Marspedia - User contributions [en]

Thaumasia quadrangle

2023-04-21T21:16:23Z

Suitupandshowup: /* Warrego Valles */

{{Mars atlas}}

{| class="wikitable sortable"
|MC-25
|Thaumasia
|30–65° S
|60–120° W
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-25-ThaumasiaRegion-mola.png
File:PIA00185-MC-25-ThaumasiaRegion-19980605.jpg
</gallery>

The Thaumasia quadrangle, is famous for showing us a good example of possible past rainfall and rivers in pictures of Warrego Valles taken with [[Mariner 9]] and the Viking Orbiters. Those early images revealed a network of branching valleys. They were clear evidence that Mars may have once been warmer, wetter, and perhaps had precipitation in the form of rain or snow. Before we saw those pictures, we believed Mars was just an old, dry desert.

The Thaumasia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS). The Thaumasia quadrangle is also referred to as MC-25 (Mars Chart-25).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>
The Thaumasia quadrangle covers the area from 30° to 65° south latitude and 60° to 120° west longitude (300-240 E). It encompasses many different regions or parts of many regions that have classical names. The northern part includes Thaumasia plateau. The southern part contains heavily cratered highland terrain and relatively smooth, low plains, such as Aonia Planum and Icaria Planum. Parts of Solis Planum, Aonia Terra, and Bosporus Planum are also found in this quadrangle. The east-central part includes Lowell Crater. Lowell Crater was named after Percival Lowell who studied Mars with a telescope in Flagstaff Arizona and then went around the world promoting the idea that Mars was inhabited<ref>http://areology.blogspot.com/2010/06/ancient-lava-plain-in-thaumasia-planum.html</ref>
The name comes from Thaumas, the god of the clouds and celestial apparitions.<ref>Blunck, J. 1982. Mars and its Satellites. Exposition Press. Smithtown, N.Y.</ref>

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

==[[Martian gullies]]==

[[File: Gulliesthaumasal.jpg|600pxr|Group of gullies, as seen by HiRISE under the HiWish program]]
Group of gullies, as seen by HiRISE under the HiWish program

Gullies occur on steep slopes, especially on the walls of craters. Gullies are believed to be relatively young because they have few, if any craters. Moreover, they lie on top of sand dunes which themselves are considered to be quite young. Usually, each gully has an alcove, channel, and apron.<ref>Edgett |first1= K. |last2= Malin |first2= M. C. |last3= Williams |first3= R. M. E. |last4= Davis |first4= S. D. |date= 2003 |title= Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit |journal= Lunar Planet. Sci. |volume=34 |at=p. 1038, Abstract 1038 | url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf |</ref>
Gullies were once thought to be caused by recent flowing water. However, with further extensive observations with HiRISE, it was found that many are forming/changing today, even though liquid water cannot exist under current Martian conditions. Faced with these new observations, scientists came up with other ideas to explain them. The consensus seems to be that although water may have helped form them in the past, today they are being produced by chunks of dry ice moving down steep slopes. <ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |date=July 10, 2014 |work=NASA</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm </ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>
There is evidence here in this quadrangle that indeed water in the past may have aided in the formation of gullies. Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow.<ref>Dickson, J. et al. 2007. Martian gullies in the southern mid-latitudes of Mars Evidence for climate-controlled formation of young fluvial features based upon local and global topography. Icarus: 188. 315-323.</ref>
Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude.<ref>Hecht, M. 2002. Metastability of liquid water on Mars. Icarus: 156. 373-386.</ref> This relationship seems to hold true in Thaumasia. This region is fairly high in evlevation and has very few gullies; however, a few are present in the lower elevations like the one pictured below in Ross Crater.

<gallery class="center" widths="380px" heights="360px">

Image:Context for Gullies in Ross crater.jpg|CTX image of part of Ross Crater showing context for next image from HiRISE.
Image:Gullies in Ross Crater.JPG|Gullies in Ross Crater

ESP 040186 1215multiplechannels.jpg|Close-up of gullies showing multiple channels

ESP 040186 1215streamlined.jpg|Close-up of gullies showing streamlined forms in channels

ESP 047333 1215gullies.jpg|Wide view of gullies in Ross Crater

Wikisliphergullies.jpg|Gullies in crater on the rim of Slipher Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter)

ESP 048546 1225gullies.jpg|Gullies
</gallery>

[[File: 47333 1215polygonsclose2.jpg|600pxr|Close view of polygons that are near gullies in Ross Crater]]
Close view of polygons that are near gullies in Ross Crater

==Sand Dunes==

Many places on Mars have sand dunes. Some craters in Thaumasia show dark blotches in them. High resolution photos expose the dark markings as dark sand dunes. Dark sand dunes probably contain the igneous rock basalt.<ref>Michael H. Carr|title=The surface of Mars|url=https://books.google.com/books?id=uLHlJ6sjohwC|accessdate=21 March 2011|year=2006|publisher=Cambridge University Press|isbn=978-0-521-87201-0</ref>

<gallery class="center" widths="380px" heights="360px">

Image:Context for Dunes in Brashear.jpg|[[Mars Global Surveyor]] context image with box showing where next image is located.
Image:Dunesinbrashear.jpg|Mars Global Surveyor image of part of area in the previous photo. The dark spots are resolved to be sand dunes. Image was taken under the MOC Public Targeting Program.

Wikilamont.jpg|Lamont Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Dark areas are composed of mostly dunes.

Wikilamontdunes.jpg|Dunes on floor of Lamont Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image.
</gallery>
[[File: ESP_028580_1385cells.jpg|600pxr|Crater floor covered with sand dunes in the shape of cells, as seen by HiRISE under HiWish program]]
Crater floor covered with sand dunes in the shape of cells, as seen by HiRISE under HiWish program

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Warrego Valles==

[[Mariner 9]] and Viking Orbiter images, showed a network of branching valleys in Thaumasia called Warrego Valles. These networks are evidence that Mars may have once been warmer, wetter, and perhaps had precipitation in the form of rain or snow. A study with the Mars Orbiter Laser Altimeter, Thermal Emission Imaging System (THEMIS) and the Mars Orbiter Camera (MOC) support the idea that Warrego Valles was formed from precipitation.<ref>Ansan, V and N. Mangold. 2006. New observations of Warrego Valles, Mars: Evidence for precipitation and surface runoff. Icarus. 54:219-242.</ref> At first glance they resemble river valleys on our Earth. But sharper images from more advanced cameras reveal that the valleys are not continuous. They are very old and may have suffered from the effects of erosion. Pictures below show some of these branching valleys.<ref>http://www.msss.com/mars_images/moc/2004/10/03/</ref>

[[File: Channels near Warrego in Thaumasia.JPG|600pxr|Channels near Warrego Valles, as seen by THEMIS. These branched channels are strong evidence for flowing water on Mars, perhaps during a much warmer period.]]

Channels near Warrego Valles, as seen by THEMIS. These branched channels are strong evidence for flowing water on Mars, perhaps during a much warmer period.

[[File:77532 1365contextchannels.jpg|600pxr|Some channals of Warrego Valles, as seen by CTX and HiRISE]]

Some channels of Warrego Valles, as seen by CTX and HiRISE

==Craters==

[[File: ESP 048282 1295flamecrater.jpg|600pxr|Unnamed crater with thin ejecta There are also many cones visible in the image.]]
Unnamed crater with thin ejecta, as seen by HiRISE under the HiWish program There are also many cones visible in the image.

Thaumasia is in the old southern highlands of Mars. As such it is loaded with craters. Craters are important to scientists.
The density of impact craters is used to determine the surface ages of Mars and other solar system bodies.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/</ref> The older the surface, the more craters present. Crater shapes can reveal the presence of ground ice.
The area around craters may be rich in minerals. On Mars, heat from the impact melts ice in the ground. Water from the melting ice dissolves minerals, and then deposits them in cracks or faults that were produced with the impact. This process, called hydrothermal alteration, is a major way in which ore deposits are produced. The area around Martian craters may be rich in useful ores for the future colonization of Mars.<ref>http://www.indiana.edu/~sierra/papers/2003/Patterson.html.</ref>
Studies on the Earth have documented that cracks are produced and that secondary minerals veins are deposited in the cracks.<ref>Osinski, G, J. Spray, and P. Lee. 2001. Impact-induced hydrothermal activity within the Haughton impact structure, arctic Canada: Generation of a transient, warm, wet oasis. Meteoritics & Planetary Science: 36. 731-745</ref> <ref>http://www.ingentaconnect.com/content/arizona/maps/2005/00000040/00000012/art00007</ref> <ref>Pirajno, F. 2000. Ore Deposits and Mantle Plumes. Kluwer Academic Publishers. Dordrecht, The Netherlands</ref> Images from satellites orbiting Mars have detected cracks near impact craters.<ref>Head, J. and J. Mustard. 2006. Breccia Dikes and Crater-Related Faults in Impact Craters on Mars: Erosion and Exposure on the Floor of a 75-km Diameter Crater at the Dichotomy Boundary. Special Issue on Role of Volatiles and Atmospheres on Martian Impact Craters Meteoritics & Planetary Science</ref> Great amounts of heat are produced during impacts. The area around a large impact may take hundreds of thousands of years to cool.<ref>name="news.discovery.com"</ref> <ref>Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2001. Effects of Large Impacts on Mars: Implications for River Formation. American Astronomical Society, DPS meeting#33, #19.08</ref><ref>Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2002. Environmental Effects of Large Impacts on Mars. Science: 298, 1977-1980.</ref>
Many craters once contained lakes.<ref>Cabrol, N. and E. Grin. 2001. The Evolution of Lacustrine Environments on Mars: Is Mars Only Hydrologically Dormant? Icarus: 149, 291-328.</ref> <ref>Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref>Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Implications of valley network lakes for the nature of Noachian hydrology.</ref> Because some crater floors show deltas, we know that water had to be present for some time. Dozens of deltas have been spotted on Mars.<ref>Wilson, J. A. Grant and A. Howard. 2013. INVENTORY OF EQUATORIAL ALLUVIAL FANS AND DELTAS ON MARS. 44th Lunar and Planetary Science Conference.</ref> Deltas form when sediment is washed in from a stream entering a quiet body of water. It takes a bit of time to form a delta, so the presence of a delta is exciting; it means water was there for a time, maybe for many years. Primitive organisms may have developed in such lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet.<ref>Newsom H., Hagerty J., Thorsos I. 2001. Location and sampling of aqueous and hydrothermal deposits in martian impact craters. Astrobiology: 1, 71-88.</ref>

<gallery class="center" widths="380px" heights="360px">

Wikilampland.jpg|Lampland Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter).

Wikilamplandlayers.jpg|Layers in wall of Lampland Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image of Lampland Crater.

ESP 043350 1430pointedcrater.jpg|Pointed crater, as seen by HiRISE under HiWish program Impacting object may have struck at a low angle.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 055652 1480craterfloor.jpg|Wide view of crater floor, as seen by HiRISE under HiWish program Some depressions on the floor have a mound in the center.

File:55652 1480concentricridges.jpg|Concentric ridges on crater floor, as seen by HiRISE under HiWish program

</gallery>

==Channels==

[[File: Branched Channels from Viking.jpg|600pxr|Branched channels in Thaumasia quadrangle, as seen by Viking Orbiter. Networks of channels like this are strong evidence for rain on Mars in the past.]]

Branched channels in Thaumasia quadrangle, as seen by Viking Orbiter. Networks of channels like this are strong evidence for rain on Mars in the past.

In the nearly half century of studying the Red Planet with orbiting satellites, much evidence has accumulating to prove that water once flowed in river valleys on Mars.<ref>Baker, V., et al. 2015. Fluvial geomorphology on Earth-like planetary surfaces: a review. Geomorphology. 245, 149–182.</ref> <ref>Carr, M. 1996. in Water on Mars. Oxford Univ. Press.</ref> Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the [[Mariner 9]] orbiter.<ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> <ref>Carr, M. 1979. Formation of Martian flood features by release of water from confined aquifers. J. Geophys. Res. 84, 2995–300.</ref> <ref>Komar, P. 1979. Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth. Icarus 37, 156–181.</ref> Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had. Water was probably recycled many times from the ocean to rainfall around Mars.<ref>http://spaceref.com/mars/how-much-water-was-needed-to-carve-valleys-on-mars.html</ref><ref>Luo, W., et al. 2017. New Martian valley network volume estimate consistent with ancient ocean and warm and wet climate. Nature Communications 8. Article number: 15766 (2017). doi:10.1038/ncomms15766</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 046291 1460channel.jpg|Channel, as seen by HiRISE under HiWish program
File:ESP 054821 1455channel.jpg|Channel In this image you can see how the channel cut through a ridge.
File:ESP 054874 1425channel.jpg|Channel Location is 36.968 S and 78.121 W.
File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.
</gallery>

==Latitude dependent mantle==

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past.<ref>Hecht | first1 = M | year = 2002 | title = Metastability of water on Mars | url = | journal = Icarus | volume = 156 | issue = 2| pages = 373–386 | doi=10.1006/icar.2001.6794 |</ref> <ref>Mustard | first1 = J. |display-authors=etal | year = 2001 | title = Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice | url = | journal = Nature | volume = 412 | issue = 6845| pages = 411–414 |</ref> <ref>Pollack | first1 = J. | last2 = Colburn | first2 = D. | last3 = Flaser | first3 = F. | last4 = Kahn | first4 = R. | last5 = Carson | first5 = C. | last6 = Pidek | first6 = D. | year = 1979 | title = Properties and effects of dust suspended in the martian atmosphere | url = | journal = J. Geophys. Res. | volume = 84 | issue = | pages = 2929–2945 | doi=10.1029/jb084ib06p02929 |</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 042123 1475mantle.jpg|Mantle layers exposed on crater rim, as seen by HiRISE under HiWish program Mantle is an ice-rich material that fell from the sky when the climate underwent major changes.

Image:Layered mantle in Icaria Planum.JPG|Layers in mantle deposit, as seen by HiRISE, under the [[HiWish program]]. Each layer probably fell from the sky each time the climate changed.
Image:ESP_024863movement.jpg|Mantle on inside of crater
</gallery>

==Dust devil tracks==

Dust devil tracks are very common on Mars, especially in certain seasons. Dust devils can create very pretty tracks. Dust devils remove bright colored dust from the Martian surface; thereby exposing a dark layer. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface creating tracks. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will be enough. The width of a single human hair ranges from approximately 20 to 200 microns (μm); consequently, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov. Retrieved on 7 August 2011.</ref> The pattern of tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref> A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 m and last at least 26 minutes.<ref>Reiss, D. et al. 2011. Multitemporal observations of identical active dust devils on Mars with High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC). Icarus. 215:358-369.</ref>

<gallery class="center" widths="380px" heights="360px">
Wikifontanadevils.jpg|Dust devil tracks just outside north rim of Fontana Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter).

</gallery>

[[File:Wikibiachini.jpg |600pxr|Biachini Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Dust devil tracks and dunes are visible on the floor. The narrow, dark lines are dust devil tracks.]]
Biachini Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Dust devil tracks and dunes are visible on the floor. The narrow, dark lines are dust devil tracks.

==Glaciers==

Since the 70’s, as our spacecraft have studied Mars with more and more advanced cameras and other instruments, we have found more and more evidence for glaciers. <ref>Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref>Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref> Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref>Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref>Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref>Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref>Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> On Mars these glaciers are covered with rock and dust debris a few meters to a few tens of meters thick. Although Mars today seems too dry for any glaciers, this covering material has protected the underlying ice. <ref>Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> One would think that under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref>Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref> Sometimes, the glaciers are active for a time and then the ice in them leaves. However, they leave behind ridges of debris that was carried within and on top of the ice. Often, the ridges make a curved shape.

<gallery class="center" widths="380px" heights="360px">

ESP 045526 1385flow.jpg|Curved ridge that probably was left by glacier, as seen by HiRISE under HiWish program

</gallery>

[[File:ESP 056642 1370flows.jpg|600pxr|Arrows indicate glaciers]]
Arrows indicate glaciers

==Other views from Thaumasia==

[[File:45737 1380brains.jpg|600pxr| Brain terrain when ice leaves the ground along cracks. It may still contain some ice. Box shows the size of football field.]]
Brain terrain when ice leaves the ground along cracks. It may still contain some ice. Box shows the size of football field.

<gallery class="center" widths="380px" heights="360px">

Image:24400dike.jpg|Possible dike in Thaumasia Dikes may have deposited valuable minerals.
Image:28384pitsandhollows.jpg|Strange surface features, as seen by HiWish under the HiWish program. The box indicates the size of a football field.

File:ESP 054954 1425ridges.jpg|Ridges We are not quite sure what causes these types of ridges.

File:56642 1370streaks.jpg|Dark slope streaks, as seen by HiRISE under[[HiWish program]] Dark slope streaks are when bright dust moves down a slope and exposes the underlying dark surface.
</gallery>

[[File:46106 1390cracks.jpg|600pxr|Cracks and pits that form square shapes Arrow points to squares formed by cracks.]]
Cracks and pits that form square shapes Arrow points to squares formed by cracks.

==See also==

*[[Glaciers on Mars]]
*[[HiWish program]]
*[[How are features on Mars Named?]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Periodic climate changes on Mars]]
*[[Rivers on Mars]]

== References ==
{{reflist|colwidth=30em}}

==Further reading==
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

==External links==

*[https://www.uahirise.org/PSP_005383_1255 Changes in dust devil tracks]

[[Category: Mars Atlas]]

Thaumasia quadrangle

2023-04-21T21:15:15Z

Suitupandshowup: /* Warrego Valles */ added image

{{Mars atlas}}

{| class="wikitable sortable"
|MC-25
|Thaumasia
|30–65° S
|60–120° W
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-25-ThaumasiaRegion-mola.png
File:PIA00185-MC-25-ThaumasiaRegion-19980605.jpg
</gallery>

The Thaumasia quadrangle, is famous for showing us a good example of possible past rainfall and rivers in pictures of Warrego Valles taken with [[Mariner 9]] and the Viking Orbiters. Those early images revealed a network of branching valleys. They were clear evidence that Mars may have once been warmer, wetter, and perhaps had precipitation in the form of rain or snow. Before we saw those pictures, we believed Mars was just an old, dry desert.

The Thaumasia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS). The Thaumasia quadrangle is also referred to as MC-25 (Mars Chart-25).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>
The Thaumasia quadrangle covers the area from 30° to 65° south latitude and 60° to 120° west longitude (300-240 E). It encompasses many different regions or parts of many regions that have classical names. The northern part includes Thaumasia plateau. The southern part contains heavily cratered highland terrain and relatively smooth, low plains, such as Aonia Planum and Icaria Planum. Parts of Solis Planum, Aonia Terra, and Bosporus Planum are also found in this quadrangle. The east-central part includes Lowell Crater. Lowell Crater was named after Percival Lowell who studied Mars with a telescope in Flagstaff Arizona and then went around the world promoting the idea that Mars was inhabited<ref>http://areology.blogspot.com/2010/06/ancient-lava-plain-in-thaumasia-planum.html</ref>
The name comes from Thaumas, the god of the clouds and celestial apparitions.<ref>Blunck, J. 1982. Mars and its Satellites. Exposition Press. Smithtown, N.Y.</ref>

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

==[[Martian gullies]]==

[[File: Gulliesthaumasal.jpg|600pxr|Group of gullies, as seen by HiRISE under the HiWish program]]
Group of gullies, as seen by HiRISE under the HiWish program

Gullies occur on steep slopes, especially on the walls of craters. Gullies are believed to be relatively young because they have few, if any craters. Moreover, they lie on top of sand dunes which themselves are considered to be quite young. Usually, each gully has an alcove, channel, and apron.<ref>Edgett |first1= K. |last2= Malin |first2= M. C. |last3= Williams |first3= R. M. E. |last4= Davis |first4= S. D. |date= 2003 |title= Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit |journal= Lunar Planet. Sci. |volume=34 |at=p. 1038, Abstract 1038 | url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf |</ref>
Gullies were once thought to be caused by recent flowing water. However, with further extensive observations with HiRISE, it was found that many are forming/changing today, even though liquid water cannot exist under current Martian conditions. Faced with these new observations, scientists came up with other ideas to explain them. The consensus seems to be that although water may have helped form them in the past, today they are being produced by chunks of dry ice moving down steep slopes. <ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |date=July 10, 2014 |work=NASA</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm </ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>
There is evidence here in this quadrangle that indeed water in the past may have aided in the formation of gullies. Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow.<ref>Dickson, J. et al. 2007. Martian gullies in the southern mid-latitudes of Mars Evidence for climate-controlled formation of young fluvial features based upon local and global topography. Icarus: 188. 315-323.</ref>
Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude.<ref>Hecht, M. 2002. Metastability of liquid water on Mars. Icarus: 156. 373-386.</ref> This relationship seems to hold true in Thaumasia. This region is fairly high in evlevation and has very few gullies; however, a few are present in the lower elevations like the one pictured below in Ross Crater.

<gallery class="center" widths="380px" heights="360px">

Image:Context for Gullies in Ross crater.jpg|CTX image of part of Ross Crater showing context for next image from HiRISE.
Image:Gullies in Ross Crater.JPG|Gullies in Ross Crater

ESP 040186 1215multiplechannels.jpg|Close-up of gullies showing multiple channels

ESP 040186 1215streamlined.jpg|Close-up of gullies showing streamlined forms in channels

ESP 047333 1215gullies.jpg|Wide view of gullies in Ross Crater

Wikisliphergullies.jpg|Gullies in crater on the rim of Slipher Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter)

ESP 048546 1225gullies.jpg|Gullies
</gallery>

[[File: 47333 1215polygonsclose2.jpg|600pxr|Close view of polygons that are near gullies in Ross Crater]]
Close view of polygons that are near gullies in Ross Crater

==Sand Dunes==

Many places on Mars have sand dunes. Some craters in Thaumasia show dark blotches in them. High resolution photos expose the dark markings as dark sand dunes. Dark sand dunes probably contain the igneous rock basalt.<ref>Michael H. Carr|title=The surface of Mars|url=https://books.google.com/books?id=uLHlJ6sjohwC|accessdate=21 March 2011|year=2006|publisher=Cambridge University Press|isbn=978-0-521-87201-0</ref>

<gallery class="center" widths="380px" heights="360px">

Image:Context for Dunes in Brashear.jpg|[[Mars Global Surveyor]] context image with box showing where next image is located.
Image:Dunesinbrashear.jpg|Mars Global Surveyor image of part of area in the previous photo. The dark spots are resolved to be sand dunes. Image was taken under the MOC Public Targeting Program.

Wikilamont.jpg|Lamont Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Dark areas are composed of mostly dunes.

Wikilamontdunes.jpg|Dunes on floor of Lamont Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image.
</gallery>
[[File: ESP_028580_1385cells.jpg|600pxr|Crater floor covered with sand dunes in the shape of cells, as seen by HiRISE under HiWish program]]
Crater floor covered with sand dunes in the shape of cells, as seen by HiRISE under HiWish program

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Warrego Valles==

[[Mariner 9]] and Viking Orbiter images, showed a network of branching valleys in Thaumasia called Warrego Valles. These networks are evidence that Mars may have once been warmer, wetter, and perhaps had precipitation in the form of rain or snow. A study with the Mars Orbiter Laser Altimeter, Thermal Emission Imaging System (THEMIS) and the Mars Orbiter Camera (MOC) support the idea that Warrego Valles was formed from precipitation.<ref>Ansan, V and N. Mangold. 2006. New observations of Warrego Valles, Mars: Evidence for precipitation and surface runoff. Icarus. 54:219-242.</ref> At first glance they resemble river valleys on our Earth. But sharper images from more advanced cameras reveal that the valleys are not continuous. They are very old and may have suffered from the effects of erosion. A picture below shows some of these branching valleys.<ref>http://www.msss.com/mars_images/moc/2004/10/03/</ref>

[[File: Channels near Warrego in Thaumasia.JPG|600pxr|Channels near Warrego Valles, as seen by THEMIS. These branched channels are strong evidence for flowing water on Mars, perhaps during a much warmer period.]]

Channels near Warrego Valles, as seen by THEMIS. These branched channels are strong evidence for flowing water on Mars, perhaps during a much warmer period.

File:77532 1365contextchannels.jpg
[[File:77532 1365contextchannels.jpg|600pxr|Some channals of Warrego Valles, as seen by CTX and HiRISE]]

Some channels of Warrego Valles, as seen by CTX and HiRISE

==Craters==

[[File: ESP 048282 1295flamecrater.jpg|600pxr|Unnamed crater with thin ejecta There are also many cones visible in the image.]]
Unnamed crater with thin ejecta, as seen by HiRISE under the HiWish program There are also many cones visible in the image.

Thaumasia is in the old southern highlands of Mars. As such it is loaded with craters. Craters are important to scientists.
The density of impact craters is used to determine the surface ages of Mars and other solar system bodies.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/</ref> The older the surface, the more craters present. Crater shapes can reveal the presence of ground ice.
The area around craters may be rich in minerals. On Mars, heat from the impact melts ice in the ground. Water from the melting ice dissolves minerals, and then deposits them in cracks or faults that were produced with the impact. This process, called hydrothermal alteration, is a major way in which ore deposits are produced. The area around Martian craters may be rich in useful ores for the future colonization of Mars.<ref>http://www.indiana.edu/~sierra/papers/2003/Patterson.html.</ref>
Studies on the Earth have documented that cracks are produced and that secondary minerals veins are deposited in the cracks.<ref>Osinski, G, J. Spray, and P. Lee. 2001. Impact-induced hydrothermal activity within the Haughton impact structure, arctic Canada: Generation of a transient, warm, wet oasis. Meteoritics & Planetary Science: 36. 731-745</ref> <ref>http://www.ingentaconnect.com/content/arizona/maps/2005/00000040/00000012/art00007</ref> <ref>Pirajno, F. 2000. Ore Deposits and Mantle Plumes. Kluwer Academic Publishers. Dordrecht, The Netherlands</ref> Images from satellites orbiting Mars have detected cracks near impact craters.<ref>Head, J. and J. Mustard. 2006. Breccia Dikes and Crater-Related Faults in Impact Craters on Mars: Erosion and Exposure on the Floor of a 75-km Diameter Crater at the Dichotomy Boundary. Special Issue on Role of Volatiles and Atmospheres on Martian Impact Craters Meteoritics & Planetary Science</ref> Great amounts of heat are produced during impacts. The area around a large impact may take hundreds of thousands of years to cool.<ref>name="news.discovery.com"</ref> <ref>Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2001. Effects of Large Impacts on Mars: Implications for River Formation. American Astronomical Society, DPS meeting#33, #19.08</ref><ref>Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2002. Environmental Effects of Large Impacts on Mars. Science: 298, 1977-1980.</ref>
Many craters once contained lakes.<ref>Cabrol, N. and E. Grin. 2001. The Evolution of Lacustrine Environments on Mars: Is Mars Only Hydrologically Dormant? Icarus: 149, 291-328.</ref> <ref>Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref>Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Implications of valley network lakes for the nature of Noachian hydrology.</ref> Because some crater floors show deltas, we know that water had to be present for some time. Dozens of deltas have been spotted on Mars.<ref>Wilson, J. A. Grant and A. Howard. 2013. INVENTORY OF EQUATORIAL ALLUVIAL FANS AND DELTAS ON MARS. 44th Lunar and Planetary Science Conference.</ref> Deltas form when sediment is washed in from a stream entering a quiet body of water. It takes a bit of time to form a delta, so the presence of a delta is exciting; it means water was there for a time, maybe for many years. Primitive organisms may have developed in such lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet.<ref>Newsom H., Hagerty J., Thorsos I. 2001. Location and sampling of aqueous and hydrothermal deposits in martian impact craters. Astrobiology: 1, 71-88.</ref>

<gallery class="center" widths="380px" heights="360px">

Wikilampland.jpg|Lampland Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter).

Wikilamplandlayers.jpg|Layers in wall of Lampland Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image of Lampland Crater.

ESP 043350 1430pointedcrater.jpg|Pointed crater, as seen by HiRISE under HiWish program Impacting object may have struck at a low angle.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 055652 1480craterfloor.jpg|Wide view of crater floor, as seen by HiRISE under HiWish program Some depressions on the floor have a mound in the center.

File:55652 1480concentricridges.jpg|Concentric ridges on crater floor, as seen by HiRISE under HiWish program

</gallery>

==Channels==

[[File: Branched Channels from Viking.jpg|600pxr|Branched channels in Thaumasia quadrangle, as seen by Viking Orbiter. Networks of channels like this are strong evidence for rain on Mars in the past.]]

Branched channels in Thaumasia quadrangle, as seen by Viking Orbiter. Networks of channels like this are strong evidence for rain on Mars in the past.

In the nearly half century of studying the Red Planet with orbiting satellites, much evidence has accumulating to prove that water once flowed in river valleys on Mars.<ref>Baker, V., et al. 2015. Fluvial geomorphology on Earth-like planetary surfaces: a review. Geomorphology. 245, 149–182.</ref> <ref>Carr, M. 1996. in Water on Mars. Oxford Univ. Press.</ref> Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the [[Mariner 9]] orbiter.<ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> <ref>Carr, M. 1979. Formation of Martian flood features by release of water from confined aquifers. J. Geophys. Res. 84, 2995–300.</ref> <ref>Komar, P. 1979. Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth. Icarus 37, 156–181.</ref> Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had. Water was probably recycled many times from the ocean to rainfall around Mars.<ref>http://spaceref.com/mars/how-much-water-was-needed-to-carve-valleys-on-mars.html</ref><ref>Luo, W., et al. 2017. New Martian valley network volume estimate consistent with ancient ocean and warm and wet climate. Nature Communications 8. Article number: 15766 (2017). doi:10.1038/ncomms15766</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 046291 1460channel.jpg|Channel, as seen by HiRISE under HiWish program
File:ESP 054821 1455channel.jpg|Channel In this image you can see how the channel cut through a ridge.
File:ESP 054874 1425channel.jpg|Channel Location is 36.968 S and 78.121 W.
File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.
</gallery>

==Latitude dependent mantle==

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past.<ref>Hecht | first1 = M | year = 2002 | title = Metastability of water on Mars | url = | journal = Icarus | volume = 156 | issue = 2| pages = 373–386 | doi=10.1006/icar.2001.6794 |</ref> <ref>Mustard | first1 = J. |display-authors=etal | year = 2001 | title = Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice | url = | journal = Nature | volume = 412 | issue = 6845| pages = 411–414 |</ref> <ref>Pollack | first1 = J. | last2 = Colburn | first2 = D. | last3 = Flaser | first3 = F. | last4 = Kahn | first4 = R. | last5 = Carson | first5 = C. | last6 = Pidek | first6 = D. | year = 1979 | title = Properties and effects of dust suspended in the martian atmosphere | url = | journal = J. Geophys. Res. | volume = 84 | issue = | pages = 2929–2945 | doi=10.1029/jb084ib06p02929 |</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 042123 1475mantle.jpg|Mantle layers exposed on crater rim, as seen by HiRISE under HiWish program Mantle is an ice-rich material that fell from the sky when the climate underwent major changes.

Image:Layered mantle in Icaria Planum.JPG|Layers in mantle deposit, as seen by HiRISE, under the [[HiWish program]]. Each layer probably fell from the sky each time the climate changed.
Image:ESP_024863movement.jpg|Mantle on inside of crater
</gallery>

==Dust devil tracks==

Dust devil tracks are very common on Mars, especially in certain seasons. Dust devils can create very pretty tracks. Dust devils remove bright colored dust from the Martian surface; thereby exposing a dark layer. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface creating tracks. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will be enough. The width of a single human hair ranges from approximately 20 to 200 microns (μm); consequently, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov. Retrieved on 7 August 2011.</ref> The pattern of tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref> A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 m and last at least 26 minutes.<ref>Reiss, D. et al. 2011. Multitemporal observations of identical active dust devils on Mars with High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC). Icarus. 215:358-369.</ref>

<gallery class="center" widths="380px" heights="360px">
Wikifontanadevils.jpg|Dust devil tracks just outside north rim of Fontana Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter).

</gallery>

[[File:Wikibiachini.jpg |600pxr|Biachini Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Dust devil tracks and dunes are visible on the floor. The narrow, dark lines are dust devil tracks.]]
Biachini Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Dust devil tracks and dunes are visible on the floor. The narrow, dark lines are dust devil tracks.

==Glaciers==

Since the 70’s, as our spacecraft have studied Mars with more and more advanced cameras and other instruments, we have found more and more evidence for glaciers. <ref>Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref>Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref> Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref>Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref>Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref>Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref>Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> On Mars these glaciers are covered with rock and dust debris a few meters to a few tens of meters thick. Although Mars today seems too dry for any glaciers, this covering material has protected the underlying ice. <ref>Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> One would think that under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref>Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref> Sometimes, the glaciers are active for a time and then the ice in them leaves. However, they leave behind ridges of debris that was carried within and on top of the ice. Often, the ridges make a curved shape.

<gallery class="center" widths="380px" heights="360px">

ESP 045526 1385flow.jpg|Curved ridge that probably was left by glacier, as seen by HiRISE under HiWish program

</gallery>

[[File:ESP 056642 1370flows.jpg|600pxr|Arrows indicate glaciers]]
Arrows indicate glaciers

==Other views from Thaumasia==

[[File:45737 1380brains.jpg|600pxr| Brain terrain when ice leaves the ground along cracks. It may still contain some ice. Box shows the size of football field.]]
Brain terrain when ice leaves the ground along cracks. It may still contain some ice. Box shows the size of football field.

<gallery class="center" widths="380px" heights="360px">

Image:24400dike.jpg|Possible dike in Thaumasia Dikes may have deposited valuable minerals.
Image:28384pitsandhollows.jpg|Strange surface features, as seen by HiWish under the HiWish program. The box indicates the size of a football field.

File:ESP 054954 1425ridges.jpg|Ridges We are not quite sure what causes these types of ridges.

File:56642 1370streaks.jpg|Dark slope streaks, as seen by HiRISE under[[HiWish program]] Dark slope streaks are when bright dust moves down a slope and exposes the underlying dark surface.
</gallery>

[[File:46106 1390cracks.jpg|600pxr|Cracks and pits that form square shapes Arrow points to squares formed by cracks.]]
Cracks and pits that form square shapes Arrow points to squares formed by cracks.

==See also==

*[[Glaciers on Mars]]
*[[HiWish program]]
*[[How are features on Mars Named?]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Periodic climate changes on Mars]]
*[[Rivers on Mars]]

== References ==
{{reflist|colwidth=30em}}

==Further reading==
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

==External links==

*[https://www.uahirise.org/PSP_005383_1255 Changes in dust devil tracks]

[[Category: Mars Atlas]]

File:77532 1365contextchannels.jpg

2023-04-21T21:11:35Z

Suitupandshowup: Part of the Warrego Vallis stream system, as seen by CTX and HiRISE under the HiWish program Source: https://www.uahirise.org/ESP_077532_1365 for HiRISE and http://viewer.mars.asu.edu/planetview/inst/ctx/K09_056721_1384_XI_41S093W#P=K09_056721_1384_XI_41S093W&T=2 for CTX Credits: NASA/JPL/University of Arizona/Secosky and NASA/MSSS/Secosky

== Summary ==
Part of the Warrego Vallis stream system, as seen by CTX and HiRISE under the HiWish program

Source: https://www.uahirise.org/ESP_077532_1365 for HiRISE and http://viewer.mars.asu.edu/planetview/inst/ctx/K09_056721_1384_XI_41S093W#P=K09_056721_1384_XI_41S093W&T=2 for CTX

Credits: NASA/JPL/University of Arizona/Secosky and NASA/MSSS/Secosky
== Licensing ==
{{PD}}

Geological processes that have shaped Mars: Why Mars looks like it does

2023-04-17T22:21:56Z

Suitupandshowup: /* Liquid water */ added image

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:Mars, Earth size comparison.jpg|left|thumb|px|Earth and Mars Earth is much bigger, but both have the same land area. Mars has about one third the gravity of the Earth.]]

Mars looks like it does because of certain geological processes. Some of them are common to both the Earth and Mars. However, others are rare or nonexistent on the Earth. Mars shows an extremely old record of the past that is lacking on the Earth. Plate tectonics and vigorous air and water erosion has wiped out nearly all of the past geology of the Earth. In contrast, much of the Martian surface is billions of years old. Another factor that has affected the appearance of Mars is its extreme cold. The coldness of the planet makes carbon dioxide significant. It has influenced Mars both as a gas and as a solid. As a greenhouse gas, early in the history of the planet, it may have been thick enough in the atmosphere to help raise the temperature enough to permit water to flow, to carve rivers, to form lakes and an ocean. Indeed, it may have been warm enough from carbon dioxide for life to first originate on Mars and then travel to the Earth on meteorites. Today, as a solid, carbon dioxide (dry ice) produces the ubiquitous gullies found in numerous areas of the planet.

==Erosion Related==

As on the Earth material was laid down and then later eroded. Many spectacular scenes are present with places that were mostly eroded, but with remnants remaining in the form of buttes and mesas. Sometimes, sediments were put down in layers. As a result beautiful places were created. On the Earth we admire such layers in Monument Valley and many beautiful canyons. The same types of landscapes show up on Mars.
The top layer of buttes and mesas is hard and resistant to erosion. It protects the lower layers from being eroded away. On Mars that hard, cap rock could be made from a lava flow. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area.

<gallery class="center" widths="380px" heights="360px">

File:16 21 2117 monument valley.jpg|Spearhead Mesa in Monument Valley Note the flat top and steep walls that are characteristic of mesas.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it.

File:58563 2225mesa.jpg|Mesa

File:45016 2080mesas.jpg|Mesas, as seen by HiRISE under HiWish program These are like the ones in Monument Valley

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte: Buttes have a much smaller area than mesas, but both have a hard cap rock on the top. Box shows the size of a football field.

</gallery>

As on the Earth, there are landslides. However, they could be a little different since Mars has only about a third of Earth’s gravity.

<gallery class="center" widths="380px" heights="360px">

File:ESP 043963 1550landslide.jpg|Landslide

</gallery>

Common features in certain areas of the Earth’s surface are “Yardangs.” They are found in desert areas which contain much sand. The wind blows sand and shapes the relatively soft grained deposits into the long, boat shapes of yardangs. On Mars it is thought that these forms are the result of the weathering of huge ash deposits from volcanoes. Mars has the biggest known volcanoes in the solar system. Many probably threw out much fine-grained material which was easily eroded to make vast fields of yardangs. Regions called the “Medusa Fossae Formation and Electris deposits contain thousands of yardangs.

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs.jpg|Yardangs
</gallery>

Unlike the Earth, Mars shows landscapes that are billions of years old. In that time material has been deposited and then eroded and/or greatly changed. Some features have been “inverted.” Low areas turned into high areas. Low areas like stream beds were filled with erosion-resistant materials like lava and large rocks. Later, the surrounding, softer ground became eroded. As a result, the old stream bed now appears raised. We can tell it was originally a stream bed since the overall shape from above still looks like a stream with curves and branches.

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Inverted streams Here a branched stream became filled with hard material and then the surrounding ground was eroded.]]

Another structure made with erosion is a “pedestal crater.” They are abundant in regions far from the equator. These craters seem to sit on little circular shelves or pedestals.<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> In the impacting process, ejecta fell about the crater and protected the underlying ground from erosion. These craters occur where we think there was a great deal of ice in the ground. So, much of the material that disappeared was just ice. With that being said, pedestal craters give us an indication of how much ice was in the region. In some places hundreds of meters of ice-rich ground were removed to make pedestal craters.<ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

[[File:ESP 037528 2350pedestal.jpg |thumb|left|px||Pedestal crater Surface close to crater was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

[[Image:Pedestal crater3.jpg |thumb|right|px||Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings]]

[[File:Pedestaldrawingcolor2.jpg|thumb|600px|center|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

Some structures on Mars are being “exhumed.” Craters are observed that are being uncovered. In the past, impacts produced craters. Later, they were buried. Now they are in the process of being uncovered by erosion. When an asteroid strikes the surface it generates a hole and throws out ejecta all around it. A circular hole is the result. If we see a half of a crater, we know that that it is being exposed by erosion. Impacts do not produce half holes!

<gallery class="center" widths="380px" heights="360px">

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]
</gallery>

==Craters==

Impact craters occur on both the Earth and Mars. However, due to the extreme age of the Martian surface, most of Mars shows a high density of impact craters especially in the southern hemisphere. Craters do not last long on the Earth. Remember, the Earth experiences a great deal more erosion due to its thick atmosphere and abundant water. And, at intervals, the crust is taken into the Earth at plate boundaries. We know a fair amount about impact craters because the Earth has impact craters like Meteor Crater in Arizona that we can study easily.

<gallery class="center" widths="380px" heights="360px">

File:Barringer Crater USGS.jpg|Meteor Crater in Arizona
</gallery>

We know that a new crater will have a rim and ejecta around it. Large ones may have a central uplift and maybe a ring around the middle of the floor. We know that the impact brings up material from deep underground.<ref>https://www.uahirise.org/hipod/PSP_007464_1985</ref> If we study the rocks in the central mound and in the ejecta, we can learn about what is deep underground. During an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE Colors show different minerals--some used to be deep underground.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterejectarim.jpg|Young crater showing layers, rim, and ejecta. Ejecta was thrown out by the force of impact.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.
</gallery>

The heat from an impact into ice-rich ground may produce channels emanating from the edge of the ejecta. These have been seen around a number of craters.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

</gallery>

Mars shows some interesting variations to the usual appearance of craters. At times the force of an impact reaches down to a different type of layer. The lower layer may be of a different color; therefore the ejecta that is spread on the landscape may be a different color.

<gallery class="center" widths="380px" heights="360px">
File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta Impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:29565 2075newcratercomposite.jpg|New, small crater Meteorite that hit here throw up dark material that was under a layer of bright, surface dust. We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref>

File:ESP 011425 1775newcrater.jpg|Dark ejecta of a new crater covers the bright surroundings.
</gallery>

Sometimes it looks as if an impact caused rocks to melt and when the molted rocks landed on the crater floor steam explosions occurred with ice-rich ground. What results is ground with a high density of pits.

<gallery class="center" widths="380px" heights="360px">
File:ESP 012531 1435pits.jpg|Floor of Hale Crater showing pits from steam explosions when hot, melt from an impact landed.

</gallery>

On occasion, an impact may go down to ice-rich ground or maybe to a layer of ice. Indeed, a number of craters expose ice on their floors which after a period of time disappears into the thin Martian atmosphere.

<gallery class="center" widths="380px" heights="360px">

File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
</gallery>

Then there is a type of crater which is common in locations we think contain much ice. Called “ring-mold” craters, they may be caused by a rebound of an ice layer. Experiments in labs confirm that this behavior can occur. Ring-mold craters are called that because they resemble ring-molds used in baking.

<gallery class="center" widths="380px" heights="360px">

File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.

26055ringmoldcrater.jpg|Close view of ring mold crater.
</gallery>

[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Now, during the impact process much material is sent flying in the air. Some of it will come down and create new craters. These are called secondary craters. They can be identified by all being of the same age. In addition, sometimes molted rock is produced by the impact. If molten rock lands on ice-rich ground, an area with a high density of pits will form. The hot molten rocks cause ice in the ground to burst into steam and cause pits to form.

<gallery class="center" widths="380px" heights="360px">

File:ESP 030244 2040secondarycraters.jpg|Secondary craters These are formed from material that is blasted way up in the air from the impact. Evidence that they are secondary craters is that they are all of the same age.
</gallery>

==Glaciers==

Mars may have had much water in past ages. Much of that water is now frozen in the ground and locked up in glacier-like forms. Many features have been found that are like glaciers—in that they are mostly made of ice and flow like glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> That means they move slowly and in a downhill direction. For ice to exist under today’s climate conditions, it must be covered with a layer of debris—dust, rocks, etc. A layer several meters or a few tens of meters thick will preserve ice for millions of years. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> Under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>
Martian glaciers show evidence of movement on their surfaces and in their shapes. The actual existence of water ice in some of them has been proven with radar studies from orbit. <ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> Some of them look just like alpine glaciers on the Earth. Most show piles of debris called moraine. This was material that was removed from one place and moved along to another by ice. Also, shapes looking just like eskers of terrestrial glaciers are common in places. Eskers form from streams moving under glaciers. These streams deposit rocks in tunnels in the ice at the bottom of glaciers. When the ice goes away, curved ridges stay behind.

<gallery class="center" widths="380px" heights="360px">

File:R0502109dorsaargentea.jpg|Possible eskers indicated by arrows. Eskers form under glaciers.

Wikilau.jpg|Lau Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Curved ridges are probably eskers which formed under glaciers.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.

File: Wikielephantglacier.jpg|Glacier in Greenland Glacier spreads out when it leaves valley.
</gallery>

For Mars, a number of names have been applied to these glacier-like forms. Some of them are tongue-shaped glaciers, lobate debris aprons (LDA’s), lineated valley fill (LVF), and concentric crater fill (CCF).<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 035327 2255tongues.jpg|Tongue-shaped glaciers These were made when a flow encountered an obstacle that made it split into two.
File:ESP 036619 2275ldalabeled.jpg|Lobate debris apron LDA) around a mound <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust . <ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref>

File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are now almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed. <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>
</gallery>

[[File:ESP 052138 1435lvf.jpg|thumb|600px|center|Lineated valley fill, as seen by HiRISE under [[HiWish program]]]]

==Ice in the ground==

Mars has some unique landscapes and features that are common just to it. Since so much water is frozen in the ground and since the thin atmosphere of Mars allows ground ice to disappear when it became exposed, unreal scenes can develop. Under current conditions on Mars, ice sublimates when exposed to the air. In that process, ice goes directly to a gas instead of first melting. It often starts with small, narrow cracks that get larger and larger. Once ice leaves the ground there is not much left except dust. And winds will eventually carry the dust away. The end result is various shaped holes, pits, canyons, and hollows. Some of these forms are called brain terrain, ribbed terrain, hollows, scalloped terrain, and exposed ice sheets. <ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> All of these may be of use to future colonists who need to find supplies of water.

[[File:45917 2220brainsopenclosed.jpg|Open an closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>]]

Open and closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows.

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> <ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref>
PIA22078 hireswideview.jpg|Wide view of triangular depression The colored strip shows the part of the image that can be seen in color. The wall at the top of the depression contains pure ice. This wall faces the south pole. <ref>Supplementary Materials Exposed subsurface ice sheets in the Martian mid-latitudes Colin M. Dundas, Ali M. Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, Nathaniel E. Putzig, Donna Viola, Sarah Sutton, Erin Clark, John W. Holt</ref>

PIA22077 hirescloseblue.jpg|Close, color view of wall containing ice from previous image <ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> <ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref>
</gallery>

[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of hollowed terrain caused by ice leaving the ground Box shows size of football field.]]

Close view of terrain caused by ice leaving the ground Box shows size of football field.

Other signs of water ice in the ground are: lobed (rampart craters), patterned ground, and possible pingos. Pattered ground or polygonal ground is common in ice-rich areas on Earth.

<gallery class="center" widths="380px" heights="360px">

File:56942 1075icepolygonslabeled2.jpg|Polygons Ice is in the low troughs that lie between the polygons.<ref>https://www.uahirise.org/ESP_047247_1150</ref>

</gallery>

Pingos are mounds that contain a core of ice.<ref>http://www.uahirise.org/ESP_046359_1250</ref> <ref>Soare, E., et al. 2019.</ref> <ref> Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref> They often have cracks on their surfaces. Cracks form when water freezes and expands. Pingos would be useful as sources of water for future colonies on the planet.

<gallery class="center" widths="380px" heights="360px">
51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.
ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program
</gallery>

Craters with ejecta that look like they were made by an impact into mud are called lobed or rampart craters. They were discovered by early, orbital missions to Mars. They are most common where we expect ice in the ground.

<gallery class="center" widths="380px" heights="360px">
File:Mars rampart crater.jpg|Yuty Crater showing lobe and rampart morphology; it looks like mud was formed during the impact.

</gallery>

Channels are sometimes found in a crater's ejecta or along the edges of the ejecta. Heat from the ejecta probably melted ice in the ground. Much heat is produced with an impact.

<gallery class="center" widths="380px" heights="360px">
File:ESP 055530 2180channels.jpg

</gallery>

==Liquid water==

Mars used to have lots of water and maybe a much thicker atmosphere billions of years ago. With liquid water, life is possible. Indeed, life may have first appeared on Mars before it occurred on Earth. Martian organisms could have been knocked off Mars by low angle asteroid impacts and found their way to Earth. Perhaps, the DNA of all Earthly organisms, included us, still contains genes from early Martian life. When we have samples of Mars brought back to Earth, we may find traces of DNA that are like ours.
Data are still being gathered and ideas debated, but scientists think that once Mars cooled down and lost its magnetic field, the solar wind may have carried away much of its atmosphere. In addition, some researchers have suggested that some of the atmosphere was splashed out by impacts. After the planet cooled, water became frozen in the polar ice caps and in the ground. But, for some period there was liquid water.

[[File:Mars vs Earth Solar Wind-1024x576.png|Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field]]

Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field

[[File:Mavenargoninfographic2.jpg|This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.]]

This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.

Huge amounts of water had to be present to carve the many outflow channels and produce the valley networks. Many of the outflow channels begin in "Chaos Terrain." Such a landscape often is where the ground seems to have just collapsed into giant blocks.<ref>https://marsed.asu.edu/mep/ice/chaos-terrain</ref> <ref>https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-9213-9_46-2</ref> It is believed that a shell of ice was created when the planet's climate cooled. Perhaps, at times the shell was broken by asteroid impacts, movements of magma, or faults. Such events would allow pressurized water to rapidly escape from under the shell of ice (shell has been called a cryosphere). Evidence is accumulating for the existence of an ocean. Lakes existed in low spots, especially craters.

[[File:ESP 056689 2210channelslowspotcropped.jpg |thumb|right|px||Channels that empty into a low area that could have been a lake Arrows show channels that lead to a low area that could have hosted a lake.]]

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel

These forms were shaped by running water.

<gallery class="center" widths="380px" heights="360px">

File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.

File:Ravi Vallis.jpg|Ravi Vallis was formed when the ground released a great flood of water from Aromatum Chaos. Maybe it started when hot magma moved under the ground.

File:Ister Chaos.jpg|Ister Chaos Water may have come out of this landscape when the ground broke up into blocks.<ref>https://www.uahirise.org/hipod/PSP_008311_1835</ref>

File:Branched Channels from Viking.jpg|These valley networks look like they were made from precipitation.
</gallery>

At present, it is hotly debated just how long water stayed around. The sun was not as strong billions of years ago. Greenhouse gases like carbon dioxide, methane, and hydrogen may have made Mars warm enough for liquid water. Massive volcanoes would have given up many of these gases, along with water vapor.

[[File: Olympus Mons Side View.svg.png|thumb|left|300px|Height of Olympus Mons compared to tall mountains on Earth]]

[[File:ESP 077583 2255inverted.jpg|thumb|500px|center|Inverted stream, a stream bed has been filled with hard materials that did not erode away like the surroundings]]

Maybe the water just existed for short periods. Some studies have showed that large impacts into icy ground could release water and change the local climate for thousands of years. Also, impacts may have punctured an ice shell and allowed pressurized water to flow out for a time. Any water moving on the surface would quickly freeze at the top. But, it would continue to flow under the ice for a long time and make many of the channels we see today. Heat to allow water to flow may have been from underground flows of magma. On the other hand, many of the features created by liquid water could have formed under massive ice sheets where water was insulated from the Martian atmosphere.
 

==Layers==

Many locations display layered formations. Some are mostly just made of ice and dust. These types of layers are common in the polar ice caps, especially the northern ice cap.<ref>https://www.uahirise.org/hipod/PSP_008244_2645</ref> Other, rockier layers, are visible in the walls of impact craters and canyon walls.

<gallery class="center" widths="380px" heights="360px">

File:PSP 008244 2645northicecaplabeled.jpg|Layers in northern ice cap that are exposed along a cliff

File:ESP 054515 2595icecaplayers.jpg|Close view of many layers exposed in northern ice cap
File: 57080 1380layerscratercolor.jpg|Layers in crater wall in Phaethontis quadrangle, as seen by HiRISE under HiWish program
48980 1725layersclose2.jpg|Close view of layers in Louros Valles
</gallery>

And then there are layers that may be more recent, they may be connected to repeated climate changes. Some have regularity to them. The climate of Mars changes drastically due to changes in the tilt of its rotational axis. At times, like now, it is close to the Earth’s 23.5 degrees. But, at times it may be as much as 70 degrees.<ref> Schorghofer, Norbert (2008). "Temperature response of Mars to Milankovitch cycles". Geophysical Research Letters. 35 (18): doi:10.1029/2008GL034954.</ref> <ref>ouma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref>Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Tilt governs the seasons and where ice is distributed. Currently, the largest deposit of ice is at the poles. At other times could have been at mid-latitudes. Imagine how it would be to have Pittsburgh under an ice cap. Mars may have had ice caps at the latitude of Pittsburgh.

<gallery class="center" widths="380px" heights="360px">

File:Mars Ice Age PIA04933 modest.jpg|How Mars may have looked with a greater tilt of Mars' rotational axis caused increased solar heating at the poles. This larger tilt would make a surface deposit of ice and dust down to about 30 degrees latitude in both hemispheres.
</gallery>

There is an ice-rich material that falls from the sky. It is called latitude dependent mantle.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It is thought to come from snow and ice-coated dust. At times, there is a lot of dust in the air. When that happens, moisture will freeze onto dust grains. When the ice-coated dust particle gets heavy enough, it will fall. Recent accumulations of this mantle look smooth. In some places the mantle is layered. Some formations, particularly in protected spots in craters and against mounds, suggest that these layered formations had many more layers. The wind sometimes shapes them into layered mounds.

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.
[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210dipping.jpg|Layers leaning against a mound The mound protected them from erosion.
</gallery>

The older layers visible on crater and canyon walls may have different sources. Some are from lava flows or ash from volcanoes. Some may have formed under water like most layered sedimentary rocks on the Earth.<ref>https://www.uahirise.org/PSP_008391_1790</ref> Curiosity, our robotic explorer, has found that layers in Gale Crater were made from sediments at the bottom of a lake. Some may be just from dust and debris settling in low areas and then being cemented by rising groundwater carrying minerals like sulfates and silica.<ref> Rates and mechanisms of chemical weathering of ferromagnesian silicate minerals on Mars | date = 1993 | last1 = Burns | first1 = Roger G | journal = Geochimica et Cosmochimica Acta | volume = 57 | issue = 19 | pages = 4555–4574 |</ref> <ref>{{cite journal | doi = 10.1029/92JE02055 | title = Rates of Oxidative Weathering on the Surface of Mars | date = 1993 | last1 = Burns | first1 = Roger G. | last2 = Fisher | first2 = Duncan S. | journal = Journal of Geophysical Research | volume = 98 | issue = E2 | pages = 3365–3372 |</ref> <ref>Hurowitz | first1 = J. A. | last2 = Fischer | first2 = W. W. | last3 = Tosca | first3 = N. J. | last4 = Milliken | first4 = R. E. | year = 2010 | title = Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars | url = https://authors.library.caltech.edu/18444/2/ngeo831-s1.pdf| journal = Nat. Geosci. | volume = 3 | issue = 5| pages = 323–326 | doi = 10.1038/ngeo831 | </ref> Sometimes a crater may have been filled up with layered rocks and then the rocks may have been eroded by the wind in such a way to just leave a layered mound in the center of the crater. Gale crater, where Curiosity is exploring, was like that.

<gallery class="center" widths="380px" heights="360px">

Image:Topographic Map of Gale Crater.jpg|Gale Crater with Aeolis Mons rising from the center. The noted [[Curiosity]] landing area is near Peace Vallis in Aeolis Palus. Curiosity landed in the northern part of the crater. Colors indicate elevation.

File:Marscratermounds.jpg|Some layers form mounds in the center of craters. They could have been made by the erosion of layers that were deposited after the impact.

</gallery>

[[File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|600pxr|Rock layers in the Murray Buttes area in lower Mount Sharp They look like rocks formed at the bottom of lakes and their chemistry proves it.]]

Rock layers in the Murray Buttes area in lower Mount Sharp

==Igneous effects==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

<gallery class="center" widths="380px" heights="360px">
File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons

</gallery>

Igneous refers to rock that is heated to a molten condition. On Mars, this is a major shaper of landscapes. Lava comes out of the ground at holes called vents. Flows of lava can be about as fluid as water and move long distances. Sometimes the top cools to a solid, but the liquid rock continues to flow underneath a hard crust. Giant pieces of this stiff crust can move around as “lava rafts.”

<gallery class="center" widths="380px" heights="360px">

File:ESP 054891 2040lavarafts.jpg|Lava rafts
</gallery>

In other places, lava travels in channels. When they make a hard crust, lave tunnels are created. A picture below shows lava tunnels.<ref> https://www.uahirise.org/PSP_009501_1755</ref> After the liquid lava moves away, an empty tunnel can be formed. These are significant for future colonists as they may be where our first colonies will be built. There people would be protected from surface radiation. We have already found spots that might be openings to these tunnels in HiRISE images.

[[File:PSP 009501 1755lavatube.jpg |Lava tubes and lava tunnels Future colonists may live in lava tunnels.]]

[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|left|Possible cave entrance to a lava tunnel Future colonies may live in caves for protection from weather and radiation.]]

[[File:Tharsis mons Viking.jpg |right|thumb|px|Some of the Martian volcanoes, as seen by Viking 1]]

There are huge volcanoes that were noticed by our first spacecraft to orbit the planet. The first satellite to orbit the planet was only able to see a few volcanoes peeking above a massive global dust storm. Since Mars has not had plate tectonics for nearly all of its history, volcanoes can grow very large.<ref>https://www.jpl.nasa.gov/edu/learn/video/mars-in-a-minute-how-did-mars-get-such-enormous-mountains/</ref> Lava and ash can erupt from the same spot for long periods of time. On the Earth, the plates move so volcanoes can only grow so big.

<gallery class="center" widths="380px" heights="360px">

File:Olympus Mons alt.jpg|Olympus Mons, tallest volcano in solar system The mass of volcanoes on mars stretches and cracks the crust causing faults.

</gallery>

Volcanoes are only the surface manifestations of liquid rock. There is more molted rock moving under the surface than what we see above ground in volcanoes. Molted rock is called magma when underground. Stretching out around volcanoes underground are various structures. Vast linear walls, called dikes radiate out from volcanoes. On Mars they can be many miles in length. Many form by moving along cracks or weak parts of rocks. Some scientists have suggested that they from long troughs when they melt ground ice. Troughs are some of the longest features on Mars.

<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 2100dike2.jpg|Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

</gallery>

Besides the direct action of lava and magma, volcanoes affect Mars with just their weight. The mass of a volcano stretches the crust and makes cracks form. The large canyon system of Valles Marineris may have been started with some sort of stretching of the crust. But, its stretching may have been caused by rising mantle plumes or maybe the rise of Tharsis where so many volcanoes are located.<ref>https://astronomy.com/magazine/ask-astro/2013/08/valles-marineris</ref> Cracks in the crust are called faults. Faults on Mars are often double faults. A center section is lower than the sides. This arrangement is called a graben. On the Earth they can turn into lakes like Lake George in New York State. Graben on Mars can be thousands of miles long.

Researchers have discovered that there is a large plume under Cerberus Fossae. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). Plumes like this are like the plume under Hawaii.

Evidence for the plume are (1) origin of nearly all Marsquakes, (2) a rise of a mile above the surroundings, (3) crater floors tilted away from the rise, and (4) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.

The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

<gallery class="center" widths="380px" heights="360px">

File:Troughs in Elysium Planitia.jpg|Troughs showing layers The center section of the picture is in color. With HiRISE only a strip in the middle is in color. These troughs are in Cerberus Fossae, as seen by HiRISE under the HiWish program. Location is 15.819 N and 161.448 E. Cerberus Fossae is the source of most of the Marsqukes detected by the InSight mission.

ESP 046251 2165graben.jpg|Straight trough is a fossa that would be classified as a graben. Curved channels may have carried lava/water from the fossa. Picture taken with HiRISE under [[HiWish program]].

File:ESP 057834 2005troughmesa.jpg|Trough or graben cutting through mesa
</gallery>

Sometimes lava moves over frozen ground. That results in steam explosions. Large fields of small cones can be produced when this happens. Those cones are called “rootless cones” since they do not go down very far.

<gallery class="center" widths="380px" heights="360px">

File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones
File:45384 2065cones2.jpg|Close view of rootless cones
</gallery>

Volcanoes sometimes explode with great amounts of ash that travels long distances, covering everything. Some of the layers seen on Mars are probably from these ash deposits. These deposits do not contain boulders and are easily eroded by just the wind. Two areas on Mars have widespread and thick deposits made in this way; they are called the Medusae Fossae Formation and the Electris deposits. These relatively soft deposits often form shapes called yardangs. They are sort of boat shaped and show the direction of the prevailing wind when they were created.

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
</gallery>

Much of the atmosphere of Mars came from volcanoes. Volcanoes give off large amounts of carbon dioxide and water, along with other chemicals. Some of these chemical compounds are “greenhouse gases” that served to heat up early Mars.
A few places are thought to be where volcanoes erupted under ice. The shapes that resulted look like those made on Earth when a volcano erupted under the ice.

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

==Bright dust==

A thin coating of bright-toned dust covers almost all parts of Mars. It has a rust brown color. It is not too noticeable until it is not here. Some things remove the dust and then reveal the dark underlying surface. The contrast between this thin coating and the underlying dark rock is striking. Much of the difference derives from how NASA pictures are processed.<ref> Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> To bring out more detail, the brightest tone is considered white, while the darkest black. It only takes a very thin layer of dust to make a difference in the over-all appearance of a picture. Experiments on Earth found that the layer may be only as thick as the diameter of a human hair.<ref> https://en.wikipedia.org/wiki/Micrometre
</ref> Incidentally, the dust has the color of rust because it is rust—it is oxidized iron.

Dark slope streaks occur when bright dust avalanches down steep slopes like crater walls. They can be very long and elaborate. These movements are affected by obstacles like boulders. A streak may split into two when encountering a boulder. They may be initiated when an impact happens nearby.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars" ''Icarus'' 2012; 217 (1) 194 </ref><ref>http://redplanet.asu.edu/</ref>
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>

[[File:ESP 043128 2005mesastreaks.jpg|600pxr|Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]]]

Dark slope streaks on layered mesa

[[File:55107 1930streaksboulders2.jpg|thumb|500px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

<gallery class="center" widths="380px" heights="360px">

</gallery>

Another thing that causes light and dark patterns is a dust devil. These miniature tornadoes remove the bright dust and make straight and/or curved tracks. They are common especially in areas with much dust cover and at certain times of the day. They have been observed both from orbit and from the ground.<ref>https://www.uahirise.org/ESP_042201_1715</ref> We even have movies of them in action. They can form beautiful scenes. And, the arrangement of the tracks can be different in just a few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">
</gallery>

The atmosphere of Mars contains a great deal of fine dust. Large dust storms happen just about every Martian year. A year on Mars is about 23 of our months. Dust storms typically occur when it is spring or summer in the southern hemisphere. At that time, Mars is at its closest to the sun. Unlike the Earth, Mars has a very elliptical orbit which brings it much closer to the sun than at other times. This makes for differences in season both in intensity and length. For example the southern summer is much shorter than that of the north. However, the summer season in the southern hemisphere is much more intense.

[[File:Marsorbitsolarsystem.gif|Comparrsion of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle.<ref> https://www.compadre.org/osp/items/detail.cfm?ID=9757</ref> <ref> https://www.compadre.org/osp/items/detail.cfm?ID=7305</ref>]]

Comparison of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle. Mars changes its distances to sun a great deal--this changes makes drastic seasonal changes.

==Dry Ice==

Some of the strangest things on Mars involve dry ice—solid carbon dioxide. The cold conditions on Mars cause much of the carbon dioxide to freeze out of the atmosphere. Both ice caps contain some dry ice. Each year about 25% of the atmosphere freezes out onto the poles. This is so much that the gravity of the planet shifts. <ref>NASA/Goddard Space Flight Center. "New gravity map gives best view yet inside Mars." ScienceDaily. ScienceDaily, 21 March 2016. https://www.sciencedaily.com/releases/2016/03/160321154013.htm.</ref> <ref>Antonio Genova, Sander Goossens, Frank G. Lemoine, Erwan Mazarico, Gregory A. Neumann, David E. Smith, Maria T. Zuber. Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science. Icarus, 2016; 272: 228 DOI: 10.1016/j.icarus.2016.02.05</ref> Winds and weather systems that almost look like the Earth’s are produced by so much dry ice changing to a gas at these times.

[[File:PIA00190-MC-30-MareAustraleRegion-19980605.jpg |right|thumb|px| Region of South Pole with ice cap Southern ice cap is much smaller than the North’s.]]

[[File:Mars NPArea-PIA00161.jpg |left|thumb|px| Spiral troughs in the northern ice cap]]

<gallery class="center" widths="380px" heights="360px">

File:Marscyclone hst.jpg|Cyclone on Mars, as seen by HST
</gallery>

In the winter dry ice accumulates. So, large areas appear white. When things warm up in the spring, the landscape gets many dark spots and areas. <ref>https://mars.jpl.nasa.gov/mgs/msss/camera/images/dune_defrost_6_2001/</ref><ref>SPRING DEFROSTING OF MARTIAN POLAR REGIONS: MARS GLOBAL SURVEYOR MOC AND TES MONITORING OF THE RICHARDSON CRATER DUNE FIELD, 1999–2000. K. S. Edgett, K. D. Supulver, and M. C. Malin, Malin Space Science Systems, P.O. Box 910148, San Diego, CA 92191-0148, USA.</ref> <ref>K.-Michael Aye, K., et al. PROBING THE MARTIAN SOUTH POLAR WINDS BY MAPPING CO2 JET DEPOSITS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2841.pdf</ref> In the past, observers thought that Mars was full of life. They saw the northern ice cap get smaller and smaller. At the same time, they watched the area get darker. They concluded that the darkening was vegetation growing from the water coming out of the ice caps. What was happening was the dry ice was disappearing. Today, we can watch this darkening occur in great detail. <ref>http://www.jpl.nasa.gov/news/news.php?release=2013-034</ref>

<gallery class="center" widths="380px" heights="360px">

43821 2555defrostingdune2.jpg|Defrosting surface Frost is disappearing in patches from a dune and from the surrounding surface. Note: the north side (side near top) has not defrosted because the sun is coming from the other side.

File:ESP 011605 1170defrosting.jpg|Defrosting The dark spots are where the ice has gone. We now can see the underlying dark surface.

</gallery>

In some places, there are many geyser-like eruptions of gas and dark dust.<ref>https://www.uahirise.org/</ref> High pressure gas and dust explode out of the ground. Winds often blow these eruptions into dark plumes. After many observations, scientists concluded that what happens is that a transparent-translucent dry ice slab forms in the winter. With increased sun in the spring, pressure builds up under this slab as light heats cavities under the slab and causes dry ice to turn into a gas. At weak areas in the slab, the gas comes out along with dark dust.<ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> The channels may get dark from the dust and make a pattern that looks like a spider. These patterns are called “spiders.” <ref>http://mars.jpl.nasa.gov/multimedia/images/2016/possible-development-stages-of-martian-spiders</ref> <ref>http://spaceref.com/mars/growth-of-a-martian-trough-network.html</ref> <ref>Benson, M. 2012. Planetfall: New Solar System Visions</ref> <ref>http://www.astrobio.net/topic/solar-system/mars/spiders-invade-mars/</ref> <ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>Portyankina, G., et al. 2017. Present-day erosion of Martian polar terrain by the seasonal CO2 jets. Icarus: 282, 93-103.</ref> The official name for spiders is "araneiforms."<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>

<gallery class="center" widths="380px" heights="360px">

File:Spiders2eruptionlabeled2.jpg|Drawing showing the cause of plumes and spiders. In the spring, sunlight goes through a clear slap of dry ice. It heats up the dark ground. Heat causes dry ice to turn into a gas and pressurize. When pressure is great enough a dark plume of carbon dioxide gas and dark dust erupt. Wind will form it into a fan shape plume.

</gallery>

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

<gallery class="center" widths="380px" heights="360px">

ESP 048845 1010spiders.jpg|Wide view of crater that contains examples of spiders
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
</gallery>

Around the southern cap, dry ice makes round, low areas that look like Swiss cheese. <ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data
Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> So, it is called “Swiss cheese terrain.” The roundness of the pits is believed to be related to the low angle of the sun.<ref>Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

[[File:South Pole Terrain.jpg|600pxr|HiRISE view of South Pole Terrain.]]
HiRISE view of South Pole Terrain.

<gallery class="center" widths="380px" heights="360px">
</gallery>

The ice caps contain a great deal of water ice. The northern cap has a covering of dry ice only 1 meter thick in the winter, but the southern cap always has a coating of dry ice up to 8 meters thick. Large deposits of dry ice are also buried in the water ice of the cap at some locations.

<gallery class="center" widths="380px" heights="360px">
</gallery>

==Gullies==

Since 2000, researchers have been studying gullies that are common in the mid-latitudes on steep slopes. They look like they were carved by liquid water. After many years of observations, it has been concluded that today they are being made by chunks of dry ice sliding down slopes.<ref>Vincendon, M. 2015. JGR:120, 1859–1879.</ref> <ref> Pilorget | first1 = C. | last2 = Forget | first2 = F. | year = 2016 | title = Formation of gullies on Mars by debris flows triggered by CO2 sublimation | url = | journal = Nature Geoscience | volume = 9 | issue = | pages = 65–69 | doi = 10.1038/ngeo2619 | </ref> <ref>Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.</ref> However, some scientists concede that water may have been involved in their formation in the past.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm</ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 047956 1420gullies.jpg|Crater with gullies, as seen by HiRISE under HiWish program
File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
</gallery>

[[File:Gullies near Newton Crater.jpg|600pxr|Gullies near Newton Crater]]
Gullies near Newton Crater

==Other features==

The surface of Mars is very old—billions of years. This is plenty of time for rocks to have broken down into sand. In low places, like crater floors, sand accumulates and makes dunes. Some are quite pretty. And the colors used by NASA make them even more pretty—they can appear blue, purple, green, or turquoise.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:61974 1710dunesrgb2.jpg|Dunes
File:ESP 046378 1415dunefield.jpg|Black and white, wide view of dunes
File:ESP 55095 2170dunes.jpg|Dunes near Sklodowski Crater in North Arabia Terra
</gallery>

Related to dunes are something called transverse aeolian ridges (TAR’s). They look like small dunes. They are often parallel to each other. They generally are in low areas and one of the most common landforms on Mars.<ref>http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1598.pdf|format=PDF|type=conference paper|title=Investigations of transverse aeolian ridges on Mars|first1=Daniel C.|last1=Berman|first2=Matthew R.|last2=Balme|year=2012|publisher=Lunar and Planetary Science Conference</ref> They are mid-way in height between dunes and ripples; they are not well understood.<ref>http://www.uahirise.org/ESP_042625_1655</ref> <ref>Berman, D., et al. 2018. High-resolution investigations of Transverse Aeolian Ridges on Mars: Icarus: 312, 247-266.</ref>

<gallery class="center" widths="380px" heights="360px">

File:64038 2155tarslabeled.jpg|Transverse Aeolian Ridges, as seen by HiRISE under HiWish program

File:ESP 039563 1730tars.jpg|Transverse Aeolian Ridges (TAR’s) between yardangs We do not totally understand these.
File:ESP 042625 1655tars.jpg|Wide view of Transverse Aeolian Ridges (TAR’s) near a channel
</gallery>

Some landscape expressions are mysteries.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>

In rocks of certain ages, often at the bottom of low spots are complex arrangements of ridges.
These are walls of rock.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>

There are different ideas for what caused them. Over 14,000 people from around the world helped map them, so that scientists could better understand them. The team of volunteers found 952 polygonal ridge networks in an area that measures about a fifth of Mars’ total surface area. Some ridges contain clays, so water may have been involved in their formation because clays need water to be formed.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al. 2022. Irregular polygonal ridge networks in ancient Noachian terrain on Mars. Icarus. 374. 114833</ref>

[[File:ESP 036745 1905top.jpg|600pxr|Linear ridge networks]]
Linear ridge networks

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
</gallery>

[[File:Ridgesmappedbycitizens.jpg|600pxr|Map of Linear ridge networks]]

Map of Linear ridge networks

Of eerie beauty are odd arrangements visible on the bottom of the Hellas Impact basin. We are not sure exactly what caused them. They have been called honeycomb terrain or banded terrain.

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Honeycomb terrain on floor of Hellas Basin The exact origin of these shapes is unknown at present.

<gallery class="center" widths="380px" heights="360px">

</gallery>

Mars is one planet that we can see the surface clearly. Its super thin atmosphere (about 1% of the Earth’s) makes it easy to observe. Early telescopes revealed many markings and patterns. As we sent better and better cameras to examine it, more mysteries and more beautiful scenes emerged. We were able to answer many questions, but always more questions arose concerning what we were seeing.

<gallery class="center" widths="380px" heights="360px">

</gallery>

==References==

{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]

*[https://www.youtube.com/watch?v=jcaawA7d0ro Sublimation of Dry Ice]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]

==Recommended reading==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf
*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

Mare Acidalium quadrangle

2023-04-17T22:19:45Z

Suitupandshowup: /* Channels */ added image

{{Mars atlas}}

{| class="wikitable sortable"
|MC-04
|Mare Acidalium
|30–65° N
|0–60° W
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-4-MareAcidaliumRegion-mola.png
File:PIA00164-MC-4-MareAcidaliumRegion-19980604.jpg
</gallery>

The [[The Face on Mars|face on Mars]] is found in the lower right corner or the Mare Acidalium quadrangle, between the craters Aranda and Bamberg in the [[Cydonia]] Labyrinthus region.

The Mare Acidalium quadrangle contains many interesting features, but is most famous for an eroded mesa that looked like a face when originally seen in Viking images in the 70’s. Outstanding views of polygonal ground, mud volcanoes, gullies, and channels are here. In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

The Mare Acidalium quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS). The quadrangle is located in the northern hemisphere and covers 30° to 65° north latitude and 0° to 60° west longitude (300° to 360° east longitude). The Mare Acidalium quadrangle is also referred to as MC-4 (Mars Chart-4).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>
The southern and northern borders of the quadrangle are approximately 3,065 km and 1,500 km wide, respectively. The north to south distance is about 2,050 km (slightly less than the length of Greenland).<ref>Distances calculated using NASA World Wind measuring tool. http://worldwind.arc.nasa.gov/.</ref> The quadrangle covers a little over 3% of Mars’ surface.

Many regions with classical names are located here. Most of the region called Acidalia Planitia is found in Acidalium quadrangle. Parts of Tempe Terra, Arabia Terra, and Chryse Planitia are also in this quadrangle. This area contains many bright spots on a dark background that may be mud volcanoes. Lomonosov Crater and Kunowsky Crater are easily seen. The famous "face" on Mars is located in the [[Cydonia]] Mensae area--the southeastern part of quadrangle.

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

The quadrangle contains many interesting features, including gullies and possible shorelines of an ancient northern ocean. Some areas are densely layered. The boundary between the southern highlands and the northern lowlands lies in Mare Acidalium.<ref>http://hirise.lpl.arizona.edu/PSP_010354_2165</ref> The Cydonia Region includes the Face on Mars (located near 40.8 degrees north and 9.6 degrees west). When Mars Global Surveyor examined it with high resolution, the face turned out to just be an eroded mesa.<ref>http://mars.jpl.nasa.gov/mgs/msss/camera/images/moc_5_24_01/face/index.html</ref> Mare Acidalium contains the Kasei Valles system of canyons. This huge system is 300 miles wide in some places—Earth's Grand Canyon is only 18 miles wide.<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_001640_2125</ref>

==Origin of name==

Mare Acidalium (Acidalian Sea) is the name of a classical albedo features on Mars located at 45° N and 330° E on Mars. The feature was named for a well or fountain in Boeotia, Greece. According to classical tradition, it is a location where Venus and the Graces bathed.<ref>Blunck, J. 1982. Mars and its Satellites. Exposition Press. Smithtown, N.Y.</ref> The name was approved by the International Astronomical Union (IAU) in 1958.<ref>USGS Gazetteer of Planetary Nomenclature. Mars. http://planetarynames.wr.usgs.gov/.</ref>

== Gullies ==

[[File:Acidalia Colles Gullies.JPG|600pxr|Acidalia Colles Gullies and other features, as seen by HiRISE The scale bar is 1,000 meters long.]]

Acidalia Colles Gullies and other features, as seen by HiRISE The scale bar is 1,000 meters long.

The HiRISE image above of Acidalia Colles shows gullies in the northern hemisphere. Gullies occur on steep slopes, especially craters. Gullies are believed to be relatively young because they have few, if any craters, and they lie on top of sand dunes which are themselves young. Usually, each gully has an alcove, channel, and apron. Many researchers believed that the processes carving the gullies involved liquid water. However, with more observations and research this idea was changed.
As soon as gullies were discovered, researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found.<ref>Malin, M., K. Edgett, L. Posiolova, S. McColley, E. Dobrea. 2006. Present-day impact cratering rate and contemporary gully activity on Mars. Science 314, 1573_1577.</ref> Later, with further analysis it was determined that the changes could have occurred with dry granular flows rather than being driven by flowing water.<ref>Kolb, et al. 2010. Investigating gully flow emplacement mechanisms using apex slopes. Icarus 2008, 132-142.</ref> <ref>McEwen, A. et al. 2007. A closer look at water-related geological activity on Mars. Science 317, 1706-1708.</ref> <ref>Pelletier, J., et al. 2008. Recent bright gully deposits on Mars wet or dry flow? Geology 36, 211-214.</ref> With continued observations many more changes were found in Gasa Crater and other craters.<ref>NASA/Jet Propulsion Laboratory. "NASA orbiter finds new gully channel on Mars." ScienceDaily. ScienceDaily, 22 March 2014. www.sciencedaily.com/releases/2014/03/140322094409.htm</ref>
With more repeated observations, more and more changes were found; since the changes occur in the winter and spring, experts are tending to believe that gullies were formed from dry ice. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon-dioxide frost changes, and at temperatures that would not have allowed for liquid water. The conditions during gully formation are just about right to allow chunks of dry ice to slide down slopes. In addition, when dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes.<ref>http://www.jpl.nasa.gov/news/news.php?release=2014-226</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032078_1420</ref><ref>http://www.space.com/26534-mars-gullies-dry-ice.html</ref> In some years frost build up may be-as thick as 1 meter.

<gallery class="center" widths="380px" heights="360px">

Image:24951bambergwidectx.jpg|Context for next image of Bamberg crater. Box shows where the next image came from. This is a CTX image from [[Mars Reconnaissance Orbiter]].

Image:ESP 024951gulliesandflow.jpg|Gullies and massive flow of material, as seen by HiRISE under [[HiWish program]]. Gullies are enlarged in next two images.

Image:24951gulliesclose.jpg|Close up view of some gullies

Image:24951gullyclose.jpg|Close up view of another gully in same HiRISE picture. Picture taken under HiWish program.

Image:27707gulliesclose.jpg|Close-up of gullies in a crater Image taken by HiRISE under HiWish program.

ESP 037506 2285gullychannels.jpg|Gullies on wall of crater

ESP 037506 2285gullychannelsclose.jpg|Close-up of gully channels This image shows many streamlined forms and some benches along a channel. These features suggest formation by running water. Benches are usually formed when the water level goes down a bit and stays at that level for a time.

File:ESP 053751 2150gullies.jpg|Gullies

File:55122 2225gulliesclosecolor.jpg|Gullies, as seen by HiRISE under [[HiWish program]]
</gallery>

==Polygonal patterned ground==

[[File:27707 2195gullygonsclose2.jpg|600pxr|Close-up of gully alcove showing "gullygons" (polygonal patterned ground near gullies), as seen by HiRISE under HiWish program]]
Close-up of gully alcove showing "gullygons" (polygonal patterned ground near gullies), as seen by HiRISE under HiWish program

Polygonal, patterned ground is quite common in some regions of Mars.<ref>http://www.diss.fu-berlin.de/diss/servlets/MCRFileNodeServlet/FUDISS_derivate_000000003198/16_ColdClimateLandforms-13-utopia.pdf?hosts=</ref> <ref>Kostama, V.-P., M. Kreslavsky, Head, J. 2006. Recent high-latitude icy mantle in the northern plains of Mars: Characteristics and ages of emplacement. Geophys. Res. Lett. 33 (L11201). doi:10.1029/2006GL025946.</ref> <ref>Malin, M., Edgett, K. 2001. Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res. 106 (E10), 23429–23540.</ref> <ref>Milliken, R., et al. 2003. Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images. J. Geophys. Res. 108 (E6). doi:10.1029/2002JE002005.</ref> <ref>Mangold | first1 = N | year = 2005 | title = High latitude patterned grounds on Mars: Classification, distribution and climatic control | url = | journal = Icarus | volume = 174 | issue = | pages = 336–359 | doi = 10.1016/j.icarus.2004.07.030 | </ref> <ref>Kreslavsky, M., Head, J. 2000. Kilometer-scale roughness on Mars: Results from MOLA data analysis. J. Geophys. Res. 105 (E11), 26695–26712.</ref> <ref>Seibert | first1 = N. | last2 = Kargel | first2 = J. | year = 2001 | title = Small-scale martian polygonal terrain: Implications for liquid surface water | url = | journal = Geophys. Res. Lett. | volume = 28 | issue = 5| pages = 899–902 | doi = 10.1029/2000gl012093 | </ref> It is commonly believed that the shapes we see here are related to ground frozen with water ice.

<gallery class="center" widths="380px" heights="360px">

27707 2195gullygonsclose.jpg|Close-up of gully alcove showing "gullygons" (polygonal patterned ground near gullies)

</gallery>

==Craters==

Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits.<ref>Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|accessdate=7 March 2011|year=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7 </ref> Sometimes craters display layers. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, craters can show us what lies deep under the surface.

<gallery class="center" widths="380px" heights="360px">

Image:Arandas Crater.JPG|Arandas Crater, as seen by HiRISE. Scale bar is 1000 meters long.

Image:Exhumedburied Craterin Coprates.jpg|Exhumed Crater in Mare Acidalium, as seen by [[Mars Global Surveyor]] This crater was buried and now it is being uncovered.

Image:ESP 026594 1470closecraters.jpg|Craters that formed at the same time. If the craters were formed at different times, they would have wiped away parts of the others. These craters may been made when an asteroid broke up in the atmosphere. Picture was taken by HiRISE, under HiWish program. Image located in Terra Cimmeria.

Image:ESP 027538 2265.jpg|Crater wall covered with a smooth mantle

ESP 052749 2285pits.jpg|Crater with pits on floor, as seen by HiRISE under [[HiWish program]]

</gallery>

==Mud volcanoes==

[[File:ESP 047053 2165cones.jpg|600pxr|Line of possible mud volcanoes]]
Line of possible mud volcanoes

Large areas of Mare Acidalium display bright spots on a dark background. It has been suggested that these spots are mud volcanoes.<ref>Farrand | first1 = W. | display-authors = etal | year = 2005 | title = Pitted cones and domes on Mars: observations in Acidalia Planitia and Cydonia Mensae using MOC, THEMIS, and TES data | url = | journal = J. Geophys. Res. | volume = 110 | issue = | page = 14 | doi = 10.1029/2004JE002297 </ref> <ref>Tanaka, K. et al. 2003 Resurfacing history of the northern plains of Mars based on geologic mapping of Mars Global Surveyor data. J. Geophys. Res. 108 (E4), doi:10.1029/2002JE001908.</ref><ref>Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM</ref> More than 18,000 of these features, which have an average diameter of about 800 meters, have been mapped.<ref>Oehler, D. and C. Allen. 2010. Evidence for pervasive mud volcanism in Acidalia Planitia, Mars. Icarus: 208. 636-657.</ref> As more observations poured in over the years, more evidence supported the notion that these abundant bright marks are mud volcanoes. Mare Acidalium would have received large quantities of mud and fluids form outflow channels, so much mud may have accumulated there. The bright mounds have been found to contain crystalline ferric oxides. Mud volcanism may be highly significant because long lived conduits for upwelling groundwater could have been produced. These could have been habitats for micro organisms.<ref>Komatsu, G., et al. 2014. ASTROBIOLOGICAL POTENTIAL OF MUD VOLCANISM ON MARS. 45th Lunar and Planetary Science Conference (2014). 1085.pdf</ref> Mud volcanoes could have brought up samples from deep zones that could be gathered by robots.<ref>Oehler | first1 = D | last2 = Allen | first2 = C. | year = 2011 | title = Evidence for pervasive mud volcanism in Acidalia Planitia, Mars | url = | journal = Icarus | volume = 208 | issue = | pages = 636–657 | doi = 10.1016/j.icarus.2010.03.031 }}</ref> The authors of an article in Icarus compare these Martian features to mud volcanoes found on the Earth. Their study using HiRISE images and CRISM data support the idea that these features are indeed mud volcanoes. Nanophase ferric minerals and hydrated minerals found with Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show that water was involved with the formation of these possible Martian mud volcanoes.<ref>Komatsu, G., et al. 2016. Small edifice features in Chryse Planitia, Mars: Assessment of a mud volcano hypothesis. Icarus: 268, 56-75.</ref> Scientists are excited that Mars may have mud volcanoes because these small volcanoes may have brought up samples of dirt that were not affected by the high radiation on the Martian surface. We may find evidence of past life in these volcanoes.

<gallery class="center" widths="380px" heights="360px">

Image:White craters in Mare Acidalium.JPG|Craters with white centers in Mare Acidalium. Sand dunes are visible in low areas in image. Some of the features may be mud volcanoes. Picture taken by [[Mars Global Surveyor]] under the MOC Public Targeting Program.

ESP 040775 2235cones.jpg|Large field of cones that may be mud volcanoes

040775 2235conesclose.jpg|Close-up of possible mud volcanoes Note: this is an enlargement of the previous image.

ESP 044665 2240cone.jpg|Possible mud volcano, as seen by HiRISE under [[HiWish program]]

ESP 046617 2210mudvolcanoes.jpg|Mud volcanoes
</gallery>

<gallery class="center" widths="190px" heights="180px" >
ESP 052050 2200mudvolcanoes.jpg|Wide view of field of mud volcanoes

</gallery>

<gallery class="center" widths="380px" heights="360px">
Gobustan State Reserve 04.png|Close view of mud volcanoes on Earth Location is Gobustan Azerbaijan.
</gallery>

==Channels in Idaeus Fossae region==

There is a 300 km long ancient river system in Idaeus Fossae. It is carved into the highlands of Idaeus Fossae, and it originated from the melting of ice in the ground after asteroid impacts. There is evidence that it was formed relatively recently. Dating has determined that the water activity came after most of the water activity ended at the boundary between the Noachian and Hesperian periods. Lakes and fan-shaped deposits were formed by running water in this system as it drained eastward into Liberta Crater and formed a delta deposit. Part of the drainage path is the Moa Valley.<ref>Salese, F., G. Di Achille, F., et al. 2016. Hydrological and sedimentary analyses of well-preserved paleo fluvial-paleolacustrine systems at Moa Valles, Mars. J. Geophys. Res. Planets. 121, 194–232, doi:10.1002/2015JE004891.</ref> <ref>Salese, F., G. Di Achille, G. Ori. 2015. SEDIMENTOLOGY OF A RIVER SYSTEM WITH A SERIES OF DAM-BREACH PALEOLAKES AT IDAEUS FOSSAE, MARS. 46th Lunar and Planetary Science Conference 2296.pdf</ref>

<gallery class="center" widths="380px" heights="360px">

File:29054cutoff.jpg|Stream meander and cutoff, as seen by HiRISE under HiWish program. This is part of a major drainage system in the Idaeus Fossae region.
ESP 045590 2170hanging.jpg|Hanging valley, as seen by HiRISE under HiWish program This may have been a waterfall at one time.
ESP 045946 2170channel.jpg|Hanging valley that once may have been a waterfall, as seen by HiRISE under HiWish program
</gallery>

==Channels==

[[File:ESP 045867 2150channels.jpg|600pxr|Channels]]
Channels

There is much evidence that water once flowed in river valleys on Mars.<ref>Baker | first1 = V. | display-authors = etal | year = 2015 | title = Fluvial geomorphology on Earth-like planetary surfaces: a review | journal = Geomorphology | volume = 245 | issue = | pages = 149–182 |</ref> <ref>Carr, M. 1996. in Water on Mars. Oxford Univ. Press.</ref> Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the [[Mariner 9]] orbiter.<ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker | first1 = V. | last2 = Strom | first2 = R. | last3 = Gulick | first3 = V. | last4 = Kargel | first4 = J. | last5 = Komatsu | first5 = G. | last6 = Kale | first6 = V. | year = 1991 | title = Ancient oceans, ice sheets and the hydrological cycle on Mars | url = | journal = Nature | volume = 352 | issue = | pages = 589–594 | doi = 10.1038/352589a0 | </ref> <ref> Carr | first1 = M | year = 1979 | title = Formation of Martian flood features by release of water from confined aquifers | url = | journal = J. Geophys. Res. | volume = 84 | issue = | pages = 2995–300 | doi = 10.1029/jb084ib06p02995 | </ref> <ref>Komar | first1 = P | year = 1979 | title = Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth | url = | journal = Icarus | volume = 37 | issue = | pages = 156–181 | doi = 10.1016/0019-1035(79)90123-4 | </ref> We have seen more and more channels with each orbiter mission to the Red Planet. Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had.<ref>http://spaceref.com/mars/how-much-water-was-needed-to-carve-valleys-on-mars.html</ref><ref>Luo, W., et al. 2017. New Martian valley network volume estimate consistent with ancient ocean and warm and wet climate. Nature Communications 8. Article number: 15766 (2017). doi:10.1038/ncomms15766</ref>

<gallery class="center" widths="380px" heights="360px">

Wikisklodowskachannels.jpg|Channels in Sklodowska Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter)
WikisklodowskaESP 035500 2130.jpg|Channels in Sklodowska Crater

ESP 048003 2165channels.jpg|Channels, as seen by HiRISE under HiWish program

</gallery>

[[File:ESP 055374 2175channelnetwork.jpg|600pxr|Channel network]]
Channel network

[[File:ESP 077583 2255inverted.jpg|thumb|500px|center|Inverted stream, a stream bed has been filled with hard materials that did not erode away like the surroundings]]

==Ocean==

Many researchers have suggested that Mars once had a great ocean in the north.<ref>Parker | first1 = T. J. | last2 = Gorsline | first2 = D. S. | last3 = Saunders | first3 = R. S. | last4 = Pieri | first4 = D. C. | last5 = Schneeberger | first5 = D. M. | year = 1993 | title = Coastal geomorphology of the Martian northern plains | url = | journal = J. Geophys. Res. | volume = 98 | issue = E6| pages = 11061–11078 | doi=10.1029/93je00618 |</ref> <ref>Fairén | first1 = A. G. |display-authors=etal | year = 2003 | title = Episodic flood inundations of the northern plains of Mars | url = http://eprints.ucm.es/10431/1/9-Marte_3.pdf| journal = Icarus | volume = 165 | issue = 1| pages = 53–67 | </ref> <ref> Head | first1 = J. W. |display-authors=etal | year = 1999 | title = Possible ancient oceans on Mars: Evidence from Mars Orbiter Laser Altimeter data | url = | journal = Science | volume = 286 | issue = 5447| pages = 2134–2137 | doi=10.1126/science.286.5447.2134| pmid = 10591640 |</ref> <ref>Parker, T. J., Saunders, R. S. & Schneeberger, D. M. Transitional morphology in west Deuteronilus Mensae, Mars: Implications for modification of the lowland/upland boundary" ''Icarus'' 1989; 82, 111–145</ref> <ref>Carr | first1 = M. H. | last2 = Head | first2 = J. W. | year = 2003 | title = Oceans on Mars: An assessment of the observational evidence and possible fate | url = | journal = J. Geophys. Res. | volume = 108 | issue = E5| page = 5042 |</ref> <ref>Kreslavsky | first1 = M. A. | last2 = Head | first2 = J. W. | year = 2002| title = Fate of outflow channel effluent in the northern lowlands of Mars: The Vastitas Borealis Formation as a sublimation residue from frozen ponded bodies of water | url = | journal = J. Geophys. Res. | volume = 107 | issue = E12| page = 5121 |</ref> <ref>Clifford, S. M. & Parker, T. J. The evolution of the martian hydrosphere: Implications for the fate of a primordial ocean and the current state of the northern plains" ''Icarus'' 2001; 154, 40–79</ref> Much evidence for this ocean has been gathered over several decades. New evidence was published in May 2016. A large team of scientists described how some of the surface in Ismenius Lacus quadrangle was altered by two tsunamis. The tsunamis were caused by asteroids striking into an ocean. Both were thought to have been strong enough to create 30 km diameter craters. The first tsunami picked up and carried boulders the size of cars or small houses. The backwash from the wave formed channels by rearranging the boulders. The second came in when the ocean was 300 m lower. The second carried a great deal of ice which was dropped in valleys. Calculations show that the average height of the waves would have been 50 m, but the heights would vary from 10 m to 120 m. So, some large waves would have gone over a 36 story building.<ref>https://www.convertunits.com/from/metre/to/story</ref> Asteroids hitting an ocean on Mars are quite possible. Numerical simulations show that in this particular part of the ocean two 30 km in diameter would form every 30 million years. The implication here is that a great northern ocean may have existed for millions of years. One argument against an ocean has been the lack of shoreline features. But shoreline features may have been washed away by these tsunami events. The parts of Mars studied in this research are Chryse Planitia and northwestern Arabia Terra. These tsunamis affected some surfaces in the [[Ismenius Lacus quadrangle]] and in the Mare Acidalium quadrangle.<ref>Ancient Tsunami Evidence on Mars Reveals Life Potential |date=May 20, 2016 |url=http://astrobiology.com/2016/05/ancient-tsunami-evidence-on-mars-reveals-life-potential.html</ref> <ref>Rodriguez | first1 = J. |display-authors=etal | year = 2016 | title = Tsunami waves extensively resurfaced the shorelines of an early Martian ocean | url = | journal = Scientific Reports | volume = 6 | issue = | page = 25106 | doi=10.1038/srep25106| pmid = 27196957 | pmc = 4872529 |</ref> <ref>| doi=10.1038/srep25106| pmid=27196957| pmc=4872529| title=Tsunami waves extensively resurfaced the shorelines of an early Martian ocean| journal=Scientific Reports| volume=6| pages=25106| year=2016| last1=Rodriguez| first1=J. Alexis P.| last2=Fairén| first2=Alberto G.| last3=Tanaka| first3=Kenneth L.| last4=Zarroca| first4=Mario| last5=Linares| first5=Rogelio| last6=Platz| first6=Thomas| last7=Komatsu| first7=Goro| last8=Miyamoto| first8=Hideaki| last9=Kargel| first9=Jeffrey S.| last10=Yan| first10=Jianguo| last11=Gulick| first11=Virginia| last12=Higuchi| first12=Kana| last13=Baker| first13=Victor R.| last14=Glines| first14=Natalie</ref> <ref>Cornell University. "Ancient tsunami evidence on Mars reveals life potential." ScienceDaily. ScienceDaily, 19 May 2016. https://www.sciencedaily.com/releases/2016/05/160519101756.htm.</ref>

==Pingos==

Pingos are believed to be present on Mars. They are mounds that contain cracks. These particular fractures were evidently produced by something emerging from below the brittle surface of Mars. Ice lenses, resulting from the accumulation of ice beneath the surface, possibly created these mounds with fractures. Ice is less dense than rock, so the buried ice rose and pushed upwards on the surface and generated these cracks. An analogous process creates similar sized mounds in arctic tundra on Earth. The name ''pingos'' is an Inuit word.<ref>http://www.uahirise.org/ESP_046359_1250</ref> They contain pure water ice, so they would be a great source of water for future colonists on Mars.

[[File:44322 2215pingos.jpg|600pxr|Arrows point to possible pingos, as seen by HiRISE under HiWish program Pingos contain a core of pure ice.]]
Arrows point to possible pingos, as seen by HiRISE under HiWish program Pingos contain a core of pure ice.

==Fractured ground==

<gallery class="center" widths="380px" heights="360px">

44322 2215fractures.jpg|Fractures These fractures are believed to eventually turn into canyons because the cracks will get much larger when ice in the ground disappears into the thin Martian atmosphere and the remaining dust blows away.

ESP 046366 2215fractures.jpg|Wide view of fractured ground, as seen by HiRISE under HiWish program Cracks form on the Martian surface, and then they turn into large fractures.

46366 2215fractures.jpg|Close view of fractures from the previous image

File:ESP 056968 2140cracks.jpg|Cracks on crater floor

File:56968 2140cracks.jpg|Close view of cracks on crater floor, as seen by HiRISE under [[HiWish program]]

File:ESP 057311 2125cracks.jpg|Group of cracks

File:ESP 057311 2125crackscraters.jpg|Close view of cracks of various sizes Ice disappears along crack surfaces and makes crack larger. Note that small craters do not have very big rims; they may be just pits.

File:57311 2155crackssmallarge.jpg|Close view of cracks of various sizes Ice disappears along crack surfaces and makes crack larger.

File:57311 2155crackscrater.jpg|Cracks around crater, as seen by HiRISE under [[HiWish program]]

</gallery>

==Layers==

Layered terrain is common on the Earth and on Mars. Water is usually involved with the formation of layers. Hence, when we see layers, there is the possibility of a lake or sea in the past.

[[File:ESP 047080 2120layered mesa.jpg|600pxr|Layers in mesa, as seen by HiRISE under [[HiWish program]]]]
Layers in mesa, as seen by HiRISE under [[HiWish program]]

Rock can be formed into layers in a variety of ways. Volcanoes, wind, or water can produce layers<ref>http://hirise.lpl.arizona.edu?PSP_008437_1750</ref> Layers can be hardened by the action of groundwater. Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through. When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents.

<gallery class="center" widths="380px" heights="360px">

File:53490 2230layers.jpg|Close view of layers in a trough

</gallery>

==Features close to Face on Mars==

Here are some CTX images of area near the Face. These pictures show natural formations on Mars. In the area around the face are mesas, mud volcanoes, pedestal craters, and brain terrain. Many of the mesas are sitting on what looks like platforms. They may be from a change in sea level. There is strong evidence building that an ocean was once all through the northern lowlands. All of the features seen here are common on Mars, especially in this latitude. For more pictures and information about the face go to The [[The Face on Mars]].

<gallery class="center" widths="380px" heights="360px">

File:FaceG22 026771 2213 XI 41N009W.jpg|Terrain to the west of Face Face is visible in upper right.

File:FacectxT01 00807 2205glaciers.jpg|Terrain near Face showing possible glacier erosion Curved portions of the mounds look like the start of what are called cirques that form as snow accumulates on mountains.<ref>http://www.landforms.eu/cairngorms/corrie%20formation.htm</ref>

File:FacectxD02 027892 2219pyramid.jpg|Mud volcanoes in terrain near Face

File:Faceg22 026771 2213pedestal.jpg|Mesa, mud volcano, and pedestal crater in area near Face.

</gallery>
[[File:FacectxF23 044929 2199 XI 39N010Wlabeled.jpg|600pxr|Mesa, ridges, possible cirques near Face]]
Mesa, ridges, possible cirques near Face.

== Other landscape features in Mare Acidalium quadrangle ==

<gallery class="center" widths="380px" heights="360px">

Image:Cliff in Mare Acidalium.JPG|Cliff in Kasei Valles system, as seen by HiRISE

</gallery>

[[File:Rolling boulders in kasei.JPG|600pxr|Boulders that are about 2.2 yards acoss (smaller than a bedroom) and their tracks after rolling down a cliff in Kasei Valles system, as seen by HiRISE]]

Boulders that are about 2.2 yards across (smaller than a bedroom) and their tracks after rolling down a cliff in Kasei Valles system, as seen by HiRISE

<gallery class="center" widths="380px" heights="360px">

Image:Context for fault.JPG|CTX image showing the context for the next image of a fault The area in the black rectangle is enlarged in next photo.

Image:Fault in Mare Acidalium.JPG|Close-up of a possible fault in Mare Acidalium, as seen by HiRISE under the [[HiWish program]]. A circle is drawn around crater to show that it may be off round because of movement of the fault. Many other faults are in the region.

ESP 045524 2120fan.jpg|Fan with channels on its surface

48924 2150ovalpits.jpg|Sample of oval pits in this location of unknown origin, as seen by HiRISE under HiWish program

</gallery>

== See also ==

*[[The Face on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[HiWish program]]
*[[How are features on Mars Named?]]

*[[Layers on Mars]]
*[[Mars Global Surveyor]]

*[[Martian gullies]]
*[[Oceans on Mars]]

*[[Rivers on Mars]]

== References ==

[[Category:Mars Atlas]]

What Mars Actually Looks Like!

2023-04-17T22:14:44Z

Suitupandshowup: /* Inverted relief */ added image

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Almost all of the sites that we have landed on Mars with spacecraft have been to the most drab and boring places on the planet. This was done to ensure a safe landing. This article will display many of the more exciting landscapes using HiRISE images. HiRISE images can show detail down to the size of a small kitchen table. With HiRISE we frequently even see spacecraft that have landed on the surface. Many of the scenes shown here are about one would see at the height of a helicopter.
Most of the HiRISE images here were obtained through the HiWish program, a program where anyone could suggest places to be imaged with HiRISE. To obtain the images, I studied wide angle CTX images to find sites that could contain interesting features. I was lucky that many of my suggestions were photographed, and I was able to gather them together for this article.

==Viking 1==

[[File:Mars Viking 11d128.png |thumb|300px|right|Rocks and dunes, as seen from Viking 1 Holes were dug by the digging tool. Part of the meteorology boom is visible. ]]
Viking 1 was the first successful spacecraft to land on Mars. It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E). July 20th was also the date when we first landed on the moon in 1969. 

==Viking 2==

[[File:Viking2lander1.jpg |thumb|300px|left| View from Viking 2 ]]
Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E). 

==Mars Pathfinder==

[[File:Mars pathfinder panorama large.jpg |thumb|300px|right|Wide view from Mars pathfinder, showing Sojourner Rover ]]
The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in [[Ares Vallis]]. 

==Spirit Rover==

The Spirit Rover landed on January 4, 2004 at 14.5684 S and 175.472636 E (184.527364 W).

<gallery class="center" widths="380px" heights="360px">
File:Bonneville crater.jpg|Bonneville crater from Spirit Rover Columbia Hills are in the right in the distance. Spirit eventually drove to the Columbia Hills.
File:Free Spirit.jpg|Wide view with Husband Hill in the distance to which Spirit eventually drove to. Solar panels are visible.
File:MER A Spirit Everest L257atc-A622R1 br2.jpg|Wide view from Spirit Rover Solar panels are visible.
</gallery>

==Opportunity Rover==

The Opportunity Rover landed on January 25, 2004 at 1.9462 S and 354.4734 E (5.5268 W).

<gallery class="center" widths="380px" heights="360px">

File:Opportunity Heat Shield.jpg|Wide view from Opportunity showing heat shield to the left and circular impact crater on the right
File:PIA21723-MarsOpportunityRover-PerserveranceValley-20170619.jpg|Wide view of Perserverance Valley taken with Opportunity Rover High points visible on the rim of Endeavour Crater include "Winnemucca" on the left and "Cape Tribulation" on the right. Winnemucca is part of the "Cape Byron" portion of the crater rim. The horizon at far right extends across the floor of Endeavour Crater, which is about 14 miles (22 kilometers) in diameter.
File:PIA19109-MarsOpportunityRover-EndeavourCrater-CapeTribulation-20150122.jpg|Wide view from top of the "Cape Tribulation" segment of the rim of Endeavour Crater.
</gallery>

==Phoenix==

[[File:PIA13804-MarsPhoenixLander-Panorama-20080525b.jpg |thumb|300px|left|Wide view from Phoenix lander Solar panels are visible.]]
Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis. 

==Curiosity Rover==
[[File:673885main PIA15986-full full.jpg |thumb|300px|right|Early view from Curiosity Mount Sharp is in the distance. The shadow of Rover is visible. Mount Sharp at a height of about 3.4 miles is taller than Mt. Whitney in California.]]
The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W). By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting. 

<gallery class="center" widths="380px" heights="360px">

File:7623 mars-slip-face-downwind-sand-dune-namib-sol1196-pia20281-full2.jpg|Slip Face on Downwind Side of 'Namib' Sand Dune on Mars, as seen by Curiosity Dune stands about 13 feet (4 meters) high. Picture taken with Navcam.

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg|View from the "Kimberley" formation on Mars taken by NASA's Curiosity rover.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp Location is within the "Murray Buttes" region on lower Mount Sharp.

File:PIA23346 hireslayerscuriosity.jpg|360-degree panorama of a location called "Teal Ridge"

File:PIA23347 hireslayersclose.jpg|Close view of layers of ancient sediment on a boulder-sized rock called "Strathdon," as seen by the Mars Hand Lens Imager (MAHLI) camera on the end of the robotic arm on NASA's Curiosity rover.
</gallery>

What follows are a few pictures of the many different scenes that we have studied with powerful cameras on board the Mars Reconnaissance Orbiter that has been going around Mars for over 10 years.

==Dunes==

The Martian surface displays many beautiful dark dunes. For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds
How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.

The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars. However, we must remember that its atmosphere is only about 1 % as dense as the Earth's. Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).<ref> https://www.space.com/30663-the-martian-dust-storms-a-breeze.html</ref>

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

<gallery class="center" widths="380px" heights="360px">

File:61974 1710dunesrgb2.jpg|Dunes processed in the rgb color system
File:ESP 044861 2225dunes.jpg|Wide view of dune field in Ismenius Lacus quadrangle
File:ESP 043821 2555dryice.jpg|Defrosting dunes in Mare Boreum quadrangle
File:ESP 043821 2555dryicecolor.jpg|Color view of dunes defrosting Ice is in the toughs of the polygons.
File:ESP 046378 1415dunefield.jpg|Wide view of dune field
File:46378 1415dunesirb.jpg|Close view of dunes
File:46378 1415dunesirb2.jpg|Close view of dunes
File:PSP 010277 1650fallingdunes.croppedjpg.jpg|Falling dunes These “falling dunes” are a type of topographically-controlled sand dune that formed when down-slope winds were focused by local topography. The dunes point to the lowest areas--in this photo that is toward the top.

</gallery>

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Layers==

Many places on Mars show rocks arranged in layers. Volcanoes, wind, or water can produce layers.<ref>url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 </ref> Layers can be hardened by the action of groundwater.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater in Oxia Palus quadrangle, as seen by HiRISE under [[HiWish program]]

<gallery class="center" widths="380px" heights="360px">

File:Wikiesp 035896 1845crommelinbutte.jpg|thumb|300px|left|Layers in Crommelin Crater
File:544858 1885topcloselayers5.jpg|thumb|300px|center|Layers in Danielson Crater in Oxia Palus quadrangle
File:60331 1880layersclosecolor.jpg|thumb|right|300px|Color image of layers on the floor of Danielson Crater taken under the HiWish program
</gallery>
[[File:60331 1880widelayersdark.jpg|600pxr|Layers on the floor of Danielson Crater taken under the [[HiWish program]] Box shows size of a football field.]]

==Glaciers==

There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. A few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>

Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.<ref>Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127</ref> <ref>Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128</ref> <ref>Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671</ref> <ref>Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33</ref> Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> Lineated valley fill (LVF) are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines may have developed as other glaciers moved down valleys. Some of these glaciers seem to come from material sitting around mesas and buttes.<ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> Lobate debris aprons (LDA) is the name given to these glaciers. All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.<ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 050176 2245glacier.jpg|Glacier leaving a valley in the Ismenius Lacus quadrangle
File:Hollows as seen by hirise under hiwish program.jpg|Concentric crater fill The concentric lines are formed from ice moving away from the crater walls. This crater is mostly full of ice.

Concentric Crater Fill Wide-view.jpg|Wide view of concentric crater fill in crater in Casius quadrangle
</gallery>

[[File:Wikildaf03 036777 2287.jpg|thumb|300px|center|Mesa with Lobate Debris Aprons (LDA) Orbiting radars have detected ice in LDA’s under a thin cover of debris.]]

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

[[File:ESP 045085 2205flowlabeled.jpg|thumb|300px|center|Labeled view of Lineated Valley Flow and glacier]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 046840 2130lvf.jpg|Lineated Valley Flow in valley
File:53630 2195lvf.jpg|Lineated Valley Flow, as seen by HiRISE under the HiWish program

</gallery>

==Gullies==

[[Martian gullies]] are networks of narrow channels and their associated downslope deposits, found on steep slopes. A high concentration occurs near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref name="Malin, M. 2000">Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. They were believed to be caused by recent running water, but with more observations other ideas emerged. In summary of our present understanding of gullies it can be said: A number of studies have demonstrated that gullies are being modified on present day Mars. <ref>C.M. Dundas, A.S. McEwen, S. Diniega, C.J. Hansen, S. Byrne, J.N. McElwaine. The formation of gullies on Mars today. Geol. Soc. London Spec. Publ., 467 (2019), pp. 67-94, 10.1144/SP467.5</ref> <ref>C.M. Dundas, S. Diniega, C.J. Hansen, S. Byrne, A.S. McEwen. Seasonal activity and morphological changes in Martian gullies. Icarus, 220 (2012), pp. 124-143, 10.1016/j.icarus.2012.04.005 </ref> <ref>.M. Dundas, S. Diniega, A.S. McEwen. Long-term monitoring of Martian gully formation and evolution with MRO/HiRISE. Icarus, 251 (2015), pp. 244-263, 10.1016/j.icarus.2014.05.013</ref> <ref>J. Raack, S.J. Conway, T. Heyer, V.T. Bickel, M. Philippe, H. Hiesinger, A. Johnsson, M. Massé. Present-day gully activity in Sisyphi Cavi, Mars - flow-like features and block movements. Icarus, 350 (2020), 10.1016/j.icarus.2020.113899. article #113899</Ref> Today, liquid water cannot exist on the Red planet because the both the pressure and the temperature are too low. Researchers have proposed other mechanisms that could account for gully formation without liquid water.<ref>S.J. Conway, T. de Haas, T.N. Harrison. Martian gullies: a comprehensive review of observations, mechanisms and insights from Earth analogues. Geol. Soc. London Spec. Publ., 467 (2019), pp. 7-66, 10.1144/SP467.14</ref> Most involve dry ice (solid carbon dioxide) accumulating during cold seasons and then changing to a gas in the spring. The gas coming off could start material moving down slopes. The gas mixed with sand and other debris could act like water to erode channels. Also, pieces of dry ice could easily side down due to the lubricating effect of gas coming off the dry ice. However, one wonders if these processes could account for the formation of all the gullies. Maybe, liquid water was sometimes necessary, especially to move large boulders. A study of over 700 sites, published in 2022 in Icarus, concluded that liquid water would not have been needed. During the duration of the study many large boulders were moved—one being 5 meters across. Many types of changes were seen in gullies. Some channels were extended, new channels were formed, and other channels were filled with new debris.<ref> Dundas, C., et al. 2022. Martian gully activity and the gully sediment transport system. Icarus. (in press) </ref> <ref>https://www.sciencedirect.com/science/article/pii/S0019103522002408#bb0145</ref> Perhaps, some water was involved in the past, but all the gullies seen today could have been made without water.

<gallery class="center" widths="380px" heights="360px">
File:ESP 039621 1315gullies.jpg|Gullies with alcove, channel, and apron labeled
File:47395 1415gullycurvedchannels.jpg|Gullies in Argyre quadrangle Curved channels were thought to need running water to form.

File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program
File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>
</gallery>

==Channels==

There are thousands of channels that were probably caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref>

<gallery class="center" widths="380px" heights="360px">
WikiESP 033729 1410stream.jpg|Small branched channel
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel These were shaped by running water.<ref>https://www.uahirise.org/ESP_045833_1845</ref>
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.
</gallery>

== Inverted relief ==

Some places on Mars show inverted relief. In these locations, a stream bed may be a raised feature, instead of a valley. Inverted former stream channels may be caused by the deposition of large rocks, cementation, or maybe by lava moving down the channel. In either case later erosion would erode the surrounding land and leave the old channel as a raised ridge because the ridge would be more resistant to erosion. The image below, taken with HiRISE show curved ridges that are old channels that have become inverted. They have the shape of streams but are above ground.<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_002279_1735</ref>

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Possible inverted streams, as seen by HiRISE under HiWish program]]

[[File:ESP 077583 2255inverted.jpg|thumb|500px|center|Inverted stream, a stream bed has been filled with hard materials that did not erode away like the surroundings]]

==Troughs==

The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="380px" heights="360px">
File:Troughs in Elysium Planitia.jpg|Troughs in the Elysium Planitia
File:ESP 051781 2035troughs.jpg|Troughs in Amenthes quadrangle
File:WikiESP 034541 2065pitstroughstharsis.jpg|Pits and troughs Troughs seem to start with lines of pits. Layers and dark slope streaks are also visible.

File:56910 2100trough.jpg|Troughs in the Cebrenia quadrangle, as seen by HiRISE under HiWish program
</gallery>

==Craters==

Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. So, impact craters are a major surface feature. There is a rich variety of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref> We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref> <ref>https://www.sciencedirect.com/science/article/abs/pii/S0019103513001693?via%3Dihub</ref> <ref>Daubar, I., et al. 2013. The current martian cratering rate. Icarus. Volume 225. 506-516. </ref>

[[File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
|600pxr|Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.]]

Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.

File:26079secondaries.jpg|Group of secondary craters These are formed from material that is blasted way up in the air from the impact.<ref>https://www.uahirise.org/hipod/ESP_046876_1465</ref>

File:ESP 046876 1465secondarycraters.jpg|Group of secondary craters They are small and the same age. They formed from material that was blasted way up in the air from an impact.

File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.

File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.

File:48131 2055pitsforming.jpg|Close view of pits on floor of crater A box shows the size of a football field. Note: This is an enlargement of the previous image of a crater.

File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>
File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.

File:ESP 052260 2165ringmold.jpg|Wide view of ring-mold crater on the floor of a larger crater

File:52260 2165ringmoldclose.jpg|Close view of ring-mold craters (indicated with arrows) Surface between the ring-mold craters is covered with brain terrain.

File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet. To see before and after photos of a new impact go to https://static.uahirise.org/images/2020/details/cut/ESP_062948_2175.gif

File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.

File:ESP 037528 2350pedestal.jpg|Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.

File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.

File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

</gallery>
Scientists love to study central peaks of craters because they contain samples of material from deep under a surface. Durning an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE Colors show different minerals--some used to be deep underground.

</gallery>

==Scalloped Terrain==

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region of Utopia Planitia.<ref> Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 |</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>http://www.uahirise.org/ESP_038821_1235</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Dundas, C., et al. 2015. Modeling the development of martian sublimation thermokarst landforms. Icarus: 262, 154-169.</ref> Scalloped topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.<ref name="Dundas, C. 2015">Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

<gallery class="center" widths="380px" heights="360px">
File:46916 2270scallopsmerging.jpg|Scalloped terrain in Casius quadrangle
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle
File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia
</gallery>
 

==Brain Terrain==

Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle Closed-cell brain terrain may still contain an ice core.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ribbed terrain==

Ribbed terrain forms as ice leaves the ground along cracks in a process called "
[[sublimation]]." Much of the ground is ice so that when the ice disappears the ground collapses.<ref>https://en.wikipedia.org/wiki/Upper_Plains_Unit</ref>

[[File:ESP 047499 2245ribswide.jpg |Wide view of ribbed terrain in Ismenius Lacus quadrangle
|600pxr|Wide view of ribbed terrain in Ismenius Lacus quadrangle]]

[[File:62002 1470ribbed.jpg|thumb|300px|left|Ribbed terrain]]

[[File:62002 1470ribbedclose2.jpg|thumb|300px|center|Ribbed terrain The box is the size of a football field]]

==Linear Ridge Networks==

[[File:46269 1770ridgesmesa.jpg|Close view of ridge network, as seen by HiRISE under HiWish program
|600pxr|Close view of ridge network, as seen by HiRISE under HiWish program]]

Close view of ridge network, as seen by HiRISE under HiWish program

This terrain appears over much of the planet. However, there is a heavy concentration of these features, also called irregular polygonal ridge networks, in the Nili Fossae region.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868.</ref> These networks consist of groups of narrow ridges that often meet at close to right angles. We are not sure of how it originated.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>
They may have been caused by fluids moving into cracks that were created by impacts. The fluids then became hard and erosion resistant.<ref>Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref> <ref>Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276.</ref> <ref>Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.</ref> <ref>Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus: 281, 200-219.</ref> <ref>E. K. Ebinger E., J. Mustard. 2015. LINEAR RIDGES IN THE NILOSYRTIS REGION OF MARS: IMPLICATIONS FOR SUBSURFACE FLUID FLOW. 46th Lunar and Planetary Science Conference (2015) 2034.pdf</ref> <ref>Saper, L., J. Mustard. 2013. Extensive linear ridge networks in Nili Fossae and Nilosyrtis, Mars: implications for fluid flow in the ancient crust. Geophysical Research letters: 40, 245-249.</ref> <ref>Kerber L., Schwamb M., Portyankina G. Hansen C. J. Aye K.-M. Global Polygonal Ridge Networks: Evidence for Pervasive Noachian Crustal Groundwater Circulation [#2972]. pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2972.pdf49th</ref> We are not totally sure of the exact ways these ridges were created. Over 14,000 people from around the world helped map them, so that scientists could better understand them. Some ridges contain clays, so water may have been involved in their formation because clays need water to form.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al. 2022. Irregular polygonal ridge networks in ancient Noachian terrain on Mars. Icarus. 374. 114833</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle
File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

File:46269 1770ridges2.jpg|Close view of ridge network
</gallery>

==Yardangs==

Yardangs form from fine-grained material. They are shaped by the wind and show the direction of the prevailing winds. Much of this fine-grained material probably has its origin in the many large volcanoes on the planet. Yardangs are especially common in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because they exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs3.jpg|Yardangs
File:35558 1830yardangs.jpg|Yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs in Amazonis quadrangle

</gallery>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface; consequently exposing a dark layer.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> The dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

Dust devils are common.<ref>https://www.uahirise.org/ESP_042201_1715</ref> In the first 216 Martian days (Sols), the Perseverance Rover in Jezero Crater found that at least four dust devils passed Perseverance on a typical Martian day and that more than one per hour passes by during a peak hourlong period just after noon.<ref>https://www.jpl.nasa.gov/news/nasas-perseverance-studies-the-wild-winds-of-jezero-crater?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Day%20in%20Review%20-%206-1-22</ref>
<ref>https://www.science.org/doi/10.1126/sciadv.abn3783</ref> <ref> Newman, C., et al. 2022. The dynamic atmospheric and aeolian environment of Jezero crater, Mars. Science Advances. Vol. 8. Number 21</ref>

[[Image:dust_devils.gif|thumb|right|300px|Dust devils photographed by Mars Rover Spirit]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.

File:ESP 061787 2140devilcropped.jpg
</gallery>

==Dark Slope Streaks==

Dark slope streaks are avalanche-like features common on dust-covered slopes, especially in the equatorial regions.<ref name=Chuang10>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

Dry ice accumulates just under the surface during cold Martian nights and then changes to a gas in the morning. That gas creates enough wind to disturb dust particles and send them down steep slopes. As the bright dust slides down it reveals the underlying dark volcanic rocks. This process was discovered by measuring temperatures in the area. At the recorded temperatures, carbon dioxide from the air should have frozen on the surface, but it was not visible. It was concluded that the dry ice was forming just under the surface rather than on top..<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al. 2022. Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks. JGR Planets. Volume127, Issue4. e2021JE006988</ref>

<gallery class="center" widths="380px" heights="360px">
File: ESP 045435 2055troughlayers.jpg | Dark slope streaks in trough Layers are also visible in the image.
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks
File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact
</gallery>

==Lava==

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Lava flows can also move around an create what appear to be layers, especially if it fluid like water. Basalt flows can often be that way.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 044840 1620lavaflow.jpg|Lava flows in Phoenicis Lacus quadrangle
File:45133 1970lvarafts.jpg|Rafts of lava in Amazonis quadrangle
File:45384 2065cones.jpg|”Rootless cones” caused by lava flowing over ice-rich ground in Elysium quadrangle
</gallery>

==Mud Volcanoes==

Mud volcanoes are very common in the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Being underground the mud was protected from radiation on the surface. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

[[File:52050 2200mudvolcanoes.jpg |thumb|300px|left| Mud volcanoes in Mare Acidalium quadrangle]]

[[File:61584 2300mudvolcano.jpg|thumb|300px|right|Close view of mud volcano, as seen by HiRISE]]

[[File:53381 2265mud.jpg|thumb|300px|center|Mud volcanoes]]

==Rootless cones==

Rootless Cones are believed to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam which blows out a ring or cone. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form.

[[File:Wikiesp37643 2060cones.jpg|thumb|300px|right|Rootless cones formed when lava flowed over ice or ice-rich ground. The sharp bend in the line of cones may have been caused by the lava changing direction.]]

[[File:58610 2100cones.jpg|thumb|300px|left|Close view of rootless cones, as seen by HiRISE under the HiWish program]]

[[File:58610 2100coneswakeslabeled.jpg|300px|center|Close view of rootless cones showing wakes caused by lava moving]]

[[File:ESP 045384 2065lavaice.jpg|thumb|300px|center|Wide view of field of rootless cones in Elysium quadrangle]]

==Honeycomb Terrain==

[[File: ESP_049330_1425honeycomb.jpg|thumb|300px|right|Honeycomb terrain in Hellas quadrangle]]

Honeycomb terrain is found on parts of the floor of Hellas Planitia. It may be due to rising bodies of ice followed by erosion.<ref>Bernhardt, H.; et al. (2016). "The honeycomb terrain on the Hellas basin floor, mars: a case for salt or ice diapirism: hellas honeycombs as salt/ice diapirs". J. Geophys. Res. 121: 714–738.</ref> <ref>Weiss, D., J. Head. 2017. HYDROLOGY OF THE HELLAS BASIN AND THE EARLY MARS CLIMATE: WAS THE HONEYCOMB TERRAIN FORMED BY SALT OR ICE DIAPIRISM? Lunar and Planetary Science XLVIII. 1060.pdf</ref> <ref>Weiss, D.; Head, J. (2017). "Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate". Icarus. 284: 249–263.</ref>

 
==Fractured Surface and Blocks==

[[File:44757 2185closeleft.jpg |thumb|300px|left| Rock breaking up into cube-shaped blocks]]
In many places on Mars bedrock breaks up into large blocks. Sometimes the blocks form what look like perfect cubes. Although one may think these shapes had to be made by intelligent aliens, this is a natural process. The salt you put on your food also breaks up into cubes. Check your salt out with a magnifying glass.

 
==Fractured Ground==

Some places on Mars break up with large fractures that create a terrain with mesas and valleys. Some of these can be quite pretty.

<gallery class="center" widths="380px" heights="360px">
File:ESP 048878 2095fractures.jpg|Wide view of fractured ground
File:48878 2095fractures.jpg|Close view of fractured ground
</gallery>

==Dipping layers==

Groups of layers that are tilted are common in some areas of Mars. They represent material that once covered a wide area.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288</ref> The layers may be related to changes in the climate in the past. They may have been shaped by the wind.

<gallery class="center" widths="380px" heights="360px">
File:ESP 050793 1365pyramids.jpg| Wide view of layered features in Hellas quadrangle
File:50793 1365layers2.jpg|Close view of layered features in Hellas quadrangle Each layer may represent a change in the climate.
File:ESP 035801 2210pyramidsismenius.jpg|Tilted layers in Ismenius Lacus These sets of layers can often be seen leaning against slopes.
</gallery>

==Boulders==

Much of the surface of Mars is covered with hard, basalt volcanic rock. When the rock breaks down it often forms large boulders the size of houses.

<gallery class="center" widths="380px" heights="360px">
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas in Elysium quadrangle Box shows size of football field.
File:ESP 045415 2220boulders.jpg|Color view of boulders
File:45575 2535dunebouldertracks.jpg| Close view of dunes showing boulders with arrows If you click on image to enlarge, you can see the tracks left by the boulders as they traveled down the dune.
45575 2535duneboulders.jpg|Boulder and boulder tracks, as seen by HiRISE under HiWish program The arrow shows a boulder that has made a track in the sand as it rolled down dune.
45575 2535dunebouldertracks.jpg|Boulders and tracks, as seen by HiRISE under HiWish program The arrows show a boulders that have produced a track by rolling down dune.

</gallery>

==Hollows==

Some places on Mars have surfaces that are covered with hollows. Sometimes they form large holes, sometimes curved canyons. They can be pretty and would be fun to explore on foot in the future. This terrain may have developed from what has been called ribbed terrain. Either way, these scenes were caused as ice left the ground.

<gallery class="center" widths="380px" heights="360px">
File:ESP 043688 2245hollows.jpg|Wide view of hollows in ground, probably from ice leaving the ground
File:ESP 043688 2245closecolor.jpg|Close color view of hollows in ground, probably from ice leaving the ground
File:ESP 026042 1470hollows.jpg| Hollows in ground, probably from ice leaving the ground Location is Hellas Montes Region.
</gallery>

==Mesas==

Many, large areas of Mars have eroded such that there are many mesas. Some show layers. Mesas show how the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="380px" heights="360px">
File:47441 1800mesaclose.jpg|Mesa with box showing size of football field
File:47421 1890bigbutte.jpg|Layered mesa with box showing size of football field
File:46050 1775race.jpg|Mesa that is 14 km or 8.7 miles around the outside
</gallery>

==Landslides==

Mars shows various mass movements like landslides. There are many steep slopes for material to move down, especially in craters and canyons.

<gallery class="center" widths="380px" heights="360px">
File:ESP 043963 1550landslide.jpg|Landslide
File:ESP 045981 1585landslide.jpg|Landslide

File:ESP 057191 2150landslidecropped.jpg|Landslide
</gallery>

==Latitude Dependent Mantle==

Latitude Dependent Mantle is very common in certain latitudes.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It often appears as a smooth covering. A certain percentage of it consists of ice. It may be a major source of water for future colonists because it has a widespread distribution. Sometimes mantle displays layers because it was deposited at different times.

<gallery class="center" widths="380px" heights="360px">
File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program
File:2509mantlelayers.jpg|Mantle layers with layers
</gallery>

==Exhumed craters==

Exhumed craters seem to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> <ref> https://www.uahirise.org/PSP_001374_1805</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters, as seen by HiRISE under HiWish program

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
</gallery>

==Swiss Cheese Terrain==

Parts of Mare Australe show pits that make the surface look like Swiss cheese.<ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap. These circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.<ref> Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

<gallery class="center" widths="380px" heights="360px">
File:South Pole Terrain.jpg|Swiss Cheese Terrain near South Pole, as seen by HiRISE
File:ESP 058515 0955closechanges.jpg|Changes in Swiss Cheese Terrain from August 2009 to January 2019
</gallery>

<gallery class="center" widths="500px">
File:ESP 014274 0955southpole3.jpg|wiss Cheese Terrain August 2009
File:ESP 058515 0955southpole2.jpg|Swiss Cheese Terrain January 2019
</gallery>

==Ice Cap Layers==

The northern ice cap of Mars displays many layers of ice that accumulated when the climate changed. These are visible when there is a canyon in the ice. The climate of Mars changes greatly due to the large changes in the tilt of Mars. Mars does not have a large moon to stabilize its' tilt.

<gallery class="center" widths="380px" heights="360px">

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019.

File:69629 2605npolarlayerswide.jpg|Layers in northern ice cap
</gallery>

==Spiders==

The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> This results in the appearance of dark plumes that are often blown in one direction by local winds. This dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> This process was demonstrated in laboratory simulations involving slabs of dry ice placed on glass spheres of different sizes.<ref>https://www.nature.com/articles/s41598-021-82763-7.pdf</ref> <ref>McKeown, L., et al. 2021. The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric
pressure. Scientific Reports.</ref> <ref>https://www.livescience.com/spiders-on-mars-explained-dry-ice.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref>

<gallery class="center" widths="380px" heights="360px">
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
File:Spidersmarspedia.jpg|Close view of spiders
</gallery>

==Polygonal Patterned Ground==

Many surfaces on Mars display “polygonal patterned ground.” The polygons can be of different shapes and sizes. They are believed to be caused by ice in the ground.<ref>https://www.uahirise.org/ESP_047247_1150</ref> Like permafrost regions on Earth, this permanently frozen water is still active.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction. Over long periods of cyclic cracking, a honeycomb-like polygonal pattern arises.<ref>https://www.uahirise.org/ESP_066782_1110</ref>

The patterns formed may yet be another marker for underground ice that could be used by future colonists. Before we land crews on Mars, we may very well have detailed maps for where the colonists can obtain water.

<gallery class="center" widths="380px" heights="360px">
File:ESP 049660 1200polygonswide.jpg|Wide view of large and small polygons

File:ESP 049660 1200polygonsclosecolor.jpg|Close, color view of polygons Note: this is an enlargement of the previous wide view image.
File:45070 1440polygonscloseshadows.jpg|High center polygons
</gallery>

<gallery class="center" widths="380px" heights="360px">
File:56148 1145polygonswide.jpg|Wide view of crater floor that is covered with polygons Low places still contain frost. Image taken with HiRISE under HiWish program.

File:56148 1145polygonsclose.jpg|Enlarged view of polygons from previous image. Dark line is a defect in processing.
File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons from a previous image that shows polygons of varying sizes. Dark lines are defects in processing.
</gallery>

==Notes about pictures==

Most pictures from spacecraft have some sort of enhancement. For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red.<ref> https://repository.si.edu/bitstream/handle/10088/19366/nasm_201048.pdf?sequence=1&isAllowed=y</ref> <ref>Delamere, W., et al. 2010. Color imaging of Mars by the High Resolution Imaging Science Experiment (HiRISE). Icarus. 205 pp. 38–52</ref> Displaying colors in this way allows us to better identify rocks and minerals.
HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 025698 1485pinksalt.jpg|HiRISE image with pink color representing chloride salt.
</gallery>

[[File:60331 1880widecolorband.jpg|Wide view of layers in Danielson Crater The center band is in color|600pxr|Wide view of layers in Danielson Crater The center band is in color.]]
Wide view of layers in Danielson Crater The center band is in color.

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Dust devils]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[How living on Mars will be different than living on Earth]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]
*[[Water]]

==Further reading==

* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

== External links ==

*[https://www.uahirise.org/PSP_007820_1505 Layered Sediments in Hellas Planitia]

*[https://www.uahirise.org/PSP_005383_1255 Changes in dust devil tracks]

*[https://static.uahirise.org/images/2020/details/cut/ESP_062948_2175.gif before and after pictures of a new impact]

*[https://static.uahirise.org/images/2020/details/cut/ESP_063204_1800.gif Looking for Slope Streaks-old and new pictures of streaks]]

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground
* [https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

* [https://www.youtube.com/user/MARS3DdotCOM Flying around Candor Chasma at an altitude of 100 meters]

* [https://www.youtube.com/watch?v=Q-2B8J2OU8o Flight over Mars using HiRISE images--very beautiful]

* [https://www.youtube.com/watch?v=mBuvVM_e4G0 HiRISE images of polar regions with narriation]

* [https://www.youtube.com/watch?v=uZ5Y8Qc_dZU&index=2&list=PL2gLpWRK0QlAqGDSlMKS4BaJVbwzEl_0g HiRISE images of beautiful scenes]

* [https://www.youtube.com/watch?v=YIoVtsVsx0Y Flyover of many parts of Mars using HiRISE images--Very nice]

* [https://www.youtube.com/watch?v=siIoqdPG3U4 Pictures from HiRISE and from Curiosity ]

[[category:Areomorphology]]

File:ESP 077583 2255inverted.jpg

2023-04-17T22:11:49Z

Suitupandshowup: Inverted stream as seen by HiRISE under the HiWish program Image credit: NASA/JPL/University of Arizona/Secosky Source: https://www.uahirise.org/ESP_077583_2255

== Summary ==
Inverted stream as seen by HiRISE under the HiWish program

Image credit: NASA/JPL/University of Arizona/Secosky
Source: https://www.uahirise.org/ESP_077583_2255
== Licensing ==
{{PD}}

What Mars Actually Looks Like!

2023-04-17T22:09:18Z

Suitupandshowup: /* Inverted relief */

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Almost all of the sites that we have landed on Mars with spacecraft have been to the most drab and boring places on the planet. This was done to ensure a safe landing. This article will display many of the more exciting landscapes using HiRISE images. HiRISE images can show detail down to the size of a small kitchen table. With HiRISE we frequently even see spacecraft that have landed on the surface. Many of the scenes shown here are about one would see at the height of a helicopter.
Most of the HiRISE images here were obtained through the HiWish program, a program where anyone could suggest places to be imaged with HiRISE. To obtain the images, I studied wide angle CTX images to find sites that could contain interesting features. I was lucky that many of my suggestions were photographed, and I was able to gather them together for this article.

==Viking 1==

[[File:Mars Viking 11d128.png |thumb|300px|right|Rocks and dunes, as seen from Viking 1 Holes were dug by the digging tool. Part of the meteorology boom is visible. ]]
Viking 1 was the first successful spacecraft to land on Mars. It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E). July 20th was also the date when we first landed on the moon in 1969. 

==Viking 2==

[[File:Viking2lander1.jpg |thumb|300px|left| View from Viking 2 ]]
Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E). 

==Mars Pathfinder==

[[File:Mars pathfinder panorama large.jpg |thumb|300px|right|Wide view from Mars pathfinder, showing Sojourner Rover ]]
The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in [[Ares Vallis]]. 

==Spirit Rover==

The Spirit Rover landed on January 4, 2004 at 14.5684 S and 175.472636 E (184.527364 W).

<gallery class="center" widths="380px" heights="360px">
File:Bonneville crater.jpg|Bonneville crater from Spirit Rover Columbia Hills are in the right in the distance. Spirit eventually drove to the Columbia Hills.
File:Free Spirit.jpg|Wide view with Husband Hill in the distance to which Spirit eventually drove to. Solar panels are visible.
File:MER A Spirit Everest L257atc-A622R1 br2.jpg|Wide view from Spirit Rover Solar panels are visible.
</gallery>

==Opportunity Rover==

The Opportunity Rover landed on January 25, 2004 at 1.9462 S and 354.4734 E (5.5268 W).

<gallery class="center" widths="380px" heights="360px">

File:Opportunity Heat Shield.jpg|Wide view from Opportunity showing heat shield to the left and circular impact crater on the right
File:PIA21723-MarsOpportunityRover-PerserveranceValley-20170619.jpg|Wide view of Perserverance Valley taken with Opportunity Rover High points visible on the rim of Endeavour Crater include "Winnemucca" on the left and "Cape Tribulation" on the right. Winnemucca is part of the "Cape Byron" portion of the crater rim. The horizon at far right extends across the floor of Endeavour Crater, which is about 14 miles (22 kilometers) in diameter.
File:PIA19109-MarsOpportunityRover-EndeavourCrater-CapeTribulation-20150122.jpg|Wide view from top of the "Cape Tribulation" segment of the rim of Endeavour Crater.
</gallery>

==Phoenix==

[[File:PIA13804-MarsPhoenixLander-Panorama-20080525b.jpg |thumb|300px|left|Wide view from Phoenix lander Solar panels are visible.]]
Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis. 

==Curiosity Rover==
[[File:673885main PIA15986-full full.jpg |thumb|300px|right|Early view from Curiosity Mount Sharp is in the distance. The shadow of Rover is visible. Mount Sharp at a height of about 3.4 miles is taller than Mt. Whitney in California.]]
The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W). By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting. 

<gallery class="center" widths="380px" heights="360px">

File:7623 mars-slip-face-downwind-sand-dune-namib-sol1196-pia20281-full2.jpg|Slip Face on Downwind Side of 'Namib' Sand Dune on Mars, as seen by Curiosity Dune stands about 13 feet (4 meters) high. Picture taken with Navcam.

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg|View from the "Kimberley" formation on Mars taken by NASA's Curiosity rover.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp Location is within the "Murray Buttes" region on lower Mount Sharp.

File:PIA23346 hireslayerscuriosity.jpg|360-degree panorama of a location called "Teal Ridge"

File:PIA23347 hireslayersclose.jpg|Close view of layers of ancient sediment on a boulder-sized rock called "Strathdon," as seen by the Mars Hand Lens Imager (MAHLI) camera on the end of the robotic arm on NASA's Curiosity rover.
</gallery>

What follows are a few pictures of the many different scenes that we have studied with powerful cameras on board the Mars Reconnaissance Orbiter that has been going around Mars for over 10 years.

==Dunes==

The Martian surface displays many beautiful dark dunes. For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds
How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.

The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars. However, we must remember that its atmosphere is only about 1 % as dense as the Earth's. Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).<ref> https://www.space.com/30663-the-martian-dust-storms-a-breeze.html</ref>

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

<gallery class="center" widths="380px" heights="360px">

File:61974 1710dunesrgb2.jpg|Dunes processed in the rgb color system
File:ESP 044861 2225dunes.jpg|Wide view of dune field in Ismenius Lacus quadrangle
File:ESP 043821 2555dryice.jpg|Defrosting dunes in Mare Boreum quadrangle
File:ESP 043821 2555dryicecolor.jpg|Color view of dunes defrosting Ice is in the toughs of the polygons.
File:ESP 046378 1415dunefield.jpg|Wide view of dune field
File:46378 1415dunesirb.jpg|Close view of dunes
File:46378 1415dunesirb2.jpg|Close view of dunes
File:PSP 010277 1650fallingdunes.croppedjpg.jpg|Falling dunes These “falling dunes” are a type of topographically-controlled sand dune that formed when down-slope winds were focused by local topography. The dunes point to the lowest areas--in this photo that is toward the top.

</gallery>

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Layers==

Many places on Mars show rocks arranged in layers. Volcanoes, wind, or water can produce layers.<ref>url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 </ref> Layers can be hardened by the action of groundwater.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater in Oxia Palus quadrangle, as seen by HiRISE under [[HiWish program]]

<gallery class="center" widths="380px" heights="360px">

File:Wikiesp 035896 1845crommelinbutte.jpg|thumb|300px|left|Layers in Crommelin Crater
File:544858 1885topcloselayers5.jpg|thumb|300px|center|Layers in Danielson Crater in Oxia Palus quadrangle
File:60331 1880layersclosecolor.jpg|thumb|right|300px|Color image of layers on the floor of Danielson Crater taken under the HiWish program
</gallery>
[[File:60331 1880widelayersdark.jpg|600pxr|Layers on the floor of Danielson Crater taken under the [[HiWish program]] Box shows size of a football field.]]

==Glaciers==

There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. A few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>

Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.<ref>Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127</ref> <ref>Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128</ref> <ref>Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671</ref> <ref>Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33</ref> Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> Lineated valley fill (LVF) are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines may have developed as other glaciers moved down valleys. Some of these glaciers seem to come from material sitting around mesas and buttes.<ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> Lobate debris aprons (LDA) is the name given to these glaciers. All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.<ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 050176 2245glacier.jpg|Glacier leaving a valley in the Ismenius Lacus quadrangle
File:Hollows as seen by hirise under hiwish program.jpg|Concentric crater fill The concentric lines are formed from ice moving away from the crater walls. This crater is mostly full of ice.

Concentric Crater Fill Wide-view.jpg|Wide view of concentric crater fill in crater in Casius quadrangle
</gallery>

[[File:Wikildaf03 036777 2287.jpg|thumb|300px|center|Mesa with Lobate Debris Aprons (LDA) Orbiting radars have detected ice in LDA’s under a thin cover of debris.]]

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

[[File:ESP 045085 2205flowlabeled.jpg|thumb|300px|center|Labeled view of Lineated Valley Flow and glacier]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 046840 2130lvf.jpg|Lineated Valley Flow in valley
File:53630 2195lvf.jpg|Lineated Valley Flow, as seen by HiRISE under the HiWish program

</gallery>

==Gullies==

[[Martian gullies]] are networks of narrow channels and their associated downslope deposits, found on steep slopes. A high concentration occurs near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref name="Malin, M. 2000">Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. They were believed to be caused by recent running water, but with more observations other ideas emerged. In summary of our present understanding of gullies it can be said: A number of studies have demonstrated that gullies are being modified on present day Mars. <ref>C.M. Dundas, A.S. McEwen, S. Diniega, C.J. Hansen, S. Byrne, J.N. McElwaine. The formation of gullies on Mars today. Geol. Soc. London Spec. Publ., 467 (2019), pp. 67-94, 10.1144/SP467.5</ref> <ref>C.M. Dundas, S. Diniega, C.J. Hansen, S. Byrne, A.S. McEwen. Seasonal activity and morphological changes in Martian gullies. Icarus, 220 (2012), pp. 124-143, 10.1016/j.icarus.2012.04.005 </ref> <ref>.M. Dundas, S. Diniega, A.S. McEwen. Long-term monitoring of Martian gully formation and evolution with MRO/HiRISE. Icarus, 251 (2015), pp. 244-263, 10.1016/j.icarus.2014.05.013</ref> <ref>J. Raack, S.J. Conway, T. Heyer, V.T. Bickel, M. Philippe, H. Hiesinger, A. Johnsson, M. Massé. Present-day gully activity in Sisyphi Cavi, Mars - flow-like features and block movements. Icarus, 350 (2020), 10.1016/j.icarus.2020.113899. article #113899</Ref> Today, liquid water cannot exist on the Red planet because the both the pressure and the temperature are too low. Researchers have proposed other mechanisms that could account for gully formation without liquid water.<ref>S.J. Conway, T. de Haas, T.N. Harrison. Martian gullies: a comprehensive review of observations, mechanisms and insights from Earth analogues. Geol. Soc. London Spec. Publ., 467 (2019), pp. 7-66, 10.1144/SP467.14</ref> Most involve dry ice (solid carbon dioxide) accumulating during cold seasons and then changing to a gas in the spring. The gas coming off could start material moving down slopes. The gas mixed with sand and other debris could act like water to erode channels. Also, pieces of dry ice could easily side down due to the lubricating effect of gas coming off the dry ice. However, one wonders if these processes could account for the formation of all the gullies. Maybe, liquid water was sometimes necessary, especially to move large boulders. A study of over 700 sites, published in 2022 in Icarus, concluded that liquid water would not have been needed. During the duration of the study many large boulders were moved—one being 5 meters across. Many types of changes were seen in gullies. Some channels were extended, new channels were formed, and other channels were filled with new debris.<ref> Dundas, C., et al. 2022. Martian gully activity and the gully sediment transport system. Icarus. (in press) </ref> <ref>https://www.sciencedirect.com/science/article/pii/S0019103522002408#bb0145</ref> Perhaps, some water was involved in the past, but all the gullies seen today could have been made without water.

<gallery class="center" widths="380px" heights="360px">
File:ESP 039621 1315gullies.jpg|Gullies with alcove, channel, and apron labeled
File:47395 1415gullycurvedchannels.jpg|Gullies in Argyre quadrangle Curved channels were thought to need running water to form.

File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program
File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>
</gallery>

==Channels==

There are thousands of channels that were probably caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref>

<gallery class="center" widths="380px" heights="360px">
WikiESP 033729 1410stream.jpg|Small branched channel
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel These were shaped by running water.<ref>https://www.uahirise.org/ESP_045833_1845</ref>
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.
</gallery>

== Inverted relief ==

Some places on Mars show inverted relief. In these locations, a stream bed may be a raised feature, instead of a valley. Inverted former stream channels may be caused by the deposition of large rocks, cementation, or maybe by lava moving down the channel. In either case later erosion would erode the surrounding land and leave the old channel as a raised ridge because the ridge would be more resistant to erosion. The image below, taken with HiRISE show curved ridges that are old channels that have become inverted. They have the shape of streams but are above ground.<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_002279_1735</ref>

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Possible inverted streams, as seen by HiRISE under HiWish program]]

==Troughs==

The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="380px" heights="360px">
File:Troughs in Elysium Planitia.jpg|Troughs in the Elysium Planitia
File:ESP 051781 2035troughs.jpg|Troughs in Amenthes quadrangle
File:WikiESP 034541 2065pitstroughstharsis.jpg|Pits and troughs Troughs seem to start with lines of pits. Layers and dark slope streaks are also visible.

File:56910 2100trough.jpg|Troughs in the Cebrenia quadrangle, as seen by HiRISE under HiWish program
</gallery>

==Craters==

Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. So, impact craters are a major surface feature. There is a rich variety of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref> We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref> <ref>https://www.sciencedirect.com/science/article/abs/pii/S0019103513001693?via%3Dihub</ref> <ref>Daubar, I., et al. 2013. The current martian cratering rate. Icarus. Volume 225. 506-516. </ref>

[[File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
|600pxr|Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.]]

Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program The impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.

File:26079secondaries.jpg|Group of secondary craters These are formed from material that is blasted way up in the air from the impact.<ref>https://www.uahirise.org/hipod/ESP_046876_1465</ref>

File:ESP 046876 1465secondarycraters.jpg|Group of secondary craters They are small and the same age. They formed from material that was blasted way up in the air from an impact.

File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.

File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.

File:48131 2055pitsforming.jpg|Close view of pits on floor of crater A box shows the size of a football field. Note: This is an enlargement of the previous image of a crater.

File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>
File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.

File:ESP 052260 2165ringmold.jpg|Wide view of ring-mold crater on the floor of a larger crater

File:52260 2165ringmoldclose.jpg|Close view of ring-mold craters (indicated with arrows) Surface between the ring-mold craters is covered with brain terrain.

File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet. To see before and after photos of a new impact go to https://static.uahirise.org/images/2020/details/cut/ESP_062948_2175.gif

File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.

File:ESP 037528 2350pedestal.jpg|Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.

File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.

File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

</gallery>
Scientists love to study central peaks of craters because they contain samples of material from deep under a surface. Durning an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE Colors show different minerals--some used to be deep underground.

</gallery>

==Scalloped Terrain==

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region of Utopia Planitia.<ref> Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 |</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>http://www.uahirise.org/ESP_038821_1235</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Dundas, C., et al. 2015. Modeling the development of martian sublimation thermokarst landforms. Icarus: 262, 154-169.</ref> Scalloped topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.<ref name="Dundas, C. 2015">Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

<gallery class="center" widths="380px" heights="360px">
File:46916 2270scallopsmerging.jpg|Scalloped terrain in Casius quadrangle
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle
File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia
</gallery>
 

==Brain Terrain==

Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle Closed-cell brain terrain may still contain an ice core.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ribbed terrain==

Ribbed terrain forms as ice leaves the ground along cracks in a process called "
[[sublimation]]." Much of the ground is ice so that when the ice disappears the ground collapses.<ref>https://en.wikipedia.org/wiki/Upper_Plains_Unit</ref>

[[File:ESP 047499 2245ribswide.jpg |Wide view of ribbed terrain in Ismenius Lacus quadrangle
|600pxr|Wide view of ribbed terrain in Ismenius Lacus quadrangle]]

[[File:62002 1470ribbed.jpg|thumb|300px|left|Ribbed terrain]]

[[File:62002 1470ribbedclose2.jpg|thumb|300px|center|Ribbed terrain The box is the size of a football field]]

==Linear Ridge Networks==

[[File:46269 1770ridgesmesa.jpg|Close view of ridge network, as seen by HiRISE under HiWish program
|600pxr|Close view of ridge network, as seen by HiRISE under HiWish program]]

Close view of ridge network, as seen by HiRISE under HiWish program

This terrain appears over much of the planet. However, there is a heavy concentration of these features, also called irregular polygonal ridge networks, in the Nili Fossae region.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868.</ref> These networks consist of groups of narrow ridges that often meet at close to right angles. We are not sure of how it originated.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>
They may have been caused by fluids moving into cracks that were created by impacts. The fluids then became hard and erosion resistant.<ref>Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref> <ref>Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276.</ref> <ref>Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.</ref> <ref>Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus: 281, 200-219.</ref> <ref>E. K. Ebinger E., J. Mustard. 2015. LINEAR RIDGES IN THE NILOSYRTIS REGION OF MARS: IMPLICATIONS FOR SUBSURFACE FLUID FLOW. 46th Lunar and Planetary Science Conference (2015) 2034.pdf</ref> <ref>Saper, L., J. Mustard. 2013. Extensive linear ridge networks in Nili Fossae and Nilosyrtis, Mars: implications for fluid flow in the ancient crust. Geophysical Research letters: 40, 245-249.</ref> <ref>Kerber L., Schwamb M., Portyankina G. Hansen C. J. Aye K.-M. Global Polygonal Ridge Networks: Evidence for Pervasive Noachian Crustal Groundwater Circulation [#2972]. pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2972.pdf49th</ref> We are not totally sure of the exact ways these ridges were created. Over 14,000 people from around the world helped map them, so that scientists could better understand them. Some ridges contain clays, so water may have been involved in their formation because clays need water to form.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al. 2022. Irregular polygonal ridge networks in ancient Noachian terrain on Mars. Icarus. 374. 114833</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle
File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

File:46269 1770ridges2.jpg|Close view of ridge network
</gallery>

==Yardangs==

Yardangs form from fine-grained material. They are shaped by the wind and show the direction of the prevailing winds. Much of this fine-grained material probably has its origin in the many large volcanoes on the planet. Yardangs are especially common in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because they exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs3.jpg|Yardangs
File:35558 1830yardangs.jpg|Yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs in Amazonis quadrangle

</gallery>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface; consequently exposing a dark layer.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> The dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

Dust devils are common.<ref>https://www.uahirise.org/ESP_042201_1715</ref> In the first 216 Martian days (Sols), the Perseverance Rover in Jezero Crater found that at least four dust devils passed Perseverance on a typical Martian day and that more than one per hour passes by during a peak hourlong period just after noon.<ref>https://www.jpl.nasa.gov/news/nasas-perseverance-studies-the-wild-winds-of-jezero-crater?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Day%20in%20Review%20-%206-1-22</ref>
<ref>https://www.science.org/doi/10.1126/sciadv.abn3783</ref> <ref> Newman, C., et al. 2022. The dynamic atmospheric and aeolian environment of Jezero crater, Mars. Science Advances. Vol. 8. Number 21</ref>

[[Image:dust_devils.gif|thumb|right|300px|Dust devils photographed by Mars Rover Spirit]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.

File:ESP 061787 2140devilcropped.jpg
</gallery>

==Dark Slope Streaks==

Dark slope streaks are avalanche-like features common on dust-covered slopes, especially in the equatorial regions.<ref name=Chuang10>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

Dry ice accumulates just under the surface during cold Martian nights and then changes to a gas in the morning. That gas creates enough wind to disturb dust particles and send them down steep slopes. As the bright dust slides down it reveals the underlying dark volcanic rocks. This process was discovered by measuring temperatures in the area. At the recorded temperatures, carbon dioxide from the air should have frozen on the surface, but it was not visible. It was concluded that the dry ice was forming just under the surface rather than on top..<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al. 2022. Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks. JGR Planets. Volume127, Issue4. e2021JE006988</ref>

<gallery class="center" widths="380px" heights="360px">
File: ESP 045435 2055troughlayers.jpg | Dark slope streaks in trough Layers are also visible in the image.
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks
File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact
</gallery>

==Lava==

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Lava flows can also move around an create what appear to be layers, especially if it fluid like water. Basalt flows can often be that way.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 044840 1620lavaflow.jpg|Lava flows in Phoenicis Lacus quadrangle
File:45133 1970lvarafts.jpg|Rafts of lava in Amazonis quadrangle
File:45384 2065cones.jpg|”Rootless cones” caused by lava flowing over ice-rich ground in Elysium quadrangle
</gallery>

==Mud Volcanoes==

Mud volcanoes are very common in the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Being underground the mud was protected from radiation on the surface. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

[[File:52050 2200mudvolcanoes.jpg |thumb|300px|left| Mud volcanoes in Mare Acidalium quadrangle]]

[[File:61584 2300mudvolcano.jpg|thumb|300px|right|Close view of mud volcano, as seen by HiRISE]]

[[File:53381 2265mud.jpg|thumb|300px|center|Mud volcanoes]]

==Rootless cones==

Rootless Cones are believed to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam which blows out a ring or cone. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form.

[[File:Wikiesp37643 2060cones.jpg|thumb|300px|right|Rootless cones formed when lava flowed over ice or ice-rich ground. The sharp bend in the line of cones may have been caused by the lava changing direction.]]

[[File:58610 2100cones.jpg|thumb|300px|left|Close view of rootless cones, as seen by HiRISE under the HiWish program]]

[[File:58610 2100coneswakeslabeled.jpg|300px|center|Close view of rootless cones showing wakes caused by lava moving]]

[[File:ESP 045384 2065lavaice.jpg|thumb|300px|center|Wide view of field of rootless cones in Elysium quadrangle]]

==Honeycomb Terrain==

[[File: ESP_049330_1425honeycomb.jpg|thumb|300px|right|Honeycomb terrain in Hellas quadrangle]]

Honeycomb terrain is found on parts of the floor of Hellas Planitia. It may be due to rising bodies of ice followed by erosion.<ref>Bernhardt, H.; et al. (2016). "The honeycomb terrain on the Hellas basin floor, mars: a case for salt or ice diapirism: hellas honeycombs as salt/ice diapirs". J. Geophys. Res. 121: 714–738.</ref> <ref>Weiss, D., J. Head. 2017. HYDROLOGY OF THE HELLAS BASIN AND THE EARLY MARS CLIMATE: WAS THE HONEYCOMB TERRAIN FORMED BY SALT OR ICE DIAPIRISM? Lunar and Planetary Science XLVIII. 1060.pdf</ref> <ref>Weiss, D.; Head, J. (2017). "Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate". Icarus. 284: 249–263.</ref>

 
==Fractured Surface and Blocks==

[[File:44757 2185closeleft.jpg |thumb|300px|left| Rock breaking up into cube-shaped blocks]]
In many places on Mars bedrock breaks up into large blocks. Sometimes the blocks form what look like perfect cubes. Although one may think these shapes had to be made by intelligent aliens, this is a natural process. The salt you put on your food also breaks up into cubes. Check your salt out with a magnifying glass.

 
==Fractured Ground==

Some places on Mars break up with large fractures that create a terrain with mesas and valleys. Some of these can be quite pretty.

<gallery class="center" widths="380px" heights="360px">
File:ESP 048878 2095fractures.jpg|Wide view of fractured ground
File:48878 2095fractures.jpg|Close view of fractured ground
</gallery>

==Dipping layers==

Groups of layers that are tilted are common in some areas of Mars. They represent material that once covered a wide area.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288</ref> The layers may be related to changes in the climate in the past. They may have been shaped by the wind.

<gallery class="center" widths="380px" heights="360px">
File:ESP 050793 1365pyramids.jpg| Wide view of layered features in Hellas quadrangle
File:50793 1365layers2.jpg|Close view of layered features in Hellas quadrangle Each layer may represent a change in the climate.
File:ESP 035801 2210pyramidsismenius.jpg|Tilted layers in Ismenius Lacus These sets of layers can often be seen leaning against slopes.
</gallery>

==Boulders==

Much of the surface of Mars is covered with hard, basalt volcanic rock. When the rock breaks down it often forms large boulders the size of houses.

<gallery class="center" widths="380px" heights="360px">
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas in Elysium quadrangle Box shows size of football field.
File:ESP 045415 2220boulders.jpg|Color view of boulders
File:45575 2535dunebouldertracks.jpg| Close view of dunes showing boulders with arrows If you click on image to enlarge, you can see the tracks left by the boulders as they traveled down the dune.
45575 2535duneboulders.jpg|Boulder and boulder tracks, as seen by HiRISE under HiWish program The arrow shows a boulder that has made a track in the sand as it rolled down dune.
45575 2535dunebouldertracks.jpg|Boulders and tracks, as seen by HiRISE under HiWish program The arrows show a boulders that have produced a track by rolling down dune.

</gallery>

==Hollows==

Some places on Mars have surfaces that are covered with hollows. Sometimes they form large holes, sometimes curved canyons. They can be pretty and would be fun to explore on foot in the future. This terrain may have developed from what has been called ribbed terrain. Either way, these scenes were caused as ice left the ground.

<gallery class="center" widths="380px" heights="360px">
File:ESP 043688 2245hollows.jpg|Wide view of hollows in ground, probably from ice leaving the ground
File:ESP 043688 2245closecolor.jpg|Close color view of hollows in ground, probably from ice leaving the ground
File:ESP 026042 1470hollows.jpg| Hollows in ground, probably from ice leaving the ground Location is Hellas Montes Region.
</gallery>

==Mesas==

Many, large areas of Mars have eroded such that there are many mesas. Some show layers. Mesas show how the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="380px" heights="360px">
File:47441 1800mesaclose.jpg|Mesa with box showing size of football field
File:47421 1890bigbutte.jpg|Layered mesa with box showing size of football field
File:46050 1775race.jpg|Mesa that is 14 km or 8.7 miles around the outside
</gallery>

==Landslides==

Mars shows various mass movements like landslides. There are many steep slopes for material to move down, especially in craters and canyons.

<gallery class="center" widths="380px" heights="360px">
File:ESP 043963 1550landslide.jpg|Landslide
File:ESP 045981 1585landslide.jpg|Landslide

File:ESP 057191 2150landslidecropped.jpg|Landslide
</gallery>

==Latitude Dependent Mantle==

Latitude Dependent Mantle is very common in certain latitudes.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It often appears as a smooth covering. A certain percentage of it consists of ice. It may be a major source of water for future colonists because it has a widespread distribution. Sometimes mantle displays layers because it was deposited at different times.

<gallery class="center" widths="380px" heights="360px">
File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program
File:2509mantlelayers.jpg|Mantle layers with layers
</gallery>

==Exhumed craters==

Exhumed craters seem to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> <ref> https://www.uahirise.org/PSP_001374_1805</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters, as seen by HiRISE under HiWish program

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
</gallery>

==Swiss Cheese Terrain==

Parts of Mare Australe show pits that make the surface look like Swiss cheese.<ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap. These circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.<ref> Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

<gallery class="center" widths="380px" heights="360px">
File:South Pole Terrain.jpg|Swiss Cheese Terrain near South Pole, as seen by HiRISE
File:ESP 058515 0955closechanges.jpg|Changes in Swiss Cheese Terrain from August 2009 to January 2019
</gallery>

<gallery class="center" widths="500px">
File:ESP 014274 0955southpole3.jpg|wiss Cheese Terrain August 2009
File:ESP 058515 0955southpole2.jpg|Swiss Cheese Terrain January 2019
</gallery>

==Ice Cap Layers==

The northern ice cap of Mars displays many layers of ice that accumulated when the climate changed. These are visible when there is a canyon in the ice. The climate of Mars changes greatly due to the large changes in the tilt of Mars. Mars does not have a large moon to stabilize its' tilt.

<gallery class="center" widths="380px" heights="360px">

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019.

File:69629 2605npolarlayerswide.jpg|Layers in northern ice cap
</gallery>

==Spiders==

The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> This results in the appearance of dark plumes that are often blown in one direction by local winds. This dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> This process was demonstrated in laboratory simulations involving slabs of dry ice placed on glass spheres of different sizes.<ref>https://www.nature.com/articles/s41598-021-82763-7.pdf</ref> <ref>McKeown, L., et al. 2021. The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric
pressure. Scientific Reports.</ref> <ref>https://www.livescience.com/spiders-on-mars-explained-dry-ice.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref>

<gallery class="center" widths="380px" heights="360px">
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
File:Spidersmarspedia.jpg|Close view of spiders
</gallery>

==Polygonal Patterned Ground==

Many surfaces on Mars display “polygonal patterned ground.” The polygons can be of different shapes and sizes. They are believed to be caused by ice in the ground.<ref>https://www.uahirise.org/ESP_047247_1150</ref> Like permafrost regions on Earth, this permanently frozen water is still active.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction. Over long periods of cyclic cracking, a honeycomb-like polygonal pattern arises.<ref>https://www.uahirise.org/ESP_066782_1110</ref>

The patterns formed may yet be another marker for underground ice that could be used by future colonists. Before we land crews on Mars, we may very well have detailed maps for where the colonists can obtain water.

<gallery class="center" widths="380px" heights="360px">
File:ESP 049660 1200polygonswide.jpg|Wide view of large and small polygons

File:ESP 049660 1200polygonsclosecolor.jpg|Close, color view of polygons Note: this is an enlargement of the previous wide view image.
File:45070 1440polygonscloseshadows.jpg|High center polygons
</gallery>

<gallery class="center" widths="380px" heights="360px">
File:56148 1145polygonswide.jpg|Wide view of crater floor that is covered with polygons Low places still contain frost. Image taken with HiRISE under HiWish program.

File:56148 1145polygonsclose.jpg|Enlarged view of polygons from previous image. Dark line is a defect in processing.
File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons from a previous image that shows polygons of varying sizes. Dark lines are defects in processing.
</gallery>

==Notes about pictures==

Most pictures from spacecraft have some sort of enhancement. For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red.<ref> https://repository.si.edu/bitstream/handle/10088/19366/nasm_201048.pdf?sequence=1&isAllowed=y</ref> <ref>Delamere, W., et al. 2010. Color imaging of Mars by the High Resolution Imaging Science Experiment (HiRISE). Icarus. 205 pp. 38–52</ref> Displaying colors in this way allows us to better identify rocks and minerals.
HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 025698 1485pinksalt.jpg|HiRISE image with pink color representing chloride salt.
</gallery>

[[File:60331 1880widecolorband.jpg|Wide view of layers in Danielson Crater The center band is in color|600pxr|Wide view of layers in Danielson Crater The center band is in color.]]
Wide view of layers in Danielson Crater The center band is in color.

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Dust devils]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[How living on Mars will be different than living on Earth]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]
*[[Water]]

==Further reading==

* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

== External links ==

*[https://www.uahirise.org/PSP_007820_1505 Layered Sediments in Hellas Planitia]

*[https://www.uahirise.org/PSP_005383_1255 Changes in dust devil tracks]

*[https://static.uahirise.org/images/2020/details/cut/ESP_062948_2175.gif before and after pictures of a new impact]

*[https://static.uahirise.org/images/2020/details/cut/ESP_063204_1800.gif Looking for Slope Streaks-old and new pictures of streaks]]

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground
* [https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

* [https://www.youtube.com/user/MARS3DdotCOM Flying around Candor Chasma at an altitude of 100 meters]

* [https://www.youtube.com/watch?v=Q-2B8J2OU8o Flight over Mars using HiRISE images--very beautiful]

* [https://www.youtube.com/watch?v=mBuvVM_e4G0 HiRISE images of polar regions with narriation]

* [https://www.youtube.com/watch?v=uZ5Y8Qc_dZU&index=2&list=PL2gLpWRK0QlAqGDSlMKS4BaJVbwzEl_0g HiRISE images of beautiful scenes]

* [https://www.youtube.com/watch?v=YIoVtsVsx0Y Flyover of many parts of Mars using HiRISE images--Very nice]

* [https://www.youtube.com/watch?v=siIoqdPG3U4 Pictures from HiRISE and from Curiosity ]

[[category:Areomorphology]]

Ismenius Lacus quadrangle

2023-04-15T15:05:28Z

Suitupandshowup: /* Glaciers */ added image

{{Mars atlas}}

{| class="wikitable sortable"
|MC-05
|Ismenius Lacus
|30–65° N
|0–60° E
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-5-IsmeniusLacusRegion-mola.png|Elevations
File:PIA00165-Mars-MC-5-IsmeniusLacusRegion-19980604.jpg
</gallery>
[[Category:Mars Atlas]]

This quadrangle has some of the most mysterious-looking landscapes on the planet. It truly looks like another world here. Strong evidence of a past ocean on Mars exists in this region and is described below. The Ismenius Lacus quadrangle contains regions called Deuteronilus Mensae and Protonilus Mensae, two places that are of special interest to scientists. They contain abundant evidence of present and past glacial activity. They also have a landscape unique to Mars, called Fretted terrain. The largest crater in the area is Lyot Crater, which contains channels probably carved by liquid water.<ref>Carter | first1 = J. | last2 = Poulet | first2 = F. | last3 = Bibring | first3 = J.-P. | last4 = Murchie | first4 = S. | year = 2010 | title = Detection of Hydrated Silicates in Crustal Outcrops in the Northern Plains of Mars | url = | journal = Science | volume = 328 | issue = 5986| pages = 1682–1686 | </ref>

The Ismenius Lacus quadrangle is located in the northern hemisphere and covers 30° to 65° north latitude and 300° to 360° west longitude (60° to 0° east longitude). The southern and northern borders of the Ismenius Lacus quadrangle are approximately 3065 km (1,905 mi) and 1500 km wide (930 mi) respectively. The north-to-south distance is about 2050 km (1,270 mi) (a bit less than the length of Greenland).<ref>Distances calculated using NASA World Wind measuring tool. http://worldwind.arc.nasa.gov/.</ref> The Ismenius Lacus quadrangle contains parts of regions named Acidalia Planitia, Arabia Terra, Vastitas Borealis, and Terra Sabaea.<ref>http://planetarynames.wr.usgs.gov/SearchResults?target=MARS&featureType=Terra,%20terrae</ref>

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

==Origin of names==

Ismenius Lacus is the name of a classical albedo feature located at 40° N and 30° E on Mars. Like most names for Martian places, Ismenius comes from old myths and stories. The term is Latin for Ismenian Lake, and refers to the Ismenian Spring near Thebes in Greece where Cadmus slew the guardian dragon. Cadmus was the legendary founder of Thebes, and had come to the spring to fetch water. The name was approved by the International Astronomical Union (IAU) in 1958.<ref>USGS Gazetteer of Planetary Nomenclature. Mars. http://planetarynames.wr.usgs.gov/.</ref> All names suggested for astronomical features have to eventually approved by the International Astronomical Union (IAU).

Some important areas in this quadrangle derive from the names of canals that some early astronomers saw in this broad area. One such large canal they called Nilus. Since 1881–1882 it was split into other canals, some were called Nilosyrtis, Protonilus (first Nile),and Deuteronilus (second Nile).<ref>Blunck, J. 1982. Mars and its Satellites. Exposition Press. Smithtown, N.Y.</ref>

==Ocean==

[[File:ESP 054857 2270grooves.jpg|600pxr|Channels that may have been made by the backwash of tsunamis in an ocean Image is from HiRISE under the [[HiWish program]]]]

Channels made by the backwash from tsunamis, tsunamis were probably caused by asteroids striking an ocean. Image is from HiRISE under the [[HiWish program]]

Many researchers have suggested that Mars once had a great ocean in the north.<ref>Parker | first1 = T. J. | last2 = Gorsline | first2 = D. S. | last3 = Saunders | first3 = R. S. | last4 = Pieri | first4 = D. C. | last5 = Schneeberger | first5 = D. M. | year = 1993 | title = Coastal geomorphology of the Martian northern plains | url = | journal = J. Geophys. Res. | volume = 98 | issue = E6| pages = 11061–11078 | doi=10.1029/93je00618 |</ref> <ref>Fairén | first1 = A. G. |display-authors=etal | year = 2003 | title = Episodic flood inundations of the northern plains of Mars | url = http://eprints.ucm.es/10431/1/9-Marte_3.pdf| journal = Icarus | volume = 165 | issue = 1| pages = 53–67 | </ref> <ref> Head | first1 = J. W. |display-authors=etal | year = 1999 | title = Possible ancient oceans on Mars: Evidence from Mars Orbiter Laser Altimeter data | url = | journal = Science | volume = 286 | issue = 5447| pages = 2134–2137 | doi=10.1126/science.286.5447.2134| pmid = 10591640 |</ref> <ref>Parker, T. J., Saunders, R. S. & Schneeberger, D. M. Transitional morphology in west Deuteronilus Mensae, Mars: Implications for modification of the lowland/upland boundary" ''Icarus'' 1989; 82, 111–145</ref> <ref>Carr | first1 = M. H. | last2 = Head | first2 = J. W. | year = 2003 | title = Oceans on Mars: An assessment of the observational evidence and possible fate | url = | journal = J. Geophys. Res. | volume = 108 | issue = E5| page = 5042 |</ref> <ref>Kreslavsky | first1 = M. A. | last2 = Head | first2 = J. W. | year = 2002| title = Fate of outflow channel effluent in the northern lowlands of Mars: The Vastitas Borealis Formation as a sublimation residue from frozen ponded bodies of water | url = | journal = J. Geophys. Res. | volume = 107 | issue = E12| page = 5121 |</ref> <ref>Clifford, S. M. & Parker, T. J. The evolution of the martian hydrosphere: Implications for the fate of a primordial ocean and the current state of the northern plains" ''Icarus'' 2001; 154, 40–79</ref> Much evidence for this ocean has been gathered over several decades. New evidence was published in May 2016. A large team of scientists described how some of the surface in Ismenius Lacus quadrangle was altered by two tsunamis. The tsunamis were caused by asteroids striking the ocean. Both were thought to have been strong enough to create 30 km diameter craters. The first tsunami picked up and carried boulders the size of cars or small houses. The backwash from the wave formed channels by rearranging the boulders. The second came in when the ocean was 300 m lower. The second carried a great deal of ice which was dropped in valleys. Calculations show that the average height of the waves would have been 50 m, but the heights would vary from 10 to 120 meters. So, some large waves would have gone over a 36 story building.<ref>https://www.convertunits.com/from/metre/to/story</ref> Numerical simulations show that in this particular part of the ocean two 30 km in diameter would form every 30 million years. The implication here is that a great northern ocean may have existed for millions of years. One argument against an ocean has been the lack of shoreline features. These features may have been washed away by these tsunami events. The parts of Mars studied in this research are Chryse Planitia and northwestern Arabia Terra. These tsunamis affected some surfaces in the Ismenius Lacus quadrangle and in the [[Mare Acidalium quadrangle]].<ref>Ancient Tsunami Evidence on Mars Reveals Life Potential |date=May 20, 2016 |url=http://astrobiology.com/2016/05/ancient-tsunami-evidence-on-mars-reveals-life-potential.html</ref> <ref>Rodriguez | first1 = J. |display-authors=etal | year = 2016 | title = Tsunami waves extensively resurfaced the shorelines of an early Martian ocean | url = | journal = Scientific Reports | volume = 6 | issue = | page = 25106 | doi=10.1038/srep25106| pmid = 27196957 | pmc = 4872529 |</ref> <ref>| doi=10.1038/srep25106| pmid=27196957| pmc=4872529| title=Tsunami waves extensively resurfaced the shorelines of an early Martian ocean| journal=Scientific Reports| volume=6| pages=25106| year=2016| last1=Rodriguez| first1=J. Alexis P.| last2=Fairén| first2=Alberto G.| last3=Tanaka| first3=Kenneth L.| last4=Zarroca| first4=Mario| last5=Linares| first5=Rogelio| last6=Platz| first6=Thomas| last7=Komatsu| first7=Goro| last8=Miyamoto| first8=Hideaki| last9=Kargel| first9=Jeffrey S.| last10=Yan| first10=Jianguo| last11=Gulick| first11=Virginia| last12=Higuchi| first12=Kana| last13=Baker| first13=Victor R.| last14=Glines| first14=Natalie</ref> <ref>Cornell University. "Ancient tsunami evidence on Mars reveals life potential." ScienceDaily. ScienceDaily, 19 May 2016. https://www.sciencedaily.com/releases/2016/05/160519101756.htm.</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 028537 2270tsunamischannels.jpg|Channels made by the backwash from tsunamis, Tsunamis were probably caused by asteroids striking the ocean.

File:ESP 055714 2270tsunamibackwash.jpg|Possible backwash channels that may have been created by a tsunami, as seen by HiRISE under HiWish program

28537 2270tsunamisboulders.jpg|Boulders that were picked up, carried, and dropped by tsunamis Tsunamis were probably caused by asteroids striking ocean. Boulders in picture are between the size of cars and houses.
Tsunamisstreamlinedp20008931.jpg|Streamlined promontory eroded by tsunami Tsunamis were probably caused by asteroids striking ocean.
File:ESP 054989 2270curvedbands.jpg|Concentric bands that may have been produced by the waves of a tsunami. Image is from HiRISE under the HiWish program.

</gallery>

==Channels (Rivers)==

[[File:ESP 043623 2160meander.jpg|600pxr|Meanders Meanders are commonly formed in old river systems when the water is moving slowly.]]
Meanders They are formed in old river systems when the water is moving slowly.

Many features were probably rivers with water flowing in them billions of years ago. Pictures below show many channels and parts of channels.

The channel shown below goes quite a long distance and has branches. It ends in a depression that may have been a lake at one time. The first picture is a wide angle, taken with CTX; while the second is a close up taken with HiRISE.<ref>http://www.uahirise.org/ESP_039997_2170</ref>

<gallery class="center" widths="380px" heights="360px">

Wikichannelsarabia.jpg|Channels in Arabia, as seen by CTX This channel winds along for a good distance and has branches. It ends in a depression that may have been a lake at one time.

WikiESP 039997 2170channels.jpg|Channel in Arabia, as seen by HiRISE under [[HiWish program]]. This is an enlargement of the previous image that was taken with CTX to give a wide view.

</gallery>

Some places (like below) display a smaller channel within a larger, wider channel or valley. When this occurs it means water went through the region at least two times in the past. This implies that water was not just here once for a short period of time.

<gallery class="center" widths="380px" heights="360px">

ESP 039931 2165channels.jpg|Channel within larger channel The existence of the smaller channel suggests water went through the region at least two times in the past.

ESP 039931 2165close.jpg|Close-up of channel within larger channel The existence of the smaller channel suggests water went through the region at least two times in the past. The black box represents the size of a football field. Some parts of the surface would be difficult to walk on with the many small hills and depressions.
</gallery>

<gallery class="center" widths="380px" heights="360px">

ESP 042924 2195channel.jpg|Channel system that travels through part of a crater

ESP 045548 2155channel.jpg|Channel that cut through a crater rim

42924 2195channelnetwork.jpg|Channel system that travels through part of a crater Note: this is an enlargement of a previous image.

42924 2195channel.jpg|Channel that travels through part of a crater The arrow shows a crater that was eroded by the channel. Note: this is an enlargement of a previous image.

ESP 042502 2200channels.jpg|Channels

ESP 045837 2245channels.jpg|Wide view of channels

45837 2245channel.jpg|Close view of channel

ESP 045838 2130channel.jpg|Channel that has cut through a crater rim

ESP 045850 2210channels.jpg|Wide view of channels, as seen by HiRISE under HiWish program

ESP 045864 2160channels.jpg|Wide view of channels

ESP 045904 2145channelstop.jpg|Channel

ESP 045916 2205channels.jpg|Wide view of channels

45916 2205hanging.jpg|Channel with hanging valley

ESP 046010 2160channels.jpg|Wide view of channels

ESP 046049 2140channels.jpg|Wide view of channels, as seen by HiRISE under HiWish program

ESP 046458 2160channel.jpg|Channel
ESP 050914 2130channel.jpg|Channels

ESP 052761 2170channel.jpg|Channels, as seen by HiRISE under HiWish program

ESP 052774 2160mantle.jpg|Channels, Some parts of the image show mantle and others show no mantle covering the surface.

File:ESP 053420 2160inverted channel.jpg|Possible inverted channel Here after a stream bed got filled with erosion resistant materials, the surrounding, softer landscape eroded away.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 057627 2175channelssapping.jpg|Channels The ends of the channels have shapes that suggest they were formed by the process of sapping.
File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

File:ESP 057560 2180channel.jpg|Channel near ejecta

</gallery>

[[File:ESP 056689 2210channelslowspot.jpg|600pxr|Channels that empty into a low area that could have been a lake, as seen by HiRISE under HiWish program]]

Channels that empty into a possible lake, as seen by HiRISE under [[HiWish program]]

== Lyot Crater ==

The vast northern plains of Mars are generally flat and smooth with few craters. However, a few large craters do stand out. The giant impact crater, Lyot, is easy to see in the northern part of Ismenius Lacus. There are only a very few craters along the far northern latitudes.<ref>U.S. department of the Interior U.S. Geological Survey, Topographic Map of the Eastern Region of Mars M 15M 0/270 2AT, 1991</ref> Lyot Crater is the deepest point in Mars's northern hemisphere.<ref>http://space.com/scienceastronomy/090514--mars-rivers.html</ref> One image below of Lyot Crater Dunes shows a variety of interesting forms: dark dunes, light-toned deposits, and Dust Devil Tracks. Dust devils, which resemble miniature tornados, create tracks by removing a thin, but bright deposit of dust to reveal the darker underlying surface. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will do the trick. Note on units: a micron is an older name for micrometre or micrometer. The width of a single human hair ranges from approximately 20 to 200 microns (μm); hence, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Light-toned materials are an important find because they are widely believed to contain minerals formed in water. Research, published in June 2010, described evidence for liquid water in Lyot crater in the past.

Many channels have been found near Lyot Crater. Research, published in 2017, concluded that the channels were made from water released when the hot ejecta landed on a layer of ice that was 20 to 300 meters thick. Calculations suggest that the ejecta would have had a temperature of at least 250 degrees Fahrenheit. The valleys seem to start from beneath the ejecta near the outer edge of the ejecta. The existence of these channels is unusual because although Mars used to have water in rivers, lakes, and an ocean; channels in Lyot came after we had thought that Mars had dried up. So Mars had flowing water later then we believed.<ref>doi=10.1002/2017GL073821 | volume=44 | issue=11 | title=Extensive Amazonian-aged fluvial channels on Mars: Evaluating the role of Lyot crater in their formation | journal=Geophysical Research Letters | pages=5336–5344 | last1 = Weiss | first1 = David K.| </ref> <ref>Weiss, D., et al. 2017. Extensive Amazonian-aged fluvial channels on Mars: Evaluating the role of Lyot crater in their formation. Geophysical Research Letters: 44, doi:10.1002/2017GL073821.</ref> <ref>http://spaceref.com/mars/hot-rocks-led-to-relatively-recent-water-carved-valleys-on-mars.html</ref>

[[File: ESP 045389 2295lyotchannels.jpg|600pxr|Wide view of channels in Lyot Crater, as seen by HiRISE under [[HiWish program]]]]
Wide view of channels in Lyot Crater, as seen by HiRISE under [[HiWish program]]

<gallery class="center" widths="380px" heights="360px">

ESP 045389 2295lyotchannelstop.jpg|Close view of channels in Lyot Crater
ESP 045389 2295lyotchannelsbottom.jpg|Close view of channels in Lyot Crater, as seen by HiRISE under HiWish program

Image:Lyot Mars Crater Dunes.JPG|Lyot Crater Dunes, as seen by HiRISE. Click on image to see light-toned deposits and dust devil tracks.

File:ESP 053485 2305lyotchannel.jpg|Channel

</gallery>

==Other craters==

Impact craters generally have a rim with ejecta around them; in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter), they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/</ref> The peak is caused by a rebound of the crater floor following the impact.<ref>Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|accessdate=7 March 2011|date=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7}}</ref> Sometimes craters will display layers in their walls. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, craters are useful for showing us what lies deep under the surface.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057007 2190freshcrater.jpg|Fresh crater, as seen by HiRISE under HiWish program This is a young crater because one can easily see the rim and ejecta. They have not yet been eroded.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.

File:ESP 054963 1950craterbench.jpg|Crater with a bench A crater with a bench may be formed from settling of the crater wall or it may be due to impact into something with vastly different types of layers.

File:ESP 056953 2160expandedcraters.jpg|Possible expanded secondary craters, as seen by HiRISE under [[HiWish program]] These craters may have become much wider, as ice left the ground around the rims.<ref>http://www.uahirise.org/epo/nuggets/expanded-secondary.pdf</ref> <ref>Viola, D., et al. 2014. EXPANDED CRATERS IN ARCADIA PLANITIA: EVIDENCE FOR >20 MYR OLD SUBSURFACE ICE. Eighth International Conference on Mars (2014). 1022pdf.</ref>

ESP 053867 2245hotejecta.jpg|Impact crater that may have formed in ice-rich ground, as seen by HiRISE under [[HiWish program]]

File:53867 2245hotejectamargin.jpg |Impact crater that may have formed in ice-rich ground Note that the ejecta seems lower than the surroundings. The hot ejecta may have caused some of the ice to go away; thus lowering the level of the ejecta.

File: ESP 054407 2265pedestal.jpg|Pedestal crater The crater's ejecta protected the underlying ground from eroding.

File:ESP 054830 2260pedestal.jpg|Pedestal crater Mesa on the crater floor formed after the crater.

</gallery>

<gallery class="center" widths="380px" heights="360px">

Image:Cerulli Crater.jpg|Cerulli Crater It looks like a delta was formed as channels bought in debris and dumped then in a lake that was in the crater.

ESP 044506 2245layers.jpg|Group of layers in crater
</gallery>

[[File: Wikiquenissetglaciers.jpg|600pxr|Northeast rim of Quenisset Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Arrows indicate old glaciers.]]
|Northeast rim of Quenisset Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Arrows indicate old glaciers.

== Deltas ==

Researchers have found a number of examples of deltas that formed in Martian lakes. Deltas are major signs that Mars once had a lot of water because deltas usually require deep water over a long period of time to form. In addition, the water level needs to be stable to keep sediment from washing away. Deltas have been found over a wide geographical range. Below, is a pictures of a one in the Ismenius Lacus quadrangle.<ref>Irwin III, R. et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development. Journal of Geophysical Research: 10. E12S15</ref>

<gallery class="center" widths="380px" heights="360px">
Image:Delta in Ismenius Lacus.jpg|Delta in Ismenius Lacus quadrangle, as seen by THEMIS.
</gallery>

== Fretted terrain ==

The Ismenius Lacus quadrangle contains several interesting features such as fretted terrain, parts of which are found in Deuteronilus Mensae and Protonilus Mensae. Fretted terrain contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Many buttes and mesas are present. In fretted terrain the land seems to transition from narrow straight valleys to isolated mesas.<ref>Sharp, R. 1973. Mars Fretted and chaotic terrains. J. Geophys. Res.: 78. 4073–4083</ref> Most of the mesas are surrounded by forms that have been called a variety of names: circum-mesa aprons, debris aprons, rock glaciers, and lobate debris apron (LDA)s. The flat floors here often display many lines or lineations that scientists call lineated valley fill (LVF). These are caused by glacier-like flow. <ref>http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1053.pdf</ref> At first they appeared to resemble rock glaciers on Earth. But scientists could not be sure. Even after the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of fretted terrain, experts could not tell for sure if material was moving or flowing as it would in an ice-rich deposit (glacier). Eventually, proof of their true nature was discovered by radar studies with the [[Mars Reconnaissance Orbiter]] showed that they contain pure water ice covered with a thin layer of rocks that insulated the ice.<ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>Plaut | first1 = J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J. | last4 = Phillips | first4 = R. | last5 = Head | first5 = J. | last6 = Seu | first6 = R. | last7 = Putzig | first7 = N. | last8 = Frigeri | first8 = A. | year = 2009 | title = Radar evidence for ice in lobate debris aprons in the midnorthern latitudes of Mars | url = https://semanticscholar.org/paper/f6b94761e6a276ce6894374ae9bea88fdc3e5e19| journal = Geophys. Res. Lett. | volume = 36| issue = 2| pages = n/a |</ref>

<gallery class="center" widths="380px" heights="360px">

Image:Fretted terrain of Ismenius Lacus taken with MGS.JPG|Fretted terrain of Ismenius Lacus showing flat floored valleys and cliffs. Photo taken with Mars Orbiter Camera (MOC) on the [[Mars Global Surveyor]], under the MOC Public Targeting Program. The white rectangle indicates the position of a high resolution image.

Image:Steep cliff in Ismenius Lacus taken with MGS.JPG|Enlargement of the photo on the left showing cliff. Photo taken with high-resolution camera of Mars Global Surveyor (MGS), under the MOC Public Targeting Program.

Wikictxp13clifflda.jpg|Wide view of mesa with CTX showing cliff face and location of lobate debris apron (LDA).

Wikifretesp 028313 2220cliff.jpg|Enlargement of previous CTX image of mesa. This image shows the cliff face and detail in the LDA. Image taken with HiRISE under HiWish program.

WikiESP 020769 2225fretted.jpg|Close-up of lineated valley fill (LVF) Note: this is an enlargement of the previous CTX image.

File:ESP 057020 2180fretterrain.jpg|Example of frettered terrain Fretted terrain contains many wide, flat-floored valleys.

</gallery>

[[File: Wikifrettedctxp22.jpg|600pxr|Wide CTX view showing mesa and buttes with lobate debris aprons and lineated valley fill around them. ]]
Wide CTX view showing mesa and buttes with lobate debris aprons and lineated valley fill around them. These are typical features of fretted terrain

== Glaciers ==

[[File: ESP 052127 2225flow.jpg|600pxr|Flow, as seen by HiRISE under HiWish program]]
Glacier, as seen by HiRISE under HiWish program

The Ismenius Lacus quadrangle might well be called the land of glaciers. Glaciers formed much of the observable surface in large areas of Mars. Much of the area in high latitudes, especially the Ismenius Lacus quadrangle, is believed to still contain enormous amounts of water ice.<ref>Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7</ref> <ref> Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://www.esa.int/SPECIALS/Mars_Express/SEMBS5V681F_0.html</ref> In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris.<ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> The ice was probably deposited as snowfall during an earlier climate when the poles were tilted more.<ref>Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> It would be difficult to take a hike on the fretted terrain where glaciers are common because the surface is folded, pitted, and often covered with linear striations.<ref>http://www.uahirise.org/ESP_018857_2225</ref> The striations show the direction of movement. Much of this rough texture is due to sublimation of buried ice. The ice goes directly into a gas (this process is called sublimation) and leaves behind an empty space. Overlying material then collapses into the void.<ref>http://hirise.lpl.arizona.edu/PSP_009719_2230</ref> Glaciers are not pure ice; they contain dirt and rocks. At times, they will dump their load of materials into ridges. Such ridges are called moraines.

<gallery class="center" widths="380px" heights="360px">

Image:Evidence of Glaciers in Fretted terrain.JPG|The arrow in the left picture points to a possibly valley carved by a glacier. The image on the right shows the same valley greatly enlarged in a Mars Global Surveyor image.

Wikielephantglacier.jpg|Romer Lake's Elephant Foot Glacier in the Earth's Arctic, as seen by Landsat 8. This picture shows several glaciers that have the same shape as many features on Mars that are believed to also be glaciers.

ESP 045560 2230wideglacier.jpg|Glacier coming out of valley Location is rim of Moreux Crater.

ESP 052179 2215flow.jpg|Flow

ESP 049476 2235glaciers.jpg|Glaciers moving from valleys in a mesa

ESP 046021 2175glaciers.jpg|Two glaciers interacting The one on the left is more recent and is flowing on top of the other one.

ESP 049410 2245flow.jpg|Glacier interacting with an obstacle

46075 2200glacier.jpg|Glacier flowing out of valley

ESP 046734 2270ridge.jpg|Ridge that is probably from an old glacier

ESP 046061 2190lvf.jpg|Lineated valley fill, as seen by HiRISE under [[HiWish program]].

46061 2190closelvf..jpg|Close view of Lineated valley fill

ESP 046061 2190closebrains.jpg|Close, color view of Lineated valley fill

ESP 046840 2130lvf.jpg|Lineated valley fill in valley

ESP 050137 2185lvf.jpg|Lineated valley fill in valley Linear valley fill is ice covered by debris.

ESP 050137 2185lvfclosecolor.jpg|Close, color view of lineated valley fill

Image:Lobate feature with hiwish.JPG|Probable glacier Radar studies have found that it is made up of almost completely pure ice. It appears to be moving from the high ground (a mesa) on the right.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it. One of the glaciers is seen in greater detail in the next two images from HiRISE.

Image:Wide view of glacier showing image field.JPG|Glacier as seen by HiRISE under the HiWish program. Area in rectangle is enlarged in the next photo. Zone of accumulation of snow at the top. Glacier is moving down valley, then spreading out on plain. Evidence for flow comes from the many lines on surface. Location is in Protonilus Mensae.

Image:Glacier close up with hirise.JPG|Enlargement of area in rectangle of the previous image. On Earth the ridge would be called the terminal moraine of an alpine glacier.

Image:ESP 028352 2245glacier.jpg|Remains of a glacier after ice has disappeared

Wikildaf03 036777 2287.jpg|Lobate debris aprons (LDAs) around a mesa, as seen by CTX Mesa and LDAs are labeled so one can see their relationship. Radar studies have determined that LDAs contain ice; therefore these can be important for future colonists of Mars.

Wikifrettedctxpo5.jpg|Wide CTX view of mesa showing lobate debris apron (LDA) and lineated valley fill. Both are believed to be debris-covered glaciers.

</gallery>

[[File: Wikifretesp 027639 2210lda.jpg|600pxr|Close-up of lobate debris apron from the previous CTX image of a mesa. Image shows open-cell brain terrain and closed-cell brain terrain, which is more common. Closed-cell brain terrain is thought to hold a core of ice.]]
Close-up of lobate debris apron from the previous CTX image of a mesa. Image shows open-cell brain terrain and closed-cell brain terrain, which is more common. Closed-cell brain terrain is thought to hold a core of ice.

[[File:77699 2215contextldactx.jpg|600pxr|Wide and close views of LDA]]

Wide and close views of LDA

<gallery class="center" widths="380px" heights="360px">

File:ESP 057389 2195flow.jpg|Lobate debris apron around mesa

File:ESP 057389 2195lda.jpg|Close view of lobate debris apron around mesa Brain terrain is visible.

ESP 044874 2205glaciers.jpg|Glaciers moving in two different valleys

ESP 045085 2205flow.jpg|Wide view of flow moving down valley

45085 2205close.jpg|Close view of part of glacier Box shows size of football field.

ESP 051177 2230flowmantle.jpg|Flow and mantle Mantle appears as layers against the cliff face.

</gallery>

<gallery class="center" widths="380px" heights="360px">

ESP 049555 2225tongue.jpg|Wide view of tongue-shaped glacier and lineated valley fill

49555 2225tongue.jpg|Tongue-shaped glacier Note: this is an enlargement of the previous image
49555 2225tongueclose.jpg|Close view of tongue-shaped glacier Surface is broken up into cubes.

</gallery>

==Latitude dependent mantle==

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past.<ref>Hecht | first1 = M | year = 2002 | title = Metastability of water on Mars | url = | journal = Icarus | volume = 156 | issue = 2| pages = 373–386 | doi=10.1006/icar.2001.6794 |</ref> <ref>Mustard | first1 = J. |display-authors=etal | year = 2001 | title = Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice | url = | journal = Nature | volume = 412 | issue = 6845| pages = 411–414 |</ref> <ref>Pollack | first1 = J. | last2 = Colburn | first2 = D. | last3 = Flaser | first3 = F. | last4 = Kahn | first4 = R. | last5 = Carson | first5 = C. | last6 = Pidek | first6 = D. | year = 1979 | title = Properties and effects of dust suspended in the martian atmosphere | url = | journal = J. Geophys. Res. | volume = 84 | issue = | pages = 2929–2945 | doi=10.1029/jb084ib06p02929 |</ref>

<gallery class="center" widths="380px" heights="360px">
45085 2205mantlethickness.jpg|Close view of mantle Arrows show craters along edge which highlight the thickness of mantle.
45917 2220gulliesmantle.jpg|Close view that displays the thickness of mantle.
ESP 046444 2225flows.jpg|Mantle and flow A part of the image showing the mantle is enlarged in the next image.
46444 2225mantle.jpg|Mantle, as seen by HiRISE under [[HiWish program]]
51177 2230mantle.jpg|Close view of mantle

51230 2200mantle.jpg|Close view of mantle, as seen by HiRISE under HiWish program

ESP 052774 2160mantleclosecolor.jpg|Color view of mantle Some parts of the image are covered with mantle; other parts are not.

File:ESP 057480 2205mantlelayerstop.jpg|Mantle layers lying against steep slopes. Each layer represents a change in the climate of Mars.

File:ESP 057480 2205pyramid.jpg|Mantle layers Mantle layers seem to be forming a group of dipping layers.
</gallery>

==Climate change caused ice-rich features==

Many features on Mars, especially ones found in the Ismenius Lacus quadrangle, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees<ref>Touma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref> Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Large changes in the tilt explains many ice-rich features on Mars.

Studies have shown that when the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles.<ref>Levy | first1 = J. | last2 = Head | first2 = J. | last3 = Marchant | first3 = D. | last4 = Kowalewski | first4 = D. | year = 2008 | title = Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution | url = | journal = Geophys. Res. Lett. | volume = 35| issue = 4| pages = L04202 | doi = 10.1029/2007GL032813 |</ref> Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Calculations suggest this material will concentrate in the mid-latitudes, like those of the Ismenius Lacus quadrangle.<ref> Levy | first1 = J. | last2 = Head | first2 = J. | last3 = Marchant | first3 = D. | year = 2009a | title = Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations | url = | journal = J. Geophys. Res. | volume = 114| issue = E1| pages = E01007 | doi = 10.1029/2008JE003273 |</ref> <ref>Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111–131</ref> General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found.<ref>Laskar, J.; Correia, A.; Gastineau, M.; Joutel, F.; Levrard, B.; Robutel, P. (2004). "Long term evolution and chaotic diffusion of the insolation quantities of Mars". Icarus. 170 (2): 343–364.</ref> When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust.<ref>Mellon | first1 = M. | last2 = Jakosky | first2 = B. | year = 1995 | title = The distribution and behavior of Martian ground ice during past and present epochs | url = https://semanticscholar.org/paper/815bfd93bdb19325e03e08556d145fa470112e4e| journal = J. Geophys. Res. | volume = 100 | issue = E6| pages = 11781–11799 |</ref> <ref>Schorghofer | first1 = N | year = 2007 | title = Dynamics of ice ages on Mars | url = | journal = Nature | volume = 449 | issue = 7159| pages = 192–194 | doi=10.1038/nature06082| pmid = 17851518 |</ref> The lag deposit caps the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind.<ref>Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> Note, that the smooth surface mantle layer probably represents only relative recent material.

==Upper Plains Unit==

Remnants of a 50–100 meter thick mantling, called the Upper Plains Unit, has been discovered in the mid-latitudes of Mars. It was first investigated in the Deuteronilus Mensae region, but it occurs in other places as well. The remnants consist of sets of dipping layers in craters and along mesas.<ref>http://www.uahirise.org/ESP_048897_2125</ref> <ref>Carr | first1 = M | year = 2001 | title = Mars Global Surveyor observations of martian fretted terrain | url = | journal = J. Geophys. Res. | volume = 106 | issue = E10| pages = 23571–23593 | doi=10.1029/2000je001316 |</ref> Sets of dipping layers may be of various sizes and shapes—some look like Aztec pyramids from Central America.

<gallery class="center" widths="380px" heights="360px">

47578 2245ctxP04 002481 2241.jpg|Wide view showing contact between upper plains unit lower part of picture and a lower unit, as seen by CTX

ESP 047578 2245contact.jpg|Contact Upper plains unit on the left is breaking up. A lower unit exists on the right side of picture.

47578 2245contactclose.jpg|Close view of contact Picture shows details of how upper plains material is breaking. The formation of many fractures seems to proceed the break up.

</gallery>

<gallery class="center" widths="380px" heights="360px">
ESP 048870 2250contact.jpg|Wide view of upper plains unit eroding into hollows Parts of this image are enlarged in following images.

48870 2250contact.jpg|Close view of upper plain unit eroding into hollows Break up begins with cracks on the surface that expand as more and more ice disappears from the ground.

48870 2250contactclose.jpg|Close view of hollows
</gallery>

Associated with this unit are dipping layers. However, these groups of layers are found in many locations around the planet. They may be mostly caused by the build up and later erosion of layers of mantle. Mantle has been built up from many climate changes. These "dipping layers" occur mainly in protected spots--like inside craters or against the steep slope of a mesa or the walls of a depression.

<gallery class="center" widths="380px" heights="360px">

ESP 045613 2230pyramids.jpg|Wide view of dipping layers along mesa walls

45613 2230pyramids.jpg|Close view of dipping layers along a mesa wall

ESP 035684 2160pyramidsbrains.jpg|Dipping layers

ESP 036790 2200pyramids.jpg|Dipping layers in a crater

P1010377redrocksfall.jpg|Layered feature in Red Rocks Park, Colorado. This has a different origin than ones on Mars, but it has a similar shape. Features in Red Rocks region were caused by uplift of mountains.

46180 2225brains.jpg|Close view of dipping layers Brain terrain is also visible in the image.

</gallery>

This unit also degrades into "brain terrain." Brain terrain is a region of maze-like ridges 3–5 meters high. The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.

<gallery class="center" widths="380px" heights="360px">

45507 2200brains.jpg|Brain terrain, as seen by HiRISE under [[HiWish program]]

45917 2220brainsopenclosed.jpg|Open and closed brain terrain with labels The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.

ESP 042105 2235brainsforming.jpg|Brain terrain being formed from a thicker layer Arrows show the thicker unit breaking up into small cells.

46075 2200brainsforming.jpg|Brain terrain being formed Arrows point to locations where the brain terrain is starting to form.

45349 2235brainsforming3.jpg|Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image.

45349 2235brainsforming2.jpg|Brain terrain being formed Note: this is an enlargement of a previous image using HiView. Arrows indicate spots where brain terrain is beginning to form.

ESP 045363 2190brain.jpg|Wide view of brain terrain being formed, as seen by HiRISE under HiWish program

46075 2200brainsside.jpg|Brain terrain with a view from the side Arrow shows where a side view of the brain terrain is visible.

</gallery>

Some regions of the upper plains unit display large fractures and troughs with raised rims; such regions are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Stress is suggested to initiate the fracture process since ribbed upper plains are common when debris aprons come together or near the edge of debris aprons—such sites would generate compressional stresses. Cracks exposed more surfaces, and consequently more ice in the material sublimates into the planet's thin atmosphere. Eventually, small cracks become large canyons or troughs.

<gallery class="center" widths="380px" heights="360px">

ESP 028339 2245headarticle.jpg|Well developed ribbed upper plains material. These start with small cracks that expand as ice sublimates from the surfaces of the crack.

ESP 042765 2245cracks.jpg|Small and large cracks The small cracks to the left will enlarge to become much larger due to sublimation of ground ice. A crack exposes more surface area, hence greatly increases sublimation in the thin Martian air.

42765 2245close.jpg|Close-up of canyons from previous image

</gallery>

[[File: ESP 042198 2235pyramid.jpg|600pxr|View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain.]]
View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain.

<gallery class="center" widths="380px" heights="360px">
ESP 035011 2240pyramidshead.jpg|Dipping layers Also, Ribbed Upper plains material is visible in the upper right of the picture. It is forming from the upper plains unit, and in turn is being eroded into brain terrain.<ref>http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.722.2437&rep=rep1&type=pdf</ref> <Baker, D and J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains
in Deuteronilus Mensae, Mars: Implications for the record
of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

45402 2230cracksmesas.jpg|Ribbed terrain being formed from upper plains unit, as seen by HiRISE under HiWish program Formation begins with cracks that enhance sublimation. Box shows the size of football field.

45837 2245turtles.jpg|Surface breaking down, as ice is removed Box shows size of football field.

ESP 046365 2245ribbed.jpg|Wide view of terrain caused by ice leaving the ground
ESP 046365 2245middle.jpg|Close view of terrain caused by ice leaving the ground

ESP 046325 2225hollowa.jpg|Wide view of terrain caused by ice leaving the ground

</gallery>

[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of terrain caused by ice leaving the ground Box shows size of football field.]]
Close view of terrain caused by ice leaving the ground Box shows size of football field.

Small cracks often contain small pits and chains of pits; these are thought to be from sublimation of ice in the ground.<ref>Morgenstern, A., et al. 2007</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269–288.</ref> Large areas of the Martian surface are loaded with ice that is protected by a meters thick layer of dust and other material. However, if cracks appear, a fresh surface will expose ice to the thin atmosphere.<ref> Mangold | first1 = N | year = 2003 | title = Geomorphic analysis of lobate debris aprons on Mars at Mars Orbiter Camera scale: Evidence for ice sublimation initiated by fractures | url = | journal = J. Geophys. Res. | volume = 108 | issue = E4| page = 8021 | doi=10.1029/2002je001885 </ref> <ref>Levy, J. et al. 2009. Concentric</ref> In a short time, the ice will disappear into the cold, thin atmosphere in a process called "sublimation." Dry ice behaves in a similar fashion on the Earth. On Mars sublimation has been observed when the Phoenix lander uncovered chunks of ice that disappeared in a few days.<ref>http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080619.html Bright Chunks at ''Phoenix'' Lander's Mars Site Must Have Been Ice – Official NASA press release (19.06.2008)</ref> <ref>http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080619.html</ref> In addition, HiRISE has seen fresh craters with ice at the bottom. After a time, HiRISE saw the ice deposit disappear.<ref> Byrne | first1 = S. |display-authors=etal | year = 2009 | title = Distribution of Mid-Latitude Ground Ice on Mars from New Impact Craters | url = | journal = Science | volume = 329 | issue = 5948| pages = 1674–1676 | doi = 10.1126/science.1175307 | </ref>

<gallery class="center" widths="380px" heights="360px">

</gallery>

The upper plains unit is thought to have fallen from the sky. It drapes various surfaces, since it fell evenly onto all surfaces. As is the case for other mantle deposits, the upper plains unit has layers, is fine-grained, and is ice-rich. It is widespread; it does not seem to have a point source. The surface appearance of some regions of Mars is due to how this unit has degraded. It is a major cause of the surface appearance of lobate debris aprons.<ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269–288.</ref> The layering of the upper plains mantling unit and other mantling units are believed to be caused by major changes in the planet's climate. Models predict that the obliquity or tilt of the rotational axis has varied from its present 25 degrees to maybe over 80 degrees over geological time. Periods of high tilt will cause the ice in the polar caps to be redistributed and change the amount of dust in the atmosphere.<ref>Head, J. et al. 2003.</ref> <ref>Madeleine, et al. 2014.</ref> <ref>Schon |display-authors=etal | year = 2009 | title = A recent ice age on Mars: Evidence for climate oscillations from regional layering in mid-latitude mantling deposits | url = | journal = Geophys. Res. Lett. | volume = 36 | issue = 15| page = L15202 | bibcode = 2009GeoRL..3615202S|</ref>

== Pits and cracks ==

Some places in the Ismenius Lacus quadrangle display large numbers of cracks and pits. It is widely believed that these are the result of ground ice sublimating (changing directly from a solid to a gas). After the ice leaves, the ground collapses in the shape of pits and cracks. The pits may come first. When enough pits form, they unite to form cracks.<ref>http://hirise.lpl.arizona.edu/PSP_009719_2230 |title=HiRISE | Fretted Terrain Valley Traverse (PSP_009719_2230) |publisher=Hirise.lpl.arizona.edu |</ref>

<gallery class="center" widths="380px" heights="360px">

Image:CTX Context Image of Pits.JPG|CTX Image in Protonilus Mensae, showing location of next image.

Image:Pits in Protonilus Mensae.JPG|Pits in Protonilus Mensae, as seen by HiRISE, under the [[HiWish program]].

</gallery>

[[File: 49700 2250pitsclose.jpg|600pxr|Close view of lines of pits Box shows size of football field. Pits may be up to around 50 meters across.]]

Close view of lines of pits Box shows size of football field. Pits may be up to around 50 meters across.

<gallery class="center" widths="380px" heights="360px">
49700 2250polygons.jpg|Close view of pits and polygons, as seen by HiRISE Pits seem to occur in low spots between polygons.

52588 2210pits.jpg|Close view of pits, as seen by HiRISE, under the HiWish program
</gallery>

==Mesas formed by ground collapse==

<gallery class="center" widths="380px" heights="360px">
ESP 043201 2160blocks.jpg|Group of mesas Oval box contains mesas that may have moved apart.

43201 2160blocks.jpg|Enlarged view of a group of mesas One surface is forming square shapes.

</gallery>

==Polygonal patterned ground==

Polygonal, patterned ground is quite common in some regions of Mars.<ref>http://www.diss.fu-berlin.de/diss/servlets/MCRFileNodeServlet/FUDISS_derivate_000000003198/16_ColdClimateLandforms-13-utopia.pdf?hosts=</ref> <ref> Kostama | first1 = V.-P. | last2 = Kreslavsky | first2 = Head | year = 2006 | title = Recent high-latitude icy mantle in the northern plains of Mars: Characteristics and ages of emplacement | url = | journal = Geophys. Res. Lett. | volume = 33 | issue = 11| page = L11201 |</ref> <ref> Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2001 | title = Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission | url = https://semanticscholar.org/paper/ad350109a111b6425140583455c222a0529f45c6| journal = J. Geophys. Res. | volume = 106 | issue = E10| pages = 23429–23540 |</ref> <ref>Milliken | first1 = R. |display-authors=etal | year = 2003 | title = Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images | url = https://semanticscholar.org/paper/a822f14644d2294b948e101be2f294ac33b57ec3| journal = J. Geophys. Res. | volume = 108 | issue = E6| page = E6 | doi = 10.1029/2002JE002005 |</ref> <ref>Mangold | first1 = N | year = 2005 | title = High latitude patterned grounds on Mars: Classification, distribution and climatic control | url = | journal = Icarus | volume = 174 | issue = 2| pages = 336–359 | doi=10.1016/j.icarus.2004.07.030 |</ref> <ref>Kreslavsky | first1 = M. | last2 = Head | first2 = J. | year = 2000 | title = Kilometer-scale roughness on Mars: Results from MOLA data analysis | url = | journal = J. Geophys. Res. | volume = 105 | issue = E11| pages = 26695–26712 | doi=10.1029/2000je001259 |</ref> <ref>Seibert | first1 = N. | last2 = Kargel | first2 = J. | year = 2001 | title = Small-scale martian polygonal terrain: Implications or liquid surface water | url = | journal = Geophys. Res. Lett. | volume = 28 | issue = 5| pages = 899–902 </ref> It is commonly believed to be a marker for ice-rich ground because these shapes are common on the Earth in cold regions with lots of ice in the ground.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction.<ref>https://www.uahirise.org/ESP_066782_1110</ref>

Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer, called latitude dependent mantle, that fell from the sky when the climate was different.<ref>Kreslavsky, M.A., Head, J.W., 2002. High-latitude Recent Surface Mantle on Mars: New Results from MOLA and MOC. European Geophysical Society XXVII, Nice.</ref> <ref>Head | first1 = J.W. | last2 = Mustard | first2 = J.F. | last3 = Kreslavsky | first3 = M.A. | last4 = Milliken | first4 = R.E. | last5 = Marchant | first5 = D.R. | year = 2003 | title = Recent ice ages on Mars | url = | journal = Nature | volume = 426 | issue = 6968| pages = 797–802 | doi=10.1038/nature02114| pmid = 14685228 |</ref>

<gallery class="center" widths="380px" heights="360px">

43899 2265closecrack.jpg|Close-up of field of high center polygons with scale Note: the black box is the size of a football field.

43899 2265highcenterpolygonsclose2.jpg|Close-up of high center polygons Note: the black box is the size of a football field.

</gallery>

[[File: 45363 2190lowcenterpolygons.jpg|600pxr|Low center polygons]]
Low center polygons

<gallery class="center" widths="380px" heights="360px">

ESP 047275 2255hcpolygons.jpg|Wide view of high center polygons
47275 2255hcpolygonsclose.jpg|Close view of high center polygons Centers of polygons are labeled.

ESP 052101 2260largepolygons.jpg|Large polygons
</gallery>

==Gullies==

Gullies were thought for a time to have been caused by recent flows of liquid water. However, further study suggests they are formed today by chunks of dry ice moving down steep slopes.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |date=July 10, 2014 |work=[[NASA]] |accessdate=July 10, 2014 </ref>

<gallery class="center" widths="380px" heights="360px">

ESP 044122 2335gullies.jpg|Gullies in crater, as seen by HiRISE under HiWish program

45561 2310gulliesclose.jpg|Close view of channel in gully showing streamlined forms
ESP 045917 2220gulliespyramids.jpg|Gullies
45917 2220gulliesclose.jpg|Close view of gullies, as seen by HiRISE under HiWish program
45917 2220gulliespolygons.jpg|Close view of gullies
</gallery>

==Layered features==

<gallery class="center" widths="380px" heights="360px">
ESP 046443 2165layers.jpg|Layers
46443 2165mesa.jpg|Layered mesas

52471 1835layers.jpg|Close view of layers
</gallery>

==Dunes==

[[File: ESP 055095 2170dunes.jpg|600pxr|Wide view of a field of dunes]]
Wide view of a field of dunes

Sand dunes have been found in many places on Mars. The presence of dunes shows that the planet has an atmosphere with wind, for dunes require wind to pile up the sand. Most dunes on Mars are black because of the weathering of the volcanic rock basalt.<ref>http://hirise.lpl.arizona.edu/ESP_016459_1830</ref> <ref>Michael H. Carr|title=The surface of Mars|url=https://books.google.com/books?id=uLHlJ6sjohwC|accessdate=21 March 2011|year=2006|publisher=Cambridge University Press|isbn=978-0-521-87201-0</ref> Black sand can be found on Earth on Hawaii and on some tropical South Pacific islands.<ref>https://www.desertusa.com/desert-activity/sand-dune-wind1.html</ref>
Sand is common on Mars due to the old age of the surface that has allowed rocks to erode into sand. Dunes on Mars have been observed to move many meters.<ref>https://www.youtube.com/watch?v=ur_TeOs3S64</ref> <ref>https://uanews.arizona.edu/story/the-flowing-sands-of-mars</ref>
In this process, sand moves up the windward side and then falls down the leeward side of the dune, thus caused the dune to go toward the leeward side (or slip face).<ref>Namowitz, S., Stone, D. 1975. earth science the world we live in. American Book Company. New York.</ref>
When images are enlarged, some dunes on Mars display ripples on their surfaces.<ref>https://www.jpl.nasa.gov/news/news.php?feature=6551</ref>

<gallery class="center" widths="380px" heights="360px">
ESP 044861 2225dunes.jpg|Wide view of dunes in Moreux Crater

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:55095 2170dunelinecolor.jpg|Close, color view of dunes, as seen by HiRISE under [[HiWish program]]

File:55095 2170dunelinecolor2.jpg|Close, color view of dunes

File:55095 2170dunelinecolor3.jpg|Close, color view of a dune

</gallery>

==Ring mold craters==

Ring Mold Craters are a kind of Impact crater that looks like a ring mold used in baking. They are believed to be caused by an impact into ice. The ice is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." Impacts into ice, warm the ice, and cause it to flow into the ring mold shape.

<gallery class="center" widths="380px" heights="360px">
ESP 037622 2200ringmolds.jpg|Ring mold craters on floor of a crater
ESP 037622 2200ringmoldfield.jpg|Ring mold craters of various sizes on floor of a crater
</gallery>

[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

<gallery class="center" widths="380px" heights="360px">

51139 2160ringmold.jpg|Close view of Ring-mold crater, as seen by HiRISE under [[HiWish program]]

</gallery>

<gallery class="center" widths="380px" heights="360px">

52260 2165ringmold.jpg|Ring-mold craters, as seen by HiRISE under HiWish program
52260 2165ringmoldclose.jpg|Close view of Ring-mold craters and brain terrain
</gallery>

<gallery class="center" widths="380px" heights="360px">
52602 2140ringmold.jpg|Close view of Ring-mold craters and brain terrain
52602 2140ringmoldclose.jpg|Close view of Ring-mold craters and brain terrain Rectangle shows size of football field for scale.

</gallery>

==Volcanoes under ice==

There is evidence that volcanoes sometimes erupt under ice, as they do on Earth at times. <ref>https://www.uahirise.org/ESP_071541_2200</ref> What seems to happen is that much ice melts, the water escapes, and then the surface cracks and collapses.<ref>Smellie, J., B. Edwards. 2016. Glaciovolcanism on Earth and Mars. Cambridge University Press.</ref> These exhibit concentric fractures and large pieces of ground that seemed to have been pulled apart. Sites like this may have recently had held liquid water, hence they may be fruitful places to search for evidence of life.<ref>Levy, J. 2017">Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185–194.</ref> <ref>University of Texas at Austin. "A funnel on Mars could be a place to look for life." ScienceDaily. ScienceDaily, 10 November 2016. <https://www.sciencedaily.com/releases/2016/11/161110125408.htm>.</ref>

<gallery class="center" widths="380px" heights="360px">
Image:25755concentriccracks.jpg|Large group of concentric cracks Location is Ismenius Lacus quadrangle. Cracks were formed by a volcano under ice.<ref>Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185–194.</ref>

25755 2200collapse.jpg|Tilted layers formed when ground collapsed, as seen by HiRISE, under [[HiWish program]]
25755 2200tiltedlayers.jpg|Tilted layers formed from ground collapse
25755 2200blocksforming.jpg|Mesas breaking up into blocks

</gallery>

<gallery class="center" widths="380px" heights="360px">

52049 2145cratercracks.jpg|Depression forming from a possible subsurface loss of material
</gallery>

==Mesas formed by ground collapse==

<gallery class="center" widths="380px" heights="360px">
ESP 043201 2160blocks.jpg|Group of mesas, as seen by HiRISE under HiWish program Oval box contains mesas that may have moved apart.

43201 2160blocksbreakup.jpg|Mesas breaking up forming straight edges, as seen by HiRISE under HiWish program
</gallery>

==Fractures forming blocks==

In places large fractures break up surfaces. Sometimes straight edges are formed and large cubes are created by the fractures.

<gallery class="center" widths="380px" heights="360px">
44757 2185wide.jpg|Wide view of mesas that are forming fractures
44757 2185zoom.jpg|Enlarged view of a part of previous image The rectangle represents the size of a football field.
44757 2185closeleft.jpg|Close-up of blocks being formed

44757 2185blocks.jpg|Close-up of blocks being formed The rectangle represents the size of a football field, so blocks are the size of buildings.
44757 2185cosefractures.jpg|Close-up of blocks being formed Many long fractures are visible on the surface.

ESP 045377 2170odd.jpg|Wide view showing light-toned feature that is breaking into blocks

45377 2170blocks.jpg|Close view showing blocks being formed Note: this is an enlargement of the previous image. Box represents the size of a football field.

File:55517 2170rocksbreakingcolor.jpg|Color view of rocks breaking apart
</gallery>

==Exhumed craters==

Some features on Mars seem to be in the process of being uncovered. So, the thought is that they formed, were covered over, and now are being exhumed as material is being taken away by erosion. These features are quite noticeable with craters. When a crater forms, it will destroy what's under it and leave a rim and ejecta. In the example below, only part of the crater is visible. If the crater came after the layered feature, the impact that formed the crater would have removed part of the layered structure.

<gallery class="center" widths="380px" heights="360px">
File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.

</gallery>

==Mounds==

<gallery class="center" widths="380px" heights="360px">
ESP 052339 2275mounds.jpg|Wide view of field of mounds near pedestal crater
ESP 052339 2275moundsclosecolor.jpg|Close, color view of mounds, as seen by HiRISE under HiWish program

File:ESP 053260 2185mounds.jpg|Row of mounds Arrows point to some of the mounds.
File:ESP 055978 2270mounds.jpg|Lines of mounds
</gallery>

==Landslide==

<gallery class="center" widths="380px" heights="360px">

File:ESP 057191 2150landslide.jpg|Landslide, as seen by HiRISE under HiWish program

File:57191 2150landslideclose.jpg|Close view of landslide

ESP 047262 2145landslide.jpg|Landslides

</gallery>

==Other images from Ismenius Lacus quadrangle==

[[File:56663 2200brains.jpg|600pxr|Close view of honeycomb shapes and brain terrain, as seen by HiRISE under [[HiWish program]]]]
Close view of honeycomb shapes and brain terrain, as seen by HiRISE under [[HiWish program]]

<gallery class="center" widths="380px" heights="360px">

Image:25781pitsmediumview.jpg|Field of pits

43201 2160dikes.jpg|Possible dike

45377 2170troughinsidetroughs.jpg|Pits and troughs Pits may have formed from water/ice leaving the ground.

ESP 045415 2220boulders.jpg|Boulders

ESP 052932 2255mudvolcanoes.jpg|Possible mud volcanoes

File:57825 2275conesclose.jpg|Close view of cones

51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

File:ESP 054870 2270snake.jpg|Ridge This ridge may be an esker. Eskers began as streams under glaciers.

</gallery>

[[File:ESP 053893 2130ridges.jpg|600pxr|Ridges]]
Ridges

==See also==

*[[Dark slope streaks]]
*[[Geography of Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[HiWish program]]
*[[How are features on Mars Named?]]
*[[Glaciers on Mars]]
*[[Layers on Mars]]
*[[Mars Global Surveyor]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Oceans on Mars]]
*[[Periodic climate changes on Mars]]
*[[Rivers on Mars]]
*[[Sublimation landscapes on Mars]]

== External links ==

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]

==References==
{{reflist|colwidth=30em}}

Glaciers on Mars

2023-04-15T15:00:23Z

Suitupandshowup: /* Lobate Debris Aprons */ added image

{{Mars atlas}}
Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Since the 60’s, as our spacecraft have studied Mars with more and more advanced cameras and other instruments, we have found more and more evidence for glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 | bibcode=2005Icar..174..321A</ref> On Mars these glaciers are covered with rock and dust debris a few meters to a few tens of meters thick. Although Mars today seems too dry for any glaciers, this covering material has protected the underlying ice. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> One would think that under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>

==Water for Future Colonists==

The discovery of ice on Mars is important because future colonists may be able to tap the ice for water. Besides the obvious uses of water to humans, water can be broken down with electricity to form hydrogen and oxygen. Hence, people living on Mars could be supplied with oxygen to breathe and hydrogen for fuel. We have known for many decades that the ice caps, called the polar layered deposits, contain ice, but they are far away from where it is easy to land rockets. Glaciers on the planet are much closer to the equator and widespread about the planet. Perhaps, the task of obtaining water will be done with automated machines. Already scientists here on Earth are building devices that can drill into the ground and melt any ice for water.<ref> https://www.nasa.gov/press-release/nasa-s-mars-ice-challenge-follow-the-water</ref> <ref> ↑ http://triblive.com/news/education/career/13040517-74/cmu-team-finalist-for-nasas-mars-ice-challenge-to-drill-for-water</ref> Recent studies have sought to determine the nature of these covering layers to find out how best to extract water.<ref> Baker, D., L. Carter. In press. Probing supraglacial debris on Mars 1: Sources, thickness, and stratigraphy. Icarus. https://doi.org/10.1016/j.icarus.2018.09.001</ref> Our advanced cameras on satellites orbiting the Red Planet have mapped the exact locations of hundreds of glaciers and glacier-like features that may all contain useable ice. We know where the water is!
From early on, images from satellites have shown features that resembled glaciers on the Earth. Of particular significance was the angle at the end of the glacier. The angle was far steeper than geologic features like landslides. Large stretches of landscape called “fretted terrain,” after the forehead of someone who worries or frets show signs of glacier activity. This terrain is characterized by wide, flat floored valleys surrounded by steep cliffs. The floors contained lines in early Viking photographs.<ref>Squyres, S. 1978. Martian Fretted Terrain: Flow of Erosional Debris. Icarus: 34, 600-613.</ref> Many isolated mesas are present. Furthermore, mesas are surrounded by wide aprons of material that today we know to be debris covered glaciers.

==Real Glaciers==

<gallery class="center" widths="380px" heights="360px">
File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.
File: Wikielephantglacier.jpg|Glacier in Greenland
</gallery>

With better cameras, it was observed that some mesas had what resembled glaciers in the valleys. A big advance in understanding Martian geology came when the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor gave us exact elevations for the whole planet; from then on, we could figure out slopes. Where the land was tilted, the glacier-forms moved down slope. Also, researchers observed that when the glacier left the valley and reached a wider, flatter place, it spread out, just as glaciers on Earth do. In some craters there are large glaciers shaped like giant tongues, so they have been called tongue-shaped glaciers. <ref>Forget, F., et al. 2006. Planet Mars Story of Another World. Praxis Publishing, Chichester, UK. ISBN|978-0-387-48925-4</ref>

[[File:Mars_MGS_colorhillshade_mola_1024.jpg |thumb|300px|center|Topographic map produced with MOLA measurements This map showed that glacial features move downhill.]]

[[File:Tongueismenius.jpg |thumb|300px|left| Glacier shaped like a giant tongue, as seen by HiRISE under HiWish program ]]

==Lobate Debris Aprons==

So for sure many things look like glaciers, but looks can be deceiving. Conclusive proof came after radar studies confirmed that many of these features were actually ice with only a thin surface covering. Shallow Subsurface Radar (SHARD) was the radar system on board the Mars Reconnaissance Orbiter that was used. It found that features, called lobate debris aprons (LDA’s), around mesas were actually glaciers, as had long been expected. <ref name="Plaut, J. 2008">Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> Ice was found both in the southern and northern hemispheres. <ref>cite journal | last1 = Holt | first1 = J. | last2 = Safaeinili | first2 = A. | last3 = Plaut | first3 = J. | last4 = Head | first4 = J. | last5 = Phillips | first5 = R. | last6 = Seu | first6 = R. | last7 = Kempf | first7 = S. | last8 = Choudhary | first8 = P. | last9 = Young | first9 = D. | last10 = Putzig | first10 = N. | last11 = Biccari | first11 = D. | last12 = Gim | first12 = Y. | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322| issue = | pages = 1235–1238| doi = 10.1126/science.1164246 | pmid=19023078|</ref> <ref>cite journal | last1 = Plaut | first1 = J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J. | last4 = Phillips | first4 = R. | last5 = Head | first5 = J. | last6 = Seu | first6 = R. | last7 = Putzig | first7 = N. | last8 = Frigeri | first8 = A. | year = 2009 | title = Radar evidence for ice in lobate debris aprons in the midnorthern latitudes of Mars | url = | journal = Geophys. Res. Lett. | volume = 36| issue = | page = | doi = 10.1029/2008GL036379 |</ref> <ref>Holt, J., et al. 2008. Radar Sounding Evidence for Ice within Lobate Debris Aprons, near Hellas Basin, Mid-southern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2441.pdf</ref>

<gallery class="center" widths="380px" heights="360px">
[[Image: Mars Reconnaissance Orbiter spacecraft model.png |thumb|200px|right|Artist view of Mars Reconnaissance Orbiter ]]
File:800px-Wideviewlda42n18e.jpg|Lobate debris apron (LDA) around a mesa Radar proved that a LDA is mostly ice.
</gallery>

[[File:77699 2215contextldactx.jpg|600pxr|Wide and close views of LDA]]

Wide and close views of LDA

==Lineated Valley Fill==

Another ice-rich feature is called lineated valley fill (LVF). <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref> https://www.uahirise.org/ESP_026414_2205</ref>
It covers many of the wide, flat valley floors of fretted terrain. Probably formed from the interaction of glaciers coming out of valleys and of mesas eroding, it has similar surface appearance of other supposed glaciers, including LDA. It looks like the human brain. Since the material covering ice is shaped into something resembling the human brain, it is named brain terrain. Two types, open and closed have been identified. The closed still holds an ice core. Brain terrain starts to form when cracks occur on an ice-rich surface. [[Sublimation]] along the cracks turns the cracks into small valleys. Regions called Nilosyrtis Mensae, Protonilus Mensae and Deuteronilus Mensae display many examples of LVF. The Ismenius Lacus quadrangle and Hellas quadrangle contain many valleys exhibiting lineated valley fill.<ref>Mellon, M. 1997. Small-scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost. J. Geophysical Res: 102. 25,617-625,628.</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref> <ref name="Souness, C 2013">cite journal | author = Souness C., Hubbard B. | year = 2013 | title = An alternative interpretation of late Amazonian ice flow: Protonilus Mensae, Mars | url = | journal = Icarus | volume = 225 | issue = | pages = 495–505 | doi=10.1016/j.icarus.2013.03.030 |</ref> <ref name="Noach">cite journal |author1=Head, J. |author2=D. Marchant |lastauthoramp=yes| date = 2006 | title = Modification of the walls of a Noachian crater in northern Arabia Terra (24E, 39N) during mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of lobate debris aprons and their relationships to lineated valley fill and glacial systems | journal = Lunar Planet. Sci | volume = 37 | page = Abstract # 1126</ref> <ref>cite journal | author = Kress, A., J. Head | date = 2008 | title = Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice | journal = Geophys. Res. Lett. | volume = 35 | page = L23206–8 | doi=10.1029/2008gl035501|</ref> <ref>cite journal | author = Baker, D. | date = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | journal = Icarus | volume = 207 | pages = 186–209 | doi = 10.1016/j.icarus.2009.11.017 | last2 = Head | first2 = James W. | last3 = Marchant | first3 = David R. </ref> <ref>cite journal |author1=Kress., A. |author2=J. Head |lastauthoramp=yes| date = 2009 | title = Ring-mould craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age | journal = Lunar Planet. Sci | volume = 40 | page = abstract 1379</ref>

<gallery class="center" widths="380px" heights="360px">
File:56544 2200lvfbrains.jpg|Wide view of Lineated Valley Fill
File:56544 2200lvf.jpg|Close view of Lineated Valley Fill The location is the Ismenius Lacus quadrangle.
File:54527 2225brainsclosecolor.jpg|Close view of brain terrain Brain terrain covers many types of Martian glaciers.
File:ESP 053642 2225brainslabeled.jpg|Closed cell brain terrain still contains a core of ice. When the ice leaves it becomes open cell brain terrain.
</gallery>

==Concentric Crater Fill==

Concentric crater fill (CCF) is a third easily identifiable landscape that is covered with brain terrain and loaded with water. Craters with CCF are shallow. Even though they started out with a deep bowl shape, today they are full. We know how deep the crater was when formed because crater studies have found a relationship between the diameter of a crater and its original depth. For example, in many parts of Mars the diameter of a crater is 10 times the depth.<ref>http://adsabs.harvard.edu/full/1993mppf.proc....1B</ref> So if see that a crater is 10 km across, we know that it started out being 1 km deep. These craters may be big, but they are shallow. Scientists believe they are full of dust and ice. As material moves down crater walls toward the center, concentric lines of brain terrain are created. <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref> <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust .
File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed.
</gallery>

==Source of Ice==

Multiple studies imply there is plenty of ice on Mars. Ice is abundant from about 30 degrees latitude up to the poles. <ref name="HeadDistn">cite journal | last1 = Head | first1 = J. W. | display-authors = 1 | last2 = et al | year = 2006 | title = Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change | url = | journal = Earth and Planetary Science Letters | volume = 241 | issue = 3| pages = 663–671 | doi=10.1016/j.epsl.2005.11.016 |</ref> <ref>Kieffer, H., et al. (eds). 1992. Mars. University of Arizona Press. Tucson. ISBN 0-8165-1257-4</ref> How did it get there? It is now widely believed that snow and ice-coated dust drops from the sky when the climate of Mars changes--as it frequently does. <ref>cite journal | last1 = Touma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = | pages = 1294–1297 | doi=10.1126/science.259.5099.1294 | pmid=17732249|</ref> <ref name="ReferenceB">cite journal | last1 = Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = | pages = 343–364 | doi=10.1016/j.icarus.2004.04.005 |</ref> Calculations reveal that the tilt of Mars drastically changes due to the lack of a large moon to stabilize it.<ref>https://www.uahirise.org/hipod/ESP_034132_1750</ref> When the tilt changes, the climate changes. At times, the ice in the polar deposits leaves and goes to mid-latitudes.<ref>http://hirise.lpl.arizona.edu/PSP_002917_2175</ref> <ref>Forget, F., et al. 2006. Planet Mars Story of Another World. Praxis Publishing, Chichester, UK. ISBN|978-0-387-48925-4</ref> During this time, ice in the cap sublimates, and thick snow falls in mid-latitudes — the zones where concentric crater fill, lineated valley fill and lobate debris aprons are common.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0 </ref> <ref name="obliq">cite journal | author = Head, J. | date = 2006 | title = Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for late Amazonian obliquity-driven climate change | journal = Earth Planet. Sci. Lett. | volume = 241 | pages = 663–671 |doi=10.1016/j.epsl.2005.11.016 | issue = 3–4| last2 = Marchant | first2 = D.R. | last3 = Agnew | first3 = M.C. | last4 = Fassett | first4 = C.I. | last5 = Kreslavsky | first5 = M.A. </ref> <ref>cite journal | author = Levy, J. | display-authors = etal | date = 2007 | title = Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary | journal = J. Geophys. Res. | volume = 112 | doi=10.1029/2006je002852 |</ref> <ref>Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. </ref> It is deposited as something called latitude dependent mantle. Over time, some ice disappears and leaves a covering lag deposit that prevents further loss of ice. <ref name="Mellon, M. 1995">cite journal | last1 = Mellon | first1 = M. | last2 = Jakosky | first2 = B. | year = 1995 | title = The distribution and behavior of Martian ground ice during past and present epochs | url = | journal = J. Geophys. Res. | volume = 100 | issue = | pages = 11781–11799 | doi=10.1029/95je01027 |</ref> <ref name="Mellon, M. 1995"/> <ref>cite journal | last1 = Schorghofer | first1 = N | year = 2007 | title = Dynamics of ice ages on Mars | url = | journal = Nature | volume = 449 | issue = | pages = 192–194 | doi=10.1038/nature06082 | pmid=17851518|</ref> Also, dust and other debris collect on the surface. Together, these coverings help to build up an ice-rich, long lasting smooth mantle that can eventually generate glaciers. If it gets thick enough, the ice mass will be pulled downhill by gravity. On Earth, glaciers often melt at the base. The resulting water helps the glacier slide. However, glaciers also move from internal movement of ice crystals sliding over each other. It flows like a soft plastic.<ref> http://www.geography-site.co.uk/pages/physical/glaciers/origin.html</ref> <ref>Earth Science. 2001. Holt Science &Technology. New York</ref> This plastic movement will not change the shape of the ground under the glacier; however, the glacier will still carry debris and make structures called moraine.

<gallery class="center" widths="380px" heights="360px">
46444 2225mantle.jpg|Latitude dependent mantle
File:ESP 028352 2245glacier.jpg|Glacier that has lost much of its ice, but has built moraines
File:Moraines52720 2250.jpg|Old Glacier with multiple moraines indicated with arrows When the glacier retreated it stopped at times and left behind a moraine. Material is still transported to the end (snout) of a glacier when it is not advancing.
</gallery>

Moraines are common on Mars. <ref>Milliken, R., J. Mustard, D. Goldsby. 2003. Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images. J. Geophys. Res. 108. </ref> It is believed that most glaciers on Mars are “cold based” that is they do not melt. Remember, under current conditions ice does not melt, rather it changes directly to a gas in a process called [[sublimation]]. We do not know if any ice melted in the past. We may understand the situation much better after we study data from the [[InSight Mission]] which landed on Mars at the end of November 2018. InSight will measure the heat flow. A combination of high heat flow and pressure from thick ice, may have generated sufficient heat to cause some melting.

[[File:PIA17358-MarsInSightLander-20140326.jpg|600pxr|Labeled drawing of InSight Lander]]

==Other Possible Glaciers==

Besides features that look like terrestrial glaciers, LDM, LVF, and CCF; there are other shapes that may be glaciers. <ref>Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127</ref> <ref>Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128</ref> <ref>Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671</ref> <ref>Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33</ref> They appear as curved ridges and have been called various names by different researchers. Some of the names are Viscus Flow Features (VFF), arcuate ridges, Glacial-like Flows (GLF), Glacier-like Forms (GLF), and Moraine-like Ridges (MLR). <ref> Milliken, R., et al. 2003. Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images. Journal of Geophysical Research: 108. Doi:10.1029/2002JE002005</ref> <ref>Berman, D., et al. 2005. The role of arcuate ridges and gullies in the degradation of craters in the Newton Basin regions of Mars. Icarus: 178, 465-486.</ref> <ref>cite journal
| last1 = Arfstrom | first1 = J
| last2 = Hartmann | first2 = W. | year = 2005
| title = Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships
| url = | journal = Icarus | volume = 174 | issue = | pages = 321–335
| doi=10.1016/j.icarus.2004.05.026 | </ref> <ref name="Hubbard B. 2011">cite journal
| last1 = Hubbard | first1 = B.
| last2 = Milliken | first2 = R.
| last3 = Kargel | first3 = J.
| last4 = Limaye | first4 = A.
| last5 = Souness | first5 = C.
| year = 2011 | title = Geomorphological characterisation and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars
| url = | journal = Icarus | volume = 211 | issue = | pages = 330–346
| doi=10.1016/j.icarus.2010.10.021 |</ref> <ref name="Hubbard B. 2011"/> <ref>http://www.antarcticglaciers.org/glacial-geology/glaciers-mars/</ref> Most lie in impact craters. Gullies are associated with many of them. These curved ridges may be created as snow and ice accumulate high on crater walls until gravity pulls them down. As they slide down, they may push material into ridges.

<gallery class="center" widths="380px" heights="360px">
File:Gullies and tongue-shaped glacier.jpg|Gullies and ridges that may be the remains of old glaciers Glaciers may have dropped moraine debris or pushed floor material into ridges.
File:44410 2195glacier.jpg|Ridge downslope from a gully This ridge in a crater may be created by a glacier.
</gallery>

==Glaciers on Volcanoes==

Most major Martian volcanoes display evidence of past glaciation. <ref name="HeadTropical">cite journal | last1 = Head | first1 = J. W. | display-authors = 1 | last2 = et al | year = 2005 | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal = Nature | volume = 434 | issue = 7031| pages = 346–351 | doi=10.1038/nature03359 | pmid=15772652|</ref> <ref name="SheanPavonis">cite journal | last1 = Shean | first1 = David E. | title = Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit | journal=Journal of Geophysical Research | volume = 110 | date = 2005 | doi = 10.1029/2004JE002360 | </ref> <ref name="HeadMarchantArsia">cite journal | last1 = Head | first1 = James W. | last2 = Marchant | first2 = David R. | year = 2003 | title = Cold-based mountain glaciers on Mars: western Arsia Mons | url = | journal = Geology | volume = 31 | issue = 7| pages = 641–644 | doi=10.1130/0091-7613(2003)031<0641:cmgomw>2.0.co;2|</ref>
<ref name="Hauber, E. 2005">Cite journal|author=Hauber, E. |date=2005 |title=Discovery of a flank caldera and very young glacial activity at Hecates Tholus, Mars |journal=Nature |volume=434 |pages=356–61|pmid=15772654|issue=7031|doi=10.1038/nature03423 |last2=Van Gasselt |first2=Stephan |last3=Ivanov |first3=Boris |last4=Werner |first4=Stephanie |last5=Head |first5=James W. |last6=Neukum |first6=Gerhard |last7=Jaumann |first7=Ralf |last8=Greeley |first8=Ronald |last9=Mitchell |first9=Karl L. |last10=Muller |first10=Peter |last11=Co-Investigator Team |first11=The Hrsc </ref> <ref>Scanlon, K., J. Head, D. Marchant. 2015. REMNANT BURIED ICE IN THE ARSIA MONS FAN-SHAPED DEPOSIT, MARS. 46th Lunar and Planetary Science Conference. 2266.pdf</ref>
<ref name="ReferenceA">cite journal | last1= Shean | first1= David E. | last2= Head | first2= James W. | last3= Fastook | first3= James L. | last4= Marchant | first4= David R. | title= Recent glaciation at high elevations on Arsia Mons, Mars: Implications for the formation and evolution of large tropical mountain glaciers| page= E03004 | date= 2007 | issue= E3 | volume= 112 | doi = 10.1029/2006JE002761 | journal= Journal of Geophysical Research | url=http://www.planetary.brown.edu/pdfs/3281.pdf | format = PDF | </ref> <ref name="Shean, D. 2005">Cite journal|author=Shean, D. |display-authors=etal |date=2005 |title=Origin and evolution of a cold-based mountain glacier on Mars: The Pavonis Mons fan-shaped deposit |journal=Journal of Geophysical Research |volume=110|issue=E5 |page=E05001 | doi = 10.1029/2004JE002360 |</ref> <ref name="Basilevsky, A. 2006">Cite journal|author=Basilevsky, A. |date=2006 |title=Geological recent tectonic, volcanic and fluvial activity on the eastern flank of the Olympus Mons volcano, Mars |journal=Geophysical Research Letters |volume=33 |issue=13 |pages=13201, L13201 |doi=10.1029/2006GL026396 |last2=Werner |first2=S. C. |last3=Neukum |first3=G. |last4=Head |first4=J. W. |last5=Van Gasselt |first5=S. |last6=Gwinner |first6=K. |last7=Ivanov |first7=B. A. </ref> Scientists now believe that glaciers exist on many of the volcanoes in Tharsis, including Olympus Mons, Ascraeus Mons, and Pavonis Mons.<ref>https://www.scienceinschool.org/2014/issue28/mars_glaciers</ref> <ref>cite journal | last1=Shean | first1=David E. | title=Origin and evolution of cold-based tropical mountain glacier on Mars: the Pavonis Mons fan-shaped deposit | journal=Journal of Geophysical Research | volume=110 | year=2005 | doi= 10.1029/2004JE002360 |</ref> <ref>cite journal | last1=Fassett | first1=C | last2=Headiii | first2=J | title=Valley formation on martian volcanoes in the Hesperian: Evidence for melting of summit snowpack, caldera lake formation, drainage and erosion on Ceraunius Tholus | url=http://www.planetary.brown.edu/pdfs/3408.pdf | format=PDF | journal=Icarus | volume=189 | pages=118–135 | year=2007| doi = 10.1016/j.icarus.2006.12.021 |</ref>
<ref>cite journal | last1= Plaut | first1= Jeffrey J. | last2= Safaeinili | first2= Ali | last3= Holt | first3= John W. | last4= Phillips | first4= Roger J. | last5= Head | first5= James W. | last6= Seu | first6= Roberto | last7= Putzig | first7= Nathaniel E. | last8= Frigeri | first8= Alessandro | title= Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars | journal= Geophysical Research Letters | volume= 36 | issue= 2 | pages= | year= 2009 | doi = 10.1029/2008GL036379 |url=http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2290.pdf | format=PDF |</ref> <ref>cite journal | title= Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars | url=http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2441.pdf | format=PDF | journal = Lunar and Planetary Science |volume=XXXIX | pages = 2441 |year=2008 |last1= Holt | first=J.W.| last2 = Safaeinili | first2 = A. | last3 = Plaut | first3 = J. J. | last4 = Young | first4 = D. A. | last5 = Head | first5 = J. W. | last6 = Phillips | first6 = R. J. | last7 = Campbell | first7 = B. A. | last8 = Carter | first8 = L. M. | last9 = Gim | first9 = Y. | last10 = Seu | first10 = R. | author11 = Sharad Team </ref >Many large mountains on Earth also have glaciers. It is cold on mountain tops. Snow often falls heavily there; therefore, one would expect glaciers on Martian volcanoes.

==Vast Ice Sheets==

Besides smaller glaciers around mesas, in craters, and on mountains, Mars may have had giant ice sheets, twice the area of the state of Texas.<ref>cite journal | last1 = Scanlon | first1 = K. | display-authors = 1 | last2 = et al | year = 2018 | title = | url = | journal = Icarus | volume = 299 | issue = | pages = 339–363| doi = 10.1016/j.icarus.2017.07.031</ref> <ref>Allen, C. 1979. Volcano-ice interactions on Mars. ''J. Geophys. Res.: Solid Earth (1978–2012)'', 84 (B14), 8048-8059.</ref> <ref>Howard, 1981</ref> <ref>cite journal | last1 = Kargel | first1 = J. | last2 = Strom | first2 = R. | year = 1992 | title = Ancient glaciation on mars | url = | journal = Geology | volume = 20 | issue = 1| pages = 3–7| doi = 10.1130/0091-7613(1992)020<0003:AGOM>2.3.CO;2 </ref> <ref>Head, J, S. Pratt. 2001. Extensive Hesperian-aged south polar ice sheet on Mars: Evidence for massive melting and retreat, and lateral flow and pending of meltwater. J. Geophys. Res.-Planet, 106 (E6), 12275-12299.</ref> Some researchers have estimated that one ice sheet was nearly a mile thick. Near the South Pole in the Dorsa Argentea Formation are tangles of ridges that resemble what is left from streams under glaciers. These are called eskers. In the same general area are shapes, now named Sisyphi Montes, that look like what is formed on Earth when volcanoes erupt under glaciers; they have steep walls and flat tops.<ref> Ghatan, G.J. and J.W. Head, III. 2002. Candidate subglacial volcanoes in the south polar region of Mars: morphology, morphometry, and eruption conditions. J. Geophys. Res., 107(E7), 5048. (10.1029/2001JE001519.)</ref> <ref> Ghatan, G.J., J.W. Head, III and S. Pratt. 2003. Cavi Angusti, Mars: characterization and assessment of possible formation mechanisms. J. Geophys. Res., 108(E5), 5045. (10.1029/2002JE001972.) </ref> <ref>Head, J., L. Wilson. 2007. Heat Transfer in Volcano-Ice Interactions on Mars: Synthesis of Environments and Implications for Processes and Landforms. Annals of Glaciology. 45</ref> These features are common in Iceland. Earlier studies support the idea that glaciers on Mars may have been much thicker and more extensive in the past. It appears in many places that LVF has dropped, probably because it has lost ice.<ref> Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Letters. Doi:10.1016/j.epsl.2009.08.031</ref> <ref> Levy, J., et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. Journal of Geophysical Research: 112, E08004</ref> <ref>Head, J., et al. 2006. Modification of the dichotomy boundary on Mars by Amazonian mi-latitude regional glaciation. Geophysical Research Letters: 33, L08S03</ref> <ref> Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36, 411-414.</ref>

[[File:R0502109dorsaargentea.jpg|thumb|300px|left|Possible eskers indicated by arrows. Eskers form under glaciers.]]

== References ==
{{reflist|colwidth=30em}}

==See also==

* [[High Resolution Imaging Science Experiment (HiRISE)]]

* [[InSight Mission]]
* [[Martian features that are signs of water ice ]]
* [[Periodic climate changes on Mars]]
* [[Tharsis]]
* [[Water]]

== External links ==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

*[https://www.youtube.com/watch?v=RYG-HLr33CM Jim Secosky - Martian Geology - 16th Annual International Mars Society Convention]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]
* [https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground
* High resolution [https://www.flickr.com/photos/seandoran/30604739258/ flyover video] by Seán Doran of a glacier in Protonilus Mensae, based on NASA [https://www.uahirise.org/ESP_018857_2225 digital terrain model]; see [https://www.flickr.com/photos/seandoran/albums/72157677941945560 album] for more
* [https://www.youtube.com/watch?v=j8P9pE8CYgI Glaciers on Mars?]

* [https://www.sciencedirect.com/science/article/pii/S0019103520305121#f0010 Gallagher. c. et al. In press 2020. Landforms indicative of regional warm based glaciation, Phlegra Montes, Mars. Icarus ]

[[Category: Geologic Processes]]

Martian features that are signs of water ice

2023-04-15T14:55:17Z

Suitupandshowup: /* Lobate Debris Aprons */

How to find water on Mars

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

INTRODUCTION
Finding sources of water on Mars is necessary for future colonists. Studies with orbiting spacecraft have provided a great deal of evidence pointing to where water ice is located. Decades ago, theoretical studies showed that ice could exist under a cover of material that needed to be very thick near the equator, but at higher latitudes could be right under the surface.<ref>Rossbacher, L and S. Judson. 1981. Ground Ice on Mars: Inventory, Distribution, and Resulting Landforms. Icarus: 45, 39-59.</ref> Instruments onboard the Mars Odyssey measured the depth to this ice layer all over the planet.

[[Image: Mars Odyssey spacecraft model.png |thumb|200px|left|Artist view of Mars Odyssey]]

These measurements closely matched what the early theories had predicted. The Phoenix lander’s rockets blew away a thin cover of dirt to reveal the top of an ice layer.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> Also, by way of frequent pictures from Phoenix, we watched chunks of ice sublimate into the atmosphere. On Mars today, any exposed ice changes directly into a gas and mixes with the atmosphere in the process called [[sublimation]].

[[Image: Phoenix landing.jpg |thumb|200px|right|Artist view of Phoenix landing]]

[[File:PIA10741 Possible Ice Below Phoenix.jpg|thumb|200px|right|View under Phoenix spacecraft Bright regions are probably top of an ice sheet.]]

We also observed this process through HiRISE photos of ice first being exposed in new craters and then disappearing.

[[Image: Iceincraterscomparison.jpg|thumb|200px|left|Ice in crater Location: 43.286° N and 164.213°E]]

Thanks to the many satellites going around Mars with advanced instruments, we now have a list of features that are signs of easily obtainable underground ice. The shapes of some landscapes are similar to those on the earth that we know contain ice. Radar studies with the SHAllow RADar instrument (SHARD) on board the Mars Reconnaissance Orbiter ( MRO) have found large deposits of ice under relatively thin layers of debris cover for some of these features .<ref> Plaut, J., A. Safaeinili, J. Holt, R. Phillips, J. Head, J., R. Seu, N. Putzig, A. Frigeri. 2009. Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars. Geophys. Res. Lett. 36. doi:10.1029/2008GL036379.</ref> <ref> Holt, J., A. Safaeinili, J. Plaut, J. Head, R. Phillips, R. Seu, S. Kempf, P. Choudhary, D. Young, N. Putzig, D. Biccari, Y. Gim. 2008. Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars. Science 322. doi:10.1126/science.1164246 </ref> The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument onboard MRO has been able to detect spectroscopic signs of water in certain landscapes. The ice caps contain vast resovors of ice, but traveling to the poles is a long way to go for this precious resource. This article will display many landscapes that probably contain easily obtained water ice that are much closer than the poles.

[[Image: Mars Reconnaissance Orbiter spacecraft model.png |thumb|200px|right|Artist view of Mars Reconnaissance Orbiter ]]
[[Image: MRO CRISM prelaunch 2.jpg |thumb|200px|left|CRISM—identifies ice and other minerals]]

===Triangular depressions===

In early 2018, researchers released information about large amounts of ice found under only a few meters of soil. These places are easily seen as triangular depressions with one steep wall that faces the pole.<ref>https://www.uahirise.org/ESP_074914_1225</ref> These exposed ice sheets as thick as 100 meters were discovered by using instruments on board the Mars Reconnaissance Orbiter (MRO). Much evidence of underground ice in vast regions of Mars has already been found by past studies, but this study found that the ice was only covered by a layer of about 1 or 2 meters thick of Martian soil.<ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> Shane Byrne, one of the co-authors remarked that future colonists of the Red Planet would be able to gather up ice with just a bucket and shovel.<ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref> The fact that water-ice makes up the layers was confirmed by Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the [[Mars Reconnaissance Orbiter]] (MRO). The spectra gathered by CRISM showed strong signals of water.<ref>Colin M. Dundas, et al. ''Science'', 12 January 2018. Vol. 359, Issue 6372, pp. 199-201.</ref>

The sites are at latitudes from about 55 to 58 degrees north and south of the equator, suggesting that there is shallow ground ice under roughly a third of the Martian surface.<ref> Steep Slopes on Mars Reveal Structure of Buried Ice. NASA Press Release. 11 January 2018.</ref>

<gallery class="center" widths="380px" heights="360px">
ESP 045290 2350triangulardepression.jpg|Wide view of triangular depressions with ice under thin cover
45290 2350icelayerscloseer.jpg|Close view of depression, as seen by HiRISE under HiWish program Arrows indicate where there is a very thin, 1-2 meter covering on what is believed to be ice.<ref>https://www.uahirise.org/ESP_071573_2350</ref>
</gallery>

== Scalloped topography==

[[Image: ESP 037461 2255scallopstop.jpg|600pxr|Scalloped ground, as seen by HiRISE under HiWish program]]

Scalloped ground, as seen by HiRISE under HiWish program

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is particularly prominent in the region of Utopia Planitia<ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> in the northern hemisphere and in the region of Peneus and Amphitrites Patera in the southern hemisphere.<ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. A typical scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> This topographic asymmetry is probably due to differences in insolation. Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation. Sublimation is where a solid changes directly into a gas without going through a liquid phase. Dry ice on the Earth changes directly to a gas; but usually on Earth, ice will melt first to form a liquid phase before turning into a gas. This process is common in the thin Martian atmosphere.
In the fall of 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars.<ref>http://www.space.com/34811-mars-ice-more-water-than-lake-superior.html</ref> The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.<ref> "Lake of frozen water the size of New Mexico found on Mars – NASA". The Register. November 22, 2016 name="NASA-20161122"</ref> The volume of water ice in the region were based on measurements from the ground-penetrating radar instrument on Mars Reconnaissance Orbiter, called SHARAD. From the data obtained from SHARAD, a dielectric constant was determined. The dielectric constant value was consistent with a large concentration of water ice.<ref>Bramson, A, et al. 2015. Widespread excess ice in Arcadia Planitia, Mars. Geophysical Research Letters: 42, 6566-6574</ref> <ref>https://planetarycassie.com/2016/11/04/widespread-thick-water-ice-found-in-utopia-planitia-mars/</ref> <ref>Stuurman, C., et al. 2016. SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars. Geophysical Research Letters: 43, 9484_9491.</ref>

<gallery class="center" widths="380px" heights="360px">

File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle

File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia

</gallery>

==Glacial Features==

Over the years of satellite observations several features have been observed that look like glacial features that is it looks like ice is flowing under a thin cover of debris. Although ice is not stable at many latitudes of Mars, ice could survive for long periods under a few meters of dirt and rock. Many of these supposed regions of underground ice generally begin around 30 degrees of latitude on both sides of the equator. In other words latitudes greater than 30 degrees may have glaciers.<ref> Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>
Some bear an uncanny resemblance to alpine or mountain glaciers of the Earth. These, supposed alpine glaciers, have been called glacier-like forms (GLF) or glacier-like flows (GLF). <ref> Arfstrom, J and W. Hartmann. 2005. Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships. Icarus 174, 321-335.</ref> <ref> Hubbard B., R. Milliken, J. Kargel , A. Limaye, C. Souness . 2011. Geomorphological characterization and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars Icarus 211, 330–346 </ref> Another, more general term sometimes seen in the literature is viscous flow features (VFF). <ref> Hubbard B., R. Milliken, J. Kargel , A. Limaye, C. Souness . 2011. Geomorphological characterization and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars Icarus 211, 330–346 </ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° E (309.5 W)
File: Wikielephantglacier.jpg|Glacier in Greenland Notice how it resembles the glacier on Mars.
File:ESP 047193 1440tongues.jpg|Tongue-shaped glaciers Lat: 35.6° S Long: 109.7° E (250.3 W)

</gallery>

Based on current models of the Martian atmosphere, ice should not be stable if exposed at the surface in the mid-Martian latitudes.<ref>Williams, K. E.; et al. (2008). "Stability of mid-latitude snowpacks on Mars". Icarus. 196 (2): 565–577.</ref> It is thus thought that most glaciers must be covered with a layer of rubble or dust preventing free transfer of water vapor from the subliming ice into the air.<ref>Plaut, J.J.; Safaeinili, A.; Holt, J.W.; Phillips, R.J.; Head, J.W.; Sue, R.; Putzig, A. (2009). "Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophys. Res. Lett. 36: L02203.</ref> <ref>Head, J.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; et al. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–350.</ref> In the recent geological past, the climate of Mars may have been different in order to allow the glaciers to grow stably at these latitudes.<ref> Head, J. W.; et al. 2006. "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671 </ref> This provides good independent evidence that the obliquity (tilt) of Mars has changed significantly in the past.<ref> Laskar, Jacques; et al. 2004. "Long term evolution and chaotic diffusion of the insolation quantities of Mars". Icarus. 170 (2): 343–364.</ref> Evidence for past glaciation also appears on the peaks of several Martian volcanoes in the tropics.<ref> Head, J. W.; et al. 2005. "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–351.</ref> <ref> Shean, David E. 2005. "Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit". Journal of Geophysical Research. 110.</ref> <ref>Head, James W.; Marchant, David R. (2003). "Cold-based mountain glaciers on Mars: western Arsia Mons". Geology. 31 (7): 641–644. </ref>
For a long time there was some doubt about there actually being glaciers on Mars. However, instruments onboard the Mars Reconnaissance Orbiter confirmed the existence of ice below a shallow cover of debris. So far this ice has been found by the SHAllow RADar (SHARAD) in features called lobate debris aprons (LDA) and lineated valley fill (LVF).<ref name="Plaut, J. 2008">Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290. </ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> Ice was found both in the southern hemisphere <ref>Holt, J.; Safaeinili, A.; Plaut, J.; Head, J.; Phillips, R.; Seu, R.; Kempf, S.; Choudhary, P.; Young, D.; Putzig, N.; Biccari, D.; Gim, Y. 2008. "Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars". Science. 322: 1235–1238.</ref> and in the northern hemisphere.<ref> Plaut, J.; Safaeinili, A.; Holt, J.; Phillips, R.; Head, J.; Seu, R.; Putzig, N.; Frigeri, A. (2009). "Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophys. Res. Lett. 36. </ref> Researchers at the Niels Bohr Institute concluded that ice in all of the Martian glaciers is equivalent to what could cover the entire surface of Mars with 1.1 meters of ice. <ref>http://spaceref.com/mars/mars-has-belts-of-glaciers-consisting-of-frozen-water.html</ref> <ref>http://www.sciencedaily.com/releases/2015/04/150408102701.htm</ref> <ref>Karlsson, N.; Schmidt, L.; Hvidberg, C. (2015). "Volume of Martian mid-latitude glaciers from radar observations and ice-flow modelling". Geophysical Research Letters. 42: 2627–2633.</ref>
In addition to alpine glaciers on Mars, there are other terrains where ice seems to be moving under a few meters of cover.

===Lineated Valley Fill===

[[File:ESP 052138 1435lvf.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

[[File:ESP 046061 2190lvf.jpg|thumb|300px|right|Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)]]

[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of Lineated Valley Fill (LVF)]]

Lineated valley fill (LVF) are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines of ridges are thought to have developed as other glaciers moved down valleys.

===Lobate Debris Aprons===

[[File:800px-Wideviewlda42n18e.jpg|600pxr|Wide view of Lobate Debris Apron (LDA) around a mesa]]

Wide view of Lobate Debris Apron (LDA) around a mesa

Lobate debris aprons (LDA) is the name given to glaciers that surround many mesas and buttes. <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 046273 2225lda.jpg|Close view of LDA around a mesa Mesa is toward the top of the image. Lat: 42.2° N Long: 18.1°E

File:ESP 057389 2195ldacropped.jpg|LDA around a mound the Ismenius Lacus quadrangle, as seen by HiRISE under HiWish program

</gallery>

[[File:77699 2215contextldactx.jpg|600pxr|Wide and close views of LDA]]

Wide and close views of LDA

===Concentric Crater Fill===

Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> The concentric ridges could have been made by the movement of ice away from the walls.
Based on topography measures of height in these craters and calculations of how deep the craters should be based on their diameters, it is thought that the craters are 80% filled with mostly ice.<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref><ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> In other words, these craters hold hundreds of meters of material that probably consists of ice with just a few tens of meters of surface debris.<ref>Garvin, J. et al. 2002. Global geometric properties of martian impact craters. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> The ice accumulated in the crater from snowfall in previous climates.<ref>Kreslavsky, M. and J. Head. 2006. Modification of impact craters in the northern plains of Mars: Implications for the Amazonian climate history. Meteorit. Planet. Sci.: 41. 1633-1646</ref> <ref>Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> <ref>http://hirise.lpl.arizona.edu/PSP_002917_2175</ref> Concentric crater fill probably develops over many cycles in which snow is deposited, then moves into the crater. Once ice gets inside the crater, shade and a covering of dust preserve it. In time the snow changes to ice. Concentric lines are created by the many separate periods of snow accumulation. Generally snow accumulates whenever the planet’s tilt reaches 35 degrees.<ref>Fastook, J., J.Head. 2014. Concentric crater fill: Rates of glacial accumulation, infilling and deglaciation in the Amazonian and Noachian of Mars. 45th Lunar and Planetary Science Conference (2014) 1227.pdf</ref>

<gallery class="center" widths="380px" heights="360px">
File:Ccffigurecaptioned.jpg|This series of drawings illustrates why researchers believe many craters are full of ice-rich material. The depth of craters can be predicted based upon the observed diameter. Many craters are almost full, instead of having bowl shape; hence it is believed that they have gained much material since they were formed by impact. Much of the extra material is believed to be ice that fell from the sky as snow or ice-coated dust.
Image: 46622 1365ctxcontextccf.jpg|Wide context view of Concentric Crater Fill
Image: ESP_046622_1365ccf.jpg|Concentric Crater Fill Lat: 43.1° S Long: 219.8°E (140.2 W)
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill
</gallery>

==Pingos==

Because of the many signs of ground ice, scientists have speculated for years that someday pingos may be found on the planet. Pingos form in ice-rich ground and contain a core of pure ice. “Pingo,” is an Inuit word. Pingos on Mars would be great because they may contain pure water ice. Over the years many mounds have been examined that resemble pingos. However, we may not be sure if they are real pingos until they are examined by rovers. One picture below from HiRISE may be a pingo. The other picture shows how a pingo looks on the Earth.
The radial and concentric cracks visible here are common when forces penetrate a brittle layer. These particular fractures were probably created by something emerging from below the brittle Martian surface. Ice may have accumulated under the surface in a lens shape; thus making these cracked mounds. Ice being less dense than rock, pushed upwards on the surface and generated these spider web-like patterns. A similar process creates similar sized mounds in arctic tundra on Earth. <ref>http://www.uahirise.org/ESP_046359_1250</ref>

Many features that look like the pingos on the Earth are found in Utopia Planitia (~35-50° N; ~80-115° E).<ref>Soare, E., et al. 2019.
Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)

Melting pingo wedge ice.jpg|Example of a pingo on Earth. On Earth the ice that caused the pingo would melt and fill the fractures with water; on Mars the ice would turn into a gas in the thin Martian atmosphere.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

</gallery>

==Ring-Mold Craters==

Ring-mold craters are a kind of impact crater that looks like the ring molds used in baking.<ref>https://link.springer.com/referenceworkentry/10.1007/978-1-4614-9213-9_318-1</ref> <ref>kress, A., J. Head. 2008. Ring‐mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophysical Research Letters Volume 35, Issue 23</ref> They are believed to be caused by an impact into ice.<ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL035501</ref> Ice that is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." They are also bigger than other craters in which an asteroid impacted solid rock. Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill.<ref>Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8</ref> <ref>Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209</ref> <ref>Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379</ref> They may be an easy way for future colonists of Mars to find water ice because some may contain ice that is relatively pure. Also, since the ring-mold was created during a rebound, ice may have been brought up from below the surface so much less digging or drilling may be required to gather ice.

Note: this is one of the first explanations for ring-mold craters, another has been proposed.

<gallery class="center" widths="380px" heights="360px">
File:Ringmolddiagramlabeled.jpg|Ring-mold craters form when an impacting object goes through a rock layer to reach ice. The rebound forms the ring-mold shape, and then dust and debris settle on the top which serves to insulate the ice.
26055cratermesaswide.jpg|Wide view of a field of ring mold craters, as seen by HiRISE under HiWish program Lat: 34.9° S Long: 105.4° E
26055ringmoldcrater.jpg|Close view of ring mold crater. Note: this is an enlargement of the previous image of a field of ring mold craters.

File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
</gallery>

==Pedestal Craters==

[[File:Pedestaldrawingcolor2.jpg|thumb|400px|right|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

A pedestal crater is an impact crater which has its ejecta sitting above the surrounding terrain. This forms a raised platform (like a pedestal). These craters are produced when an impact crater ejects material that forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions.<ref>http://hirise.lpl.eduPSP_008508_1870</ref> <ref>Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref>http://themis.asu.edu/feature_utopiacraters</ref> <ref> McCauley, John F. (December 1972). "Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars". Journal of Geophysical Research. 78 (20): 4123–4137(JGRHomepage). </ref> Much of the material under the pedestal crater may be ice. These may be useful for sources of water ice as these craters can be easily spotted from orbit.

<gallery class="center" widths="380px" heights="360px">

Image: ESP 047615 1275pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program Top layer has protected the lower material from being eroded. Location is Hellas quadrangle, at 52.014° S and 110.651° E (249.349 W).

</gallery>

==Latitude Dependent Mantle==

With the increasing resolution of cameras orbiting Mars, we have discovered that many parts of the planet are covered by a smooth coating that in some cases is layered and quite thick. <ref>Mustard, J., C. Cooper, M. Rifkin. 2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature 412, 411–414 .</ref> Some parts are eroded, revealing rough surfaces. Some parts possess layers. It’s generally accepted that mantle is ice-rich dust that fell from the sky as snow and ice-coated dust grains during a different climate.<ref> Pollack, J., D. Colburn, F. Flaser, R. Kahn, C. Carson, and D. Pidek. 1979. Properties and effects of dust suspended in the martian atmosphere. J. Geophys. Res. 84, 2929-2945. </ref> Latitude Dependent Mantle and many other supposed ice-rich features occur in two latitude bands in the mid-latitudes; 30-60 degrees North and 30-60 degrees South latitudes.
We do not know the exact concentration of ice in the mantle. There may be a little or a lot; maybe the amount varies from place to place. Many places that we believe contain water may require hard drilling to harvest the ice. Perhaps the latitude dependent mantle will not be so hard to extract water from. We know that the mantle does not seem to break up into boulders. Boulders would suggest hard basalt to drill through.

<gallery class="center" widths="380px" heights="360px">
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
Esp 037167 1445mantle.jpg|Surface showing appearance with and without mantle covering Location is [[Terra Sirenum]] in Phaethontis quadrangle.
</gallery>

==Upper Plains Unit==

In many places, it seems that the latitude dependent mantle has accumulated to a substantial thickness. Researchers have called it the “Upper Plains Unit.” This unit can be easily spotted by orbiting satellites by a number of its shapes. Sometimes it displays sets of dipping layers in impact craters, in depressions, and along mesas. It may be 50-100 meters thick, so it may be a source of large amounts of water.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref>

[[File: ESP 019778 1385pyramid.jpg|thumb|400px|center|Layered structure in crater that is probably what is left of a layered unit that once covered a much larger area. Material for this unit fell from the sky as ice-coated dust. Location is Hellas quadrangle, Lat: 41.3° S Long: 116°E (244 W)]]

This unit also degrades into brain terrain. Brain terrain is a region of maze-like ridges 3–5 meters high. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>

[[File: 48011 1370upperunit.jpg|thumb|400px|left|Close view of upper plains unit breaking down into brain terrain As ice leaves the ground, the ground collapses and winds blow the remaining dust away. Location is Hellas quadrangle.]]

[[File:53630 2195brainslvf.jpg|thumb|400px|center|Close view of brain terrain]]

In some places the upper plains unit exists as large fractures and troughs with raised rims; these are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Cracks expose more surface area, and consequently more ice in the material sublimates into the planet’s thin atmosphere. Eventually, small cracks become large canyons or troughs.

[[File: ESP 042198 2235pyramid.jpg|thumb|400px|left|View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain. Lat: 43.2° N Long: 25.9° E (334.1 W)]]

[[File:ESP 028339 2245headarticle.jpg|thumb|400px|center|Ribbed terrain Lat: 44° N Long: 26.2°E (333.8 W)]]

There is one common surface feature that is common to most of these features that contain ice. It is called “brain terrain”. It consists of complex ridges that makes it resemble the outside of the human brain. Wide ridges are called ''closed-cell'' brain terrain, and the less common narrow ridges are called ''open-cell'' brain terrain.<ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref> It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. Brain terrain has been observed to form from what has been called an "Upper Plains Unit."

[[File:45917 2220brainsopenclosed.jpg|thumb|400px|left|Open and closed brain terrain with labels Lat: 41.9°N Long: 16.7° E (343.3 W) Closed-cell brain terrain may still contain an ice core.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> ]]

[[File:54527 2225brainsface.jpg|thumb|400px|center|Brain Terrain to the right. Box shows the size of a football field.]]

In summary, brain terrain is found on the surface of glaciers, concentric crater fill, lineated valley fill, lobate debris aprons, and the upper plains unit. The closed cell brain terrain probably contains a core of ice. We do not know the size of this core, but having a surface covered by brain terrain is a clue that much more ice may lie below.

==Future research and technology==

Although we have strong evidence that Mars had much water in its past and that certain landscapes are signs of water, there is much more to learn before we can start to utilize these resources. Ideally, we would not want to travel too far for our water. The ice found in triangular depressions may be too far. On the other hand water from the mantle and various glacial forms may be much closer, but it may require digging through meters of debris or the materials (in the mantle for example) may only contain a small percentage of water. Consequently, we should develop rovers and penetrators which could sample various features that contain water. This program of looking for ice-rich places should be intensified once we decide where we want to land. Already, individuals are targeting HiRISE observations at possible manned mission’s sites.<ref>https://www.uahirise.org/ESP_053423_2055</ref>
Later, we will want to develop robotic machines to mine, process, and deliver ice to the Mars colonists. At least one individual has designed a device that drills for and extracts water from ice-rich ground (check out second external link from the 20th Mars Society Convention). In 2017, there was a nation-wide contest for college students to build such a device.<ref>http://triblive.com/news/education/career/13040517-74/cmu-team-finalist-for-nasas-mars-ice-challenge-to-drill-for-water</ref> <ref>https://www.nasa.gov/press-release/nasa-s-mars-ice-challenge-follow-the-water</ref>

==Appendix==

As more and more observations from increasing powerful instruments was gathered, researchers developed ideas to explain the origin of ice rich features on a planet that is very cold and dry. It seems that ice moves from the poles to the mid-latitudes frequently, as the planets tilt changes.
Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as our moon stabilizes Earth; at times the tilt of Mars has even been greater than 80 degrees<ref> name= Touma J. and J. Wisdom. 1993. The Chaotic Obliquity of Mars. Science 259, 1294-1297.</ref> <ref> Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364. </ref>
When the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles. <ref> Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. doi:10.1029/2007GL032813. </ref> Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Models show that this material will concentrate in the mid-latitudes. <ref> Levy, J., J. Head, D. Marchant. 2009a. Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations. J. Geophys. Res. 114. doi:10.1029/2008JE003273.</ref> <ref> Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111-131 </ref> General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found. <ref> Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364. </ref>
When the tilt begins to return back to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust. <ref> Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799. </ref> <ref> Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799. </ref> <ref> Schorghofer, N., 2007. Dynamics of ice ages on Mars. Nature 449, 192–194.</ref> The lag deposit covers the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind. <ref> Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096. </ref>

==References==
{{reflist|colwidth=30em}}

== External links ==

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

==See Also==

*[[Glaciers on Mars]]

*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Sublimation]]

*[[Sublimation landscapes on Mars]]

*[[Water]]

[[Category: Hydrology]]

Martian features that are signs of water ice

2023-04-15T14:54:25Z

Suitupandshowup: /* Lobate Debris Aprons */ added image

How to find water on Mars

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

INTRODUCTION
Finding sources of water on Mars is necessary for future colonists. Studies with orbiting spacecraft have provided a great deal of evidence pointing to where water ice is located. Decades ago, theoretical studies showed that ice could exist under a cover of material that needed to be very thick near the equator, but at higher latitudes could be right under the surface.<ref>Rossbacher, L and S. Judson. 1981. Ground Ice on Mars: Inventory, Distribution, and Resulting Landforms. Icarus: 45, 39-59.</ref> Instruments onboard the Mars Odyssey measured the depth to this ice layer all over the planet.

[[Image: Mars Odyssey spacecraft model.png |thumb|200px|left|Artist view of Mars Odyssey]]

These measurements closely matched what the early theories had predicted. The Phoenix lander’s rockets blew away a thin cover of dirt to reveal the top of an ice layer.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> Also, by way of frequent pictures from Phoenix, we watched chunks of ice sublimate into the atmosphere. On Mars today, any exposed ice changes directly into a gas and mixes with the atmosphere in the process called [[sublimation]].

[[Image: Phoenix landing.jpg |thumb|200px|right|Artist view of Phoenix landing]]

[[File:PIA10741 Possible Ice Below Phoenix.jpg|thumb|200px|right|View under Phoenix spacecraft Bright regions are probably top of an ice sheet.]]

We also observed this process through HiRISE photos of ice first being exposed in new craters and then disappearing.

[[Image: Iceincraterscomparison.jpg|thumb|200px|left|Ice in crater Location: 43.286° N and 164.213°E]]

Thanks to the many satellites going around Mars with advanced instruments, we now have a list of features that are signs of easily obtainable underground ice. The shapes of some landscapes are similar to those on the earth that we know contain ice. Radar studies with the SHAllow RADar instrument (SHARD) on board the Mars Reconnaissance Orbiter ( MRO) have found large deposits of ice under relatively thin layers of debris cover for some of these features .<ref> Plaut, J., A. Safaeinili, J. Holt, R. Phillips, J. Head, J., R. Seu, N. Putzig, A. Frigeri. 2009. Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars. Geophys. Res. Lett. 36. doi:10.1029/2008GL036379.</ref> <ref> Holt, J., A. Safaeinili, J. Plaut, J. Head, R. Phillips, R. Seu, S. Kempf, P. Choudhary, D. Young, N. Putzig, D. Biccari, Y. Gim. 2008. Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars. Science 322. doi:10.1126/science.1164246 </ref> The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument onboard MRO has been able to detect spectroscopic signs of water in certain landscapes. The ice caps contain vast resovors of ice, but traveling to the poles is a long way to go for this precious resource. This article will display many landscapes that probably contain easily obtained water ice that are much closer than the poles.

[[Image: Mars Reconnaissance Orbiter spacecraft model.png |thumb|200px|right|Artist view of Mars Reconnaissance Orbiter ]]
[[Image: MRO CRISM prelaunch 2.jpg |thumb|200px|left|CRISM—identifies ice and other minerals]]

===Triangular depressions===

In early 2018, researchers released information about large amounts of ice found under only a few meters of soil. These places are easily seen as triangular depressions with one steep wall that faces the pole.<ref>https://www.uahirise.org/ESP_074914_1225</ref> These exposed ice sheets as thick as 100 meters were discovered by using instruments on board the Mars Reconnaissance Orbiter (MRO). Much evidence of underground ice in vast regions of Mars has already been found by past studies, but this study found that the ice was only covered by a layer of about 1 or 2 meters thick of Martian soil.<ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> Shane Byrne, one of the co-authors remarked that future colonists of the Red Planet would be able to gather up ice with just a bucket and shovel.<ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref> The fact that water-ice makes up the layers was confirmed by Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the [[Mars Reconnaissance Orbiter]] (MRO). The spectra gathered by CRISM showed strong signals of water.<ref>Colin M. Dundas, et al. ''Science'', 12 January 2018. Vol. 359, Issue 6372, pp. 199-201.</ref>

The sites are at latitudes from about 55 to 58 degrees north and south of the equator, suggesting that there is shallow ground ice under roughly a third of the Martian surface.<ref> Steep Slopes on Mars Reveal Structure of Buried Ice. NASA Press Release. 11 January 2018.</ref>

<gallery class="center" widths="380px" heights="360px">
ESP 045290 2350triangulardepression.jpg|Wide view of triangular depressions with ice under thin cover
45290 2350icelayerscloseer.jpg|Close view of depression, as seen by HiRISE under HiWish program Arrows indicate where there is a very thin, 1-2 meter covering on what is believed to be ice.<ref>https://www.uahirise.org/ESP_071573_2350</ref>
</gallery>

== Scalloped topography==

[[Image: ESP 037461 2255scallopstop.jpg|600pxr|Scalloped ground, as seen by HiRISE under HiWish program]]

Scalloped ground, as seen by HiRISE under HiWish program

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is particularly prominent in the region of Utopia Planitia<ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> in the northern hemisphere and in the region of Peneus and Amphitrites Patera in the southern hemisphere.<ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. A typical scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> This topographic asymmetry is probably due to differences in insolation. Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation. Sublimation is where a solid changes directly into a gas without going through a liquid phase. Dry ice on the Earth changes directly to a gas; but usually on Earth, ice will melt first to form a liquid phase before turning into a gas. This process is common in the thin Martian atmosphere.
In the fall of 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars.<ref>http://www.space.com/34811-mars-ice-more-water-than-lake-superior.html</ref> The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.<ref> "Lake of frozen water the size of New Mexico found on Mars – NASA". The Register. November 22, 2016 name="NASA-20161122"</ref> The volume of water ice in the region were based on measurements from the ground-penetrating radar instrument on Mars Reconnaissance Orbiter, called SHARAD. From the data obtained from SHARAD, a dielectric constant was determined. The dielectric constant value was consistent with a large concentration of water ice.<ref>Bramson, A, et al. 2015. Widespread excess ice in Arcadia Planitia, Mars. Geophysical Research Letters: 42, 6566-6574</ref> <ref>https://planetarycassie.com/2016/11/04/widespread-thick-water-ice-found-in-utopia-planitia-mars/</ref> <ref>Stuurman, C., et al. 2016. SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars. Geophysical Research Letters: 43, 9484_9491.</ref>

<gallery class="center" widths="380px" heights="360px">

File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle

File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia

</gallery>

==Glacial Features==

Over the years of satellite observations several features have been observed that look like glacial features that is it looks like ice is flowing under a thin cover of debris. Although ice is not stable at many latitudes of Mars, ice could survive for long periods under a few meters of dirt and rock. Many of these supposed regions of underground ice generally begin around 30 degrees of latitude on both sides of the equator. In other words latitudes greater than 30 degrees may have glaciers.<ref> Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>
Some bear an uncanny resemblance to alpine or mountain glaciers of the Earth. These, supposed alpine glaciers, have been called glacier-like forms (GLF) or glacier-like flows (GLF). <ref> Arfstrom, J and W. Hartmann. 2005. Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships. Icarus 174, 321-335.</ref> <ref> Hubbard B., R. Milliken, J. Kargel , A. Limaye, C. Souness . 2011. Geomorphological characterization and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars Icarus 211, 330–346 </ref> Another, more general term sometimes seen in the literature is viscous flow features (VFF). <ref> Hubbard B., R. Milliken, J. Kargel , A. Limaye, C. Souness . 2011. Geomorphological characterization and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars Icarus 211, 330–346 </ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° E (309.5 W)
File: Wikielephantglacier.jpg|Glacier in Greenland Notice how it resembles the glacier on Mars.
File:ESP 047193 1440tongues.jpg|Tongue-shaped glaciers Lat: 35.6° S Long: 109.7° E (250.3 W)

</gallery>

Based on current models of the Martian atmosphere, ice should not be stable if exposed at the surface in the mid-Martian latitudes.<ref>Williams, K. E.; et al. (2008). "Stability of mid-latitude snowpacks on Mars". Icarus. 196 (2): 565–577.</ref> It is thus thought that most glaciers must be covered with a layer of rubble or dust preventing free transfer of water vapor from the subliming ice into the air.<ref>Plaut, J.J.; Safaeinili, A.; Holt, J.W.; Phillips, R.J.; Head, J.W.; Sue, R.; Putzig, A. (2009). "Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophys. Res. Lett. 36: L02203.</ref> <ref>Head, J.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; et al. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–350.</ref> In the recent geological past, the climate of Mars may have been different in order to allow the glaciers to grow stably at these latitudes.<ref> Head, J. W.; et al. 2006. "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671 </ref> This provides good independent evidence that the obliquity (tilt) of Mars has changed significantly in the past.<ref> Laskar, Jacques; et al. 2004. "Long term evolution and chaotic diffusion of the insolation quantities of Mars". Icarus. 170 (2): 343–364.</ref> Evidence for past glaciation also appears on the peaks of several Martian volcanoes in the tropics.<ref> Head, J. W.; et al. 2005. "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–351.</ref> <ref> Shean, David E. 2005. "Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit". Journal of Geophysical Research. 110.</ref> <ref>Head, James W.; Marchant, David R. (2003). "Cold-based mountain glaciers on Mars: western Arsia Mons". Geology. 31 (7): 641–644. </ref>
For a long time there was some doubt about there actually being glaciers on Mars. However, instruments onboard the Mars Reconnaissance Orbiter confirmed the existence of ice below a shallow cover of debris. So far this ice has been found by the SHAllow RADar (SHARAD) in features called lobate debris aprons (LDA) and lineated valley fill (LVF).<ref name="Plaut, J. 2008">Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290. </ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> Ice was found both in the southern hemisphere <ref>Holt, J.; Safaeinili, A.; Plaut, J.; Head, J.; Phillips, R.; Seu, R.; Kempf, S.; Choudhary, P.; Young, D.; Putzig, N.; Biccari, D.; Gim, Y. 2008. "Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars". Science. 322: 1235–1238.</ref> and in the northern hemisphere.<ref> Plaut, J.; Safaeinili, A.; Holt, J.; Phillips, R.; Head, J.; Seu, R.; Putzig, N.; Frigeri, A. (2009). "Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophys. Res. Lett. 36. </ref> Researchers at the Niels Bohr Institute concluded that ice in all of the Martian glaciers is equivalent to what could cover the entire surface of Mars with 1.1 meters of ice. <ref>http://spaceref.com/mars/mars-has-belts-of-glaciers-consisting-of-frozen-water.html</ref> <ref>http://www.sciencedaily.com/releases/2015/04/150408102701.htm</ref> <ref>Karlsson, N.; Schmidt, L.; Hvidberg, C. (2015). "Volume of Martian mid-latitude glaciers from radar observations and ice-flow modelling". Geophysical Research Letters. 42: 2627–2633.</ref>
In addition to alpine glaciers on Mars, there are other terrains where ice seems to be moving under a few meters of cover.

===Lineated Valley Fill===

[[File:ESP 052138 1435lvf.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

[[File:ESP 046061 2190lvf.jpg|thumb|300px|right|Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)]]

[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of Lineated Valley Fill (LVF)]]

Lineated valley fill (LVF) are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines of ridges are thought to have developed as other glaciers moved down valleys.

===Lobate Debris Aprons===

[[File:800px-Wideviewlda42n18e.jpg|600pxr|Wide view of Lobate Debris Apron (LDA) around a mesa]]

Wide view of Lobate Debris Apron (LDA) around a mesa

Lobate debris aprons (LDA) is the name given to glaciers that surround many mesas and buttes. <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 046273 2225lda.jpg|Close view of LDA around a mesa Mesa is toward the top of the image. Lat: 42.2° N Long: 18.1°E

File:ESP 057389 2195ldacropped.jpg|LDA around a mound the Ismenius Lacus quadrangle, as seen by HiRISE under HiWish program

</gallery>

File:77699 2215contextldactx.jpg
[[File:77699 2215contextldactx.jpg|600pxr|Wide and close views of LDA]]

===Concentric Crater Fill===

Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> The concentric ridges could have been made by the movement of ice away from the walls.
Based on topography measures of height in these craters and calculations of how deep the craters should be based on their diameters, it is thought that the craters are 80% filled with mostly ice.<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref><ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> In other words, these craters hold hundreds of meters of material that probably consists of ice with just a few tens of meters of surface debris.<ref>Garvin, J. et al. 2002. Global geometric properties of martian impact craters. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> The ice accumulated in the crater from snowfall in previous climates.<ref>Kreslavsky, M. and J. Head. 2006. Modification of impact craters in the northern plains of Mars: Implications for the Amazonian climate history. Meteorit. Planet. Sci.: 41. 1633-1646</ref> <ref>Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> <ref>http://hirise.lpl.arizona.edu/PSP_002917_2175</ref> Concentric crater fill probably develops over many cycles in which snow is deposited, then moves into the crater. Once ice gets inside the crater, shade and a covering of dust preserve it. In time the snow changes to ice. Concentric lines are created by the many separate periods of snow accumulation. Generally snow accumulates whenever the planet’s tilt reaches 35 degrees.<ref>Fastook, J., J.Head. 2014. Concentric crater fill: Rates of glacial accumulation, infilling and deglaciation in the Amazonian and Noachian of Mars. 45th Lunar and Planetary Science Conference (2014) 1227.pdf</ref>

<gallery class="center" widths="380px" heights="360px">
File:Ccffigurecaptioned.jpg|This series of drawings illustrates why researchers believe many craters are full of ice-rich material. The depth of craters can be predicted based upon the observed diameter. Many craters are almost full, instead of having bowl shape; hence it is believed that they have gained much material since they were formed by impact. Much of the extra material is believed to be ice that fell from the sky as snow or ice-coated dust.
Image: 46622 1365ctxcontextccf.jpg|Wide context view of Concentric Crater Fill
Image: ESP_046622_1365ccf.jpg|Concentric Crater Fill Lat: 43.1° S Long: 219.8°E (140.2 W)
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill
</gallery>

==Pingos==

Because of the many signs of ground ice, scientists have speculated for years that someday pingos may be found on the planet. Pingos form in ice-rich ground and contain a core of pure ice. “Pingo,” is an Inuit word. Pingos on Mars would be great because they may contain pure water ice. Over the years many mounds have been examined that resemble pingos. However, we may not be sure if they are real pingos until they are examined by rovers. One picture below from HiRISE may be a pingo. The other picture shows how a pingo looks on the Earth.
The radial and concentric cracks visible here are common when forces penetrate a brittle layer. These particular fractures were probably created by something emerging from below the brittle Martian surface. Ice may have accumulated under the surface in a lens shape; thus making these cracked mounds. Ice being less dense than rock, pushed upwards on the surface and generated these spider web-like patterns. A similar process creates similar sized mounds in arctic tundra on Earth. <ref>http://www.uahirise.org/ESP_046359_1250</ref>

Many features that look like the pingos on the Earth are found in Utopia Planitia (~35-50° N; ~80-115° E).<ref>Soare, E., et al. 2019.
Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)

Melting pingo wedge ice.jpg|Example of a pingo on Earth. On Earth the ice that caused the pingo would melt and fill the fractures with water; on Mars the ice would turn into a gas in the thin Martian atmosphere.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

</gallery>

==Ring-Mold Craters==

Ring-mold craters are a kind of impact crater that looks like the ring molds used in baking.<ref>https://link.springer.com/referenceworkentry/10.1007/978-1-4614-9213-9_318-1</ref> <ref>kress, A., J. Head. 2008. Ring‐mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophysical Research Letters Volume 35, Issue 23</ref> They are believed to be caused by an impact into ice.<ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL035501</ref> Ice that is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." They are also bigger than other craters in which an asteroid impacted solid rock. Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill.<ref>Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8</ref> <ref>Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209</ref> <ref>Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379</ref> They may be an easy way for future colonists of Mars to find water ice because some may contain ice that is relatively pure. Also, since the ring-mold was created during a rebound, ice may have been brought up from below the surface so much less digging or drilling may be required to gather ice.

Note: this is one of the first explanations for ring-mold craters, another has been proposed.

<gallery class="center" widths="380px" heights="360px">
File:Ringmolddiagramlabeled.jpg|Ring-mold craters form when an impacting object goes through a rock layer to reach ice. The rebound forms the ring-mold shape, and then dust and debris settle on the top which serves to insulate the ice.
26055cratermesaswide.jpg|Wide view of a field of ring mold craters, as seen by HiRISE under HiWish program Lat: 34.9° S Long: 105.4° E
26055ringmoldcrater.jpg|Close view of ring mold crater. Note: this is an enlargement of the previous image of a field of ring mold craters.

File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
</gallery>

==Pedestal Craters==

[[File:Pedestaldrawingcolor2.jpg|thumb|400px|right|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

A pedestal crater is an impact crater which has its ejecta sitting above the surrounding terrain. This forms a raised platform (like a pedestal). These craters are produced when an impact crater ejects material that forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions.<ref>http://hirise.lpl.eduPSP_008508_1870</ref> <ref>Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref>http://themis.asu.edu/feature_utopiacraters</ref> <ref> McCauley, John F. (December 1972). "Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars". Journal of Geophysical Research. 78 (20): 4123–4137(JGRHomepage). </ref> Much of the material under the pedestal crater may be ice. These may be useful for sources of water ice as these craters can be easily spotted from orbit.

<gallery class="center" widths="380px" heights="360px">

Image: ESP 047615 1275pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program Top layer has protected the lower material from being eroded. Location is Hellas quadrangle, at 52.014° S and 110.651° E (249.349 W).

</gallery>

==Latitude Dependent Mantle==

With the increasing resolution of cameras orbiting Mars, we have discovered that many parts of the planet are covered by a smooth coating that in some cases is layered and quite thick. <ref>Mustard, J., C. Cooper, M. Rifkin. 2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature 412, 411–414 .</ref> Some parts are eroded, revealing rough surfaces. Some parts possess layers. It’s generally accepted that mantle is ice-rich dust that fell from the sky as snow and ice-coated dust grains during a different climate.<ref> Pollack, J., D. Colburn, F. Flaser, R. Kahn, C. Carson, and D. Pidek. 1979. Properties and effects of dust suspended in the martian atmosphere. J. Geophys. Res. 84, 2929-2945. </ref> Latitude Dependent Mantle and many other supposed ice-rich features occur in two latitude bands in the mid-latitudes; 30-60 degrees North and 30-60 degrees South latitudes.
We do not know the exact concentration of ice in the mantle. There may be a little or a lot; maybe the amount varies from place to place. Many places that we believe contain water may require hard drilling to harvest the ice. Perhaps the latitude dependent mantle will not be so hard to extract water from. We know that the mantle does not seem to break up into boulders. Boulders would suggest hard basalt to drill through.

<gallery class="center" widths="380px" heights="360px">
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
Esp 037167 1445mantle.jpg|Surface showing appearance with and without mantle covering Location is [[Terra Sirenum]] in Phaethontis quadrangle.
</gallery>

==Upper Plains Unit==

In many places, it seems that the latitude dependent mantle has accumulated to a substantial thickness. Researchers have called it the “Upper Plains Unit.” This unit can be easily spotted by orbiting satellites by a number of its shapes. Sometimes it displays sets of dipping layers in impact craters, in depressions, and along mesas. It may be 50-100 meters thick, so it may be a source of large amounts of water.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref>

[[File: ESP 019778 1385pyramid.jpg|thumb|400px|center|Layered structure in crater that is probably what is left of a layered unit that once covered a much larger area. Material for this unit fell from the sky as ice-coated dust. Location is Hellas quadrangle, Lat: 41.3° S Long: 116°E (244 W)]]

This unit also degrades into brain terrain. Brain terrain is a region of maze-like ridges 3–5 meters high. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>

[[File: 48011 1370upperunit.jpg|thumb|400px|left|Close view of upper plains unit breaking down into brain terrain As ice leaves the ground, the ground collapses and winds blow the remaining dust away. Location is Hellas quadrangle.]]

[[File:53630 2195brainslvf.jpg|thumb|400px|center|Close view of brain terrain]]

In some places the upper plains unit exists as large fractures and troughs with raised rims; these are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Cracks expose more surface area, and consequently more ice in the material sublimates into the planet’s thin atmosphere. Eventually, small cracks become large canyons or troughs.

[[File: ESP 042198 2235pyramid.jpg|thumb|400px|left|View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain. Lat: 43.2° N Long: 25.9° E (334.1 W)]]

[[File:ESP 028339 2245headarticle.jpg|thumb|400px|center|Ribbed terrain Lat: 44° N Long: 26.2°E (333.8 W)]]

There is one common surface feature that is common to most of these features that contain ice. It is called “brain terrain”. It consists of complex ridges that makes it resemble the outside of the human brain. Wide ridges are called ''closed-cell'' brain terrain, and the less common narrow ridges are called ''open-cell'' brain terrain.<ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref> It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. Brain terrain has been observed to form from what has been called an "Upper Plains Unit."

[[File:45917 2220brainsopenclosed.jpg|thumb|400px|left|Open and closed brain terrain with labels Lat: 41.9°N Long: 16.7° E (343.3 W) Closed-cell brain terrain may still contain an ice core.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> ]]

[[File:54527 2225brainsface.jpg|thumb|400px|center|Brain Terrain to the right. Box shows the size of a football field.]]

In summary, brain terrain is found on the surface of glaciers, concentric crater fill, lineated valley fill, lobate debris aprons, and the upper plains unit. The closed cell brain terrain probably contains a core of ice. We do not know the size of this core, but having a surface covered by brain terrain is a clue that much more ice may lie below.

==Future research and technology==

Although we have strong evidence that Mars had much water in its past and that certain landscapes are signs of water, there is much more to learn before we can start to utilize these resources. Ideally, we would not want to travel too far for our water. The ice found in triangular depressions may be too far. On the other hand water from the mantle and various glacial forms may be much closer, but it may require digging through meters of debris or the materials (in the mantle for example) may only contain a small percentage of water. Consequently, we should develop rovers and penetrators which could sample various features that contain water. This program of looking for ice-rich places should be intensified once we decide where we want to land. Already, individuals are targeting HiRISE observations at possible manned mission’s sites.<ref>https://www.uahirise.org/ESP_053423_2055</ref>
Later, we will want to develop robotic machines to mine, process, and deliver ice to the Mars colonists. At least one individual has designed a device that drills for and extracts water from ice-rich ground (check out second external link from the 20th Mars Society Convention). In 2017, there was a nation-wide contest for college students to build such a device.<ref>http://triblive.com/news/education/career/13040517-74/cmu-team-finalist-for-nasas-mars-ice-challenge-to-drill-for-water</ref> <ref>https://www.nasa.gov/press-release/nasa-s-mars-ice-challenge-follow-the-water</ref>

==Appendix==

As more and more observations from increasing powerful instruments was gathered, researchers developed ideas to explain the origin of ice rich features on a planet that is very cold and dry. It seems that ice moves from the poles to the mid-latitudes frequently, as the planets tilt changes.
Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as our moon stabilizes Earth; at times the tilt of Mars has even been greater than 80 degrees<ref> name= Touma J. and J. Wisdom. 1993. The Chaotic Obliquity of Mars. Science 259, 1294-1297.</ref> <ref> Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364. </ref>
When the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles. <ref> Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. doi:10.1029/2007GL032813. </ref> Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Models show that this material will concentrate in the mid-latitudes. <ref> Levy, J., J. Head, D. Marchant. 2009a. Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations. J. Geophys. Res. 114. doi:10.1029/2008JE003273.</ref> <ref> Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111-131 </ref> General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found. <ref> Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364. </ref>
When the tilt begins to return back to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust. <ref> Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799. </ref> <ref> Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799. </ref> <ref> Schorghofer, N., 2007. Dynamics of ice ages on Mars. Nature 449, 192–194.</ref> The lag deposit covers the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind. <ref> Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096. </ref>

==References==
{{reflist|colwidth=30em}}

== External links ==

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

==See Also==

*[[Glaciers on Mars]]

*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Sublimation]]

*[[Sublimation landscapes on Mars]]

*[[Water]]

[[Category: Hydrology]]

File:77699 2215contextldactx.jpg

2023-04-15T14:51:45Z

Suitupandshowup: Lobate debris apron (LDA) as seen by CTX and HiRISE. Wide view with CTX, close view with HiRISE. HiRISE image from HiWish program. Sources: CTX image from http://viewer.mars.asu.edu/planetview/inst/ctx/F01_036185_2217_XN_41N344W#P=F01_036185_2217_XN_41N344W&T=2 HiRISE image from https://www.uahirise.org/ESP_077699_2215 Image Credits: CTX NASA/MSSS/Secosky HiRISE NASA/JPL/University of Arizona/Secosky

== Summary ==
Lobate debris apron (LDA) as seen by CTX and HiRISE. Wide view with CTX, close view with HiRISE. HiRISE image from HiWish program.

Sources: CTX image from http://viewer.mars.asu.edu/planetview/inst/ctx/F01_036185_2217_XN_41N344W#P=F01_036185_2217_XN_41N344W&T=2

HiRISE image from https://www.uahirise.org/ESP_077699_2215

Image Credits: CTX NASA/MSSS/Secosky
HiRISE NASA/JPL/University of Arizona/Secosky
== Licensing ==
{{PD}}

Noachis quadrangle

2023-03-21T00:56:05Z

Suitupandshowup: /* Hellas floor features */

{{Mars atlas}}

{| class="wikitable sortable"
|MC-27
|Noachis
|30–65° S
|0–60° E
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-27-NoachisRegion-mola.png
File:Noachis Terra.jpg
</gallery>
[[Category: Mars Atlas]]

The Noachis quadrangle covers the area from 30° to 65° south latitude and 300° to 360° west longitude (60-0 E). It lies between Argyre and Hellas, two giant impact basins on Mars. The Noachis quadrangle includes Noachis Terra and the western part of Hellas Planitia, which are classical names for regions on Mars. The name "Noachis" means the land of Noah.
Noachis is considered among the oldest regions on Mars since it is so densely covered with impact craters. The oldest parts of Mars have the designation of “Noachian age."
In addition, many previously buried craters are now coming to the surface.<ref>http://themis.asu.edu/zoom-20040317a|title=Exhumed Crater (Released 17 March 2004)|author=Mars Space Flight Facility|date=17 March 2004|publisher=Arizona State University|</ref> Noachis' extreme age has allowed ancient craters to be filled, and once again become newly exposed.
Much of the surface in Noachis quadrangle shows a scalloped topography in which the disappearance of ground ice has left depressions.<ref>Lefort | first1 = A. | display-authors = etal | year = 2010 | title = Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE | url = | journal = Icarus | volume = 205 | issue = 1| pages = 259–268 | </ref>
The first piece of human technology to land on Mars landed (crashed) in the Noachis quadrangle. It was the Soviet's Mars 2 that crash landed at 44.2 S and 313.2 W. It weighed about one ton. The automated craft attempted to land in a giant dust storm and in an area that has many dust devils.<ref>Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY, NY.</ref>

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

==Scalloped topography==

Certain regions of Mars display scalloped-shaped depressions. The depressions are believed to be the remains of an ice-rich mantle deposit. Scallops are created when ice sublimates from frozen soil.<ref>https://www.uahirise.org/PSP_004340_1235 | title=HiRISE | Scalloped Depressions in Peneus Patera (PSP_004340_1235)}}</ref> <ref>McEwen, A., et al. 2017. Mars The Pristine Beauty of the Red Planet. University of Arizona Press. Tucson.</ref> This mantle material probably fell from the air as ice formed on dust when the climate was different due to changes in the tilt of the Mars pole.<ref>doi=10.1038/nature02114 |pmid=14685228 |title=Recent ice ages on Mars |journal=Nature |volume=426 |issue=6968 |pages=797–802 |year=2003 |last1=Head |first1=James W. |last2=Mustard |first2=John F. |last3=Kreslavsky |first3=Mikhail A. |last4=Milliken |first4=Ralph E. |last5=Marchant |first5=David R. |</ref> The scallops are typically tens of meters deep and from a few hundred to a few thousand meters across. They can be almost circular or elongated. Some appear to have coalesced, thereby causing a large heavily pitted terrain to form. A study published in Icarus, found that the landforms of scalloped topography can be made by the subsurface loss of water ice by sublimation under current Martian climate conditions. This model predicts similar shapes when the ground has large amounts of pure ice, up to many tens of meters in depth.<ref> |doi=10.1016/j.icarus.2015.07.033 |title=Modeling the development of martian sublimation thermokarst landforms |journal=Icarus |volume=262 |pages=154–169 |year=2015 |last1=Dundas |first1=Colin M. |last2=Byrne |first2=Shane |last3=McEwen |first3=Alfred S. |https://zenodo.org/record/1259051/files/article.pdf </ref>
The process of producing the terrain may begin with sublimation from a crack because there are often polygon cracks where scallops form.<ref > Lefort, A.; et al. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259–268.</ref> In other words, when we see this type of surface, we know there is probably ice in the ground. Future astronauts may mine this terrain for water.

<gallery class="center" widths="380px" heights="360px">

4340 1235scalloped.jpg|Close view of scalloped topography, as seen by HiRISE

ESP 050728 1210scalloped.jpg|Scalloped topography, as seen by HiRISE under HiWish program

</gallery>

== Dust Devil Tracks ==

[[File:ESP 050715 1225devilsscallops.jpg|600pxr|Dust devil tracks and scalloped topography, as seen by HiRISE under [[HiWish program]]]]
Dust devil tracks and scalloped topography, as seen by HiRISE under [[HiWish program]]

Many areas on Mars experience the passage of giant dust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface creating tracks. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will be enough. The width of a single human hair ranges from approximately 20 to 200 microns (μm); consequently, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Dust devils have been seen from the ground and from orbit. They have even blown the dust off of the solar panels of the two Mars Exploration Rovers (Spirit and Opportunity), thereby greatly extending their lives.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html|publisher=National Aeronautics and Space Administration</ref> The twin Rovers were designed to last for 3 months, instead they lasted many years with Opportunity lasting over 14 years. The pattern of the dust devil tracks have been shown to change every few months.<ref>https://web.archive.org/web/20111028015730/http://mars.jpl.nasa.gov/spotlight/kenEdgett.html |</ref> One study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 meters and last at least 26 minutes.<ref>doi=10.1016/j.icarus.2011.06.011 |title=Multitemporal observations of identical active dust devils on Mars with the High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC) |journal=Icarus |volume=215 |issue=1 |pages=358–369 |year=2011 |last1=Reiss |first1=D. |last2=Zanetti |first2=M. |last3=Neukum |first3=G. |</ref> The image below of Russel Crater shows changes in dust devil tracks over a period of only three months, as documented by HiRISE.

<gallery class="center" widths="380px" heights="360px">

Image:Russel Crater Dust Devil Changes.JPG|Russell Crater Dust Devil Changes, as seen by HiRISE. The pictures show that major changes in dust devil tracks happened in just 3 months.

</gallery>

==Craters==

<gallery class="center" widths="380px" heights="360px">

Image:Asimov Layers Close-up.JPG|Close-up of layers in west slope of Asimov Crater. Shadows show the overhang. Some of the layers are much more resistant to erosion, so they stick out. Image from HiRISE.

Image:Kaiser Crater.JPG|Kaiser Crater (large crater in upper part of image)context for THEMIS image.
Image:Kaiser Crater.jpg|Detail of south wall of Kaiser Crater, as seen by THEMIS. Top of image shows part of a dune field.

Image:Exhumed crater in Noachis.JPG|Crater that was buried in another age and is now being exposed by erosion, as seen by the [[Mars Global Surveyor]], under the MOC Public Targeting Program.

Image:24396floor.jpg|Floor of crater in Noachis quadrangle, as seen by HiRISE under [[HiWish program]].

</gallery>

==Sand Dunes==

[[File: Dark dunes in Noachis.JPG|600pxr|Wide view of a field of sand dunes]]
Wide view of a field of sand dunes, as seen by Mars Global Surveyor

When there are perfect conditions for producing sand dunes, (steady wind in one direction and just enough sand), a barchan sand dune forms. Barchans have a gentle slope on the wind side and a much steeper slope on the lee side where horns or a notch often forms.<ref>Pye|first=Kenneth|title=Aeolian Sand and Sand Dunes|year=2008|publisher=Springer|isbn=9783540859109|pages=138|</ref> One picture below shows a definite barchan.

[[File:ESP 046378 1415dunes.jpg|600pxr|Dark dunes]]
Wide view of a field of sand dunes

<gallery class="center" widths="380px" heights="360px">

Image:Dunes Wide View.jpg|Wide view of dunes in Noachis, as seen by HiRISE.
Image:Close-up view of Dunes.jpg|Close-up View of dunes in previous image, as seen by HiRISE. Note how sand barely covers some boulders.

46378 1415dunes.jpg|Close view of sand dunes A barchan dune is labeled.
46378 1415dunes2.jpg|Close view of sand dunes, as seen by HiRISE under HiWish program
46378 1415dunes3.jpg|Close view of sand dunes A barchan dune is labeled.
ESP 046378 1415dunescolor.jpg|Close, color view of sand dunes
File:55097 1455dunescolor.jpg|Close, color view of dome sand dunes, as seen by HiRISE under[[HiWish program]]

</gallery>

==Gullies==

Gullies on steep slopes are found in certain regions of Mars. Many ideas have been advanced to explain them. Formation by running water when the climate was different is a popular idea. Recently, because changes in gullies have been seen since HiRISE has been orbiting Mars, it is thought that they may be formed by chunks of dry ice moving down slope during spring time. Gullies are one of the most interesting discoveries made by orbiting space craft.<ref>http://www.jpl.nasa.gov/news/news.php?release=2014-226 | title=NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032078_1420 | title=HiRISE | Activity in Martian Gullies (ESP_032078_1420)</ref> <ref>http://www.space.com/26534-mars-gullies-dry-ice.html | title=Gullies on Mars Carved by Dry Ice, Not Water</ref> <ref>http://spaceref.com/mars/frosty-gullies-on-mars.html | title=Frosty Gullies on Mars - SpaceRef</ref>

<gallery class="center" widths="190px" heights="180px" >
ESP 048159 1310gullies.jpg|Wide view of gullies and ridges in crater Ridges may be from old glaciers.

48159 1310gullychannelsclose.jpg|Close view of gully channels Arrows point to small channel within larger channels.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 055056 1420gulliesridges.jpg|Wide view of gullies, as seen by HiRISE under [[HiWish program]]

File:55056 1420gullies.jpg|Close view of gullies Channels show curves.

File:55056 1420gulliesclose.jpg|Close view of gullies, as seen by HiRISE under HiWish program Polygonal shapes are visible.

File:ESP 055227 1420crater.jpg|Crater with gullies
File:55227 1420gullies.jpg|Close view of gullies

</gallery>

==Hellas floor features==

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

The Hellas floor contains some strange-looking features. One of these features is called "banded terrain."<ref>Diot, X., et al. 2014. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars. Planetary and Space Science: 101, 118-134.</ref> <ref>http://www.nasa.gov/mission_pages/MRO/multimedia/20070717-2.html | title=NASA - Banded Terrain in Hellas</ref> <ref>http://hirise.lpl.arizona.edu/ESP_016154_1420 | title=HiRISE | Complex Banded Terrain in Hellas Planitia (ESP_016154_1420)</ref> This terrain has also been called "taffy pull" terrain, and it lies near honeycomb terrain, another strange surface.<ref>Bernhardt, H., et al. 2018. THE BANDED TERRAIN ON THE HELLAS BASIN FLOOR, MARS: GRAVITY-DRIVEN FLOW NOT SUPPORTED BY NEW OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1143.pdf</ref> Banded terrain is found in the north-western part of the Hellas basin. This is the deepest part of the Hellas basin. The banded-terrain deposit displays an alternation of narrow band shapes and inter-bands. The sinuous nature and relatively smooth surface texture suggesting a viscous flow origin. A study published in Planetary and Space Science found that this terrain was the youngest deposit of the interior of Hellas. They also suggest in the paper that banded terrain may have covered a larger area of the NW interior of Hellas. The bands can be classified as linear, concentric, or lobate. Bands are typically 3–15 km long, 3 km wide. Narrow inter-band depressions are 65 m wide and 10 m deep.<ref>Complex geomorphologic assemblage of terrains in association with the banded terrain in Hellas basin, Mars |journal=Planetary and Space Science |volume=121 |pages=36–52 |year=2016 |last1=Diot |first1=X. |last2=El-Maarry |first2=M.R. |last3=Schlunegger |first3=F. |last4=Norton |first4=K.P. |last5=Thomas |first5=N. |last6=Grindrod |first6=P.M. |last7=Chojnacki |first7=M. |bibcode=2016P&SS..121...36D |url=https://boris.unibe.ch/74530/1/Diot_Schlunegger.pdf </ref> Researchers do not at this time understand how these features ere formed. .<ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/1588.pdf</ref> <ref>Cook, C., et al. 2022. FORMATION OF THE BANDED TERRAIN OF HELLAS PLANITIA, MARS. 53rd Lunar and Planetary Science Conference (2022). 1588.pdf</ref>

One idea for how these strange features were created involves a large mass of ice being deposited into the Hellas basin. Later the ice could be covered with lava and ash from the many nearby volcanoes. Hot lava would melt some of the ice, but the heat may not have been enough to melt all the ice. So, there may have been a thick layer of lava and ash sitting on top of ice. The ice is much less dense; consequently, it would rise through the denser material that covers it. Strange shapes could result. This principle is like when one pulls a ball down into a swimming pool. The ball would want to go up through the water. On Earth this type of event occurs. The bodies that form are called diapirs. Sometimes salt deposits covered by sediment move upward on the Earth. Diapir comes from Greek diapeirein, which means “to pierce" in reference to how one lower density body pierces or moves through another.<ref> Fastook1, J. and J. Head. 2023. HELLAS BASIN, MARS: RIM-WALL-FLOOR GLACIATION IN THE LATE NOACHIAN-EARLY HESPERIAN AND INTERACTIONS WITH SUPERPOSED LAVA FLOWS. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1330.pdf</ref>

Pictures of these features can look like abstract art.

[[File:Twisted Terrain in Hellas Planitia.jpg|600pxr|Twisted Terrain in Hellas Planitia, but actually located in Noachis quadrangle. Imagine trying to walk across this. Image taken with HiRISE.]]

Twisted Terrain in Hellas Planitia, but actually located in Noachis quadrangle. Imagine trying to walk across this. Image taken with HiRISE.

<gallery class="center" widths="380px" heights="360px">
ESP 048830 1415ridges.jpg|Layered features on floor of Hellas Planitia This may be an example of honeycomb terrain that is not yet completely understood.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 055080 1425twistedbands.jpg|Twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program

File:ESP 055212 1420taffypull.jpg|Twisted bands on the floor of Hellas Planitia These twisted bands are also called "taffy pull" terrain.

</gallery>

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Floor features in Hellas Planitia

[[File:ESP 055146 1425ridges.jpg|600pxr|Wide view of twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program]]

Wide view of twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program

==Gullies on Dunes==

Gullies are found on some dunes. These are somewhat different than gullies in other places, like the walls of craters. Gullies on dunes seem to keep the same width for a long distance and often just end with a pit, instead of an apron. Many of these gullies are found on dunes in Russell Crater.

<gallery class="center" widths="380px" heights="360px">

ESP 020217 1255dunechannels.jpg|Wide view of dunes in Russell Crater, as seen by HiRISE Many narrow gullies are visible.

20217 1255dunechannelsclose.jpg|Close view of the end of gullies in Russell Crater Note: These type of gullies do not usually end with an apron.

20217 1255dunechannelsclosetop.jpg|Close view of the end of gullies in Russell Crater

ESP 020217 1255dunesclosecolor.jpg|Close, color view of the end of gullies in Russell Crater, as seen by HiRISE
</gallery>

==Channels==

<gallery class="center" widths="380px" heights="360px">

File:ESP 056981 1415channels.jpg|Channels
File:ESP 053698 1485channel.jpg|Channel, as seen by HiRISE under HiWish program
</gallery>

== Other scenes from Noachis quadrangle ==

<gallery class="center" widths="380px" heights="360px">

46417 1425straightridges.jpg|Ridges, as seen by HiRISE under HiWish program
48159 1310highcenterpolygons.jpg|High center polygons Boxes are drawn around two individual polygons.

ESP 048184 1470moundsbrains.jpg|Wide view of mounds and brain terrain
48184 1470moundsbrains.jpg|Close view of mounds and brain terrain
ESP 049226 1480boulderslighttoned.jpg|Light-toned material Light-toned material is often associated with minerals that formed in water.
49226 1480boulderslighttoned.jpg|Close view of surface, showing boulders and light-toned material
ESP 049674 1470flow.jpg|Flow or glacier
ESP 051138 1460ridges.jpg|Wide view showing flows and ridges

</gallery>

==See also==

*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[HiWish program]]
*[[How are features on Mars Named?]]
*[[Mars Global Surveyor]]
*[[Martian gullies]]
*[[Rivers on Mars]]

== External links ==

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]
* https://www.youtube.com/watch?v=483HcpqyMNU Banded Flow Terrain in Hellas Basin

==References==
{{reflist|colwidth=30em}}

==References==
{{reflist|colwidth=30em}}

Noachis quadrangle

2023-03-21T00:54:58Z

Suitupandshowup: /* Hellas floor features */ added

{{Mars atlas}}

{| class="wikitable sortable"
|MC-27
|Noachis
|30–65° S
|0–60° E
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-27-NoachisRegion-mola.png
File:Noachis Terra.jpg
</gallery>
[[Category: Mars Atlas]]

The Noachis quadrangle covers the area from 30° to 65° south latitude and 300° to 360° west longitude (60-0 E). It lies between Argyre and Hellas, two giant impact basins on Mars. The Noachis quadrangle includes Noachis Terra and the western part of Hellas Planitia, which are classical names for regions on Mars. The name "Noachis" means the land of Noah.
Noachis is considered among the oldest regions on Mars since it is so densely covered with impact craters. The oldest parts of Mars have the designation of “Noachian age."
In addition, many previously buried craters are now coming to the surface.<ref>http://themis.asu.edu/zoom-20040317a|title=Exhumed Crater (Released 17 March 2004)|author=Mars Space Flight Facility|date=17 March 2004|publisher=Arizona State University|</ref> Noachis' extreme age has allowed ancient craters to be filled, and once again become newly exposed.
Much of the surface in Noachis quadrangle shows a scalloped topography in which the disappearance of ground ice has left depressions.<ref>Lefort | first1 = A. | display-authors = etal | year = 2010 | title = Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE | url = | journal = Icarus | volume = 205 | issue = 1| pages = 259–268 | </ref>
The first piece of human technology to land on Mars landed (crashed) in the Noachis quadrangle. It was the Soviet's Mars 2 that crash landed at 44.2 S and 313.2 W. It weighed about one ton. The automated craft attempted to land in a giant dust storm and in an area that has many dust devils.<ref>Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY, NY.</ref>

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

==Scalloped topography==

Certain regions of Mars display scalloped-shaped depressions. The depressions are believed to be the remains of an ice-rich mantle deposit. Scallops are created when ice sublimates from frozen soil.<ref>https://www.uahirise.org/PSP_004340_1235 | title=HiRISE | Scalloped Depressions in Peneus Patera (PSP_004340_1235)}}</ref> <ref>McEwen, A., et al. 2017. Mars The Pristine Beauty of the Red Planet. University of Arizona Press. Tucson.</ref> This mantle material probably fell from the air as ice formed on dust when the climate was different due to changes in the tilt of the Mars pole.<ref>doi=10.1038/nature02114 |pmid=14685228 |title=Recent ice ages on Mars |journal=Nature |volume=426 |issue=6968 |pages=797–802 |year=2003 |last1=Head |first1=James W. |last2=Mustard |first2=John F. |last3=Kreslavsky |first3=Mikhail A. |last4=Milliken |first4=Ralph E. |last5=Marchant |first5=David R. |</ref> The scallops are typically tens of meters deep and from a few hundred to a few thousand meters across. They can be almost circular or elongated. Some appear to have coalesced, thereby causing a large heavily pitted terrain to form. A study published in Icarus, found that the landforms of scalloped topography can be made by the subsurface loss of water ice by sublimation under current Martian climate conditions. This model predicts similar shapes when the ground has large amounts of pure ice, up to many tens of meters in depth.<ref> |doi=10.1016/j.icarus.2015.07.033 |title=Modeling the development of martian sublimation thermokarst landforms |journal=Icarus |volume=262 |pages=154–169 |year=2015 |last1=Dundas |first1=Colin M. |last2=Byrne |first2=Shane |last3=McEwen |first3=Alfred S. |https://zenodo.org/record/1259051/files/article.pdf </ref>
The process of producing the terrain may begin with sublimation from a crack because there are often polygon cracks where scallops form.<ref > Lefort, A.; et al. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259–268.</ref> In other words, when we see this type of surface, we know there is probably ice in the ground. Future astronauts may mine this terrain for water.

<gallery class="center" widths="380px" heights="360px">

4340 1235scalloped.jpg|Close view of scalloped topography, as seen by HiRISE

ESP 050728 1210scalloped.jpg|Scalloped topography, as seen by HiRISE under HiWish program

</gallery>

== Dust Devil Tracks ==

[[File:ESP 050715 1225devilsscallops.jpg|600pxr|Dust devil tracks and scalloped topography, as seen by HiRISE under [[HiWish program]]]]
Dust devil tracks and scalloped topography, as seen by HiRISE under [[HiWish program]]

Many areas on Mars experience the passage of giant dust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface creating tracks. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will be enough. The width of a single human hair ranges from approximately 20 to 200 microns (μm); consequently, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Dust devils have been seen from the ground and from orbit. They have even blown the dust off of the solar panels of the two Mars Exploration Rovers (Spirit and Opportunity), thereby greatly extending their lives.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html|publisher=National Aeronautics and Space Administration</ref> The twin Rovers were designed to last for 3 months, instead they lasted many years with Opportunity lasting over 14 years. The pattern of the dust devil tracks have been shown to change every few months.<ref>https://web.archive.org/web/20111028015730/http://mars.jpl.nasa.gov/spotlight/kenEdgett.html |</ref> One study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 meters and last at least 26 minutes.<ref>doi=10.1016/j.icarus.2011.06.011 |title=Multitemporal observations of identical active dust devils on Mars with the High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC) |journal=Icarus |volume=215 |issue=1 |pages=358–369 |year=2011 |last1=Reiss |first1=D. |last2=Zanetti |first2=M. |last3=Neukum |first3=G. |</ref> The image below of Russel Crater shows changes in dust devil tracks over a period of only three months, as documented by HiRISE.

<gallery class="center" widths="380px" heights="360px">

Image:Russel Crater Dust Devil Changes.JPG|Russell Crater Dust Devil Changes, as seen by HiRISE. The pictures show that major changes in dust devil tracks happened in just 3 months.

</gallery>

==Craters==

<gallery class="center" widths="380px" heights="360px">

Image:Asimov Layers Close-up.JPG|Close-up of layers in west slope of Asimov Crater. Shadows show the overhang. Some of the layers are much more resistant to erosion, so they stick out. Image from HiRISE.

Image:Kaiser Crater.JPG|Kaiser Crater (large crater in upper part of image)context for THEMIS image.
Image:Kaiser Crater.jpg|Detail of south wall of Kaiser Crater, as seen by THEMIS. Top of image shows part of a dune field.

Image:Exhumed crater in Noachis.JPG|Crater that was buried in another age and is now being exposed by erosion, as seen by the [[Mars Global Surveyor]], under the MOC Public Targeting Program.

Image:24396floor.jpg|Floor of crater in Noachis quadrangle, as seen by HiRISE under [[HiWish program]].

</gallery>

==Sand Dunes==

[[File: Dark dunes in Noachis.JPG|600pxr|Wide view of a field of sand dunes]]
Wide view of a field of sand dunes, as seen by Mars Global Surveyor

When there are perfect conditions for producing sand dunes, (steady wind in one direction and just enough sand), a barchan sand dune forms. Barchans have a gentle slope on the wind side and a much steeper slope on the lee side where horns or a notch often forms.<ref>Pye|first=Kenneth|title=Aeolian Sand and Sand Dunes|year=2008|publisher=Springer|isbn=9783540859109|pages=138|</ref> One picture below shows a definite barchan.

[[File:ESP 046378 1415dunes.jpg|600pxr|Dark dunes]]
Wide view of a field of sand dunes

<gallery class="center" widths="380px" heights="360px">

Image:Dunes Wide View.jpg|Wide view of dunes in Noachis, as seen by HiRISE.
Image:Close-up view of Dunes.jpg|Close-up View of dunes in previous image, as seen by HiRISE. Note how sand barely covers some boulders.

46378 1415dunes.jpg|Close view of sand dunes A barchan dune is labeled.
46378 1415dunes2.jpg|Close view of sand dunes, as seen by HiRISE under HiWish program
46378 1415dunes3.jpg|Close view of sand dunes A barchan dune is labeled.
ESP 046378 1415dunescolor.jpg|Close, color view of sand dunes
File:55097 1455dunescolor.jpg|Close, color view of dome sand dunes, as seen by HiRISE under[[HiWish program]]

</gallery>

==Gullies==

Gullies on steep slopes are found in certain regions of Mars. Many ideas have been advanced to explain them. Formation by running water when the climate was different is a popular idea. Recently, because changes in gullies have been seen since HiRISE has been orbiting Mars, it is thought that they may be formed by chunks of dry ice moving down slope during spring time. Gullies are one of the most interesting discoveries made by orbiting space craft.<ref>http://www.jpl.nasa.gov/news/news.php?release=2014-226 | title=NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032078_1420 | title=HiRISE | Activity in Martian Gullies (ESP_032078_1420)</ref> <ref>http://www.space.com/26534-mars-gullies-dry-ice.html | title=Gullies on Mars Carved by Dry Ice, Not Water</ref> <ref>http://spaceref.com/mars/frosty-gullies-on-mars.html | title=Frosty Gullies on Mars - SpaceRef</ref>

<gallery class="center" widths="190px" heights="180px" >
ESP 048159 1310gullies.jpg|Wide view of gullies and ridges in crater Ridges may be from old glaciers.

48159 1310gullychannelsclose.jpg|Close view of gully channels Arrows point to small channel within larger channels.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 055056 1420gulliesridges.jpg|Wide view of gullies, as seen by HiRISE under [[HiWish program]]

File:55056 1420gullies.jpg|Close view of gullies Channels show curves.

File:55056 1420gulliesclose.jpg|Close view of gullies, as seen by HiRISE under HiWish program Polygonal shapes are visible.

File:ESP 055227 1420crater.jpg|Crater with gullies
File:55227 1420gullies.jpg|Close view of gullies

</gallery>

==Hellas floor features==

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

The Hellas floor contains some strange-looking features. One of these features is called "banded terrain."<ref>Diot, X., et al. 2014. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars. Planetary and Space Science: 101, 118-134.</ref> <ref>http://www.nasa.gov/mission_pages/MRO/multimedia/20070717-2.html | title=NASA - Banded Terrain in Hellas</ref> <ref>http://hirise.lpl.arizona.edu/ESP_016154_1420 | title=HiRISE | Complex Banded Terrain in Hellas Planitia (ESP_016154_1420)</ref> This terrain has also been called "taffy pull" terrain, and it lies near honeycomb terrain, another strange surface.<ref>Bernhardt, H., et al. 2018. THE BANDED TERRAIN ON THE HELLAS BASIN FLOOR, MARS: GRAVITY-DRIVEN FLOW NOT SUPPORTED BY NEW OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1143.pdf</ref> Banded terrain is found in the north-western part of the Hellas basin. This is the deepest part of the Hellas basin. The banded-terrain deposit displays an alternation of narrow band shapes and inter-bands. The sinuous nature and relatively smooth surface texture suggesting a viscous flow origin. A study published in Planetary and Space Science found that this terrain was the youngest deposit of the interior of Hellas. They also suggest in the paper that banded terrain may have covered a larger area of the NW interior of Hellas. The bands can be classified as linear, concentric, or lobate. Bands are typically 3–15 km long, 3 km wide. Narrow inter-band depressions are 65 m wide and 10 m deep.<ref>Complex geomorphologic assemblage of terrains in association with the banded terrain in Hellas basin, Mars |journal=Planetary and Space Science |volume=121 |pages=36–52 |year=2016 |last1=Diot |first1=X. |last2=El-Maarry |first2=M.R. |last3=Schlunegger |first3=F. |last4=Norton |first4=K.P. |last5=Thomas |first5=N. |last6=Grindrod |first6=P.M. |last7=Chojnacki |first7=M. |bibcode=2016P&SS..121...36D |url=https://boris.unibe.ch/74530/1/Diot_Schlunegger.pdf </ref> Researchers do not at this time understand how these features ere formed. .<ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/1588.pdf</ref> <ref>Cook, C., et al. 2022. FORMATION OF THE BANDED TERRAIN OF HELLAS PLANITIA, MARS. 53rd Lunar and Planetary Science Conference (2022). 1588.pdf</ref>

One idea for how these strange features were created involves a large mass of ice being deposited into the Hellas basin. Later the ice could be covered with lava and ash from the many nearby volcanoes. Hot lava would melt some of the ice, but the heat may not have been enough to melt all the ice. So, there may have been a thick layer of lava and ash sitting on top of ice. The ice is much less dense; consequently, it would rise through the denser material that covers it. Strange shapes could result. This principle is like when one pulls a ball down int a swimming pool. The ball would want to go up through the water. On Earth this type of even occurs. The bodies that form are called diapirs. Sometimes salt deposits covered by sediment move upward on the Earth. Diapir comes from Greek diapeirein, which means “to pierce" in reference to how one lower density body pierces or moves through another.<ref> Fastook1, J. and J. Head. 2023. HELLAS BASIN, MARS: RIM-WALL-FLOOR GLACIATION IN THE LATE NOACHIAN-EARLY HESPERIAN AND INTERACTIONS WITH SUPERPOSED LAVA FLOWS. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1330.pdf</ref>

Pictures of these features can look like abstract art.

[[File:Twisted Terrain in Hellas Planitia.jpg|600pxr|Twisted Terrain in Hellas Planitia, but actually located in Noachis quadrangle. Imagine trying to walk across this. Image taken with HiRISE.]]

Twisted Terrain in Hellas Planitia, but actually located in Noachis quadrangle. Imagine trying to walk across this. Image taken with HiRISE.

<gallery class="center" widths="380px" heights="360px">
ESP 048830 1415ridges.jpg|Layered features on floor of Hellas Planitia This may be an example of honeycomb terrain that is not yet completely understood.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 055080 1425twistedbands.jpg|Twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program

File:ESP 055212 1420taffypull.jpg|Twisted bands on the floor of Hellas Planitia These twisted bands are also called "taffy pull" terrain.

</gallery>

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Floor features in Hellas Planitia

[[File:ESP 055146 1425ridges.jpg|600pxr|Wide view of twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program]]

Wide view of twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program

==Gullies on Dunes==

Gullies are found on some dunes. These are somewhat different than gullies in other places, like the walls of craters. Gullies on dunes seem to keep the same width for a long distance and often just end with a pit, instead of an apron. Many of these gullies are found on dunes in Russell Crater.

<gallery class="center" widths="380px" heights="360px">

ESP 020217 1255dunechannels.jpg|Wide view of dunes in Russell Crater, as seen by HiRISE Many narrow gullies are visible.

20217 1255dunechannelsclose.jpg|Close view of the end of gullies in Russell Crater Note: These type of gullies do not usually end with an apron.

20217 1255dunechannelsclosetop.jpg|Close view of the end of gullies in Russell Crater

ESP 020217 1255dunesclosecolor.jpg|Close, color view of the end of gullies in Russell Crater, as seen by HiRISE
</gallery>

==Channels==

<gallery class="center" widths="380px" heights="360px">

File:ESP 056981 1415channels.jpg|Channels
File:ESP 053698 1485channel.jpg|Channel, as seen by HiRISE under HiWish program
</gallery>

== Other scenes from Noachis quadrangle ==

<gallery class="center" widths="380px" heights="360px">

46417 1425straightridges.jpg|Ridges, as seen by HiRISE under HiWish program
48159 1310highcenterpolygons.jpg|High center polygons Boxes are drawn around two individual polygons.

ESP 048184 1470moundsbrains.jpg|Wide view of mounds and brain terrain
48184 1470moundsbrains.jpg|Close view of mounds and brain terrain
ESP 049226 1480boulderslighttoned.jpg|Light-toned material Light-toned material is often associated with minerals that formed in water.
49226 1480boulderslighttoned.jpg|Close view of surface, showing boulders and light-toned material
ESP 049674 1470flow.jpg|Flow or glacier
ESP 051138 1460ridges.jpg|Wide view showing flows and ridges

</gallery>

==See also==

*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[HiWish program]]
*[[How are features on Mars Named?]]
*[[Mars Global Surveyor]]
*[[Martian gullies]]
*[[Rivers on Mars]]

== External links ==

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]
* https://www.youtube.com/watch?v=483HcpqyMNU Banded Flow Terrain in Hellas Basin

==References==
{{reflist|colwidth=30em}}

==References==
{{reflist|colwidth=30em}}

Water

2023-03-20T23:26:13Z

Suitupandshowup: /* External links */ added to list

[[Image:GlassOfWater.jpg|thumb|200px|right|A glass is filled with drinking water.]]

'''Water''' is a chemical compound consisting of a single [[oxygen]] atom bonded to two [[hydrogen]] atoms (''chemical symbols:'' H2O). Water is essential to all known forms of life, and its unique properties make it invaluable for most industrial processes. While water in the liquid phase is abundant on [[Earth]], its icy deposits on [[Mars]] make it into a critical resource to be treasured.

==Evidence for water on Mars==

[[Image:388886main_mars_ice_226x170.jpg|thumb|226px|right|A new crater full of melting ice, as seen from the Mars Reconnaissance Orbiter.]]

[[File:PIA15090nirgalvallismariner9.jpg|thumb|226px|left|Nirgal Vallis, as seen by Mariner 9 This is one of the first images to show evidence of past water on Mars.]]

Starting in 2004, the evidence of the presence of water on Mars has been mounting.

===Past liquid water===
Mars shows evidence of extensive liquid water flowing on its surface in the past and it is the focus of many Mars missions to find out how this water has leaked away over the millennia.

The 1996 [[Mars Pathfinder]] mission discovered plentiful evidence that its landing site, [[Ares Vallis]], was once the bottom of a huge valley system eroded by ancient water.

In 2004, the [[Opportunity]] rover discovered geological markers - stratification and cross-bedding - near its landing site which pointed to significant flows of water at some time in Mars' history.<ref>Michael P. Lamb, John P. Grotzinger, John B. Southard, Nicholas J. Tosca, 2012. "Were Aqueous Ripples on Mars Formed by Flowing Brines?", Sedimentary Geology of Mars, John P. Grotzinger, Ralph E. Milliken. <nowiki>https://doi.org/10.2110/pec.12.102.0139</nowiki></ref>

The Mars Express Orbiter used [[Imaging Spectroscopy|imaging spectroscopy]] to detect hydrated minerals in 2005, strong evidence that surface water was once present in large amounts and for a long duration.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #1. Hydrated minerals – evidence of liquid water on Mars. <nowiki>https://sci.esa.int/web/mars-express/-/51821-1-hydrated-minerals-ndash-evidence-of-liquid-water-on-mars</nowiki></ref>

Further support for the historic existence of flowing water comes from the first observations made by NASA's [[Mars Reconnaissance Orbiter]] (launched in 2005) where the High Resolution Imaging Science Experiment (HiRISE) camera spotted small fractures and cracks in the Martian canyon, [[Candor Chasma]]. The cracks analyzed show signs of mineral alteration in the rock exposed - a sign that liquid water once flowed through these sub-surface pipes.

:"''What caught my eye was the bleaching or lack of dark material along the fracture. That is a sign of mineral alteration by fluids that moved through those joints. It reminded me of something I had seen during field studies in Utah, that is light-tone zones, or 'haloes,' on either side of cracks through darker sandstone''" - Dr. Chris Okubo, a geologist at the University of Arizona, Tucson.

Although this is a sign that the liquid water has since disappeared from these cracks and fractures in the canyon rock, it is interesting to find evidence for ancient water in abundance.

===Current water ice===
Today, water on Mars appears to be concentrated in Martian polar ice, suggesting Mars may once have had a warmer climate, slowly cooling as the atmosphere became a more inefficient insulator for the meager heating from the distant Sun. There appears to be very large amounts of water frozen into the regolith just bellow the surface. These areas may exist even at the Martian Equator.

In 2004 the [[Mars Express]] orbiter detected spectral evidence of water in the south pole's ice cap and the surrounding area, which ruled out the possibility that the southern ice cap consisted of only carbon dioxide ice.<ref>European Space Agency. March 17, 2004. Water at Martian south pole. https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Water_at_Martian_south_pole</ref>

In 2005, [[Mars Express]] located an area of solid water ice near the north pole.

The Phoenix lander confirmed in 2008 that water ice is not limited to the extreme polar regions.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref>

Photos from the [[Mars Reconnaissance Orbiter]] show frozen water just below the Martian surface (see photograph). Surprisingly the location is far away from the poles (43.28 degrees north latitude, 164.22 degrees east longitude), which raises the hope of large amounts of water all over the planet.
<ref>[http://www.nasa.gov/mission_pages/MRO/news/mro20090924.html Mars Reconnaissance Orbiter Sees Ice Exposed by Meteor Impact]</ref>

====Abundance====
[[Image:MARSIS.jpg|thumb|200px|right|A MARSIS map of Mars' south pole ice deposits.]]
On March 15, 2007, [[Mars Express]]' mission control released more news of extensive frozen water discovered at the Martian [[south pole]]. These new and highly accurate measurements predict that if the ice were to be melted, the whole planet would be covered in a liquid layer 11 meters deep.<ref>The European Space Agency. September 1 2019. Mars Express science highlights: #4. Probing the polar regions. <nowiki>https://sci.esa.int/web/mars-express/-/51824-4-probing-the-polar-regions</nowiki></ref> Although it has been known for many years that the poles have an abundance of ice, it has never been measured to this degree of accuracy. The data comes from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) currently mapping the north pole to gain a better understanding of how much frozen water may be contained there. MARSIS can probe over 2 miles below the Martian surface and has found extensive layered deposits of ice.

===Current liquid water===

Future manned exploration on Mars will require a source of water whether it is in the form of ice or sub-surface [[aquifers]]. The [[Mars Express]] orbiter has uncovered some confusing measurements suggesting there may be liquid water accompanying all that ice. MARSIS bounced back data suggesting at least 90% of the layered deposits under the polar cap are indeed supplies of ice, but a thin layer resembling liquid water is also evident. It is hard to understand the existence of liquid water at the extremely low temperatures predicted. Perhaps high pressures or small geological processes may explain these observations. Another orbiter, NASA's Mars Global Surveyor, has also returned some exciting new evidence for the existence of new flows of liquid water on the Martian surface away from the frozen poles. {{science question|What pressures are required to keep water in a liquid phase at temperatures as low as that on the surface of Mars? - [[User:Ioneill|Ioneill]]}}

The [[Mars Global Surveyor]] arrived at the Red Planet on September 11, 1997 and returned a decade of data on the evolution of the planet before it was lost in November 2006 through energy loss. It was Mars' longest operational artificial satellite. The Mars Orbiter Camera (MOC) onboard revealed new deposits possibly carried as sediment by flowing water in two locations in the past 7 years (press release dated December 6, 2006)<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref>. In images taken in August 1999 and September 2006 of the same location ([[Centauri Montes]] Region), a bright deposit measuring several hundred meters long is evident in the 2006 image but not in the 1999 image. A similar feature was observed at a different location from 2001 to 2005 at [[Terra Sirenum]]. It is worth noting that both locations are in equatorial regions, not usually associated with ice or liquid water. This suggests liquid water remains a characteristic of the Mars landscape, if only sporadically. These discoveries have increased the enthusiasm for the search for [[microbes|microbial life]], but the implications for manned exploration are huge. If there are pockets of liquid water just below the surface, Mars may yet be able to provide our future pioneers with natural springs more familiar on Earth.
[[Image:Water_deposit.jpg|thumb|left|200px|Evidence from the [[Mars Global Surveyor]] MOC instrument that spurts of liquid water may sporadically flow on the Martian surface]]
However, surface water on Mars is short-lived. The Martian atmosphere is very thin (a pressure of 7 millibars, <1% that of Earth's thick atmosphere) and cold (an average global temperature of -55°C or -67F), these two factors deny any long-term existence of liquid water. Surface liquid water will quickly freeze and [[sublimation|sublime]] into the atmosphere, bypassing the [[triple point|liquid phase]]. This phase transition for water on Mars is much like the phase transition for liquid carbon dioxide on Earth when it is released from a CO2 fire extinguisher to produce dry ice snow and CO2 gas. The phase transition for H2O on the surface of Mars occurs below the "[[triple point]]" on the phase diagram so the recent observations of sediment on the surface will have been deposited very quickly by short lived "spurts" of water. Just how short-lived these spurts of water are it is unknown, but a significant volume must have created a formidable river to carry sediment several hundred meters.

At times, the humidity of the Martian atmosphere can reach 100% (at Mars' temperature and pressure). If the temperature was high, salty brines could last several minutes on the Martian surface.

Although there may be other explanations for these long "channels" of sediment, such as rock slides or wind-blown [[sand]] features, the appearance of the deposits seem very water-like. Michael Malin of Malin Space Science Systems, a mission scientist for the MOC says, "''The shapes of these deposits are what you would expect to see if the material were carried by flowing water... they have finger-like branches at the downhill end and easily diverted around small obstacles''".<ref>[http://mars.jpl.nasa.gov/mgs/newsroom/20061206a.html NASA Press Release: ''NASA Images Suggest Water Still Flows in Brief Spurts on Mars'']</ref> It is also possible that other liquids such as 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 1,3-propanediol, ethylene glycol and related liquids could be responsible for [[Recent Liquid Flow on Mars|fluid flow features]] on Mars. While such liquids would be relatively more rare than water, the resistance to freezing of such liquids and mixtures of such liquids with water would allow them to cause fluid flow effects where pure liquid water is impossible.

==Water production==
Water production on Mars for settlement use or for exploration uses can take many forms. As a prime [[In-situ resource utilization|In-situ]] resource the presence of water on Mars is one of its main attractions. Further exploration is needed to determine if the water is available in a relatively pure form, or if it will contain salts and other chemical contaminants requiring water treatment.

===Atmosphere===
The Martian [[atmosphere]] contains water vapour (which on occasion can reach 100% humidity). However, it is normally dry and very thin, which makes extracting water slow and energy intensive. With a device similar to an [[atmospheric mining|air dehumidifier]] the production of water should be feasible all over the planet's surface. An [[experimental setup#water out of the atmosphere|experimental setup]] is necessary to find out all about the viability of this approach.

"The University of Washington has designed an in situ resource utilization system to provide water to a life support system in the laboratory module of the NASA Reference Mission to Mars. This system, the Water Vapor Adsorption Reactor (WAVAR), extracts water vapor from the Martian atmosphere by adsorption in a bed of type 3A zeolite molecular sieve. The zeolite 3A adsorbs the water vapor until nearly saturated and is then heated within a sealed chamber by microwave radiation to drive off the water for collection. The water vapor flows to a condenser where it freezes and is later liquefied for use in the life support system. In the NASA Reference Mission, water, methane, and oxygen are produced for life support and propulsion via the Sabatier/Electrolysis process from seed hydrogen brought from Earth and Martian atmospheric carbon dioxide. In order for the WAVAR system to be compatible with the NASA Reference Mission, its mass must be less than that of the seed hydrogen and cryogenic tanks apportioned for life support in the Sabatier/Electrolysis process. The WAVAR system is designed for atmospheric conditions observed by the Viking missions, which measured an average global atmospheric water vapor concentration of approx. 2 x 10-6kg/cubic meter. WAVAR performance is analyzed taking into consideration hourly and daily fluctuations in Martian ambient temperature and the corresponding effects on zeolite performance." <ref> Sergio Adan-Plaza, Kirsten Carpenter, Laila Elias, Rob Grover, Mark Hilstad, Chris Hoffman, Matt Scheider, & Adam Bruckner. (1998). Extraction of Atmospheric Water on Mars for the Mars Reference Mission. Lpi.usra.edu. Retrieved 15 November 2021, from https://www.lpi.usra.edu/publications/reports/CB-955/washington.pdf.</ref>

===Caves===
Since the discovery of [[caves]] scientists believe in the possibility of water ice on the ground of the caves. Water ice is abundant under the ground at least near the poles, and probably elsewhere too.

===Glaciers===
The [[Mars Reconnaissance Orbiter]] has found evidence of [[glacier|glaciers]] covered in regolith.<ref>http://www.nasa.gov/home/hqnews/2008/nov/HQ_08-304_MRO_BuriedGlaciers.html</ref> Radar reflection data indicates that these are not Rock Glaciers that have been previously suspected on Mars, but instead are thick glacial ice covered in a thin layer of debris. The buried glaciers lie in the [[Hellas Planitia|Hellas Basin]] region of Mars' southern hemisphere with similar aprons detected extending from cliffs in the northern hemisphere.

===Regolith===
Water is present in the martian regolith both as ice and as hydrated minerals. In addition, a recent paper has shown that a huge amount of water has been absorbed by rocks. On Earth, plate Tectonics takes these hydrated minerals and melts them, where water can return to the surface via vulcanism. On Mars the water remains in these minerals. <ref>https://science.sciencemag.org/content/early/2021/03/15/science.abc7717 - Long term drying of Mars by sequestration of Ocean-scale volumes of water in the crust</ref>

One way to obtain water from regolith is to cover a spot with a clear cover, heat it with focused sunlight (mirrors), and let the water vapor condense on the cover. Collect the condensate on the edges of the cover. At ground level the Martian atmosphere has a pressure of 6.518 millibars or 0.095 psi as compared to the Earth's sea level atmospheric pressure of 14.7 psi. <ref>Mars. Mars.nasa.gov. (1997). Retrieved 15 November 2021, from https://mars.nasa.gov/MPF/mpf/realtime/mars2.html.</ref> Boiling point of water at 6.518 millibars: 1.5 degC, 34.7 degF. <ref>Water - Boiling Points at Vacuum Pressure. Engineeringtoolbox.com. (2021). Retrieved 15 November 2021, from https://www.engineeringtoolbox.com/water-evacuation-pressure-temperature-d_1686.html.</ref>

"Excavated regolith can be processed by crushing, dry-grinding, and running it through a continuous feed electrically heated rotary kiln, heating to temperatures above 500˚C to decompose perchlorates, <ref>James D. Little (2019). 3: Aeneas Complex: A Plan For A Sustainable, Permanent 1000 Person Settlement On Mars in the book Mars colonies: Plans for Settling the Red Planet (p. 58).</ref><ref>Marvin, G., Woolaver, L., Thermal Decomposition of Perchlorates, Industrial & Engineering Chemistry Analytical Edition, 1945, Vol. 17, Iss. 8, pp. 474-476.</ref><ref>Bruck. A., Sutter, B., Ming, D., Mahaffy, P., Thermal Decomposition of Calcium Perchlorate/Iron-mineral Mixtures: Implications of the Evolved Oxygen from the Rocknest Eolian Deposit in Gale Crater, Mars., 45th Lunar and Planetary Science Conference, Mar. 2014.</ref> 
[Ca(H2O)4](ClO4)2 -> Ca(ClO4)2 + 4H2O 
oxides, sulfates, carbonates, and nitrates driving off gases and water vapor. The gases are processed through aseries of PSA equipment. The remaining regolith can be sifted and sorted, using various ore processing techniques, such as magnetic separation for iron rich minerals, and sifting to produce aggregate mixtures suitable for producing 3D printed sulfur concrete."

===Polar regions===
The martian polar regions have extensive ice caps as well as ice filled craters, such as the [[Korolev]] crater, that could serve as water sources. As the poles are usually extremely cold, sources closer to the equator would be more useful for future martian settlements. Note that permafrost has been detected at all latitudes, but above 30 degrees latitude, surface ice is found fairly often.

==Uses==

===Drinking water===
The [[human]] metabolism requires a regular intake of fresh water. Pure liquid water is non-existent on Mars but there is abundant frozen water and hydrated minerals. Since getting liquid water for use will require some industrial effort, the [[recycling]] of all excretion would provide advantages in reducing water use. There are two ways: Wastewater can be [[Potable_water_treatment|treated]], which is partially done on the [[ISS]] already. Alternatively, the water can be kept in a nearly natural cycle, using parts of the [[greenhouse]]s for [[biological wastewater treatment]].

The concentration of deuterium in Martian hydrogen and thus in Martian water is between five and thirteen ten-thousandth-parts.<ref>[http://www.sciencemag.org/content/240/4860/1767.abstract abstract in ''Science'']</ref> or about six times the relative abundance on Earth. Still this concentration is far from the 25% of the body's content of hydrogen that would need to be substituted by deuterium before there are any serious health effects. Deuterium is not a cumulative poison. At about one thousandth part of the hydrogen in Martian water, deuterium would be excreted as fast as it is consumed and would not be a health problem.

===Industrial processes===

Many industrial processes considered for a Mars settlement, in particular the production of [[methanol]] and [[methane]] and other hydrocarbons require hydrogen. This can be obtained by [[electrolysis]] or via thermolysis such as the Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2006.05.013</ref> or the Zinc/Sulfur/Iodine cycle<ref>https://doi.org/10.1016/j.ijhydene.2015.11.049</ref>. In electrolysis or basic thermolysis, [[Oxygen O2]] is produced as a byproduct. In the Zinc/Sulfur/Iodine cycle, CO2 and H2O are inputs and the outputs are CO and H2. CO is industrially useful in the production of [[methanol]] and other [[Hydrocarbon_synthesis|hydrocarbons]], as well as in mineral refining via the [https://en.wikipedia.org/wiki/Mond_process Mond process]. The H2 can also be combined with atmospheric N2 using a [https://en.wikipedia.org/wiki/Haber_process Haber reactor] to produce [[ammonia]].

Most other processes require the use of significant quantities of water as a [[solvent]] for reagents such as [[acid]]s or [[ammonia]] or a a coolant for high temperature systems.

Power sources which rely on heat engines (such as [[nuclear power]]) require a heat sink to provide the heat differential required for the engine to run. Water or Ice make good materials for this heat sink as they are dense and have high thermal mass. The ice of [[korolev|Korolev Crater]] has been suggested as a potential heat sink sufficient to provide for colony scale power generation.

[[Deuterium]] from martian water may provide a source of fusion fuel for future energy production. Note that deuterium is about six times more concentrated on Mars than on Earth, and may form a viable export.

[[Methanol]] and [[methane]] may be used to feed [[Biological_reactors|methanotrophs]] to produce food or other biologically produced industrial materials.

==See Also==

*[[Martian features that are signs of water ice]]
*[[Sublimation]]
*[[Water Infrastructure|Water infrastructure]] and waste water treatment
*"Mars: A Warmer Wetter Planet", by Jeffrey S. Kargel, ISBN 1-85233-568-8. This important book collected the evidence of water on Mars, and put to rest the idea that Mars had always been a dry planet.

==External links==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf

*[https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]

*[http://en.wikipedia.org/wiki/Water Wikipedia page on water]
*[http://mars.jpl.nasa.gov/express/mission/sc_science_marsis02.html Searching for water with the Mars Express MARSIS instrument.]
*[https://en.wikipedia.org/wiki/Water_on_Mars Wikipedia page on water on Mars]

*[https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]
*[https://www.youtube.com/watch?v=QWcdAvFN_q0 James Wray - The Search for Water and Life on Mars (and Beyond) (November 15, 2018)]
*[https://www.youtube.com/watch?v=b4hCWIQsyps Mars: Ancient Water, Present Day Ice]
*[https://www.youtube.com/watch?v=EJk0hS4_gz4 Water on Mars and the Potential for Martian Life]
*[https://www.youtube.com/watch?v=GX9XzRyuYLc Oceans and Life on Mars]

===References===
<references />

Glaciers on Mars

2023-03-20T23:25:13Z

Suitupandshowup: /* External links */ added to list

{{Mars atlas}}
Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

Since the 60’s, as our spacecraft have studied Mars with more and more advanced cameras and other instruments, we have found more and more evidence for glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 | bibcode=2005Icar..174..321A</ref> On Mars these glaciers are covered with rock and dust debris a few meters to a few tens of meters thick. Although Mars today seems too dry for any glaciers, this covering material has protected the underlying ice. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> One would think that under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>

==Water for Future Colonists==

The discovery of ice on Mars is important because future colonists may be able to tap the ice for water. Besides the obvious uses of water to humans, water can be broken down with electricity to form hydrogen and oxygen. Hence, people living on Mars could be supplied with oxygen to breathe and hydrogen for fuel. We have known for many decades that the ice caps, called the polar layered deposits, contain ice, but they are far away from where it is easy to land rockets. Glaciers on the planet are much closer to the equator and widespread about the planet. Perhaps, the task of obtaining water will be done with automated machines. Already scientists here on Earth are building devices that can drill into the ground and melt any ice for water.<ref> https://www.nasa.gov/press-release/nasa-s-mars-ice-challenge-follow-the-water</ref> <ref> ↑ http://triblive.com/news/education/career/13040517-74/cmu-team-finalist-for-nasas-mars-ice-challenge-to-drill-for-water</ref> Recent studies have sought to determine the nature of these covering layers to find out how best to extract water.<ref> Baker, D., L. Carter. In press. Probing supraglacial debris on Mars 1: Sources, thickness, and stratigraphy. Icarus. https://doi.org/10.1016/j.icarus.2018.09.001</ref> Our advanced cameras on satellites orbiting the Red Planet have mapped the exact locations of hundreds of glaciers and glacier-like features that may all contain useable ice. We know where the water is!
From early on, images from satellites have shown features that resembled glaciers on the Earth. Of particular significance was the angle at the end of the glacier. The angle was far steeper than geologic features like landslides. Large stretches of landscape called “fretted terrain,” after the forehead of someone who worries or frets show signs of glacier activity. This terrain is characterized by wide, flat floored valleys surrounded by steep cliffs. The floors contained lines in early Viking photographs.<ref>Squyres, S. 1978. Martian Fretted Terrain: Flow of Erosional Debris. Icarus: 34, 600-613.</ref> Many isolated mesas are present. Furthermore, mesas are surrounded by wide aprons of material that today we know to be debris covered glaciers.

==Real Glaciers==

<gallery class="center" widths="380px" heights="360px">
File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.
File: Wikielephantglacier.jpg|Glacier in Greenland
</gallery>

With better cameras, it was observed that some mesas had what resembled glaciers in the valleys. A big advance in understanding Martian geology came when the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor gave us exact elevations for the whole planet; from then on, we could figure out slopes. Where the land was tilted, the glacier-forms moved down slope. Also, researchers observed that when the glacier left the valley and reached a wider, flatter place, it spread out, just as glaciers on Earth do. In some craters there are large glaciers shaped like giant tongues, so they have been called tongue-shaped glaciers. <ref>Forget, F., et al. 2006. Planet Mars Story of Another World. Praxis Publishing, Chichester, UK. ISBN|978-0-387-48925-4</ref>

[[File:Mars_MGS_colorhillshade_mola_1024.jpg |thumb|300px|center|Topographic map produced with MOLA measurements This map showed that glacial features move downhill.]]

[[File:Tongueismenius.jpg |thumb|300px|left| Glacier shaped like a giant tongue, as seen by HiRISE under HiWish program ]]

==Lobate Debris Aprons==

So for sure many things look like glaciers, but looks can be deceiving. Conclusive proof came after radar studies confirmed that many of these features were actually ice with only a thin surface covering. Shallow Subsurface Radar (SHARD) was the radar system on board the Mars Reconnaissance Orbiter that was used. It found that features, called lobate debris aprons (LDA’s), around mesas were actually glaciers, as had long been expected. <ref name="Plaut, J. 2008">Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> Ice was found both in the southern and northern hemispheres. <ref>cite journal | last1 = Holt | first1 = J. | last2 = Safaeinili | first2 = A. | last3 = Plaut | first3 = J. | last4 = Head | first4 = J. | last5 = Phillips | first5 = R. | last6 = Seu | first6 = R. | last7 = Kempf | first7 = S. | last8 = Choudhary | first8 = P. | last9 = Young | first9 = D. | last10 = Putzig | first10 = N. | last11 = Biccari | first11 = D. | last12 = Gim | first12 = Y. | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322| issue = | pages = 1235–1238| doi = 10.1126/science.1164246 | pmid=19023078|</ref> <ref>cite journal | last1 = Plaut | first1 = J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J. | last4 = Phillips | first4 = R. | last5 = Head | first5 = J. | last6 = Seu | first6 = R. | last7 = Putzig | first7 = N. | last8 = Frigeri | first8 = A. | year = 2009 | title = Radar evidence for ice in lobate debris aprons in the midnorthern latitudes of Mars | url = | journal = Geophys. Res. Lett. | volume = 36| issue = | page = | doi = 10.1029/2008GL036379 |</ref> <ref>Holt, J., et al. 2008. Radar Sounding Evidence for Ice within Lobate Debris Aprons, near Hellas Basin, Mid-southern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2441.pdf</ref>

<gallery class="center" widths="380px" heights="360px">
[[Image: Mars Reconnaissance Orbiter spacecraft model.png |thumb|200px|right|Artist view of Mars Reconnaissance Orbiter ]]
File:800px-Wideviewlda42n18e.jpg|Lobate debris apron (LDA) around a mesa Radar proved that a LDA is mostly ice.
</gallery>

==Lineated Valley Fill==

Another ice-rich feature is called lineated valley fill (LVF). <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref> https://www.uahirise.org/ESP_026414_2205</ref>
It covers many of the wide, flat valley floors of fretted terrain. Probably formed from the interaction of glaciers coming out of valleys and of mesas eroding, it has similar surface appearance of other supposed glaciers, including LDA. It looks like the human brain. Since the material covering ice is shaped into something resembling the human brain, it is named brain terrain. Two types, open and closed have been identified. The closed still holds an ice core. Brain terrain starts to form when cracks occur on an ice-rich surface. [[Sublimation]] along the cracks turns the cracks into small valleys. Regions called Nilosyrtis Mensae, Protonilus Mensae and Deuteronilus Mensae display many examples of LVF. The Ismenius Lacus quadrangle and Hellas quadrangle contain many valleys exhibiting lineated valley fill.<ref>Mellon, M. 1997. Small-scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost. J. Geophysical Res: 102. 25,617-625,628.</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref> <ref name="Souness, C 2013">cite journal | author = Souness C., Hubbard B. | year = 2013 | title = An alternative interpretation of late Amazonian ice flow: Protonilus Mensae, Mars | url = | journal = Icarus | volume = 225 | issue = | pages = 495–505 | doi=10.1016/j.icarus.2013.03.030 |</ref> <ref name="Noach">cite journal |author1=Head, J. |author2=D. Marchant |lastauthoramp=yes| date = 2006 | title = Modification of the walls of a Noachian crater in northern Arabia Terra (24E, 39N) during mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of lobate debris aprons and their relationships to lineated valley fill and glacial systems | journal = Lunar Planet. Sci | volume = 37 | page = Abstract # 1126</ref> <ref>cite journal | author = Kress, A., J. Head | date = 2008 | title = Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice | journal = Geophys. Res. Lett. | volume = 35 | page = L23206–8 | doi=10.1029/2008gl035501|</ref> <ref>cite journal | author = Baker, D. | date = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | journal = Icarus | volume = 207 | pages = 186–209 | doi = 10.1016/j.icarus.2009.11.017 | last2 = Head | first2 = James W. | last3 = Marchant | first3 = David R. </ref> <ref>cite journal |author1=Kress., A. |author2=J. Head |lastauthoramp=yes| date = 2009 | title = Ring-mould craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age | journal = Lunar Planet. Sci | volume = 40 | page = abstract 1379</ref>

<gallery class="center" widths="380px" heights="360px">
File:56544 2200lvfbrains.jpg|Wide view of Lineated Valley Fill
File:56544 2200lvf.jpg|Close view of Lineated Valley Fill The location is the Ismenius Lacus quadrangle.
File:54527 2225brainsclosecolor.jpg|Close view of brain terrain Brain terrain covers many types of Martian glaciers.
File:ESP 053642 2225brainslabeled.jpg|Closed cell brain terrain still contains a core of ice. When the ice leaves it becomes open cell brain terrain.
</gallery>

==Concentric Crater Fill==

Concentric crater fill (CCF) is a third easily identifiable landscape that is covered with brain terrain and loaded with water. Craters with CCF are shallow. Even though they started out with a deep bowl shape, today they are full. We know how deep the crater was when formed because crater studies have found a relationship between the diameter of a crater and its original depth. For example, in many parts of Mars the diameter of a crater is 10 times the depth.<ref>http://adsabs.harvard.edu/full/1993mppf.proc....1B</ref> So if see that a crater is 10 km across, we know that it started out being 1 km deep. These craters may be big, but they are shallow. Scientists believe they are full of dust and ice. As material moves down crater walls toward the center, concentric lines of brain terrain are created. <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref> <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust .
File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed.
</gallery>

==Source of Ice==

Multiple studies imply there is plenty of ice on Mars. Ice is abundant from about 30 degrees latitude up to the poles. <ref name="HeadDistn">cite journal | last1 = Head | first1 = J. W. | display-authors = 1 | last2 = et al | year = 2006 | title = Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change | url = | journal = Earth and Planetary Science Letters | volume = 241 | issue = 3| pages = 663–671 | doi=10.1016/j.epsl.2005.11.016 |</ref> <ref>Kieffer, H., et al. (eds). 1992. Mars. University of Arizona Press. Tucson. ISBN 0-8165-1257-4</ref> How did it get there? It is now widely believed that snow and ice-coated dust drops from the sky when the climate of Mars changes--as it frequently does. <ref>cite journal | last1 = Touma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = | pages = 1294–1297 | doi=10.1126/science.259.5099.1294 | pmid=17732249|</ref> <ref name="ReferenceB">cite journal | last1 = Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = | pages = 343–364 | doi=10.1016/j.icarus.2004.04.005 |</ref> Calculations reveal that the tilt of Mars drastically changes due to the lack of a large moon to stabilize it.<ref>https://www.uahirise.org/hipod/ESP_034132_1750</ref> When the tilt changes, the climate changes. At times, the ice in the polar deposits leaves and goes to mid-latitudes.<ref>http://hirise.lpl.arizona.edu/PSP_002917_2175</ref> <ref>Forget, F., et al. 2006. Planet Mars Story of Another World. Praxis Publishing, Chichester, UK. ISBN|978-0-387-48925-4</ref> During this time, ice in the cap sublimates, and thick snow falls in mid-latitudes — the zones where concentric crater fill, lineated valley fill and lobate debris aprons are common.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0 </ref> <ref name="obliq">cite journal | author = Head, J. | date = 2006 | title = Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for late Amazonian obliquity-driven climate change | journal = Earth Planet. Sci. Lett. | volume = 241 | pages = 663–671 |doi=10.1016/j.epsl.2005.11.016 | issue = 3–4| last2 = Marchant | first2 = D.R. | last3 = Agnew | first3 = M.C. | last4 = Fassett | first4 = C.I. | last5 = Kreslavsky | first5 = M.A. </ref> <ref>cite journal | author = Levy, J. | display-authors = etal | date = 2007 | title = Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary | journal = J. Geophys. Res. | volume = 112 | doi=10.1029/2006je002852 |</ref> <ref>Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. </ref> It is deposited as something called latitude dependent mantle. Over time, some ice disappears and leaves a covering lag deposit that prevents further loss of ice. <ref name="Mellon, M. 1995">cite journal | last1 = Mellon | first1 = M. | last2 = Jakosky | first2 = B. | year = 1995 | title = The distribution and behavior of Martian ground ice during past and present epochs | url = | journal = J. Geophys. Res. | volume = 100 | issue = | pages = 11781–11799 | doi=10.1029/95je01027 |</ref> <ref name="Mellon, M. 1995"/> <ref>cite journal | last1 = Schorghofer | first1 = N | year = 2007 | title = Dynamics of ice ages on Mars | url = | journal = Nature | volume = 449 | issue = | pages = 192–194 | doi=10.1038/nature06082 | pmid=17851518|</ref> Also, dust and other debris collect on the surface. Together, these coverings help to build up an ice-rich, long lasting smooth mantle that can eventually generate glaciers. If it gets thick enough, the ice mass will be pulled downhill by gravity. On Earth, glaciers often melt at the base. The resulting water helps the glacier slide. However, glaciers also move from internal movement of ice crystals sliding over each other. It flows like a soft plastic.<ref> http://www.geography-site.co.uk/pages/physical/glaciers/origin.html</ref> <ref>Earth Science. 2001. Holt Science &Technology. New York</ref> This plastic movement will not change the shape of the ground under the glacier; however, the glacier will still carry debris and make structures called moraine.

<gallery class="center" widths="380px" heights="360px">
46444 2225mantle.jpg|Latitude dependent mantle
File:ESP 028352 2245glacier.jpg|Glacier that has lost much of its ice, but has built moraines
File:Moraines52720 2250.jpg|Old Glacier with multiple moraines indicated with arrows When the glacier retreated it stopped at times and left behind a moraine. Material is still transported to the end (snout) of a glacier when it is not advancing.
</gallery>

Moraines are common on Mars. <ref>Milliken, R., J. Mustard, D. Goldsby. 2003. Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images. J. Geophys. Res. 108. </ref> It is believed that most glaciers on Mars are “cold based” that is they do not melt. Remember, under current conditions ice does not melt, rather it changes directly to a gas in a process called [[sublimation]]. We do not know if any ice melted in the past. We may understand the situation much better after we study data from the [[InSight Mission]] which landed on Mars at the end of November 2018. InSight will measure the heat flow. A combination of high heat flow and pressure from thick ice, may have generated sufficient heat to cause some melting.

[[File:PIA17358-MarsInSightLander-20140326.jpg|600pxr|Labeled drawing of InSight Lander]]

==Other Possible Glaciers==

Besides features that look like terrestrial glaciers, LDM, LVF, and CCF; there are other shapes that may be glaciers. <ref>Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127</ref> <ref>Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128</ref> <ref>Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671</ref> <ref>Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33</ref> They appear as curved ridges and have been called various names by different researchers. Some of the names are Viscus Flow Features (VFF), arcuate ridges, Glacial-like Flows (GLF), Glacier-like Forms (GLF), and Moraine-like Ridges (MLR). <ref> Milliken, R., et al. 2003. Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images. Journal of Geophysical Research: 108. Doi:10.1029/2002JE002005</ref> <ref>Berman, D., et al. 2005. The role of arcuate ridges and gullies in the degradation of craters in the Newton Basin regions of Mars. Icarus: 178, 465-486.</ref> <ref>cite journal
| last1 = Arfstrom | first1 = J
| last2 = Hartmann | first2 = W. | year = 2005
| title = Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships
| url = | journal = Icarus | volume = 174 | issue = | pages = 321–335
| doi=10.1016/j.icarus.2004.05.026 | </ref> <ref name="Hubbard B. 2011">cite journal
| last1 = Hubbard | first1 = B.
| last2 = Milliken | first2 = R.
| last3 = Kargel | first3 = J.
| last4 = Limaye | first4 = A.
| last5 = Souness | first5 = C.
| year = 2011 | title = Geomorphological characterisation and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars
| url = | journal = Icarus | volume = 211 | issue = | pages = 330–346
| doi=10.1016/j.icarus.2010.10.021 |</ref> <ref name="Hubbard B. 2011"/> <ref>http://www.antarcticglaciers.org/glacial-geology/glaciers-mars/</ref> Most lie in impact craters. Gullies are associated with many of them. These curved ridges may be created as snow and ice accumulate high on crater walls until gravity pulls them down. As they slide down, they may push material into ridges.

<gallery class="center" widths="380px" heights="360px">
File:Gullies and tongue-shaped glacier.jpg|Gullies and ridges that may be the remains of old glaciers Glaciers may have dropped moraine debris or pushed floor material into ridges.
File:44410 2195glacier.jpg|Ridge downslope from a gully This ridge in a crater may be created by a glacier.
</gallery>

==Glaciers on Volcanoes==

Most major Martian volcanoes display evidence of past glaciation. <ref name="HeadTropical">cite journal | last1 = Head | first1 = J. W. | display-authors = 1 | last2 = et al | year = 2005 | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal = Nature | volume = 434 | issue = 7031| pages = 346–351 | doi=10.1038/nature03359 | pmid=15772652|</ref> <ref name="SheanPavonis">cite journal | last1 = Shean | first1 = David E. | title = Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit | journal=Journal of Geophysical Research | volume = 110 | date = 2005 | doi = 10.1029/2004JE002360 | </ref> <ref name="HeadMarchantArsia">cite journal | last1 = Head | first1 = James W. | last2 = Marchant | first2 = David R. | year = 2003 | title = Cold-based mountain glaciers on Mars: western Arsia Mons | url = | journal = Geology | volume = 31 | issue = 7| pages = 641–644 | doi=10.1130/0091-7613(2003)031<0641:cmgomw>2.0.co;2|</ref>
<ref name="Hauber, E. 2005">Cite journal|author=Hauber, E. |date=2005 |title=Discovery of a flank caldera and very young glacial activity at Hecates Tholus, Mars |journal=Nature |volume=434 |pages=356–61|pmid=15772654|issue=7031|doi=10.1038/nature03423 |last2=Van Gasselt |first2=Stephan |last3=Ivanov |first3=Boris |last4=Werner |first4=Stephanie |last5=Head |first5=James W. |last6=Neukum |first6=Gerhard |last7=Jaumann |first7=Ralf |last8=Greeley |first8=Ronald |last9=Mitchell |first9=Karl L. |last10=Muller |first10=Peter |last11=Co-Investigator Team |first11=The Hrsc </ref> <ref>Scanlon, K., J. Head, D. Marchant. 2015. REMNANT BURIED ICE IN THE ARSIA MONS FAN-SHAPED DEPOSIT, MARS. 46th Lunar and Planetary Science Conference. 2266.pdf</ref>
<ref name="ReferenceA">cite journal | last1= Shean | first1= David E. | last2= Head | first2= James W. | last3= Fastook | first3= James L. | last4= Marchant | first4= David R. | title= Recent glaciation at high elevations on Arsia Mons, Mars: Implications for the formation and evolution of large tropical mountain glaciers| page= E03004 | date= 2007 | issue= E3 | volume= 112 | doi = 10.1029/2006JE002761 | journal= Journal of Geophysical Research | url=http://www.planetary.brown.edu/pdfs/3281.pdf | format = PDF | </ref> <ref name="Shean, D. 2005">Cite journal|author=Shean, D. |display-authors=etal |date=2005 |title=Origin and evolution of a cold-based mountain glacier on Mars: The Pavonis Mons fan-shaped deposit |journal=Journal of Geophysical Research |volume=110|issue=E5 |page=E05001 | doi = 10.1029/2004JE002360 |</ref> <ref name="Basilevsky, A. 2006">Cite journal|author=Basilevsky, A. |date=2006 |title=Geological recent tectonic, volcanic and fluvial activity on the eastern flank of the Olympus Mons volcano, Mars |journal=Geophysical Research Letters |volume=33 |issue=13 |pages=13201, L13201 |doi=10.1029/2006GL026396 |last2=Werner |first2=S. C. |last3=Neukum |first3=G. |last4=Head |first4=J. W. |last5=Van Gasselt |first5=S. |last6=Gwinner |first6=K. |last7=Ivanov |first7=B. A. </ref> Scientists now believe that glaciers exist on many of the volcanoes in Tharsis, including Olympus Mons, Ascraeus Mons, and Pavonis Mons.<ref>https://www.scienceinschool.org/2014/issue28/mars_glaciers</ref> <ref>cite journal | last1=Shean | first1=David E. | title=Origin and evolution of cold-based tropical mountain glacier on Mars: the Pavonis Mons fan-shaped deposit | journal=Journal of Geophysical Research | volume=110 | year=2005 | doi= 10.1029/2004JE002360 |</ref> <ref>cite journal | last1=Fassett | first1=C | last2=Headiii | first2=J | title=Valley formation on martian volcanoes in the Hesperian: Evidence for melting of summit snowpack, caldera lake formation, drainage and erosion on Ceraunius Tholus | url=http://www.planetary.brown.edu/pdfs/3408.pdf | format=PDF | journal=Icarus | volume=189 | pages=118–135 | year=2007| doi = 10.1016/j.icarus.2006.12.021 |</ref>
<ref>cite journal | last1= Plaut | first1= Jeffrey J. | last2= Safaeinili | first2= Ali | last3= Holt | first3= John W. | last4= Phillips | first4= Roger J. | last5= Head | first5= James W. | last6= Seu | first6= Roberto | last7= Putzig | first7= Nathaniel E. | last8= Frigeri | first8= Alessandro | title= Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars | journal= Geophysical Research Letters | volume= 36 | issue= 2 | pages= | year= 2009 | doi = 10.1029/2008GL036379 |url=http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2290.pdf | format=PDF |</ref> <ref>cite journal | title= Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars | url=http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2441.pdf | format=PDF | journal = Lunar and Planetary Science |volume=XXXIX | pages = 2441 |year=2008 |last1= Holt | first=J.W.| last2 = Safaeinili | first2 = A. | last3 = Plaut | first3 = J. J. | last4 = Young | first4 = D. A. | last5 = Head | first5 = J. W. | last6 = Phillips | first6 = R. J. | last7 = Campbell | first7 = B. A. | last8 = Carter | first8 = L. M. | last9 = Gim | first9 = Y. | last10 = Seu | first10 = R. | author11 = Sharad Team </ref >Many large mountains on Earth also have glaciers. It is cold on mountain tops. Snow often falls heavily there; therefore, one would expect glaciers on Martian volcanoes.

==Vast Ice Sheets==

Besides smaller glaciers around mesas, in craters, and on mountains, Mars may have had giant ice sheets, twice the area of the state of Texas.<ref>cite journal | last1 = Scanlon | first1 = K. | display-authors = 1 | last2 = et al | year = 2018 | title = | url = | journal = Icarus | volume = 299 | issue = | pages = 339–363| doi = 10.1016/j.icarus.2017.07.031</ref> <ref>Allen, C. 1979. Volcano-ice interactions on Mars. ''J. Geophys. Res.: Solid Earth (1978–2012)'', 84 (B14), 8048-8059.</ref> <ref>Howard, 1981</ref> <ref>cite journal | last1 = Kargel | first1 = J. | last2 = Strom | first2 = R. | year = 1992 | title = Ancient glaciation on mars | url = | journal = Geology | volume = 20 | issue = 1| pages = 3–7| doi = 10.1130/0091-7613(1992)020<0003:AGOM>2.3.CO;2 </ref> <ref>Head, J, S. Pratt. 2001. Extensive Hesperian-aged south polar ice sheet on Mars: Evidence for massive melting and retreat, and lateral flow and pending of meltwater. J. Geophys. Res.-Planet, 106 (E6), 12275-12299.</ref> Some researchers have estimated that one ice sheet was nearly a mile thick. Near the South Pole in the Dorsa Argentea Formation are tangles of ridges that resemble what is left from streams under glaciers. These are called eskers. In the same general area are shapes, now named Sisyphi Montes, that look like what is formed on Earth when volcanoes erupt under glaciers; they have steep walls and flat tops.<ref> Ghatan, G.J. and J.W. Head, III. 2002. Candidate subglacial volcanoes in the south polar region of Mars: morphology, morphometry, and eruption conditions. J. Geophys. Res., 107(E7), 5048. (10.1029/2001JE001519.)</ref> <ref> Ghatan, G.J., J.W. Head, III and S. Pratt. 2003. Cavi Angusti, Mars: characterization and assessment of possible formation mechanisms. J. Geophys. Res., 108(E5), 5045. (10.1029/2002JE001972.) </ref> <ref>Head, J., L. Wilson. 2007. Heat Transfer in Volcano-Ice Interactions on Mars: Synthesis of Environments and Implications for Processes and Landforms. Annals of Glaciology. 45</ref> These features are common in Iceland. Earlier studies support the idea that glaciers on Mars may have been much thicker and more extensive in the past. It appears in many places that LVF has dropped, probably because it has lost ice.<ref> Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Letters. Doi:10.1016/j.epsl.2009.08.031</ref> <ref> Levy, J., et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. Journal of Geophysical Research: 112, E08004</ref> <ref>Head, J., et al. 2006. Modification of the dichotomy boundary on Mars by Amazonian mi-latitude regional glaciation. Geophysical Research Letters: 33, L08S03</ref> <ref> Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36, 411-414.</ref>

[[File:R0502109dorsaargentea.jpg|thumb|300px|left|Possible eskers indicated by arrows. Eskers form under glaciers.]]

== References ==
{{reflist|colwidth=30em}}

==See also==

* [[High Resolution Imaging Science Experiment (HiRISE)]]

* [[InSight Mission]]
* [[Martian features that are signs of water ice ]]
* [[Periodic climate changes on Mars]]
* [[Tharsis]]
* [[Water]]

== External links ==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

*[https://www.youtube.com/watch?v=RYG-HLr33CM Jim Secosky - Martian Geology - 16th Annual International Mars Society Convention]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]
* [https://www.youtube.com/watch?v=m2ERsEXAq_s Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk[T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground
* High resolution [https://www.flickr.com/photos/seandoran/30604739258/ flyover video] by Seán Doran of a glacier in Protonilus Mensae, based on NASA [https://www.uahirise.org/ESP_018857_2225 digital terrain model]; see [https://www.flickr.com/photos/seandoran/albums/72157677941945560 album] for more
* [https://www.youtube.com/watch?v=j8P9pE8CYgI Glaciers on Mars?]

* [https://www.sciencedirect.com/science/article/pii/S0019103520305121#f0010 Gallagher. c. et al. In press 2020. Landforms indicative of regional warm based glaciation, Phlegra Montes, Mars. Icarus ]

[[Category: Geologic Processes]]

Rivers on Mars

2023-03-20T23:24:06Z

Suitupandshowup: /* External links */ added to list

{{Mars atlas}}
Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:PIA15090nirgalvallismariner9.jpg|thumb|226px|left|Nirgal Vallis, as seen by Mariner 9 This is one of the first images to show evidence of past water on Mars.]]

There is much evidence that water once flowed in river valleys on Mars. Images of curved and branched channels have been seen in images from Mars spacecraft dating back to the early seventies with the Mariner 9 orbiter. <ref> Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX </ref> <ref> Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> <ref> Carr, M. 1979. Formation of Martian flood features by release of water from confined aquifers. J. Geophys. Res. 84, 2995–300.</ref> <ref> Komar, P. 1979. Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth. Icarus 37, 156–181.</ref> <ref>http://advances.sciencemag.org/content/5/3/eaav7710</ref> <ref>Kite, E., et al. 2019. Persistence of intense, climate-driven runoff late in Mars history. Science Advances: 5, eaav7710</ref> These river valleys are called Vallis (plural Valles), the Latin word for valley.

==Outflow Channels==

[[File: Ravi_Vallis.jpg|thumb|226px|right|Water poured out of the ground here at Ravi Vallis and carved a channel.]]

Researchers have grouped Martian river valleys into two groups. One type, called outflow channels, carried as much as or more water any on Earth and maybe at any time in Earth’s history.<ref>https://www.uahirise.org/ESP_045833_1845</ref> Rushing water formed large streamlined islands. Vast quantities of water seem to have just burst out of the ground.<ref> Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref> <ref> Carr, M. (1979). "Formation of Martian flood features by release of water from confined aquifers". J. Geophys. Res., 84, 2995-3007.</ref> <ref>Clifford, S. M.; Parker, T. J. (2001). "The Evolution of the Martian Hydrosphere: Implications for the Fate of a Primordial Ocean and the Current State of the Northern Plains". Icarus. 154 (1): 40–79. Bibcode:2001Icar..154...40C. doi:10.1006/icar.2001.6671</ref> <ref> Andrews-Hanna, J., R. Phillips. 2007. Hydrological modeling of outflow channels and chaos regions on Mars. Journal of Geophysical Research: Planets Volume 112, Issue E8 </ref> <ref>Clifford, S. 1993. A model for the hydrologic and climatic behavior of water on Mars. JGR, 98, 10973L </ref> The water originated in areas of collapsed terrain where the ground ended up formed into mesas and large blocks. This collapsed terrain has been called chaos.<ref> Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> The water is thought to have flowed to lower elevations and created an ocean to the north that may have been one third the area of Mars.<ref>https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref> Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> Some researches postulated that floods erupted from the ground many times.<ref>Coleman, N and C. Coughenour. 2021. CONSIDERATION OF STREAM POWER AND THE OUTFLOW CHANNELS OF MARS. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 1010.pdf</ref> <ref> Coleman N. (2010) LPSC 41, Abs. #1174, Kasei cataracts, https://www.lpi.usra.edu/meetings/lpsc2010/pdf/1174.pdf.</ref> Since Mars is very cold, ice would have quickly formed on the top and allowed the water to move along for some time. Scientists generally agree that Mars has a thick shell of ice under the surface.<ref>Clifford, S. 1993. A model for the hydrologic and climatic behavior of water on Mars. Geophys. Res. 98 (E6)</ref> Perhaps in the past there was a vast interconnected layer of water under it. If an asteroid, fault, or volcanic eruption caused the ice to break, water could pour out. <ref>Carr, M. 1979. Formation of martian flood features by release of water from confined aquifers. J. Geophys. Res. 84: 2995-3007.</ref> <ref>ISBN 978-0-521-87501-0 Please check ISBN|reason=Check digit (0) does not correspond to calculated figure.</ref> <ref>Hanna, J. and R. Phillips. 2005. Tectonic pressurization of aquifers in the formation of Mangala and Athabasca Valles on Mars. LPSC XXXVI. Abstract 2261.</ref>

<gallery class="center" widths="380px" heights="360px">

File:Kasei Valles topolabled.JPG|Labeled topo map of Kasei Valles and many other outflow channels These channels supplied water to a vast Martian Ocean.
File:USGS-Mars-MC-11-OxiaPalusRegion-mola.png|Labeled topo map of outflow channels in the Oxia Palus region

File:Viking Teardrop Islands.jpg|Teardrop-shaped islands formed from water.
File:Detail of Maja Valles Flow.jpg|Maja Valles, an outflow channel, shaped land around Dromore crater.
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel These were shaped by running water.
</gallery>

==Valley Networks==

Another type of channel exists mostly in the old, southern highlands. They were discovered by Mariner 9 in 1971. Sometimes called valley networks, these channels closely resemble streams in drainage basins on the Earth. The channels are branched (dendritic). However, branches are typically shorter on Mars than on the Earth. <ref> Baker, V. , and J. Partridge. 1986. Small Martian valleys: Pristine and degraded morphology, J. Geophys. Res., 91, 3561–3572.</ref> Also, most channels do not exhibit a high branching density. But, in some places the stream branches are, in fact, as dense as some on Earth.<ref> Hynek, B.M., and Phillips, R. 2001. Evidence of extensive denudation of the martian highlands, Geology, 29, 407-10</ref> Many look as if they were made with precipitation. Further support for abundant water flow, came from a research team that developed a computer program to look for valleys made by streams found that the stream networks were much longer than previous thought (2.3 times longer) and that they were much denser. Valleys were especially dense in northern Terra Cimmeria and the Margaritifer Terra. There results suggest that precipitation may have caused them.<ref>https://www.astrobio.net/mars/martian-north-once-covered-by-ocean/</ref> <ref>Luo, W., T. Stepinski. 2009. Computer‐generated global map of valley networks on Mars. Journal of Geophysical Research: Planets: 114, Issue E11. https://doi.org/10.1029/2009JE003357.</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009JE003357</ref>

<gallery class="center" widths="380px" heights="360px">
File:Branched Channels from Viking.jpg|These branched channels, as seen by Viking look like they were caused by rainfall.
WikiESP 033729 1410stream.jpg|Small branched channel
File:ESP 056561 2170channels.jpg|Branched channel, as seen by HiRISE under HiWish Program
File:ESP 056820 1505channelnetwork.jpg|Channel network
</gallery>

Channels displaying curves, wide meanders, oxbow lakes, and wide meanders are similar to those on Earth. Many channels end in low areas such as craters. At times, deltas form where the stream enters a crater; they look like a stream entering a lake. Some small streams are found on valley floors. Stream channels on valley floors imply more than one episode of flow.<ref> Malin, M.C., and Carr, M.H. (1999), Groundwater formation of martian valleys, Nature, 397, 589-592</ref> <ref> Jaumann, R. (2005), Martian valley networks and associated fluvial features as seen by the Mars Express High Resolution Camera (HRSC), LPSC XXXVI, Abstract 1815</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 048011 1830channel.jpg|Small channel on floor of a valley suggest water flowed more than once here.
File:13882282 10207143921535802 7740003704272946655 nchannelinvalley.jpg|Channel on floor of a valley Water may have carved large valley early on; later the small channel was made.
File:ESP 056800 1385channels.jpg|Channels carried water in and out of craters.
File:26126contextb22 018333 1548delta.jpg|Delta on Holden Crater floor, as seen by CTX
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.
</gallery>

<gallery class="center" widths="380px" heights="360px">
File:34189 1740cutoff.jpg|Cutoff from a meander. This type of formations takes a long time to form.
</gallery>

Even though some channels go for relative short distances, some may run for hundreds or thousands of kilometers. One long system of lakes and rivers may reach from the far south to the far north. <ref> Cabrol, N., E. Grin. 1999. Distribution, classification, and ages of martian impact crater lakes. Icarus: 142, 160-172.</ref> <ref> Irwin, R.; et al. (2005). "An intense terminal epoch of widespread fluvial activity on early Mars. 2. Increased runoff and paleolake development". J. Geophys. Res. 110.</ref> <ref> Fassett, C.; Head, J. (2008). "Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology". Icarus. 198: 37–56.</ref> In a study released in 2018, researchers found 34 palelakes and associated channels in the northeastern Hellas Basin. Because some were close to the Hadriacus volcano, some channels may have been created by hydrothermal systems; thereby allowing ice to melt. A number look as if they were formed from precipitation, others from groundwater.<ref>https://www.liebertpub.com/doi/abs/10.1089/ast.2018.1816?journalCode=ast</ref> <ref>https://www.seti.org/groundwater-and-precipitation-provided-water-form-lakes-along-northern-rim-hellas-basin-throughout</ref> <ref>Hargitai, H., et al. 2018. Groundwater-Fed, and Fluvial Lakes in the Navua–Hadriacus–Ausonia Region, Mars. Astrobiology: 18. (11). https://doi.org/10.1089/ast.2018.1816</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 056917 2170channels.jpg|Curved and branched channels
</gallery>

==Was Mars too cold for running water?==

It seems that these valley networks happened in the past when Mars was much warmer and wetter. But, climate models all say that Mars was always too cold to have much liquid water. The sun is too far away. It likely did not give off as much light energy in the past.<ref>Wordsworth, R., et al. 2015. Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model. Journal of Geophysical Research: Planets Volume 120, Issue 6. https://doi.org/10.1002/2015JE004787.</ref> <ref>Squyres, S., J. Kasting. 1994. Early Mars: How Warm and How Wet? Science : Vol. 265, Issue 5173, pp. 744-749.</ref> <ref>Catling, D. C. (2007). Mars: Ancient fingerprints in the clay. Nature. 448 (7149): 31–32. </ref> Another factor that could still have made the climate warmer is that the atmosphere may have been much thicker in the past and could have contained greenhouse gases like carbon dioxide. However, if this were the case, carbon dioxide would have ended up in large deposits of carbonate rocks such as limestone.<ref>http://www.psrd.hawaii.edu/Oct03/carbonatesMars.html</ref> Despite looking with instruments designed to detect carbonates, scientists have found very little. <ref> Murchie, S., et al. 2009. A synthesis of Martian aqueous mineralogy after 1 Mars years of observations from the Mars Reconnaissance Orbiter. Journal of Geophysical Research: 114, E00D06</ref> They do exist in tiny areas, have been found in meteorites that came from Mars, and have been found by landers, but there just does not seem to be enough to say that Mars once had a thick carbon dioxide atmosphere. <ref> McKay, C., et al. 1996. Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001. Science: 273, 924-930</ref> <ref>https://www.webelements.com/nexus/carbonate-minerals-on-mars/</ref> <ref> https://mars.nasa.gov/mer/newsroom/pressreleases/20040109a.html</ref> <ref>Pollack, J. B, Roush, T., Witteborn, F., Bregman, J., Wooden, D., Stoker, C., Toon, O. B., Rank, D., Dalton, B., and Freedman, R. (1990) Thermal emission spectra of Mars (5.4-10.5 microns): evidence for sulfates, carbonates, and hydrates, Journal of Geophysical Research, v. 95 (B9), p. 14595-14627.</ref> <ref> https://mars.nasa.gov/resources/4040/carbonate-containing-martian-rocks/</ref> Some researchers have proposed that other greenhouse gases may have been involved.<ref> Ramirez, R. M., Kopparapu, R., Zugger, M. E., Robinson, T. D., Freedman, R., & Kasting, J. F. 2014. Warming early Mars with CO2 and H2. Nature Geoscience, 7(1), 59-63.</ref> <ref> Wordsworth, R., Kalugina, Y., Lokshtanov, S., Vigasin, A., Ehlmann, B., Head, J., ... & Wang, H. 2017. Transient reducing greenhouse warming on early Mars. Geophysical Research Letters, 44(2), 665-671.</ref>
So we are left with what appears to be certain proof that Mars had great amounts of liquid water—somehow channels were made. On the other hand, we do not know how the climate could have ever supported very much liquid water.<ref> Haberle, R.M. 1998. Early Climate Models, J. Geophys. Res., 103(E12), 28467-79.</ref> Nevertheless, scientists have suggested many ways for channels to be created. We must keep in mind that the planet does not have to that warmed to 32 degrees F for running water to exist because water on Mars would likely contain dissolved minerals that would lower its freezing point.<ref>Fairen, A., et al. 2009. Stability against freezing of aqueous solutions on early Mars. Nature: 459, 401-404</ref> Also, water may have collected in vast aquifers under the ground and released at different times by things such as heating from magma moving underground or by impacts of asteroids. After large impacts, the nearby area might be warm enough, long enough for water to erode channels.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/2024.pdf</ref> <ref>Palumbo, A., J. Head. OCEANS ON MARS: THE POSSIBILITY OF A NOACHIAN GROUNDWATER-FED OCEAN IN A SUBFREEZING MARTIAN CLIMATE. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 2024.pdf</ref> <ref> Newsome, H.E. (1980), Hydrothermal alteration of impact melt sheets with implications for Mars, Icarus, 44, 207-16.</ref> <ref>Mangold, N., V. Ansan, P. Masson, C. Quantin, and G. Neukum. 2008. Geomorphic study of fluvial landforms on the northern Valles Marinerisplateau, Mars, J. Geophys. Res., 113, E08009, doi:10.1029/2007JE002985.</ref> <ref>Segura, T. L., O. B. Toon, and T. Colaprete. 2008. Modeling the environmentaleffects of moderate‐sized impacts on Mars, J. Geophys. Res., 113,E11007, doi:10.1029/2008JE003147</ref> <ref> Segura, T. L., O. B. Toon, T. Colaprete, and K. Zahnle. 2002. Environmental Effects of Large Impacts on Mars, Science, 298, 1977–1980. doi:10.1126/science.1073586</ref> <ref>Kraal, E. R., M. van Dijk, G. Postma, and M. G. Kleinhans 2008b. Martian stepped‐delta formation by rapid water release, Nature, 451. 973–976, doi:10.1038/nature06615</ref> <ref>Toon, O. B., T. Segura, and K. Zahnle. 2010. The formation of Martian river valleys by impacts, Annu. Rev. Earth Planet. Sci., 38, 303–322. doi:10.1146/annurev-earth-040809-152354</ref> It has even been suggested that the weather after a big impact may be changed enough to generate rainfall.<ref>https://arxiv.org/abs/1902.07666</ref> <ref>Turbet, M., et al. 2019. The environmental effects of very large bolide impacts on early Mars explored with a hierarchy of numerical models. Submitted to Icarus</ref> <ref>https://www.space.com/mars-water-from-massive-impacts.html?utm_source=sdc-newsletter&utm_medium=email&utm_campaign=20190305-sdc</ref> Some researchers think that streams may have existed under thick ice sheets. <ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/2574.pdf</ref> <ref>Galofre, G., et al. 2019. DID MARTIAN VALLEY NETWORKS FORM UNDER ANCIENT ICE SHEETS? 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 2574.pdf</ref> <ref> Squyres, S.W., and Kasting, J.F. 1994. Early Mars: How warm and how wet?, Science, 265, 744-8.</ref> <ref>https://www.iflscience.com/space/massive-ice-sheets-not-rivers-may-have-carved-ancient-valleys-on-mars/</ref> <ref> https://www.nature.com/articles/s41561-020-0618-x</ref> <ref>Galofre, A. et al. 2020. Valley formation on early Mars by subglacial and fluvial erosion. Nature Geoscience. </ref> As of today, we just do not have a definite answer.

==References==

{{reflist|colwidth=30em}}

==See Also==

*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[How living on Mars will be different than living on Earth]]
*[[Martian features that are signs of water ice]]
*[[Oceans on Mars]]

*[[Sublimation]]
*[[Water]]

== External links ==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

*[https://www.youtube.com/watch?v=9BthpvATURA What caused the rivers on Mars: Climate change or impacts?]

*[https://www.youtube.com/watch?v=6A8MHpPhcuw Mars: Ancient Rivers]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]

* [https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

*[https://www.youtube.com/watch?v=EJk0hS4_gz4 Water on Mars and the Potential for Martian Life]

* [https://www.youtube.com/watch?v=GX9XzRyuYLc Oceans and Life on Mars]

[[Category: Geologic Processes]]

Oceans on Mars

2023-03-20T23:22:58Z

Suitupandshowup: /* External links */ added to list

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:Marsoceanimage.jpg|600pxr| Drawing showing the extent of ocean on Mars]]

Today, much evidence supports at least one ocean in the past on Mars.<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872529/</ref> <ref> Carr, M. & J. Head. 2010 Geologic history of Mars. Earth and Planetary Science Letters. 294. 185-203.</ref> <ref>Clifford, S. M.; Parker, T. J. (2001). "The Evolution of the Martian Hydrosphere: Implications for the Fate of a Primordial Ocean and the Current State of the Northern Plains". Icarus. 154 (1): 40–79. Bibcode:2001Icar..154...40C. doi:10.1006/icar.2001.6671</ref> <ref> Baker, V. R.; Strom, R. G.; Gulick, V. C.; Kargel, J. S.; Komatsu, G.; Kale, V. S. (1991). "Ancient oceans, ice sheets and the hydrological cycle on Mars". Nature. 352 (6336): 589–594. Bibcode:1991Natur.352..589B. doi:10.1038/352589a0. </ref> <ref>Lucchitta, B. et al. 1986. Sedimentary deposits in the northern lowland plains, Mars. Proc. Lunar planet. Conf. 17th, part 1, j. Geophys. Res., 91, suppl., E166-E174.</ref> Support for the idea of Martian oceans was boosted when it was concluded that Mars has lost most of its atmosphere (and water).<ref>Villanueva G. L., Mumma M. J., Novak R. E., Käufl H. U., Hartogh P., Encrenaz T., Tokunaga A., Khayat A., and Smith M. D., Science, Published online 5 March 2015 [DOI:10.1126/science.aaa3630]</ref> <ref> Villanueva, G., et al. 2015. Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs. Science 10 Apr 2015: Vol. 348, Issue 6231, pp. 218-221. </ref> <ref> https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space </ref> <ref> B.M. Jakosky et al. 2017. Mars’ atmospheric history derived from upper-atmosphere measurements of 38Ar/36Ar. Science 355 (6332): 1408-1410; doi: 10.1126/science.aai7721 </ref> <ref> http://www.sci-news.com/space/maven-martian-atmosphere-lost-space-04750.html</ref> In addition, researchers in 2015 published a paper detailing two tsunamis that happened when asteroids struck a Martian ocean that existed at the time. <ref> http://astrobiology.com/2016/05/ancient-tsunami-evidence-on-mars-reveals-life-potential.html </ref> <ref>Rodriguez, J.; et al. 2016. "Tsunami waves extensively resurfaced the shorelines of an early Martian ocean. :" (PDF). Scientific Reports / 47th Lunar and Planetary Science Conference. 6: 25106. Bibcode:2016NatSR...625106R. doi:10.1038/srep25106. PMC 4872529 Freely accessible. PMID 27196957.version at Nature </ref> Most of the rest of this article will cover the long history of how evidence built up for one or more oceans on Mars. Nevertheless, it must be said that although there are decades of accumulated evidence for a Martian ocean, the idea remains controversial. <ref>Head, J., et al. 2018. TWO OCEANS ON MARS?: HISTORY, PROBLEMS AND PROSPECTS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2194.pdf</ref>

==Appearance==

When Mariner 9 pictures arrived in 1969, pictures revealed outflow channels that could carry water into the northern lowlands.<ref> Carr,M. 1996. Water on Mars. Oxford</ref> These lowlands, called Vastitas Borealis, were smooth and level, as if they were formed under an ocean. Moreover, the age of Vastitas Borealis and the channels were found to be similar.<ref>Head, J., et al. 2002. Northern lowlands of Mars: Evidence for widespread volcanic flooding and tectonic deformation in the Hesperian Period. J. Geophys. Res. 107(E1), 5003.</ref> Hence, it was logical to assume that huge outflow channels supplied water to form an ocean covering one third of the planet. The ground was smooth because it was an ocean floor.

<gallery class="center" widths="380px" heights="360px">
File:Kasei Valles topolabled.JPG|Labeled topo map of Kasei Valles and many other outflow channels that supplied water to a Mars Ocean

File:USGS-Mars-MC-11-OxiaPalusRegion-mola.png|Labeled topo map of outflow channels in the Oxia Palus region

File:Mgs orbiter.jpg|Mars Global Surveyor Its instrument, called MOLA, while measuring topography revealed a deep, smooth basin that could have contained an ocean.

Mars_MGS_colorhillshade_mola_1024.jpg|MOLA map of Mars The blue area in the north (top of image) is low and smooth as if it were under an ocean.

</gallery>

Further study by researchers seemed to show features common to shorelines on Earth.<ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M. 1989. Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> Still, other explanations for these features were advanced when higher resolution photos from Mars Global Surveyor (5-10 times better than Viking) were examined. Some could be identified as volcanic in origin. <ref>Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> Also, many shoreline features were located at vastly different altitudes according to MOLA measurements from the Mars Global spacecraft, when in theory all should be of the same level. However, large sections of the shorelines did line up to be nearly on a level line on one of the two shorelines that were previously been proposed .<ref>Head et al. 1999. Possible Ancient Oceans on Mars: Evidence from Mars Orbiter Laser Altimeter Data. Science: 286, 2134.</ref> <ref>Malin, M. C., and Edgett, K. S. 1999. "Oceans or Seas in the Martian Northern Lowlands: High Resolution Imaging Tests of Proposed Coastlines". Geophys. Res. Lett. 26 (19): 3049–3052. Bibcode:1999GeoRL..26.3049M. doi:10.1029/1999GL002342.</ref>

[[File:Mars rampart crater.jpg|left|thumb|320px| Yuty Crater showing lobe and rampart morphology; it looks like mud was formed during the impact.]]

As researchers examined more and more data from orbiting spacecraft more hints that an ocean had existed become evident. The deepest parts of the supposed ocean basins displayed polygonal ground which could be formed from abundant water.<ref>Parker, T., et al. 1989. Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary . Icarus. 82111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> Furthermore, craters that would have been under the ocean had a different appearance. They looked like projectiles had landed in mud. Scientists described the shapes as having a “lobe and rampart morphology.” In these places, the ground may have been full of water and/or ice that could have been left by a previous ocean. <ref> Carr, M. , et al. 1977. Martian permafrost features. Journal of Geophysical Research. 82. 195. </ref> When a detailed analysis was performed, it was found that the deeper basins showed that lobe and rampart shapes appeared in smaller craters than in other regions. Consequently, the team concluded that the ice was shallower in the deeper basins. <ref>Kuzmin, R., et al. 1988. Structure inhomogeneities of the Martian cryosphere, Solar System Res. 22. 195-212. </ref> Many of the major channels that drained into the northern lowlands stopped at about the same elevation; just as if they were at the edge of a large body of water.<ref>Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134</ref> <ref> Carr,M. 1996. Water on Mars. Oxford</ref> Similarly, with access to high resolution photos from HiRISE, a 2010 study of deltas revealed that over a dozen stop at the shoreline of the possible ocean.<ref>cite journal | last1 = DiAchille | first1 = G | last2 = Hynek | first2 = B. | year = 2010 | title = Ancient ocean on Mars supported by global distribution of deltas and valleys. nat | url = | journal = Geosci | volume = 3 | issue = 7| pages = 459–463 | doi = 10.1038/ngeo891 | bibcode=2010NatGe...3..459D</ref> Initial observations showed deltas at near the same level and that can be explained if they were at the edge of an ocean.<ref>cite journal | last1 = DiBiasse | first1 = | last2 = Limaye | first2 = A. | last3 = Scheingross | first3 = J. | last4 = Fischer | first4 = W. | last5 = Lamb | first5 = M. | year = 2013 | title = Deltic deposits at Aeolis Dorsa: Sedimentary evidence for a standing body of water on the northern plains of Mars | url = | journal = Journal of Geophysical Research: Planets | volume = 118 | issue = | pages = 1285–1302</ref> <ref>Fawdon, P., et al. 2018. HYPANIS VALLES DELTA: THE LAST HIGH-STAND OF A SEA ON EARLY MARS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2839.pdf</ref> However, later studies showed that many of the deltas were in clusters as if they were in depressions like craters. If they were lined up along the proposed edge of ocean, it would be strong evidence for an ocean.<ref> Rivera-Hernbardez, F. 2019, From Grains to Landscapes: Reconstructing Martian Environments at Multiple Scales. From talk given to Schoumberger</ref>

== Theoretical and computational considerations==

===Was there enough water===

The northern lowlands, where the ocean was, appear to be covered by a material that has been called the Vastitas Borealis Formation. Many craters here were called "stealth" craters because they looked like they were hidden under some sort of covering--like a deposit on an ocean floor.<ref>Kreslavsky, M., J. Head. 2002. Fate of outflow channel effluents in the northern lowlands of Mars: The Vastitas Borealis Formation as a sublimation residue from frozen ponded bodies of water. Journal of Geophysical Research: 107, 5121</ref> This formation may represent the eroded materials from the outflow channels. Evidence for this relationship is that the volume of the Vastitas Borealis Formation is almost the same as the volume of the eroded material from the channels.<ref>Carr, M., et al. 1987. Volumes of channels, canyons, and chaos in the circum-Chryse region of mars. Lunar Planet. Sci. XVIII. 155-156</ref>
In addition, more water was required to develop valley networks, outflow channels, and delta deposits of Mars than was in a Martian ocean, according to research reported in 2017. This implies that there was plenty of water for an ocean.<ref>cite journal | url=https://www.hou.usra.edu/meetings/lpsc2017/pdf/1734.pdf | title=New Martian valley network volume estimate consistent with ancient ocean and warm and wet climate | author=Luo, W., et al. | journal=Lunar And Planetary Science | year=2017 | volume=XLVIII | pages=15766 | doi=10.1038/ncomms15766 | pmid=28580943 |pmc=5465386| bibcode=2017NatCo...815766L </ref>
In 2009 a team of researchers tried to find out exactly how many stream channels existed on Mars. They developed a computer program that examined topographical data. The program looked for U-shaped structures, since that would be the shape of channels carved by water. They found many more channels, and in some areas the valley density was similar to what is found on the Earth. Such a high density of channels supports rain on the planet. A large ocean may have been needed to provide enough moisture for rain. A northern ocean would explain the way that certain channels are distributed around the planet. For example, valleys tend to get shallower in the south, perhaps because they are farther from the ocean. Also, there seems to be a southern limit for valleys where less water could be carried from a northern ocean.<ref>cite news | author = Staff | title = Martian North Once Covered by Ocean | date = 26 November 2009 | url = http://www.astrobio.net/pressrelease/3322/martian-north-once-covered-by-ocean | work = Astrobiology Magazine | accessdate = 19 February 2014</ref> <ref>cite news | author = Staff | title = New Map Bolsters Case for Ancient Ocean on Mars | date = 23 November 2009 | url = http://www.space.com/7584-map-bolsters-case-ancient-ocean-mars.html | work = Space.com | accessdate = 2014-02-19</ref>

===Size of ocean===

Different researchers have come up with different sizes for an ancient ocean on Mars. However, many of these estimates are reasonable in that the ocean volume is similar to the volume of water needed to carve the many channels on Mars. In fact, it is even less than the maximum amount that the ground could hold.<ref>Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134</ref> <ref> Carr,M. 1996. Water on Mars. Oxford</ref> So, the ground could contain all of the water that was in the ocean. There is a division of opinion as to the area of the ocean. Early on two different shorelines were proposed.<ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> The shoreline for the smaller ocean is more plausible since there are far less elevation differences along the shoreline.<ref>Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> One early estimate of the ocean volume was 19,000,000 Km cubed (1.9 X 107). This volume is equal to 130 meters of water covering the entire planet.(Global Equivalent level-GEL). Estimates would be 23,000,000 Km cubed (2.3 X 107) equal to 156 meters GEL for the high end for the ocean’s size. This larger number represents the ocean’s if we take of total size of the Vastitas Borealis Formation as the area for the ocean.<ref>Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref>

===What was the source of the water===

Many have wondered where did the water come from? Today Mars is cold and dry—very dry. Many believe that the atmosphere was once much thicker with a great deal of carbon dioxide that would have caused a global warming. But, models of long term climate change indicate that Mars may have always been cold and dry. <ref> Forget et al. 2013. 3D modelling of the early martian climate under a denser CO2 atmosphere: Temperatures and CO2 ice clouds. Icarus 222, 81-99.</ref> <ref> Wordsworth et al. 2013. Global modelling of the early martian climate under a denser CO atmosphere: Water cycle and ice evolution. Icarus 222, 1-19.</ref> One major consideration is that the early sun was not as strong. Perhaps, the average temperature was never above freezing. If that was the case, then the many channels on Mars may have formed during relatively short term, localized events like impacts or volcanic activity.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/2024.pdf</ref> <ref>Palumbo, A., J. Head. 2019. OCEANS ON MARS: THE POSSIBILITY OF A NOACHIAN GROUNDWATER-FED OCEAN IN A SUBFREEZING MARTIAN CLIMATE. A. SUB- FREEZING MARTIAN CLIMATE. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132) 2024.pdf</ref> <ref>Head, J., et al. 2017. DECIPHERING THE NOACHIAN GEOLOGICAL AND CLIMATE HISTORY OF MARS: A STRATIGRAPHIC, GEOLOGIC PROCESS AND MINERALOGICAL PERSPECTIVE – PART 1: CURRENT KNOWNS AND UNKNOWNS. 4th Early Mars, 3046/3047.</ref> <ref> Head, J. et al. 2017. DECIPHERING THE NOACHIAN GEOLOGICAL AND CLIMATE HISTORY OF MARS: PART 2 – A NOACHIAN STRATIGRAPHIC VIEW OF MAJOR GEOLOGIC PROCESSES AND THEIR CLIMATIC CONSEQUENCES. 4th Early Mars, 3047</ref>
Today, we generally accept ideas that were put forth in a long paper by Steven Clifford in which he proposed that a thick layer of ice, called a cryosphere, circled the entire planet. This frozen cryosphere is estimated to contain hundreds meters of GEL.<ref> Clifford, S. 1993. A model for the hydrologic and climatic behavior of water on Mars. Geophys. Res. 98 (E6)</ref> As the planet cooled, water in the ground froze to the bottom of this ice layer, creating an aquifer under great pressure. Then the water in the aquifer was suddenly released, perhaps after an asteroid impact cracked the cryosphere. Huge, catastrophic floods came out of chaos regions and carved great outflow channels that carried the water to a northern ocean. <ref>Clifford, S. M.; Parker, T. J. (2001). "The Evolution of the Martian Hydrosphere: Implications for the Fate of a Primordial Ocean and the Current State of the Northern Plains". Icarus. 154 (1): 40–79. Bibcode:2001Icar..154...40C. doi:10.1006/icar.2001.6671</ref> <ref> Gulick, V., D. Tyler, C. McKay, and R. Haberle. 1997. Episodic ocean‐induced CO2 greenhouse on Mars: Implications for fluvial valley formation. Icarus: 130, 68–86.</ref> <ref> Andrews-Hanna, J., R. Phillips. 2007. Hydrological modeling of outflow channels and chaos regions on Mars. Journal of Geophysical Research: Planets Volume 112, Issue E8</ref> <ref> Clifford, S. 1993. A model for the hydrologic and climatic behavior of water on Mars. JGR, 98, 10973L</ref>

Evidence for a past aquifer at depth on Mars came out in February 2019, from a group of European scientists who published geological evidence of an ancient planet-wide groundwater system that was probably connected to a Martian ocean.<ref name="ESA-20190228">ESA Staff |title=First Evidence of "Planet-Wide Groundwater System" on Mars Found |url=https://www.esa.int/Our_Activities/Space_Science/Mars_Express/First_evidence_of_planet-wide_groundwater_system_on_Mars |date=28 February 2019 |work=[[European Space Agency]]</ref> <ref name="FTR-20190228">Houser |first=Kristin |title=First Evidence of "Planet-Wide Groundwater System" on Mars Found |url=https://futurism.com/the-byte/mars-groundwater-system-planet-wide |date=28 February 2019 |work=Futurism.com</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018JE005802</ref> <ref> https://www.leonarddavid.com/planet%E2%80%90wide-groundwater-system-on-mars-new-geological-evidence/</ref> The study was of 24 craters that did not display an inlet or outlet; hence, water for the lake must have come from the ground. All craters were located in the northern hemisphere of Mars. These craters had floors lying roughly 4000 m below Martian 'sea level' (a level that, given the planet's lack of seas, is defined based on elevation and atmospheric pressure). Features on the floors of these craters could only have formed in the presence of water.<ref>Salese, F., et al. 2019. A GEOLOGICAL MODEL FOR MARTIAN GROUNDWATER BASED ON WATER-FORMED
FEATURES WITHIN DEEP BASINS. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3240.pdf</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/3240.pdf</ref> There are multiple features showing that the water level in the craters rose and fell over time. Deltas and terraces were present in many craters.<ref>http://astrobiology.com/2019/02/first-evidence-of-a-planet-wide-groundwater-system-on-mars.html</ref> Some crater floors contain minerals such as various clays and light-toned minerals that form in water. In addition, layers are found in some of these craters, and layers often form under water. Taken together, these observations strongly suggest that water was present in these places.<ref>https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018JE005802</ref> Some of the craters studied were Pettit, Sagan, Nicholson, Mclaughlin, du Martheray, Tombaugh, Mojave, Curie, Oyama, and Wahoo. It seems that if a crater was deep enough, water came out of the ground and produced a lake.<ref>https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018JE005802</ref> Water may have came out of the ground to contribute water to an ocean in the low-lying North.

<gallery class="center" widths="380px" heights="360px">

File:J03 045825 2081sappingcraterarrowslabeled.jpg|Crater showing valleys that formed from sapping--that is the water flowed out of the ground. Eventually, the water formed a lake.

File:J03 045825 2081sappingcraterdelta.jpg|Red arrows show deltas that formed from water that issued from the ground in sapping valleys. This is evidence that water came out of the ground and made a lake.

</gallery>

===Where did the water go===

Another consideration that needs to be explained is where did all the water go? At first the water would freeze. Then, in the thin, cold atmosphere of Mars, the ice would have slowly sublimated--that is turned directly into a gas. This water in the vapor state would have migrated to the poles, and then the base of the ice caps would melt with the liquid water freezing to the cryosphere. However, if dust covered the ice the ice may have been lasted for a very long time.<ref> Clifford, S., T. Parker, 2001. The evolution of the Martian hydrosphere: implications for the fate of a primordial ocean and the current state of the Northern Plains. Icarus 154, 40</ref>
The biggest present supply of water is the ice caps, also called the layered polar deposits. Scientists have said that they account for only 25 meter Global Equivalent level (GEL). More recent estimates are 17-22 meters of GEL.<ref>Lasue, J., et al. 2013. Quantitative Assessments of the Martian Hydrosphere. Space Sci. Rev. 174, 155-212.</ref> <ref> Carr, M., J. Head. 2015. Martian surface/near-surface water inventory: Sources, sinks, and changes with time. Geophys. Res. Lett. 42, 726-732.</ref> However, it could be less, as radar studies from orbit have measured the larger cap, the northern one, as having only 821,000 Km cubed which is less than 6 meters GEL. <ref>https://www.space.com/17048-water-on-mars.html </ref> <ref> Radar Map of Buried Mars Layers Matches Climate Cycles". Jet Propulsion Lab. 2009-09-22</ref> Remember, the ocean may have held more than 100 meters of GEL.

[[File:Mars NPArea-PIA00161.jpg |left|thumb|320px| The North Polar layered deposits are the largest reservoir of water . They contain enough water to cover Mars to a depth of 6-25 meters.]]

Some water is frozen in the ground and in glaciers. A team of researchers led by Jeremie Mauginot reasoned that there was 7 meters GEL in the ground between the polar deposits and 50 degrees latitude. <ref> Mauginot , J., et al. 2010. The 3-5 MHz-global ref map of Mars by MARSIS/Mars Express: implications for the current inventory of subsurface H2O. Icarus: 210, 612-625.</ref> In addition, a study, published in 2017, found evidence for ice sheets down to 38 degrees latitude in Utopia and Arcadia Planitiae.<ref> Bramson, A., et al. 2017. Preservation of mid-latitude ice-sheets on Mars. J. Geophys. Res. 122, 2250-2260.</ref> Glaciers that are covered with debris and pedestal craters can account for another 2.6 meters GEL in the 30-50 degree bands according to Joseph Levy and his team that were published in Icarus.<ref> Levey, J., et al. 2010. Concentric crater fill in the northern mid-latitudes of Mars: Formation. Icarus: 209, 390-404.</ref>

[[File:ESP 018857 2225alpineglacier.jpg |right|thumb|320px| Glacier moving down a valley Picture taken with HiRISE under HiWish program. ]]

The abundance of water in the upper surface of the ground was mapped by the gamma ray and neutron spectrometers from the orbiting Mars Odyssey.<ref>https://mars.nasa.gov/odyssey/mission/overview/</ref> <ref> Mitrofanov, I., Anfimov, D., Kozyrev, A., Litvak, M., Sanin, A., Tret'yakov, V., ... Saunders, R. S. (2002). Maps of subsurface hydrogen from the High Energy Neutron Detector, Mars Odyssey. Science, 297(5578), 78-81. DOI: 10.1126/science.1073616</ref> <ref> Wilson, J. et al. 2018. Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data. Icarus 299: 148-160; doi: 10.1016/j.icarus.2017.07.028</ref>

<gallery class="center" widths="380px" heights="360px">
File:Mars Odyssey spacecraft model.png|Mars Odyssey found water-ice in the ground on Mars.
</gallery>

It found much water ice just beneath the surface, just as predicted by mathematical models. In fact, ice was actually seen when the landing rockets of the Phoenix lander blow away a dust cover to reveal ice.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> Powerful cameras have showed features that resemble glaciers on the Earth. Radar on satellites found ice just beneath the surface around mesas in features that were named lobate debris aprons (LDA). <ref>Holt, J. W.; Safaeinili, A.; Plaut, J. J.; Young, D. A.; Head, J. W.; Phillips, R. J.; Campbell, B. A.; Carter, L. M.; Gim, Y.; Seu, R.; Team, Sharad (2008). "Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars" (PDF). Lunar and Planetary Science. XXXIX: 2441. </ref> Measurements with MARSIS/Mars Express of something called a dielectric constant indicates that much ice is contained in the material that was under the ocean.<ref>Mouginot, J., et al. 2012. Dielectric map of the Martian northern hemisphere and the nature of plain filling materials. GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L02202, doi:10.1029/2011GL050286, 2012</ref> <ref>Holt, J. W.; Safaeinili, A.; Plaut, J. J.; Young, D. A.; Head, J. W.; Phillips, R. J.; Campbell, B. A.; Carter, L. M.; Gim, Y.; Seu, R.; Team, Sharad (2008). "Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars" (PDF). Lunar and Planetary Science. XXXIX: 2441.</ref> All these observations support the notion that there is a great deal of water frozen under the Martian surface.<ref>https://www.jpl.nasa.gov/news/new-study-challenges-long-held-theory-of-fate-of-mars-water?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20210316-2</ref> <ref>E. L. Scheller, B. L. Ehlmann, Renyu Hu, D. J. Adams, Y. L. Yung. Long-term drying of Mars by sequestration of ocean-scale volumes of water in the crust. Science, 2021; eabc7717 DOI: 10.1126/science.abc7717</ref> <ref>https://www.sciencedaily.com/releases/2021/03/210316132106.htm</ref>

<gallery class="center" widths="380px" heights="360px">

File:PIA10741 Possible Ice Below Phoenix.jpg|Smooth areas under Phoenix may be top of an ice layer.
File:800px-Wideviewlda42n18e.jpg|Labeled picture showing mesa surrounded by lobate debris aprons which radar has shown contain water-ice under a thin debris covering
</gallery>

It was believed that Mars may have been much warmer in the past due to a thick carbon dioxide atmosphere that would have through a global warming effect raised the temperature above the freezing point of water. If that was so, where did all the Carbon dioxide go? Chemically it should have been deposited as carbonates and formed limestone type rocks. Despite searches with instruments aboard satellites, very little carbonates have been found. <ref>Bandfield, J. , et al. 2000. A global view of Martian surface composition from MGS-TES. Science: 287, 1626-1630.</ref> <ref>Christensen, P., et al. 2001. Mars Global Surveyor Thermal Emission Spectrometer experiment: Investigation description and surface science results. J. Geosphy. Res. 106, 23823-23871</ref> On the other hand, there is strong evidence of acid conditions which would prevent carbonates from forming.<ref> Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM</ref> <ref> Catling, D. (1999-07-25). "A chemical model for evaporites on early Mars: Possible sedimentary tracers of the early climate and implications for exploration" (PDF). Journal of Geophysical Research. 104 (E7): 16453–16469. Bibcode:1999JGR...10416453C. doi:10.1029/1998JE001020</ref> <ref> Fairén, Alberto G.; Fernández-Remolar, David; Dohm, James M.; Baker, Victor R.; Amils, Ricardo (2004-09-23). "Inhibition of carbonate synthesis in acidic oceans on early Mars" (PDF). Nature. 431 (7007): 423–426. Bibcode:2004Natur.431..423F. doi:10.1038/nature02911. PMID 15386004</ref> Orbiting instruments, as well as instruments on landers have found sulfates that may have formed under acid conditions.<ref>https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160006674.pdf</ref> <ref>https://www.sciencedirect.com/science/article/pii/S0019103514003522</ref> <ref>Farrand, W., et al. 2014. Detection of copiapite in the northern Mawrth Vallis region of Mars: Evidence of acid sulfate alteration. Icarus: 241, 346-357.</ref>

===Water lost to space===

Of great significance in answering where the water went has come from advanced studies of the Martian atmosphere. In short, most of the atmosphere and water was lost into space by various processes.
As far back as 2001, NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) measurements of the ratio of molecular hydrogen to deuterium in the upper atmosphere of Mars suggested an abundant water supply on primordial Mars that has since been lost. Deuterium is a rare, heavy isotope of hydrogen. It has a neutron its nucleus. Since it is heavier, it tends to stick around longer. The ratio between the hydrogen and deuterium tells us how much has been lost in the past. <ref name=Krasnopolsky>cite journal | last1 = Krasnopolsky | first1 = Vladimir A. | last2 = Feldman | first2 = Paul D. | year = 2001 | title = Detection of Molecular Hydrogen in the Atmosphere of Mars | url = | journal = Science | volume = 294 | issue = 5548| pages = 1914–1917 | doi=10.1126/science.1065569 | pmid=11729314| bibcode = 2001Sci...294.1914K </ref>
Another later study, published in 2015, of water and deuterium came to the conclusion that Mars has lost the equivalent of an Arctic Ocean of water. <ref>Villanueva G. L., Mumma M. J., Novak R. E., Käufl H. U., Hartogh P., Encrenaz T., Tokunaga A., Khayat A., and Smith M. D., Science, Published online 5 March 2015 [DOI:10.1126/science.aaa3630]</ref> <ref>Villanueva, G., et al. 2015. Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs. Science 10 Apr 2015:Vol. 348, Issue 6231, pp. 218-221.</ref> This discovery was derived from the ratio of water and deuterium in the modern Martian atmosphere compared to the ratio found on Earth and derived from telescopic observations. Telescopic observations from the Earth found eight times the concentration of deuterium at the polar deposits of Mars than exists on Earth, signifying that Mars once had much greater levels of water. The telescopic values are within range that the ''Curiosity'' rover detected in Gale Crater.<ref>cite journal | last1 = Webster | first1 = C.R. | display-authors = 1 | last2 = et al | year = 2013 | title = Isotope Ratios of H, C, and O in CO2 and H2O of the Martian Atmosphere | url = | journal = Science | volume = 341 | issue = 6| pages = 260–263 | bibcode = 2013Sci...341..260W | doi = 10.1126/science.1237961 | pmid = 23869013 </ref> Dust storms also increase water loss.<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006616</ref> <ref>Fedorova, A. et al. 2020. Multi‐Annual Monitoring of the Water Vapor Vertical Distribution on Mars by SPICAM on Mars Express. JGR Planets. Volume126, Issue1
January 2021. e2020JE006616</ref>
Ten percent of the water loss from Mars may have been caused by dust storms, according to a study of dust storms with the Mars Reconnaissance Orbiter. Dust storms carry water vapor to very high altitudes; there ultraviolet light from the Sun can then break the water apart in a process called photodissociation. Hydrogen from the water molecule then goes into space.<ref>https://www.sciencenews.org/article/mars-dust-storms-water?mode=topic&context=36</ref> <ref>N. Heavens et al. Hydrogen escape from Mars enhanced by deep convection in dust storms. ''Nature Astronomy''. Published online January 22, 2018. doi: 10.1038/s41550-017-0353-4.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?release=2018-012&rn=news.xml&rst=7041</ref>

[[File:PIA03170 fig1duststroms.jpg |left|thumb|320px| Mars with and without a dust storm Dust storms may have caused 10% of the water loss from Mars into space. ]]

Further evidence that Mars once had a thicker atmosphere which would make an ocean more probable came from the MAVEN spacecraft that has been making measurements from Mars orbit. Bruce Jakosky, lead author of a paper published in Science, stated that "We've determined that most of the gas ever present in the Mars atmosphere has been lost to space."<ref>https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space</ref> This research was based upon two different isotopes of argon gas.<ref>B.M. Jakosky et al. 2017. Mars’ atmospheric history derived from upper-atmosphere measurements of 38Ar/36Ar. Science 355 (6332): 1408-1410; doi: 10.1126/science.aai7721</ref> <ref>http://www.sci-news.com/space/maven-martian-atmosphere-lost-space-04750.html</ref> Argon gas is inert, it does not react with anything; hence, the ratio of its isotopes gives an accurate reading of how much has been lost. Like deuterium, a heavy isotope of hydrogen, the heavy form of argon is not lost to space as easily as the lighter variety. A greater proportion of heavy isotope left on the planet means that more of the gas has disappeared. By studying the ratio of the heavier Ar38 to the lighter Ar36, scientists found that 65% of argon has left the planet. The main way that argon left the atmosphere was through a process called “sputtering.” Sputtering is a complex method in which the sun strips atmosphere from a planet. The sun is constantly shooting out particles at high speed. If one hits a gas particle in the atmosphere, it may directly knock it into space. Alternatively, it would cause an atom of atmosphere to lose an electron and thereby become an ion. Ions can interact with the sun’s magnetic field as it moves through space. In the such an exchange, the ion can then acquire energy and fly off into space or hit other atoms in the atmosphere, knocking them into space, as well.<ref> https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space</ref>

<gallery class="center" widths="380px" heights="360px">
File:1-Mars limb-1024x665maveninorbit.jpg|Artist’s conception of MAVEN orbiting Mars
File:Mars vs Earth Solar Wind-1024x576.png|Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field

File:Mavenargoninfographic2.jpg|Drawing showing how Mars lost argon and other gases into space

</gallery>

The shoreline of a Mars ocean is not even; also it is hard to account for where the all water came from and where it went. These big problems were potentially solved by a team of scientists, in 2018. They proposed that Martian oceans appeared very early--before or along with the growth of Tharsis. The great mass of the Tharsis volcanoes pulled the crust down making a deep basin. If the ocean was formed before the mass of Tharsis deepen the basins, much less water would be needed. Also, the shorelines would not be regular since Tharsis would still be growing and changing the position of the shoreline. As Tharsis volcanoes erupted they added huge amounts of gases (such as water, carbon dioxide, sulfur dioxide) into the atmosphere and created a global warming, thereby possibly allowing liquid water to exist.<ref>[https://www.sciencedaily.com/releases/2018/03/180319124255.htm Mars' oceans formed early, possibly aided by massive volcanic eruptions]. University of California - Berkeley. March 19, 2018.</ref> <ref>Citron, R., M. Manga, D. Hemingway. 2018. "Timing of oceans on Mars from shoreline deformation." ''Nature'' doi| 10.1038/nature26144</ref> <ref>Citro, R., et al. 2018. EVIDENCE OF EARLY MARTIAN OCEANS FROM SHORELINE DEFORMATION DUE TO THARSIS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1244.pdf</ref>

<gallery class="center" widths="380px" heights="360px">
File:Olympus Mons.jpg|Olympus Mons, the largest of the Tharsis volcanoes, pulled the crust down making a deep basin nearby. New research indicates that the ocean may have formed before Olympus Mons reached its final size; hence, the ocean may have been only half as deep as thought.
File:USGS-Mars-MC-9-TharsisRegion-mola.png|Most of the volcanoes of Tharsis These volcanoes and others may have released vast amounts of greenhouse gases.
</gallery>

However, it is hotly debated just how much of a global warming took place. Newest climate models show Mars to always have been too cold for much water to exist as a liquid. <ref> Forget et al. 2013 3D modelling of the early martian climate under a denser CO2 atmosphere: Temperatures and CO2 ice clouds. Icarus 222, 81-99.</ref> <ref> Wordsworth et al. 2013. Global modelling of the early martian climate under a denser CO2 atmosphere: Water cycle and ice evolution. Icarus 222, 1-19.</ref> <ref>http://astrobiology.com/2018/12/geologic-constraints-on-early-mars-climate.html</ref> One group of researchers have proposed that if an object 1000 km across were to strike Mars at certain angles that the large body would break up into small pieces and react with ice on the surface as well as the iron core of Mars. Such reactions could generate large amounts of hydrogen gas (3 times as thick as the Earth's atmosphere). This gas, being a greenhouse gas, could raise the temperature of the atmosphere.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/1067.pdf</ref> <ref>Woo, J., et al. 2019. MARS IN THE AFTERMATH OF COLOSSAL IMPACT. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 1067.pdf)</ref> Even though research studies continue to support a Mars ocean, there have been other ideas put forth to explain observations.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/2024.pdf</ref> <ref>Palumbo, A., J. Head. OCEANS ON MARS: THE POSSIBILITY OF A NOACHIAN GROUNDWATER-FED OCEAN IN A SUBFREEZING MARTIAN CLIMATE. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 2024.pdf</ref> Some have suggested a series of lakes rather than one large ocean. A recent study suggested a frozen ocean resulting from a succession of floods. Water from the outflow channels probably rushed out many times with long gaps between flooding events. Each time the water would have frozen. <ref>Carr, M., J. Head. In press. Mars: Formation and fate of a frozen Hesperian ocean. Icarus. https://doi.org/10.1016/j.icarus.2018.08.021</ref> <ref>Carr, M. 1996. Water on Mars. Oxford</ref> Circulation in an ocean may have warmed the surface up to 4.5°C, according to a study published in 2022. The research team noted that an ocean could be stable even if the average temperature of Mars was below 0°C.<ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/1467.pdf</ref> <ref>Schmidt, F. 2022. CIRCUMPOLAR OCEAN STABILITY ON MARS 3 GY AGO. 53rd Lunar and Planetary Science Conference (2022. 1467.pdf</ref>

===Tsunamis===

If Mars had an ocean for a time, there is a chance that sooner or later an asteroid would strike it and cause a great wave, called a tsunami. Evidence for two such events was published in May 2016. Parts of the surface in Ismenius Lacus quadrangle were altered by two tsunamis argue a large team of scientists. Both impacts which caused the tsunamis were powerful enough to leave behind 30 km diameter craters. The first picked up and transported boulders the size of small houses. The wave washed over the land, and then gravity pulled it back to lower ground and when it did, the backwash created channels by rearranging the boulders. The second came in when the ocean was 300 m lower. The second tsunami brought great deal of ice which was dropped in valleys. The average height of the waves would have been 50 m, but the heights would vary from 10 m to 120 m according to calculations. That means that some waves were tall enough to have gone way over the United States Capitol Building. Lobes of giant boulders went around obstacles and down low paths. Having such strikes are quite plausible, as simulations indicate that in this particular part of the ocean two impact craters of 30 km in diameter are expected every 30 million years. Two of these events imply that a huge ocean may have existed for millions of years. One persistent argument against an ocean has been the lack of shoreline features, but they may have been destroyed by these tsunamis. Chryse Planitia and northwestern Arabia Terra were studied in this research. <ref>http://astrobiology.com/2016/05/ancient-tsunami-evidence-on-mars-reveals-life-potential.html</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2016/pdf/1680.pdf | title=Tsunami waves extensively resurfaced the shorelines of an early Martian ocean. : | author=Rodriguez, J., et al. | journal=Scientific Reports / 47th Lunar and Planetary Science Conference | year=2016 | volume=6 | pages=25106 | doi=10.1038/srep25106| pmid=27196957 | pmc=4872529 | [https://www.nature.com/articles/srep25106 version at ''Nature'']</ref> <ref> [https://www.sciencedaily.com/releases/2016/05/160519101756.htm "Ancient tsunami evidence on Mars reveals life potential."] ''ScienceDaily''. 19 May 2016.</ref> The crater Lomonosov has been identified as a likely source of tsunami waves.<ref name = "Rincon2017">cite web | url = https://www.bbc.com/news/science-environment-39394583 | title = Impact crater linked to Martian tsunamis | last = Rincon | first = P. | date = 2017-03-26 | website = BBC | access-date = 2017-03-26</ref> <ref>Costard | first2 = A. | last2 = Séjourné | first3 = K. | last3 = Kelfoun | first4 = S. | last4 = Clifford | first5 = F. | last5 = Lavigne | first6 = I. | last6 = Di Pietro | first7 = S. | last7 = Bouley | title = Modelling Investigation of Tsunamis on Mars | book-title = Lunar and Planetary Science Conference|Lunar and Planetary Science XLVIII | pages = 1171 | publisher = Lunar and Planetary Institute | date = 2017 | location = The Woodlands, Texas | url = http://www.lpi.usra.edu/meetings/lpsc2017/pdf/1171.pdf | access-date = 2017-03-26</ref> <ref>Costard, F., et al. 2018. FORMATION OF THE NORTHERN PLAINS LOMONOSOV CRATER DURING A TSUNAMI GENERATING MARINE IMPACT CRATER EVENT. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1928.pdf</ref> <ref>https://www.techtimes.com/articles/203105/20170326/impact-crater-linked-to-powerful-tsunamis-on-mars-another-proof-of-an-ancient-ocean.htm</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JE006008</ref> Another possible crater for the origin was the crater Pohl. It's formation would have made the first tsunami, while the impact creating Lomonosov could have caused the second one.<ref>https://www.nature.com/articles/s41598-022-18082-2?utm_medium=affiliate&utm_source=commission_junction&utm_campaign=CONR_PF018_ECOM_GL_PHSS_ALWYS_DEEPLINK&utm_content=textlink&utm_term=PID100052172&CJEVENT=327985de727d11ed80c400a00a1c0e10</ref> <ref>Rodriguez, J.A.P., Robertson, D.K., Kargel, J.S. et al. Evidence of an oceanic impact and megatsunami sedimentation in Chryse Planitia, Mars. Sci Rep 12, 19589 (2022). https://doi.org/10.1038/s41598-022-18082-2</ref> <ref>https://www.livescience.com/mars-mega-tsunami-impact-point</ref> Pohl is 111 Km across and is located at 34.04 N and 323.01 E.<ref>https://planetarynames.wr.usgs.gov/Feature/Pohl</ref>

[[File:Pohloceancomposit.jpg|600pxr| Map showing location of Pohl Crater the source of the first tsunami]]

Map showing location of Pohl Crater the source of the first tsunami

<gallery class="center" widths="380px" heights="360px">

File:Mars Reconnaissance Orbiter spacecraft model.png|The Mars Reconnaissance Orbiter with its powerful HiRISE saw house-sized boulders that may have been carried and formed into channels by tsunamis.

ESP 028537 2270tsunamischannels.jpg|Channels made by the backwash from tsunamis, as seen by HiRISE The tsunami wave carried great boulders over the land, and then when the wave went back out to the sea channels like these were created.

28537 2270tsunamisboulders.jpg|Boulders that were picked up, carried, and dropped by tsunamis, as seen by HiRISE Tsunamis picked up and carried these boulders, the size of small houses.

Tsunamisstreamlinedp20008931.jpg|Streamlined island eroded by tsunami, as seen by HiRISE Tsunamis were probably caused by asteroids striking ocean.

File:MarsLomonosovCraterWinter.jpg|Lomonosov Crater in the winter with frost One of the two tsunamis may have been caused by the formation of this crater.
</gallery>

Evidence of other tsunami events was presented at the 50th Lunar and Planetary Science Conference (March 18–22, 2019) in The Woodlands, Texas.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/lpsc2019_program.htm</ref> Observations made by a large group of scientists showed that a large tsunami traveled up into the highlands at least ~1.2 km in
elevation over a distance of ~350 km. The paper's authors calculated that an impact ~150 km in diameter in a Martian northern ocean could have produced this tsunami. Deposits from the tsunami cover the lower reaches of Maumee Valles and most of the highland surfaces next to Kasei Valles, Maumee Valles, and Xanthe Montes. The [[Viking 1]] lander set down on a part of the deposit from the tsunami.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/2757.pdf</ref> <ref>Rodrignez, J., et al. 2019. A NASA SPACECRAFT MAY HAVE LANDED ON AN EARLY MARS MEGA-TSUNAMI DEPOSIT IN 1976. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 2757.pdf</ref> Another tsunami may have occurred from a landside that slide down [[Olympus Mons]], the largest volcano on Mars. The deposit went much further than expected for just a landslide. However, the great distance covered by landslide would have been expected if the material sliding down Olympus Mons were mixed with water from an ocean or smaller ponds. If this tsunami did occur that means that an ocean lasted until the early Amazonia period, at least in the area of Amazonis Arcadia Planitiae. So, an ocean may have lasted longer than previously thought.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/1573.pdf</ref> <ref>DeBlasio, F. 2019. LANDSLIDE-GENERATED TSUNAMI ON MARS? 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 1573.pdf</ref> <ref> Costard, F., et al. 2019. The Lomonosov Crater Impact Event: A Possible Mega‐Tsunami Source on Mars. JGR. Volume124, Issue7. Pages 1840-1851,</ref>

== References ==
{{reflist}}

==See also==
* [[Geography of Mars]]
* [[Global warming]]

* [[Greenhouse effect]]
* [[High Resolution Imaging Science Experiment (HiRISE)]]
* [[Mars Global Surveyor ]]
* [[MAVEN]]
* [[Rivers on Mars]]
* [[Tharsis]]
* [[Water]]

[[Category: Climate]]

== External links ==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* [https://www.youtube.com/watch?v=EoUy4lsgRo8 NASA | Mars Atmosphere Loss: Sputtering]

*[https://www.youtube.com/watch?v=Y4vVFetfSF8 MAVEN | Measuring Mars' Atmospheric Loss]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]

*[https://en.wikipedia.org/wiki/Water_on_Mars Wikipedia page on water on Mars]

*[https://www.bing.com/videos/search?q=nasa+gsfc+mars+ocean&view=detail&mid=435F5E5E3D31FFF0D5AC435F5E5E3D31FFF0D5AC&FORM=VIRE NASA | Mars' Ancient Ocean]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]

* [https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

* [https://www.youtube.com/watch?v=1SRmXG6UnHY&t=1335s Dr. Geronimo Villanueva - Ancient Ocean on Mars - 18th Annual International Mars Society Convention]

* [https://www.youtube.com/watch?v=WH8kHncLZwM NASA | Measuring Mars' Ancient Ocean]

* [https://www.youtube.com/watch?v=GX9XzRyuYLc Oceans and Life on Mars]
* [https://www.youtube.com/watch?v=HyV4K7EeV3U Scientists Identify a Crater that Created Massive Tsunamis on Mars]
*[https://www.youtube.com/watch?v=b4hCWIQsyps Mars: Ancient Water, Present Day Ice]
* [https://www.youtube.com/watch?v=bs8wTdCJ-NA What Happened To All The Water On Mars?]
*[https://www.youtube.com/watch?v=EJk0hS4_gz4 Water on Mars and the Potential for Martian Life]
*[https://www.youtube.com/watch?v=gtcEdeezuYg Explore the Geology of Mars]

Lakes on Mars

2023-03-20T23:21:37Z

Suitupandshowup: /* External links */

{{Mars atlas}}
Lakes on Mars
Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

It is believed that there were hundreds of lakes on Mars—over 200 inside of craters.<ref>
Fassett C. I. and Head J. W. 2008. Icarus. 195 61</ref> <ref>Goudge T. A., Aureli K. L., Head J. W., Fassett C. I. and Mustard J. F. 2015 Icarus. 260 346</ref> Water for the lakes came from various sources such as rainfall, runoff from surrounding land, melting of glaciers, and from groundwater [[sapping]].<ref>Benjamin D. Boatwright and James W. Head. 2021. Planet. Sci. J.Volume 2. Number 2. p. 52</ref> <ref>Salese F., Pondrelli M., Neeseman A., Schmidt G. and Ori G. G. 2019. JGRE. Vol. 124. P. 374</ref>

<gallery class="center" widths="380px" heights="360px">

File:B17 016128 1596glaciersmarssocietywithglaciersjpg.jpg|Crater with glaciers drawn in white. Glaciers were on walls. When they melted, channels took the water to the center of crater, and created a lake. The channels are now inverted. That is they formed ridges.

File:B17 016128 1596glaciersmarssociety.jpg|Inverted channels on a crater floor. They run from where the glaciers were toward the center.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:J03 045825 2081sappingcraterarrowslabeled.jpg|Crater showing valleys that formed from sapping--that is the water flowed out of the ground. Eventually, the water formed a lake.

File:J03 045825 2081sappingcraterdelta.jpg|Red arrows show deltas that formed from water that issued from the ground in sapping valleys. This is evidence that water came out of the ground and made a lake.

</gallery>

One evidence for lakes is the presence of deltas in craters. Deltas form when water flows into a quiet body of water.

==Images of possible deltas==

<gallery class="center" widths="380px" heights="360px">

Image:Delta in Margaritifer Sinus.jpg|Possible delta in [[Margaritifer Sinus quadrangle]] as seen by THEMIS.
Image:Distributary fan-delta.jpg|Probable delta in Eberswalde Crater that lies to the NE of Holden Crater, as seen by Mars Global Surveyor. Image in [[Margaritifer Sinus quadrangle]].
Image:Delta in Lunae Palus.jpg|Delta in [[Lunae Palus quadrangle]], as seen by THEMIS.
Image:Delta as seen by HiRISE.jpg|Delta that fills a crater in [[Lunae Palus quadrangle]], as seen by HiRISE.
Image:605555-PIA15097-JezeroCrater-Delta.jpg|[[Jezero Crater]] delta - chemical alteration by water ([[:File:260184-JezeroCrater-Delta-Full.jpg|hi-res]])

</gallery>

Some places that are believed to have once held lakes are [[Holden Crater]], [[Jezero Crater]], [[Gale Crater]], [[Ritchey Crater]], [[Columbus Crater]], [[Valles Marineris]], Argyre basin, Hellas Basin, and large areas in Eridania.

<gallery class="center" widths="380px" heights="360px">

File:Martian impact crater Holden based on day THEMIS.png|Holden Crater, as seen by THEMIS

File:Martian crater Columbus based on day THEMIS.png|[[Columbus Crater]]

[[File:Martian impact crater Holden based on day THEMIS.png]]|[[Holden Crater]], as seen by THEMIS. Image is located in the [[Margaritifer Sinus quadrangle]].

</gallery>

<gallery class="center" widths="380px" heights="360px">

Image:Topographic Map of Gale Crater.jpg|Gale Crater with Aeolis Mons rising from the center. The noted [[Curiosity]] landing area is near Peace Vallis in Aeolis Palus. Curiosity landed in the northern part of the crater.

</gallery>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg|600pxr|View from the "Kimberley" formation on Mars taken by NASA's Curiosity rover.]]

View from the "Kimberley" formation on Mars taken by NASA's Curiosity rover. Layered rock formed under lake.

<gallery class="center" widths="380px" heights="360px">
PIA22059 fig1eridaniadepths.jpg|Map showing estimated water depth in different parts of Eridania Sea This map is about 530 miles across.

PIA22059 fig1eridaniadepthslabeled.jpg|Features around Eridania Sea labeled
</gallery>

Another major form of evidence is the finding of minerals such as clays, carbonates, and sulfates. These minerals require water to be produced. These minerals were both detected from orbit and from rovers on the surface of Mars. The Curiosity Rover has been exploring Gale crater for years with very sophisticated instruments. Many of the minerals identified were hydrated which required water. Some of these hydrated minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

== Underground Lakes Near the South Pole ==
Deep penetrating radar detected several possible lakes of liquid water (or brine) under the polar cap near the South Pole. It was thought that these were kept liquid by geothermal heat. However, modelling suggested that they should freeze. Currently the theory is that they are not lakes at all, but bands of clay material. Under the right amount of pressure, they would give a radar return like water.<ref>https://www.scientificamerican.com/article/buried-lakes-on-mars-may-just-be-frozen-clay/</ref>

==See also==
*[[Aeolis quadrangle]]
*[[Columbus Crater]]
*[[Curiosity]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Holden Crater]]
*[[Jezero Crater]]
*[[Margaritifer Sinus quadrangle]]
*[[Spirit]]

==References==

{{Reflist|30em}}

== External links ==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* [https://en.wikipedia.org/wiki/Lakes_on_Mars Lakes on Mars]

* [https://www.youtube.com/watch?v=9rbnvdWk3eg The Lakes and Rivers of Ancient Mars]
* [https://www.youtube.com/watch?v=DGBbke1wJRk Lakes on Mars - Nathalie Cabrol (SETI Talks)]

* [https://www.youtube.com/watch?v=a4UiwmbrI3o Researchers discover a new type of crater lake on Mars' surface]

* [https://www.youtube.com/watch?v=QWcdAvFN_q0 James Wray - The Search for Water and Life on Mars (and Beyond) (November 15, 2018)]
*[https://www.youtube.com/watch?v=b4hCWIQsyps Mars: Ancient Water, Present Day Ice]

* [https://www.youtube.com/watch?v=bs8wTdCJ-NA What Happened To All The Water On Mars?]
*[https://www.youtube.com/watch?v=EJk0hS4_gz4 Water on Mars and the Potential for Martian Life]
* [https://www.youtube.com/watch?v=d-27kmtkrog Advances in the Mineralogy of Mars]
* [https://www.youtube.com/watch?v=K5tbrf9TNak Mars Crater Modification in the Late Noachian:]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]
* [https://www.youtube.com/watch?v=wI183V7evbg Seeking Signs of Ancient Life in Jezero Crater with the Mars 2020 Perseverance Rover 103 minutes]

Geological processes that have shaped Mars: Why Mars looks like it does

2023-03-20T23:19:59Z

Suitupandshowup: /* Recommended reading */ added to list

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:Mars, Earth size comparison.jpg|left|thumb|px|Earth and Mars Earth is much bigger, but both have the same land area. Mars has about one third the gravity of the Earth.]]

Mars looks like it does because of certain geological processes. Some of them are common to both the Earth and Mars. However, others are rare or nonexistent on the Earth. Mars shows an extremely old record of the past that is lacking on the Earth. Plate tectonics and vigorous air and water erosion has wiped out nearly all of the past geology of the Earth. In contrast, much of the Martian surface is billions of years old. Another factor that has affected the appearance of Mars is its extreme cold. The coldness of the planet makes carbon dioxide significant. It has influenced Mars both as a gas and as a solid. As a greenhouse gas, early in the history of the planet, it may have been thick enough in the atmosphere to help raise the temperature enough to permit water to flow, to carve rivers, to form lakes and an ocean. Indeed, it may have been warm enough from carbon dioxide for life to first originate on Mars and then travel to the Earth on meteorites. Today, as a solid, carbon dioxide (dry ice) produces the ubiquitous gullies found in numerous areas of the planet.

==Erosion Related==

As on the Earth material was laid down and then later eroded. Many spectacular scenes are present with places that were mostly eroded, but with remnants remaining in the form of buttes and mesas. Sometimes, sediments were put down in layers. As a result beautiful places were created. On the Earth we admire such layers in Monument Valley and many beautiful canyons. The same types of landscapes show up on Mars.
The top layer of buttes and mesas is hard and resistant to erosion. It protects the lower layers from being eroded away. On Mars that hard, cap rock could be made from a lava flow. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area.

<gallery class="center" widths="380px" heights="360px">

File:16 21 2117 monument valley.jpg|Spearhead Mesa in Monument Valley Note the flat top and steep walls that are characteristic of mesas.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it.

File:58563 2225mesa.jpg|Mesa

File:45016 2080mesas.jpg|Mesas, as seen by HiRISE under HiWish program These are like the ones in Monument Valley

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte: Buttes have a much smaller area than mesas, but both have a hard cap rock on the top. Box shows the size of a football field.

</gallery>

As on the Earth, there are landslides. However, they could be a little different since Mars has only about a third of Earth’s gravity.

<gallery class="center" widths="380px" heights="360px">

File:ESP 043963 1550landslide.jpg|Landslide

</gallery>

Common features in certain areas of the Earth’s surface are “Yardangs.” They are found in desert areas which contain much sand. The wind blows sand and shapes the relatively soft grained deposits into the long, boat shapes of yardangs. On Mars it is thought that these forms are the result of the weathering of huge ash deposits from volcanoes. Mars has the biggest known volcanoes in the solar system. Many probably threw out much fine-grained material which was easily eroded to make vast fields of yardangs. Regions called the “Medusa Fossae Formation and Electris deposits contain thousands of yardangs.

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs.jpg|Yardangs
</gallery>

Unlike the Earth, Mars shows landscapes that are billions of years old. In that time material has been deposited and then eroded and/or greatly changed. Some features have been “inverted.” Low areas turned into high areas. Low areas like stream beds were filled with erosion-resistant materials like lava and large rocks. Later, the surrounding, softer ground became eroded. As a result, the old stream bed now appears raised. We can tell it was originally a stream bed since the overall shape from above still looks like a stream with curves and branches.

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Inverted streams Here a branched stream became filled with hard material and then the surrounding ground was eroded.]]

Another structure made with erosion is a “pedestal crater.” They are abundant in regions far from the equator. These craters seem to sit on little circular shelves or pedestals.<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> In the impacting process, ejecta fell about the crater and protected the underlying ground from erosion. These craters occur where we think there was a great deal of ice in the ground. So, much of the material that disappeared was just ice. With that being said, pedestal craters give us an indication of how much ice was in the region. In some places hundreds of meters of ice-rich ground were removed to make pedestal craters.<ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

[[File:ESP 037528 2350pedestal.jpg |thumb|left|px||Pedestal crater Surface close to crater was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

[[Image:Pedestal crater3.jpg |thumb|right|px||Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings]]

[[File:Pedestaldrawingcolor2.jpg|thumb|600px|center|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

Some structures on Mars are being “exhumed.” Craters are observed that are being uncovered. In the past, impacts produced craters. Later, they were buried. Now they are in the process of being uncovered by erosion. When an asteroid strikes the surface it generates a hole and throws out ejecta all around it. A circular hole is the result. If we see a half of a crater, we know that that it is being exposed by erosion. Impacts do not produce half holes!

<gallery class="center" widths="380px" heights="360px">

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]
</gallery>

==Craters==

Impact craters occur on both the Earth and Mars. However, due to the extreme age of the Martian surface, most of Mars shows a high density of impact craters especially in the southern hemisphere. Craters do not last long on the Earth. Remember, the Earth experiences a great deal more erosion due to its thick atmosphere and abundant water. And, at intervals, the crust is taken into the Earth at plate boundaries. We know a fair amount about impact craters because the Earth has impact craters like Meteor Crater in Arizona that we can study easily.

<gallery class="center" widths="380px" heights="360px">

File:Barringer Crater USGS.jpg|Meteor Crater in Arizona
</gallery>

We know that a new crater will have a rim and ejecta around it. Large ones may have a central uplift and maybe a ring around the middle of the floor. We know that the impact brings up material from deep underground.<ref>https://www.uahirise.org/hipod/PSP_007464_1985</ref> If we study the rocks in the central mound and in the ejecta, we can learn about what is deep underground. During an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE Colors show different minerals--some used to be deep underground.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterejectarim.jpg|Young crater showing layers, rim, and ejecta. Ejecta was thrown out by the force of impact.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.
</gallery>

The heat from an impact into ice-rich ground may produce channels emanating from the edge of the ejecta. These have been seen around a number of craters.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

</gallery>

Mars shows some interesting variations to the usual appearance of craters. At times the force of an impact reaches down to a different type of layer. The lower layer may be of a different color; therefore the ejecta that is spread on the landscape may be a different color.

<gallery class="center" widths="380px" heights="360px">
File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta Impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:29565 2075newcratercomposite.jpg|New, small crater Meteorite that hit here throw up dark material that was under a layer of bright, surface dust. We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref>

File:ESP 011425 1775newcrater.jpg|Dark ejecta of a new crater covers the bright surroundings.
</gallery>

Sometimes it looks as if an impact caused rocks to melt and when the molted rocks landed on the crater floor steam explosions occurred with ice-rich ground. What results is ground with a high density of pits.

<gallery class="center" widths="380px" heights="360px">
File:ESP 012531 1435pits.jpg|Floor of Hale Crater showing pits from steam explosions when hot, melt from an impact landed.

</gallery>

On occasion, an impact may go down to ice-rich ground or maybe to a layer of ice. Indeed, a number of craters expose ice on their floors which after a period of time disappears into the thin Martian atmosphere.

<gallery class="center" widths="380px" heights="360px">

File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
</gallery>

Then there is a type of crater which is common in locations we think contain much ice. Called “ring-mold” craters, they may be caused by a rebound of an ice layer. Experiments in labs confirm that this behavior can occur. Ring-mold craters are called that because they resemble ring-molds used in baking.

<gallery class="center" widths="380px" heights="360px">

File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.

26055ringmoldcrater.jpg|Close view of ring mold crater.
</gallery>

[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Now, during the impact process much material is sent flying in the air. Some of it will come down and create new craters. These are called secondary craters. They can be identified by all being of the same age. In addition, sometimes molted rock is produced by the impact. If molten rock lands on ice-rich ground, an area with a high density of pits will form. The hot molten rocks cause ice in the ground to burst into steam and cause pits to form.

<gallery class="center" widths="380px" heights="360px">

File:ESP 030244 2040secondarycraters.jpg|Secondary craters These are formed from material that is blasted way up in the air from the impact. Evidence that they are secondary craters is that they are all of the same age.
</gallery>

==Glaciers==

Mars may have had much water in past ages. Much of that water is now frozen in the ground and locked up in glacier-like forms. Many features have been found that are like glaciers—in that they are mostly made of ice and flow like glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> That means they move slowly and in a downhill direction. For ice to exist under today’s climate conditions, it must be covered with a layer of debris—dust, rocks, etc. A layer several meters or a few tens of meters thick will preserve ice for millions of years. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> Under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>
Martian glaciers show evidence of movement on their surfaces and in their shapes. The actual existence of water ice in some of them has been proven with radar studies from orbit. <ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> Some of them look just like alpine glaciers on the Earth. Most show piles of debris called moraine. This was material that was removed from one place and moved along to another by ice. Also, shapes looking just like eskers of terrestrial glaciers are common in places. Eskers form from streams moving under glaciers. These streams deposit rocks in tunnels in the ice at the bottom of glaciers. When the ice goes away, curved ridges stay behind.

<gallery class="center" widths="380px" heights="360px">

File:R0502109dorsaargentea.jpg|Possible eskers indicated by arrows. Eskers form under glaciers.

Wikilau.jpg|Lau Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Curved ridges are probably eskers which formed under glaciers.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.

File: Wikielephantglacier.jpg|Glacier in Greenland Glacier spreads out when it leaves valley.
</gallery>

For Mars, a number of names have been applied to these glacier-like forms. Some of them are tongue-shaped glaciers, lobate debris aprons (LDA’s), lineated valley fill (LVF), and concentric crater fill (CCF).<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 035327 2255tongues.jpg|Tongue-shaped glaciers These were made when a flow encountered an obstacle that made it split into two.
File:ESP 036619 2275ldalabeled.jpg|Lobate debris apron LDA) around a mound <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust . <ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref>

File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are now almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed. <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>
</gallery>

[[File:ESP 052138 1435lvf.jpg|thumb|600px|center|Lineated valley fill, as seen by HiRISE under [[HiWish program]]]]

==Ice in the ground==

Mars has some unique landscapes and features that are common just to it. Since so much water is frozen in the ground and since the thin atmosphere of Mars allows ground ice to disappear when it became exposed, unreal scenes can develop. Under current conditions on Mars, ice sublimates when exposed to the air. In that process, ice goes directly to a gas instead of first melting. It often starts with small, narrow cracks that get larger and larger. Once ice leaves the ground there is not much left except dust. And winds will eventually carry the dust away. The end result is various shaped holes, pits, canyons, and hollows. Some of these forms are called brain terrain, ribbed terrain, hollows, scalloped terrain, and exposed ice sheets. <ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> All of these may be of use to future colonists who need to find supplies of water.

[[File:45917 2220brainsopenclosed.jpg|Open an closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>]]

Open and closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows.

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> <ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref>
PIA22078 hireswideview.jpg|Wide view of triangular depression The colored strip shows the part of the image that can be seen in color. The wall at the top of the depression contains pure ice. This wall faces the south pole. <ref>Supplementary Materials Exposed subsurface ice sheets in the Martian mid-latitudes Colin M. Dundas, Ali M. Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, Nathaniel E. Putzig, Donna Viola, Sarah Sutton, Erin Clark, John W. Holt</ref>

PIA22077 hirescloseblue.jpg|Close, color view of wall containing ice from previous image <ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> <ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref>
</gallery>

[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of hollowed terrain caused by ice leaving the ground Box shows size of football field.]]

Close view of terrain caused by ice leaving the ground Box shows size of football field.

Other signs of water ice in the ground are: lobed (rampart craters), patterned ground, and possible pingos. Pattered ground or polygonal ground is common in ice-rich areas on Earth.

<gallery class="center" widths="380px" heights="360px">

File:56942 1075icepolygonslabeled2.jpg|Polygons Ice is in the low troughs that lie between the polygons.<ref>https://www.uahirise.org/ESP_047247_1150</ref>

</gallery>

Pingos are mounds that contain a core of ice.<ref>http://www.uahirise.org/ESP_046359_1250</ref> <ref>Soare, E., et al. 2019.</ref> <ref> Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref> They often have cracks on their surfaces. Cracks form when water freezes and expands. Pingos would be useful as sources of water for future colonies on the planet.

<gallery class="center" widths="380px" heights="360px">
51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.
ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program
</gallery>

Craters with ejecta that look like they were made by an impact into mud are called lobed or rampart craters. They were discovered by early, orbital missions to Mars. They are most common where we expect ice in the ground.

<gallery class="center" widths="380px" heights="360px">
File:Mars rampart crater.jpg|Yuty Crater showing lobe and rampart morphology; it looks like mud was formed during the impact.

</gallery>

Channels are sometimes found in a crater's ejecta or along the edges of the ejecta. Heat from the ejecta probably melted ice in the ground. Much heat is produced with an impact.

<gallery class="center" widths="380px" heights="360px">
File:ESP 055530 2180channels.jpg

</gallery>

==Liquid water==

Mars used to have lots of water and maybe a much thicker atmosphere billions of years ago. With liquid water, life is possible. Indeed, life may have first appeared on Mars before it occurred on Earth. Martian organisms could have been knocked off Mars by low angle asteroid impacts and found their way to Earth. Perhaps, the DNA of all Earthly organisms, included us, still contains genes from early Martian life. When we have samples of Mars brought back to Earth, we may find traces of DNA that are like ours.
Data are still being gathered and ideas debated, but scientists think that once Mars cooled down and lost its magnetic field, the solar wind may have carried away much of its atmosphere. In addition, some researchers have suggested that some of the atmosphere was splashed out by impacts. After the planet cooled, water became frozen in the polar ice caps and in the ground. But, for some period there was liquid water.

[[File:Mars vs Earth Solar Wind-1024x576.png|Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field]]

Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field

[[File:Mavenargoninfographic2.jpg|This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.]]

This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.

Huge amounts of water had to be present to carve the many outflow channels and produce the valley networks. Many of the outflow channels begin in "Chaos Terrain." Such a landscape often is where the ground seems to have just collapsed into giant blocks.<ref>https://marsed.asu.edu/mep/ice/chaos-terrain</ref> <ref>https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-9213-9_46-2</ref> It is believed that a shell of ice was created when the planet's climate cooled. Perhaps, at times the shell was broken by asteroid impacts, movements of magma, or faults. Such events would allow pressurized water to rapidly escape from under the shell of ice (shell has been called a cryosphere). Evidence is accumulating for the existence of an ocean. Lakes existed in low spots, especially craters.

[[File:ESP 056689 2210channelslowspotcropped.jpg |thumb|right|px||Channels that empty into a low area that could have been a lake Arrows show channels that lead to a low area that could have hosted a lake.]]

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel

These forms were shaped by running water.

<gallery class="center" widths="380px" heights="360px">

File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.

File:Ravi Vallis.jpg|Ravi Vallis was formed when the ground released a great flood of water from Aromatum Chaos. Maybe it started when hot magma moved under the ground.

File:Ister Chaos.jpg|Ister Chaos Water may have come out of this landscape when the ground broke up into blocks.<ref>https://www.uahirise.org/hipod/PSP_008311_1835</ref>

File:Branched Channels from Viking.jpg|These valley networks look like they were made from precipitation.
</gallery>

At present, it is hotly debated just how long water stayed around. The sun was not as strong billions of years ago. Greenhouse gases like carbon dioxide, methane, and hydrogen may have made Mars warm enough for liquid water. Massive volcanoes would have given up many of these gases, along with water vapor.

[[File: Olympus Mons Side View.svg.png|thumb|left|300px|Height of Olympus Mons compared to tall mountains on Earth]]

Maybe the water just existed for short periods. Some studies have showed that large impacts into icy ground could release water and change the local climate for thousands of years. Also, impacts may have punctured an ice shell and allowed pressurized water to flow out for a time. Any water moving on the surface would quickly freeze at the top. But, it would continue to flow under the ice for a long time and make many of the channels we see today. Heat to allow water to flow may have been from underground flows of magma. On the other hand, many of the features created by liquid water could have formed under massive ice sheets where water was insulated from the Martian atmosphere.
 
==Layers==

Many locations display layered formations. Some are mostly just made of ice and dust. These types of layers are common in the polar ice caps, especially the northern ice cap.<ref>https://www.uahirise.org/hipod/PSP_008244_2645</ref> Other, rockier layers, are visible in the walls of impact craters and canyon walls.

<gallery class="center" widths="380px" heights="360px">

File:PSP 008244 2645northicecaplabeled.jpg|Layers in northern ice cap that are exposed along a cliff

File:ESP 054515 2595icecaplayers.jpg|Close view of many layers exposed in northern ice cap
File: 57080 1380layerscratercolor.jpg|Layers in crater wall in Phaethontis quadrangle, as seen by HiRISE under HiWish program
48980 1725layersclose2.jpg|Close view of layers in Louros Valles
</gallery>

And then there are layers that may be more recent, they may be connected to repeated climate changes. Some have regularity to them. The climate of Mars changes drastically due to changes in the tilt of its rotational axis. At times, like now, it is close to the Earth’s 23.5 degrees. But, at times it may be as much as 70 degrees.<ref> Schorghofer, Norbert (2008). "Temperature response of Mars to Milankovitch cycles". Geophysical Research Letters. 35 (18): doi:10.1029/2008GL034954.</ref> <ref>ouma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref>Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Tilt governs the seasons and where ice is distributed. Currently, the largest deposit of ice is at the poles. At other times could have been at mid-latitudes. Imagine how it would be to have Pittsburgh under an ice cap. Mars may have had ice caps at the latitude of Pittsburgh.

<gallery class="center" widths="380px" heights="360px">

File:Mars Ice Age PIA04933 modest.jpg|How Mars may have looked with a greater tilt of Mars' rotational axis caused increased solar heating at the poles. This larger tilt would make a surface deposit of ice and dust down to about 30 degrees latitude in both hemispheres.
</gallery>

There is an ice-rich material that falls from the sky. It is called latitude dependent mantle.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It is thought to come from snow and ice-coated dust. At times, there is a lot of dust in the air. When that happens, moisture will freeze onto dust grains. When the ice-coated dust particle gets heavy enough, it will fall. Recent accumulations of this mantle look smooth. In some places the mantle is layered. Some formations, particularly in protected spots in craters and against mounds, suggest that these layered formations had many more layers. The wind sometimes shapes them into layered mounds.

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.
[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210dipping.jpg|Layers leaning against a mound The mound protected them from erosion.
</gallery>

The older layers visible on crater and canyon walls may have different sources. Some are from lava flows or ash from volcanoes. Some may have formed under water like most layered sedimentary rocks on the Earth.<ref>https://www.uahirise.org/PSP_008391_1790</ref> Curiosity, our robotic explorer, has found that layers in Gale Crater were made from sediments at the bottom of a lake. Some may be just from dust and debris settling in low areas and then being cemented by rising groundwater carrying minerals like sulfates and silica.<ref> Rates and mechanisms of chemical weathering of ferromagnesian silicate minerals on Mars | date = 1993 | last1 = Burns | first1 = Roger G | journal = Geochimica et Cosmochimica Acta | volume = 57 | issue = 19 | pages = 4555–4574 |</ref> <ref>{{cite journal | doi = 10.1029/92JE02055 | title = Rates of Oxidative Weathering on the Surface of Mars | date = 1993 | last1 = Burns | first1 = Roger G. | last2 = Fisher | first2 = Duncan S. | journal = Journal of Geophysical Research | volume = 98 | issue = E2 | pages = 3365–3372 |</ref> <ref>Hurowitz | first1 = J. A. | last2 = Fischer | first2 = W. W. | last3 = Tosca | first3 = N. J. | last4 = Milliken | first4 = R. E. | year = 2010 | title = Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars | url = https://authors.library.caltech.edu/18444/2/ngeo831-s1.pdf| journal = Nat. Geosci. | volume = 3 | issue = 5| pages = 323–326 | doi = 10.1038/ngeo831 | </ref> Sometimes a crater may have been filled up with layered rocks and then the rocks may have been eroded by the wind in such a way to just leave a layered mound in the center of the crater. Gale crater, where Curiosity is exploring, was like that.

<gallery class="center" widths="380px" heights="360px">

Image:Topographic Map of Gale Crater.jpg|Gale Crater with Aeolis Mons rising from the center. The noted [[Curiosity]] landing area is near Peace Vallis in Aeolis Palus. Curiosity landed in the northern part of the crater. Colors indicate elevation.

File:Marscratermounds.jpg|Some layers form mounds in the center of craters. They could have been made by the erosion of layers that were deposited after the impact.

</gallery>

[[File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|600pxr|Rock layers in the Murray Buttes area in lower Mount Sharp They look like rocks formed at the bottom of lakes and their chemistry proves it.]]

Rock layers in the Murray Buttes area in lower Mount Sharp

==Igneous effects==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

<gallery class="center" widths="380px" heights="360px">
File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons

</gallery>

Igneous refers to rock that is heated to a molten condition. On Mars, this is a major shaper of landscapes. Lava comes out of the ground at holes called vents. Flows of lava can be about as fluid as water and move long distances. Sometimes the top cools to a solid, but the liquid rock continues to flow underneath a hard crust. Giant pieces of this stiff crust can move around as “lava rafts.”

<gallery class="center" widths="380px" heights="360px">

File:ESP 054891 2040lavarafts.jpg|Lava rafts
</gallery>

In other places, lava travels in channels. When they make a hard crust, lave tunnels are created. A picture below shows lava tunnels.<ref> https://www.uahirise.org/PSP_009501_1755</ref> After the liquid lava moves away, an empty tunnel can be formed. These are significant for future colonists as they may be where our first colonies will be built. There people would be protected from surface radiation. We have already found spots that might be openings to these tunnels in HiRISE images.

[[File:PSP 009501 1755lavatube.jpg |Lava tubes and lava tunnels Future colonists may live in lava tunnels.]]

[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|left|Possible cave entrance to a lava tunnel Future colonies may live in caves for protection from weather and radiation.]]

[[File:Tharsis mons Viking.jpg |right|thumb|px|Some of the Martian volcanoes, as seen by Viking 1]]

There are huge volcanoes that were noticed by our first spacecraft to orbit the planet. The first satellite to orbit the planet was only able to see a few volcanoes peeking above a massive global dust storm. Since Mars has not had plate tectonics for nearly all of its history, volcanoes can grow very large.<ref>https://www.jpl.nasa.gov/edu/learn/video/mars-in-a-minute-how-did-mars-get-such-enormous-mountains/</ref> Lava and ash can erupt from the same spot for long periods of time. On the Earth, the plates move so volcanoes can only grow so big.

<gallery class="center" widths="380px" heights="360px">

File:Olympus Mons alt.jpg|Olympus Mons, tallest volcano in solar system The mass of volcanoes on mars stretches and cracks the crust causing faults.

</gallery>

Volcanoes are only the surface manifestations of liquid rock. There is more molted rock moving under the surface than what we see above ground in volcanoes. Molted rock is called magma when underground. Stretching out around volcanoes underground are various structures. Vast linear walls, called dikes radiate out from volcanoes. On Mars they can be many miles in length. Many form by moving along cracks or weak parts of rocks. Some scientists have suggested that they from long troughs when they melt ground ice. Troughs are some of the longest features on Mars.

<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 2100dike2.jpg|Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

</gallery>

Besides the direct action of lava and magma, volcanoes affect Mars with just their weight. The mass of a volcano stretches the crust and makes cracks form. The large canyon system of Valles Marineris may have been started with some sort of stretching of the crust. But, its stretching may have been caused by rising mantle plumes or maybe the rise of Tharsis where so many volcanoes are located.<ref>https://astronomy.com/magazine/ask-astro/2013/08/valles-marineris</ref> Cracks in the crust are called faults. Faults on Mars are often double faults. A center section is lower than the sides. This arrangement is called a graben. On the Earth they can turn into lakes like Lake George in New York State. Graben on Mars can be thousands of miles long.

Researchers have discovered that there is a large plume under Cerberus Fossae. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). Plumes like this are like the plume under Hawaii.

Evidence for the plume are (1) origin of nearly all Marsquakes, (2) a rise of a mile above the surroundings, (3) crater floors tilted away from the rise, and (4) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.

The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

<gallery class="center" widths="380px" heights="360px">

File:Troughs in Elysium Planitia.jpg|Troughs showing layers The center section of the picture is in color. With HiRISE only a strip in the middle is in color. These troughs are in Cerberus Fossae, as seen by HiRISE under the HiWish program. Location is 15.819 N and 161.448 E. Cerberus Fossae is the source of most of the Marsqukes detected by the InSight mission.

ESP 046251 2165graben.jpg|Straight trough is a fossa that would be classified as a graben. Curved channels may have carried lava/water from the fossa. Picture taken with HiRISE under [[HiWish program]].

File:ESP 057834 2005troughmesa.jpg|Trough or graben cutting through mesa
</gallery>

Sometimes lava moves over frozen ground. That results in steam explosions. Large fields of small cones can be produced when this happens. Those cones are called “rootless cones” since they do not go down very far.

<gallery class="center" widths="380px" heights="360px">

File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones
File:45384 2065cones2.jpg|Close view of rootless cones
</gallery>

Volcanoes sometimes explode with great amounts of ash that travels long distances, covering everything. Some of the layers seen on Mars are probably from these ash deposits. These deposits do not contain boulders and are easily eroded by just the wind. Two areas on Mars have widespread and thick deposits made in this way; they are called the Medusae Fossae Formation and the Electris deposits. These relatively soft deposits often form shapes called yardangs. They are sort of boat shaped and show the direction of the prevailing wind when they were created.

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
</gallery>

Much of the atmosphere of Mars came from volcanoes. Volcanoes give off large amounts of carbon dioxide and water, along with other chemicals. Some of these chemical compounds are “greenhouse gases” that served to heat up early Mars.
A few places are thought to be where volcanoes erupted under ice. The shapes that resulted look like those made on Earth when a volcano erupted under the ice.

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

==Bright dust==

A thin coating of bright-toned dust covers almost all parts of Mars. It has a rust brown color. It is not too noticeable until it is not here. Some things remove the dust and then reveal the dark underlying surface. The contrast between this thin coating and the underlying dark rock is striking. Much of the difference derives from how NASA pictures are processed.<ref> Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> To bring out more detail, the brightest tone is considered white, while the darkest black. It only takes a very thin layer of dust to make a difference in the over-all appearance of a picture. Experiments on Earth found that the layer may be only as thick as the diameter of a human hair.<ref> https://en.wikipedia.org/wiki/Micrometre
</ref> Incidentally, the dust has the color of rust because it is rust—it is oxidized iron.

Dark slope streaks occur when bright dust avalanches down steep slopes like crater walls. They can be very long and elaborate. These movements are affected by obstacles like boulders. A streak may split into two when encountering a boulder. They may be initiated when an impact happens nearby.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars" ''Icarus'' 2012; 217 (1) 194 </ref><ref>http://redplanet.asu.edu/</ref>
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>

[[File:ESP 043128 2005mesastreaks.jpg|600pxr|Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]]]

Dark slope streaks on layered mesa

[[File:55107 1930streaksboulders2.jpg|thumb|500px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

<gallery class="center" widths="380px" heights="360px">

</gallery>

Another thing that causes light and dark patterns is a dust devil. These miniature tornadoes remove the bright dust and make straight and/or curved tracks. They are common especially in areas with much dust cover and at certain times of the day. They have been observed both from orbit and from the ground.<ref>https://www.uahirise.org/ESP_042201_1715</ref> We even have movies of them in action. They can form beautiful scenes. And, the arrangement of the tracks can be different in just a few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">
</gallery>

The atmosphere of Mars contains a great deal of fine dust. Large dust storms happen just about every Martian year. A year on Mars is about 23 of our months. Dust storms typically occur when it is spring or summer in the southern hemisphere. At that time, Mars is at its closest to the sun. Unlike the Earth, Mars has a very elliptical orbit which brings it much closer to the sun than at other times. This makes for differences in season both in intensity and length. For example the southern summer is much shorter than that of the north. However, the summer season in the southern hemisphere is much more intense.

[[File:Marsorbitsolarsystem.gif|Comparrsion of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle.<ref> https://www.compadre.org/osp/items/detail.cfm?ID=9757</ref> <ref> https://www.compadre.org/osp/items/detail.cfm?ID=7305</ref>]]

Comparison of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle. Mars changes its distances to sun a great deal--this changes makes drastic seasonal changes.

==Dry Ice==

Some of the strangest things on Mars involve dry ice—solid carbon dioxide. The cold conditions on Mars cause much of the carbon dioxide to freeze out of the atmosphere. Both ice caps contain some dry ice. Each year about 25% of the atmosphere freezes out onto the poles. This is so much that the gravity of the planet shifts. <ref>NASA/Goddard Space Flight Center. "New gravity map gives best view yet inside Mars." ScienceDaily. ScienceDaily, 21 March 2016. https://www.sciencedaily.com/releases/2016/03/160321154013.htm.</ref> <ref>Antonio Genova, Sander Goossens, Frank G. Lemoine, Erwan Mazarico, Gregory A. Neumann, David E. Smith, Maria T. Zuber. Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science. Icarus, 2016; 272: 228 DOI: 10.1016/j.icarus.2016.02.05</ref> Winds and weather systems that almost look like the Earth’s are produced by so much dry ice changing to a gas at these times.

[[File:PIA00190-MC-30-MareAustraleRegion-19980605.jpg |right|thumb|px| Region of South Pole with ice cap Southern ice cap is much smaller than the North’s.]]

[[File:Mars NPArea-PIA00161.jpg |left|thumb|px| Spiral troughs in the northern ice cap]]

<gallery class="center" widths="380px" heights="360px">

File:Marscyclone hst.jpg|Cyclone on Mars, as seen by HST
</gallery>

In the winter dry ice accumulates. So, large areas appear white. When things warm up in the spring, the landscape gets many dark spots and areas. <ref>https://mars.jpl.nasa.gov/mgs/msss/camera/images/dune_defrost_6_2001/</ref><ref>SPRING DEFROSTING OF MARTIAN POLAR REGIONS: MARS GLOBAL SURVEYOR MOC AND TES MONITORING OF THE RICHARDSON CRATER DUNE FIELD, 1999–2000. K. S. Edgett, K. D. Supulver, and M. C. Malin, Malin Space Science Systems, P.O. Box 910148, San Diego, CA 92191-0148, USA.</ref> <ref>K.-Michael Aye, K., et al. PROBING THE MARTIAN SOUTH POLAR WINDS BY MAPPING CO2 JET DEPOSITS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2841.pdf</ref> In the past, observers thought that Mars was full of life. They saw the northern ice cap get smaller and smaller. At the same time, they watched the area get darker. They concluded that the darkening was vegetation growing from the water coming out of the ice caps. What was happening was the dry ice was disappearing. Today, we can watch this darkening occur in great detail. <ref>http://www.jpl.nasa.gov/news/news.php?release=2013-034</ref>

<gallery class="center" widths="380px" heights="360px">

43821 2555defrostingdune2.jpg|Defrosting surface Frost is disappearing in patches from a dune and from the surrounding surface. Note: the north side (side near top) has not defrosted because the sun is coming from the other side.

File:ESP 011605 1170defrosting.jpg|Defrosting The dark spots are where the ice has gone. We now can see the underlying dark surface.

</gallery>

In some places, there are many geyser-like eruptions of gas and dark dust.<ref>https://www.uahirise.org/</ref> High pressure gas and dust explode out of the ground. Winds often blow these eruptions into dark plumes. After many observations, scientists concluded that what happens is that a transparent-translucent dry ice slab forms in the winter. With increased sun in the spring, pressure builds up under this slab as light heats cavities under the slab and causes dry ice to turn into a gas. At weak areas in the slab, the gas comes out along with dark dust.<ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> The channels may get dark from the dust and make a pattern that looks like a spider. These patterns are called “spiders.” <ref>http://mars.jpl.nasa.gov/multimedia/images/2016/possible-development-stages-of-martian-spiders</ref> <ref>http://spaceref.com/mars/growth-of-a-martian-trough-network.html</ref> <ref>Benson, M. 2012. Planetfall: New Solar System Visions</ref> <ref>http://www.astrobio.net/topic/solar-system/mars/spiders-invade-mars/</ref> <ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>Portyankina, G., et al. 2017. Present-day erosion of Martian polar terrain by the seasonal CO2 jets. Icarus: 282, 93-103.</ref> The official name for spiders is "araneiforms."<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>

<gallery class="center" widths="380px" heights="360px">

File:Spiders2eruptionlabeled2.jpg|Drawing showing the cause of plumes and spiders. In the spring, sunlight goes through a clear slap of dry ice. It heats up the dark ground. Heat causes dry ice to turn into a gas and pressurize. When pressure is great enough a dark plume of carbon dioxide gas and dark dust erupt. Wind will form it into a fan shape plume.

</gallery>

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

<gallery class="center" widths="380px" heights="360px">

ESP 048845 1010spiders.jpg|Wide view of crater that contains examples of spiders
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
</gallery>

Around the southern cap, dry ice makes round, low areas that look like Swiss cheese. <ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data
Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> So, it is called “Swiss cheese terrain.” The roundness of the pits is believed to be related to the low angle of the sun.<ref>Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

[[File:South Pole Terrain.jpg|600pxr|HiRISE view of South Pole Terrain.]]
HiRISE view of South Pole Terrain.

<gallery class="center" widths="380px" heights="360px">
</gallery>

The ice caps contain a great deal of water ice. The northern cap has a covering of dry ice only 1 meter thick in the winter, but the southern cap always has a coating of dry ice up to 8 meters thick. Large deposits of dry ice are also buried in the water ice of the cap at some locations.

<gallery class="center" widths="380px" heights="360px">
</gallery>

==Gullies==

Since 2000, researchers have been studying gullies that are common in the mid-latitudes on steep slopes. They look like they were carved by liquid water. After many years of observations, it has been concluded that today they are being made by chunks of dry ice sliding down slopes.<ref>Vincendon, M. 2015. JGR:120, 1859–1879.</ref> <ref> Pilorget | first1 = C. | last2 = Forget | first2 = F. | year = 2016 | title = Formation of gullies on Mars by debris flows triggered by CO2 sublimation | url = | journal = Nature Geoscience | volume = 9 | issue = | pages = 65–69 | doi = 10.1038/ngeo2619 | </ref> <ref>Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.</ref> However, some scientists concede that water may have been involved in their formation in the past.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm</ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 047956 1420gullies.jpg|Crater with gullies, as seen by HiRISE under HiWish program
File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
</gallery>

[[File:Gullies near Newton Crater.jpg|600pxr|Gullies near Newton Crater]]
Gullies near Newton Crater

==Other features==

The surface of Mars is very old—billions of years. This is plenty of time for rocks to have broken down into sand. In low places, like crater floors, sand accumulates and makes dunes. Some are quite pretty. And the colors used by NASA make them even more pretty—they can appear blue, purple, green, or turquoise.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:61974 1710dunesrgb2.jpg|Dunes
File:ESP 046378 1415dunefield.jpg|Black and white, wide view of dunes
File:ESP 55095 2170dunes.jpg|Dunes near Sklodowski Crater in North Arabia Terra
</gallery>

Related to dunes are something called transverse aeolian ridges (TAR’s). They look like small dunes. They are often parallel to each other. They generally are in low areas and one of the most common landforms on Mars.<ref>http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1598.pdf|format=PDF|type=conference paper|title=Investigations of transverse aeolian ridges on Mars|first1=Daniel C.|last1=Berman|first2=Matthew R.|last2=Balme|year=2012|publisher=Lunar and Planetary Science Conference</ref> They are mid-way in height between dunes and ripples; they are not well understood.<ref>http://www.uahirise.org/ESP_042625_1655</ref> <ref>Berman, D., et al. 2018. High-resolution investigations of Transverse Aeolian Ridges on Mars: Icarus: 312, 247-266.</ref>

<gallery class="center" widths="380px" heights="360px">

File:64038 2155tarslabeled.jpg|Transverse Aeolian Ridges, as seen by HiRISE under HiWish program

File:ESP 039563 1730tars.jpg|Transverse Aeolian Ridges (TAR’s) between yardangs We do not totally understand these.
File:ESP 042625 1655tars.jpg|Wide view of Transverse Aeolian Ridges (TAR’s) near a channel
</gallery>

Some landscape expressions are mysteries.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>

In rocks of certain ages, often at the bottom of low spots are complex arrangements of ridges.
These are walls of rock.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>

There are different ideas for what caused them. Over 14,000 people from around the world helped map them, so that scientists could better understand them. The team of volunteers found 952 polygonal ridge networks in an area that measures about a fifth of Mars’ total surface area. Some ridges contain clays, so water may have been involved in their formation because clays need water to be formed.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al. 2022. Irregular polygonal ridge networks in ancient Noachian terrain on Mars. Icarus. 374. 114833</ref>

[[File:ESP 036745 1905top.jpg|600pxr|Linear ridge networks]]
Linear ridge networks

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
</gallery>

[[File:Ridgesmappedbycitizens.jpg|600pxr|Map of Linear ridge networks]]

Map of Linear ridge networks

Of eerie beauty are odd arrangements visible on the bottom of the Hellas Impact basin. We are not sure exactly what caused them. They have been called honeycomb terrain or banded terrain.

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Honeycomb terrain on floor of Hellas Basin The exact origin of these shapes is unknown at present.

<gallery class="center" widths="380px" heights="360px">

</gallery>

Mars is one planet that we can see the surface clearly. Its super thin atmosphere (about 1% of the Earth’s) makes it easy to observe. Early telescopes revealed many markings and patterns. As we sent better and better cameras to examine it, more mysteries and more beautiful scenes emerged. We were able to answer many questions, but always more questions arose concerning what we were seeing.

<gallery class="center" widths="380px" heights="360px">

</gallery>

==References==

{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]

*[https://www.youtube.com/watch?v=jcaawA7d0ro Sublimation of Dry Ice]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]

==Recommended reading==

*Head, J., et al. 2023. GEOLOGICAL AND CLIMATE HISTORY OF MARS: IDENTIFICATION OF POTENTIAL WARM AND
WET CLIMATE ‘FALSE POSITIVES’. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1731.pdf
*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

Martian gullies

2023-03-20T22:25:56Z

Suitupandshowup: /* Dry ice makes gullies today */ added ref

Martian gullies are narrow channels and their associated downslope sediment deposits, they are found on steep slopes on Mars. They were first discovered on Mars Global Surveyor images especially on the walls of craters. Usually, each gully has a ‘‘alcove’’ at its head, a fan-shaped ''apron'' at its base, and a single thread of incised ''channel'' connecting the two. The whole gully resembles an hourglass.
<ref name="Malin, M. 2000"> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910| </ref>
They are estimated to be relatively young because they have few, if any, craters.

[[File:50858 1435gullies.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

Most gullies appear 30 degrees poleward in each hemisphere, with greater numbers in the southern hemisphere. Some studies have found that gullies occur on slopes that face all directions.

<ref>cite journal|last1=Edgett|first1=K.|display-authors=etal|date=2003|title=Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit|journal=Lunar Planet. Sci.|volume=34|at=Abstract 1038|url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf|bibcode=2003LPI....34.1038E</ref>
Others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S.<ref>Dickson, J; Head, J; Kreslavsky, M (2007). "Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography" (PDF). Icarus. 188: 315–323.</ref>
Although thousands of gullies have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia.
<ref>name="2007Icar..188..324H">last1=Heldmann|first1=J|last2=Carlsson|first2=E|last3=Johansson|first3=H|last4=Mellon|first4=M|last5=Toon|first5=O|title=Observations of martian gullies and constraints on potential formation mechanisms. The northern hemisphere|journal=Icarus|volume=188|pages=324–344|date=2007|doi=10.1016/j.icarus.2006.</ref>
In the south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra, and along the walls of the Hellas outflow channels.<ref>Heldmann, J; Carlsson, E; Johansson, H; Mellon, M; Toon, O (2007). "Observations of martian gullies and constraints on potential formation mechanismsII. The northern hemisphere". Icarus. 188: 324–344.</ref>
A recent study examined 54,040 CTX images that covered 85% of the Martian surface found 4861 separate gullied landforms (e.g., individual craters, mounds, valleys, etc.), which totaled tens of thousands of individual gullies. This number may represent a fairly accurate census of gullies since it is estimated that CTX can resolve 95% of gullies.
<ref>Harrison, T., G. Osinski1, and L. Tornabene. 2014. GLOBAL DOCUMENTATION OF GULLIES WITH THE MARS RECONNAISSANCE ORBITER CONTEXT CAMERA (CTX) AND IMPLICATIONS FOR THEIR FORMATION. 45th Lunar and Planetary Science Conference. pdf</ref>

On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers think (especially when they were first discovered) that the processes carving gullies involve liquid water. Because the gullies are so young, this would suggest that liquid water has been present on Mars in its very recent geological past, consequently adding to the possibility of living forms on the present surface.

After being discovered, many hypotheses were put forward to explain the gullies.
<ref>http://www.psrd.hawaii.edu/Aug03/MartianGullies.html</ref>
However, as in the usual progression of science, some ideas came to be more plausible than others when more observations were made, when other instruments were used, and when statistical analysis was employed. Even though some gullies resembled debris flows on Earth, it was found that many gullies were on slopes that were not steep enough for typical debris flows. Although it was suggested that liquid carbon dioxide could cause gullies, calculations showed that the pressure and temperatures were not suitable for liquid carbon dioxide.
<ref>Musselwhite, C., et al. 2001. Liquid CO2 Breakout and the formation of recent small gullies on Mars. Lunar and Planetary Science XXXII. 1030.pdf</ref> <ref> Stewart, S. 2001. Lunar and Planetary Science XXXII. 17820.pdf</ref>
<ref>Stewart, S. 2001. Surface runoff features on Mars: Testing the carbon dioxide formation hypothesis. Lunar and Planetary Science XXXII. 1780.pdf</ref>
Moreover, the winding shape of the gullies suggested that the flows were slower than what would be produced in debris flows or eruptions of liquid carbon dioxide. Liquid carbon dioxide would explode out of the ground in the thin Martian atmosphere. Because the liquid carbon dioxide would throw material over 100 meters, the channels should be discontinuous, but they are not.
<ref name="Heldmann 2004">last1=Heldmann|first1=J|title=Observations of martian gullies and constraints on potential formation mechanisms|journal=Icarus|volume=168|pages=285–304|date=2004|doi=10.1016/j.icarus.2003.11.024|</ref>
Eventually, most hypotheses focused on liquid water coming from an aquifer, from melting at the base of old glaciers (or snowpacks), or from the melting of ice in the ground when the climate was warmer.<ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/3060.pdf</ref> <ref>Khuller1, A., P. R. Christensen. 2019. EVIDENCE OF WATER-RICH SNOW DEPOSITS WITHIN MARTIAN GULLIES. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3060.pdf</ref> <ref> Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304. </ref> <ref>Forget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK.</ref>
Close-up images with HiRISE showed details that support the idea that a fluid was involved. Images show that channels formed at various times--smaller channels were found in larger valleys, suggesting that after a valley formed another formed at a later time. Many cases showed channels took different paths at different times. Streamlined forms like teardrop-shaped islands were common in some channels. On the Earth, running water is the cause of streamlined forms.<ref>Head, J., D. Marchant, M. Kreslavsky. 2008. Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin. PNAS: 105 (36), 13258–13263.</ref>

<gallery class="center" widths="380px" heights="360px">
File:26420gulliesclose.jpg|Streamlined features in gullies thought to have formed by running water
File:Multiple channels in 21461.jpg| Smaller gullies inside larger ones Water may have flowed in these gullies more than once.
File:ESP 039793 1385channeldetails.jpg|Close-up of gullies in crater showing channels within larger valleys and curves in channels. These characteristics suggest they were made by flowing water. Location is Eridania quadrangle.
</gallery>

The following group of pictures of gullies illustrates some of the shapes that lead researchers to think that water was involved in creating at least some of the gullies.

<gallery class="center" widths="380px" heights="360px">
File:45752 1410gullies.jpg|Gullies The location is the Phaethontis quadrangle.
File:46386 1420gullies.jpg|Gullies, as seen by HiRISE Location is the Phaethontis quadrangle.
File:ESP 037506 2285gullychannelsclose.jpg|Close-up of gully channels, as seen by HiRISE under HiWish program. This image shows many streamlined forms and some benches along a channel. These features suggest formation by running water. Benches are usually formed when the water level goes down a bit and stays at that level for a time. Location is the Mare Acidalium quadrangle.
</gallery>

===Aquifers===

One of the earliest ideas attempting to explain gully formation was that water came out of aquifers. Most of the gully alcove heads occur at the same level, just as one would expect if water came out of aquifers. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies. Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin.
<ref > Heldmann, J (2004). "Observations of martian gullies and constraints on potential formation mechanisms". Icarus. 168: 285–304.</ref>
One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers.
<ref>http://www.space.com/scienceastronomy/mars_aquifer_041112.html Mars Gullies Likely Formed By Underground Aquifers. Leonard David, 12 November 2004 (Space.com)</ref>
Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.
<ref>Harris, A and E. Tuttle. 1990. Geology of National Parks. Kendall/Hunt Publishing Company. Dubuque, Iowa</ref>
However, the idea that aquifers formed the gullies does not explain the ones found on isolated peaks, like knobs and the central peaks of craters. Also, one kind of gully seems to be present on sand dunes.
<ref>Reiss, D, R. Jaumann. 2003. Recent debris flows on Mars: Seasonal observations of the Russell Crater dune field. Geophysical Research letters: 30, 54</ref>

[[File:ESP 051770 1345dunegullies.jpg |thumb|300px|left| Gullies on dunes Some gullies on sand dunes appear each Martian year. It is difficult to conceive of an aquifer causing gullies on dunes.]]

[[File:ESP 054026 1300gulliesdunes.jpg|thumb|300px|center|Gullies on Dunes in Matara Crater, as seen by HiRISE]]

Aquifers need a wide collecting area which is not present on sand dunes or on isolated slopes. Even though most of the original gullies that were seen seemed to come from the same layer in the slope, some exceptions to this pattern have been found.
<ref>Foget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK</ref> Examples of gullies coming from different levels are shown below in the image of Lohse Crater and the image of gullies in Ross Crater.

<gallery class="center" widths="380px" heights="360px">
File:Wide view of gully on hill.jpg|CTX image of the next image showing a wide view of the area. Since the hill is isolated it would be difficult for an aquifer to develop. Rectangle shows the approximate location of the next image.
File:Gully on mound.JPG|Gully on mound as seen by Mars Global Surveyor, under the MOC Public Targeting Program. Images of gullies on isolated peaks, like this one, are difficult to explain with the theory of water coming from aquifers because aquifers need large collecting areas.
File:47528 1355gulliesmound.jpg|Gullies on 2 sides of a mound. This arrangement is difficult to explain with aquifers.
File:ESP 039621 1315gullies2levels.jpg|Gullies in two levels of a crater wall, as seen by HiRISE under HiWish program. Gullies at two levels suggest they were not made with an aquifer, as was first suggested. Location is Phaethontis quadrangle.
</gallery>

===Snowpacks===

The main basis for the snowpack hypothesis for gully formation is that much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.
<ref>last1=Malin|first1=Michael C.|last2=Edgett|first2=Kenneth S.|title=Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission|journal=Journal of Geophysical Research|volume=106|pages=23429–23570|date=2001|doi=10.1029/2000JE001455</ref> <ref>|pmid=11473309|last1=Mustard|first1=JF|date=2001|pages=411–4|issue=6845|last2=Cooper|volume=412|first2=CD|journal=Nature|last3=Rifkin|first3=MK|title=Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice.|url=http://www.planetary.brown.edu/pdfs/2610.pdf</ref> <ref>last1=Carr|first1=Michael H.|title=Mars Global Surveyor observations of Martian fretted terrain|journal=Journal of Geophysical Research|volume=106|pages=23571–23595|date=2001|doi=10.1029/2000JE001316|</ref>
This ice-rich mantle, a few yards thick, soothes the land. The mantle may be like a glacier, and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.<ref>http://www.nbcnews.com/id/15702457/ns/technology_and_science-space/t/martian-gullies-could-be-scientific-gold-mines/#.WxVAOUxFzIU</ref> <ref>Head, JW; Marchant, DR; Kreslavsky, MA (2008). "Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin". PNAS. 105 (36): 13258–63.</ref>
Indeed, calculations show that a third of a mm of runoff can be produced through the melting of a dusty snowpack each day for 50 days of each Martian year even under current conditions.
<ref>last1=Clow|first1=G|title=Generation of liquid water on Mars through the melting of a dusty snowpack|journal=Icarus|volume=72|pages=93–127|date=1987|</ref>
Because there are few craters on this mantle, the mantle is relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE.
<ref>last1=Christensen|first1=PR|title=Formation of recent martian gullies through melting of extensive water-rich snow deposits.|journal=Nature|volume=422|issue=6927|pages=45–8|date=2003|pmid=12594459|doi=10.1038/nature01436 </ref>
The ice-rich mantle may be the result of climate changes.
<ref>http://news.nationalgeographic.com/news/2008/03/080319-mars-gullies_2.html Melting Snow Created Mars Gullies, Expert Says</ref>
Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed with dust. This movement of water could last for several thousand years and create a snow layer of up to around 10 meters thick.
<ref name="ReferenceA">last1=Jakosky|first1=Bruce M.|last2=Carr|first2=Michael H.|title=Possible precipitation of ice at low latitudes of Mars during periods of high obliquity|journal=Nature|volume=315|pages=559–561|date=1985|doi=10.1038/315559a0|issue=6020</ref> <ref>|last1=Jakosky|first1=Bruce M.|last2=Henderson|first2=Bradley G.|last3=Mellon|first3=Michael T.|title=Chaotic obliquity and the nature of the Martian climate|journal=Journal of Geophysical Research|volume=100|pages=1579–1584|date=1995|</ref>
When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice.

<gallery class="center" widths="380px" heights="360px">
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program
46444 2225mantle.jpg|Mantle
</gallery>

<ref>author=MLA NASA/Jet Propulsion Laboratory|date=December 18, 2003|title=Mars May Be Emerging From An Ice Age|work=ScienceDaily|accessdate=February 19, 2009|url=https://www.sciencedaily.com/releases/2003/12/</ref>
When the slopes, orientations, and elevations of thousands of gullies were compared, clear patterns emerged from the data. Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow.
<ref name="2007Icar..188..315D">last1=Dickson|first1=J|last2=Head|first2=J|last3=Kreslavsky|first3=M|title=Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography|doi=10.1016/j.icarus.2006.11.020|url=http://www.planetary.brown.edu/pdfs/3138.pdf|date=2007|pages=315–323|volume=188|journal=Icarus|format=PDF</ref>
Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude. For example, Thaumasia quadrangle is heavily cratered with many steep slopes. It is in the right latitude range, but its altitude is so high that there is not enough pressure to keep ice from sublimating (going directly from a solid to a gas); hence it does not have gullies.
<ref>pages=26695–26712|date=2000|doi=10.1029/2000JE001259|last1=Kreslavsky|volume=105|first1=Mikhail A.|journal=Journal of Geophysical Research|last2=Head|first2=James W.|title=Kilometer-scale roughness of Mars: Results from MOLA data analysis|url=http://www.planetary.brown.edu/pdfs/2447.pdf|</ref> <ref>last1=Hecht|first1=M|title=Metastability of liquid water on Mars|pages=373–386|date=2002|volume=156|doi=10.1006/icar.2001.6794|journal=Icarus|url=http://www.geo.brown.edu/geocourses/geo292/papers/Hecht2002.pdf|format=PDF|</ref>
In summary, it is now estimated that during periods of high obliquity, the ice caps will melt causing higher temperature, pressure, and moisture. The moisture will then accumulate as snow in midlatitudes, especially in the more shaded area. At a certain time of the year, sunlight will melt snow with the resulting water producing gullies.

A related idea is that buried snow deposits may be uncovered, melt, and help to form gullies. Evidence for snow deposits being exposed has been observed and reported.</ref>Kuller, A., P. Christensen. 2019. EVIDENCE OF WATER-RICH SNOW DEPOSITS WITHIN MARTIAN GULLIES. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132). 3060.pdf</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2019/pdf/3060.pdf</ref>

===Melting of ground ice===

The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast.
<ref>last1=Peulvast|first1=J.P.|date=1988|title=Mouvements verticaux et genèse du bourrelet Est-groenlandais. dans la région de Scoresby Sund|journal=Physio Géo|volume=18|pages=87–105|language=French </ref>
Since the gullies occur on steep slopes only a small decrease of the shear strength of the soil particles is needed to begin the flow. Small amounts of liquid water from melted ground ice could be enough.
<ref>author1=Jouannic G. |author2=J. Gargani |author3=S. Conway |author4=F. Costard |author5=M. Balme |author6=M. Patel |author7=M. Massé |author8=C. Marmo |author9=V. Jomelli |author10=G. Ori |date=2015|title= Laboratory simulation of debris flows over a sand dune : Insights into gully-formation (Mars)|journal=Geomorphology|volume=231|pages=101–115|url=http://www.sciencedirect.com/science/article/pii/S0169555X14005972|doi=10.1016/j.geomorph.2014.12.007|</ref> <ref>last1=Costard|first1=F.|display-authors=etal|date=2001|title=Debris Flows on Mars: Analogy with Terrestrial Periglacial Environment and Climatic Implications|journal=Lunar and Planetary Science|volume=XXXII||url=http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1534.pdf|format=PDF </ref> <ref>{{cite web |url=http://www.spaceref.com/16090/news/viewpr.html?pid=7124 |title=Archived copy |accessdate=2011-03-10 |deadurl=yes |archiveurl=https://archive.is/20120910131532/http://www.spaceref.com/16090/news/viewpr.html?pid=7124 |</ref>

==Dry ice makes gullies today==

[[File:ESP 032011 1425newgullies.jpg|600pxr|Changes in gullies, as seen by HiRISE This shows that gullies are forming today, even though liquid water can not exist on the surface today.]]

Changes in gullies, as seen by HiRISE This shows that gullies are forming today, even though liquid water can not exist on the surface today

As soon as gullies were discovered,
<ref name="Malin, M. 2000"> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2000 | title = Evidence for recent groundwater seepage and surface runoff on Mars | url = | journal = Science | volume = 288 | issue = | pages = 2330–2335 | doi=10.1126/science.288.5475.2330 | pmid=10875910| </ref>
researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found.
<ref> last1 = Malin | first1 = M. | last2 = Edgett | first2 = K. | last3 = Posiolova | first3 = L. | last4 = McColley | first4 = S. | last5 = Dobrea | first5 = E. | year = 2006 | title = Present-day impact cratering rate and contemporary gully activity on Mars | url = | journal = Science | volume = 314 | issue = | pages = 1573–1577 | doi=10.1126/science.1135156 | pmid=17158321| </ref> Liquid water can not exist on Mars today to carve gullies, yet images showed that new gullies were forming.<ref>https://www.uahirise.org/ESP_039701_1095</ref> <ref>https://www.uahirise.org/ESP_032011_1425</ref> There must be other mechanisms going on today.
Later, analysis revealed that the changes could have occurred by dry granular flows rather than being driven by flowing water.
<ref>| last1 = Kolb | display-authors = et al. | year = 2010 | title = Investigating gully flow emplacement mechanisms using apex slopes | doi = 10.1016/j.icarus.2010.01.007 | journal = Icarus | volume = 208 | issue = | pages = 132–142 | </ref> <ref> last1 = McEwen | first1 = A. | display-authors = et al. | year = 2007 | title = A closer look at water-related geological activity on Mars | url = | journal = Science | volume = 317 | issue = | pages = 1706–1708 | </ref> <ref>| last1 = Pelletier | first1 = J. | display-authors = et al. | year = 2008 | title = Recent bright gully deposits on Mars wet or dry flow? | url = | journal = Geology | volume = 36 | issue = | pages = 211–214 | doi=10.1130/g24346a.1| </ref>
Changes were found in Gasa Crater and other craters.
<ref>NASA/Jet Propulsion Laboratory. "NASA orbiter finds new gully channel on Mars." ScienceDaily. ScienceDaily, 22 March 2014. www.sciencedaily.com/releases/2014/03/140322094409.htm </ref>
Channels widened by 0.5 to 1 m; meter sized boulders moved; and hundreds of cubic meters of material moved. It was calculated that gullies could be formed under present conditions with as little as 1 event in 50–500 years. Although today there is little liquid water, present geological/climatic processes could still form gullies.
<ref>Dundas, C., S.
Diniega, and A. McEwen. 2014. LONG-TERM MONITORING OF MARTIAN GULLY ACTIVITY WITH HIRISE. 45th Lunar and Planetary Science Conference. 2204.pdf</ref>
Sinuous channels which were thought to need liquid water for their formation have even been seen to form over just a few years when liquid water cannot exist.
<ref>Dundas, C. et al. 2016. HOW WET IS RECENT MARS? INSIGHTS FROM GULLIES AND RSL. 47th Lunar and Planetary Science Conference (2016) 2327.pdf.</ref>
The timing of gully activity is seasonal and happens during the period when seasonal frost is present and defrosting.
<ref>Vincendon, M. 2015. JGR:120, 1859–1879.</ref>
Observations with HiRISE show widespread activity in southern hemisphere gullies, especially in those that appear fresh. Significant channel incision and large-scale mass movements have been seen.
Neither large amounts of water or great changes in climate were not needed. But, some gullies in the past may have been aided by weather changes that involved larger amounts of water, perhaps from melted snow.
<ref>Dundas, C., S. Diniega, C. Hansen, S. Byrne, A. McEwen. 2012. Seasonal activity and morphological changes in martian gullies. Icarus, 220. 124–143.</ref>
Repeated observations, showed that changes occur in the winter and spring. Studies with the High Resolution Imaging Science Experiment (HiRISE) camera on MRO examined gullies at 356 sites, starting in 2006. Thirty-eight of the sites showed active gully formation. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon dioxide frost and temperatures that would not have allowed for liquid water. <ref>http://www.jpl.nasa.gov/news/news.php?release=2014-226</ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158/</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032078_1420</ref> <ref>http://www.space.com/26534-mars-gullies-dry-ice.html</ref> Some scientists tended to suspect that gullies were formed from carbon dioxide ice (dry ice). When dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes. In some years frost, perhaps as thick as 1 meter, triggers avalanches. This frost contains mostly dry ice, but also has tiny amounts of water ice.
<ref>http://spaceref.com/mars/frosty-gullies-on-mars.html</ref>
These observations support a model in which currently active gully formation is driven mainly by seasonal CO2 frost.
<ref>Dundas, C., S. Diniega, A. McEwen. 2015. Long-term monitoring of martian gully formation and evolution with MRO/HiRISE. Icarus: 251, 244–263</ref>
<ref> last1 = Raack | first1 = J. | display-authors = etal | year = 2015 | title = Present-day seasonal gully activity in a south polar pit (Sisyphi Cavi) on Mars| url = | journal = Icarus | volume = 251 | issue = | pages = 226–243 | doi=10.1016/j.icarus.2014.03.040 | </ref>
Simulations described in a 2015 conference, show that high pressure CO2 gas trapping in the subsurface can cause debris flows.
<ref>http://www.uahirise.org/ESP_044327_1375</ref>
The conditions that can lead to this are found in latitudes where gullies occur.<ref>C. Pilorget, C., F. Forget. 2015. "CO2 Driven Formation of Gullies on Mars." 46th Lunar and Planetary Science Conference. 2471.pdf</ref>
This research was described in a later article entitled, "Formation of gullies on Mars by debris flows triggered by CO2 sublimation."
<ref>| last1 = Pilorget | first1 = C. | last2 = Forget | first2 = F. | year = 2016 | title = Formation of gullies on Mars by debris flows triggered by CO2 sublimation | url = | journal = Nature Geoscience | volume = 9 | issue = | pages = 65–69 | doi = 10.1038/ngeo2619 | </ref>
In the model, CO2 ice accumulates in the cold winter.
<ref>Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.</ref>
It piles up on a frozen permafrost layer that consists of ice-cemented dirt. When the higher intensity sunlight of spring begins, light penetrates the translucent dry ice layer, consequently warming the ground. The CO2 ice absorbs heat and sublimates—that is changes directly from a solid to a gas. This gas builds up pressure because it is trapped between the ice and the frozen ground. Eventually, pressure builds up enough to explode through the ice taking with it soil particles. The dirt particles mix with the pressurized gas and act as a fluid that can flow down the slope and carve gullies.
On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by the seasonal freezing of [[carbon dioxide]] (CO2 ice or 'dry ice'), and not by that of liquid water as thought earlier. So, the current thought is that gullies can be formed today by chunks of dry ice moving down steep slopes today.<ref> Raack, J., et al. 2020. Present-day gully activity in Sisyphi Cavi, Mars – Flow-like features and block movements. Icarus. 350. https://doi.org/10.1016/j.icarus.2020.113899. </ref> Perhaps in the past, water was also involved.<ref name="NASA-20140710">last=Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |date=July 10, 2014 |work=NASA</ref>
<ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm </ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref> <ref>https://www.uahirise.org/ESP_067299_1435</ref> <ref>Dickson, J., et al. 2021. THE ELEVATION DISTRIBUTION OF MID-LATITUDE GULLIES ON MARS AS A TEST OF CO2 AND
H2O FORMATION AND MODIFICATION PROCESSES. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2426.pdf</ref>

In summary of our present understanding of gullies it can be said: A number of studies have demonstrated that gullies are being modified on present day Mars. <ref>C.M. Dundas, A.S. McEwen, S. Diniega, C.J. Hansen, S. Byrne, J.N. McElwaine. The formation of gullies on Mars today. Geol. Soc. London Spec. Publ., 467 (2019), pp. 67-94, 10.1144/SP467.5</ref> <ref>C.M. Dundas, S. Diniega, C.J. Hansen, S. Byrne, A.S. McEwen. Seasonal activity and morphological changes in Martian gullies. Icarus, 220 (2012), pp. 124-143, 10.1016/j.icarus.2012.04.005 </ref> <ref>.M. Dundas, S. Diniega, A.S. McEwen. Long-term monitoring of Martian gully formation and evolution with MRO/HiRISE. Icarus, 251 (2015), pp. 244-263, 10.1016/j.icarus.2014.05.013</ref> <ref>J. Raack, S.J. Conway, T. Heyer, V.T. Bickel, M. Philippe, H. Hiesinger, A. Johnsson, M. Massé. Present-day gully activity in Sisyphi Cavi, Mars - flow-like features and block movements. Icarus, 350 (2020), 10.1016/j.icarus.2020.113899. article #113899</Ref> Today, liquid water cannot exist on the Red planet because the both the pressure and the temperature is too low. Further evidence that water is not involved is that minerals are not changed by gully formation.<ref>J.I. Núñez, O.S. Barnouin, S.L. Murchie, F.P. Seelos, J.A. McGovern, K.D. Seelos, D.L. Buczkowski. New insights into gully formation on Mars: constraints from composition as seen by MRO/CRISM. Geophys. Res. Lett., 43 (2016), pp. 8893-8902, 10.1002/2016GL068956</ref> For many years, many believed that gullies had to be made with liquid water. So, researchers have proposed other mechanisms that could account for gully formation without liquid water.<ref>S.J. Conway, T. de Haas, T.N. Harrison. Martian gullies: a comprehensive review of observations, mechanisms and insights from Earth analogues. Geol. Soc. London Spec. Publ., 467 (2019), pp. 7-66, 10.1144/SP467.14</ref> Most involve dry ice (solid carbon dioxide) accumulating during cold seasons and then changing to a gas in the spring. The gas coming off could start material moving down slopes. The gas mixed with sand and other debris could act like water to erode channels. Also, pieces of dry ice could easily side down due to the lubricating effect of gas coming off the dry ice. However, one wonders if these processes could account for the formation of all the gullies. Maybe, liquid water was sometimes necessary, especially to move large boulders. A study of over 700 sites, published in 2022 in Icarus, concluded that liquid water would not have been needed. During the duration of the study many large boulders were moved—one being 5 meters across. Many types of changes were seen in gullies. Some channels were extended, new channels were formed, and other channels were filled with new debris.<ref> Dundas, C., et al. 2022. Martian gully activity and the gully sediment transport system. Icarus. (in press) </ref> <ref>https://www.sciencedirect.com/science/article/pii/S0019103522002408#bb0145</ref> Perhaps, some water was involved in the past, but all the gullies seen today could have been made without water.

In support of water being involved is the fact that many gully alcoves have a greater volume than the aprons. The material that was in the alcove may have contained much water ice that disappeared into the atmosphere.<ref>Gulick, V. and N. Glines. 2021. STUDIES OF MARTIAN GULLY SYSTEMS AND THEIR POTENTIAL PALEOENVIRONMENTAL
SETTINGS. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 2773.pdf.</ref> <ref>Gulick et al. 2017 LPSC #1970</ref> Addition evidence that water is involved is that some gullies occur on slopes that are not steep enough for a dry flow, but would be steep enough if water was involved.<ref>Huang, R., et al. 2021. SLOPE ANALYSIS OF MARTIAN GULLIES IN THREE HIGH-NORTHERN LATITUDE CRATERS. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 2625.pdf.</ref> <ref> Huang, R.,
and V. Gulick. 2023. MORPHOLOGIC ANALYSIS OF MARTIAN GULLIES IN FOUR HIGH-NORTHERN LATITUDE
CRATERS. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1863.pdf.</ref>

==References==

{{Reflist|colwidth=30em}}

==See also==

*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Martian features that are signs of water ice]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]
*[[Water]]
*[[What Mars Actually Looks Like!]]

==External links==
* [[https://www.youtube.com/watch?v=mNXBfz1iVzc]] Video demonstrates how dry ice can form gullies on dunes
*[[https://www.youtube.com/watch?v=B1UU8XSMHmM Pictures of gullies on dunes]]
*[[https://www.youtube.com/watch?v=jZpJqlzCRpw Demonstration of dry ice moving down dune ]]
*https://www.hou.usra.edu/meetings/lpsc2022/pdf/1928.pdf Map of gullies on Mars

Dark slope streaks

2023-03-20T21:29:17Z

Suitupandshowup: /* Other slope features */ added ref

[[File:ESP 061648 1895streaks.jpg|600pxr|Dark slope streaks, as seen by HiRISE.]]
Dark slope streaks, as seen by HiRISE

[[File:Fan-shaped Streaks ESP 012410 1835cropped.jpg|300px|right|Dark slope streaks, as seen by HiRISE]]
Dark slope streaks are found on Mars on dust-covered slopes often near the equator; they are believed to be avalanches involving bright Martian dust moving down slope and exposing the dark underlying rock.

==Appearance==

Dark slope streaks are found on dust-covered slopes, particular near the equator.<ref name="Chuang10">Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> They have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>

The streaks start out only about 10% darker than their surroundings.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> Many images of the streaks have been post-processed to bring out more detail and appear much darker. Over time these streaks tend to get lighter as the brighter Martian dust settles from the atmosphere. The darker ones are the newest.

Typically, streaks begin at a small point high on a steep slope, such as a crater wall.<ref name="Schorghofer02">Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> And then they greatly widen and sometimes divide into finger-like extensions (digitation). Obstacles, such as boulders, may cause an individual streak to split into two separate streaks or eventually form a braided (anastomosing) pattern.<ref>Chuang, F.C. et al. 2007. HiRISE Observations of Slope Streaks on Mars. Geophys. Res. Lett., 34 L20204.</ref> Slopes can change their direction.<ref>https://www.uahirise.org/ESP_021976_2055</ref> Many have a fan shape. <ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

Streaks may be hundreds of meters long with a width of 20 to 200 meters.<ref> http://viewer.mars.asu.edu/planetview/inst/moc/M1600596#P=M1600596&T=2</ref> Indeed, some can be over 2 kilometers long.
<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. 2010. Modification of Martian Slope Streaks by Eolian Processes. Icarus, 205 154–164.</ref>
<ref>Baratoux, D. et al. 2006. The Role of the Wind-Transported Dust in Slope Streaks Activity: Evidence from the HRSC Data. Icarus, 183 30–45.</ref>

<gallery class="center" widths="380px" heights="360px">
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks

File:55480 2060streaksobstacles.jpg|Close view of streak showing boulders causing streak to divide
</gallery>

[[File:55107 1930streaksclose.jpg|center|thumb|400px|Streak being affected by boulders. Arrows indicate boulders and resulting effect on streak.]]

[[File:70288 1960craterstreaks.jpg|center|thumb|400px|Dark slope streaks in crater, as seen by HiRISE, under HiWish program]]

==How long do they last?==

Thanks to the many excellent cameras that we have placed in orbit over many decades, we have a history of how the Martian surface changes. Dark slope streaks are some of the most changing parts of Mars. They were discovered in Viking Orbiter pictures from the 1970.<ref name="Morris82">Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. ''J. Geophys. Res.,'' '''87'''(B2), 1164–1178.</ref> <ref name="Ferguson84">Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in ''Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246,'' pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.</ref> When images from Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft are compared, the life history of streaks can be precisely determined.<ref>Sullivan, R. et al. (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633. </ref> <ref name="Chuang07">Chuang, F.C. et al. 2007. HiRISE Observations of Slope Streaks on Mars. 'Geophys. Res. Lett. 34 L20204.</ref> <ref>Dundas, C. 2018. HIRISE OBSERVATIONS OF NEW MARTIAN SLOPE STREAKS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2026.pdf</ref> <ref>Malin, M.C.; Edgett, K.S. (2001). Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res., 106(E10), 23,429–23,570.</ref> <ref>Edgett, K.S.; Malin, M.C.; Sullivan, R.J.; Thomas, P.; Veverka, J. (2000). Dynamic Mars: New Dark Slope Streaks Observed on Annual and Decadal Time Scales. 31st Lunar and Planetary Science Conference, Abstract #1058. http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1058.pdf.</ref>

One analysis concluded that 70 streaks per day may form on the planet. The research team compared overlapping images from Mars Global Surveyor Mars Orbiter Camera that were spaced days to years apart. <ref>Aharonson, O.; Schorghofer, N.; Gerstell, M.F. (2003). Slope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123. </ref>
Dark slope streaks are constantly forming and fading. The darker ones are the youngest. Fading is accomplished by settling of bright dust in the Martian atmosphere. When researches looked at a small area (Lycus Sulci) on Mars with both Viking images and recent CTX images from the Mars Reconnaissance Orbiter, they found that the ones seen in Viking photos were gone, however, new streaks have taken their place. Their calculations indicated that slope streaks last about 40 years <ref>Bergonio, J., K. Rottas, and N. Schorghofer. 2013. Properties of martian slope streak populations: 225. Icarus: 194-199.</ref>

It is believed that during Mars' global dust storms many - perhaps most - streaks and other features are erased during these occosional occurences.<ref>Aharonson, O.; Schorghofer, N.; Gerstell, M.F. 2003. S lope Streak Formation and Dust Deposition Rates on Mars. J. Geophys. Res., 108(E12), 5138, doi:10.1029/2003JE002123.</ref> <ref>Schorghofer, Aharonson, O.; Gerstell, M.F.; Tatsumi, L. 2007. Three Decades of Slope Streak Activity on Mars. Icarus: 191, 132–140. doi:10.1016/j.icarus.2007.04.026.</ref>

[[File:New Streaks Formed PIA02379.jpg|left|thumb|400px|New slope streaks formed near Apollinaris Mons between February 1998 and November 1999, as seen by Mars Orbital Camera (MOC).]]

[[File:23677streakslabeled.jpg|center|thumb|400px|Young and old dark slope streaks with origins labeled.]]

==What causes dark slope streaks?==

Although many ideas have been put forward to explain slope streaks, the general opinion today is that they are simply avalanches of darker colored dust.<ref>https://www.uahirise.org/hipod/ESP_022991_2070</ref> <ref>https://www.uahirise.org/PSP_009192_1890</ref> <ref>Treiman, A.H.; Louge, M.Y. (2004). Martian Slope Streaks and Gullies: Origins as Dry Granular Flows. 35th Lunar and Planetary Science Conference, Abstract #1323. http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1323.pdf</ref> Nearly all of Mars is covered with a thin, bright dust. On steep slopes this layer of dust can move away and reveal a dark surface. The dark volcanic rock basalt lies under the lighter-toned dust which falls out of the atmosphere.
With the long term observations from orbit, researchers have noticed that strikes by meteorites can start the process of slope formation.<ref>http://www.uahirise.org/epo/nuggets/dust-avalanche.pdf</ref> <ref>https://hirise.lpl.arizona.edu/ESP_054066_1920</ref> Moreover, even the air blast from an oncoming strike can trigger clusters of slopes to form.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. 2012. Impact air blast triggers dust avalanches on Mars Icarus: 217 (1) 194 doi:10.1016/j.icarus.2011.10.026</ref>

Although event like meteorite impact nearby can trigger the formation of streaks, surface temperature and wind velocity may be connected to dark slope streak formation. This conclusion was described in a recent article in the journal Icarus.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref> It has been found that streaks can start when dry ice in the ground turns into a gas. Dry ice turning into a gas can make a wind that disturbs the dust; thus starting it to move down a slope. Dry ice can form under the surface as temperature drops.<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al. 2022. Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks. JGR Planets. Volume127, Issue4. e2021JE006988</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 054066 1920newstreak.jpg|New dark slope streak that was triggered by an impact Location is the Arabia quadrangle
</gallery>

==Other slope features==

[[File:50858 1435gullies.jpg|center|thumb|400px|Image of gullies with the parts "alcove", "channel", and "apron" labelled. Picture was taken by HiRISE under HiWish program.]]

Several features are common on slopes on Mars. The surface of Mars is billions of years old in most
places. Consequently, it has accumulated many steep slopes, especially in craters and canyons. Although streaks, gullies, and recurring slope lineae all occur on slopes, they have different origins.
[[Martian gullies]] show up in certain zones. However, unlike dark slope streaks they go fairly deep into the surface and are not erased by falling dust over time. Their origin is still debated. For over a decade they were believed to be formed by recent, flowing water.
<ref>Malin, M.; Edgett, K. (2000). "Evidence for recent groundwater seepage and surface runoff on Mars". Science. 288: 2330–2335.</ref>
<ref>Luu, K., et al. 2018. GULLY FORMATION ON THE NORTHWESTERN SLOPE OF PALIKIR CRATER, MARS 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2650.pdf</ref>
<ref>Hamid, S., V. Gulick. 2018. GEOMORPHOLOGICAL ANALYSIS OF GULLIES ALONG WESTERN SLOPES OF PALIKIR CRATER. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2644.pdf</ref>
<ref>Tyler Paladin, T., et al. 2018. INSIGHTS INTO THE FORMATION OF GULLIES IN ASIMOV CRATER, MARS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2889.pdf</ref> Now, new observations suggest that gullies are being made today by chunks of dry ice moving down steep slopes in the spring.
<ref>Dundas, C., S. Diniega, A. McEwen. 2015. Long-term monitoring of martian gully formation and evolution with MRO/HiRISE. Icarus: 251, 244–263</ref>
<ref>Fergason, R., C. Dundas, R. Anderson. 2015. IN-DEPTH REGIONAL ASSESSMENT OF THERMOPHYSICAL PROPERTIES OF ACTIVE GULLIES ON MARS. 46th Lunar and Planetary Science Conference. 2009.pdf</ref>
<ref>Dundas, C. et al. 2016. HOW WET IS RECENT MARS? INSIGHTS FROM GULLIES AND RSL. 47th Lunar and Planetary Science Conference (2016) 2327.pdf. </ref>
<ref>Vincendon, M. 2015. Identification of Mars gully activity
types associated with ice composition.JGR:120, 1859–1879. </ref>
<ref>Raack, J.; et al. (2015). "Present-day seasonal gully activity in a south polar pit (Sisyphi Cavi) on Mars". Icarus. 251: 226–243. Bibcode:2015Icar..251..226R. doi:10.1016/j.icarus.2014.03.040. </ref>
<ref>http://www.uahirise.org/ESP_044327_1375</ref>
<ref>C. Pilorget, C., F. Forget. 2015. "CO2 Driven Formation of Gullies on Mars." 46th Lunar and Planetary Science Conference. 2471.pdf</ref>
<ref>Pilorget, C.; Forget, F. (2016). "Formation of gullies on Mars by debris flows triggered by CO2 sublimation". Nature Geoscience. 9: 65–69. Bibcode:2016NatGe...9...65P. </ref>

Gullies and streaks are found in different areas on the planet. While the streaks are towards the equator, gullies are often found in the middle northern and southern hemispheres.

Like gullies and streaks, recurring slope lineae are seen on steep slopes, but they are smaller, more narrow, and straighter. Since they seem to lengthen as the temperature increases, they were believed to be involved with liquid water.
<ref>McEwen, A. et al. 2011. Seasonal Flows on Warm Martian Slopes. Science, 333(6043), 740–743. doi:10.1126/science.1204816 PMID 21817049. http://www.sciencemag.org/content/333/6043/740. </ref>
<ref>Mann, Adam (18 February 2014). "Strange Dark Streaks on Mars Get More and More Mysterious". Wired. Retrieved 18 February 2014. </ref>
<ref>Chang, K. 2011. "Scientists Find Signs Water Is Flowing on Mars," New York Times, August 4, A13. https://www.nytimes.com/2011/08/05/science/space/05mars.html?_r=1&ref=marsplanet. </ref>
<ref>HiRISE website. Seasonal Flows on Warm Martian Slopes. http://hirise.lpl.arizona.edu/sim/science-2011-aug-4.php. </ref>
<ref>McEwen, A. Ojha L.; Dundas C.; Mattson, S.; Byrne S.; Wray J.; Cull S.; Murchie S. 2011. Transient Slope Lineae: Evidence for Summertime Briny Flows on Mars? 42nd Lunar and Planetary Science Conference, Abstract #2314. http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2314.pdf. </ref>
Nevertheless, later studies showed that very little water, if any, could be involved.<ref>Dundas, C., et al. 2017. Granular Flows at Recurring Slope Lineae on Mars Indicate a Limited Role for Liquid Water. Nature Geoscience. Nov. 20. [1].</ref> <ref>Schaefer, E., et al. 2018. A case study of recurring slope lineae (RSL) at Tivat crater: Implications for RSL origins. Icarus: In press. https://doi.org/10.1016/j.icarus.2018.07.014</ref> <ref>https://advances.sciencemag.org/content/7/6/eabe4459</ref> <ref>https://www.livescience.com/mars-mysterious-dark-streaks-landslides.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref> <ref>Mason, D. and
L. Scuderi. 2023. Interweaving RSL on Mars: Do They Support a Wet Hypothesis? 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 1703.pdf</ref> As more and more observations were gathered, researchers leaned more and more to liquid water not being involved with these types of streaks. Since there are more streaks when more dust devils are present, researchers think wind may be involved.<ref>https://www.space.com/mars-dark-streaks-probably-not-water?utm_source=Selligent&utm_medium=email&utm_campaign=SDC_Newsletter&utm_content=SDC_Newsletter+&utm_term=2946561</ref> <ref>McEwen, A., et al. 2021. Mars: Abundant Recurring Slope Lineae (RSL) Following the Planet‐Encircling Dust Event (PEDE) of 2018. JGR Planets</ref>

[[File:Streak Locations PIA09030.jpg|left|400px|Map showing locations of gullies (brown) and streaks (pink)]]

[[File:Oblique View of Warm Season Flows in Newton Crater.jpg|center|thumb|400px|Recurrent slope lineae, as seen by HiRISE]]

==References==
{{reflist}}

==See also==
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Martian gullies]]
*[[What Mars Actually Looks Like! ]]

==External links==

*[[yt:_sUUKcZaTgA|Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]]

*[https://static.uahirise.org/images/2020/details/cut/ESP_063204_1800.gif Looking for Slope Streaks]

[[Category: Geologic Processes]]

Curiosity

2023-03-20T21:21:14Z

Suitupandshowup: /* Minerals and Rocks of Mars */ added ref

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating.
In the future, colonists may be able to use the opal as a source of water. Just two halos that have an area of a square meter could contain one to 1.5 gallons of water in the top foot.<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref> <ref>Gabriel, T., et al. 2022. On an Extensive Late Hydrologic Event in Gale Crater as Indicated by Water-Rich Fracture Halos. JGR Planets. Volume127, Issue12 e2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

[[File:Curiosityripplemarks.jpg|left|thumb|320px| Ripple marks in Gale Crater that show water was there.]]

NASA released a picture in February 2023 that shows strong evidence for water. "This is the best evidence of water and waves that we've seen in the entire mission," said Ashwin Vasavada, Curiosity's project scientist at NASA's Jet Propulsion Laboratory in Southern California. These kind of ripple marks are common on Earth along the seashore or bottom of shallow lakes. In the distant past on Mars, waves on the surface of a shallow lake stirred up sediment at the lake bottom to form rippled textures.<ref> https://www.forbes.com/sites/davidbressan/2023/02/09/nasas-curiosity-rover-finds-first-traces-of-a-fossil-lake-on-mars/?sh=10a253dca82f</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices.<ref>Gasnault, O., et al. 2023. CHEMCAM: ZAPPING MARS FOR 10 YEARS (AND MORE). 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 2076.pdf.</ref> Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

InSight Mission

2023-03-20T19:54:22Z

Suitupandshowup: /* Mission Discoveries */

NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) made a soft landing as planned on November 26, 2018 at 4.502 °N, 135.623 °E. InSight landed in a crater that is 25 meters in diameter Homestead hollow. This crater is filed with sediments from impacts. The sediments have been modified and transported by wind.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

It is the first space robotic explorer to study the inside of Mars: its crust, mantle, and core. It set down at exactly 2:52:59 p.m. EST. We found out about the landing by way of two small experimental Mars Cube One (MarCO) CubeSats. They were launched on the same rocket as InSight and relayed information from the lander. <ref>https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight</ref>
The launch took place with an Atlas V-401 from Vandenberg Air Force Base, California on May 5, 2018 7:05 a.m. ET. It’s main instruments are a seismometer (SEIS), a heat probe, and a radio science instrument (RISE).<ref>https://mars.nasa.gov/insight/spacecraft/instruments/summary/</ref>

See the [[Interior of Mars]] for more information of Mars' structure.

Artist’s conception of Insight lander sitting on Mars with instruments deployed

[[File:PIA22878b-annotatedinsightlanding.jpg |600pxr|Location of Insight]]

The red dot shows where InSight landed. It landed just about in the center of its landing ellipse. The location is in the Elysium quadrangle at about 4.5 N and 135.6 E (224.4 W).

==Spacecraft==

InSight weighs 794 pounds (360 kilograms). It is 19 feet 8 inches (6 meters) with solar panels deployed ("wingspan"), and its deck is 5 feet 1 inch (1.56 meters) in diameter.<ref>https://mars.nasa.gov/insight/spacecraft/about-the-lander/</ref> Since dust covering solar panels is a persistent problem for Mars missions, the solar panels on InSight are about two times larger than necessary.

[[File:ESP 058005 1845-lander-full-res.jpg |right|thumb|320px|InSight sitting on the surface, as seen by HiRISE]]

==Mission Activities==

December 19, 2018, InSight's seismometer was set onto the ground directly in front of the lander, about as far away as the arm can reach ---- 5.367 feet. Principal Investigator Bruce Banerdt, stated "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives." The seismometer allows scientists to peer into the Martian interior by studying ground motion — also known as marsquakes. Each marsquake acts as a kind of flashbulb that illuminates the structure of the planet's interior. By studying how seismic waves pass through the layers of the planet, scientists can deduce the depth and composition of these layers.<ref>https://mars.nasa.gov/news/8402/nasas-insight-places-first-instrument-on-mars/?site=insight</ref> InSight's seismometer is so sensitive that if Mars had an atmosphere, and a butterfly landed on the seismometer it's vibrations would be detected. It can detect ground motion that is only half the width of a hydrogen atom.

[[File:22280 PIA22959windshield.jpg|left|thumb|320px|InSights's seismometer with wind cover on the Martian surface.]]

[[File:PIA23045 hiresmole.jpg|right|thumb|320px|Parts of "mole" that will drill into Mars and take its temperature at different points]]

On February 13, 2019, NASA announced that the InSight lander has placed its second instrument on the Martian surface. New images confirm that the Heat Flow and Physical Properties Package, or HP3, was successfully deployed on Feb. 12 about 3 feet (1 meter) from InSight's seismometer. HP3 measures heat moving through Mars' subsurface.
Equipped with a self-hammering spike, mole, the instrument will burrow up to 16 feet (5 meters) below the surface, deeper than any previous mission to the Red Planet. This compares to, the Viking 1 lander which went down 8.6 inches (22 centimeters). While the Phoenix lander dug down 7 inches (18 centimeters).

HP3 looks a bit like an automobile jack but with a vertical metal tube up front to hold the 16-inch-long (40-centimeter-long) mole. A tether connects HP3's support structure to the lander, while a tether attached to the top of the mole features heat sensors to measure the temperature of the Martian subsurface. Meanwhile, heat sensors in the mole itself will measure the soil's thermal conductivity, that is how easily heat moves through the subsurface.

The mole will stop every 19 inches (50 centimeters) to take a thermal conductivity measurement of the soil. Because hammering creates friction and releases heat, the mole is first allowed to cool down for a good two days. Then it will be heated up by about 50 degrees Fahrenheit (10 degrees Celsius) over 24 hours. Temperature sensors within the mole measure how rapidly this happens, which tells scientists the conductivity of the soil.
If the mole encounters a large rock before reaching at least 10 feet (3 meters) down, the team will need a full Martian year (two Earth years) to filter noise out of their data. This is one reason the team carefully selected a landing site with few rocks and why it spent weeks picking where to place the instrument.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7335&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190213-4</ref>

In May 2021, the InSight team boasted the power output of the solar cells with a novel method. By using the scoop to drop sand grains on the panels, they raised the power by 30 watt-hours. When there was maximum wind, they caused sand to fall and then bounce along on the solar panels. The larger grains carried off the smaller dust particles in the wind. A big drawback to using solar panels on Mars is that they get covered with dust. However, sometimes we get lucky because passing dust devils clean the panels.<ref>https://www.jpl.nasa.gov/news/nasas-insight-mars-lander-gets-a-power-boost?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20210603-3</ref>

==Mission Discoveries==

InSight's seismometer recorded its first marsquake on April 6, 2019, and its largest seismic signal to date at 7:23 p.m. PDT (10:23 EDT) on May 22, 2019. That last event is believed to be a marsquake of magnitude 3.0.<ref>https://outlook.live.com/mail/inbox/id/AQMkADAwATExAGNiNy00YzQ1LTM4MjMtMDACLTAwCgBGAAADdsmEa%2FgtIEmBK%2FX8yb671wcAkr%2FaXi2mwEKimhNbcs0ITQAAAgEMAAAAkr%2FaXi2mwEKimhNbcs0ITQACxRb2xwAAAA%3D%3D</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> NASA's Mars InSight lander has measured and recorded for the first time ever a likely "marsquake." This is the first recorded vibration that seems to have originated inside Mars. It's greater duration is similar to that of moonquakes detected on the lunar surface during the Apollo missions,"said Lori Glaze, Planetary Science Division director at NASA Headquarters. Sismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> As of October 2019. Insight has found 21 Marsquakes.<ref>https://www.space.com/mars-insight-lander-burrowing-probe-hope.html?utm_source=Selligent&utm_medium=email&utm_campaign=8763&utm_content=20191016_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=pAsrLmboNLkM3OHTeP4JZwcN0DgadelbQged0iUjw8q_smkwBFQbBTBN4arp5CfWSRZEdakPqW36HVks02yDLWEFGsm9W%2Bsppz</ref> <ref>https://www.universetoday.com/143625/insight-has-already-detected-21-marsquakes/</ref>

As summary of Insight's first Martian year of operation reported that there were more than 450 events that appear to be of
tectonic origin. Three events had magnitudes between 3.1 and 3.6 and were at distances between 27.5° and 47°
(±10°) from the lander. They originating in the Cerberus Fossae region.<ref>Panning, M., et al. 2021. RESULTS FROM INSIGHT’S FIRST FULL MARTIAN YEAR. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 1533.pdf</ref>

The marsquakes measured by insight have led scientists to conclude that the three biggest events were from the Cerberus Fossae region. It is located about 1’500 km away. The tectonic graben system at Cerberus Fossae is caused by the great mass of Elysium Mons, a volcano in the Elysium Planitia region. Mars has a total seismic energy between that of the moon and the Earth.<ref>https://ethz.ch/en/news-and-events/eth-news/news/2020/02/seismicity-of-mars.html?fbclid=IwAR0HwOkxqG_QmBNn62TxW8yMKZDDNAtfB2LEIHGZ4zNvIjbGD8wFWZJaI6k</ref> <ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref> <ref>Giardini D et al.: The seismicity of Mars. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0539-8
</ref> <ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref> The top 8–11 km of the crust is highly altered and/or broken.<ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref>
All of the seismic event found so far are of tectonic origins--none were the result of impacts.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

Mars soil is strange--very cohesive. Holes dug on Mars showed no lip; it seems the soil was just pounded into the ground.<ref>https://www.space.com/mars-soil-weird-nasa-insight-lander.html?utm_source=Selligent&utm_medium=email&utm_campaign=9036&utm_content=20191022_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=6BJGMRJ6hO865ajoAYi4Nmpcq_wRcyNG4CEPalniT_t4eiV%2B%2BNyldqilky%2BFCzep%2BIlvwPHsKTQcyrSLTwmD0ToRMHgw5jd669</ref>

[[File:Rollingstonesrock.jpg|right|thumb|320px|Rock that was named "Rolling Stones Rock." One can see the trail the rock moved when InSight landed]]

[[File:Insight marsweather white.png|600pxr|Weather data from Insight]]

Insight has detected dust devils with the weather station.

On 28 February 2019, the Heat and Physical Properties Package probe (HP³) started its drilling into the surface of Mars. The probe and its digging mole were intended to reach a maximum depth of 5 meters (16 ft) about two months after, but on 7 March 2019, the HP³ instrument's mole paused its digging. The mole had only gone down to about 35 cm (14 in)<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref>

At first, it was thought that maybe the mole hit a rock--that would have been hard to deal with. But in October 2019, scientists at JPL concluded that the mole could not go any farther because the soil on Mars does not provide necessary friction for drilling. Hence, the mole bounces around and makes a wide pit around itself instead of digging deeper. However, they devised a manoeuvre called "pinning" in which they press the side of the scoop against the mole to try and pin it to the side of the wall of the hole to increase friction to stop it from moving forward while digging.<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref> NASA reported that the pinning worked.<ref>https://mars.nasa.gov/news/8529/mars-insights-mole-is-moving-again/</ref>

NASA has gave up trying to deploy a heat flow probe in January, 2021. Almost two years of trying different approaches did not work. The team attempted to push down the mole with the scoop on the end of the lander’s robotic arm to prevent it from rebounding. They tried to tamp down regolith around the hole. They filled in the widening hole so the mole could gain more friction, but nothing worked.<ref>https://spacenews.com/nasa-ceases-efforts-to-deploy-mars-insight-heat-flow-probe</ref> <ref>https://www.jpl.nasa.gov/news/nasa-insights-mole-ends-its-journey-on-mars</ref>

On December 16, 2020, NASA reported that InSight had detected more than 480 quakes in a
little more than one Martian year after landing. However, none had greater than a 3.7 magnitude and none exhibited surface waves--only P and S waves. The lack of surface waves could be due to extensive fracturing in the top 6 miles (10 kilometers) below the lander. Or it could also mean that the quakes InSight detected are coming from deep within the planet. Deep quakes do not make strong surface waves.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight</ref>

By March, 2021, Insight had detected about 500 events, according to Philippe Lognonné, principal investigator.<ref>https://www.space.com/insight-mission-mars-core-size-finding?utm_source=Selligent&utm_medium=email&utm_campaign=SDC_Newsletter&utm_content=SDC_Newsletter+&utm_term=2946561</ref>

The timing of the quakes was a bit unusual. Once InSight began hearing quakes, they occurred every day. Then, in late June, quakes stopped. Just five quakes have been detected since then, all of them since September. Experts think Mars' wind is responsible for these seismically blank periods. The time when no quakes were measured was the windiest season of the Martian year. This idea is supported by the fact that it took a while before any quakes were found and that was also a windy time for a regional dust storm was finishing up.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight/</ref>

Journal articles published in July 2021 in the journal Science detailed what has been learned about the Martian interior to date. Its crust is probably 24- to 72-kilometers thick, while its lithosphere is about 500 kilometers thick. Like the Earth, Mars has a low-velocity layer under its lithosphere. The Martian crust is highly enriched (13 to 20 times as much) in radioactive elements that help to heat this layer, but at the expense of the interior. In other words, these heat producing elements lie more in the crust than in the deeper interior. Mars has a large (1830 kilometer) liquid core.<ref>https://science.sciencemag.org/content/373/6553/434</ref> <ref>Khan, A., et al. 2021. Upper mantle structure of Mars from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 434-438
DOI: 10.1126/science.abf2966</ref> <ref>https://www.technologyreview.com/2021/07/23/1030040/we-just-got-our-best-ever-look-at-the-inside-of-mars/</ref> <ref>https://science.sciencemag.org/content/373/6553/438</ref> <ref>Knapmeyer-Endrun, B. et al. 2021. Thickness and structure of the martian crust from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 438-443
DOI: 10.1126/science.abf8966</ref> The core has an average density of 5.7 to 6.3 grams per cubic centimeter. To achieve that density means that a great deal of light elements must be dissolved in an iron-nickel core. The number of Marsquakes that were detected was problably reduced by a large seismic core shadow as seen from InSight’s position on the planet. It would have been difficult to find quakes near Tharsis. Tharsis contains many huge volcanoes, including Olympus Mons. One might expect this region to produce many quakes, but they can not be found by InSight.<ref>https://science.sciencemag.org/content/373/6553/443</ref> <ref>Stahler, S. et al. 2021. Seismic detection of the martian core. Science. Vol. 373, Issue 6553, pp. 443-448
DOI: 10.1126/science.abi7730</ref> Quakes have an area where waves can't pass through; hence, we can't observe earthquakes form that region. To be technical, it is the angular distances of 104 to 140 degrees from a given earthquake. In that area, S waves are being stopped by the liquid core and P waves are being bent or refracted, by the liquid core.<ref>https://earthquake.usgs.gov/learn/glossary/?term=shadow%20zone</ref>

Mission scientists said that one 4.2-magnitude earthquake struck roughly 8,500 kilometers (5,280 miles) from InSight in August. This is much farther than the other quakes.<ref>https://www.sciencetimes.com/articles/33612/20210924/nasa-insight-mars-lander-detects-3-massive-earthquakes-red-planet.htm</ref> Furthermore, it lasted for almost an hour and a half.<ref> https://www.techtimes.com/articles/265793/20210924/nasa-insight-lander-mars-quakes-nasa-insight-lander-mars-quakes-magnitude-4-mars-quake-over-1-hour.htm</ref>

A large research team announced that they had determined details of the Martian the subsurface to about a depth of 200 m. Right beneath the surface is a 3 meter regolith layer of sandy material. Next, there is a 15 meter layer of blocky ejecta that came from past impacts. Under the blocker layer is a basalt lava flow. Between lava flows is a layer of sedimentary material. The upper basalt layer is of Amazonian age--about 1.7 billion years old. The lower basalt layer is of Hesperian age (3.6 billion years old).<ref>https://scitechdaily.com/nasas-mars-insight-lander-uses-wind-induced-vibrations-to-reveal-the-red-planets-subsurface-layers/</ref> <ref> Hobiger, M. et al. 2021. The shallow structure of Mars at the InSight
landing site from inversion of ambient vibrations. NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-26957-7</ref> The researchers used the faint vibrations induced by Martian winds to discover the subsurface structure.<ref> https://www.msn.com/en-us/news/technology/nasa-mars-lander-makes-1st-ever-map-of-red-planet-underground-by-listening-to-winds/ar-AAR3v7Q?ocid=uxbndlbing,</ref>

In an abstract released in February of 2022. researchers described what had been learned from InSight at that time--after almost 1000 Marsquakes had been detected. The crust is 20-35 km thick under insight.<ref> Knapmeyer-Endrun et al.,
Science, 373, 438-443, 2021 </ref> <ref>Kim et al., J. Geo Mantlephy. Res., Planets, in press, 2022</ref> <ref>Compaire et al.
J. Geophy. Res., Planets, 126, e2020JE006498, 2021</ref>
<ref> Schimmel et al. Earth and Space Science, 8,
e2021EA001755, 2021</ref> Seismic velocity was 7.8 Km/sec. The core has a radius of 1830 Km and a density of 6000 Kg/m cubed.<ref> Stähler et al., Science, 373, 443-448,
2021</ref> <ref> Khan et al., EPSL, 578, 2022</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf</ref> <ref>Lognonne, P. et al. 2022. SEIS achievement for Mars Seismology after 1000 sols of seismic monitoring. 53rd Lunar and Planetary Science Conference (2022). 2279.pdf</ref>

[[File:InSights Seismogramm5.png|center|thumb|320px|Magnitude 5 quake, as seen by InSight]]

In May, 2022, NASA announced that InSight detected the largest quake ever detected on Mars; it had an estimated magnitude of 5. This temblor occurred on May 4, 2022, the 1,222nd Martian day. Insight has observed more than 1,313 quakes since landing in November 2018. The largest previously recorded quake was an estimated magnitude 4.2 detected Aug. 25, 2021.<ref>https://www.jpl.nasa.gov/news/nasas-insight-records-monster-quake-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220509-1</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101543</ref> <ref>Kawamura. T., et al. 2022. S1222a - the largest Marsquake detected by InSight. Geophysical Research Letters. doi: 10.1029/2022GL101543</ref>

[[File:Troughs in Elysium Planitia.JPG|600pxr|Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes]]

Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes

Research published in August, 2022 suggested that "uncemented material" largely fills in the region under InSight. That implies that little water is present. Although the ground has much pore space, the pore spaces probably are largely just full of air, rather than ice or other cementing material. It was thought that perhaps there could be ice- or liquid water-saturated layers within the upper 300 m beneath InSight, but this study shows that is not the case. Had there been cement between soil particles, it has likely been broken by impacts or marsquakes. InSight measures the speed of seismic waves within the crust. These velocities change depending on rock type and the material that fills the pores within rocks. Hence, the amount of pore space can be measured. The velocity of these waves would be different going through ice or air.<ref> https://www.msn.com/en-us/news/technology/equatorial-mars-is-surprisingly-dry-nasas-insight-lander-finds/ar-AA10zrBw</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL099250</ref> <ref>Wright, V., et al. 2022. A minimally cemented shallow crust beneath InSight. Geophysical Research Letters. doi: 10.1029/2022GL099250 </ref>

NASA announced on September 19, 2022 that Insight had detected audio and seismic waves from an impact. In other words, they heard the impact.
Researchers calculated where the impact happened, and then found the resulting craters with CTX and HiRISE. The body entered Mars’ atmosphere on Sept. 5, 2021. It then blew apart into at least three pieces. Each of them made a crater. Scientists studied the seismic recordings to see what an impact event looks like. They were then able to discover three other impacts that occurred on May 27, 2020; Feb. 18, 2021; and Aug. 31, 2021. The size of the quakes produced by these impacts was small--no more than magnitude 2.0.<ref>https://www.nature.com/articles/s41561-022-01014-0</ref> <ref>Garcia, R.F., Daubar, I.J., Beucler, É. et al. Newly formed craters on Mars located using seismic and acoustic wave data from InSight. Nat. Geosci. (2022). https://doi.org/10.1038/s41561-022-01014-0</ref> <ref>https://www.jpl.nasa.gov/news/nasas-insight-hears-its-first-meteoroid-impacts-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Daily09192022</ref>

[[File:Insightimpacecrater.jpg|center|thumb|320px|Impact craters that InSight heard and that scientists were are to photograph with HiRISE. the projectile broke apart as it entered the Martian atmosphere.]]

The sound can be heard at https://www.youtube.com/watch?v=439Hg8aAars

[[File:Insightselfydust.jpg|center|thumb|320px|Selfie of Insight as of April, 2022. Since solar panels are almost totally covered with dust, Insight may not last much longer. However it was still going as of October, 2022]]

On October 27, 2022, NASA described a new impact that was seen with orbiting cameras and detected by Insight. This discovery was published in the journal Science.
The impacting body is estimated to have been 16 to 39 feet (5 to 12 meters) across. It would have burned up in Earth’s atmosphere. The crater produced by the impact was larger than a football field and was 70 feet (21 meters) deep. Pieces of ejecta flew as far as 23 miles (37 kilometers) away.

<gallery class="center" widths="380px" heights="360px">
File:Newcraterctxbeforeafter.jpg|Before and after pictures of site where the new crater was formed. Pictures are from CTX.
File:Newcratericesize.jpeg|Close view of new crater, as seen by HiRISE. Sizes are indicated. White dots are boulder-sized chunks of ice that were blown out by the impact.
</gallery>

The impact happened on December 24, 2021 and was measured to have made a marsquake of magnitude 4 by InSight. This may have been the largest impact that has ever been observed. Chunks of ice that were excavated were the biggest ever found this close to the equator. That's good news for future colonists--maybe ice is more widespread than previously thought.<ref>https://mars.nasa.gov/news/9289/nasas-insight-lander-detects-stunning-meteoroid-impact-on-mars/?s=03&fbclid=IwAR2wjZ6yhSZ1XrU553LOZ8R8jJugkkv79uHMvLkZRqfn03ed_6X8Q-ncj5c</ref>

InSight found that nearly all the Marsquakes originated near Cerberus Fossae. Researchers have discovered that there is a large plume under the area. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). The uplift caused by this plume stretched the crust, cracking it to form Cerberus Fossae. Plumes like this are like the plume under Hawaii.

In all, InSight detected 8 impact events. However, none were found in the first Martian year. Four of the events resulted in clusters of craters. All 8 events were in the northern equatorial to mid-latitudes of the planet.<ref>Ingrid J., et al. 2023. MARTIAN SEISMIC EVENTS CONFIRMED AS IMPACTS TO DATE. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 2616.pdf.</ref>

Besides being the focus of Marsquakes, other forms of evidence for the plume are (1) a rise of a mile above the surroundings, (2) crater floors tilted away from the rise, and (3) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.
The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

On December 21, 2022, NASA declared the mission finished when they were unable to contact the lander after two consecutive attempts.
The solar panels had too much dust on them to function<ref>https://www.jpl.nasa.gov/news/nasa-retires-insight-mars-lander-mission-after-years-of-science?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20221221-3</ref>

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Cerberus Fossae]]

*[[Elysium quadrangle]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Interior of Mars]]
*[[Geography of Mars]]

==Recommended reading==

*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://www.jpl.nasa.gov/missions/insight/ JPL Mission to Mars InSight]

==External links==

*[https://www.youtube.com/watch?v=439Hg8aAars NASA's InSight hears its first meteoroid impacts on Mars]

*[https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight Mars InSight Mission]
*[https://www.youtube.com/watch?v=bGD_YF64Nwk Mission Control Live: NASA InSight Mars Landing]
*[https://www.youtube.com/watch?v=lGwM30F4Oao How NASA's Next Mars Mission Will Take the Red Planet's Pulse | Decoder]

*[https://mars.nasa.gov/insight/timeline/surface-operations/ Timeline of Surface Operations]

*[https://usc-marshall-panopto-demo.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=399919d8-faf3-4feb-bdec-aae80114eeb6 / Update on InSight from Mars Society Convention 2019]

*[https://www.youtube.com/watch?v=kca3Y8XUK1c InSight Live Q&A: Journey to the Center of Mars with the Lander Team]

*https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf InSight Seismology after 1000 sols of seismic monitoring

[[Category:Lander Missions]]

InSight Mission

2023-03-20T19:52:47Z

Suitupandshowup: /* Mission Discoveries */ added new info and ref

NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) made a soft landing as planned on November 26, 2018 at 4.502 °N, 135.623 °E. InSight landed in a crater that is 25 meters in diameter Homestead hollow. This crater is filed with sediments from impacts. The sediments have been modified and transported by wind.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

It is the first space robotic explorer to study the inside of Mars: its crust, mantle, and core. It set down at exactly 2:52:59 p.m. EST. We found out about the landing by way of two small experimental Mars Cube One (MarCO) CubeSats. They were launched on the same rocket as InSight and relayed information from the lander. <ref>https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight</ref>
The launch took place with an Atlas V-401 from Vandenberg Air Force Base, California on May 5, 2018 7:05 a.m. ET. It’s main instruments are a seismometer (SEIS), a heat probe, and a radio science instrument (RISE).<ref>https://mars.nasa.gov/insight/spacecraft/instruments/summary/</ref>

See the [[Interior of Mars]] for more information of Mars' structure.

Artist’s conception of Insight lander sitting on Mars with instruments deployed

[[File:PIA22878b-annotatedinsightlanding.jpg |600pxr|Location of Insight]]

The red dot shows where InSight landed. It landed just about in the center of its landing ellipse. The location is in the Elysium quadrangle at about 4.5 N and 135.6 E (224.4 W).

==Spacecraft==

InSight weighs 794 pounds (360 kilograms). It is 19 feet 8 inches (6 meters) with solar panels deployed ("wingspan"), and its deck is 5 feet 1 inch (1.56 meters) in diameter.<ref>https://mars.nasa.gov/insight/spacecraft/about-the-lander/</ref> Since dust covering solar panels is a persistent problem for Mars missions, the solar panels on InSight are about two times larger than necessary.

[[File:ESP 058005 1845-lander-full-res.jpg |right|thumb|320px|InSight sitting on the surface, as seen by HiRISE]]

==Mission Activities==

December 19, 2018, InSight's seismometer was set onto the ground directly in front of the lander, about as far away as the arm can reach ---- 5.367 feet. Principal Investigator Bruce Banerdt, stated "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives." The seismometer allows scientists to peer into the Martian interior by studying ground motion — also known as marsquakes. Each marsquake acts as a kind of flashbulb that illuminates the structure of the planet's interior. By studying how seismic waves pass through the layers of the planet, scientists can deduce the depth and composition of these layers.<ref>https://mars.nasa.gov/news/8402/nasas-insight-places-first-instrument-on-mars/?site=insight</ref> InSight's seismometer is so sensitive that if Mars had an atmosphere, and a butterfly landed on the seismometer it's vibrations would be detected. It can detect ground motion that is only half the width of a hydrogen atom.

[[File:22280 PIA22959windshield.jpg|left|thumb|320px|InSights's seismometer with wind cover on the Martian surface.]]

[[File:PIA23045 hiresmole.jpg|right|thumb|320px|Parts of "mole" that will drill into Mars and take its temperature at different points]]

On February 13, 2019, NASA announced that the InSight lander has placed its second instrument on the Martian surface. New images confirm that the Heat Flow and Physical Properties Package, or HP3, was successfully deployed on Feb. 12 about 3 feet (1 meter) from InSight's seismometer. HP3 measures heat moving through Mars' subsurface.
Equipped with a self-hammering spike, mole, the instrument will burrow up to 16 feet (5 meters) below the surface, deeper than any previous mission to the Red Planet. This compares to, the Viking 1 lander which went down 8.6 inches (22 centimeters). While the Phoenix lander dug down 7 inches (18 centimeters).

HP3 looks a bit like an automobile jack but with a vertical metal tube up front to hold the 16-inch-long (40-centimeter-long) mole. A tether connects HP3's support structure to the lander, while a tether attached to the top of the mole features heat sensors to measure the temperature of the Martian subsurface. Meanwhile, heat sensors in the mole itself will measure the soil's thermal conductivity, that is how easily heat moves through the subsurface.

The mole will stop every 19 inches (50 centimeters) to take a thermal conductivity measurement of the soil. Because hammering creates friction and releases heat, the mole is first allowed to cool down for a good two days. Then it will be heated up by about 50 degrees Fahrenheit (10 degrees Celsius) over 24 hours. Temperature sensors within the mole measure how rapidly this happens, which tells scientists the conductivity of the soil.
If the mole encounters a large rock before reaching at least 10 feet (3 meters) down, the team will need a full Martian year (two Earth years) to filter noise out of their data. This is one reason the team carefully selected a landing site with few rocks and why it spent weeks picking where to place the instrument.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7335&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190213-4</ref>

In May 2021, the InSight team boasted the power output of the solar cells with a novel method. By using the scoop to drop sand grains on the panels, they raised the power by 30 watt-hours. When there was maximum wind, they caused sand to fall and then bounce along on the solar panels. The larger grains carried off the smaller dust particles in the wind. A big drawback to using solar panels on Mars is that they get covered with dust. However, sometimes we get lucky because passing dust devils clean the panels.<ref>https://www.jpl.nasa.gov/news/nasas-insight-mars-lander-gets-a-power-boost?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20210603-3</ref>

==Mission Discoveries==

InSight's seismometer recorded its first marsquake on April 6, 2019, and its largest seismic signal to date at 7:23 p.m. PDT (10:23 EDT) on May 22, 2019. That last event is believed to be a marsquake of magnitude 3.0.<ref>https://outlook.live.com/mail/inbox/id/AQMkADAwATExAGNiNy00YzQ1LTM4MjMtMDACLTAwCgBGAAADdsmEa%2FgtIEmBK%2FX8yb671wcAkr%2FaXi2mwEKimhNbcs0ITQAAAgEMAAAAkr%2FaXi2mwEKimhNbcs0ITQACxRb2xwAAAA%3D%3D</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> NASA's Mars InSight lander has measured and recorded for the first time ever a likely "marsquake." This is the first recorded vibration that seems to have originated inside Mars. It's greater duration is similar to that of moonquakes detected on the lunar surface during the Apollo missions,"said Lori Glaze, Planetary Science Division director at NASA Headquarters. Sismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> As of October 2019. Insight has found 21 Marsquakes.<ref>https://www.space.com/mars-insight-lander-burrowing-probe-hope.html?utm_source=Selligent&utm_medium=email&utm_campaign=8763&utm_content=20191016_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=pAsrLmboNLkM3OHTeP4JZwcN0DgadelbQged0iUjw8q_smkwBFQbBTBN4arp5CfWSRZEdakPqW36HVks02yDLWEFGsm9W%2Bsppz</ref> <ref>https://www.universetoday.com/143625/insight-has-already-detected-21-marsquakes/</ref>

As summary of Insight's first Martian year of operation reported that there were more than 450 events that appear to be of
tectonic origin. Three events had magnitudes between 3.1 and 3.6 and were at distances between 27.5° and 47°
(±10°) from the lander. They originating in the Cerberus Fossae region.<ref>Panning, M., et al. 2021. RESULTS FROM INSIGHT’S FIRST FULL MARTIAN YEAR. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 1533.pdf</ref>

The marsquakes measured by insight have led scientists to conclude that the three biggest events were from the Cerberus Fossae region. It is located about 1’500 km away. The tectonic graben system at Cerberus Fossae is caused by the great mass of Elysium Mons, a volcano in the Elysium Planitia region. Mars has a total seismic energy between that of the moon and the Earth.<ref>https://ethz.ch/en/news-and-events/eth-news/news/2020/02/seismicity-of-mars.html?fbclid=IwAR0HwOkxqG_QmBNn62TxW8yMKZDDNAtfB2LEIHGZ4zNvIjbGD8wFWZJaI6k</ref> <ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref> <ref>Giardini D et al.: The seismicity of Mars. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0539-8
</ref> <ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref> The top 8–11 km of the crust is highly altered and/or broken.<ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref>
All of the seismic event found so far are of tectonic origins--none were the result of impacts.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

Mars soil is strange--very cohesive. Holes dug on Mars showed no lip; it seems the soil was just pounded into the ground.<ref>https://www.space.com/mars-soil-weird-nasa-insight-lander.html?utm_source=Selligent&utm_medium=email&utm_campaign=9036&utm_content=20191022_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=6BJGMRJ6hO865ajoAYi4Nmpcq_wRcyNG4CEPalniT_t4eiV%2B%2BNyldqilky%2BFCzep%2BIlvwPHsKTQcyrSLTwmD0ToRMHgw5jd669</ref>

[[File:Rollingstonesrock.jpg|right|thumb|320px|Rock that was named "Rolling Stones Rock." One can see the trail the rock moved when InSight landed]]

[[File:Insight marsweather white.png|600pxr|Weather data from Insight]]

Insight has detected dust devils with the weather station.

On 28 February 2019, the Heat and Physical Properties Package probe (HP³) started its drilling into the surface of Mars. The probe and its digging mole were intended to reach a maximum depth of 5 meters (16 ft) about two months after, but on 7 March 2019, the HP³ instrument's mole paused its digging. The mole had only gone down to about 35 cm (14 in)<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref>

At first, it was thought that maybe the mole hit a rock--that would have been hard to deal with. But in October 2019, scientists at JPL concluded that the mole could not go any farther because the soil on Mars does not provide necessary friction for drilling. Hence, the mole bounces around and makes a wide pit around itself instead of digging deeper. However, they devised a manoeuvre called "pinning" in which they press the side of the scoop against the mole to try and pin it to the side of the wall of the hole to increase friction to stop it from moving forward while digging.<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref> NASA reported that the pinning worked.<ref>https://mars.nasa.gov/news/8529/mars-insights-mole-is-moving-again/</ref>

NASA has gave up trying to deploy a heat flow probe in January, 2021. Almost two years of trying different approaches did not work. The team attempted to push down the mole with the scoop on the end of the lander’s robotic arm to prevent it from rebounding. They tried to tamp down regolith around the hole. They filled in the widening hole so the mole could gain more friction, but nothing worked.<ref>https://spacenews.com/nasa-ceases-efforts-to-deploy-mars-insight-heat-flow-probe</ref> <ref>https://www.jpl.nasa.gov/news/nasa-insights-mole-ends-its-journey-on-mars</ref>

On December 16, 2020, NASA reported that InSight had detected more than 480 quakes in a
little more than one Martian year after landing. However, none had greater than a 3.7 magnitude and none exhibited surface waves--only P and S waves. The lack of surface waves could be due to extensive fracturing in the top 6 miles (10 kilometers) below the lander. Or it could also mean that the quakes InSight detected are coming from deep within the planet. Deep quakes do not make strong surface waves.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight</ref>

By March, 2021, Insight had detected about 500 events, according to Philippe Lognonné, principal investigator.<ref>https://www.space.com/insight-mission-mars-core-size-finding?utm_source=Selligent&utm_medium=email&utm_campaign=SDC_Newsletter&utm_content=SDC_Newsletter+&utm_term=2946561</ref>

The timing of the quakes was a bit unusual. Once InSight began hearing quakes, they occurred every day. Then, in late June, quakes stopped. Just five quakes have been detected since then, all of them since September. Experts think Mars' wind is responsible for these seismically blank periods. The time when no quakes were measured was the windiest season of the Martian year. This idea is supported by the fact that it took a while before any quakes were found and that was also a windy time for a regional dust storm was finishing up.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight/</ref>

Journal articles published in July 2021 in the journal Science detailed what has been learned about the Martian interior to date. Its crust is probably 24- to 72-kilometers thick, while its lithosphere is about 500 kilometers thick. Like the Earth, Mars has a low-velocity layer under its lithosphere. The Martian crust is highly enriched (13 to 20 times as much) in radioactive elements that help to heat this layer, but at the expense of the interior. In other words, these heat producing elements lie more in the crust than in the deeper interior. Mars has a large (1830 kilometer) liquid core.<ref>https://science.sciencemag.org/content/373/6553/434</ref> <ref>Khan, A., et al. 2021. Upper mantle structure of Mars from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 434-438
DOI: 10.1126/science.abf2966</ref> <ref>https://www.technologyreview.com/2021/07/23/1030040/we-just-got-our-best-ever-look-at-the-inside-of-mars/</ref> <ref>https://science.sciencemag.org/content/373/6553/438</ref> <ref>Knapmeyer-Endrun, B. et al. 2021. Thickness and structure of the martian crust from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 438-443
DOI: 10.1126/science.abf8966</ref> The core has an average density of 5.7 to 6.3 grams per cubic centimeter. To achieve that density means that a great deal of light elements must be dissolved in an iron-nickel core. The number of Marsquakes that were detected was problably reduced by a large seismic core shadow as seen from InSight’s position on the planet. It would have been difficult to find quakes near Tharsis. Tharsis contains many huge volcanoes, including Olympus Mons. One might expect this region to produce many quakes, but they can not be found by InSight.<ref>https://science.sciencemag.org/content/373/6553/443</ref> <ref>Stahler, S. et al. 2021. Seismic detection of the martian core. Science. Vol. 373, Issue 6553, pp. 443-448
DOI: 10.1126/science.abi7730</ref> Quakes have an area where waves can't pass through; hence, we can't observe earthquakes form that region. To be technical, it is the angular distances of 104 to 140 degrees from a given earthquake. In that area, S waves are being stopped by the liquid core and P waves are being bent or refracted, by the liquid core.<ref>https://earthquake.usgs.gov/learn/glossary/?term=shadow%20zone</ref>

Mission scientists said that one 4.2-magnitude earthquake struck roughly 8,500 kilometers (5,280 miles) from InSight in August. This is much farther than the other quakes.<ref>https://www.sciencetimes.com/articles/33612/20210924/nasa-insight-mars-lander-detects-3-massive-earthquakes-red-planet.htm</ref> Furthermore, it lasted for almost an hour and a half.<ref> https://www.techtimes.com/articles/265793/20210924/nasa-insight-lander-mars-quakes-nasa-insight-lander-mars-quakes-magnitude-4-mars-quake-over-1-hour.htm</ref>

A large research team announced that they had determined details of the Martian the subsurface to about a depth of 200 m. Right beneath the surface is a 3 meter regolith layer of sandy material. Next, there is a 15 meter layer of blocky ejecta that came from past impacts. Under the blocker layer is a basalt lava flow. Between lava flows is a layer of sedimentary material. The upper basalt layer is of Amazonian age--about 1.7 billion years old. The lower basalt layer is of Hesperian age (3.6 billion years old).<ref>https://scitechdaily.com/nasas-mars-insight-lander-uses-wind-induced-vibrations-to-reveal-the-red-planets-subsurface-layers/</ref> <ref> Hobiger, M. et al. 2021. The shallow structure of Mars at the InSight
landing site from inversion of ambient vibrations. NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-26957-7</ref> The researchers used the faint vibrations induced by Martian winds to discover the subsurface structure.<ref> https://www.msn.com/en-us/news/technology/nasa-mars-lander-makes-1st-ever-map-of-red-planet-underground-by-listening-to-winds/ar-AAR3v7Q?ocid=uxbndlbing,</ref>

In an abstract released in February of 2022. researchers described what had been learned from InSight at that time--after almost 1000 Marsquakes had been detected. The crust is 20-35 km thick under insight.<ref> Knapmeyer-Endrun et al.,
Science, 373, 438-443, 2021 </ref> <ref>Kim et al., J. Geo Mantlephy. Res., Planets, in press, 2022</ref> <ref>Compaire et al.
J. Geophy. Res., Planets, 126, e2020JE006498, 2021</ref>
<ref> Schimmel et al. Earth and Space Science, 8,
e2021EA001755, 2021</ref> Seismic velocity was 7.8 Km/sec. The core has a radius of 1830 Km and a density of 6000 Kg/m cubed.<ref> Stähler et al., Science, 373, 443-448,
2021</ref> <ref> Khan et al., EPSL, 578, 2022</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf</ref> <ref>Lognonne, P. et al. 2022. SEIS achievement for Mars Seismology after 1000 sols of seismic monitoring. 53rd Lunar and Planetary Science Conference (2022). 2279.pdf</ref>

[[File:InSights Seismogramm5.png|center|thumb|320px|Magnitude 5 quake, as seen by InSight]]

In May, 2022, NASA announced that InSight detected the largest quake ever detected on Mars; it had an estimated magnitude of 5. This temblor occurred on May 4, 2022, the 1,222nd Martian day. Insight has observed more than 1,313 quakes since landing in November 2018. The largest previously recorded quake was an estimated magnitude 4.2 detected Aug. 25, 2021.<ref>https://www.jpl.nasa.gov/news/nasas-insight-records-monster-quake-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220509-1</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101543</ref> <ref>Kawamura. T., et al. 2022. S1222a - the largest Marsquake detected by InSight. Geophysical Research Letters. doi: 10.1029/2022GL101543</ref>

[[File:Troughs in Elysium Planitia.JPG|600pxr|Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes]]

Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes

Research published in August, 2022 suggested that "uncemented material" largely fills in the region under InSight. That implies that little water is present. Although the ground has much pore space, the pore spaces probably are largely just full of air, rather than ice or other cementing material. It was thought that perhaps there could be ice- or liquid water-saturated layers within the upper 300 m beneath InSight, but this study shows that is not the case. Had there been cement between soil particles, it has likely been broken by impacts or marsquakes. InSight measures the speed of seismic waves within the crust. These velocities change depending on rock type and the material that fills the pores within rocks. Hence, the amount of pore space can be measured. The velocity of these waves would be different going through ice or air.<ref> https://www.msn.com/en-us/news/technology/equatorial-mars-is-surprisingly-dry-nasas-insight-lander-finds/ar-AA10zrBw</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL099250</ref> <ref>Wright, V., et al. 2022. A minimally cemented shallow crust beneath InSight. Geophysical Research Letters. doi: 10.1029/2022GL099250 </ref>

NASA announced on September 19, 2022 that Insight had detected audio and seismic waves from an impact. In other words, they heard the impact.
Researchers calculated where the impact happened, and then found the resulting craters with CTX and HiRISE. The body entered Mars’ atmosphere on Sept. 5, 2021. It then blew apart into at least three pieces. Each of them made a crater. Scientists studied the seismic recordings to see what an impact event looks like. They were then able to discover three other impacts that occurred on May 27, 2020; Feb. 18, 2021; and Aug. 31, 2021. The size of the quakes produced by these impacts was small--no more than magnitude 2.0.<ref>https://www.nature.com/articles/s41561-022-01014-0</ref> <ref>Garcia, R.F., Daubar, I.J., Beucler, É. et al. Newly formed craters on Mars located using seismic and acoustic wave data from InSight. Nat. Geosci. (2022). https://doi.org/10.1038/s41561-022-01014-0</ref> <ref>https://www.jpl.nasa.gov/news/nasas-insight-hears-its-first-meteoroid-impacts-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Daily09192022</ref>

[[File:Insightimpacecrater.jpg|center|thumb|320px|Impact craters that InSight heard and that scientists were are to photograph with HiRISE. the projectile broke apart as it entered the Martian atmosphere.]]

The sound can be heard at https://www.youtube.com/watch?v=439Hg8aAars

[[File:Insightselfydust.jpg|center|thumb|320px|Selfie of Insight as of April, 2022. Since solar panels are almost totally covered with dust, Insight may not last much longer. However it was still going as of October, 2022]]

On October 27, 2022, NASA described a new impact that was seen with orbiting cameras and detected by Insight. This discovery was published in the journal Science.
The impacting body is estimated to have been 16 to 39 feet (5 to 12 meters) across. It would have burned up in Earth’s atmosphere. The crater produced by the impact was larger than a football field and was 70 feet (21 meters) deep. Pieces of ejecta flew as far as 23 miles (37 kilometers) away.

<gallery class="center" widths="380px" heights="360px">
File:Newcraterctxbeforeafter.jpg|Before and after pictures of site where the new crater was formed. Pictures are from CTX.
File:Newcratericesize.jpeg|Close view of new crater, as seen by HiRISE. Sizes are indicated. White dots are boulder-sized chunks of ice that were blown out by the impact.
</gallery>

The impact happened on December 24, 2021 and was measured to have made a marsquake of magnitude 4 by InSight. This may have been the largest impact that has ever been observed. Chunks of ice that were excavated were the biggest ever found this close to the equator. That's good news for future colonists--maybe ice is more widespread than previously thought.<ref>https://mars.nasa.gov/news/9289/nasas-insight-lander-detects-stunning-meteoroid-impact-on-mars/?s=03&fbclid=IwAR2wjZ6yhSZ1XrU553LOZ8R8jJugkkv79uHMvLkZRqfn03ed_6X8Q-ncj5c</ref>

InSight found that nearly all the Marsquakes originated near Cerberus Fossae. Researchers have discovered that there is a large plume under the area. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). The uplift caused by this plume stretched the crust, cracking it to form Cerberus Fossae. Plumes like this are like the plume under Hawaii.

In all, InSight detected 8 impact events. However, none were found in the first Martian year. Four of the events resulted in clusters of craters. All 8 events were in the northern equatorial to mid-latitudes of the planet.<ref>

Besides being the focus of Marsquakes, other forms of evidence for the plume are (1) a rise of a mile above the surroundings, (2) crater floors tilted away from the rise, and (3) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.
The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>Ingrid J., et al. 2023. MARTIAN SEISMIC EVENTS CONFIRMED AS IMPACTS TO DATE. 54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806). 2616.pdf.</ref>

On December 21, 2022, NASA declared the mission finished when they were unable to contact the lander after two consecutive attempts.
The solar panels had too much dust on them to function<ref>https://www.jpl.nasa.gov/news/nasa-retires-insight-mars-lander-mission-after-years-of-science?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20221221-3</ref>

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Cerberus Fossae]]

*[[Elysium quadrangle]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Interior of Mars]]
*[[Geography of Mars]]

==Recommended reading==

*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://www.jpl.nasa.gov/missions/insight/ JPL Mission to Mars InSight]

==External links==

*[https://www.youtube.com/watch?v=439Hg8aAars NASA's InSight hears its first meteoroid impacts on Mars]

*[https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight Mars InSight Mission]
*[https://www.youtube.com/watch?v=bGD_YF64Nwk Mission Control Live: NASA InSight Mars Landing]
*[https://www.youtube.com/watch?v=lGwM30F4Oao How NASA's Next Mars Mission Will Take the Red Planet's Pulse | Decoder]

*[https://mars.nasa.gov/insight/timeline/surface-operations/ Timeline of Surface Operations]

*[https://usc-marshall-panopto-demo.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=399919d8-faf3-4feb-bdec-aae80114eeb6 / Update on InSight from Mars Society Convention 2019]

*[https://www.youtube.com/watch?v=kca3Y8XUK1c InSight Live Q&A: Journey to the Center of Mars with the Lander Team]

*https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf InSight Seismology after 1000 sols of seismic monitoring

[[Category:Lander Missions]]

Ismenius Lacus quadrangle

2023-03-04T22:57:24Z

Suitupandshowup: /* Other images from Ismenius Lacus quadrangle */ added image

{{Mars atlas}}

{| class="wikitable sortable"
|MC-05
|Ismenius Lacus
|30–65° N
|0–60° E
|[[Mars Quadrangles|Quadrangles]]
|[[Mars Atlas|Atlas]]
|}
<gallery widths="400" heights="300">
File:USGS-Mars-MC-5-IsmeniusLacusRegion-mola.png|Elevations
File:PIA00165-Mars-MC-5-IsmeniusLacusRegion-19980604.jpg
</gallery>
[[Category:Mars Atlas]]

This quadrangle has some of the most mysterious-looking landscapes on the planet. It truly looks like another world here. Strong evidence of a past ocean on Mars exists in this region and is described below. The Ismenius Lacus quadrangle contains regions called Deuteronilus Mensae and Protonilus Mensae, two places that are of special interest to scientists. They contain abundant evidence of present and past glacial activity. They also have a landscape unique to Mars, called Fretted terrain. The largest crater in the area is Lyot Crater, which contains channels probably carved by liquid water.<ref>Carter | first1 = J. | last2 = Poulet | first2 = F. | last3 = Bibring | first3 = J.-P. | last4 = Murchie | first4 = S. | year = 2010 | title = Detection of Hydrated Silicates in Crustal Outcrops in the Northern Plains of Mars | url = | journal = Science | volume = 328 | issue = 5986| pages = 1682–1686 | </ref>

The Ismenius Lacus quadrangle is located in the northern hemisphere and covers 30° to 65° north latitude and 300° to 360° west longitude (60° to 0° east longitude). The southern and northern borders of the Ismenius Lacus quadrangle are approximately 3065 km (1,905 mi) and 1500 km wide (930 mi) respectively. The north-to-south distance is about 2050 km (1,270 mi) (a bit less than the length of Greenland).<ref>Distances calculated using NASA World Wind measuring tool. http://worldwind.arc.nasa.gov/.</ref> The Ismenius Lacus quadrangle contains parts of regions named Acidalia Planitia, Arabia Terra, Vastitas Borealis, and Terra Sabaea.<ref>http://planetarynames.wr.usgs.gov/SearchResults?target=MARS&featureType=Terra,%20terrae</ref>

In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.

==Origin of names==

Ismenius Lacus is the name of a classical albedo feature located at 40° N and 30° E on Mars. Like most names for Martian places, Ismenius comes from old myths and stories. The term is Latin for Ismenian Lake, and refers to the Ismenian Spring near Thebes in Greece where Cadmus slew the guardian dragon. Cadmus was the legendary founder of Thebes, and had come to the spring to fetch water. The name was approved by the International Astronomical Union (IAU) in 1958.<ref>USGS Gazetteer of Planetary Nomenclature. Mars. http://planetarynames.wr.usgs.gov/.</ref> All names suggested for astronomical features have to eventually approved by the International Astronomical Union (IAU).

Some important areas in this quadrangle derive from the names of canals that some early astronomers saw in this broad area. One such large canal they called Nilus. Since 1881–1882 it was split into other canals, some were called Nilosyrtis, Protonilus (first Nile),and Deuteronilus (second Nile).<ref>Blunck, J. 1982. Mars and its Satellites. Exposition Press. Smithtown, N.Y.</ref>

==Ocean==

[[File:ESP 054857 2270grooves.jpg|600pxr|Channels that may have been made by the backwash of tsunamis in an ocean Image is from HiRISE under the [[HiWish program]]]]

Channels made by the backwash from tsunamis, tsunamis were probably caused by asteroids striking an ocean. Image is from HiRISE under the [[HiWish program]]

Many researchers have suggested that Mars once had a great ocean in the north.<ref>Parker | first1 = T. J. | last2 = Gorsline | first2 = D. S. | last3 = Saunders | first3 = R. S. | last4 = Pieri | first4 = D. C. | last5 = Schneeberger | first5 = D. M. | year = 1993 | title = Coastal geomorphology of the Martian northern plains | url = | journal = J. Geophys. Res. | volume = 98 | issue = E6| pages = 11061–11078 | doi=10.1029/93je00618 |</ref> <ref>Fairén | first1 = A. G. |display-authors=etal | year = 2003 | title = Episodic flood inundations of the northern plains of Mars | url = http://eprints.ucm.es/10431/1/9-Marte_3.pdf| journal = Icarus | volume = 165 | issue = 1| pages = 53–67 | </ref> <ref> Head | first1 = J. W. |display-authors=etal | year = 1999 | title = Possible ancient oceans on Mars: Evidence from Mars Orbiter Laser Altimeter data | url = | journal = Science | volume = 286 | issue = 5447| pages = 2134–2137 | doi=10.1126/science.286.5447.2134| pmid = 10591640 |</ref> <ref>Parker, T. J., Saunders, R. S. & Schneeberger, D. M. Transitional morphology in west Deuteronilus Mensae, Mars: Implications for modification of the lowland/upland boundary" ''Icarus'' 1989; 82, 111–145</ref> <ref>Carr | first1 = M. H. | last2 = Head | first2 = J. W. | year = 2003 | title = Oceans on Mars: An assessment of the observational evidence and possible fate | url = | journal = J. Geophys. Res. | volume = 108 | issue = E5| page = 5042 |</ref> <ref>Kreslavsky | first1 = M. A. | last2 = Head | first2 = J. W. | year = 2002| title = Fate of outflow channel effluent in the northern lowlands of Mars: The Vastitas Borealis Formation as a sublimation residue from frozen ponded bodies of water | url = | journal = J. Geophys. Res. | volume = 107 | issue = E12| page = 5121 |</ref> <ref>Clifford, S. M. & Parker, T. J. The evolution of the martian hydrosphere: Implications for the fate of a primordial ocean and the current state of the northern plains" ''Icarus'' 2001; 154, 40–79</ref> Much evidence for this ocean has been gathered over several decades. New evidence was published in May 2016. A large team of scientists described how some of the surface in Ismenius Lacus quadrangle was altered by two tsunamis. The tsunamis were caused by asteroids striking the ocean. Both were thought to have been strong enough to create 30 km diameter craters. The first tsunami picked up and carried boulders the size of cars or small houses. The backwash from the wave formed channels by rearranging the boulders. The second came in when the ocean was 300 m lower. The second carried a great deal of ice which was dropped in valleys. Calculations show that the average height of the waves would have been 50 m, but the heights would vary from 10 to 120 meters. So, some large waves would have gone over a 36 story building.<ref>https://www.convertunits.com/from/metre/to/story</ref> Numerical simulations show that in this particular part of the ocean two 30 km in diameter would form every 30 million years. The implication here is that a great northern ocean may have existed for millions of years. One argument against an ocean has been the lack of shoreline features. These features may have been washed away by these tsunami events. The parts of Mars studied in this research are Chryse Planitia and northwestern Arabia Terra. These tsunamis affected some surfaces in the Ismenius Lacus quadrangle and in the [[Mare Acidalium quadrangle]].<ref>Ancient Tsunami Evidence on Mars Reveals Life Potential |date=May 20, 2016 |url=http://astrobiology.com/2016/05/ancient-tsunami-evidence-on-mars-reveals-life-potential.html</ref> <ref>Rodriguez | first1 = J. |display-authors=etal | year = 2016 | title = Tsunami waves extensively resurfaced the shorelines of an early Martian ocean | url = | journal = Scientific Reports | volume = 6 | issue = | page = 25106 | doi=10.1038/srep25106| pmid = 27196957 | pmc = 4872529 |</ref> <ref>| doi=10.1038/srep25106| pmid=27196957| pmc=4872529| title=Tsunami waves extensively resurfaced the shorelines of an early Martian ocean| journal=Scientific Reports| volume=6| pages=25106| year=2016| last1=Rodriguez| first1=J. Alexis P.| last2=Fairén| first2=Alberto G.| last3=Tanaka| first3=Kenneth L.| last4=Zarroca| first4=Mario| last5=Linares| first5=Rogelio| last6=Platz| first6=Thomas| last7=Komatsu| first7=Goro| last8=Miyamoto| first8=Hideaki| last9=Kargel| first9=Jeffrey S.| last10=Yan| first10=Jianguo| last11=Gulick| first11=Virginia| last12=Higuchi| first12=Kana| last13=Baker| first13=Victor R.| last14=Glines| first14=Natalie</ref> <ref>Cornell University. "Ancient tsunami evidence on Mars reveals life potential." ScienceDaily. ScienceDaily, 19 May 2016. https://www.sciencedaily.com/releases/2016/05/160519101756.htm.</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 028537 2270tsunamischannels.jpg|Channels made by the backwash from tsunamis, Tsunamis were probably caused by asteroids striking the ocean.

File:ESP 055714 2270tsunamibackwash.jpg|Possible backwash channels that may have been created by a tsunami, as seen by HiRISE under HiWish program

28537 2270tsunamisboulders.jpg|Boulders that were picked up, carried, and dropped by tsunamis Tsunamis were probably caused by asteroids striking ocean. Boulders in picture are between the size of cars and houses.
Tsunamisstreamlinedp20008931.jpg|Streamlined promontory eroded by tsunami Tsunamis were probably caused by asteroids striking ocean.
File:ESP 054989 2270curvedbands.jpg|Concentric bands that may have been produced by the waves of a tsunami. Image is from HiRISE under the HiWish program.

</gallery>

==Channels (Rivers)==

[[File:ESP 043623 2160meander.jpg|600pxr|Meanders Meanders are commonly formed in old river systems when the water is moving slowly.]]
Meanders They are formed in old river systems when the water is moving slowly.

Many features were probably rivers with water flowing in them billions of years ago. Pictures below show many channels and parts of channels.

The channel shown below goes quite a long distance and has branches. It ends in a depression that may have been a lake at one time. The first picture is a wide angle, taken with CTX; while the second is a close up taken with HiRISE.<ref>http://www.uahirise.org/ESP_039997_2170</ref>

<gallery class="center" widths="380px" heights="360px">

Wikichannelsarabia.jpg|Channels in Arabia, as seen by CTX This channel winds along for a good distance and has branches. It ends in a depression that may have been a lake at one time.

WikiESP 039997 2170channels.jpg|Channel in Arabia, as seen by HiRISE under [[HiWish program]]. This is an enlargement of the previous image that was taken with CTX to give a wide view.

</gallery>

Some places (like below) display a smaller channel within a larger, wider channel or valley. When this occurs it means water went through the region at least two times in the past. This implies that water was not just here once for a short period of time.

<gallery class="center" widths="380px" heights="360px">

ESP 039931 2165channels.jpg|Channel within larger channel The existence of the smaller channel suggests water went through the region at least two times in the past.

ESP 039931 2165close.jpg|Close-up of channel within larger channel The existence of the smaller channel suggests water went through the region at least two times in the past. The black box represents the size of a football field. Some parts of the surface would be difficult to walk on with the many small hills and depressions.
</gallery>

<gallery class="center" widths="380px" heights="360px">

ESP 042924 2195channel.jpg|Channel system that travels through part of a crater

ESP 045548 2155channel.jpg|Channel that cut through a crater rim

42924 2195channelnetwork.jpg|Channel system that travels through part of a crater Note: this is an enlargement of a previous image.

42924 2195channel.jpg|Channel that travels through part of a crater The arrow shows a crater that was eroded by the channel. Note: this is an enlargement of a previous image.

ESP 042502 2200channels.jpg|Channels

ESP 045837 2245channels.jpg|Wide view of channels

45837 2245channel.jpg|Close view of channel

ESP 045838 2130channel.jpg|Channel that has cut through a crater rim

ESP 045850 2210channels.jpg|Wide view of channels, as seen by HiRISE under HiWish program

ESP 045864 2160channels.jpg|Wide view of channels

ESP 045904 2145channelstop.jpg|Channel

ESP 045916 2205channels.jpg|Wide view of channels

45916 2205hanging.jpg|Channel with hanging valley

ESP 046010 2160channels.jpg|Wide view of channels

ESP 046049 2140channels.jpg|Wide view of channels, as seen by HiRISE under HiWish program

ESP 046458 2160channel.jpg|Channel
ESP 050914 2130channel.jpg|Channels

ESP 052761 2170channel.jpg|Channels, as seen by HiRISE under HiWish program

ESP 052774 2160mantle.jpg|Channels, Some parts of the image show mantle and others show no mantle covering the surface.

File:ESP 053420 2160inverted channel.jpg|Possible inverted channel Here after a stream bed got filled with erosion resistant materials, the surrounding, softer landscape eroded away.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 057627 2175channelssapping.jpg|Channels The ends of the channels have shapes that suggest they were formed by the process of sapping.
File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

File:ESP 057560 2180channel.jpg|Channel near ejecta

</gallery>

[[File:ESP 056689 2210channelslowspot.jpg|600pxr|Channels that empty into a low area that could have been a lake, as seen by HiRISE under HiWish program]]

Channels that empty into a possible lake, as seen by HiRISE under [[HiWish program]]

== Lyot Crater ==

The vast northern plains of Mars are generally flat and smooth with few craters. However, a few large craters do stand out. The giant impact crater, Lyot, is easy to see in the northern part of Ismenius Lacus. There are only a very few craters along the far northern latitudes.<ref>U.S. department of the Interior U.S. Geological Survey, Topographic Map of the Eastern Region of Mars M 15M 0/270 2AT, 1991</ref> Lyot Crater is the deepest point in Mars's northern hemisphere.<ref>http://space.com/scienceastronomy/090514--mars-rivers.html</ref> One image below of Lyot Crater Dunes shows a variety of interesting forms: dark dunes, light-toned deposits, and Dust Devil Tracks. Dust devils, which resemble miniature tornados, create tracks by removing a thin, but bright deposit of dust to reveal the darker underlying surface. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will do the trick. Note on units: a micron is an older name for micrometre or micrometer. The width of a single human hair ranges from approximately 20 to 200 microns (μm); hence, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Light-toned materials are an important find because they are widely believed to contain minerals formed in water. Research, published in June 2010, described evidence for liquid water in Lyot crater in the past.

Many channels have been found near Lyot Crater. Research, published in 2017, concluded that the channels were made from water released when the hot ejecta landed on a layer of ice that was 20 to 300 meters thick. Calculations suggest that the ejecta would have had a temperature of at least 250 degrees Fahrenheit. The valleys seem to start from beneath the ejecta near the outer edge of the ejecta. The existence of these channels is unusual because although Mars used to have water in rivers, lakes, and an ocean; channels in Lyot came after we had thought that Mars had dried up. So Mars had flowing water later then we believed.<ref>doi=10.1002/2017GL073821 | volume=44 | issue=11 | title=Extensive Amazonian-aged fluvial channels on Mars: Evaluating the role of Lyot crater in their formation | journal=Geophysical Research Letters | pages=5336–5344 | last1 = Weiss | first1 = David K.| </ref> <ref>Weiss, D., et al. 2017. Extensive Amazonian-aged fluvial channels on Mars: Evaluating the role of Lyot crater in their formation. Geophysical Research Letters: 44, doi:10.1002/2017GL073821.</ref> <ref>http://spaceref.com/mars/hot-rocks-led-to-relatively-recent-water-carved-valleys-on-mars.html</ref>

[[File: ESP 045389 2295lyotchannels.jpg|600pxr|Wide view of channels in Lyot Crater, as seen by HiRISE under [[HiWish program]]]]
Wide view of channels in Lyot Crater, as seen by HiRISE under [[HiWish program]]

<gallery class="center" widths="380px" heights="360px">

ESP 045389 2295lyotchannelstop.jpg|Close view of channels in Lyot Crater
ESP 045389 2295lyotchannelsbottom.jpg|Close view of channels in Lyot Crater, as seen by HiRISE under HiWish program

Image:Lyot Mars Crater Dunes.JPG|Lyot Crater Dunes, as seen by HiRISE. Click on image to see light-toned deposits and dust devil tracks.

File:ESP 053485 2305lyotchannel.jpg|Channel

</gallery>

==Other craters==

Impact craters generally have a rim with ejecta around them; in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter), they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/</ref> The peak is caused by a rebound of the crater floor following the impact.<ref>Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|accessdate=7 March 2011|date=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7}}</ref> Sometimes craters will display layers in their walls. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, craters are useful for showing us what lies deep under the surface.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057007 2190freshcrater.jpg|Fresh crater, as seen by HiRISE under HiWish program This is a young crater because one can easily see the rim and ejecta. They have not yet been eroded.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.

File:ESP 054963 1950craterbench.jpg|Crater with a bench A crater with a bench may be formed from settling of the crater wall or it may be due to impact into something with vastly different types of layers.

File:ESP 056953 2160expandedcraters.jpg|Possible expanded secondary craters, as seen by HiRISE under [[HiWish program]] These craters may have become much wider, as ice left the ground around the rims.<ref>http://www.uahirise.org/epo/nuggets/expanded-secondary.pdf</ref> <ref>Viola, D., et al. 2014. EXPANDED CRATERS IN ARCADIA PLANITIA: EVIDENCE FOR >20 MYR OLD SUBSURFACE ICE. Eighth International Conference on Mars (2014). 1022pdf.</ref>

ESP 053867 2245hotejecta.jpg|Impact crater that may have formed in ice-rich ground, as seen by HiRISE under [[HiWish program]]

File:53867 2245hotejectamargin.jpg |Impact crater that may have formed in ice-rich ground Note that the ejecta seems lower than the surroundings. The hot ejecta may have caused some of the ice to go away; thus lowering the level of the ejecta.

File: ESP 054407 2265pedestal.jpg|Pedestal crater The crater's ejecta protected the underlying ground from eroding.

File:ESP 054830 2260pedestal.jpg|Pedestal crater Mesa on the crater floor formed after the crater.

</gallery>

<gallery class="center" widths="380px" heights="360px">

Image:Cerulli Crater.jpg|Cerulli Crater It looks like a delta was formed as channels bought in debris and dumped then in a lake that was in the crater.

ESP 044506 2245layers.jpg|Group of layers in crater
</gallery>

[[File: Wikiquenissetglaciers.jpg|600pxr|Northeast rim of Quenisset Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Arrows indicate old glaciers.]]
|Northeast rim of Quenisset Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Arrows indicate old glaciers.

== Deltas ==

Researchers have found a number of examples of deltas that formed in Martian lakes. Deltas are major signs that Mars once had a lot of water because deltas usually require deep water over a long period of time to form. In addition, the water level needs to be stable to keep sediment from washing away. Deltas have been found over a wide geographical range. Below, is a pictures of a one in the Ismenius Lacus quadrangle.<ref>Irwin III, R. et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development. Journal of Geophysical Research: 10. E12S15</ref>

<gallery class="center" widths="380px" heights="360px">
Image:Delta in Ismenius Lacus.jpg|Delta in Ismenius Lacus quadrangle, as seen by THEMIS.
</gallery>

== Fretted terrain ==

The Ismenius Lacus quadrangle contains several interesting features such as fretted terrain, parts of which are found in Deuteronilus Mensae and Protonilus Mensae. Fretted terrain contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Many buttes and mesas are present. In fretted terrain the land seems to transition from narrow straight valleys to isolated mesas.<ref>Sharp, R. 1973. Mars Fretted and chaotic terrains. J. Geophys. Res.: 78. 4073–4083</ref> Most of the mesas are surrounded by forms that have been called a variety of names: circum-mesa aprons, debris aprons, rock glaciers, and lobate debris apron (LDA)s. The flat floors here often display many lines or lineations that scientists call lineated valley fill (LVF). These are caused by glacier-like flow. <ref>http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1053.pdf</ref> At first they appeared to resemble rock glaciers on Earth. But scientists could not be sure. Even after the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of fretted terrain, experts could not tell for sure if material was moving or flowing as it would in an ice-rich deposit (glacier). Eventually, proof of their true nature was discovered by radar studies with the [[Mars Reconnaissance Orbiter]] showed that they contain pure water ice covered with a thin layer of rocks that insulated the ice.<ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>Plaut | first1 = J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J. | last4 = Phillips | first4 = R. | last5 = Head | first5 = J. | last6 = Seu | first6 = R. | last7 = Putzig | first7 = N. | last8 = Frigeri | first8 = A. | year = 2009 | title = Radar evidence for ice in lobate debris aprons in the midnorthern latitudes of Mars | url = https://semanticscholar.org/paper/f6b94761e6a276ce6894374ae9bea88fdc3e5e19| journal = Geophys. Res. Lett. | volume = 36| issue = 2| pages = n/a |</ref>

<gallery class="center" widths="380px" heights="360px">

Image:Fretted terrain of Ismenius Lacus taken with MGS.JPG|Fretted terrain of Ismenius Lacus showing flat floored valleys and cliffs. Photo taken with Mars Orbiter Camera (MOC) on the [[Mars Global Surveyor]], under the MOC Public Targeting Program. The white rectangle indicates the position of a high resolution image.

Image:Steep cliff in Ismenius Lacus taken with MGS.JPG|Enlargement of the photo on the left showing cliff. Photo taken with high-resolution camera of Mars Global Surveyor (MGS), under the MOC Public Targeting Program.

Wikictxp13clifflda.jpg|Wide view of mesa with CTX showing cliff face and location of lobate debris apron (LDA).

Wikifretesp 028313 2220cliff.jpg|Enlargement of previous CTX image of mesa. This image shows the cliff face and detail in the LDA. Image taken with HiRISE under HiWish program.

WikiESP 020769 2225fretted.jpg|Close-up of lineated valley fill (LVF) Note: this is an enlargement of the previous CTX image.

File:ESP 057020 2180fretterrain.jpg|Example of frettered terrain Fretted terrain contains many wide, flat-floored valleys.

</gallery>

[[File: Wikifrettedctxp22.jpg|600pxr|Wide CTX view showing mesa and buttes with lobate debris aprons and lineated valley fill around them. ]]
Wide CTX view showing mesa and buttes with lobate debris aprons and lineated valley fill around them. These are typical features of fretted terrain

== Glaciers ==

[[File: ESP 052127 2225flow.jpg|600pxr|Flow, as seen by HiRISE under HiWish program]]
Glacier, as seen by HiRISE under HiWish program

The Ismenius Lacus quadrangle might well be called the land of glaciers. Glaciers formed much of the observable surface in large areas of Mars. Much of the area in high latitudes, especially the Ismenius Lacus quadrangle, is believed to still contain enormous amounts of water ice.<ref>Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7</ref> <ref> Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://www.esa.int/SPECIALS/Mars_Express/SEMBS5V681F_0.html</ref> In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris.<ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> The ice was probably deposited as snowfall during an earlier climate when the poles were tilted more.<ref>Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> It would be difficult to take a hike on the fretted terrain where glaciers are common because the surface is folded, pitted, and often covered with linear striations.<ref>http://www.uahirise.org/ESP_018857_2225</ref> The striations show the direction of movement. Much of this rough texture is due to sublimation of buried ice. The ice goes directly into a gas (this process is called sublimation) and leaves behind an empty space. Overlying material then collapses into the void.<ref>http://hirise.lpl.arizona.edu/PSP_009719_2230</ref> Glaciers are not pure ice; they contain dirt and rocks. At times, they will dump their load of materials into ridges. Such ridges are called moraines.

<gallery class="center" widths="380px" heights="360px">

Image:Evidence of Glaciers in Fretted terrain.JPG|The arrow in the left picture points to a possibly valley carved by a glacier. The image on the right shows the same valley greatly enlarged in a Mars Global Surveyor image.

Wikielephantglacier.jpg|Romer Lake's Elephant Foot Glacier in the Earth's Arctic, as seen by Landsat 8. This picture shows several glaciers that have the same shape as many features on Mars that are believed to also be glaciers.

ESP 045560 2230wideglacier.jpg|Glacier coming out of valley Location is rim of Moreux Crater.

ESP 052179 2215flow.jpg|Flow

ESP 049476 2235glaciers.jpg|Glaciers moving from valleys in a mesa

ESP 046021 2175glaciers.jpg|Two glaciers interacting The one on the left is more recent and is flowing on top of the other one.

ESP 049410 2245flow.jpg|Glacier interacting with an obstacle

46075 2200glacier.jpg|Glacier flowing out of valley

ESP 046734 2270ridge.jpg|Ridge that is probably from an old glacier

ESP 046061 2190lvf.jpg|Lineated valley fill, as seen by HiRISE under [[HiWish program]].

46061 2190closelvf..jpg|Close view of Lineated valley fill

ESP 046061 2190closebrains.jpg|Close, color view of Lineated valley fill

ESP 046840 2130lvf.jpg|Lineated valley fill in valley

ESP 050137 2185lvf.jpg|Lineated valley fill in valley Linear valley fill is ice covered by debris.

ESP 050137 2185lvfclosecolor.jpg|Close, color view of lineated valley fill

Image:Lobate feature with hiwish.JPG|Probable glacier Radar studies have found that it is made up of almost completely pure ice. It appears to be moving from the high ground (a mesa) on the right.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it. One of the glaciers is seen in greater detail in the next two images from HiRISE.

Image:Wide view of glacier showing image field.JPG|Glacier as seen by HiRISE under the HiWish program. Area in rectangle is enlarged in the next photo. Zone of accumulation of snow at the top. Glacier is moving down valley, then spreading out on plain. Evidence for flow comes from the many lines on surface. Location is in Protonilus Mensae.

Image:Glacier close up with hirise.JPG|Enlargement of area in rectangle of the previous image. On Earth the ridge would be called the terminal moraine of an alpine glacier.

Image:ESP 028352 2245glacier.jpg|Remains of a glacier after ice has disappeared

Wikildaf03 036777 2287.jpg|Lobate debris aprons (LDAs) around a mesa, as seen by CTX Mesa and LDAs are labeled so one can see their relationship. Radar studies have determined that LDAs contain ice; therefore these can be important for future colonists of Mars.

Wikifrettedctxpo5.jpg|Wide CTX view of mesa showing lobate debris apron (LDA) and lineated valley fill. Both are believed to be debris-covered glaciers.

</gallery>

[[File: Wikifretesp 027639 2210lda.jpg|600pxr|Close-up of lobate debris apron from the previous CTX image of a mesa. Image shows open-cell brain terrain and closed-cell brain terrain, which is more common. Closed-cell brain terrain is thought to hold a core of ice.]]
Close-up of lobate debris apron from the previous CTX image of a mesa. Image shows open-cell brain terrain and closed-cell brain terrain, which is more common. Closed-cell brain terrain is thought to hold a core of ice.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057389 2195flow.jpg|Lobate debris apron around mesa

File:ESP 057389 2195lda.jpg|Close view of lobate debris apron around mesa Brain terrain is visible.

ESP 044874 2205glaciers.jpg|Glaciers moving in two different valleys

ESP 045085 2205flow.jpg|Wide view of flow moving down valley

45085 2205close.jpg|Close view of part of glacier Box shows size of football field.

ESP 051177 2230flowmantle.jpg|Flow and mantle Mantle appears as layers against the cliff face.

</gallery>

<gallery class="center" widths="380px" heights="360px">

ESP 049555 2225tongue.jpg|Wide view of tongue-shaped glacier and lineated valley fill

49555 2225tongue.jpg|Tongue-shaped glacier Note: this is an enlargement of the previous image
49555 2225tongueclose.jpg|Close view of tongue-shaped glacier Surface is broken up into cubes.

</gallery>

==Latitude dependent mantle==

Much of the Martian surface is covered with a thick ice-rich, mantle layer that has fallen from the sky a number of times in the past.<ref>Hecht | first1 = M | year = 2002 | title = Metastability of water on Mars | url = | journal = Icarus | volume = 156 | issue = 2| pages = 373–386 | doi=10.1006/icar.2001.6794 |</ref> <ref>Mustard | first1 = J. |display-authors=etal | year = 2001 | title = Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice | url = | journal = Nature | volume = 412 | issue = 6845| pages = 411–414 |</ref> <ref>Pollack | first1 = J. | last2 = Colburn | first2 = D. | last3 = Flaser | first3 = F. | last4 = Kahn | first4 = R. | last5 = Carson | first5 = C. | last6 = Pidek | first6 = D. | year = 1979 | title = Properties and effects of dust suspended in the martian atmosphere | url = | journal = J. Geophys. Res. | volume = 84 | issue = | pages = 2929–2945 | doi=10.1029/jb084ib06p02929 |</ref>

<gallery class="center" widths="380px" heights="360px">
45085 2205mantlethickness.jpg|Close view of mantle Arrows show craters along edge which highlight the thickness of mantle.
45917 2220gulliesmantle.jpg|Close view that displays the thickness of mantle.
ESP 046444 2225flows.jpg|Mantle and flow A part of the image showing the mantle is enlarged in the next image.
46444 2225mantle.jpg|Mantle, as seen by HiRISE under [[HiWish program]]
51177 2230mantle.jpg|Close view of mantle

51230 2200mantle.jpg|Close view of mantle, as seen by HiRISE under HiWish program

ESP 052774 2160mantleclosecolor.jpg|Color view of mantle Some parts of the image are covered with mantle; other parts are not.

File:ESP 057480 2205mantlelayerstop.jpg|Mantle layers lying against steep slopes. Each layer represents a change in the climate of Mars.

File:ESP 057480 2205pyramid.jpg|Mantle layers Mantle layers seem to be forming a group of dipping layers.
</gallery>

==Climate change caused ice-rich features==

Many features on Mars, especially ones found in the Ismenius Lacus quadrangle, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees<ref>Touma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref> Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Large changes in the tilt explains many ice-rich features on Mars.

Studies have shown that when the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles.<ref>Levy | first1 = J. | last2 = Head | first2 = J. | last3 = Marchant | first3 = D. | last4 = Kowalewski | first4 = D. | year = 2008 | title = Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution | url = | journal = Geophys. Res. Lett. | volume = 35| issue = 4| pages = L04202 | doi = 10.1029/2007GL032813 |</ref> Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Calculations suggest this material will concentrate in the mid-latitudes, like those of the Ismenius Lacus quadrangle.<ref> Levy | first1 = J. | last2 = Head | first2 = J. | last3 = Marchant | first3 = D. | year = 2009a | title = Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations | url = | journal = J. Geophys. Res. | volume = 114| issue = E1| pages = E01007 | doi = 10.1029/2008JE003273 |</ref> <ref>Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111–131</ref> General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found.<ref>Laskar, J.; Correia, A.; Gastineau, M.; Joutel, F.; Levrard, B.; Robutel, P. (2004). "Long term evolution and chaotic diffusion of the insolation quantities of Mars". Icarus. 170 (2): 343–364.</ref> When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust.<ref>Mellon | first1 = M. | last2 = Jakosky | first2 = B. | year = 1995 | title = The distribution and behavior of Martian ground ice during past and present epochs | url = https://semanticscholar.org/paper/815bfd93bdb19325e03e08556d145fa470112e4e| journal = J. Geophys. Res. | volume = 100 | issue = E6| pages = 11781–11799 |</ref> <ref>Schorghofer | first1 = N | year = 2007 | title = Dynamics of ice ages on Mars | url = | journal = Nature | volume = 449 | issue = 7159| pages = 192–194 | doi=10.1038/nature06082| pmid = 17851518 |</ref> The lag deposit caps the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind.<ref>Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> Note, that the smooth surface mantle layer probably represents only relative recent material.

==Upper Plains Unit==

Remnants of a 50–100 meter thick mantling, called the Upper Plains Unit, has been discovered in the mid-latitudes of Mars. It was first investigated in the Deuteronilus Mensae region, but it occurs in other places as well. The remnants consist of sets of dipping layers in craters and along mesas.<ref>http://www.uahirise.org/ESP_048897_2125</ref> <ref>Carr | first1 = M | year = 2001 | title = Mars Global Surveyor observations of martian fretted terrain | url = | journal = J. Geophys. Res. | volume = 106 | issue = E10| pages = 23571–23593 | doi=10.1029/2000je001316 |</ref> Sets of dipping layers may be of various sizes and shapes—some look like Aztec pyramids from Central America.

<gallery class="center" widths="380px" heights="360px">

47578 2245ctxP04 002481 2241.jpg|Wide view showing contact between upper plains unit lower part of picture and a lower unit, as seen by CTX

ESP 047578 2245contact.jpg|Contact Upper plains unit on the left is breaking up. A lower unit exists on the right side of picture.

47578 2245contactclose.jpg|Close view of contact Picture shows details of how upper plains material is breaking. The formation of many fractures seems to proceed the break up.

</gallery>

<gallery class="center" widths="380px" heights="360px">
ESP 048870 2250contact.jpg|Wide view of upper plains unit eroding into hollows Parts of this image are enlarged in following images.

48870 2250contact.jpg|Close view of upper plain unit eroding into hollows Break up begins with cracks on the surface that expand as more and more ice disappears from the ground.

48870 2250contactclose.jpg|Close view of hollows
</gallery>

Associated with this unit are dipping layers. However, these groups of layers are found in many locations around the planet. They may be mostly caused by the build up and later erosion of layers of mantle. Mantle has been built up from many climate changes. These "dipping layers" occur mainly in protected spots--like inside craters or against the steep slope of a mesa or the walls of a depression.

<gallery class="center" widths="380px" heights="360px">

ESP 045613 2230pyramids.jpg|Wide view of dipping layers along mesa walls

45613 2230pyramids.jpg|Close view of dipping layers along a mesa wall

ESP 035684 2160pyramidsbrains.jpg|Dipping layers

ESP 036790 2200pyramids.jpg|Dipping layers in a crater

P1010377redrocksfall.jpg|Layered feature in Red Rocks Park, Colorado. This has a different origin than ones on Mars, but it has a similar shape. Features in Red Rocks region were caused by uplift of mountains.

46180 2225brains.jpg|Close view of dipping layers Brain terrain is also visible in the image.

</gallery>

This unit also degrades into "brain terrain." Brain terrain is a region of maze-like ridges 3–5 meters high. The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.

<gallery class="center" widths="380px" heights="360px">

45507 2200brains.jpg|Brain terrain, as seen by HiRISE under [[HiWish program]]

45917 2220brainsopenclosed.jpg|Open and closed brain terrain with labels The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.

ESP 042105 2235brainsforming.jpg|Brain terrain being formed from a thicker layer Arrows show the thicker unit breaking up into small cells.

46075 2200brainsforming.jpg|Brain terrain being formed Arrows point to locations where the brain terrain is starting to form.

45349 2235brainsforming3.jpg|Brain terrain being formed, as seen by HiRISE under HiWish program Note: this is an enlargement of a previous image.

45349 2235brainsforming2.jpg|Brain terrain being formed Note: this is an enlargement of a previous image using HiView. Arrows indicate spots where brain terrain is beginning to form.

ESP 045363 2190brain.jpg|Wide view of brain terrain being formed, as seen by HiRISE under HiWish program

46075 2200brainsside.jpg|Brain terrain with a view from the side Arrow shows where a side view of the brain terrain is visible.

</gallery>

Some regions of the upper plains unit display large fractures and troughs with raised rims; such regions are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Stress is suggested to initiate the fracture process since ribbed upper plains are common when debris aprons come together or near the edge of debris aprons—such sites would generate compressional stresses. Cracks exposed more surfaces, and consequently more ice in the material sublimates into the planet's thin atmosphere. Eventually, small cracks become large canyons or troughs.

<gallery class="center" widths="380px" heights="360px">

ESP 028339 2245headarticle.jpg|Well developed ribbed upper plains material. These start with small cracks that expand as ice sublimates from the surfaces of the crack.

ESP 042765 2245cracks.jpg|Small and large cracks The small cracks to the left will enlarge to become much larger due to sublimation of ground ice. A crack exposes more surface area, hence greatly increases sublimation in the thin Martian air.

42765 2245close.jpg|Close-up of canyons from previous image

</gallery>

[[File: ESP 042198 2235pyramid.jpg|600pxr|View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain.]]
View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain.

<gallery class="center" widths="380px" heights="360px">
ESP 035011 2240pyramidshead.jpg|Dipping layers Also, Ribbed Upper plains material is visible in the upper right of the picture. It is forming from the upper plains unit, and in turn is being eroded into brain terrain.<ref>http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.722.2437&rep=rep1&type=pdf</ref> <Baker, D and J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains
in Deuteronilus Mensae, Mars: Implications for the record
of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

45402 2230cracksmesas.jpg|Ribbed terrain being formed from upper plains unit, as seen by HiRISE under HiWish program Formation begins with cracks that enhance sublimation. Box shows the size of football field.

45837 2245turtles.jpg|Surface breaking down, as ice is removed Box shows size of football field.

ESP 046365 2245ribbed.jpg|Wide view of terrain caused by ice leaving the ground
ESP 046365 2245middle.jpg|Close view of terrain caused by ice leaving the ground

ESP 046325 2225hollowa.jpg|Wide view of terrain caused by ice leaving the ground

</gallery>

[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of terrain caused by ice leaving the ground Box shows size of football field.]]
Close view of terrain caused by ice leaving the ground Box shows size of football field.

Small cracks often contain small pits and chains of pits; these are thought to be from sublimation of ice in the ground.<ref>Morgenstern, A., et al. 2007</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269–288.</ref> Large areas of the Martian surface are loaded with ice that is protected by a meters thick layer of dust and other material. However, if cracks appear, a fresh surface will expose ice to the thin atmosphere.<ref> Mangold | first1 = N | year = 2003 | title = Geomorphic analysis of lobate debris aprons on Mars at Mars Orbiter Camera scale: Evidence for ice sublimation initiated by fractures | url = | journal = J. Geophys. Res. | volume = 108 | issue = E4| page = 8021 | doi=10.1029/2002je001885 </ref> <ref>Levy, J. et al. 2009. Concentric</ref> In a short time, the ice will disappear into the cold, thin atmosphere in a process called "sublimation." Dry ice behaves in a similar fashion on the Earth. On Mars sublimation has been observed when the Phoenix lander uncovered chunks of ice that disappeared in a few days.<ref>http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080619.html Bright Chunks at ''Phoenix'' Lander's Mars Site Must Have Been Ice – Official NASA press release (19.06.2008)</ref> <ref>http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080619.html</ref> In addition, HiRISE has seen fresh craters with ice at the bottom. After a time, HiRISE saw the ice deposit disappear.<ref> Byrne | first1 = S. |display-authors=etal | year = 2009 | title = Distribution of Mid-Latitude Ground Ice on Mars from New Impact Craters | url = | journal = Science | volume = 329 | issue = 5948| pages = 1674–1676 | doi = 10.1126/science.1175307 | </ref>

<gallery class="center" widths="380px" heights="360px">

</gallery>

The upper plains unit is thought to have fallen from the sky. It drapes various surfaces, since it fell evenly onto all surfaces. As is the case for other mantle deposits, the upper plains unit has layers, is fine-grained, and is ice-rich. It is widespread; it does not seem to have a point source. The surface appearance of some regions of Mars is due to how this unit has degraded. It is a major cause of the surface appearance of lobate debris aprons.<ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269–288.</ref> The layering of the upper plains mantling unit and other mantling units are believed to be caused by major changes in the planet's climate. Models predict that the obliquity or tilt of the rotational axis has varied from its present 25 degrees to maybe over 80 degrees over geological time. Periods of high tilt will cause the ice in the polar caps to be redistributed and change the amount of dust in the atmosphere.<ref>Head, J. et al. 2003.</ref> <ref>Madeleine, et al. 2014.</ref> <ref>Schon |display-authors=etal | year = 2009 | title = A recent ice age on Mars: Evidence for climate oscillations from regional layering in mid-latitude mantling deposits | url = | journal = Geophys. Res. Lett. | volume = 36 | issue = 15| page = L15202 | bibcode = 2009GeoRL..3615202S|</ref>

== Pits and cracks ==

Some places in the Ismenius Lacus quadrangle display large numbers of cracks and pits. It is widely believed that these are the result of ground ice sublimating (changing directly from a solid to a gas). After the ice leaves, the ground collapses in the shape of pits and cracks. The pits may come first. When enough pits form, they unite to form cracks.<ref>http://hirise.lpl.arizona.edu/PSP_009719_2230 |title=HiRISE | Fretted Terrain Valley Traverse (PSP_009719_2230) |publisher=Hirise.lpl.arizona.edu |</ref>

<gallery class="center" widths="380px" heights="360px">

Image:CTX Context Image of Pits.JPG|CTX Image in Protonilus Mensae, showing location of next image.

Image:Pits in Protonilus Mensae.JPG|Pits in Protonilus Mensae, as seen by HiRISE, under the [[HiWish program]].

</gallery>

[[File: 49700 2250pitsclose.jpg|600pxr|Close view of lines of pits Box shows size of football field. Pits may be up to around 50 meters across.]]

Close view of lines of pits Box shows size of football field. Pits may be up to around 50 meters across.

<gallery class="center" widths="380px" heights="360px">
49700 2250polygons.jpg|Close view of pits and polygons, as seen by HiRISE Pits seem to occur in low spots between polygons.

52588 2210pits.jpg|Close view of pits, as seen by HiRISE, under the HiWish program
</gallery>

==Mesas formed by ground collapse==

<gallery class="center" widths="380px" heights="360px">
ESP 043201 2160blocks.jpg|Group of mesas Oval box contains mesas that may have moved apart.

43201 2160blocks.jpg|Enlarged view of a group of mesas One surface is forming square shapes.

</gallery>

==Polygonal patterned ground==

Polygonal, patterned ground is quite common in some regions of Mars.<ref>http://www.diss.fu-berlin.de/diss/servlets/MCRFileNodeServlet/FUDISS_derivate_000000003198/16_ColdClimateLandforms-13-utopia.pdf?hosts=</ref> <ref> Kostama | first1 = V.-P. | last2 = Kreslavsky | first2 = Head | year = 2006 | title = Recent high-latitude icy mantle in the northern plains of Mars: Characteristics and ages of emplacement | url = | journal = Geophys. Res. Lett. | volume = 33 | issue = 11| page = L11201 |</ref> <ref> Malin | first1 = M. | last2 = Edgett | first2 = K. | year = 2001 | title = Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission | url = https://semanticscholar.org/paper/ad350109a111b6425140583455c222a0529f45c6| journal = J. Geophys. Res. | volume = 106 | issue = E10| pages = 23429–23540 |</ref> <ref>Milliken | first1 = R. |display-authors=etal | year = 2003 | title = Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images | url = https://semanticscholar.org/paper/a822f14644d2294b948e101be2f294ac33b57ec3| journal = J. Geophys. Res. | volume = 108 | issue = E6| page = E6 | doi = 10.1029/2002JE002005 |</ref> <ref>Mangold | first1 = N | year = 2005 | title = High latitude patterned grounds on Mars: Classification, distribution and climatic control | url = | journal = Icarus | volume = 174 | issue = 2| pages = 336–359 | doi=10.1016/j.icarus.2004.07.030 |</ref> <ref>Kreslavsky | first1 = M. | last2 = Head | first2 = J. | year = 2000 | title = Kilometer-scale roughness on Mars: Results from MOLA data analysis | url = | journal = J. Geophys. Res. | volume = 105 | issue = E11| pages = 26695–26712 | doi=10.1029/2000je001259 |</ref> <ref>Seibert | first1 = N. | last2 = Kargel | first2 = J. | year = 2001 | title = Small-scale martian polygonal terrain: Implications or liquid surface water | url = | journal = Geophys. Res. Lett. | volume = 28 | issue = 5| pages = 899–902 </ref> It is commonly believed to be a marker for ice-rich ground because these shapes are common on the Earth in cold regions with lots of ice in the ground.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction.<ref>https://www.uahirise.org/ESP_066782_1110</ref>

Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer, called latitude dependent mantle, that fell from the sky when the climate was different.<ref>Kreslavsky, M.A., Head, J.W., 2002. High-latitude Recent Surface Mantle on Mars: New Results from MOLA and MOC. European Geophysical Society XXVII, Nice.</ref> <ref>Head | first1 = J.W. | last2 = Mustard | first2 = J.F. | last3 = Kreslavsky | first3 = M.A. | last4 = Milliken | first4 = R.E. | last5 = Marchant | first5 = D.R. | year = 2003 | title = Recent ice ages on Mars | url = | journal = Nature | volume = 426 | issue = 6968| pages = 797–802 | doi=10.1038/nature02114| pmid = 14685228 |</ref>

<gallery class="center" widths="380px" heights="360px">

43899 2265closecrack.jpg|Close-up of field of high center polygons with scale Note: the black box is the size of a football field.

43899 2265highcenterpolygonsclose2.jpg|Close-up of high center polygons Note: the black box is the size of a football field.

</gallery>

[[File: 45363 2190lowcenterpolygons.jpg|600pxr|Low center polygons]]
Low center polygons

<gallery class="center" widths="380px" heights="360px">

ESP 047275 2255hcpolygons.jpg|Wide view of high center polygons
47275 2255hcpolygonsclose.jpg|Close view of high center polygons Centers of polygons are labeled.

ESP 052101 2260largepolygons.jpg|Large polygons
</gallery>

==Gullies==

Gullies were thought for a time to have been caused by recent flows of liquid water. However, further study suggests they are formed today by chunks of dry ice moving down steep slopes.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |date=July 10, 2014 |work=[[NASA]] |accessdate=July 10, 2014 </ref>

<gallery class="center" widths="380px" heights="360px">

ESP 044122 2335gullies.jpg|Gullies in crater, as seen by HiRISE under HiWish program

45561 2310gulliesclose.jpg|Close view of channel in gully showing streamlined forms
ESP 045917 2220gulliespyramids.jpg|Gullies
45917 2220gulliesclose.jpg|Close view of gullies, as seen by HiRISE under HiWish program
45917 2220gulliespolygons.jpg|Close view of gullies
</gallery>

==Layered features==

<gallery class="center" widths="380px" heights="360px">
ESP 046443 2165layers.jpg|Layers
46443 2165mesa.jpg|Layered mesas

52471 1835layers.jpg|Close view of layers
</gallery>

==Dunes==

[[File: ESP 055095 2170dunes.jpg|600pxr|Wide view of a field of dunes]]
Wide view of a field of dunes

Sand dunes have been found in many places on Mars. The presence of dunes shows that the planet has an atmosphere with wind, for dunes require wind to pile up the sand. Most dunes on Mars are black because of the weathering of the volcanic rock basalt.<ref>http://hirise.lpl.arizona.edu/ESP_016459_1830</ref> <ref>Michael H. Carr|title=The surface of Mars|url=https://books.google.com/books?id=uLHlJ6sjohwC|accessdate=21 March 2011|year=2006|publisher=Cambridge University Press|isbn=978-0-521-87201-0</ref> Black sand can be found on Earth on Hawaii and on some tropical South Pacific islands.<ref>https://www.desertusa.com/desert-activity/sand-dune-wind1.html</ref>
Sand is common on Mars due to the old age of the surface that has allowed rocks to erode into sand. Dunes on Mars have been observed to move many meters.<ref>https://www.youtube.com/watch?v=ur_TeOs3S64</ref> <ref>https://uanews.arizona.edu/story/the-flowing-sands-of-mars</ref>
In this process, sand moves up the windward side and then falls down the leeward side of the dune, thus caused the dune to go toward the leeward side (or slip face).<ref>Namowitz, S., Stone, D. 1975. earth science the world we live in. American Book Company. New York.</ref>
When images are enlarged, some dunes on Mars display ripples on their surfaces.<ref>https://www.jpl.nasa.gov/news/news.php?feature=6551</ref>

<gallery class="center" widths="380px" heights="360px">
ESP 044861 2225dunes.jpg|Wide view of dunes in Moreux Crater

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:55095 2170dunelinecolor.jpg|Close, color view of dunes, as seen by HiRISE under [[HiWish program]]

File:55095 2170dunelinecolor2.jpg|Close, color view of dunes

File:55095 2170dunelinecolor3.jpg|Close, color view of a dune

</gallery>

==Ring mold craters==

Ring Mold Craters are a kind of Impact crater that looks like a ring mold used in baking. They are believed to be caused by an impact into ice. The ice is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." Impacts into ice, warm the ice, and cause it to flow into the ring mold shape.

<gallery class="center" widths="380px" heights="360px">
ESP 037622 2200ringmolds.jpg|Ring mold craters on floor of a crater
ESP 037622 2200ringmoldfield.jpg|Ring mold craters of various sizes on floor of a crater
</gallery>

[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

<gallery class="center" widths="380px" heights="360px">

51139 2160ringmold.jpg|Close view of Ring-mold crater, as seen by HiRISE under [[HiWish program]]

</gallery>

<gallery class="center" widths="380px" heights="360px">

52260 2165ringmold.jpg|Ring-mold craters, as seen by HiRISE under HiWish program
52260 2165ringmoldclose.jpg|Close view of Ring-mold craters and brain terrain
</gallery>

<gallery class="center" widths="380px" heights="360px">
52602 2140ringmold.jpg|Close view of Ring-mold craters and brain terrain
52602 2140ringmoldclose.jpg|Close view of Ring-mold craters and brain terrain Rectangle shows size of football field for scale.

</gallery>

==Volcanoes under ice==

There is evidence that volcanoes sometimes erupt under ice, as they do on Earth at times. <ref>https://www.uahirise.org/ESP_071541_2200</ref> What seems to happen is that much ice melts, the water escapes, and then the surface cracks and collapses.<ref>Smellie, J., B. Edwards. 2016. Glaciovolcanism on Earth and Mars. Cambridge University Press.</ref> These exhibit concentric fractures and large pieces of ground that seemed to have been pulled apart. Sites like this may have recently had held liquid water, hence they may be fruitful places to search for evidence of life.<ref>Levy, J. 2017">Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185–194.</ref> <ref>University of Texas at Austin. "A funnel on Mars could be a place to look for life." ScienceDaily. ScienceDaily, 10 November 2016. <https://www.sciencedaily.com/releases/2016/11/161110125408.htm>.</ref>

<gallery class="center" widths="380px" heights="360px">
Image:25755concentriccracks.jpg|Large group of concentric cracks Location is Ismenius Lacus quadrangle. Cracks were formed by a volcano under ice.<ref>Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185–194.</ref>

25755 2200collapse.jpg|Tilted layers formed when ground collapsed, as seen by HiRISE, under [[HiWish program]]
25755 2200tiltedlayers.jpg|Tilted layers formed from ground collapse
25755 2200blocksforming.jpg|Mesas breaking up into blocks

</gallery>

<gallery class="center" widths="380px" heights="360px">

52049 2145cratercracks.jpg|Depression forming from a possible subsurface loss of material
</gallery>

==Mesas formed by ground collapse==

<gallery class="center" widths="380px" heights="360px">
ESP 043201 2160blocks.jpg|Group of mesas, as seen by HiRISE under HiWish program Oval box contains mesas that may have moved apart.

43201 2160blocksbreakup.jpg|Mesas breaking up forming straight edges, as seen by HiRISE under HiWish program
</gallery>

==Fractures forming blocks==

In places large fractures break up surfaces. Sometimes straight edges are formed and large cubes are created by the fractures.

<gallery class="center" widths="380px" heights="360px">
44757 2185wide.jpg|Wide view of mesas that are forming fractures
44757 2185zoom.jpg|Enlarged view of a part of previous image The rectangle represents the size of a football field.
44757 2185closeleft.jpg|Close-up of blocks being formed

44757 2185blocks.jpg|Close-up of blocks being formed The rectangle represents the size of a football field, so blocks are the size of buildings.
44757 2185cosefractures.jpg|Close-up of blocks being formed Many long fractures are visible on the surface.

ESP 045377 2170odd.jpg|Wide view showing light-toned feature that is breaking into blocks

45377 2170blocks.jpg|Close view showing blocks being formed Note: this is an enlargement of the previous image. Box represents the size of a football field.

File:55517 2170rocksbreakingcolor.jpg|Color view of rocks breaking apart
</gallery>

==Exhumed craters==

Some features on Mars seem to be in the process of being uncovered. So, the thought is that they formed, were covered over, and now are being exhumed as material is being taken away by erosion. These features are quite noticeable with craters. When a crater forms, it will destroy what's under it and leave a rim and ejecta. In the example below, only part of the crater is visible. If the crater came after the layered feature, the impact that formed the crater would have removed part of the layered structure.

<gallery class="center" widths="380px" heights="360px">
File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.

</gallery>

==Mounds==

<gallery class="center" widths="380px" heights="360px">
ESP 052339 2275mounds.jpg|Wide view of field of mounds near pedestal crater
ESP 052339 2275moundsclosecolor.jpg|Close, color view of mounds, as seen by HiRISE under HiWish program

File:ESP 053260 2185mounds.jpg|Row of mounds Arrows point to some of the mounds.
File:ESP 055978 2270mounds.jpg|Lines of mounds
</gallery>

==Landslide==

<gallery class="center" widths="380px" heights="360px">

File:ESP 057191 2150landslide.jpg|Landslide, as seen by HiRISE under HiWish program

File:57191 2150landslideclose.jpg|Close view of landslide

ESP 047262 2145landslide.jpg|Landslides

</gallery>

==Other images from Ismenius Lacus quadrangle==

[[File:56663 2200brains.jpg|600pxr|Close view of honeycomb shapes and brain terrain, as seen by HiRISE under [[HiWish program]]]]
Close view of honeycomb shapes and brain terrain, as seen by HiRISE under [[HiWish program]]

<gallery class="center" widths="380px" heights="360px">

Image:25781pitsmediumview.jpg|Field of pits

43201 2160dikes.jpg|Possible dike

45377 2170troughinsidetroughs.jpg|Pits and troughs Pits may have formed from water/ice leaving the ground.

ESP 045415 2220boulders.jpg|Boulders

ESP 052932 2255mudvolcanoes.jpg|Possible mud volcanoes

File:57825 2275conesclose.jpg|Close view of cones

51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

File:ESP 054870 2270snake.jpg|Ridge This ridge may be an esker. Eskers began as streams under glaciers.

</gallery>

[[File:ESP 053893 2130ridges.jpg|600pxr|Ridges]]
Ridges

==See also==

*[[Dark slope streaks]]
*[[Geography of Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[HiWish program]]
*[[How are features on Mars Named?]]
*[[Glaciers on Mars]]
*[[Layers on Mars]]
*[[Mars Global Surveyor]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Oceans on Mars]]
*[[Periodic climate changes on Mars]]
*[[Rivers on Mars]]
*[[Sublimation landscapes on Mars]]

== External links ==

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]

==References==
{{reflist|colwidth=30em}}

Martian features that are signs of water ice

2023-03-04T22:52:52Z

Suitupandshowup: /* Pingos */ added image

How to find water on Mars

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

INTRODUCTION
Finding sources of water on Mars is necessary for future colonists. Studies with orbiting spacecraft have provided a great deal of evidence pointing to where water ice is located. Decades ago, theoretical studies showed that ice could exist under a cover of material that needed to be very thick near the equator, but at higher latitudes could be right under the surface.<ref>Rossbacher, L and S. Judson. 1981. Ground Ice on Mars: Inventory, Distribution, and Resulting Landforms. Icarus: 45, 39-59.</ref> Instruments onboard the Mars Odyssey measured the depth to this ice layer all over the planet.

[[Image: Mars Odyssey spacecraft model.png |thumb|200px|left|Artist view of Mars Odyssey]]

These measurements closely matched what the early theories had predicted. The Phoenix lander’s rockets blew away a thin cover of dirt to reveal the top of an ice layer.<ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> Also, by way of frequent pictures from Phoenix, we watched chunks of ice sublimate into the atmosphere. On Mars today, any exposed ice changes directly into a gas and mixes with the atmosphere in the process called [[sublimation]].

[[Image: Phoenix landing.jpg |thumb|200px|right|Artist view of Phoenix landing]]

[[File:PIA10741 Possible Ice Below Phoenix.jpg|thumb|200px|right|View under Phoenix spacecraft Bright regions are probably top of an ice sheet.]]

We also observed this process through HiRISE photos of ice first being exposed in new craters and then disappearing.

[[Image: Iceincraterscomparison.jpg|thumb|200px|left|Ice in crater Location: 43.286° N and 164.213°E]]

Thanks to the many satellites going around Mars with advanced instruments, we now have a list of features that are signs of easily obtainable underground ice. The shapes of some landscapes are similar to those on the earth that we know contain ice. Radar studies with the SHAllow RADar instrument (SHARD) on board the Mars Reconnaissance Orbiter ( MRO) have found large deposits of ice under relatively thin layers of debris cover for some of these features .<ref> Plaut, J., A. Safaeinili, J. Holt, R. Phillips, J. Head, J., R. Seu, N. Putzig, A. Frigeri. 2009. Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars. Geophys. Res. Lett. 36. doi:10.1029/2008GL036379.</ref> <ref> Holt, J., A. Safaeinili, J. Plaut, J. Head, R. Phillips, R. Seu, S. Kempf, P. Choudhary, D. Young, N. Putzig, D. Biccari, Y. Gim. 2008. Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars. Science 322. doi:10.1126/science.1164246 </ref> The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument onboard MRO has been able to detect spectroscopic signs of water in certain landscapes. The ice caps contain vast resovors of ice, but traveling to the poles is a long way to go for this precious resource. This article will display many landscapes that probably contain easily obtained water ice that are much closer than the poles.

[[Image: Mars Reconnaissance Orbiter spacecraft model.png |thumb|200px|right|Artist view of Mars Reconnaissance Orbiter ]]
[[Image: MRO CRISM prelaunch 2.jpg |thumb|200px|left|CRISM—identifies ice and other minerals]]

===Triangular depressions===

In early 2018, researchers released information about large amounts of ice found under only a few meters of soil. These places are easily seen as triangular depressions with one steep wall that faces the pole.<ref>https://www.uahirise.org/ESP_074914_1225</ref> These exposed ice sheets as thick as 100 meters were discovered by using instruments on board the Mars Reconnaissance Orbiter (MRO). Much evidence of underground ice in vast regions of Mars has already been found by past studies, but this study found that the ice was only covered by a layer of about 1 or 2 meters thick of Martian soil.<ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> Shane Byrne, one of the co-authors remarked that future colonists of the Red Planet would be able to gather up ice with just a bucket and shovel.<ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref> The fact that water-ice makes up the layers was confirmed by Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the [[Mars Reconnaissance Orbiter]] (MRO). The spectra gathered by CRISM showed strong signals of water.<ref>Colin M. Dundas, et al. ''Science'', 12 January 2018. Vol. 359, Issue 6372, pp. 199-201.</ref>

The sites are at latitudes from about 55 to 58 degrees north and south of the equator, suggesting that there is shallow ground ice under roughly a third of the Martian surface.<ref> Steep Slopes on Mars Reveal Structure of Buried Ice. NASA Press Release. 11 January 2018.</ref>

<gallery class="center" widths="380px" heights="360px">
ESP 045290 2350triangulardepression.jpg|Wide view of triangular depressions with ice under thin cover
45290 2350icelayerscloseer.jpg|Close view of depression, as seen by HiRISE under HiWish program Arrows indicate where there is a very thin, 1-2 meter covering on what is believed to be ice.<ref>https://www.uahirise.org/ESP_071573_2350</ref>
</gallery>

== Scalloped topography==

[[Image: ESP 037461 2255scallopstop.jpg|600pxr|Scalloped ground, as seen by HiRISE under HiWish program]]

Scalloped ground, as seen by HiRISE under HiWish program

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is particularly prominent in the region of Utopia Planitia<ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> in the northern hemisphere and in the region of Peneus and Amphitrites Patera in the southern hemisphere.<ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref> Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. A typical scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> This topographic asymmetry is probably due to differences in insolation. Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation. Sublimation is where a solid changes directly into a gas without going through a liquid phase. Dry ice on the Earth changes directly to a gas; but usually on Earth, ice will melt first to form a liquid phase before turning into a gas. This process is common in the thin Martian atmosphere.
In the fall of 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars.<ref>http://www.space.com/34811-mars-ice-more-water-than-lake-superior.html</ref> The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.<ref> "Lake of frozen water the size of New Mexico found on Mars – NASA". The Register. November 22, 2016 name="NASA-20161122"</ref> The volume of water ice in the region were based on measurements from the ground-penetrating radar instrument on Mars Reconnaissance Orbiter, called SHARAD. From the data obtained from SHARAD, a dielectric constant was determined. The dielectric constant value was consistent with a large concentration of water ice.<ref>Bramson, A, et al. 2015. Widespread excess ice in Arcadia Planitia, Mars. Geophysical Research Letters: 42, 6566-6574</ref> <ref>https://planetarycassie.com/2016/11/04/widespread-thick-water-ice-found-in-utopia-planitia-mars/</ref> <ref>Stuurman, C., et al. 2016. SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars. Geophysical Research Letters: 43, 9484_9491.</ref>

<gallery class="center" widths="380px" heights="360px">

File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle

File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia

</gallery>

==Glacial Features==

Over the years of satellite observations several features have been observed that look like glacial features that is it looks like ice is flowing under a thin cover of debris. Although ice is not stable at many latitudes of Mars, ice could survive for long periods under a few meters of dirt and rock. Many of these supposed regions of underground ice generally begin around 30 degrees of latitude on both sides of the equator. In other words latitudes greater than 30 degrees may have glaciers.<ref> Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>
Some bear an uncanny resemblance to alpine or mountain glaciers of the Earth. These, supposed alpine glaciers, have been called glacier-like forms (GLF) or glacier-like flows (GLF). <ref> Arfstrom, J and W. Hartmann. 2005. Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships. Icarus 174, 321-335.</ref> <ref> Hubbard B., R. Milliken, J. Kargel , A. Limaye, C. Souness . 2011. Geomorphological characterization and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars Icarus 211, 330–346 </ref> Another, more general term sometimes seen in the literature is viscous flow features (VFF). <ref> Hubbard B., R. Milliken, J. Kargel , A. Limaye, C. Souness . 2011. Geomorphological characterization and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars Icarus 211, 330–346 </ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° E (309.5 W)
File: Wikielephantglacier.jpg|Glacier in Greenland Notice how it resembles the glacier on Mars.
File:ESP 047193 1440tongues.jpg|Tongue-shaped glaciers Lat: 35.6° S Long: 109.7° E (250.3 W)

</gallery>

Based on current models of the Martian atmosphere, ice should not be stable if exposed at the surface in the mid-Martian latitudes.<ref>Williams, K. E.; et al. (2008). "Stability of mid-latitude snowpacks on Mars". Icarus. 196 (2): 565–577.</ref> It is thus thought that most glaciers must be covered with a layer of rubble or dust preventing free transfer of water vapor from the subliming ice into the air.<ref>Plaut, J.J.; Safaeinili, A.; Holt, J.W.; Phillips, R.J.; Head, J.W.; Sue, R.; Putzig, A. (2009). "Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophys. Res. Lett. 36: L02203.</ref> <ref>Head, J.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; et al. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–350.</ref> In the recent geological past, the climate of Mars may have been different in order to allow the glaciers to grow stably at these latitudes.<ref> Head, J. W.; et al. 2006. "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671 </ref> This provides good independent evidence that the obliquity (tilt) of Mars has changed significantly in the past.<ref> Laskar, Jacques; et al. 2004. "Long term evolution and chaotic diffusion of the insolation quantities of Mars". Icarus. 170 (2): 343–364.</ref> Evidence for past glaciation also appears on the peaks of several Martian volcanoes in the tropics.<ref> Head, J. W.; et al. 2005. "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–351.</ref> <ref> Shean, David E. 2005. "Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit". Journal of Geophysical Research. 110.</ref> <ref>Head, James W.; Marchant, David R. (2003). "Cold-based mountain glaciers on Mars: western Arsia Mons". Geology. 31 (7): 641–644. </ref>
For a long time there was some doubt about there actually being glaciers on Mars. However, instruments onboard the Mars Reconnaissance Orbiter confirmed the existence of ice below a shallow cover of debris. So far this ice has been found by the SHAllow RADar (SHARAD) in features called lobate debris aprons (LDA) and lineated valley fill (LVF).<ref name="Plaut, J. 2008">Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290. </ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> Ice was found both in the southern hemisphere <ref>Holt, J.; Safaeinili, A.; Plaut, J.; Head, J.; Phillips, R.; Seu, R.; Kempf, S.; Choudhary, P.; Young, D.; Putzig, N.; Biccari, D.; Gim, Y. 2008. "Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars". Science. 322: 1235–1238.</ref> and in the northern hemisphere.<ref> Plaut, J.; Safaeinili, A.; Holt, J.; Phillips, R.; Head, J.; Seu, R.; Putzig, N.; Frigeri, A. (2009). "Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophys. Res. Lett. 36. </ref> Researchers at the Niels Bohr Institute concluded that ice in all of the Martian glaciers is equivalent to what could cover the entire surface of Mars with 1.1 meters of ice. <ref>http://spaceref.com/mars/mars-has-belts-of-glaciers-consisting-of-frozen-water.html</ref> <ref>http://www.sciencedaily.com/releases/2015/04/150408102701.htm</ref> <ref>Karlsson, N.; Schmidt, L.; Hvidberg, C. (2015). "Volume of Martian mid-latitude glaciers from radar observations and ice-flow modelling". Geophysical Research Letters. 42: 2627–2633.</ref>
In addition to alpine glaciers on Mars, there are other terrains where ice seems to be moving under a few meters of cover.

===Lineated Valley Fill===

[[File:ESP 052138 1435lvf.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

[[File:ESP 046061 2190lvf.jpg|thumb|300px|right|Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)]]

[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of Lineated Valley Fill (LVF)]]

Lineated valley fill (LVF) are lines of ridges in valleys.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> These lines of ridges are thought to have developed as other glaciers moved down valleys.

===Lobate Debris Aprons===

[[File:800px-Wideviewlda42n18e.jpg|600pxr|Wide view of Lobate Debris Apron (LDA) around a mesa]]

Wide view of Lobate Debris Apron (LDA) around a mesa

Lobate debris aprons (LDA) is the name given to glaciers that surround many mesas and buttes. <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 046273 2225lda.jpg|Close view of LDA around a mesa Mesa is toward the top of the image. Lat: 42.2° N Long: 18.1°E

File:ESP 057389 2195ldacropped.jpg|LDA around a mound the Ismenius Lacus quadrangle, as seen by HiRISE under HiWish program

</gallery>

===Concentric Crater Fill===

Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> The concentric ridges could have been made by the movement of ice away from the walls.
Based on topography measures of height in these craters and calculations of how deep the craters should be based on their diameters, it is thought that the craters are 80% filled with mostly ice.<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref><ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> In other words, these craters hold hundreds of meters of material that probably consists of ice with just a few tens of meters of surface debris.<ref>Garvin, J. et al. 2002. Global geometric properties of martian impact craters. Lunar Planet. Sci: 33. Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> The ice accumulated in the crater from snowfall in previous climates.<ref>Kreslavsky, M. and J. Head. 2006. Modification of impact craters in the northern plains of Mars: Implications for the Amazonian climate history. Meteorit. Planet. Sci.: 41. 1633-1646</ref> <ref>Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> <ref>http://hirise.lpl.arizona.edu/PSP_002917_2175</ref> Concentric crater fill probably develops over many cycles in which snow is deposited, then moves into the crater. Once ice gets inside the crater, shade and a covering of dust preserve it. In time the snow changes to ice. Concentric lines are created by the many separate periods of snow accumulation. Generally snow accumulates whenever the planet’s tilt reaches 35 degrees.<ref>Fastook, J., J.Head. 2014. Concentric crater fill: Rates of glacial accumulation, infilling and deglaciation in the Amazonian and Noachian of Mars. 45th Lunar and Planetary Science Conference (2014) 1227.pdf</ref>

<gallery class="center" widths="380px" heights="360px">
File:Ccffigurecaptioned.jpg|This series of drawings illustrates why researchers believe many craters are full of ice-rich material. The depth of craters can be predicted based upon the observed diameter. Many craters are almost full, instead of having bowl shape; hence it is believed that they have gained much material since they were formed by impact. Much of the extra material is believed to be ice that fell from the sky as snow or ice-coated dust.
Image: 46622 1365ctxcontextccf.jpg|Wide context view of Concentric Crater Fill
Image: ESP_046622_1365ccf.jpg|Concentric Crater Fill Lat: 43.1° S Long: 219.8°E (140.2 W)
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill
</gallery>

==Pingos==

Because of the many signs of ground ice, scientists have speculated for years that someday pingos may be found on the planet. Pingos form in ice-rich ground and contain a core of pure ice. “Pingo,” is an Inuit word. Pingos on Mars would be great because they may contain pure water ice. Over the years many mounds have been examined that resemble pingos. However, we may not be sure if they are real pingos until they are examined by rovers. One picture below from HiRISE may be a pingo. The other picture shows how a pingo looks on the Earth.
The radial and concentric cracks visible here are common when forces penetrate a brittle layer. These particular fractures were probably created by something emerging from below the brittle Martian surface. Ice may have accumulated under the surface in a lens shape; thus making these cracked mounds. Ice being less dense than rock, pushed upwards on the surface and generated these spider web-like patterns. A similar process creates similar sized mounds in arctic tundra on Earth. <ref>http://www.uahirise.org/ESP_046359_1250</ref>

Many features that look like the pingos on the Earth are found in Utopia Planitia (~35-50° N; ~80-115° E).<ref>Soare, E., et al. 2019.
Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)

Melting pingo wedge ice.jpg|Example of a pingo on Earth. On Earth the ice that caused the pingo would melt and fill the fractures with water; on Mars the ice would turn into a gas in the thin Martian atmosphere.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

</gallery>

==Ring-Mold Craters==

Ring-mold craters are a kind of impact crater that looks like the ring molds used in baking.<ref>https://link.springer.com/referenceworkentry/10.1007/978-1-4614-9213-9_318-1</ref> <ref>kress, A., J. Head. 2008. Ring‐mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophysical Research Letters Volume 35, Issue 23</ref> They are believed to be caused by an impact into ice.<ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL035501</ref> Ice that is covered by a layer of debris. They are found in parts of Mars that have buried ice. Laboratory experiments confirm that impacts into ice result in a "ring mold shape." They are also bigger than other craters in which an asteroid impacted solid rock. Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill.<ref>Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8</ref> <ref>Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209</ref> <ref>Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379</ref> They may be an easy way for future colonists of Mars to find water ice because some may contain ice that is relatively pure. Also, since the ring-mold was created during a rebound, ice may have been brought up from below the surface so much less digging or drilling may be required to gather ice.

Note: this is one of the first explanations for ring-mold craters, another has been proposed.

<gallery class="center" widths="380px" heights="360px">
File:Ringmolddiagramlabeled.jpg|Ring-mold craters form when an impacting object goes through a rock layer to reach ice. The rebound forms the ring-mold shape, and then dust and debris settle on the top which serves to insulate the ice.
26055cratermesaswide.jpg|Wide view of a field of ring mold craters, as seen by HiRISE under HiWish program Lat: 34.9° S Long: 105.4° E
26055ringmoldcrater.jpg|Close view of ring mold crater. Note: this is an enlargement of the previous image of a field of ring mold craters.

File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
</gallery>

==Pedestal Craters==

[[File:Pedestaldrawingcolor2.jpg|thumb|400px|right|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

A pedestal crater is an impact crater which has its ejecta sitting above the surrounding terrain. This forms a raised platform (like a pedestal). These craters are produced when an impact crater ejects material that forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions.<ref>http://hirise.lpl.eduPSP_008508_1870</ref> <ref>Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref>http://themis.asu.edu/feature_utopiacraters</ref> <ref> McCauley, John F. (December 1972). "Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars". Journal of Geophysical Research. 78 (20): 4123–4137(JGRHomepage). </ref> Much of the material under the pedestal crater may be ice. These may be useful for sources of water ice as these craters can be easily spotted from orbit.

<gallery class="center" widths="380px" heights="360px">

Image: ESP 047615 1275pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program Top layer has protected the lower material from being eroded. Location is Hellas quadrangle, at 52.014° S and 110.651° E (249.349 W).

</gallery>

==Latitude Dependent Mantle==

With the increasing resolution of cameras orbiting Mars, we have discovered that many parts of the planet are covered by a smooth coating that in some cases is layered and quite thick. <ref>Mustard, J., C. Cooper, M. Rifkin. 2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature 412, 411–414 .</ref> Some parts are eroded, revealing rough surfaces. Some parts possess layers. It’s generally accepted that mantle is ice-rich dust that fell from the sky as snow and ice-coated dust grains during a different climate.<ref> Pollack, J., D. Colburn, F. Flaser, R. Kahn, C. Carson, and D. Pidek. 1979. Properties and effects of dust suspended in the martian atmosphere. J. Geophys. Res. 84, 2929-2945. </ref> Latitude Dependent Mantle and many other supposed ice-rich features occur in two latitude bands in the mid-latitudes; 30-60 degrees North and 30-60 degrees South latitudes.
We do not know the exact concentration of ice in the mantle. There may be a little or a lot; maybe the amount varies from place to place. Many places that we believe contain water may require hard drilling to harvest the ice. Perhaps the latitude dependent mantle will not be so hard to extract water from. We know that the mantle does not seem to break up into boulders. Boulders would suggest hard basalt to drill through.

<gallery class="center" widths="380px" heights="360px">
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
Esp 037167 1445mantle.jpg|Surface showing appearance with and without mantle covering Location is [[Terra Sirenum]] in Phaethontis quadrangle.
</gallery>

==Upper Plains Unit==

In many places, it seems that the latitude dependent mantle has accumulated to a substantial thickness. Researchers have called it the “Upper Plains Unit.” This unit can be easily spotted by orbiting satellites by a number of its shapes. Sometimes it displays sets of dipping layers in impact craters, in depressions, and along mesas. It may be 50-100 meters thick, so it may be a source of large amounts of water.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref>

[[File: ESP 019778 1385pyramid.jpg|thumb|400px|center|Layered structure in crater that is probably what is left of a layered unit that once covered a much larger area. Material for this unit fell from the sky as ice-coated dust. Location is Hellas quadrangle, Lat: 41.3° S Long: 116°E (244 W)]]

This unit also degrades into brain terrain. Brain terrain is a region of maze-like ridges 3–5 meters high. Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>

[[File: 48011 1370upperunit.jpg|thumb|400px|left|Close view of upper plains unit breaking down into brain terrain As ice leaves the ground, the ground collapses and winds blow the remaining dust away. Location is Hellas quadrangle.]]

[[File:53630 2195brainslvf.jpg|thumb|400px|center|Close view of brain terrain]]

In some places the upper plains unit exists as large fractures and troughs with raised rims; these are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Cracks expose more surface area, and consequently more ice in the material sublimates into the planet’s thin atmosphere. Eventually, small cracks become large canyons or troughs.

[[File: ESP 042198 2235pyramid.jpg|thumb|400px|left|View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain. Lat: 43.2° N Long: 25.9° E (334.1 W)]]

[[File:ESP 028339 2245headarticle.jpg|thumb|400px|center|Ribbed terrain Lat: 44° N Long: 26.2°E (333.8 W)]]

There is one common surface feature that is common to most of these features that contain ice. It is called “brain terrain”. It consists of complex ridges that makes it resemble the outside of the human brain. Wide ridges are called ''closed-cell'' brain terrain, and the less common narrow ridges are called ''open-cell'' brain terrain.<ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref> It is thought that the wide closed-cell terrain contains a core of ice, and when the ice disappears the center of the wide ridge collapses to produce the narrow ridges of the open-cell brain terrain.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> Shadow measurements from HiRISE indicate the ridges are 4-5 meters high. Brain terrain has been observed to form from what has been called an "Upper Plains Unit."

[[File:45917 2220brainsopenclosed.jpg|thumb|400px|left|Open and closed brain terrain with labels Lat: 41.9°N Long: 16.7° E (343.3 W) Closed-cell brain terrain may still contain an ice core.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> ]]

[[File:54527 2225brainsface.jpg|thumb|400px|center|Brain Terrain to the right. Box shows the size of a football field.]]

In summary, brain terrain is found on the surface of glaciers, concentric crater fill, lineated valley fill, lobate debris aprons, and the upper plains unit. The closed cell brain terrain probably contains a core of ice. We do not know the size of this core, but having a surface covered by brain terrain is a clue that much more ice may lie below.

==Future research and technology==

Although we have strong evidence that Mars had much water in its past and that certain landscapes are signs of water, there is much more to learn before we can start to utilize these resources. Ideally, we would not want to travel too far for our water. The ice found in triangular depressions may be too far. On the other hand water from the mantle and various glacial forms may be much closer, but it may require digging through meters of debris or the materials (in the mantle for example) may only contain a small percentage of water. Consequently, we should develop rovers and penetrators which could sample various features that contain water. This program of looking for ice-rich places should be intensified once we decide where we want to land. Already, individuals are targeting HiRISE observations at possible manned mission’s sites.<ref>https://www.uahirise.org/ESP_053423_2055</ref>
Later, we will want to develop robotic machines to mine, process, and deliver ice to the Mars colonists. At least one individual has designed a device that drills for and extracts water from ice-rich ground (check out second external link from the 20th Mars Society Convention). In 2017, there was a nation-wide contest for college students to build such a device.<ref>http://triblive.com/news/education/career/13040517-74/cmu-team-finalist-for-nasas-mars-ice-challenge-to-drill-for-water</ref> <ref>https://www.nasa.gov/press-release/nasa-s-mars-ice-challenge-follow-the-water</ref>

==Appendix==

As more and more observations from increasing powerful instruments was gathered, researchers developed ideas to explain the origin of ice rich features on a planet that is very cold and dry. It seems that ice moves from the poles to the mid-latitudes frequently, as the planets tilt changes.
Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as our moon stabilizes Earth; at times the tilt of Mars has even been greater than 80 degrees<ref> name= Touma J. and J. Wisdom. 1993. The Chaotic Obliquity of Mars. Science 259, 1294-1297.</ref> <ref> Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364. </ref>
When the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles. <ref> Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. doi:10.1029/2007GL032813. </ref> Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Models show that this material will concentrate in the mid-latitudes. <ref> Levy, J., J. Head, D. Marchant. 2009a. Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations. J. Geophys. Res. 114. doi:10.1029/2008JE003273.</ref> <ref> Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111-131 </ref> General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found. <ref> Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364. </ref>
When the tilt begins to return back to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust. <ref> Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799. </ref> <ref> Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799. </ref> <ref> Schorghofer, N., 2007. Dynamics of ice ages on Mars. Nature 449, 192–194.</ref> The lag deposit covers the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind. <ref> Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096. </ref>

==References==
{{reflist|colwidth=30em}}

== External links ==

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
* https://www.youtube.com/watch?v=kpnTh3qlObk T. Gordon Wasilewski - Water on Mars - 20th Annual International Mars Society Convention] Describes how to get water from ice in the ground

* https://www.youtube.com/watch?v=PYl3HXpvqhM Kris Zacny Water on Mars - 21st Annual International Mars Society Convention Describes how to get water from ice in the ground]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=m2ERsEXAq_s - Jeffrey Plaut - Subsurface Ice - 21st Annual International Mars Society Convention-2018]

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

==See Also==

*[[Glaciers on Mars]]

*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Sublimation]]

*[[Sublimation landscapes on Mars]]

*[[Water]]

[[Category: Hydrology]]

HiWish program

2023-03-04T22:51:52Z

Suitupandshowup: /* Pingos */

HiWish is a NASA program in which anyone can suggest a place for the [[High Resolution Imaging Science Experiment (HiRISE)]] camera on the [[Mars Reconnaissance Orbiter]] to image.<ref>http://www.marsdaily.com/reports/Public_Invited_To_Pick_Pixels_On_Mars_999.html |title=Public Invited To Pick Pixels On Mars |date=January 22, 2010 |publisher=Mars Daily</ref> <ref>http://www.astronomy.com/magazine/2018/08/take-control-of-a-mars-orbiter</ref> <ref>http://www.planetary.org/blogs/guest-blogs/hiwishing-for-3d-mars-images-1.html</ref> It started in January 2010. Three thousand people signed up in the first few months of the program.<ref>Interview with Alfred McEwen on Planetary Radio, 3/15/2010</ref> <ref>http://www.planetary.org/multimedia/planetary-radio/show/2010/384.html|title=Your Personal Photoshoot on Mars?|website=www.planetary.org|</ref> By February 2020, 9,726 had signed up and 24,059 suggestions had been submitted for targets in each of the 30 quadrangles of Mars. A that point 10,318 images had been taken.<ref> https://www.jpl.nasa.gov/missions/viking-1/</ref> <ref> OP Lunch Talk #10: HiWish, public suggestion targeting web tool for Mars imaging with MRO/HIRISE</ref> The first images were released in April 2010.<ref>http://topnews.net.nz/content/23052-nasa-releases-first-eight-hiwish-selections-people-s-choice-mars-images |title=NASA releases first eight "HiWish" selections of people's choice Mars images |date=April 2, 2010 |publisher=TopNews |accessdate=January 10, 2011 |archive-url=https://www.webcitation.org/6Gop7RR0c?url=http://topnews.net.nz/content/23052-nasa-releases-first-eight-hiwish-selections-people-s-choice-mars-images |</ref> Some of the images from HiWish were used for three talks at the 16th Annual International Mars Society Convention. Below are some of the over 4,224 images that have been released from the HiWish program as of March 2016.<ref>McEwen, A. et al. 2016. THE FIRST DECADE OF HIRISE AT MARS. 47th Lunar and Planetary Science Conference (2016) 1372.pdf</ref>

==Landslides==

[[File:ESP 057191 2150landslidecropped.jpg|Landslide]]

Landslides have been observed on Mars. They may be a little different since the gravity of Mars is only about one third as that of the Earth.
<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 1585landslide.jpg|Landslide
File:ESP 043963 1550landslide.jpg|Landslide
</gallery>

==Hollows==

[[File:28207 2250hollowsarrows.jpg|Hollows]]

Hollows make strange, beautiful landscapes. The hollows are believed to be produced when ice leaves the ground and the remaining dust is blown away. There is much water frozen in the ground. Water is carried around the planet frozen on dust grains that fall to the ground and make up what is called “mantle.” Mantle is produced when the climate is such that there is a lot of dust and moisture in the atmosphere. During those times, water will freeze onto the dust particles. Eventually, the particles will be too heavy and fall to the surface. In addition, it may snow on Mars.
The mantle covers wide expanses. It has a smooth appearance. It covers the irregular, created surface of the planet.

<gallery class="center" widths="380px" heights="360px">

File:46325 2225hollows4.jpg|Hollows

File:ESP 046325 2225hollowsmiddlelabeled.jpg|Hollows

</gallery>

==Mud Volcanoes==

[[File:53381 2265mud.jpg|Mud volcanoes]]

Mud volcanoes They may have come through a zone of weakness in the rock here

Mud volcanoes are very common in a place on Mars called the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Mud that formed the volcanoes comes from a depth underground that is deep enough to be protected from radiation. The radiation level at the surface would kill most organisms over time. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

<gallery class="center" widths="380px" heights="360px">
File:570770 2100coneslabeled.jpg|Mud volcanoes

File:52050 2200mudvolcanoes.jpg|Mud volcanoes
File:ESP 043580 2120mud.jpg|Wide view of field of mud volcanoes
</gallery>

==Volcanic vents==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

[[File:ESP 030440 1945ventcropped.jpg|Volcanic vent]]

Volcanic vent

==Lava Flows==

[[File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons]]

Lava flow on Olympus Mons

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Large volcanoes in the [[Tharsis]] region show many overlapping lava flows. Lava flows can also move around and create what appear to be layers, especially if it behaves like water. Basalt flows are very fluid.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="380px" heights="360px">
File:44828 2030lavaflow.jpg|Lava flows These are common in large sections of Mars.

File:ESP 044840 1620lavaflow.jpg|Lava flow

File:WikiESP 035095 1975lavalobestharsiswide.jpg|Old and young lava flows

File:68460 1945laveolympus.jpg|Lava flowing down a slope from [[Olympus Mons]]

File:68460 1945lavechannel.jpg|Lava channel from Olympus Mons

</gallery>

==Rootless Cones==

[[File:40162 2065conesarrows2.jpg|Rootless cones ]]

Rootless cones

Rootless Cones are thought to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam. The resulting steam explosion produces a ring or cone. Such features are common in certain locations on the Earth. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form. Sometimes a wake is made as the lava moves along the surface.

<gallery class="center" widths="380px" heights="360px">

File:45384 2065cones2.jpg|Rootless cones
File:45384 2065cones.jpg|Rootless cones Here, lava has moved over ice-rich ground from the upper right to the lower left of the picture.
File:58610 2100coneswakeslabeled.jpg|Close view of wake of a rootless cone
File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones

</gallery>

==Dikes==

[[File:ESP 045981 2100dike2.jpg|Dike]]

Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

Dikes show as mostly straight ridges. They are made when magma flows along cracks or faults in the ground. This part of the process happens under the ground. Later erosion will remove the weaker materials around the dike. What is left is a narrow wall of rock.<ref> "Characteristics and Origin of Giant Radiating Dyke Swarms". MantlePlumes.org.</ref> On Mars many faults are due to stretching of the crust. The mass of huge volcanoes pull at the crust until it cracks.

[[File:ESP 046403 2095dikecropped.jpg|thumb|400px|center|Dike in [[Syrtis Major quadrangle]]]]

==Troughs==

[[File:ESP 051781 2035troughs.jpg |Troughs]]

Troughs are common on Mars. They are due to the great weight of several huge volcanoes on Mars. The mass of these structures has caused the crust to stretch. That tension made the crust break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="380px" heights="360px">

File:56910 2100trough.jpg|Group of troughs

File:Troughs in Elysium Planitia.jpg|Troughs showing layers Hard cap rock is at the surface. The center section is in color. With HiRISE only a strip in the middle is in color.

File:ESP 057834 2005troughmesa.jpg|Troughs cutting through mesa, as seen by HiRISE under HiWish program
</gallery>

==Faults==

Faults are visible in some parts of Mars. They are most noticeable in places where many layers exist. Sometimes their presence is known because they can change the direction of stream channels.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater

[[File:60331 1880faultslabeled2.jpg|thumb|300px|left|Faults in layered terrain]]

[[File:27615 1880faults.jpg|thumb|300px|center|Faults in layered terrain]]

[[File:71634 1880layersfaultslabeled.jpg|thumb|300px|Faults in layers in Danielson Crater]]

<gallery class="center" widths="380px" heights="360px">
File:26086 1800fault.jpg|Fault that changed direction of stream. CTX image is included for context.

</gallery>

==Mesas and layers==

[[File:58788 1890layerscolorlabeled2.jpg|Mesa with layers]]

Mesa with layers

On Mars much layered terrain is visible. Layered rock is formed from separate events. For example, a layer may be formed at the bottom of a lake. Later, lava may cover that layer, thus making a new layer—one that is harder. In times erosion may remove nearly all the layers. But, sometimes remnants are left behind, especially if they are topped off by a hard cap rock. Lave flows can make cap rock. The cap rock will protect the underlying rocks from erosion. Cap rock often breaks up into large boulders. Sometimes the boulders are in the shape of cube-shaped blocks. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="380px" heights="360px">
File:58563 2225mesa.jpg|Mesa

File:58524 1820layerscolor4labeled.jpg|Mesa with layers

File:58919 1935mesalayers.jpg|Mesa with layers Box is the size of a football field.

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte The box shows the size of a football field.

</gallery>

==Layers in Craters==

[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

Craters can contain mesas that show layers. It is believed that these layers are the remnants of material that once covered a wide area, but is now only in protected places like inside craters. The layers mean that different events laid down the layers. These layers are probably due to latitude dependent mantle that falls from the sky at different times. Mantle is mostly from ice-coated dust falling from the sky under certain climate conditions. Wind, acting over millions of years, will shape the material in craters into smooth mesas.

<gallery class="center" widths="380px" heights="360px">

File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>

File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.

File:28207 2250cratermesa.jpg|Color view of layers in a mesa in a crater
</gallery>

==Dipping Layers==

[[File:46180 2225dippinglayers.jpg|Dipping layers and brain terrain (right side of picture)]]

Dipping layers and brain terrain (right side of picture)

A common feature on Mars is “dipping layers.” They are groups or stacks of layers that seem to be leaning against something steep like a crater wall or the wall of a mesa. It is believed that they represent material that once covered a wide area, but is now only in protected places. The layers mean that different events laid down the layers. These layers are probably due to latitude dependent mantle that falls from the sky at different times. Mantle is mostly from ice-coated dust falling from the sky under certain climate conditions. These dipping layers are often smooth from the action of the wind over millions of years.

[[File:ESP 038002 1375dipping.jpg|thumb|300px|left|Wide view of dipping layers against slopes]]

[[File:ESP 062082 2175dippingcropped.jpg|thumb|300px|right|Dipping layers These may be the remains of past layers of mantle that covered the whole area.]]

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210pyramidsismenius.jpg|Dipping layers against a mesa wall.

</gallery>

[[File:ESP 019778 1385pyramid.jpg|Set of dipping layers in crater]]

Set of dipping layers in crater

==Boulders==

[[File:28497 2250boulderslabeled.jpg|Boulders near hollows]]

Boulders near hollows

Large, house-sized boulders are widespread on the Red Planet. Mars has an old surface—billions of years old. In that time, erosion has broken down many hard rocks. Most of Mars is covered with hard volcanic rock. The dark volcanic rock basalt covers most of the Martian surface. When it breaks, it first forms large boulders.

<gallery class="center" widths="380px" heights="360px">

File:55119 2080mesasinglelabeled.jpg|Mesa The top has a hard cap rock that protects the underlying rocks from erosion. Boulders are visible in the image.
File:58904 2240brainsboulders.jpg|Boulders and brain terrain
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas Box shows size of football field.
49950 2125ridgesboulders.jpg|Close view of ridge networks, as seen by HiRISE under HiWish program Many boulders are visible.

File:ESP 045415 2220boulders.jpg|Color view of boulders

45575 2535dunebouldertracks.jpg|Boulders and tracks, as seen by HiRISE under HiWish program The arrows show a boulders that have produced a track by rolling down dune.

</gallery>

[[File: 47157 1850boulders.jpg|Boulders and their tracks from rolling down a slope Arrows show two boulders at the end of their tracks.]]

Boulders and their tracks from rolling down a slope Arrows show two boulders at the end of their tracks.

[[File:59458 2145boulders.jpg|Color view of boulders]]

Boulders formed from break up of a mesa

==Yardangs==

[[File:61167 1735yardangs.jpg|Yardangs]]

Yardangs

Yardangs develop from fine-grained material. They are shaped by the wind and show the direction of the dominant winds.<ref> Bridges, Nathan T.; Muhs, Daniel R. (2012). "Duststones on Mars: Source, Transport, Deposition, and Erosion". Sedimentary Geology of Mars. pp. 169–182. doi:10.2110/pec.12.102.0169. ISBN 978-1-56576-312-8.</ref> <ref> https://www.uahirise.org/ESP_039563_1730</ref> Volcanoes supply much of this fine-grained material. Yardangs are especially widespread in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because yardangs exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref> The largest single source of dust in the air on Mars comes from the Medusae Fossae Formation.<ref> Ojha, Lujendra; Lewis, Kevin; Karunatillake, Suniti; Schmidt, Mariek (2018). "The Medusae Fossae Formation as the single largest source of dust on Mars". Nature Communications. 9 (1): 2867.</ref>

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 047915 1815yardangs.jpg|Wide view of yardangs
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs
</gallery>

==Ring-Mold Craters==

[[File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.]]

Ring mold craters They may contain ice.

Ring-mold craters are a type of small impact crater that looks like the ring molds used in baking.<ref>https://link.springer.com/referenceworkentry/10.1007/978-1-4614-9213-9_318-1</ref> <ref>kress, A., J. Head. 2008. Ring‐mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophysical Research Letters Volume 35, Issue 23</ref> One popular idea for their formation is an impact into ice--Ice that is covered by a layer of debris.<ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL035501</ref> They are found in parts of Mars that contain buried ice. Laboratory experiments confirm that impacts into ice end in a "ring mold shape." Other evidence for this contention is that they are bigger than other craters in which an asteroid impacted solid rock implying that the material entered by the impact was softer than rock (as ice is). Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill—both thought to have buried ice under a thin layer of rocky debris<ref>Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8</ref> <ref>Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209</ref> <ref>Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379</ref> Ring-mold craters may be an easy way for future colonists of Mars to find water ice because some may contain ice that is relatively pure. And, since it was generated during a rebound, ice may have been brought up from below the surface; hence, less digging or drilling may be required to gather ice.

<gallery class="center" widths="380px" heights="360px">

26055ringmoldcrater.jpg|Close view of ring mold crater.
File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
</gallery>

==Dark Slope Streaks==

[[File:55480 2060streaksobstacles.jpg|Some of the streaks here were affected by boulders.]]

Streaks around a mound. Some of the streaks here were affected by boulders.

[[File:55107 1930streaksboulders2.jpg|thumb|300px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

[[Dark slope streaks]] are avalanche-like features common on dust-covered slopes.<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. 2010. Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> Although they appear much darker than their surroundings, the darkest streaks are only about 10% darker than their backgrounds. Streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046188 1855streakslabeled2.jpg|Streaks along a mesa
File:ESP 045435 2055troughlayers.jpg|Dark slope streaks in a trough

</gallery>

[[File:23677streakslabeled.jpg|Streaks often start at a small point and then expand down slope.]]

Streaks often start at a small point and then expand down slope. Many streaks may be caused by the action of solid carbon dioxide (dry ice). Under conditions on Mars, during the night dry ice forms under the surface. When the ground warms in the morning, the dry ice turns into a gas and creates a wind that disturbs the dust grains. If situated on a steep slope, an avalanche of bright dust moves down and uncovers the dark undersurface.<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al. 2022. Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks. JGR Planets. Volume127, Issue4. e2021JE006988</ref>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface. As a result, dark underlying material is exposed.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit.<ref>https://www.uahirise.org/ESP_042201_1715</ref> They helped scientists by blowing dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> Dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">

File:ESP 036297 2370devils.jpg|Dust Devil Tracks

File:ESP 036631 2335devilsbottom.jpg|Dust devil tracks in Casius quadrangle

</gallery>

[[File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.|500pxr|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.]]

Dust devil tracks in Casius quadrangle

==Dunes==

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Some places on Mars have many beautiful dark dunes. Rovers on the Martian surface confirmed earlier ideas that the dunes are composed of sand made from the volcanic rock basalt..<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> Dunes are often covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring. As the frost disappears, different patterns can emerge on the dunes. Dunes can take on different colors because of slight chemical variations in the sand grains.

The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars. However, we must remember that its atmosphere is only about 1 % as dense as the Earth's. Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).<ref> https://www.space.com/30663-the-martian-dust-storms-a-breeze.html</ref>

[[File:ESP 046378 1415dunescolor.jpg|thumb|300px|right|Dunes]]

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:59628 1275dunes.jpg|Dunes in Hellas quadrangle

</gallery>

[[File:58089 2170duneswidemarsp.jpg |600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle|Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle]]

Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle

[[File:59658 1415dunes.jpg|600pxr|Dunes The location is the Noachis quadrangle |Dunes The location is the Noachis quadrangle]]

Dunes The location is the Noachis quadrangle

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Glaciers==

[[File:ESP 018857 2225alpineglacier.jpg|Glacier moving out of a valley This is similar to glaciers on the Earth]]

Glacier moving out of a valley This is similar to glaciers on the Earth

Glaciers have been described as “rivers of ice.” With glaciers there is a downward movement that can be noticed by examining patterns on their surface. There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. Exposed ice will not last long under present climate conditions on Mars, but just a few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref> Researchers noticed decades ago that many forms on Mars resembled glaciers on the Earth. As scientists received pictures with greater resolution, the shapes and patterns visible on their surfaces looked like the flows visible in the Earth’s glaciers.

<gallery class="center" widths="380px" heights="360px">

File:ESP 050176 2245glacier.jpg|Glacier moving out of a valley
File:ESP 045085 2205flowlabeled.jpg|Alpine Glacier moving out of a valley and then moving onto Lineated valley fill (LVF) The LVF contains ice under a layer of insulating debris. Lineated Valley Fill is considered to be a glacier.
File:47193 1440glacier.jpg|Glaciers
File:35934 2215brainsglacier.jpg|End of an old glacier. Most of the ice is gone, but the material moved by the glacier is formed into an arc.
</gallery>

<gallery class="center" widths="380px" heights="360px">
ESP 045505 1400flow.jpg|Flow feature that was probably a glacier

Image:ESP_020319flowcontext.jpg|Context for the next image of the end of a glacier.

Image:ESP_020319flowsclose-up.jpg|Close-up of the area in the box in the previous image. This may be called by some the terminal moraine of a glacier. For scale, the box shows the approximate size of a football field.

Image:Tongue23141.jpg|Tongue-shaped glacier, Ice may exist in the glacier, even today, beneath an insulating layer of dirt.

Image:Tongue23141close.jpg|Close-up of tongue-shaped glacier Resolution is about 1 meter, so one can see objects a few meters across in this image.

</gallery>

==Lobate Debris Aprons (LDA’s) ==

Lobate debris aprons (LDAs), first seen by the Viking Orbiters, look like piles of rock debris below cliffs.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. </ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> They slope away from mesas and buttes.
The Mars Reconnaissance Orbiter's Shallow Radar found pure ice in LDA’s around many mesas.<ref>http://www.planetary.brown.edu/pdfs/3733.pdf</ref> Based on this data, LDA’s are considered to be glaciers covered with a thin layer of rocks.<ref>Head, J. et al. 2005. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars. Nature: 434. 346-350</ref><ref>http://www.marstoday.com/news/viewpr.html?pid=18050</ref> <ref>http://news.brown.edu/pressreleases/2008/04/martian-glaciers</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>Holt, J. et al. 2008. Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2441.pdf</ref> <ref>Petersen, E., et al. 2018. ALL OUR APRONS ARE ICY: NO EVIDENCE FOR DEBRIS-RICH “LOBATE DEBRIS APRONS” IN DEUTERONILUS MENSAE 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2354.</ref>

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 036580 2260ldacropped.jpg|Lobate debris apron
File:ESP 036619 2275ldacropped.jpg|Lobate debris apron
</gallery>

==Lineated Valley Fill (LVF) ==

Lineated valley floor consists of many mostly parallel ridges and grooves on the floors of many channels. The ridges and grooves look like they moved around obstacles. They are believed to be ice-rich. Some glaciers on the Earth show such features.<ref> https://www.uahirise.org/ESP_026414_2205</ref>
[[File:ESP 052138 1435lvf.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

[[File:ESP 046061 2190lvf.jpg|thumb|300px|right|Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)]]
[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of Lineated Valley Fill (LVF)]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 055408 1375lvf2.jpg|Lineated Valley Fill
File:ESP 046840 2130lvf.jpg|Lineated Valley Fill in valley
File:53630 2195lvf.jpg|Lineated Valley Fill
File:56544 2200lvfbrains.jpg|Lineated Valley Fill
File:56544 2200lvflabeled.jpg|Lineated Valley Fill
</gallery>

==Concentric Crater Fill (CCF) ==

[[Image: ESP_046622_1365ccf.jpg |Concentric Crater Fill Lat: 43.1° S Long: 219.8°E (140.2 W]]

Concentric Crater Fill Located at Lat: 43.1° S Long: 219.8°E (140.2 W

Concentric crater fill is believed to be an ice-rich feature on the floors of many Martian craters. The floor of craters exhibiting CCF is almost totally covered with many parallel ridges.<ref>https://web.archive.org/web/20161001224229/http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185 </ref> It is common in the mid-latitudes of Mars,<ref>Dickson, J. et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> and is widely accepted as caused by glacial movement.<ref>Head, J. et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for late Amazonian obliquity-driven climate change. Earth Planet. Sci Lett: 241. 663-671.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res.: 112.</ref> The [[Ismenius Lacus quadrangle]] contains examples of concentric crater fill.

<gallery class="center" widths="380px" heights="360px">
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill

File:46688 1365ccf2.jpg|Close view of Concentric Crater Fill (CCF)
</gallery>

==Brain Terrain==

[[File:45917 2220brainsopenclosed.jpg|Open and closed brain terrain]]

Open and closed brain terrain The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>

Brain terrain is an area of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists. There are two kinds—open and closed. Brain terrain is thought to begin with cracks that get larger and larger as ice leaves the ground. When ice is exposed on Mars under its present climate conditions, ice goes directly into the air. That process of going from a solid to a gas—instead of first to a liquid—is called sublimation. With this process, the cracks get wider and wider until a complex of high and low areas remains. <ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:25246brainseroding.jpg|Brain terrain
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle The closed cell brain terrain may still hold an ice core,<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> so it may a source of water for future colonists.
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle

File:53630 2195brainslvf.jpg|Brains on surface of leaneted valley fill
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ice Cap Layers==

[[File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019. ]]

Layers in northern ice cap This photo was named picture of the day for January 21, 2019.

The northern ice cap of layers displays many layers. These layers are visible when a valley cuts through the cap. Layers in the ice cap, as with other exposures of layers across the planet, are formed from frequent dramatic changes in the climate. These changes are the result of great changes in the rotational axis or tilt of the planet. Mars does not have a large moon to stabilize its' tilt; hence the planet has huge variations in its tilt (maybe from its present Earth-like tilt to over twice the Earth’s).

<gallery class="center" widths="380px" heights="360px">

File:ESP 061636 2620nicecaplayerscroppedlabeled.jpg|Northern ice cap layers
File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

</gallery>

==Spiders==

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

Some features have been called spiders because they can resemble spiders. The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> <ref>https://www.uahirise.org/</ref> This process results in the appearance of dark plumes that are often blown in one direction by local winds. Besides producing plumes, dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>
The process of making spiders was demonstrated in laboratory simulations involving slabs of dry ice and glass spheres of different sizes.<ref>https://www.nature.com/articles/s41598-021-82763-7.pdf</ref> <ref>McKeown, L., et al. 2021. The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric
pressure. Scientific Reports.</ref> <ref>https://www.livescience.com/spiders-on-mars-explained-dry-ice.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref>

<gallery class="center" widths="380px" heights="360px">

File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program

</gallery>

==Mantle==

[[File:37167 1445mantlelabeled.jpg|Mantle Mantle covers the surface irregularities on Mars]]

Mantle Mantle covers the surface irregularities on Mars

Mantle on Mars appears as a smooth surface. It covers the normal irregular surface of the planet. It is often called “Latitude Dependent Mantle” because it occurs at certain distances from the equator (certain latitudes).<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> This latitude dependent mantle is believed to fall from the sky. During certain climatic conditions, moisture from the air will freeze onto dust particles. When they become too heavy, these particles fall to the ground. Snow may also fall on to the mantle. So, mantle consists of ice with dust. Since Mantle has a widespread distribution, it may be a major source of water for future colonists. Sometimes mantle displays layers because it was deposited at different times. The climate of Mars has changed many times due to a lack of a large moon. Our Earth’s moon is very massive and that helps to control the tilt of the rotational axis of our Earth. In other words, our moon keeps our planet’s tilt from changing much. Changes in the tilt of a planet will cause major changes in climate.

<gallery class="center" widths="380px" heights="360px">

File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program

</gallery>

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.

==Polygons==

[[File:56942 1075icepolygonslabeled2.jpg|Polygons]]

Polygons

Many surfaces on Mars have polygon shapes. These areas are sometimes called “polygonal patterned ground.” The polygons can be of different shapes and sizes—often very beautiful. They are believed to be caused by ice in the ground because they occur on the Earth where there is ice in the ground.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction.<ref>https://www.uahirise.org/ESP_066782_1110</ref> <ref>https://www.uahirise.org/ESP_047247_1150</ref>

In the future they may help point us to supplies of ice for colonists. The locations of polygons will provide evidence for us to make detailed maps for locations of water before we send crews to live there.

<gallery class="center" widths="380px" heights="360px">

File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons that shows polygons of varying sizes. Dark lines are defects in processing.
File:56148 1145polygons.jpg|Close view of polygons

File:ESP 043821 2555dryice.jpg|Field of dunes defrosting Black areas are free of frost, so the dark of the dunes shows up. White portions of dunes are still covered with frost.

File:ESP 043821 2555dryicecolor.jpg|Close view of parts of two dunes showing white parts with frost. The polygon surface they sit on still has frost in the low areas.

</gallery>

[[File:43821 2555dunesdefrosting2.jpg|Defrosting dune--white areas still contain frost]]

Defrosting dune--white areas still contain frost. Frost is in low parts of polygons.

==Scalloped Terrain==

[[File:37461 2255scallopslabeled2.jpg|Scalloped terrain This feature is important it may point future colonists to water supplies.]]

Scalloped terrain This feature is important it may point future colonists to water supplies.

Scalloped topography or terrain is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region called “Utopia Planitia.”<ref>last1 = Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 |</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> This terrain displays shallow, rimless depressions with scalloped edges--commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>http://www.uahirise.org/ESP_038821_1235</ref> <ref>Dundas, C., et al. 2015. Modeling the development of martian sublimation thermokarst landforms. Icarus: 262, 154-169.</ref> Scalloped topography may be of great importance for future colonization of Mars because radar studies reveal it is ice-rich.<ref>"Dundas, C. 2015" Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Stuurman, C., et al. 2016. SHARAD reflectors in Utopia Planitia, SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars. Geophysical Research Letters, Volume 43, Issue 18, 28 September 2016, Pages 9484–9491.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia
File:37461 2255scallopedclose.jpg|Scalloped terrain
</gallery>

==Pingos==

[[File: ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)]]

Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)

For many years, Pingos were believed to be present on Mars. Since they contain pure water ice, they would be a great source of water for future colonists on Mars. One picture from HiRISE under the HiWish program was thought to be a pingo.

<gallery class="center" widths="380px" heights="360px">

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

</gallery>

==Gullies==

[[File:50858 1435gullylabeled.jpg|Gullies with parts labeled--Alcove, Channel, Apron]]

Gullies with parts labeled--Alcove, Channel, Apron

[[Martian gullies]] are narrow channels and their associated downslope deposits. They are found on steep slopes. Most are seen on the walls of craters. Many are visible near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref >Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. For many years, gullies were thought to be caused by recent running water. But since some are being formed today, even when the climate of Mars is too cold for running water to exist on the surface, there must be another cause. After more observations, it was shown that pieces of dry ice moving down slopes could cause them. Nevertheless, some scientists think that in the past, water may have been involved in their formation.

<gallery class="center" widths="380px" heights="360px">
File:ESP 046386 1420gullies.jpg|Gullies

File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program Only part of the picture appears in color because the camera only produces color in a center strip.

</gallery>

[[File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>]]

Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>

==Craters==

[[File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.]]

This is a fairly young crater as it still shows ejecta, layers, and a rim.

Craters cover nearly all parts of Mars. Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. There are many kinds of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>

<gallery class="center" widths="380px" heights="360px">

File:55252 1385craterfloorbrains.jpg|Crater floor with brain terrain

File:ESP 055252 1385brainscolorclose.jpg|Edge of crater with brain terrain on its floor

File:52030 1560crater.jpg|Average crater showing layers

File:54774 1700colorcraterejecta.jpg|Crater and part of its ejecta

File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.
File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.

File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.
File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

File:61167 1735crater.jpg|Crater with thin ejecta The color strip for HiRISE images is only in the center of images.

</gallery>

[[File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet.]]

New, small crater We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref> <ref>https://www.sciencedirect.com/science/article/abs/pii/S0019103513001693?via%3Dihub</ref> <ref>Daubar, I., et al. 2013. The current martian cratering rate. Icarus. Volume 225. 506-516. </ref>

==Hellas Floor Features==

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.
The exact origin of these shapes is unknown at present.

The Hellas floor contains strange-looking features that look like some sort of abstract art. One such feature is called "banded terrain." <ref>Diot, X., et al. 2014. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars. Planetary and Space Science: 101, 118-134.</ref> <ref>http://www.nasa.gov/mission_pages/MRO/multimedia/20070717-2.html | title=NASA - Banded Terrain in Hellas</ref> <ref>http://hirise.lpl.arizona.edu/ESP_016154_1420 | title=HiRISE | Complex Banded Terrain in Hellas Planitia (ESP_016154_1420)</ref> This terrain has also been called "taffy pull" terrain, and it lies near honeycomb terrain, another strange surface.<ref>Bernhardt, H., et al. 2018. THE BANDED TERRAIN ON THE HELLAS BASIN FLOOR, MARS: GRAVITY-DRIVEN FLOW NOT SUPPORTED BY NEW OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1143.pdf</ref> Banded terrain is found in the north-western part of the Hellas basin, the deepest section. The bands can be classified as linear, concentric, or lobate. Bands are typically 3–15km long and 3km wide. Narrow inter-band depressions are 65 m wide and 10 m deep.<ref>doi=10.1016/j.pss.2015.12.003 |title=Complex geomorphologic assemblage of terrains in association with the banded terrain in Hellas basin, Mars |journal=Planetary and Space Science |volume=121 |pages=36–52 |year=2016 |last1=Diot |first1=X. |last2=El-Maarry |first2=M.R. |last3=Schlunegger |first3=F. |last4=Norton |first4=K.P. |last5=Thomas |first5=N. |last6=Grindrod |first6=P.M. |last7=Chojnacki |first7=M. |121...36D |url=https://boris.unibe.ch/74530/1/Diot_Schlunegger.pdf </ref> How these shapes were made is still a mystery, although some explanations have been advanced.

[[File:55146 1425hellisfloorcropped.jpg|thumb|400px|center|Features on floor of Hellas impact basin.]]

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

<gallery class="center" widths="380px" heights="360px">
ESP 049330 1425honeycomb.jpg|Honeycomb terrain

File:ESP 057110 1365ridgescircles.jpg|Close view of concentric and parallel ridges, as seen by HiRISE under [[HiWish program]]

</gallery>

==Oxbow lakes and meanders==

An oxbow lake is a U-shaped lake that forms when a wide meander of a river is a cut off that makes a lake. This landform is so named for its distinctive curved shape, which resembles the bow pin of an oxbow.<ref>https://en.wikipedia.org/wiki/Oxbow_lake</ref> Finding them on Mars means that water probably flowed for a long time.

<gallery class="center" widths="380px" heights="360px">
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.

File:29054cutoff.jpg|Stream meander and cutoff, as seen by HiRISE under HiWish program. This is part of a major drainage system in the Idaeus Fossae region.
</gallery>

[[File: ESP 045779 1730meander.jpg|600pxr|Channel showing an old oxbow and a cutoff, as seen by HiRISE under HiWish program]]

Channel showing an old oxbow and a cutoff

[[File: ESP 045868 2245channel.jpg|600pxr|Channel, with meanders These meanders may have meandered a little more and then made oxbow lakes. Arrow points to a crater that was probably eroded by flowing water.]]
Channel, with meanders These meanders may have meandered a little more and then made oxbow lakes. Arrow points to a crater that was probably eroded by flowing water.

[[File:ESP 043623 2160meander.jpg|600pxr|Meanders Meanders are commonly formed in old river systems when the water is moving slowly.]]
Meanders They are formed in old river systems when the water is moving slowly.

[[File: ESP 052494 1395meanders.jpg|600pxr|Channel Arrows indicate evidence of a meander.]]

Channel Arrows indicate evidence of a meander.

==Channels==

[[File:ESP 056917 2170channels3.jpg|Old river channel with branches]]

Old river channel with branches and meanders

There are thousands of channels that were caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref> These channels have been seen in pictures from spacecraft for nearly 50 years. Current climate models do not support a warm climate on Mars; consequently, various ideas have been advanced to explain the existence of so many channels when it may have always been too cold for liquid water to exist on the surface. Some say they could be formed under ice sheets. Other scientists maintain that they could be produced in short periods after an asteroid impact warms the planet for thousands of years.

<gallery class="center" widths="380px" heights="360px">
File:41974 1740channellabeled.jpg|Old river valley in the Sinus Sabaeus quadrangle

WikiESP 033729 1410stream.jpg|Small branched channel

File:13882282 10207143921535802 7740003704272946655 nchannelinvalley.jpg|Channel in valley The valley was formed early on and then at a later time a small channel appeared. This arrangement means that water flowed here twice--once for the valley, another time for the small channel.

</gallery>

==Streamlined Shapes==

[[File:ESP 045860 2085streamlinedcroppedlabeled.jpg|Streamlined shapes made by running water]]

Streamlined shapes made by running water

Some locations on Mars show clear evidence of massive flows of water in the past. During these floods, the ground was carved into streamlined shapes. There are several ideas for how all this happened.<ref>https://www.uahirise.org/ESP_045833_1845</ref> It may have resulted from asteroid impacts into frozen ground. Under a cap of frozen ground there may have been vast buildups of water that were suddenly released.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057728 2090streamlined.jpg|Streamlined forms

File:58137 2090streamlined.jpg|Streamlined features These were created by the erosion of running water that flowed from the bottom of the image to the top. This direction can be determined by the way the erosion tails are pointed. The location is the Amenthes quadrangle

</gallery>

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel
These forms were shaped by running water.

==Inverted Terrain==

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Possible inverted streams, as seen by HiRISE under HiWish program]]

Often low areas can become high areas. This frequently happens with streams. An old stream channel may become filled with a hard, erosion resistant material like lava or large boulders. Later, erosion of the whole area may remove all the surrounding soft materials. But, the stream channel will be preserved because of the hard materials that were deposited in it. In the end, you are left with a feature which is elevated above the landscape, but has the shape of the original stream. Geologists will then call the stream “inverted.”

<gallery class="center" widths="380px" heights="360px">

Image:ESP_024997ridges.jpg|Possible inverted stream channels, as seen by HiRISE under HiWish program. The ridges were probably once stream valleys that have become full of sediment and cemented. So, they became hardened against erosion which removed surrounding material.

ESP 036362 2195inverted.jpg|Inverted stream channels on crater slope, as seen by HiRISE under HiWish program Location is [[Diacria quadrangle]].
</gallery>

[[File:ESP 055431 1430invertedstream.jpg|thumb|400px|center|Inverted Stream channel It was once a stream, now it is a curved ridge.]]

==Exhumed Craters==

[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]

Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."

Exhumed terrain appears to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> <ref> https://www.uahirise.org/PSP_001374_1805</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under and around it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

[[File:57652 2215exhumed.marspedaijpg.jpg|thumb|400px|left|This crater had been buried and now is being uncovered by erosion. Had it just been formed, it would have destroyed part of the layered formation that is on top of its right side (just to the left of the crater).]]

[[File:48057 1560craterlayersclose.jpg|thumb|400px|center|The small crater that sits in layers is being exhumed. If it had been made after the layers that it is sitting in, it would have destroyed some of the layered material.]]

==Pedestal Craters==

[[File:ESP 037528 2350pedestal.jpg |Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.

A Pedestal crater is a crater with its ejecta sitting above the surrounding terrain. Its ejecta form a raised platform (like a pedestal).<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> They are produced when an impact ejects material that forms an erosion-resistant layer. Consequently, the immediate area erodes more slowly than the rest of the region. Some pedestals are hundreds of meters above the surroundings. This means that hundreds of meters of material were eroded away. What remains is a crater and its ejecta blanket sitting above the surrounding ground. <ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 048021 2130pedestal2.jpg|Pedestal Crater with an odd ejecta pattern

Image: ESP 047615 1275pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program Top layer has protected the lower material from being eroded. Location is Hellas quadrangle, at 52.014° S and 110.651° E (249.349 W).

File:62242 2265pedestal.jpg|Pedestal crater
</gallery>

==Ridges==

[[File:36745 1905ridgesv2.jpg |Close view of ridges We are sure how these were formed, but we have come up with a few possibilities.]]

Close view of ridges We are sure how these were formed, but we have come up with a few possibilities.

Ridge fields are another feature that we do not yet fully understand.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref> <ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>
Hard ridges standing above the surroundings often meet at close to right angles. They may have something to do with cracks caused by impacts. Mineral laden water may then migrate up the cracks and harden. These fields can be quite complex and beautiful.

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.

File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

</gallery>

[[File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle ]]

Ridge network in Amazonis quadrangle

==Layers==

[[File:44507 1880longlayersdanielson.jpg|600pxr|Layers in Dannielson Crater, as seen by HiRISE under HiWish program]]

Layers of rocks and other materials are very common on Mars.<ref>https://www.uahirise.org/PSP_007820_1505 Layered Sediments in Hellas Planitia</ref> They are found in many low places like craters.<ref>https://www.uahirise.org/hipod/PSP_008930_1880</ref> The widespread occurrence of layering on the Red Planet has great significance. On Earth, much layering originates in bodies of water.<ref>Namowitz, S., Stone, D. 1975. Earth science The World We Live in. American Book Company. N.Y. </ref> If this is true, at least to some extent on Mars, then traces of past life might be found in layered formations. Indeed, much evidence has been gathered for the existence of lakes in craters and some canyons.
Whether layers were created under water or through ground water, water is still being debated. Probably ground water is at least partial responsible for many of the layers we observe on the planet. The existence of water in the ground is important for life on Mars. Most of the organic mass on the Earth is found under the surface. Likewise, Mars may have a great deal of life living under the surface. <ref>https://microbewiki.kenyon.edu/index.php/Deep_subsurface_microbes</ref> <ref>Amend, J.. A. Teske. 2005. Expanding frontiers in deep subsurface microbiology. Palaeogeography, Palaeoclimatology, Palaeoecology: Volume 219, Issues 1–2, 131-155.</ref> Many microbes live deep underground.<ref>Pedersen, K. 1993. The deep subterranean biosphere. Earth Science Reviews: 34, 243-260.</ref> <ref> Stevens, T., J. McKiney. 1995. Lithoautotrophic Microbial Ecosystems in Deep Basalt Acquifers. Science: 270, 450-454.</ref> <ref>Fredrickson, J. , T. Onstott. 1996. Microbes Deep inside the Earth. Scientific American. October, 1996.</ref> Life under the Martian surface might find it easier since it would be protected from high levels of radiation.<ref>Boston, P., et al. 1992. On the Possibility of Chemosynthetic Ecosystems in Subsurface Habitats on Mars. Icarus: 95, 300-308.</ref> One recent study found that radiation from certain elements in the crust of Mars could have reacted with water in the ground to produce hydrogen. Hydrogen can supply chemical energy for life.<ref>http://astrobiology.com/2018/09/ancient-mars-had-right-conditions-for-underground-life.html</ref> <ref> Tarnas, J., et al. 2018 Radiolytic H2 Production on Noachian Mars: Implications for Habitability and Atmospheric Warming. Earth and Planetary Science Letters [https://doi.org/10.1016/j.epsl.2018.09.001</ref>

<gallery class="center" widths="380px" heights="360px">

File: 54763_1500layers2.jpg
File: 54763_1500layerscolor.jpg

File:59619 1845layers3.jpg|Close view of layers

File:59619 1845layers2labeled.jpg|Layers Different colors of the rocks means they contain different minerals.

ESP 048980 1725layers.jpg|Wide view of layers in Louros Valles, as seen by HiRISE under HiWish program Louros Valles is part of the Ius Chasma.
48980 1725layersclose2.jpg|Close view of layers in Louros Valles Note this is an enlargement of a previous image.

48980 1725layersclose.jpg|Close view of layers in Louros VallesNote this is an enlargement of a previous image.
ESP 048980 1725layersclosecolor.jpg|Close view of layers in Louros Valles Note this is an enlargement of a previous image.

File: 47421 1890bigbutte.jpg|Close view of layers, as seen by HiRISE under HiWish program. Box shows the size of a football field.
</gallery>

[[File:544858 1885topcloselayers5.jpg|thumb|400px|center|Close view of layers, as seen by HiRISE under HiWish program Location is Danielson Crater.]]

==Ribbed terrain==

Ribbed terrain consists of mostly elongated canyon-like forms. Some portions turn into mesas. It is created when small cracks become larger and larger. A crack in the surface of an ice-rich area will permit more of the ice to go into the thin Martian air because of increased surface area. This process of going directly form a solid to a gas phase is called sublimation. On Earth it is easily observed in the behavior of dry ice (solid carbon dioxide).

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows

[[File:28339 2245ribbbed.jpg|thumb|400px|center|Wide view of ribbed terrain.]]

[[File:ESP 025174 2245ribs.jpg|500pxr|Wide view of ribbed terrain.]]

Wide view of ribbed terrain.

[[File:25174 2245ribscolor.jpg|thumb|400px|center|Close, color view of ribbed terrain.]]

==Blocks and boulders forming==

Some places on Mars show rocks breaking into boulders or cube-shaped blocks.

[[File:26557joints.jpg|500pxr|Crossing joints, as seen by HiRISE under HiWish program]]

Crossing joints, as seen by HiRISE under HiWish program
<gallery class="center" widths="380px" heights="360px">
48144 1475layerscubes.jpg|Close view of layers, as seen by HiRISE under HiWish program Some of the layers are breaking up into large blocks
48144 1475cubes.jpg|Close view of layers Some layers are breaking up
</gallery>

[[File:26557rocksforming.jpg|Rocks forming|thumb|300px|left|Rocks forming]]

[[File:44757 2185fracturesblocks.jpg|thumb|300px|center|Blocks forming]]

[[File: 47577 1515blocks.jpg|thumb|400px|right|Surface breaking up into cube-shaped blocks]]

[[File: 46684 1280breaking.jpg|thumb|500px|center|Layers breaking up into boulders in Galle Crater, as seen by HiRISE under HiWish program]]

[[File:45377 2170blocks2.jpg|500pxr|Fractures forming large blocks Box shows size of a football field]]

Fractures forming large blocks Box shows size of a football field

==Volcanoes under ice==

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

Researchers believe they have found evidence that volcanoes erupt under ice on Mars.<ref>https://www.uahirise.org/ESP_071541_2200</ref> Such eruptions have been observed on the Earth. What seems to happen is that ice melts, the water escapes, and then the surface cracks and collapses. The resulting formation shows concentric fractures and large pieces of ground that seemed to have been pulled apart.<ref>Smellie, J., B. Edwards. 2016. Glaciovolcanism on Earth and Mars. Cambridge University Press.</ref> Sites like this may have recently had held liquid water; therefore, they may be good places to search for evidence of life.<ref name="Levy, J. 2017">Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185-194.</ref><ref>University of Texas at Austin. "A funnel on Mars could be a place to look for life." ScienceDaily. ScienceDaily, 10 November 2016. <www.sciencedaily.com/releases/2016/11/161110125408.htm>.</ref>

[[File:25755 2200collapse.jpg|thumb|400px|left|Close view of fractures from volcano under ice.]]

[[File:25755 2200tiltedlayers.jpg|thumb|400px|center|Close view of fractures from volcano under ice.]]

==Recurrent slope lineae==

Recurrent slope lineae are small, narrow, dark streaks on slopes that get longer in warm seasons. They may be evidence of liquid water.<ref>McEwen, A., et al. 2014. Recurring slope lineae in equatorial regions of Mars. Nature Geoscience 7, 53-58. doi:10.1038/ngeo2014</ref> <ref>McEwen, A., et al. 2011. Seasonal Flows on Warm Martian Slopes. Science. 05 Aug 2011. 333, 6043,740-743. DOI: 10.1126/science.1204816</ref> <ref>http://redplanet.asu.edu/?tag=recurring-slope-lineae|title=recurring slope lineae - Red Planet Report|website=redplanet.asu.edu|</ref> Evidence is still being gathered on this feature.

[[File:49955 1665rslcolorarrows (1).jpg|500pxr|Recurrent slope lineae (RSL) They form in warm seasons.]]

Recurrent slope lineae (RSL) They form in warm seasons.

==Notes about pictures==

Most pictures from spacecraft are enhanced. The surface of Mars shows little contrast. Consequently, in order to see more detail, contrast is enhanced by a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. This process makes a huge difference for some features like dark slope streaks. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red. Displaying colors in this way allows us to better identify rocks and minerals. Usually, color images are constructed in one of two ways. An IRB image assigns the output from the infrared channel to the color red, the wide red channel to the color green, and the blue-green channel to the color blue. On the other hand, a RGB image has the output of the broad red channel displayed as red, the blue-green channel as green, and a synthetic blue channel (blue-green minus part of the red) as blue. The wavelengths of these channels are: RED: 570-830 nanometers BG: <580 nanometers IR: >790 nanometers. One nanometer is equal to one billionth of a meter (0.000 000 001 m). HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.[12]

HiRISE images are about 5 km wide, but only have a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

==How to suggest image==

To suggest a location for HiRISE to image visit the site at http://www.uahirise.org/hiwish

In the sign up process you will need to come up with an ID and a password. When you choose a target to be imaged, you have to pick and exact location on a map and write about why the image should be taken. If your suggestion is accepted, it may take 3 months or more to see your image. You will be sent an email telling you about your images. The emails usually arrive on the first Wednesday of the month in the late afternoon.

==Notes to teachers==

This article goes along with the video Features of Mars with HiRISE under HiWish program at https://www.youtube.com/watch?v=b7q1Xyz_LBc

==References==
{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.jpl.nasa.gov/missions/viking-1/ OP Lunch Talk #10: HiWish, public suggestion targeting web tool for Mars imaging with MRO/HIRISE]

*[https://www.youtube.com/watch?v=0fQHEay-Yas&list=PLn0lnGc1Saik-yyWpeec3AWz9NgdtxDAF&index=122 How to Explore Mars without Leaving Your Chair - Jim Secosky - 23rd Annual Mars Society Convention]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]
*[[Viking 2]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

HiWish program

2023-03-04T22:51:31Z

Suitupandshowup: /* Pingos */ added image

HiWish is a NASA program in which anyone can suggest a place for the [[High Resolution Imaging Science Experiment (HiRISE)]] camera on the [[Mars Reconnaissance Orbiter]] to image.<ref>http://www.marsdaily.com/reports/Public_Invited_To_Pick_Pixels_On_Mars_999.html |title=Public Invited To Pick Pixels On Mars |date=January 22, 2010 |publisher=Mars Daily</ref> <ref>http://www.astronomy.com/magazine/2018/08/take-control-of-a-mars-orbiter</ref> <ref>http://www.planetary.org/blogs/guest-blogs/hiwishing-for-3d-mars-images-1.html</ref> It started in January 2010. Three thousand people signed up in the first few months of the program.<ref>Interview with Alfred McEwen on Planetary Radio, 3/15/2010</ref> <ref>http://www.planetary.org/multimedia/planetary-radio/show/2010/384.html|title=Your Personal Photoshoot on Mars?|website=www.planetary.org|</ref> By February 2020, 9,726 had signed up and 24,059 suggestions had been submitted for targets in each of the 30 quadrangles of Mars. A that point 10,318 images had been taken.<ref> https://www.jpl.nasa.gov/missions/viking-1/</ref> <ref> OP Lunch Talk #10: HiWish, public suggestion targeting web tool for Mars imaging with MRO/HIRISE</ref> The first images were released in April 2010.<ref>http://topnews.net.nz/content/23052-nasa-releases-first-eight-hiwish-selections-people-s-choice-mars-images |title=NASA releases first eight "HiWish" selections of people's choice Mars images |date=April 2, 2010 |publisher=TopNews |accessdate=January 10, 2011 |archive-url=https://www.webcitation.org/6Gop7RR0c?url=http://topnews.net.nz/content/23052-nasa-releases-first-eight-hiwish-selections-people-s-choice-mars-images |</ref> Some of the images from HiWish were used for three talks at the 16th Annual International Mars Society Convention. Below are some of the over 4,224 images that have been released from the HiWish program as of March 2016.<ref>McEwen, A. et al. 2016. THE FIRST DECADE OF HIRISE AT MARS. 47th Lunar and Planetary Science Conference (2016) 1372.pdf</ref>

==Landslides==

[[File:ESP 057191 2150landslidecropped.jpg|Landslide]]

Landslides have been observed on Mars. They may be a little different since the gravity of Mars is only about one third as that of the Earth.
<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 1585landslide.jpg|Landslide
File:ESP 043963 1550landslide.jpg|Landslide
</gallery>

==Hollows==

[[File:28207 2250hollowsarrows.jpg|Hollows]]

Hollows make strange, beautiful landscapes. The hollows are believed to be produced when ice leaves the ground and the remaining dust is blown away. There is much water frozen in the ground. Water is carried around the planet frozen on dust grains that fall to the ground and make up what is called “mantle.” Mantle is produced when the climate is such that there is a lot of dust and moisture in the atmosphere. During those times, water will freeze onto the dust particles. Eventually, the particles will be too heavy and fall to the surface. In addition, it may snow on Mars.
The mantle covers wide expanses. It has a smooth appearance. It covers the irregular, created surface of the planet.

<gallery class="center" widths="380px" heights="360px">

File:46325 2225hollows4.jpg|Hollows

File:ESP 046325 2225hollowsmiddlelabeled.jpg|Hollows

</gallery>

==Mud Volcanoes==

[[File:53381 2265mud.jpg|Mud volcanoes]]

Mud volcanoes They may have come through a zone of weakness in the rock here

Mud volcanoes are very common in a place on Mars called the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Mud that formed the volcanoes comes from a depth underground that is deep enough to be protected from radiation. The radiation level at the surface would kill most organisms over time. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

<gallery class="center" widths="380px" heights="360px">
File:570770 2100coneslabeled.jpg|Mud volcanoes

File:52050 2200mudvolcanoes.jpg|Mud volcanoes
File:ESP 043580 2120mud.jpg|Wide view of field of mud volcanoes
</gallery>

==Volcanic vents==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

[[File:ESP 030440 1945ventcropped.jpg|Volcanic vent]]

Volcanic vent

==Lava Flows==

[[File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons]]

Lava flow on Olympus Mons

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Large volcanoes in the [[Tharsis]] region show many overlapping lava flows. Lava flows can also move around and create what appear to be layers, especially if it behaves like water. Basalt flows are very fluid.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="380px" heights="360px">
File:44828 2030lavaflow.jpg|Lava flows These are common in large sections of Mars.

File:ESP 044840 1620lavaflow.jpg|Lava flow

File:WikiESP 035095 1975lavalobestharsiswide.jpg|Old and young lava flows

File:68460 1945laveolympus.jpg|Lava flowing down a slope from [[Olympus Mons]]

File:68460 1945lavechannel.jpg|Lava channel from Olympus Mons

</gallery>

==Rootless Cones==

[[File:40162 2065conesarrows2.jpg|Rootless cones ]]

Rootless cones

Rootless Cones are thought to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam. The resulting steam explosion produces a ring or cone. Such features are common in certain locations on the Earth. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form. Sometimes a wake is made as the lava moves along the surface.

<gallery class="center" widths="380px" heights="360px">

File:45384 2065cones2.jpg|Rootless cones
File:45384 2065cones.jpg|Rootless cones Here, lava has moved over ice-rich ground from the upper right to the lower left of the picture.
File:58610 2100coneswakeslabeled.jpg|Close view of wake of a rootless cone
File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones

</gallery>

==Dikes==

[[File:ESP 045981 2100dike2.jpg|Dike]]

Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

Dikes show as mostly straight ridges. They are made when magma flows along cracks or faults in the ground. This part of the process happens under the ground. Later erosion will remove the weaker materials around the dike. What is left is a narrow wall of rock.<ref> "Characteristics and Origin of Giant Radiating Dyke Swarms". MantlePlumes.org.</ref> On Mars many faults are due to stretching of the crust. The mass of huge volcanoes pull at the crust until it cracks.

[[File:ESP 046403 2095dikecropped.jpg|thumb|400px|center|Dike in [[Syrtis Major quadrangle]]]]

==Troughs==

[[File:ESP 051781 2035troughs.jpg |Troughs]]

Troughs are common on Mars. They are due to the great weight of several huge volcanoes on Mars. The mass of these structures has caused the crust to stretch. That tension made the crust break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="380px" heights="360px">

File:56910 2100trough.jpg|Group of troughs

File:Troughs in Elysium Planitia.jpg|Troughs showing layers Hard cap rock is at the surface. The center section is in color. With HiRISE only a strip in the middle is in color.

File:ESP 057834 2005troughmesa.jpg|Troughs cutting through mesa, as seen by HiRISE under HiWish program
</gallery>

==Faults==

Faults are visible in some parts of Mars. They are most noticeable in places where many layers exist. Sometimes their presence is known because they can change the direction of stream channels.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater

[[File:60331 1880faultslabeled2.jpg|thumb|300px|left|Faults in layered terrain]]

[[File:27615 1880faults.jpg|thumb|300px|center|Faults in layered terrain]]

[[File:71634 1880layersfaultslabeled.jpg|thumb|300px|Faults in layers in Danielson Crater]]

<gallery class="center" widths="380px" heights="360px">
File:26086 1800fault.jpg|Fault that changed direction of stream. CTX image is included for context.

</gallery>

==Mesas and layers==

[[File:58788 1890layerscolorlabeled2.jpg|Mesa with layers]]

Mesa with layers

On Mars much layered terrain is visible. Layered rock is formed from separate events. For example, a layer may be formed at the bottom of a lake. Later, lava may cover that layer, thus making a new layer—one that is harder. In times erosion may remove nearly all the layers. But, sometimes remnants are left behind, especially if they are topped off by a hard cap rock. Lave flows can make cap rock. The cap rock will protect the underlying rocks from erosion. Cap rock often breaks up into large boulders. Sometimes the boulders are in the shape of cube-shaped blocks. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="380px" heights="360px">
File:58563 2225mesa.jpg|Mesa

File:58524 1820layerscolor4labeled.jpg|Mesa with layers

File:58919 1935mesalayers.jpg|Mesa with layers Box is the size of a football field.

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte The box shows the size of a football field.

</gallery>

==Layers in Craters==

[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

Craters can contain mesas that show layers. It is believed that these layers are the remnants of material that once covered a wide area, but is now only in protected places like inside craters. The layers mean that different events laid down the layers. These layers are probably due to latitude dependent mantle that falls from the sky at different times. Mantle is mostly from ice-coated dust falling from the sky under certain climate conditions. Wind, acting over millions of years, will shape the material in craters into smooth mesas.

<gallery class="center" widths="380px" heights="360px">

File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>

File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.

File:28207 2250cratermesa.jpg|Color view of layers in a mesa in a crater
</gallery>

==Dipping Layers==

[[File:46180 2225dippinglayers.jpg|Dipping layers and brain terrain (right side of picture)]]

Dipping layers and brain terrain (right side of picture)

A common feature on Mars is “dipping layers.” They are groups or stacks of layers that seem to be leaning against something steep like a crater wall or the wall of a mesa. It is believed that they represent material that once covered a wide area, but is now only in protected places. The layers mean that different events laid down the layers. These layers are probably due to latitude dependent mantle that falls from the sky at different times. Mantle is mostly from ice-coated dust falling from the sky under certain climate conditions. These dipping layers are often smooth from the action of the wind over millions of years.

[[File:ESP 038002 1375dipping.jpg|thumb|300px|left|Wide view of dipping layers against slopes]]

[[File:ESP 062082 2175dippingcropped.jpg|thumb|300px|right|Dipping layers These may be the remains of past layers of mantle that covered the whole area.]]

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210pyramidsismenius.jpg|Dipping layers against a mesa wall.

</gallery>

[[File:ESP 019778 1385pyramid.jpg|Set of dipping layers in crater]]

Set of dipping layers in crater

==Boulders==

[[File:28497 2250boulderslabeled.jpg|Boulders near hollows]]

Boulders near hollows

Large, house-sized boulders are widespread on the Red Planet. Mars has an old surface—billions of years old. In that time, erosion has broken down many hard rocks. Most of Mars is covered with hard volcanic rock. The dark volcanic rock basalt covers most of the Martian surface. When it breaks, it first forms large boulders.

<gallery class="center" widths="380px" heights="360px">

File:55119 2080mesasinglelabeled.jpg|Mesa The top has a hard cap rock that protects the underlying rocks from erosion. Boulders are visible in the image.
File:58904 2240brainsboulders.jpg|Boulders and brain terrain
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas Box shows size of football field.
49950 2125ridgesboulders.jpg|Close view of ridge networks, as seen by HiRISE under HiWish program Many boulders are visible.

File:ESP 045415 2220boulders.jpg|Color view of boulders

45575 2535dunebouldertracks.jpg|Boulders and tracks, as seen by HiRISE under HiWish program The arrows show a boulders that have produced a track by rolling down dune.

</gallery>

[[File: 47157 1850boulders.jpg|Boulders and their tracks from rolling down a slope Arrows show two boulders at the end of their tracks.]]

Boulders and their tracks from rolling down a slope Arrows show two boulders at the end of their tracks.

[[File:59458 2145boulders.jpg|Color view of boulders]]

Boulders formed from break up of a mesa

==Yardangs==

[[File:61167 1735yardangs.jpg|Yardangs]]

Yardangs

Yardangs develop from fine-grained material. They are shaped by the wind and show the direction of the dominant winds.<ref> Bridges, Nathan T.; Muhs, Daniel R. (2012). "Duststones on Mars: Source, Transport, Deposition, and Erosion". Sedimentary Geology of Mars. pp. 169–182. doi:10.2110/pec.12.102.0169. ISBN 978-1-56576-312-8.</ref> <ref> https://www.uahirise.org/ESP_039563_1730</ref> Volcanoes supply much of this fine-grained material. Yardangs are especially widespread in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because yardangs exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref> The largest single source of dust in the air on Mars comes from the Medusae Fossae Formation.<ref> Ojha, Lujendra; Lewis, Kevin; Karunatillake, Suniti; Schmidt, Mariek (2018). "The Medusae Fossae Formation as the single largest source of dust on Mars". Nature Communications. 9 (1): 2867.</ref>

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 047915 1815yardangs.jpg|Wide view of yardangs
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs
</gallery>

==Ring-Mold Craters==

[[File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.]]

Ring mold craters They may contain ice.

Ring-mold craters are a type of small impact crater that looks like the ring molds used in baking.<ref>https://link.springer.com/referenceworkentry/10.1007/978-1-4614-9213-9_318-1</ref> <ref>kress, A., J. Head. 2008. Ring‐mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophysical Research Letters Volume 35, Issue 23</ref> One popular idea for their formation is an impact into ice--Ice that is covered by a layer of debris.<ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL035501</ref> They are found in parts of Mars that contain buried ice. Laboratory experiments confirm that impacts into ice end in a "ring mold shape." Other evidence for this contention is that they are bigger than other craters in which an asteroid impacted solid rock implying that the material entered by the impact was softer than rock (as ice is). Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill—both thought to have buried ice under a thin layer of rocky debris<ref>Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8</ref> <ref>Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209</ref> <ref>Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379</ref> Ring-mold craters may be an easy way for future colonists of Mars to find water ice because some may contain ice that is relatively pure. And, since it was generated during a rebound, ice may have been brought up from below the surface; hence, less digging or drilling may be required to gather ice.

<gallery class="center" widths="380px" heights="360px">

26055ringmoldcrater.jpg|Close view of ring mold crater.
File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
</gallery>

==Dark Slope Streaks==

[[File:55480 2060streaksobstacles.jpg|Some of the streaks here were affected by boulders.]]

Streaks around a mound. Some of the streaks here were affected by boulders.

[[File:55107 1930streaksboulders2.jpg|thumb|300px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

[[Dark slope streaks]] are avalanche-like features common on dust-covered slopes.<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. 2010. Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> Although they appear much darker than their surroundings, the darkest streaks are only about 10% darker than their backgrounds. Streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046188 1855streakslabeled2.jpg|Streaks along a mesa
File:ESP 045435 2055troughlayers.jpg|Dark slope streaks in a trough

</gallery>

[[File:23677streakslabeled.jpg|Streaks often start at a small point and then expand down slope.]]

Streaks often start at a small point and then expand down slope. Many streaks may be caused by the action of solid carbon dioxide (dry ice). Under conditions on Mars, during the night dry ice forms under the surface. When the ground warms in the morning, the dry ice turns into a gas and creates a wind that disturbs the dust grains. If situated on a steep slope, an avalanche of bright dust moves down and uncovers the dark undersurface.<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al. 2022. Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks. JGR Planets. Volume127, Issue4. e2021JE006988</ref>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface. As a result, dark underlying material is exposed.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit.<ref>https://www.uahirise.org/ESP_042201_1715</ref> They helped scientists by blowing dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> Dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">

File:ESP 036297 2370devils.jpg|Dust Devil Tracks

File:ESP 036631 2335devilsbottom.jpg|Dust devil tracks in Casius quadrangle

</gallery>

[[File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.|500pxr|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.]]

Dust devil tracks in Casius quadrangle

==Dunes==

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Some places on Mars have many beautiful dark dunes. Rovers on the Martian surface confirmed earlier ideas that the dunes are composed of sand made from the volcanic rock basalt..<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> Dunes are often covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring. As the frost disappears, different patterns can emerge on the dunes. Dunes can take on different colors because of slight chemical variations in the sand grains.

The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars. However, we must remember that its atmosphere is only about 1 % as dense as the Earth's. Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).<ref> https://www.space.com/30663-the-martian-dust-storms-a-breeze.html</ref>

[[File:ESP 046378 1415dunescolor.jpg|thumb|300px|right|Dunes]]

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:59628 1275dunes.jpg|Dunes in Hellas quadrangle

</gallery>

[[File:58089 2170duneswidemarsp.jpg |600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle|Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle]]

Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle

[[File:59658 1415dunes.jpg|600pxr|Dunes The location is the Noachis quadrangle |Dunes The location is the Noachis quadrangle]]

Dunes The location is the Noachis quadrangle

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Glaciers==

[[File:ESP 018857 2225alpineglacier.jpg|Glacier moving out of a valley This is similar to glaciers on the Earth]]

Glacier moving out of a valley This is similar to glaciers on the Earth

Glaciers have been described as “rivers of ice.” With glaciers there is a downward movement that can be noticed by examining patterns on their surface. There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. Exposed ice will not last long under present climate conditions on Mars, but just a few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref> Researchers noticed decades ago that many forms on Mars resembled glaciers on the Earth. As scientists received pictures with greater resolution, the shapes and patterns visible on their surfaces looked like the flows visible in the Earth’s glaciers.

<gallery class="center" widths="380px" heights="360px">

File:ESP 050176 2245glacier.jpg|Glacier moving out of a valley
File:ESP 045085 2205flowlabeled.jpg|Alpine Glacier moving out of a valley and then moving onto Lineated valley fill (LVF) The LVF contains ice under a layer of insulating debris. Lineated Valley Fill is considered to be a glacier.
File:47193 1440glacier.jpg|Glaciers
File:35934 2215brainsglacier.jpg|End of an old glacier. Most of the ice is gone, but the material moved by the glacier is formed into an arc.
</gallery>

<gallery class="center" widths="380px" heights="360px">
ESP 045505 1400flow.jpg|Flow feature that was probably a glacier

Image:ESP_020319flowcontext.jpg|Context for the next image of the end of a glacier.

Image:ESP_020319flowsclose-up.jpg|Close-up of the area in the box in the previous image. This may be called by some the terminal moraine of a glacier. For scale, the box shows the approximate size of a football field.

Image:Tongue23141.jpg|Tongue-shaped glacier, Ice may exist in the glacier, even today, beneath an insulating layer of dirt.

Image:Tongue23141close.jpg|Close-up of tongue-shaped glacier Resolution is about 1 meter, so one can see objects a few meters across in this image.

</gallery>

==Lobate Debris Aprons (LDA’s) ==

Lobate debris aprons (LDAs), first seen by the Viking Orbiters, look like piles of rock debris below cliffs.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. </ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> They slope away from mesas and buttes.
The Mars Reconnaissance Orbiter's Shallow Radar found pure ice in LDA’s around many mesas.<ref>http://www.planetary.brown.edu/pdfs/3733.pdf</ref> Based on this data, LDA’s are considered to be glaciers covered with a thin layer of rocks.<ref>Head, J. et al. 2005. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars. Nature: 434. 346-350</ref><ref>http://www.marstoday.com/news/viewpr.html?pid=18050</ref> <ref>http://news.brown.edu/pressreleases/2008/04/martian-glaciers</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>Holt, J. et al. 2008. Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2441.pdf</ref> <ref>Petersen, E., et al. 2018. ALL OUR APRONS ARE ICY: NO EVIDENCE FOR DEBRIS-RICH “LOBATE DEBRIS APRONS” IN DEUTERONILUS MENSAE 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2354.</ref>

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 036580 2260ldacropped.jpg|Lobate debris apron
File:ESP 036619 2275ldacropped.jpg|Lobate debris apron
</gallery>

==Lineated Valley Fill (LVF) ==

Lineated valley floor consists of many mostly parallel ridges and grooves on the floors of many channels. The ridges and grooves look like they moved around obstacles. They are believed to be ice-rich. Some glaciers on the Earth show such features.<ref> https://www.uahirise.org/ESP_026414_2205</ref>
[[File:ESP 052138 1435lvf.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

[[File:ESP 046061 2190lvf.jpg|thumb|300px|right|Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)]]
[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of Lineated Valley Fill (LVF)]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 055408 1375lvf2.jpg|Lineated Valley Fill
File:ESP 046840 2130lvf.jpg|Lineated Valley Fill in valley
File:53630 2195lvf.jpg|Lineated Valley Fill
File:56544 2200lvfbrains.jpg|Lineated Valley Fill
File:56544 2200lvflabeled.jpg|Lineated Valley Fill
</gallery>

==Concentric Crater Fill (CCF) ==

[[Image: ESP_046622_1365ccf.jpg |Concentric Crater Fill Lat: 43.1° S Long: 219.8°E (140.2 W]]

Concentric Crater Fill Located at Lat: 43.1° S Long: 219.8°E (140.2 W

Concentric crater fill is believed to be an ice-rich feature on the floors of many Martian craters. The floor of craters exhibiting CCF is almost totally covered with many parallel ridges.<ref>https://web.archive.org/web/20161001224229/http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185 </ref> It is common in the mid-latitudes of Mars,<ref>Dickson, J. et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> and is widely accepted as caused by glacial movement.<ref>Head, J. et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for late Amazonian obliquity-driven climate change. Earth Planet. Sci Lett: 241. 663-671.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res.: 112.</ref> The [[Ismenius Lacus quadrangle]] contains examples of concentric crater fill.

<gallery class="center" widths="380px" heights="360px">
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill

File:46688 1365ccf2.jpg|Close view of Concentric Crater Fill (CCF)
</gallery>

==Brain Terrain==

[[File:45917 2220brainsopenclosed.jpg|Open and closed brain terrain]]

Open and closed brain terrain The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>

Brain terrain is an area of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists. There are two kinds—open and closed. Brain terrain is thought to begin with cracks that get larger and larger as ice leaves the ground. When ice is exposed on Mars under its present climate conditions, ice goes directly into the air. That process of going from a solid to a gas—instead of first to a liquid—is called sublimation. With this process, the cracks get wider and wider until a complex of high and low areas remains. <ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:25246brainseroding.jpg|Brain terrain
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle The closed cell brain terrain may still hold an ice core,<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> so it may a source of water for future colonists.
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle

File:53630 2195brainslvf.jpg|Brains on surface of leaneted valley fill
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ice Cap Layers==

[[File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019. ]]

Layers in northern ice cap This photo was named picture of the day for January 21, 2019.

The northern ice cap of layers displays many layers. These layers are visible when a valley cuts through the cap. Layers in the ice cap, as with other exposures of layers across the planet, are formed from frequent dramatic changes in the climate. These changes are the result of great changes in the rotational axis or tilt of the planet. Mars does not have a large moon to stabilize its' tilt; hence the planet has huge variations in its tilt (maybe from its present Earth-like tilt to over twice the Earth’s).

<gallery class="center" widths="380px" heights="360px">

File:ESP 061636 2620nicecaplayerscroppedlabeled.jpg|Northern ice cap layers
File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

</gallery>

==Spiders==

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

Some features have been called spiders because they can resemble spiders. The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> <ref>https://www.uahirise.org/</ref> This process results in the appearance of dark plumes that are often blown in one direction by local winds. Besides producing plumes, dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>
The process of making spiders was demonstrated in laboratory simulations involving slabs of dry ice and glass spheres of different sizes.<ref>https://www.nature.com/articles/s41598-021-82763-7.pdf</ref> <ref>McKeown, L., et al. 2021. The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric
pressure. Scientific Reports.</ref> <ref>https://www.livescience.com/spiders-on-mars-explained-dry-ice.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref>

<gallery class="center" widths="380px" heights="360px">

File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program

</gallery>

==Mantle==

[[File:37167 1445mantlelabeled.jpg|Mantle Mantle covers the surface irregularities on Mars]]

Mantle Mantle covers the surface irregularities on Mars

Mantle on Mars appears as a smooth surface. It covers the normal irregular surface of the planet. It is often called “Latitude Dependent Mantle” because it occurs at certain distances from the equator (certain latitudes).<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> This latitude dependent mantle is believed to fall from the sky. During certain climatic conditions, moisture from the air will freeze onto dust particles. When they become too heavy, these particles fall to the ground. Snow may also fall on to the mantle. So, mantle consists of ice with dust. Since Mantle has a widespread distribution, it may be a major source of water for future colonists. Sometimes mantle displays layers because it was deposited at different times. The climate of Mars has changed many times due to a lack of a large moon. Our Earth’s moon is very massive and that helps to control the tilt of the rotational axis of our Earth. In other words, our moon keeps our planet’s tilt from changing much. Changes in the tilt of a planet will cause major changes in climate.

<gallery class="center" widths="380px" heights="360px">

File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program

</gallery>

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.

==Polygons==

[[File:56942 1075icepolygonslabeled2.jpg|Polygons]]

Polygons

Many surfaces on Mars have polygon shapes. These areas are sometimes called “polygonal patterned ground.” The polygons can be of different shapes and sizes—often very beautiful. They are believed to be caused by ice in the ground because they occur on the Earth where there is ice in the ground.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction.<ref>https://www.uahirise.org/ESP_066782_1110</ref> <ref>https://www.uahirise.org/ESP_047247_1150</ref>

In the future they may help point us to supplies of ice for colonists. The locations of polygons will provide evidence for us to make detailed maps for locations of water before we send crews to live there.

<gallery class="center" widths="380px" heights="360px">

File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons that shows polygons of varying sizes. Dark lines are defects in processing.
File:56148 1145polygons.jpg|Close view of polygons

File:ESP 043821 2555dryice.jpg|Field of dunes defrosting Black areas are free of frost, so the dark of the dunes shows up. White portions of dunes are still covered with frost.

File:ESP 043821 2555dryicecolor.jpg|Close view of parts of two dunes showing white parts with frost. The polygon surface they sit on still has frost in the low areas.

</gallery>

[[File:43821 2555dunesdefrosting2.jpg|Defrosting dune--white areas still contain frost]]

Defrosting dune--white areas still contain frost. Frost is in low parts of polygons.

==Scalloped Terrain==

[[File:37461 2255scallopslabeled2.jpg|Scalloped terrain This feature is important it may point future colonists to water supplies.]]

Scalloped terrain This feature is important it may point future colonists to water supplies.

Scalloped topography or terrain is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region called “Utopia Planitia.”<ref>last1 = Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 |</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> This terrain displays shallow, rimless depressions with scalloped edges--commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>http://www.uahirise.org/ESP_038821_1235</ref> <ref>Dundas, C., et al. 2015. Modeling the development of martian sublimation thermokarst landforms. Icarus: 262, 154-169.</ref> Scalloped topography may be of great importance for future colonization of Mars because radar studies reveal it is ice-rich.<ref>"Dundas, C. 2015" Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Stuurman, C., et al. 2016. SHARAD reflectors in Utopia Planitia, SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars. Geophysical Research Letters, Volume 43, Issue 18, 28 September 2016, Pages 9484–9491.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia
File:37461 2255scallopedclose.jpg|Scalloped terrain
</gallery>

==Pingos==

[[File: ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)]]

Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)

For many years, Pingos were believed to be present on Mars. Since they contain pure water ice, they would be a great source of water for future colonists on Mars. One picture from HiRISE under the HiWish program was thought to be a pingo.

<gallery class="center" widths="380px" heights="360px">

File:76854 2220pingo.jpg|Possible pingos. Pingos should look like mounds. Some will have cracks that formed when the water inside expanded as it froze.

</gallery>

File:76854 2220pingo.jpg

==Gullies==

[[File:50858 1435gullylabeled.jpg|Gullies with parts labeled--Alcove, Channel, Apron]]

Gullies with parts labeled--Alcove, Channel, Apron

[[Martian gullies]] are narrow channels and their associated downslope deposits. They are found on steep slopes. Most are seen on the walls of craters. Many are visible near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref >Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. For many years, gullies were thought to be caused by recent running water. But since some are being formed today, even when the climate of Mars is too cold for running water to exist on the surface, there must be another cause. After more observations, it was shown that pieces of dry ice moving down slopes could cause them. Nevertheless, some scientists think that in the past, water may have been involved in their formation.

<gallery class="center" widths="380px" heights="360px">
File:ESP 046386 1420gullies.jpg|Gullies

File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program Only part of the picture appears in color because the camera only produces color in a center strip.

</gallery>

[[File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>]]

Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>

==Craters==

[[File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.]]

This is a fairly young crater as it still shows ejecta, layers, and a rim.

Craters cover nearly all parts of Mars. Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. There are many kinds of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>

<gallery class="center" widths="380px" heights="360px">

File:55252 1385craterfloorbrains.jpg|Crater floor with brain terrain

File:ESP 055252 1385brainscolorclose.jpg|Edge of crater with brain terrain on its floor

File:52030 1560crater.jpg|Average crater showing layers

File:54774 1700colorcraterejecta.jpg|Crater and part of its ejecta

File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.
File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.

File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.
File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

File:61167 1735crater.jpg|Crater with thin ejecta The color strip for HiRISE images is only in the center of images.

</gallery>

[[File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet.]]

New, small crater We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref> <ref>https://www.sciencedirect.com/science/article/abs/pii/S0019103513001693?via%3Dihub</ref> <ref>Daubar, I., et al. 2013. The current martian cratering rate. Icarus. Volume 225. 506-516. </ref>

==Hellas Floor Features==

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.
The exact origin of these shapes is unknown at present.

The Hellas floor contains strange-looking features that look like some sort of abstract art. One such feature is called "banded terrain." <ref>Diot, X., et al. 2014. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars. Planetary and Space Science: 101, 118-134.</ref> <ref>http://www.nasa.gov/mission_pages/MRO/multimedia/20070717-2.html | title=NASA - Banded Terrain in Hellas</ref> <ref>http://hirise.lpl.arizona.edu/ESP_016154_1420 | title=HiRISE | Complex Banded Terrain in Hellas Planitia (ESP_016154_1420)</ref> This terrain has also been called "taffy pull" terrain, and it lies near honeycomb terrain, another strange surface.<ref>Bernhardt, H., et al. 2018. THE BANDED TERRAIN ON THE HELLAS BASIN FLOOR, MARS: GRAVITY-DRIVEN FLOW NOT SUPPORTED BY NEW OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1143.pdf</ref> Banded terrain is found in the north-western part of the Hellas basin, the deepest section. The bands can be classified as linear, concentric, or lobate. Bands are typically 3–15km long and 3km wide. Narrow inter-band depressions are 65 m wide and 10 m deep.<ref>doi=10.1016/j.pss.2015.12.003 |title=Complex geomorphologic assemblage of terrains in association with the banded terrain in Hellas basin, Mars |journal=Planetary and Space Science |volume=121 |pages=36–52 |year=2016 |last1=Diot |first1=X. |last2=El-Maarry |first2=M.R. |last3=Schlunegger |first3=F. |last4=Norton |first4=K.P. |last5=Thomas |first5=N. |last6=Grindrod |first6=P.M. |last7=Chojnacki |first7=M. |121...36D |url=https://boris.unibe.ch/74530/1/Diot_Schlunegger.pdf </ref> How these shapes were made is still a mystery, although some explanations have been advanced.

[[File:55146 1425hellisfloorcropped.jpg|thumb|400px|center|Features on floor of Hellas impact basin.]]

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

<gallery class="center" widths="380px" heights="360px">
ESP 049330 1425honeycomb.jpg|Honeycomb terrain

File:ESP 057110 1365ridgescircles.jpg|Close view of concentric and parallel ridges, as seen by HiRISE under [[HiWish program]]

</gallery>

==Oxbow lakes and meanders==

An oxbow lake is a U-shaped lake that forms when a wide meander of a river is a cut off that makes a lake. This landform is so named for its distinctive curved shape, which resembles the bow pin of an oxbow.<ref>https://en.wikipedia.org/wiki/Oxbow_lake</ref> Finding them on Mars means that water probably flowed for a long time.

<gallery class="center" widths="380px" heights="360px">
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.

File:29054cutoff.jpg|Stream meander and cutoff, as seen by HiRISE under HiWish program. This is part of a major drainage system in the Idaeus Fossae region.
</gallery>

[[File: ESP 045779 1730meander.jpg|600pxr|Channel showing an old oxbow and a cutoff, as seen by HiRISE under HiWish program]]

Channel showing an old oxbow and a cutoff

[[File: ESP 045868 2245channel.jpg|600pxr|Channel, with meanders These meanders may have meandered a little more and then made oxbow lakes. Arrow points to a crater that was probably eroded by flowing water.]]
Channel, with meanders These meanders may have meandered a little more and then made oxbow lakes. Arrow points to a crater that was probably eroded by flowing water.

[[File:ESP 043623 2160meander.jpg|600pxr|Meanders Meanders are commonly formed in old river systems when the water is moving slowly.]]
Meanders They are formed in old river systems when the water is moving slowly.

[[File: ESP 052494 1395meanders.jpg|600pxr|Channel Arrows indicate evidence of a meander.]]

Channel Arrows indicate evidence of a meander.

==Channels==

[[File:ESP 056917 2170channels3.jpg|Old river channel with branches]]

Old river channel with branches and meanders

There are thousands of channels that were caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref> These channels have been seen in pictures from spacecraft for nearly 50 years. Current climate models do not support a warm climate on Mars; consequently, various ideas have been advanced to explain the existence of so many channels when it may have always been too cold for liquid water to exist on the surface. Some say they could be formed under ice sheets. Other scientists maintain that they could be produced in short periods after an asteroid impact warms the planet for thousands of years.

<gallery class="center" widths="380px" heights="360px">
File:41974 1740channellabeled.jpg|Old river valley in the Sinus Sabaeus quadrangle

WikiESP 033729 1410stream.jpg|Small branched channel

File:13882282 10207143921535802 7740003704272946655 nchannelinvalley.jpg|Channel in valley The valley was formed early on and then at a later time a small channel appeared. This arrangement means that water flowed here twice--once for the valley, another time for the small channel.

</gallery>

==Streamlined Shapes==

[[File:ESP 045860 2085streamlinedcroppedlabeled.jpg|Streamlined shapes made by running water]]

Streamlined shapes made by running water

Some locations on Mars show clear evidence of massive flows of water in the past. During these floods, the ground was carved into streamlined shapes. There are several ideas for how all this happened.<ref>https://www.uahirise.org/ESP_045833_1845</ref> It may have resulted from asteroid impacts into frozen ground. Under a cap of frozen ground there may have been vast buildups of water that were suddenly released.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057728 2090streamlined.jpg|Streamlined forms

File:58137 2090streamlined.jpg|Streamlined features These were created by the erosion of running water that flowed from the bottom of the image to the top. This direction can be determined by the way the erosion tails are pointed. The location is the Amenthes quadrangle

</gallery>

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel
These forms were shaped by running water.

==Inverted Terrain==

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Possible inverted streams, as seen by HiRISE under HiWish program]]

Often low areas can become high areas. This frequently happens with streams. An old stream channel may become filled with a hard, erosion resistant material like lava or large boulders. Later, erosion of the whole area may remove all the surrounding soft materials. But, the stream channel will be preserved because of the hard materials that were deposited in it. In the end, you are left with a feature which is elevated above the landscape, but has the shape of the original stream. Geologists will then call the stream “inverted.”

<gallery class="center" widths="380px" heights="360px">

Image:ESP_024997ridges.jpg|Possible inverted stream channels, as seen by HiRISE under HiWish program. The ridges were probably once stream valleys that have become full of sediment and cemented. So, they became hardened against erosion which removed surrounding material.

ESP 036362 2195inverted.jpg|Inverted stream channels on crater slope, as seen by HiRISE under HiWish program Location is [[Diacria quadrangle]].
</gallery>

[[File:ESP 055431 1430invertedstream.jpg|thumb|400px|center|Inverted Stream channel It was once a stream, now it is a curved ridge.]]

==Exhumed Craters==

[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]

Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."

Exhumed terrain appears to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> <ref> https://www.uahirise.org/PSP_001374_1805</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under and around it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

[[File:57652 2215exhumed.marspedaijpg.jpg|thumb|400px|left|This crater had been buried and now is being uncovered by erosion. Had it just been formed, it would have destroyed part of the layered formation that is on top of its right side (just to the left of the crater).]]

[[File:48057 1560craterlayersclose.jpg|thumb|400px|center|The small crater that sits in layers is being exhumed. If it had been made after the layers that it is sitting in, it would have destroyed some of the layered material.]]

==Pedestal Craters==

[[File:ESP 037528 2350pedestal.jpg |Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.

A Pedestal crater is a crater with its ejecta sitting above the surrounding terrain. Its ejecta form a raised platform (like a pedestal).<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> They are produced when an impact ejects material that forms an erosion-resistant layer. Consequently, the immediate area erodes more slowly than the rest of the region. Some pedestals are hundreds of meters above the surroundings. This means that hundreds of meters of material were eroded away. What remains is a crater and its ejecta blanket sitting above the surrounding ground. <ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 048021 2130pedestal2.jpg|Pedestal Crater with an odd ejecta pattern

Image: ESP 047615 1275pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program Top layer has protected the lower material from being eroded. Location is Hellas quadrangle, at 52.014° S and 110.651° E (249.349 W).

File:62242 2265pedestal.jpg|Pedestal crater
</gallery>

==Ridges==

[[File:36745 1905ridgesv2.jpg |Close view of ridges We are sure how these were formed, but we have come up with a few possibilities.]]

Close view of ridges We are sure how these were formed, but we have come up with a few possibilities.

Ridge fields are another feature that we do not yet fully understand.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref> <ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>
Hard ridges standing above the surroundings often meet at close to right angles. They may have something to do with cracks caused by impacts. Mineral laden water may then migrate up the cracks and harden. These fields can be quite complex and beautiful.

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.

File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

</gallery>

[[File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle ]]

Ridge network in Amazonis quadrangle

==Layers==

[[File:44507 1880longlayersdanielson.jpg|600pxr|Layers in Dannielson Crater, as seen by HiRISE under HiWish program]]

Layers of rocks and other materials are very common on Mars.<ref>https://www.uahirise.org/PSP_007820_1505 Layered Sediments in Hellas Planitia</ref> They are found in many low places like craters.<ref>https://www.uahirise.org/hipod/PSP_008930_1880</ref> The widespread occurrence of layering on the Red Planet has great significance. On Earth, much layering originates in bodies of water.<ref>Namowitz, S., Stone, D. 1975. Earth science The World We Live in. American Book Company. N.Y. </ref> If this is true, at least to some extent on Mars, then traces of past life might be found in layered formations. Indeed, much evidence has been gathered for the existence of lakes in craters and some canyons.
Whether layers were created under water or through ground water, water is still being debated. Probably ground water is at least partial responsible for many of the layers we observe on the planet. The existence of water in the ground is important for life on Mars. Most of the organic mass on the Earth is found under the surface. Likewise, Mars may have a great deal of life living under the surface. <ref>https://microbewiki.kenyon.edu/index.php/Deep_subsurface_microbes</ref> <ref>Amend, J.. A. Teske. 2005. Expanding frontiers in deep subsurface microbiology. Palaeogeography, Palaeoclimatology, Palaeoecology: Volume 219, Issues 1–2, 131-155.</ref> Many microbes live deep underground.<ref>Pedersen, K. 1993. The deep subterranean biosphere. Earth Science Reviews: 34, 243-260.</ref> <ref> Stevens, T., J. McKiney. 1995. Lithoautotrophic Microbial Ecosystems in Deep Basalt Acquifers. Science: 270, 450-454.</ref> <ref>Fredrickson, J. , T. Onstott. 1996. Microbes Deep inside the Earth. Scientific American. October, 1996.</ref> Life under the Martian surface might find it easier since it would be protected from high levels of radiation.<ref>Boston, P., et al. 1992. On the Possibility of Chemosynthetic Ecosystems in Subsurface Habitats on Mars. Icarus: 95, 300-308.</ref> One recent study found that radiation from certain elements in the crust of Mars could have reacted with water in the ground to produce hydrogen. Hydrogen can supply chemical energy for life.<ref>http://astrobiology.com/2018/09/ancient-mars-had-right-conditions-for-underground-life.html</ref> <ref> Tarnas, J., et al. 2018 Radiolytic H2 Production on Noachian Mars: Implications for Habitability and Atmospheric Warming. Earth and Planetary Science Letters [https://doi.org/10.1016/j.epsl.2018.09.001</ref>

<gallery class="center" widths="380px" heights="360px">

File: 54763_1500layers2.jpg
File: 54763_1500layerscolor.jpg

File:59619 1845layers3.jpg|Close view of layers

File:59619 1845layers2labeled.jpg|Layers Different colors of the rocks means they contain different minerals.

ESP 048980 1725layers.jpg|Wide view of layers in Louros Valles, as seen by HiRISE under HiWish program Louros Valles is part of the Ius Chasma.
48980 1725layersclose2.jpg|Close view of layers in Louros Valles Note this is an enlargement of a previous image.

48980 1725layersclose.jpg|Close view of layers in Louros VallesNote this is an enlargement of a previous image.
ESP 048980 1725layersclosecolor.jpg|Close view of layers in Louros Valles Note this is an enlargement of a previous image.

File: 47421 1890bigbutte.jpg|Close view of layers, as seen by HiRISE under HiWish program. Box shows the size of a football field.
</gallery>

[[File:544858 1885topcloselayers5.jpg|thumb|400px|center|Close view of layers, as seen by HiRISE under HiWish program Location is Danielson Crater.]]

==Ribbed terrain==

Ribbed terrain consists of mostly elongated canyon-like forms. Some portions turn into mesas. It is created when small cracks become larger and larger. A crack in the surface of an ice-rich area will permit more of the ice to go into the thin Martian air because of increased surface area. This process of going directly form a solid to a gas phase is called sublimation. On Earth it is easily observed in the behavior of dry ice (solid carbon dioxide).

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows

[[File:28339 2245ribbbed.jpg|thumb|400px|center|Wide view of ribbed terrain.]]

[[File:ESP 025174 2245ribs.jpg|500pxr|Wide view of ribbed terrain.]]

Wide view of ribbed terrain.

[[File:25174 2245ribscolor.jpg|thumb|400px|center|Close, color view of ribbed terrain.]]

==Blocks and boulders forming==

Some places on Mars show rocks breaking into boulders or cube-shaped blocks.

[[File:26557joints.jpg|500pxr|Crossing joints, as seen by HiRISE under HiWish program]]

Crossing joints, as seen by HiRISE under HiWish program
<gallery class="center" widths="380px" heights="360px">
48144 1475layerscubes.jpg|Close view of layers, as seen by HiRISE under HiWish program Some of the layers are breaking up into large blocks
48144 1475cubes.jpg|Close view of layers Some layers are breaking up
</gallery>

[[File:26557rocksforming.jpg|Rocks forming|thumb|300px|left|Rocks forming]]

[[File:44757 2185fracturesblocks.jpg|thumb|300px|center|Blocks forming]]

[[File: 47577 1515blocks.jpg|thumb|400px|right|Surface breaking up into cube-shaped blocks]]

[[File: 46684 1280breaking.jpg|thumb|500px|center|Layers breaking up into boulders in Galle Crater, as seen by HiRISE under HiWish program]]

[[File:45377 2170blocks2.jpg|500pxr|Fractures forming large blocks Box shows size of a football field]]

Fractures forming large blocks Box shows size of a football field

==Volcanoes under ice==

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

Researchers believe they have found evidence that volcanoes erupt under ice on Mars.<ref>https://www.uahirise.org/ESP_071541_2200</ref> Such eruptions have been observed on the Earth. What seems to happen is that ice melts, the water escapes, and then the surface cracks and collapses. The resulting formation shows concentric fractures and large pieces of ground that seemed to have been pulled apart.<ref>Smellie, J., B. Edwards. 2016. Glaciovolcanism on Earth and Mars. Cambridge University Press.</ref> Sites like this may have recently had held liquid water; therefore, they may be good places to search for evidence of life.<ref name="Levy, J. 2017">Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185-194.</ref><ref>University of Texas at Austin. "A funnel on Mars could be a place to look for life." ScienceDaily. ScienceDaily, 10 November 2016. <www.sciencedaily.com/releases/2016/11/161110125408.htm>.</ref>

[[File:25755 2200collapse.jpg|thumb|400px|left|Close view of fractures from volcano under ice.]]

[[File:25755 2200tiltedlayers.jpg|thumb|400px|center|Close view of fractures from volcano under ice.]]

==Recurrent slope lineae==

Recurrent slope lineae are small, narrow, dark streaks on slopes that get longer in warm seasons. They may be evidence of liquid water.<ref>McEwen, A., et al. 2014. Recurring slope lineae in equatorial regions of Mars. Nature Geoscience 7, 53-58. doi:10.1038/ngeo2014</ref> <ref>McEwen, A., et al. 2011. Seasonal Flows on Warm Martian Slopes. Science. 05 Aug 2011. 333, 6043,740-743. DOI: 10.1126/science.1204816</ref> <ref>http://redplanet.asu.edu/?tag=recurring-slope-lineae|title=recurring slope lineae - Red Planet Report|website=redplanet.asu.edu|</ref> Evidence is still being gathered on this feature.

[[File:49955 1665rslcolorarrows (1).jpg|500pxr|Recurrent slope lineae (RSL) They form in warm seasons.]]

Recurrent slope lineae (RSL) They form in warm seasons.

==Notes about pictures==

Most pictures from spacecraft are enhanced. The surface of Mars shows little contrast. Consequently, in order to see more detail, contrast is enhanced by a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. This process makes a huge difference for some features like dark slope streaks. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red. Displaying colors in this way allows us to better identify rocks and minerals. Usually, color images are constructed in one of two ways. An IRB image assigns the output from the infrared channel to the color red, the wide red channel to the color green, and the blue-green channel to the color blue. On the other hand, a RGB image has the output of the broad red channel displayed as red, the blue-green channel as green, and a synthetic blue channel (blue-green minus part of the red) as blue. The wavelengths of these channels are: RED: 570-830 nanometers BG: <580 nanometers IR: >790 nanometers. One nanometer is equal to one billionth of a meter (0.000 000 001 m). HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.[12]

HiRISE images are about 5 km wide, but only have a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

==How to suggest image==

To suggest a location for HiRISE to image visit the site at http://www.uahirise.org/hiwish

In the sign up process you will need to come up with an ID and a password. When you choose a target to be imaged, you have to pick and exact location on a map and write about why the image should be taken. If your suggestion is accepted, it may take 3 months or more to see your image. You will be sent an email telling you about your images. The emails usually arrive on the first Wednesday of the month in the late afternoon.

==Notes to teachers==

This article goes along with the video Features of Mars with HiRISE under HiWish program at https://www.youtube.com/watch?v=b7q1Xyz_LBc

==References==
{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.jpl.nasa.gov/missions/viking-1/ OP Lunch Talk #10: HiWish, public suggestion targeting web tool for Mars imaging with MRO/HIRISE]

*[https://www.youtube.com/watch?v=0fQHEay-Yas&list=PLn0lnGc1Saik-yyWpeec3AWz9NgdtxDAF&index=122 How to Explore Mars without Leaving Your Chair - Jim Secosky - 23rd Annual Mars Society Convention]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]
*[[Viking 2]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

HiWish program

2023-03-04T22:48:36Z

Suitupandshowup: /* Pingos */

HiWish is a NASA program in which anyone can suggest a place for the [[High Resolution Imaging Science Experiment (HiRISE)]] camera on the [[Mars Reconnaissance Orbiter]] to image.<ref>http://www.marsdaily.com/reports/Public_Invited_To_Pick_Pixels_On_Mars_999.html |title=Public Invited To Pick Pixels On Mars |date=January 22, 2010 |publisher=Mars Daily</ref> <ref>http://www.astronomy.com/magazine/2018/08/take-control-of-a-mars-orbiter</ref> <ref>http://www.planetary.org/blogs/guest-blogs/hiwishing-for-3d-mars-images-1.html</ref> It started in January 2010. Three thousand people signed up in the first few months of the program.<ref>Interview with Alfred McEwen on Planetary Radio, 3/15/2010</ref> <ref>http://www.planetary.org/multimedia/planetary-radio/show/2010/384.html|title=Your Personal Photoshoot on Mars?|website=www.planetary.org|</ref> By February 2020, 9,726 had signed up and 24,059 suggestions had been submitted for targets in each of the 30 quadrangles of Mars. A that point 10,318 images had been taken.<ref> https://www.jpl.nasa.gov/missions/viking-1/</ref> <ref> OP Lunch Talk #10: HiWish, public suggestion targeting web tool for Mars imaging with MRO/HIRISE</ref> The first images were released in April 2010.<ref>http://topnews.net.nz/content/23052-nasa-releases-first-eight-hiwish-selections-people-s-choice-mars-images |title=NASA releases first eight "HiWish" selections of people's choice Mars images |date=April 2, 2010 |publisher=TopNews |accessdate=January 10, 2011 |archive-url=https://www.webcitation.org/6Gop7RR0c?url=http://topnews.net.nz/content/23052-nasa-releases-first-eight-hiwish-selections-people-s-choice-mars-images |</ref> Some of the images from HiWish were used for three talks at the 16th Annual International Mars Society Convention. Below are some of the over 4,224 images that have been released from the HiWish program as of March 2016.<ref>McEwen, A. et al. 2016. THE FIRST DECADE OF HIRISE AT MARS. 47th Lunar and Planetary Science Conference (2016) 1372.pdf</ref>

==Landslides==

[[File:ESP 057191 2150landslidecropped.jpg|Landslide]]

Landslides have been observed on Mars. They may be a little different since the gravity of Mars is only about one third as that of the Earth.
<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 1585landslide.jpg|Landslide
File:ESP 043963 1550landslide.jpg|Landslide
</gallery>

==Hollows==

[[File:28207 2250hollowsarrows.jpg|Hollows]]

Hollows make strange, beautiful landscapes. The hollows are believed to be produced when ice leaves the ground and the remaining dust is blown away. There is much water frozen in the ground. Water is carried around the planet frozen on dust grains that fall to the ground and make up what is called “mantle.” Mantle is produced when the climate is such that there is a lot of dust and moisture in the atmosphere. During those times, water will freeze onto the dust particles. Eventually, the particles will be too heavy and fall to the surface. In addition, it may snow on Mars.
The mantle covers wide expanses. It has a smooth appearance. It covers the irregular, created surface of the planet.

<gallery class="center" widths="380px" heights="360px">

File:46325 2225hollows4.jpg|Hollows

File:ESP 046325 2225hollowsmiddlelabeled.jpg|Hollows

</gallery>

==Mud Volcanoes==

[[File:53381 2265mud.jpg|Mud volcanoes]]

Mud volcanoes They may have come through a zone of weakness in the rock here

Mud volcanoes are very common in a place on Mars called the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold evidence of life.<ref>Wheatley, D., et al., 2019. Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization. Icarus. In Press</ref> Mud that formed the volcanoes comes from a depth underground that is deep enough to be protected from radiation. The radiation level at the surface would kill most organisms over time. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>

<gallery class="center" widths="380px" heights="360px">
File:570770 2100coneslabeled.jpg|Mud volcanoes

File:52050 2200mudvolcanoes.jpg|Mud volcanoes
File:ESP 043580 2120mud.jpg|Wide view of field of mud volcanoes
</gallery>

==Volcanic vents==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

[[File:ESP 030440 1945ventcropped.jpg|Volcanic vent]]

Volcanic vent

==Lava Flows==

[[File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons]]

Lava flow on Olympus Mons

Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W. 2007. The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G. 2008. Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref> Large volcanoes in the [[Tharsis]] region show many overlapping lava flows. Lava flows can also move around and create what appear to be layers, especially if it behaves like water. Basalt flows are very fluid.<ref>https://www.uahirise.org/ESP_057978_1875</ref>

<gallery class="center" widths="380px" heights="360px">
File:44828 2030lavaflow.jpg|Lava flows These are common in large sections of Mars.

File:ESP 044840 1620lavaflow.jpg|Lava flow

File:WikiESP 035095 1975lavalobestharsiswide.jpg|Old and young lava flows

File:68460 1945laveolympus.jpg|Lava flowing down a slope from [[Olympus Mons]]

File:68460 1945lavechannel.jpg|Lava channel from Olympus Mons

</gallery>

==Rootless Cones==

[[File:40162 2065conesarrows2.jpg|Rootless cones ]]

Rootless cones

Rootless Cones are thought to be caused by lava flowing over ice or ground containing ice. Heat from the lava causes the ice to quickly change to steam. The resulting steam explosion produces a ring or cone. Such features are common in certain locations on the Earth. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form. Sometimes a wake is made as the lava moves along the surface.

<gallery class="center" widths="380px" heights="360px">

File:45384 2065cones2.jpg|Rootless cones
File:45384 2065cones.jpg|Rootless cones Here, lava has moved over ice-rich ground from the upper right to the lower left of the picture.
File:58610 2100coneswakeslabeled.jpg|Close view of wake of a rootless cone
File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones

</gallery>

==Dikes==

[[File:ESP 045981 2100dike2.jpg|Dike]]

Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

Dikes show as mostly straight ridges. They are made when magma flows along cracks or faults in the ground. This part of the process happens under the ground. Later erosion will remove the weaker materials around the dike. What is left is a narrow wall of rock.<ref> "Characteristics and Origin of Giant Radiating Dyke Swarms". MantlePlumes.org.</ref> On Mars many faults are due to stretching of the crust. The mass of huge volcanoes pull at the crust until it cracks.

[[File:ESP 046403 2095dikecropped.jpg|thumb|400px|center|Dike in [[Syrtis Major quadrangle]]]]

==Troughs==

[[File:ESP 051781 2035troughs.jpg |Troughs]]

Troughs are common on Mars. They are due to the great weight of several huge volcanoes on Mars. The mass of these structures has caused the crust to stretch. That tension made the crust break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>

<gallery class="center" widths="380px" heights="360px">

File:56910 2100trough.jpg|Group of troughs

File:Troughs in Elysium Planitia.jpg|Troughs showing layers Hard cap rock is at the surface. The center section is in color. With HiRISE only a strip in the middle is in color.

File:ESP 057834 2005troughmesa.jpg|Troughs cutting through mesa, as seen by HiRISE under HiWish program
</gallery>

==Faults==

Faults are visible in some parts of Mars. They are most noticeable in places where many layers exist. Sometimes their presence is known because they can change the direction of stream channels.

[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]

Layers and fault in Firsoff Crater

[[File:60331 1880faultslabeled2.jpg|thumb|300px|left|Faults in layered terrain]]

[[File:27615 1880faults.jpg|thumb|300px|center|Faults in layered terrain]]

[[File:71634 1880layersfaultslabeled.jpg|thumb|300px|Faults in layers in Danielson Crater]]

<gallery class="center" widths="380px" heights="360px">
File:26086 1800fault.jpg|Fault that changed direction of stream. CTX image is included for context.

</gallery>

==Mesas and layers==

[[File:58788 1890layerscolorlabeled2.jpg|Mesa with layers]]

Mesa with layers

On Mars much layered terrain is visible. Layered rock is formed from separate events. For example, a layer may be formed at the bottom of a lake. Later, lava may cover that layer, thus making a new layer—one that is harder. In times erosion may remove nearly all the layers. But, sometimes remnants are left behind, especially if they are topped off by a hard cap rock. Lave flows can make cap rock. The cap rock will protect the underlying rocks from erosion. Cap rock often breaks up into large boulders. Sometimes the boulders are in the shape of cube-shaped blocks. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area. Mesas are what are left after the ground is mostly eroded.

<gallery class="center" widths="380px" heights="360px">
File:58563 2225mesa.jpg|Mesa

File:58524 1820layerscolor4labeled.jpg|Mesa with layers

File:58919 1935mesalayers.jpg|Mesa with layers Box is the size of a football field.

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte The box shows the size of a football field.

</gallery>

==Layers in Craters==

[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

Craters can contain mesas that show layers. It is believed that these layers are the remnants of material that once covered a wide area, but is now only in protected places like inside craters. The layers mean that different events laid down the layers. These layers are probably due to latitude dependent mantle that falls from the sky at different times. Mantle is mostly from ice-coated dust falling from the sky under certain climate conditions. Wind, acting over millions of years, will shape the material in craters into smooth mesas.

<gallery class="center" widths="380px" heights="360px">

File:48024 2195pyramid.jpg|Layered mound in crater Layers represent material that once covered a wide area. Mound was shaped by winds.<ref>https://www.uahirise.org/hipod/ESP_054486_2210</ref>

File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle These layered features are quite common in some regions of Mars.

File:28207 2250cratermesa.jpg|Color view of layers in a mesa in a crater
</gallery>

==Dipping Layers==

[[File:46180 2225dippinglayers.jpg|Dipping layers and brain terrain (right side of picture)]]

Dipping layers and brain terrain (right side of picture)

A common feature on Mars is “dipping layers.” They are groups or stacks of layers that seem to be leaning against something steep like a crater wall or the wall of a mesa. It is believed that they represent material that once covered a wide area, but is now only in protected places. The layers mean that different events laid down the layers. These layers are probably due to latitude dependent mantle that falls from the sky at different times. Mantle is mostly from ice-coated dust falling from the sky under certain climate conditions. These dipping layers are often smooth from the action of the wind over millions of years.

[[File:ESP 038002 1375dipping.jpg|thumb|300px|left|Wide view of dipping layers against slopes]]

[[File:ESP 062082 2175dippingcropped.jpg|thumb|300px|right|Dipping layers These may be the remains of past layers of mantle that covered the whole area.]]

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210pyramidsismenius.jpg|Dipping layers against a mesa wall.

</gallery>

[[File:ESP 019778 1385pyramid.jpg|Set of dipping layers in crater]]

Set of dipping layers in crater

==Boulders==

[[File:28497 2250boulderslabeled.jpg|Boulders near hollows]]

Boulders near hollows

Large, house-sized boulders are widespread on the Red Planet. Mars has an old surface—billions of years old. In that time, erosion has broken down many hard rocks. Most of Mars is covered with hard volcanic rock. The dark volcanic rock basalt covers most of the Martian surface. When it breaks, it first forms large boulders.

<gallery class="center" widths="380px" heights="360px">

File:55119 2080mesasinglelabeled.jpg|Mesa The top has a hard cap rock that protects the underlying rocks from erosion. Boulders are visible in the image.
File:58904 2240brainsboulders.jpg|Boulders and brain terrain
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas Box shows size of football field.
49950 2125ridgesboulders.jpg|Close view of ridge networks, as seen by HiRISE under HiWish program Many boulders are visible.

File:ESP 045415 2220boulders.jpg|Color view of boulders

45575 2535dunebouldertracks.jpg|Boulders and tracks, as seen by HiRISE under HiWish program The arrows show a boulders that have produced a track by rolling down dune.

</gallery>

[[File: 47157 1850boulders.jpg|Boulders and their tracks from rolling down a slope Arrows show two boulders at the end of their tracks.]]

Boulders and their tracks from rolling down a slope Arrows show two boulders at the end of their tracks.

[[File:59458 2145boulders.jpg|Color view of boulders]]

Boulders formed from break up of a mesa

==Yardangs==

[[File:61167 1735yardangs.jpg|Yardangs]]

Yardangs

Yardangs develop from fine-grained material. They are shaped by the wind and show the direction of the dominant winds.<ref> Bridges, Nathan T.; Muhs, Daniel R. (2012). "Duststones on Mars: Source, Transport, Deposition, and Erosion". Sedimentary Geology of Mars. pp. 169–182. doi:10.2110/pec.12.102.0169. ISBN 978-1-56576-312-8.</ref> <ref> https://www.uahirise.org/ESP_039563_1730</ref> Volcanoes supply much of this fine-grained material. Yardangs are especially widespread in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref> Because yardangs exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref> The largest single source of dust in the air on Mars comes from the Medusae Fossae Formation.<ref> Ojha, Lujendra; Lewis, Kevin; Karunatillake, Suniti; Schmidt, Mariek (2018). "The Medusae Fossae Formation as the single largest source of dust on Mars". Nature Communications. 9 (1): 2867.</ref>

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
File:ESP 047915 1815yardangs.jpg|Wide view of yardangs
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs
</gallery>

==Ring-Mold Craters==

[[File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.]]

Ring mold craters They may contain ice.

Ring-mold craters are a type of small impact crater that looks like the ring molds used in baking.<ref>https://link.springer.com/referenceworkentry/10.1007/978-1-4614-9213-9_318-1</ref> <ref>kress, A., J. Head. 2008. Ring‐mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophysical Research Letters Volume 35, Issue 23</ref> One popular idea for their formation is an impact into ice--Ice that is covered by a layer of debris.<ref>https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008GL035501</ref> They are found in parts of Mars that contain buried ice. Laboratory experiments confirm that impacts into ice end in a "ring mold shape." Other evidence for this contention is that they are bigger than other craters in which an asteroid impacted solid rock implying that the material entered by the impact was softer than rock (as ice is). Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill—both thought to have buried ice under a thin layer of rocky debris<ref>Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8</ref> <ref>Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209</ref> <ref>Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379</ref> Ring-mold craters may be an easy way for future colonists of Mars to find water ice because some may contain ice that is relatively pure. And, since it was generated during a rebound, ice may have been brought up from below the surface; hence, less digging or drilling may be required to gather ice.

<gallery class="center" widths="380px" heights="360px">

26055ringmoldcrater.jpg|Close view of ring mold crater.
File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
</gallery>

==Dark Slope Streaks==

[[File:55480 2060streaksobstacles.jpg|Some of the streaks here were affected by boulders.]]

Streaks around a mound. Some of the streaks here were affected by boulders.

[[File:55107 1930streaksboulders2.jpg|thumb|300px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

[[Dark slope streaks]] are avalanche-like features common on dust-covered slopes.<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. 2010. Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> These streaks have never been observed on the Earth.<ref>Heyer, T., et al. 2019. Seasonal formation rates of martian slope streaks. Icarus </ref>
They form in relatively steep terrain, such as along cliffs and crater walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S. 2002. Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref> Although they appear much darker than their surroundings, the darkest streaks are only about 10% darker than their backgrounds. Streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046188 1855streakslabeled2.jpg|Streaks along a mesa
File:ESP 045435 2055troughlayers.jpg|Dark slope streaks in a trough

</gallery>

[[File:23677streakslabeled.jpg|Streaks often start at a small point and then expand down slope.]]

Streaks often start at a small point and then expand down slope. Many streaks may be caused by the action of solid carbon dioxide (dry ice). Under conditions on Mars, during the night dry ice forms under the surface. When the ground warms in the morning, the dry ice turns into a gas and creates a wind that disturbs the dust grains. If situated on a steep slope, an avalanche of bright dust moves down and uncovers the dark undersurface.<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al. 2022. Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks. JGR Planets. Volume127, Issue4. e2021JE006988</ref>

==Dust Devil Tracks==

Dust devil tracks can be very beautiful. They are made by giant [[dust devils]] removing bright colored dust from the Martian surface. As a result, dark underlying material is exposed.<ref>https://www.uahirise.org/ESP_058427_1080</ref> Dust devils on Mars have been photographed both from the ground and from orbit.<ref>https://www.uahirise.org/ESP_042201_1715</ref> They helped scientists by blowing dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> Dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref> The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">

File:ESP 036297 2370devils.jpg|Dust Devil Tracks

File:ESP 036631 2335devilsbottom.jpg|Dust devil tracks in Casius quadrangle

</gallery>

[[File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.|500pxr|Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.]]

Dust devil tracks in Casius quadrangle

==Dunes==

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Some places on Mars have many beautiful dark dunes. Rovers on the Martian surface confirmed earlier ideas that the dunes are composed of sand made from the volcanic rock basalt..<ref>Lorenz, R. and J. Zimbelman. 2014. Dune Worlds How Windblown Sand Shapes Planetary Landscapes. Springer. NY.</ref> Dunes are often covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring. As the frost disappears, different patterns can emerge on the dunes. Dunes can take on different colors because of slight chemical variations in the sand grains.

The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars. However, we must remember that its atmosphere is only about 1 % as dense as the Earth's. Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).<ref> https://www.space.com/30663-the-martian-dust-storms-a-breeze.html</ref>

[[File:ESP 046378 1415dunescolor.jpg|thumb|300px|right|Dunes]]

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:59628 1275dunes.jpg|Dunes in Hellas quadrangle

</gallery>

[[File:58089 2170duneswidemarsp.jpg |600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle|Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle]]

Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle

[[File:59658 1415dunes.jpg|600pxr|Dunes The location is the Noachis quadrangle |Dunes The location is the Noachis quadrangle]]

Dunes The location is the Noachis quadrangle

[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes This image was named picture of the day for July 25, 2021]]

Dunes This image was named picture of the day for July 25, 2021

==Glaciers==

[[File:ESP 018857 2225alpineglacier.jpg|Glacier moving out of a valley This is similar to glaciers on the Earth]]

Glacier moving out of a valley This is similar to glaciers on the Earth

Glaciers have been described as “rivers of ice.” With glaciers there is a downward movement that can be noticed by examining patterns on their surface. There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. Exposed ice will not last long under present climate conditions on Mars, but just a few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref> Researchers noticed decades ago that many forms on Mars resembled glaciers on the Earth. As scientists received pictures with greater resolution, the shapes and patterns visible on their surfaces looked like the flows visible in the Earth’s glaciers.

<gallery class="center" widths="380px" heights="360px">

File:ESP 050176 2245glacier.jpg|Glacier moving out of a valley
File:ESP 045085 2205flowlabeled.jpg|Alpine Glacier moving out of a valley and then moving onto Lineated valley fill (LVF) The LVF contains ice under a layer of insulating debris. Lineated Valley Fill is considered to be a glacier.
File:47193 1440glacier.jpg|Glaciers
File:35934 2215brainsglacier.jpg|End of an old glacier. Most of the ice is gone, but the material moved by the glacier is formed into an arc.
</gallery>

<gallery class="center" widths="380px" heights="360px">
ESP 045505 1400flow.jpg|Flow feature that was probably a glacier

Image:ESP_020319flowcontext.jpg|Context for the next image of the end of a glacier.

Image:ESP_020319flowsclose-up.jpg|Close-up of the area in the box in the previous image. This may be called by some the terminal moraine of a glacier. For scale, the box shows the approximate size of a football field.

Image:Tongue23141.jpg|Tongue-shaped glacier, Ice may exist in the glacier, even today, beneath an insulating layer of dirt.

Image:Tongue23141close.jpg|Close-up of tongue-shaped glacier Resolution is about 1 meter, so one can see objects a few meters across in this image.

</gallery>

==Lobate Debris Aprons (LDA’s) ==

Lobate debris aprons (LDAs), first seen by the Viking Orbiters, look like piles of rock debris below cliffs.<ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. </ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> They slope away from mesas and buttes.
The Mars Reconnaissance Orbiter's Shallow Radar found pure ice in LDA’s around many mesas.<ref>http://www.planetary.brown.edu/pdfs/3733.pdf</ref> Based on this data, LDA’s are considered to be glaciers covered with a thin layer of rocks.<ref>Head, J. et al. 2005. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars. Nature: 434. 346-350</ref><ref>http://www.marstoday.com/news/viewpr.html?pid=18050</ref> <ref>http://news.brown.edu/pressreleases/2008/04/martian-glaciers</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>Holt, J. et al. 2008. Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2441.pdf</ref> <ref>Petersen, E., et al. 2018. ALL OUR APRONS ARE ICY: NO EVIDENCE FOR DEBRIS-RICH “LOBATE DEBRIS APRONS” IN DEUTERONILUS MENSAE 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2354.</ref>

[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 036580 2260ldacropped.jpg|Lobate debris apron
File:ESP 036619 2275ldacropped.jpg|Lobate debris apron
</gallery>

==Lineated Valley Fill (LVF) ==

Lineated valley floor consists of many mostly parallel ridges and grooves on the floors of many channels. The ridges and grooves look like they moved around obstacles. They are believed to be ice-rich. Some glaciers on the Earth show such features.<ref> https://www.uahirise.org/ESP_026414_2205</ref>
[[File:ESP 052138 1435lvf.jpg|600pxr|Image of gullies with main parts labeled. The main parts of a Martian gully are alcove, channel, and apron. Since there are no craters on this gully, it is thought to be rather young. Picture was taken by HiRISE under HiWish program.]]

[[File:ESP 046061 2190lvf.jpg|thumb|300px|right|Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)]]
[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of Lineated Valley Fill (LVF)]]

<gallery class="center" widths="380px" heights="360px">
File:ESP 055408 1375lvf2.jpg|Lineated Valley Fill
File:ESP 046840 2130lvf.jpg|Lineated Valley Fill in valley
File:53630 2195lvf.jpg|Lineated Valley Fill
File:56544 2200lvfbrains.jpg|Lineated Valley Fill
File:56544 2200lvflabeled.jpg|Lineated Valley Fill
</gallery>

==Concentric Crater Fill (CCF) ==

[[Image: ESP_046622_1365ccf.jpg |Concentric Crater Fill Lat: 43.1° S Long: 219.8°E (140.2 W]]

Concentric Crater Fill Located at Lat: 43.1° S Long: 219.8°E (140.2 W

Concentric crater fill is believed to be an ice-rich feature on the floors of many Martian craters. The floor of craters exhibiting CCF is almost totally covered with many parallel ridges.<ref>https://web.archive.org/web/20161001224229/http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185 </ref> It is common in the mid-latitudes of Mars,<ref>Dickson, J. et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> and is widely accepted as caused by glacial movement.<ref>Head, J. et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for late Amazonian obliquity-driven climate change. Earth Planet. Sci Lett: 241. 663-671.</ref> <ref>Levy, J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res.: 112.</ref> The [[Ismenius Lacus quadrangle]] contains examples of concentric crater fill.

<gallery class="center" widths="380px" heights="360px">
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill

File:46688 1365ccf2.jpg|Close view of Concentric Crater Fill (CCF)
</gallery>

==Brain Terrain==

[[File:45917 2220brainsopenclosed.jpg|Open and closed brain terrain]]

Open and closed brain terrain The closed cell brain terrain may still hold an ice core, so they may be sources of water for future colonists.<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>

Brain terrain is an area of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists. There are two kinds—open and closed. Brain terrain is thought to begin with cracks that get larger and larger as ice leaves the ground. When ice is exposed on Mars under its present climate conditions, ice goes directly into the air. That process of going from a solid to a gas—instead of first to a liquid—is called sublimation. With this process, the cracks get wider and wider until a complex of high and low areas remains. <ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

<gallery class="center" widths="380px" heights="360px">
File:25246brainseroding.jpg|Brain terrain
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle The closed cell brain terrain may still hold an ice core,<ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> so it may a source of water for future colonists.
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle

File:53630 2195brainslvf.jpg|Brains on surface of leaneted valley fill
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
</gallery>

==Ice Cap Layers==

[[File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap This photo was named picture of the day for January 21, 2019. ]]

Layers in northern ice cap This photo was named picture of the day for January 21, 2019.

The northern ice cap of layers displays many layers. These layers are visible when a valley cuts through the cap. Layers in the ice cap, as with other exposures of layers across the planet, are formed from frequent dramatic changes in the climate. These changes are the result of great changes in the rotational axis or tilt of the planet. Mars does not have a large moon to stabilize its' tilt; hence the planet has huge variations in its tilt (maybe from its present Earth-like tilt to over twice the Earth’s).

<gallery class="center" widths="380px" heights="360px">

File:ESP 061636 2620nicecaplayerscroppedlabeled.jpg|Northern ice cap layers
File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle

File:ESP 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
ESP_052405_2595icelayers.jpg|Layers in northern ice cap Some of the layers are at different angles because erosion took away some layers to the right.

</gallery>

==Spiders==

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

Some features have been called spiders because they can resemble spiders. The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref> <ref>https://www.uahirise.org/</ref> This process results in the appearance of dark plumes that are often blown in one direction by local winds. Besides producing plumes, dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>
The process of making spiders was demonstrated in laboratory simulations involving slabs of dry ice and glass spheres of different sizes.<ref>https://www.nature.com/articles/s41598-021-82763-7.pdf</ref> <ref>McKeown, L., et al. 2021. The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric
pressure. Scientific Reports.</ref> <ref>https://www.livescience.com/spiders-on-mars-explained-dry-ice.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref>

<gallery class="center" widths="380px" heights="360px">

File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program

</gallery>

==Mantle==

[[File:37167 1445mantlelabeled.jpg|Mantle Mantle covers the surface irregularities on Mars]]

Mantle Mantle covers the surface irregularities on Mars

Mantle on Mars appears as a smooth surface. It covers the normal irregular surface of the planet. It is often called “Latitude Dependent Mantle” because it occurs at certain distances from the equator (certain latitudes).<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> This latitude dependent mantle is believed to fall from the sky. During certain climatic conditions, moisture from the air will freeze onto dust particles. When they become too heavy, these particles fall to the ground. Snow may also fall on to the mantle. So, mantle consists of ice with dust. Since Mantle has a widespread distribution, it may be a major source of water for future colonists. Sometimes mantle displays layers because it was deposited at different times. The climate of Mars has changed many times due to a lack of a large moon. Our Earth’s moon is very massive and that helps to control the tilt of the rotational axis of our Earth. In other words, our moon keeps our planet’s tilt from changing much. Changes in the tilt of a planet will cause major changes in climate.

<gallery class="center" widths="380px" heights="360px">

File:46294 1395mantle.jpg|Comparison of terrain with and without a covering of mantle
46444 2225mantle.jpg|Mantle, as seen by HiRISE under HiWish program
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program

</gallery>

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.

==Polygons==

[[File:56942 1075icepolygonslabeled2.jpg|Polygons]]

Polygons

Many surfaces on Mars have polygon shapes. These areas are sometimes called “polygonal patterned ground.” The polygons can be of different shapes and sizes—often very beautiful. They are believed to be caused by ice in the ground because they occur on the Earth where there is ice in the ground.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction.<ref>https://www.uahirise.org/ESP_066782_1110</ref> <ref>https://www.uahirise.org/ESP_047247_1150</ref>

In the future they may help point us to supplies of ice for colonists. The locations of polygons will provide evidence for us to make detailed maps for locations of water before we send crews to live there.

<gallery class="center" widths="380px" heights="360px">

File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons that shows polygons of varying sizes. Dark lines are defects in processing.
File:56148 1145polygons.jpg|Close view of polygons

File:ESP 043821 2555dryice.jpg|Field of dunes defrosting Black areas are free of frost, so the dark of the dunes shows up. White portions of dunes are still covered with frost.

File:ESP 043821 2555dryicecolor.jpg|Close view of parts of two dunes showing white parts with frost. The polygon surface they sit on still has frost in the low areas.

</gallery>

[[File:43821 2555dunesdefrosting2.jpg|Defrosting dune--white areas still contain frost]]

Defrosting dune--white areas still contain frost. Frost is in low parts of polygons.

==Scalloped Terrain==

[[File:37461 2255scallopslabeled2.jpg|Scalloped terrain This feature is important it may point future colonists to water supplies.]]

Scalloped terrain This feature is important it may point future colonists to water supplies.

Scalloped topography or terrain is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region called “Utopia Planitia.”<ref>last1 = Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 |</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref> This terrain displays shallow, rimless depressions with scalloped edges--commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>http://www.uahirise.org/ESP_038821_1235</ref> <ref>Dundas, C., et al. 2015. Modeling the development of martian sublimation thermokarst landforms. Icarus: 262, 154-169.</ref> Scalloped topography may be of great importance for future colonization of Mars because radar studies reveal it is ice-rich.<ref>"Dundas, C. 2015" Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Stuurman, C., et al. 2016. SHARAD reflectors in Utopia Planitia, SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars. Geophysical Research Letters, Volume 43, Issue 18, 28 September 2016, Pages 9484–9491.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia
File:37461 2255scallopedclose.jpg|Scalloped terrain
</gallery>

==Pingos==

[[File: ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)]]

Close view of possible pingo with scale, as seen by HiRISE under HiWish program Lat: 54.7° S Long: 202.7°E (157.3 W)

For many years, Pingos were believed to be present on Mars. Since they contain pure water ice, they would be a great source of water for future colonists on Mars. One picture from HiRISE under the HiWish program was thought to be a pingo.

File:76854 2220pingo.jpg

==Gullies==

[[File:50858 1435gullylabeled.jpg|Gullies with parts labeled--Alcove, Channel, Apron]]

Gullies with parts labeled--Alcove, Channel, Apron

[[Martian gullies]] are narrow channels and their associated downslope deposits. They are found on steep slopes. Most are seen on the walls of craters. Many are visible near 40 degrees north and south of the equator. Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref >Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters. For many years, gullies were thought to be caused by recent running water. But since some are being formed today, even when the climate of Mars is too cold for running water to exist on the surface, there must be another cause. After more observations, it was shown that pieces of dry ice moving down slopes could cause them. Nevertheless, some scientists think that in the past, water may have been involved in their formation.

<gallery class="center" widths="380px" heights="360px">
File:ESP 046386 1420gullies.jpg|Gullies

File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program Only part of the picture appears in color because the camera only produces color in a center strip.

</gallery>

[[File:Gullies near Newton Crater2185.jpg|Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>]]

Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>

==Craters==

[[File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.]]

This is a fairly young crater as it still shows ejecta, layers, and a rim.

Craters cover nearly all parts of Mars. Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. There are many kinds of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>

<gallery class="center" widths="380px" heights="360px">

File:55252 1385craterfloorbrains.jpg|Crater floor with brain terrain

File:ESP 055252 1385brainscolorclose.jpg|Edge of crater with brain terrain on its floor

File:52030 1560crater.jpg|Average crater showing layers

File:54774 1700colorcraterejecta.jpg|Crater and part of its ejecta

File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions The curved depressions are formed when the ground loses ice. Gullies may be due to water or dry ice moving down the walls.
File:ESP 048131 2055crater.jpg|Crater with pits and holes on floor The shapes on the floor occurred when ice left the ground.

File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape. this may have formed from a low angle impact.
File:ESP 053576 1990lightstreak.jpg|Crater with light streak Streaks associated with craters are quite common on Mars because there is a great deal of fine dust that can be blown around.

File:61167 1735crater.jpg|Crater with thin ejecta The color strip for HiRISE images is only in the center of images.

</gallery>

[[File:29565 2075newcratercomposite.jpg|New, small crater We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet.]]

New, small crater We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref> <ref>https://www.sciencedirect.com/science/article/abs/pii/S0019103513001693?via%3Dihub</ref> <ref>Daubar, I., et al. 2013. The current martian cratering rate. Icarus. Volume 225. 506-516. </ref>

==Hellas Floor Features==

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.
The exact origin of these shapes is unknown at present.

The Hellas floor contains strange-looking features that look like some sort of abstract art. One such feature is called "banded terrain." <ref>Diot, X., et al. 2014. The geomorphology and morphometry of the banded terrain in Hellas basin, Mars. Planetary and Space Science: 101, 118-134.</ref> <ref>http://www.nasa.gov/mission_pages/MRO/multimedia/20070717-2.html | title=NASA - Banded Terrain in Hellas</ref> <ref>http://hirise.lpl.arizona.edu/ESP_016154_1420 | title=HiRISE | Complex Banded Terrain in Hellas Planitia (ESP_016154_1420)</ref> This terrain has also been called "taffy pull" terrain, and it lies near honeycomb terrain, another strange surface.<ref>Bernhardt, H., et al. 2018. THE BANDED TERRAIN ON THE HELLAS BASIN FLOOR, MARS: GRAVITY-DRIVEN FLOW NOT SUPPORTED BY NEW OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1143.pdf</ref> Banded terrain is found in the north-western part of the Hellas basin, the deepest section. The bands can be classified as linear, concentric, or lobate. Bands are typically 3–15km long and 3km wide. Narrow inter-band depressions are 65 m wide and 10 m deep.<ref>doi=10.1016/j.pss.2015.12.003 |title=Complex geomorphologic assemblage of terrains in association with the banded terrain in Hellas basin, Mars |journal=Planetary and Space Science |volume=121 |pages=36–52 |year=2016 |last1=Diot |first1=X. |last2=El-Maarry |first2=M.R. |last3=Schlunegger |first3=F. |last4=Norton |first4=K.P. |last5=Thomas |first5=N. |last6=Grindrod |first6=P.M. |last7=Chojnacki |first7=M. |121...36D |url=https://boris.unibe.ch/74530/1/Diot_Schlunegger.pdf </ref> How these shapes were made is still a mystery, although some explanations have been advanced.

[[File:55146 1425hellisfloorcropped.jpg|thumb|400px|center|Features on floor of Hellas impact basin.]]

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

<gallery class="center" widths="380px" heights="360px">
ESP 049330 1425honeycomb.jpg|Honeycomb terrain

File:ESP 057110 1365ridgescircles.jpg|Close view of concentric and parallel ridges, as seen by HiRISE under [[HiWish program]]

</gallery>

==Oxbow lakes and meanders==

An oxbow lake is a U-shaped lake that forms when a wide meander of a river is a cut off that makes a lake. This landform is so named for its distinctive curved shape, which resembles the bow pin of an oxbow.<ref>https://en.wikipedia.org/wiki/Oxbow_lake</ref> Finding them on Mars means that water probably flowed for a long time.

<gallery class="center" widths="380px" heights="360px">
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.

File:29054cutoff.jpg|Stream meander and cutoff, as seen by HiRISE under HiWish program. This is part of a major drainage system in the Idaeus Fossae region.
</gallery>

[[File: ESP 045779 1730meander.jpg|600pxr|Channel showing an old oxbow and a cutoff, as seen by HiRISE under HiWish program]]

Channel showing an old oxbow and a cutoff

[[File: ESP 045868 2245channel.jpg|600pxr|Channel, with meanders These meanders may have meandered a little more and then made oxbow lakes. Arrow points to a crater that was probably eroded by flowing water.]]
Channel, with meanders These meanders may have meandered a little more and then made oxbow lakes. Arrow points to a crater that was probably eroded by flowing water.

[[File:ESP 043623 2160meander.jpg|600pxr|Meanders Meanders are commonly formed in old river systems when the water is moving slowly.]]
Meanders They are formed in old river systems when the water is moving slowly.

[[File: ESP 052494 1395meanders.jpg|600pxr|Channel Arrows indicate evidence of a meander.]]

Channel Arrows indicate evidence of a meander.

==Channels==

[[File:ESP 056917 2170channels3.jpg|Old river channel with branches]]

Old river channel with branches and meanders

There are thousands of channels that were caused by running water in the past on Mars. Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref> These channels have been seen in pictures from spacecraft for nearly 50 years. Current climate models do not support a warm climate on Mars; consequently, various ideas have been advanced to explain the existence of so many channels when it may have always been too cold for liquid water to exist on the surface. Some say they could be formed under ice sheets. Other scientists maintain that they could be produced in short periods after an asteroid impact warms the planet for thousands of years.

<gallery class="center" widths="380px" heights="360px">
File:41974 1740channellabeled.jpg|Old river valley in the Sinus Sabaeus quadrangle

WikiESP 033729 1410stream.jpg|Small branched channel

File:13882282 10207143921535802 7740003704272946655 nchannelinvalley.jpg|Channel in valley The valley was formed early on and then at a later time a small channel appeared. This arrangement means that water flowed here twice--once for the valley, another time for the small channel.

</gallery>

==Streamlined Shapes==

[[File:ESP 045860 2085streamlinedcroppedlabeled.jpg|Streamlined shapes made by running water]]

Streamlined shapes made by running water

Some locations on Mars show clear evidence of massive flows of water in the past. During these floods, the ground was carved into streamlined shapes. There are several ideas for how all this happened.<ref>https://www.uahirise.org/ESP_045833_1845</ref> It may have resulted from asteroid impacts into frozen ground. Under a cap of frozen ground there may have been vast buildups of water that were suddenly released.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057728 2090streamlined.jpg|Streamlined forms

File:58137 2090streamlined.jpg|Streamlined features These were created by the erosion of running water that flowed from the bottom of the image to the top. This direction can be determined by the way the erosion tails are pointed. The location is the Amenthes quadrangle

</gallery>

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel
These forms were shaped by running water.

==Inverted Terrain==

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Possible inverted streams, as seen by HiRISE under HiWish program]]

Often low areas can become high areas. This frequently happens with streams. An old stream channel may become filled with a hard, erosion resistant material like lava or large boulders. Later, erosion of the whole area may remove all the surrounding soft materials. But, the stream channel will be preserved because of the hard materials that were deposited in it. In the end, you are left with a feature which is elevated above the landscape, but has the shape of the original stream. Geologists will then call the stream “inverted.”

<gallery class="center" widths="380px" heights="360px">

Image:ESP_024997ridges.jpg|Possible inverted stream channels, as seen by HiRISE under HiWish program. The ridges were probably once stream valleys that have become full of sediment and cemented. So, they became hardened against erosion which removed surrounding material.

ESP 036362 2195inverted.jpg|Inverted stream channels on crater slope, as seen by HiRISE under HiWish program Location is [[Diacria quadrangle]].
</gallery>

[[File:ESP 055431 1430invertedstream.jpg|thumb|400px|center|Inverted Stream channel It was once a stream, now it is a curved ridge.]]

==Exhumed Craters==

[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]

Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."

Exhumed terrain appears to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> <ref> https://www.uahirise.org/PSP_001374_1805</ref> The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under and around it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

[[File:57652 2215exhumed.marspedaijpg.jpg|thumb|400px|left|This crater had been buried and now is being uncovered by erosion. Had it just been formed, it would have destroyed part of the layered formation that is on top of its right side (just to the left of the crater).]]

[[File:48057 1560craterlayersclose.jpg|thumb|400px|center|The small crater that sits in layers is being exhumed. If it had been made after the layers that it is sitting in, it would have destroyed some of the layered material.]]

==Pedestal Craters==

[[File:ESP 037528 2350pedestal.jpg |Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

Pedestal crater The surface was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice.

A Pedestal crater is a crater with its ejecta sitting above the surrounding terrain. Its ejecta form a raised platform (like a pedestal).<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> They are produced when an impact ejects material that forms an erosion-resistant layer. Consequently, the immediate area erodes more slowly than the rest of the region. Some pedestals are hundreds of meters above the surroundings. This means that hundreds of meters of material were eroded away. What remains is a crater and its ejecta blanket sitting above the surrounding ground. <ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

<gallery class="center" widths="380px" heights="360px">
File:ESP 048021 2130pedestal2.jpg|Pedestal Crater with an odd ejecta pattern

Image: ESP 047615 1275pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program Top layer has protected the lower material from being eroded. Location is Hellas quadrangle, at 52.014° S and 110.651° E (249.349 W).

File:62242 2265pedestal.jpg|Pedestal crater
</gallery>

==Ridges==

[[File:36745 1905ridgesv2.jpg |Close view of ridges We are sure how these were formed, but we have come up with a few possibilities.]]

Close view of ridges We are sure how these were formed, but we have come up with a few possibilities.

Ridge fields are another feature that we do not yet fully understand.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref> <ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>
Hard ridges standing above the surroundings often meet at close to right angles. They may have something to do with cracks caused by impacts. Mineral laden water may then migrate up the cracks and harden. These fields can be quite complex and beautiful.

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.

File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle

</gallery>

[[File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle ]]

Ridge network in Amazonis quadrangle

==Layers==

[[File:44507 1880longlayersdanielson.jpg|600pxr|Layers in Dannielson Crater, as seen by HiRISE under HiWish program]]

Layers of rocks and other materials are very common on Mars.<ref>https://www.uahirise.org/PSP_007820_1505 Layered Sediments in Hellas Planitia</ref> They are found in many low places like craters.<ref>https://www.uahirise.org/hipod/PSP_008930_1880</ref> The widespread occurrence of layering on the Red Planet has great significance. On Earth, much layering originates in bodies of water.<ref>Namowitz, S., Stone, D. 1975. Earth science The World We Live in. American Book Company. N.Y. </ref> If this is true, at least to some extent on Mars, then traces of past life might be found in layered formations. Indeed, much evidence has been gathered for the existence of lakes in craters and some canyons.
Whether layers were created under water or through ground water, water is still being debated. Probably ground water is at least partial responsible for many of the layers we observe on the planet. The existence of water in the ground is important for life on Mars. Most of the organic mass on the Earth is found under the surface. Likewise, Mars may have a great deal of life living under the surface. <ref>https://microbewiki.kenyon.edu/index.php/Deep_subsurface_microbes</ref> <ref>Amend, J.. A. Teske. 2005. Expanding frontiers in deep subsurface microbiology. Palaeogeography, Palaeoclimatology, Palaeoecology: Volume 219, Issues 1–2, 131-155.</ref> Many microbes live deep underground.<ref>Pedersen, K. 1993. The deep subterranean biosphere. Earth Science Reviews: 34, 243-260.</ref> <ref> Stevens, T., J. McKiney. 1995. Lithoautotrophic Microbial Ecosystems in Deep Basalt Acquifers. Science: 270, 450-454.</ref> <ref>Fredrickson, J. , T. Onstott. 1996. Microbes Deep inside the Earth. Scientific American. October, 1996.</ref> Life under the Martian surface might find it easier since it would be protected from high levels of radiation.<ref>Boston, P., et al. 1992. On the Possibility of Chemosynthetic Ecosystems in Subsurface Habitats on Mars. Icarus: 95, 300-308.</ref> One recent study found that radiation from certain elements in the crust of Mars could have reacted with water in the ground to produce hydrogen. Hydrogen can supply chemical energy for life.<ref>http://astrobiology.com/2018/09/ancient-mars-had-right-conditions-for-underground-life.html</ref> <ref> Tarnas, J., et al. 2018 Radiolytic H2 Production on Noachian Mars: Implications for Habitability and Atmospheric Warming. Earth and Planetary Science Letters [https://doi.org/10.1016/j.epsl.2018.09.001</ref>

<gallery class="center" widths="380px" heights="360px">

File: 54763_1500layers2.jpg
File: 54763_1500layerscolor.jpg

File:59619 1845layers3.jpg|Close view of layers

File:59619 1845layers2labeled.jpg|Layers Different colors of the rocks means they contain different minerals.

ESP 048980 1725layers.jpg|Wide view of layers in Louros Valles, as seen by HiRISE under HiWish program Louros Valles is part of the Ius Chasma.
48980 1725layersclose2.jpg|Close view of layers in Louros Valles Note this is an enlargement of a previous image.

48980 1725layersclose.jpg|Close view of layers in Louros VallesNote this is an enlargement of a previous image.
ESP 048980 1725layersclosecolor.jpg|Close view of layers in Louros Valles Note this is an enlargement of a previous image.

File: 47421 1890bigbutte.jpg|Close view of layers, as seen by HiRISE under HiWish program. Box shows the size of a football field.
</gallery>

[[File:544858 1885topcloselayers5.jpg|thumb|400px|center|Close view of layers, as seen by HiRISE under HiWish program Location is Danielson Crater.]]

==Ribbed terrain==

Ribbed terrain consists of mostly elongated canyon-like forms. Some portions turn into mesas. It is created when small cracks become larger and larger. A crack in the surface of an ice-rich area will permit more of the ice to go into the thin Martian air because of increased surface area. This process of going directly form a solid to a gas phase is called sublimation. On Earth it is easily observed in the behavior of dry ice (solid carbon dioxide).

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows

[[File:28339 2245ribbbed.jpg|thumb|400px|center|Wide view of ribbed terrain.]]

[[File:ESP 025174 2245ribs.jpg|500pxr|Wide view of ribbed terrain.]]

Wide view of ribbed terrain.

[[File:25174 2245ribscolor.jpg|thumb|400px|center|Close, color view of ribbed terrain.]]

==Blocks and boulders forming==

Some places on Mars show rocks breaking into boulders or cube-shaped blocks.

[[File:26557joints.jpg|500pxr|Crossing joints, as seen by HiRISE under HiWish program]]

Crossing joints, as seen by HiRISE under HiWish program
<gallery class="center" widths="380px" heights="360px">
48144 1475layerscubes.jpg|Close view of layers, as seen by HiRISE under HiWish program Some of the layers are breaking up into large blocks
48144 1475cubes.jpg|Close view of layers Some layers are breaking up
</gallery>

[[File:26557rocksforming.jpg|Rocks forming|thumb|300px|left|Rocks forming]]

[[File:44757 2185fracturesblocks.jpg|thumb|300px|center|Blocks forming]]

[[File: 47577 1515blocks.jpg|thumb|400px|right|Surface breaking up into cube-shaped blocks]]

[[File: 46684 1280breaking.jpg|thumb|500px|center|Layers breaking up into boulders in Galle Crater, as seen by HiRISE under HiWish program]]

[[File:45377 2170blocks2.jpg|500pxr|Fractures forming large blocks Box shows size of a football field]]

Fractures forming large blocks Box shows size of a football field

==Volcanoes under ice==

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

Researchers believe they have found evidence that volcanoes erupt under ice on Mars.<ref>https://www.uahirise.org/ESP_071541_2200</ref> Such eruptions have been observed on the Earth. What seems to happen is that ice melts, the water escapes, and then the surface cracks and collapses. The resulting formation shows concentric fractures and large pieces of ground that seemed to have been pulled apart.<ref>Smellie, J., B. Edwards. 2016. Glaciovolcanism on Earth and Mars. Cambridge University Press.</ref> Sites like this may have recently had held liquid water; therefore, they may be good places to search for evidence of life.<ref name="Levy, J. 2017">Levy, J., et al. 2017. Candidate volcanic and impact-induced ice depressions on Mars. Icarus: 285, 185-194.</ref><ref>University of Texas at Austin. "A funnel on Mars could be a place to look for life." ScienceDaily. ScienceDaily, 10 November 2016. <www.sciencedaily.com/releases/2016/11/161110125408.htm>.</ref>

[[File:25755 2200collapse.jpg|thumb|400px|left|Close view of fractures from volcano under ice.]]

[[File:25755 2200tiltedlayers.jpg|thumb|400px|center|Close view of fractures from volcano under ice.]]

==Recurrent slope lineae==

Recurrent slope lineae are small, narrow, dark streaks on slopes that get longer in warm seasons. They may be evidence of liquid water.<ref>McEwen, A., et al. 2014. Recurring slope lineae in equatorial regions of Mars. Nature Geoscience 7, 53-58. doi:10.1038/ngeo2014</ref> <ref>McEwen, A., et al. 2011. Seasonal Flows on Warm Martian Slopes. Science. 05 Aug 2011. 333, 6043,740-743. DOI: 10.1126/science.1204816</ref> <ref>http://redplanet.asu.edu/?tag=recurring-slope-lineae|title=recurring slope lineae - Red Planet Report|website=redplanet.asu.edu|</ref> Evidence is still being gathered on this feature.

[[File:49955 1665rslcolorarrows (1).jpg|500pxr|Recurrent slope lineae (RSL) They form in warm seasons.]]

Recurrent slope lineae (RSL) They form in warm seasons.

==Notes about pictures==

Most pictures from spacecraft are enhanced. The surface of Mars shows little contrast. Consequently, in order to see more detail, contrast is enhanced by a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. This process makes a huge difference for some features like dark slope streaks. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red. Displaying colors in this way allows us to better identify rocks and minerals. Usually, color images are constructed in one of two ways. An IRB image assigns the output from the infrared channel to the color red, the wide red channel to the color green, and the blue-green channel to the color blue. On the other hand, a RGB image has the output of the broad red channel displayed as red, the blue-green channel as green, and a synthetic blue channel (blue-green minus part of the red) as blue. The wavelengths of these channels are: RED: 570-830 nanometers BG: <580 nanometers IR: >790 nanometers. One nanometer is equal to one billionth of a meter (0.000 000 001 m). HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.[12]

HiRISE images are about 5 km wide, but only have a 1 km wide band in the center that is in color.<ref>McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson</ref>

==How to suggest image==

To suggest a location for HiRISE to image visit the site at http://www.uahirise.org/hiwish

In the sign up process you will need to come up with an ID and a password. When you choose a target to be imaged, you have to pick and exact location on a map and write about why the image should be taken. If your suggestion is accepted, it may take 3 months or more to see your image. You will be sent an email telling you about your images. The emails usually arrive on the first Wednesday of the month in the late afternoon.

==Notes to teachers==

This article goes along with the video Features of Mars with HiRISE under HiWish program at https://www.youtube.com/watch?v=b7q1Xyz_LBc

==References==
{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.jpl.nasa.gov/missions/viking-1/ OP Lunch Talk #10: HiWish, public suggestion targeting web tool for Mars imaging with MRO/HIRISE]

*[https://www.youtube.com/watch?v=0fQHEay-Yas&list=PLn0lnGc1Saik-yyWpeec3AWz9NgdtxDAF&index=122 How to Explore Mars without Leaving Your Chair - Jim Secosky - 23rd Annual Mars Society Convention]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]
*[[Viking 2]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

File:76854 2220pingo.jpg

2023-03-04T22:46:13Z

Suitupandshowup: Possible pingos, as seen by HiRISE under HiWish program. Source: https://www.uahirise.org/ESP_076854_2220 Credit: NASA/JPL/University of Arizona

== Summary ==
Possible pingos, as seen by HiRISE under HiWish program.

Source: https://www.uahirise.org/ESP_076854_2220

Credit: NASA/JPL/University of Arizona

== Licensing ==
{{PD}}

Curiosity

2023-02-20T22:33:35Z

Suitupandshowup: /* Water */ added info and ref

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating.
In the future, colonists may be able to use the opal as a source of water. Just two halos that have an area of a square meter could contain one to 1.5 gallons of water in the top foot.<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref> <ref>Gabriel, T., et al. 2022. On an Extensive Late Hydrologic Event in Gale Crater as Indicated by Water-Rich Fracture Halos. JGR Planets. Volume127, Issue12 e2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

[[File:Curiosityripplemarks.jpg|left|thumb|320px| Ripple marks in Gale Crater that show water was there.]]

NASA released a picture in February 2023 that shows strong evidence for water. "This is the best evidence of water and waves that we've seen in the entire mission," said Ashwin Vasavada, Curiosity's project scientist at NASA's Jet Propulsion Laboratory in Southern California. These kind of ripple marks are common on Earth along the seashore or bottom of shallow lakes. In the distant past on Mars, waves on the surface of a shallow lake stirred up sediment at the lake bottom to form rippled textures.<ref> https://www.forbes.com/sites/davidbressan/2023/02/09/nasas-curiosity-rover-finds-first-traces-of-a-fossil-lake-on-mars/?sh=10a253dca82f</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

Curiosity

2023-02-20T22:27:07Z

Suitupandshowup: /* Water */ added image

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating.
In the future, colonists may be able to use the opal as a source of water. Just two halos that have an area of a square meter could contain one to 1.5 gallons of water in the top foot.<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref> <ref>Gabriel, T., et al. 2022. On an Extensive Late Hydrologic Event in Gale Crater as Indicated by Water-Rich Fracture Halos. JGR Planets. Volume127, Issue12 e2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

File:Curiosityripplemarks.jpg

[[File:Curiosityripplemarks.jpg|left|thumb|320px| Ripple marks in Gale Crater that show water was there.]]

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

File:Curiosityripplemarks.jpg

2023-02-20T22:22:38Z

Suitupandshowup: Ripple marks in Gale crater, as seen by Curiosity Rover Source: https://www.forbes.com/sites/davidbressan/2023/02/09/nasas-curiosity-rover-finds-first-traces-of-a-fossil-lake-on-mars/?sh=10a253dca82f Credit: NASA/JPL-CALTECH/MSSS

== Summary ==
Ripple marks in Gale crater, as seen by Curiosity Rover

Source: https://www.forbes.com/sites/davidbressan/2023/02/09/nasas-curiosity-rover-finds-first-traces-of-a-fossil-lake-on-mars/?sh=10a253dca82f

Credit: NASA/JPL-CALTECH/MSSS
== Licensing ==
{{PD}}

Curiosity

2023-01-10T23:12:46Z

Suitupandshowup: /* Water */

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating.
In the future, colonists may be able to use the opal as a source of water. Just two halos that have an area of a square meter could contain one to 1.5 gallons of water in the top foot.<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref> <ref>Gabriel, T., et al. 2022. On an Extensive Late Hydrologic Event in Gale Crater as Indicated by Water-Rich Fracture Halos. JGR Planets. Volume127, Issue12 e2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

Curiosity

2023-01-10T15:46:48Z

Suitupandshowup: /* Water */

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating.
In the future, colonists may be able to use the opal as a source of water<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

Curiosity

2023-01-10T15:45:43Z

Suitupandshowup: /* Water */

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating it.
In the future, colonists may be able to use the opal as a source of water<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

Curiosity

2023-01-10T15:45:06Z

Suitupandshowup: /* Water */ added new info

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed. The halos represent the tops of large subsurface networks that once held water.
Curiosity's instruments found the halos to contain opal. Opal is rich in water which can be obtained by just heating it.
In the future, colonists may be able to use the opal as a source of water<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006600</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

Curiosity

2023-01-10T14:10:11Z

Suitupandshowup: /* Water */ added new info and ref

[[Image:CuriosityIcon.jpg|thumb|right]]

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

'''Curiosity''' is the last and most advanced [[rover]] from [[NASA]]. It carries several instruments for scientific investigation. One of the goals is to find signs of life on the Martian surface or a few centimeters below.

Curiosity took off on November 26, 2011 atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida.<ref> https://mars.nasa.gov/msl/mission/timeline/launch/</ref> It landed on August 6, 2012 in Gale Crater in the Aeolis quadrangle at 4.5895 degrees S and 137.4417 degrees E.<ref>https://www.skyandtelescope.com/astronomy-news/watch-curiosity-descend-onto-mars/</ref> <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> It's landing was in the northern part of Gale Crater. Curiosity nailed its landing—“so close to the target that the offset was almost equivalent to a rounding error.”<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> Its destination, Gale Crater, was chosen because it contained a large layered mountain. The mountain’s original name was Mt. Aeolis, but it has been changed to Mt. Sharp in honor of Robert P. Sharp (1911–2004), a field geologist and professor at Caltech. The original name Mt. Aeolis came from Greek mythology, it was a floating island where winds were held in a cave inside a mountain.<ref> https://www.skyandtelescope.com/astronomy-news/mount-sharp-or-aeolis-mons/</ref> With a height of 18,000 feet (3.4 miles--5.5 Km), Mt. Sharp is higher than any mountain in the continental United States.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref> https://mars.nasa.gov/resources/4494/the-heights-of-mount-sharp/</ref> “Bradbury,” after the famous science fiction writer Ray Bradbury was picked for the name of the touchdown spot.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

<gallery class="center" widths="190px" heights="180px" >

File:MRO sees Curiosity landing.jpg|Curiosity Rover descending to surface with parachute, as photographed by HiRISE.
File:PIA15279 3rovers-stand D2011 1215 D521.jpg|Three rovers with engineers for scale Sojourner is in the front. Spirit/Opportunity is to the left. The largest is Curiosity to the right. The setting is JPL's Mars Yard testing area.
File:First two full-resolution images from the Curosity rover.jpg| First two full-resolution images of the Martian surface from the Navigation cameras The eroded rim of Gale Crater is in the distance. The foreground shows two zones of excavation probably made by blasts from the rover's descent stage thrusters.

File: Mars-curiosity-rover-msl-rock-layers-PIA21042-full2.jpg|View from Mastcam on Curiosity showing sloping buttes and layered outcrops on lower Mount Sharp

</gallery>

[[File:PIA16158-Mars Curiosity Rover-Water-AlluvialFanlandingsite.jpg|600pxr| Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments.]]

Landing site for Curiosity in northern part of Gale Crater The black oval indicates the "landing ellipse," and the cross shows where the rover actually landed. Nearby a stream, called “Peace Vallis” built an alluvial fan from water and sediments. Peace Vallis is a stream that ran off of the north rim of the crater.

==Spacecraft==

Curiosity has a mass of 1,982 pounds max (899 kilograms). It is 10 feet (3 meters) long, 9 feet (2.7 meters) wide, and 7 feet (2.2 meters) tall. Power is provided by a radioisotope thermoelectric generator that provides (about 2,700 watt hours per sol).<ref>https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf</ref> However, it does not generate much instant power. Instead it is slowly charging its batteries all the time. When the batteries have a good charge, they can supply Curiosity with all the power it requires. It uses two rechargeable lithium-ion batteries with each having a capacity of about 42 ampere-hours.<ref>https://en.wikipedia.org/wiki/Curiosity_%28rover%29</ref>

[[File:4392 edl20120809-full2landingsteps.jpg |600pxr|Events of Curiosity’s landing]]

Events for Curiosity’s landing

It employed an interesting, though complex, method of landing. Because it had so many instruments and mass it could not use the bouncing air bags that other successful rovers had used. First parachutes slowed the craft, and then four engines fired to just about stop the descent. With the vehicle basically floating above the ground, it was lowered down a “umbilical cord.” Upon safely landing, the cord was cut and the descent stage flew away at full throttle. This new scheme of landing is called the Sky Crane maneuver. <ref> https://mars.nasa.gov/msl/mission/technology/insituexploration/edl/skycrane/</ref>
Curiosity is a rover, but a very slow rover. Its top speed is 450 feet/hour—less than a quarter mile/hour. Many seem to believe that we should stick to an unmanned approach to exploration. However, remember the Apollo astronauts went 8-11 miles/hour on the far rougher terrain on the moon.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>

== Instruments==

[[File:4077 malin-4rovercam-full.jpg |right|thumb|320px|| Cameras on Curiosity]]

Mast Camera (Mastcam)

Mars Hand Lens Imager (MAHLI)

Mars Descent Imager (MARDI)

Spectrometers:
Alpha Particle X-Ray Spectrometer (APXS)

Chemistry & Camera (ChemCam)

Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument (CheMin)
Sample Analysis at Mars (SAM) Instrument Suite

Radiation Detectors:
Radiation Assessment Detector (RAD)

Dynamic Albedo of Neutrons (DAN)

Environmental Sensors:
Rover Environmental Monitoring Station (REMS)

Atmospheric Sensors

Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI)<ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref>

==Findings==

===Water===

Just days into its mission, Curiosity discovered strong evidence of an ancient streambed where water once flowed knee-deep. As the mission progressed, more and more signs of water accumulated. Great amounts of past water had been suggested by most scientists based upon decades of data from both orbiting satellites and lander/rovers. [[Mariner 9]], [[Viking 1]], [[Viking 2]], [[Mars Odyssey]], [[Mars Global Surveyor]], Mars Express, and [[Mars Reconnaissance Orbiter]] all have imaged features resembling river valleys.<ref>https://hirise.lpl.arizona.edu/PSP_007925_1990</ref> <ref>Goudge, T., et al. 2017. STRATIGRAPHY AND EVOLUTION OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 1195.pdf.</ref> <ref>Baker, V. 1982. The Channels of Mars. Univ. of Tex. Press, Austin, TX</ref> <ref>Baker, V., R. Strom, R., V. Gulick, J. Kargel, G. Komatsu, V. Kale. 1991. Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352, 589–594.</ref> Many researchers believe there have been lakes on Mars. <ref>Goudge, T., K. Aureli, J. Head, C. Fassett, J. Mustard. 2015. Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars. Icarus: 260, 346-367.</ref> <ref>Fassett, C. J. Head. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.</ref> <ref> Zhao, J., et al. 2018. PALEOLAKES IN THE NORTHWEST HELLAS REGION: IMPLICATIONS FOR PALEO-CLIMATE AND REGIONAL GEOLOGIC HISTORY. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083).</ref> Some have developed a argument for an ocean covering a full third of the planet.<ref> https://www.sciencedaily.com/releases/2010/06/100613181245.htm</ref> <ref>Gaetano Di Achille, Brian M. Hynek. Ancient ocean on Mars supported by global distribution of deltas and valleys. Nature, 2010; DOI: 10.1038/ngeo891</ref> <ref> Head et al. 1999. Possible Ancient oceans on Mars: Evidence from mars orbiter laser Altimeter Data. Science 286, 2134.</ref> <ref>Carr,M. 1996. Water on Mars. Oxford.</ref> <ref> Parker, T.J., Saunders, R.S., and Schneeberger, D.M., 1989, Transitional morphology in the west Deuteronilus Mensae region of Mars: Implications for modification of the lowland/upland boundary: Icarus , v. 82, 111–145, doi:10.1016/0019-1035(89)90027-4.</ref> <ref> Parker, T., et al. 1993. Coastal geomorphology of the Martian northern plains. Journal of Geophysical Research. 98. 11061.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> <ref> Carr, M. , J. Head. 2003. Oceans of Mars: An assessment of the observational evidence and possible fate. Journal of Geophysical Research. 108(E5). 5041. Doi:10.1029/2002JE001963, 2003.</ref> The [[Phoenix Mars Mission]] actually found ice in the soil and there may have been drops of liquid water observed that formed with the heat of the descent engines.<ref> https://www.space.com/6394-phoenix-mars-lander-liquid-water-scientists.html</ref> <ref> https://www.skyandtelescope.com/astronomy-news/drops-of-water-on-mars/</ref> <ref> https://www.astrobio.net/mars/liquid-water-ice-salt-mars/</ref> <ref>Smith, P., et al. 2009. H2O at the Phoenix Landing Site. Science: 325, 58-61.</ref> <ref>https://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080530.html</ref> The Mars rovers [[Spirit]] and [[Opportunity]] have found evidence for a watery past. However, the vast and varied amounts of data from Curiosity have sealed the case for a wet, early Mars. It is now accepted that a large, long-lived lake existed in Gale Crater.
The presence of water is a prerequisite for life. Hence, the case for life on Mars at present or at least in the past has been greatly strengthened by Curiosity’s explorations, experiments, and measurements.
Following are some of the individual studies that have led to the conclusion that Gale Crater once harbored a lake.

[[File:5316 pia17062 Hottah WB-full2conglomerate.jpg |left|thumb|320px|Conglomerate rock called “Hottah" after Hottah Lake in Canada's Northwest Territories. Conglomerate is composed of rounded pebbles that had to be formed in running water.]]

As early as September 27, 2012,NASA scientists announced that ''Curiosity (rover)'' found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.<ref>https://www.nasa.gov/home/hqnews/2012/sep/HQ_12-338_Mars_Water_Stream.html</ref> <ref>Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012.</ref> <ref>Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouelic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; et al. (2013-07-25). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref> <ref>Williams R.; et al. (2013). "Martian fluvial conglomerates at Gale Crater". Science. 340 (6136): 1068–1072.</ref>
Mars scientists, in a press conference on December 8, 2014, described observations by Curiosity rover that show Mars' Mount Sharp was made by sediments deposited in a large lake bed over tens of millions of years. This finding suggests the climate of ancient Mars could have been conducive to long-lasting lakes at many places on the Planet. Many scientists had suggested this long ago. There is a long list of where lakes may have existed in the distant past. Rock layers in Gale imply that a huge lake was filled and evaporated many times. Many deltas stacked upon each other support this contention.<ref>https://www.nasa.gov/press/2014/december/nasa-s-curiosity-rover-finds-clues-to-how-water-helped-shape-martian-landscape</ref> <ref>https://www.nytimes.com/2014/12/09/science/-stronger-signs-of-life-on-mars.html</ref> <ref>https://www.jpl.nasa.gov/video/details.php?id=1346</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4398</ref>

<gallery class="center" widths="190px" heights="180px" >

File:6866 mars-curiosity-rover-mastcam-sedimentary-deposit-lakebed-rocks-pia19074-full2.jpg|This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.

File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
File:8023 mars-curiosity-rover-msl-rock-layers-PIA21045-full2murray.jpg|Rock layers in the Murray Buttes area in lower Mount Sharp
</gallery>

[[File:PIA19080-MarsRoverCuriosity-AncientGaleLake-Simulated-20141208.jpg|600pxr|Simulated view of past lake in Gale Crater]]

Simulated view of past lake in Gale Crater

After more observations, on October 8, 2015, a large team of scientists confirmed the existence of long-lasting lakes in Gale Crater. The team came to this conclusion based on evidence of old streams with coarser gravel in addition to places where streams appear to have emptied out into bodies of standing water. If lakes were once present, Curiosity would start seeing water-deposited, fine-grained rocks closer to Mount Sharp. That is exactly what was observed. Finely laminated mudstones were discovered by Curiosity; this lamination represents the settling of plumes of fine sediment through a standing body of water. Sediment deposited the Gale Crater lake formed the lower portion of Mount Sharp, the mountain in Gale crater.<ref>http://astrobiology.com/2015/10/wet-paleoclimate-of-mars-revealed-by-ancient-lakes-at-gale-crater.html</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=4734</ref> <ref> Grotzinger, J.P.; et al. (October 9, 2015). "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars". Science: 350 (6257): aac7575.</ref>
Research presented in 2018 at the Geological Society of America Annual Meeting in Indianapolis, Indiana explained evidence for huge floods in Gale Crater. Of great significance was a conglomerate rock unit with particles up to 20 centimeters across. To create such a type of rock, water must have been 10 to 20 meters in depth. Between 2 million years to 12,000 years ago, Earth experienced these types of floods.<ref>https://phys.org/news/2018-11-evidence-outburst-plentiful-early-mars.html</ref> <ref>Significance of Flood Deposits in Gale Crater, Mars. Geological Society of America Abstracts with Programs. Vol. 50, No. 6 DOI: 10.1130/abs/2018AM-319960, https://gsa.confex.com/gsa/2018AM/webprogram/Paper319960.html</ref> <ref>https://www.sciencedaily.com/releases/2018/11/181105132920.htm</ref> Conglomerate is a rock composed of rounded rocks of various sizes. Rounded rocks are produced by traveling down streams. In the streams they become rounded by hitting the steam bottom and each other.
Besides physical evidence of water, there was much more supporting signs of water that was detected by various instruments on Curiosity. Although some are subtle and complicated, they are consistent with a history of water. For instance, many minerals require water for their formation. Many of these types of minerals are in Gale Crater. Curiosity was able to even examine small veins and determine their composition which often turned out to be different than the surrounding rocks. Veins form when fluids move through cracks in rocks.<ref>https://mars.nasa.gov/resources/7056/prominent-veins-at-garden-city-on-mount-sharp-mars/</ref>

Researched published in nature Geoscience in October 2019, described how Gale crater underwent many wet and dry cycles as its lake waters disappeared.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7514</ref>
Sulfate salts from evaporated water showed that pools of salty water once existed in Gale Cater. These ponds could have supported organisms. Curiosity found magnesium sulfate salts which means that the lake must have almost totally evaporated because this salt does not crystalize out from a water solution until nearly all the water has evaporated.<ref>https://www.pbs.org/wgbh/nova/article/salt-lake-gale-crater-mars/?linkId=74886308</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2018/pdf/2936.pdf</ref> The remaining pools of water would have been very salty--such lakes on Earth contain organisms that are salt tolerant. These minerals were found along the edges of what were lakes.<ref>https://www.sciencealert.com/the-mars-gale-crater-may-have-once-held-a-sloshing-salty-lake-3-3-to-3-7-billion-years-ago</ref>

Researchers who examined halos concluded that much water remained in the ground after the lake dried up. Microbes may have been able to live there much longer than was previously believed.<ref>https://astrobiology.com/2023/01/mars-curiosity-rover-discovers-water-rich-fracture-halos-in-gale-crater.html?fbclid=IwAR3ltrseN-2NYB1y2LLJ-pAFtLEEK_7yP5dQzLa9WkeoJ-SxpKAnofUPitM</ref>

<gallery class="center" widths="190px" heights="180px">

File:7528 pia19921-MAIN Blaney1 sol-0938 ML-full2veins.jpg| Curiosity's laser-firing Chemistry and Camera (ChemCam) here at Garden City found calcium sulfate in some veins and magnesium sulfate in others. Some veins contained fluorine or varying amounts of iron.
File:7056 mars-rover-curiosity-mount-sharp-sol929-pia19161-full2veins.jpg|Veins Veins form when fluids move through cracks in the rock. They are exposed here because erosion has removed the softer rock that the veins were in.
</gallery>

Some of the more indirect findings are mentioned below.
Signs of mineral hydration, probably hydrated calcium sulfate, were reported by NASA on March 18, 2013, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock plus in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.bbc.com/news/science-environment-21340279</ref> Minerals that are hydrated needed water to become hydrated, so finding hydrated minerals means that water must have been present.
By the start of 2016, Curiosity had detected seven hydrous minerals. The minerals are actinolite, montmorillonite, saponite, jarosite, halloysite, szomolnokite and magnesite. In some places 40 vol% of the minerals were hydrous minerals. Note that all of these minerals must have formed in water. <ref>Lin H.; et al. (2016). "Abundance retrieval of hydrous minerals around the Mars Science Laboratory landing site in Gale crater, Mars". Planetary and Space Science. 121: 76–82.</ref>

[[File:7505 mars-curiosity-rover-gale-crater-beauty-shot-pia19839-full2.jpg |right|thumb|320px| Rocks layers from the “Kimberley” formation Layers like this are usually formed under water.]]

Scientists found manganese oxides in mineral veins in the "Kimberley" region of Gale Crater by using Curiosity's laser-firing device (ChemCam). These minerals need lots of water and oxidizing conditions to form; therefore, this finding points to a water-rich, oxygen-rich past.<ref>NASA/Jet Propulsion Laboratory. "NASA rover findings point to a more Earth-like Martian past." ScienceDaily. ScienceDaily, 27 June 2016. <www.sciencedaily.com/releases/2016/06/160627125731.htm>.</ref> <ref>Lanza, Nina L.; Wiens, Roger C.; Arvidson, Raymond E.; Clark, Benton C.; Fischer, Woodward W.; Gellert, Ralf; Grotzinger, John P.; Hurowitz, Joel A.; McLennan, Scott M.; Morris, Richard V.; Rice, Melissa S.; Bell, James F.; Berger, Jeffrey A.; Blaney, Diana L.; Bridges, Nathan T.; Calef, Fred; Campbell, John L.; Clegg, Samuel M.; Cousin, Agnes; Edgett, Kenneth S.; Fabre, Cécile; Fisk, Martin R.; Forni, Olivier; Frydenvang, Jens; Hardy, Keian R.; Hardgrove, Craig; Johnson, Jeffrey R.; Lasue, Jeremie; Le Mouélic, Stéphane; Malin, Michael C.; Mangold, Nicolas; Martìn-Torres, Javier; Maurice, Sylvestre; McBride, Marie J.; Ming, Douglas W.; Newsom, Horton E.; Ollila, Ann M.; Sautter, Violaine; Schröder, Susanne; Thompson, Lucy M.; Treiman, Allan H.; VanBommel, Scott; Vaniman, David T.; Zorzano, Marìa-Paz (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars". Geophysical Research Letters. 43 (14): 7398–7407.</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=6544</ref>
A study of types of minerals in veins found that evaporating lakes were extant in the past in Gale crater. The Sheepbed Member mudstones of Yellowknife Bay (YKB) were investigated in this research.<ref>Schwenzer, S. P.; Bridges, J. C.; Wiens, R. C.; Conrad, P. G.; Kelley, S. P.; Leveille, R.; Mangold, N.; Martín-Torres, J.; McAdam, A.; Newsom, H.; Zorzano, M. P.; Rapin, W.; Spray, J.; Treiman, A. H.; Westall, F.; Fairén, A. G.; Meslin, P.-Y. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars". Meteoritics & Planetary Science. 51 (11): 2175–202.</ref> <ref>https://www.sciencedaily.com/releases/2016/08/160805085749.htm</ref>
In January, 2017, JPL scientists announced the discovery of mud cracks in Gale Crater. Such mud cracks form with the aid of water.<ref>https://www.jpl.nasa.gov/spaceimages/details.php?id=pia21263</ref> <ref>http://spaceref.com/mars/desiccation-cracks-reveal-the-shape-of-water-on-mars.html</ref> <ref>Stein, N.; Grotzinger, J.P.; Schieber, J.; Mangold, N.; Hallet, B.; Newsom, H.; Stack, K.M.; Berger, J.A.; Thompson, L.; Siebach, K.L.; Cousin, A.; Le Mouélic, S.; Minitti, M.; Sumner, D.Y.; Fedo, C.; House, C.H.; Gupta, S.; Vasavada, A.R.; Gellert, R.; Wiens, R. C.; Frydenvang, J.; Forni, O.; Meslin, P. Y.; Payré, V.; Dehouck, E. (2018). "Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater". Geology. 46 (6): 515–518.</ref>
Analysis using data from the rover’s Dynamic Albedo of Neutrons (DAN) scientists acquired evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 2 feet (60cm), between the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref>
Mars even has liquid water at times according to measurements made by Curiosity. Since the humidity goes to 100% at night, salts, similar to calcium perchlorate, will absorb water from the air and make brine in the soil. This manner in which a salt absorbs water from the air is called deliquescence. Liquid water results even though the temperature is very low because salts lower the freezing point of water. We use this idea to melt snow/ice by spreading salt on roads. The liquid brine produced in the night at Gale Crater evaporates after sunrise. Higher amounts of liquid water are expected in higher latitudes where the colder temperature can result in higher levels of humidity more often.<ref> https://www.jpl.nasa.gov/news/news.php?feature=4549</ref> <ref>University of Copenhagen – Niels Bohr Institute. "Mars might have salty liquid water." ScienceDaily. 13 April 2015. <www.sciencedaily.com/releases/2015/04/150413130611.htm>.</ref> Researchers cautioned that the amount of water was not enough to support life; however, it could allow salts to move around in the soil.<ref>https://www.space.com/29072-mars-liquid-water-at-night.html</ref> The brines would occur commonly in the upper 5 cm of the surface, but there is evidence that the effects of liquid water can be detected down to 15 cm. Chlorine-bearing brines are corrosive; therefore design changes may need to be made for future landers.<ref>Martin-Torre, F. et al. 2015. Transient liquid water and water activity at Gale crater on Mars. Nature geoscienceDOI:10.1038/NGEO2412</ref>

===Radiation levels===

Measurements of radiation levels are necessary for human missions to the surface of Mars, to provide microbial survival times of any possible extant or past life, and to determine how long conceivable organic biosignatures can be preserved. Astronauts on Mars would need to spend most of their time underground for protection from radiation. Future colonies would probably be in lava tunnels; Mars has an abundance of volcanoes, so lava tunnels may be common. Also, perhaps in the future we may have developed robotic earth movers which could move dirt around for cover.

[[File:PIA16938-RadiationSources-InterplanetarySpace.jpg |600px| Sources of dangerous radiation in space ]]

Curiosity took accurate readings of radiation on the way to Mars as well as on the surface. The absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the Martian surface for ~300 days of observations during the current solar maximum was measured. This study estimates that a one-meter depth drill is necessary to access possible viable radioresistant microbe cells. The actual absorbed dose measured by the Radiation Assessment Detector (RAD) is 76 mGy/yr at the surface. Based on these quantities, for a round trip Mars surface mission with 180 days (each way) cruise, and 500 days on the Martian surface for this current solar cycle, an astronaut would be exposed to a total mission dose equivalent of ~1.01 sievert. One Sievert exposure is associated with a five percent increase in risk for developing fatal cancer. NASA's current lifetime limit for increased risk for its astronauts operating in low-Earth orbit is three percent.<ref>http://spaceref.com/mars/understanding-mars-past-and-current-environments.html</ref>
Maximum shielding from galactic cosmic rays can be obtained with about 3 meters of Martian soil.<ref>Hassler, D.; et al. (2013). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover" (PDF). Science (Submitted manuscript). 343 (6169): 1244797.</ref>

Measuring the [[radiation]] levels, Curiosity finds no stronger radiation on the Martian surface than in low Earth orbit, where the [[ISS]] is. This seems the result of Mars' [[atmosphere]] deflecting parts of the cosmic rays. This is very good news as it simplifies significantly the construction of [[house|living quarters]] for the settlers. However, the intensity of [[solar flares]] still needs to be measured.<ref>[http://www.newscientist.com/article/dn22520-mars-is-safe-from-radiation--but-the-trip-there-isnt.html Mars is safe from radiation – but the trip there isn't]</ref>

The origin of Cosmic rays are not greatly understood. Most are small atomic particles, but some are the nuclei of heavier atoms.<ref> http://certificate.ulo.ucl.ac.uk/modules/year_one/NASA_GSFC/goddard/imagine.gsfc.nasa.gov/docs/science/know_l2/cosmic_rays.html</ref>
They are a major concern in space because they can damage living cells and electronics. The Earth’s atmosphere and magnetic field protect us from their effects. However, they are a potential problem on Mars which has only a very thin atmosphere and no magnetic field. A small number of cosmic rays can have about 40 million times the energy of particles accelerated by the largest particle accelerators.<ref>https://home.cern/science/accelerators/large-hadron-collider</ref> The energy of the most powerful cosmic rays is equal to a baseball moving at 56 mph (90 km/hr.)<ref>https://en.wikipedia.org/wiki/Cosmic_ray</ref>

===Methane===

There have been sporadic detections of methane in the Martian atmosphere. Methane can be given off by living organisms; therefore, methane may be an indication of life on Mars. On the other hand, there are other ways of getting methane—ones that do not involve biology. Still this gas should be looked into. Curiosity, at first found no methane, but later found that its level goes up and down.<ref>http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-387_Mars_Atmosphere.html NASA Rover's NASA'S Curiosity Rover Provides Clues to Changes in Martian Atmosphere</ref>

NASA announced in December 2014 that Curiosity had detected sharp increases in methane four times out of twelve during a 20-month period with the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars instrument (SAM). Methane levels were ten times greater than usual. Because of the temporary nature of the methane spike, scientists think the source is localized. The source may be biological or non-biological.<ref>https://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars</ref> <ref>Webster1, C. et al. 2014. Mars methane detection and variability at Gale crate. Science. 1261713</ref> <ref>https://www.nbclosangeles.com/news/local/Mars-Rover-Curiosity-Methane-285996081.html</ref>

[[File:Methane-3D-balls.png |right|thumb|320px| Methane contains 4 hydrogen atoms and 1 carbon atom covalently bonded to each other. Methane has been detected on Mars, and it could come from living organisms.]]

After two full Martian years (five Earth years) of measurements, researchers found that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. However, it must be noted that methane levels rise and fall with the seasons, going from 0.24 ppb in winter to 0.65 ppb in summer. They also observed some relatively large methane spikes, up to about 7 ppb, at random intervals.<ref> https://www.sciencenews.org/article/curiosity-finds-mars-methane-changes-seasons</ref> <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>
The existence of methane in the Martian atmosphere is exciting because on Earth, most methane is produced by living organisms. Methane on Mars does not prove that life exists there, but it is consistent with life. Ultraviolet radiation from the sun destroys methane; hence, methane doesn’t last long. To explain its presence something must have been creating or releasing it <ref>Webster, C., et al. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science: 360, June 8, 2018, p. 1093. doi:10.1126/science.aaq0131.</ref>

===Organic Chemicals===

Curiosity cannot find and was not designed to find alien life on Mars. But, it has the capacity to look for and identify some organic chemicals. Organic chemicals are associated with life. But one must be aware that a certain amount of organic chemicals are expected on the surface due to the arrival of meteorites over billions of years. Some types of meteorites are loaded with a variety of organic chemicals.

[[File:PIA17085-MarsCuriosityRover-TraverseMap-Sol351-20130801.jpg |600pxr|Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.]]

Map showing where Curiosity went in the first year Organic chemicals were found in the Yellow-knife Bay region in Sheepbed mudstone.

The first major testing of the Martian soil yielded interesting results. On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. The presence of perchlorates in the sample seems highly likely. The presence of sulfate and sulfide is also likely because sulfur dioxide and hydrogen sulfide were detected. Small amounts of chloromethane, dichloromethane and trichloromethane were detected. The source of the carbon in these molecules is unclear. Possible sources include contamination of the instrument, organics in the sample and inorganic carbonates.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399</ref> <ref>https://thelede.blogs.nytimes.com/2012/12/03/mars-rover-discovery-revealed</ref> Perchlorates, first discovered by the [[Phoenix]] mission can complicate the measurement of organic chemicals. Perchlorates may destroy organic chemicals.

[[File:7858 mars-curiosity-rover-msl-drill-targets-samples-map-pia20748-full2.jpg |600px| Map showing the first 14 drill sites Some important locations are labeled.]]

Map showing the first 14 drill sites Some important locations are labeled.

In a series of six articles in the journal ''Science'' December 9, 2013, teams of NASA researchers described, many new discoveries from the ''Curiosity'' rover including possible organics that could not be explained by contamination.<ref> Blake, D.; et al. (2013). "Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow – Medline" (PDF). Science (Submitted manuscript). 341 (6153): 1239505.</ref> <ref>Leshin, L.; et al. (2013). "Volatile, isotope, and organic analysis of martian fines with the Mars Curiosity rover - Medline". Science. 341 (6153): 1238937.</ref>
Although the organic carbon was probably from Mars, it can all be explained by dust and meteorites that have landed on the planet.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Flynn, G. (1996). "The delivery of organic matter from asteroids and comets to the early surface of Mars". Earth Moon Planets. 72 (1–3): 469–474.</ref>

[[File:5001 pia16564 Sol-133 LNav SnakeRiver-full2yellowknife.jpg |right|thumb|320px|Yellowknife Bay with "Snake River" Sheepbed mudstone which contains organic chemicals is found in this location. “Yellowknife” is a town in Canada. The oldest rocks in North America can be found there.<ref> Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref>
]]

Because much of the carbon was released at a relatively low temperature in Curiosity’s Sample Analysis at Mars (SAM) instrument package, it probably did not come from carbonates in the sample. Carbonates are expected when there is water and carbon dioxide present. Both were probably abundant in the past on Mars. The carbon could be from organisms, but this has not been proven. This organic-bearing matter was obtained by drilling 5 centimeters deep in a site called Yellowknife Bay into a rock called "Snake River." The samples were named ”John Klein” and “Cumberland.” Microbes could be living on Mars by obtaining energy from chemical imbalances between minerals in a process called chemolithotrophy which means “eating rock.”<ref> Grotzinger, J.; et al. (2013). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science. 343 (6169): 1242777.</ref>
Later, after further analysis, a team of researchers on December 16, 2014 explained their conclusions that organic compounds have been found on Mars. The compounds were found in samples from drilling into Sheepbed mudstone. Chlorobenzene and several dichloroalkanes, such as dichloroethane, dichloropropane and dichlorobutane were discovered in the samples.<ref>https://www.sciencedaily.com/releases/2014/12/141216144137.htm</ref> <ref>https://www.nasa.gov/content/goddard/mars-organic-matter</ref>

[[File:PIA17603 Erosion by Scarp Retreat in Gale Crater, Annotated Version.jpg |left|thumb|320px|Location of Sheepbed mudstone where organic chemicals were found. White X is about 43 feet (13 meters) higher in elevation than the Sheepbed-Gillespie contact and at a distance of about 780 feet (240 meters).]]

At a June 2018 press conference it was announced the detection of more organic molecules in a drill sample analyzed by Curiosity.<ref>Eigenbrode, J., et al. Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars. Science: 360, June 8, 2018, p. 1096. doi:10.1126/science.aas9185.</ref> Some of the organic molecules found were thiophenes, benzene, toluene, and small carbon chains, such as propane or butane.<ref>http://astrobiology.com/2018/06/curiosity-finds-ancient-organic-compounds-that-match-meteoritic-samples.html</ref> The identity of all the chemicals were not all resolved. At least 50 nanomoles of organic carbon are still in the sample, but were not specifically determined. The remaining organic material probably exists as macromolecules organic sulfur molecules. Organic matter was from lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, by the Sample Analysis at Mars instrument suite. <ref>Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice (2018). "Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars". Science: (6393): 1096–1101.</ref>

In late June, 2022, NASA announced the amount of total carbon found in early samples at Gale Crater. At least 200 to 273 parts per million of organic carbon was measured. This level of organics is comparable to or even greater than the amount found in rocks in some locations on Earth, such as in the Atacama Desert This amount is even more than found in Mars meteorites. Organic cemicals are evidence that Mars could have had life, but organic carbon can also come from nonliving sources, such as meteorites, volcanoes, or be formed in place by surface reactions. <ref>https://www.jpl.nasa.gov/news/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220627-1</ref> <ref>https://www.youtube.com/watch?v=65sibaYV2X8</ref>

===Minerals and Rocks of Mars===

With a complex of instruments on Curiosity, we were able to determine a great deal more about the geological make-up and history of Mars. Many, may rocks and soil samples were analyzed by various devices. Basically, we understand Mars as being mostly made of volcanic materials, especially the dark rock basalt which comes out of volcanoes. Mars has many huge volcanoes so this is to be expected.
We also found that many of the minerals that weather from basalt. By studying these minerals we can arrive at conclusions about the past conditions that produced them. Many of the minerals were hydrated. That means that water was around. Some of the minerals are clay minerals; clay minerals are significant because not only do they need lots of water to form, but they can’t develop in acid conditions. So, in summary the examinations of rocks/minerals show that Gale Crater contained a lake for a long time with a near neutral pH. It was neither acid or alkaline. The lake had water that could support life. On Earth some organisms have evolved to live in an acid environment, but the vast majority of Earth organisms live in liquids with a near neutral pH. Our stomachs secrete strong hydrochloric acid—not just to digest our foods, but the acid kill things that found there way into our stomachs.<ref>https://www.livestrong.com/article/419261-role-of-hydrochloric-acid-in-the-stomach/</ref>

Besides basaltic minerals and their weathered products, Curiosity found what are called more evolved rocks. The minerals in these rocks were formed by various processes underground. These are significant because many of our useful mineral ores we use on Earth are from these more evolved minerals. We will understand much more of the history and deep structure of Mars when we receive data from instruments on the [[InSight Mission]]. It will use a seismometer and a heat probe. It landed in late November 2018 in the Elysium quadrangle.
What follows are some of the studies that came from Curiosity’s probes of rocks.
On October 17, 2012, at Rocknest (Mars), the first X-ray crystallography and of Martian soil was performed. The outcomes of this test revealed the presence of feldspar, pyroxenes and olivine. Martian soil was like the weathered basaltic soils of Hawaii Volcanoes. The sample was composed of dust distributed from Martian dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.<ref>https://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html</ref>

[[File:4792 wiens-1pia16192annotated-full2jake.jpg |right|thumb|320px|”Jake Matijevic rock, the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on Curiosity It is alkaline and relatively fractionated; hence, it is different than most other rocks on Mars. On Earth we get many valuable minerals from fractionated rocks. Marks show where instruments analyzed it.]]

In the journal ''Science'' from September 2013, researchers explained a different type of rock called "Jake M (rock)" or "Jake Matijevic (rock),” It was the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the ''Curiosity'' rover, and was different from other known Martian igneous rocks as it is alkaline (>15% normative nepheline) and relatively fractionated. Fractionated rocks form as magma cools in large magma chambers. In those chambers some minerals float to the surface; others sink due to a higher density. Jake M is similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. Jake M's discovery may mean that alkaline magmas may be more common on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).<ref>Stolper, E.; et al. (2013). "The Petrochemistry of Jake M: A Martian Mugearite" (PDF). Science (Submitted manuscript). 341 (6153): 6153. https://authors.library.caltech.edu/41547/ </ref>
French and U.S. scientists found a type of granite after studying images and chemical results of 22 rock fragments. The composition of the rocks was resolved with the ChemCam instrument. These pale rocks are rich in feldspar and may contain some quartz. The rocks are similar to Earth's granitic continental crust. On Earth these kinds of rocks form deep underground and are later exposed by erosion. By landing in Gale crater, Curiosity was able to sample a variety of rocks because the crater dug deep into the crust, thus exposing old rocks, some of which may be about 3.6 billion years old. For many years, Mars was thought to be composed of only the dark, igneous rock basalt, so this is a significant discovery.<ref>http://spaceref.com/mars/evidence-of-mars-primitive-continental-crust.html</ref> <ref>https://www.sciencedaily.com/releases/2015/07/150714142051.htm</ref> <ref> Sautter, V.; Toplis, M.; Wiens, R.; Cousin, A.; Fabre, C.; Gasnault, O.; Maurice, S.; Forni, O.; Lasue, J.; Ollila, A.; Bridges, J.; Mangold, N.; Le Mouélic, S.; Fisk, M.; Meslin, P.-Y.; Beck, P.; Pinet, P.; Le Deit, L.; Rapin, W.; Stolper, E.; Newsom, H.; Dyar, D.; Lanza, N.; Vaniman, D.; Clegg, S.; Wray, J. (2015). "In situ evidence for continental crust on early Mars" (PDF). Nature Geoscience. 8 (8): 605–609.</ref>
As of 2018, Curiosity's CheMin has discovered discovered olivine, pyroxene, feldspar, quartz, magnetite, iron sulfides (pyrite)and pyrrhotite), akaganeite, jarosite, and calcium sulfates (gypsum, anhydrite, basanite) <ref>Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>

===Life was possible in Gale Crater===

The aim of the Curiosity Rover was not to find alien life, but it was able to find things that could lead us to believe that life may have been possible in Gale Crater <ref> https://solarsystem.nasa.gov/missions/curiosity-msl/in-depth/</ref> Of course, a major case for life would have been to find evidence of past water. Finding out that the water could have a suitable pH is another big plus. Our rover did indeed find evidence for the right kind of water in the past. Various chemicals we think our necessary for life and for the development of life. Curiosity has found many of these as well. Many theories about the origin of life involve clay minerals. Clay particles are thin and flat; hence, they have a high surface area. Chemicals can attach to clay particles and react with other chemicals that are also stuck on the surface of the clay. Curiosity has found clay.
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide.<ref>https://www.jpl.nasa.gov/news/news.php?release=2013-092</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref>

[[File:5073 pia16726-full2john.jpg |left|thumb|320px| Drill hole that went into rock called “John Klein.” Chemicals detected in this sample showed that this spot was suitable for microbial life. ]]

Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals.<ref>https://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1446</ref> <ref>https://www.space.com/20187-ancient-mars-life-curiosity-faq.html</ref> <ref>https://www.nytimes.com/2013/03/13/science/space/mars-could-have-supported-life-nasa-says.html</ref>
Some samples were probably once mud that for millions to tens of millions of years could have hosted living organisms. This wet environment had neutral pH, low salinity, and variable redox states of both iron and sulfur species.<ref>McLennan, M.; et al. (2013). "Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars" (PDF). Science (Submitted manuscript). 343 (6169): 1244734.</ref> <ref>Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref> <ref>Bibring, J.; et al. (2006). "Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data". Science. 312 (5772): 400–404.</ref> <ref>Squyres, S.; A. Knoll. (2005). "Sedimentary rocks and Meridiani Planum: Origin, diagenesis, and implications for life of Mars". Earth Planet. Sci. Lett. 240 (1): 1–10.</ref>These types of iron and sulfur could have been used by living organisms.<ref>Nealson, K.; P. Conrad. (1999). "Life: past, present and future". Phil. Trans. R. Soc. Lond. B. 354: 1923–1939.</ref>
Some clays presented a relative young age (Late Noachian/Early Hesperian or younger age); consequently, in this location neutral pH lasted longer than previously thought. Finding clay minerals is significant because to be created they need a near neutral pH and the water needs to be around for a good length of time.<ref> Vaniman, D.; et al. (2013). "Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars" (PDF). Science. 343 (6169): 1243480.</ref>
CheMin found feldspar, mafic igneous minerals, iron oxides, crystalline silica, phyllosilicates, sulfate minerals in mudstone of Gale Crater. Some of the trends in these minerals at different levels suggested that at least part of the time the lake had near-neutral pH.<ref>Bristow T. F. et al. 2015 Am. Min., 100.</ref> <ref>Rampe, E., et al. 2017. MINERAL TRENDS IN EARLY HESPERIAN LACUSTRINE MUDSTONE AT GALE CRATER, MARS. Lunar and Planetary Science XLVIII (2017). 2821pdf</ref> This finding of more evidence that the lake in Gale Crater probably had a neutral pH gives much support to life thriving there.
On March 24, 2015, a paper was released describing the discovery of nitrates in three samples analyzed by Curiosity. The nitrates are believed to have been created from diatomic nitrogen in the atmosphere during meteorite impacts.<ref>https://www.sciencedaily.com/releases/2015/03/150325082341.htm</ref> <ref> Stern, J.; Sutter, B.; Freissinet, C.; Navarro-González, R.; McKay, C.; Archer, P.; Buch, A.; Brunner, A.; Coll, P.; Eigenbrode, J.; Fairen, A.; Franz, H.; Glavin, D.; Kashyap, S.; McAdam, A.; Ming, D.; Steele, A.; Szopa, C.; Wray, J.; Martín-Torres, F.; Zorzano, Maria-Paz; Conrad, P.; Mahaffy, P. (2015). "Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars". Proceedings of the National Academy of Sciences. 112 (14): 4245–4250.</ref> Nitrogen is necessary for all forms of life because it is used in the building blocks of larger molecules like proteins, DNA, and RNA. Nitrates contain nitrogen in a manner that can be used by living organisms; nitrogen in the air cannot be used by organisms. This discovery of nitrates adds to the evidence that Mars once could have had life.<ref>http://astrobiology.com/2015/03/curiosity-rover-finds-biologically-useful-nitrogen-on-mars.html</ref> <ref>https://www.space.com/28899-mars-life-nitrogen-carbon-monoxide.html?adbid=10152715032851466&adbpl=fb&adbpr=17610706465</ref>
Researchers in December 2016 announced the discovery of the element boron by Curiosity in mineral veins. For boron to be present there must have been a temperature between 0–60 degrees Celsius and a neutral-to-alkaline pH. The temperature, pH, and dissolved minerals of the groundwater support a habitable environment. So, boron is a marker for an environment conducive for life.<ref>http://spaceref.com/mars/first-detection-of-boron-on-the-surface-of-mars.html</ref>
Of great significance is that boron has been suggested to be necessary for life to form. Its presence stabilizes the sugar ribose which is an ingredient in RNA.<ref>http://adsabs.harvard.edu/abs/2013PLoSO...864624S</ref> <ref>Kim HJ, Benner SA (2010). ""Comment on "The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates". Science. 20 (329): 5994.</ref> <ref>Ricardo, A.; Carrigan, M.A.; Olcott, A.N.; Benner, S.A. (2004). "Borate minerals stabilize ribose". Science. 303 (5655): 196.</ref> Specifics of the discovery of Boron on Mars were described in a paper written by a large number of researchers and published in Geophysical Research Letters.<ref>Gasda, P., et al. 2017. In situ detection of boron by ChemCam on Mars. Geophysical Research Letters. DOI: 10.1002/2017GL074480</ref> <ref>https://www.dailymail.co.uk/sciencetech/article-4855658/Breakthrough-hunt-life-Mars.html</ref> <ref>https://www.sciencedaily.com/releases/2017/09/170905123226.htm</ref> <ref>Gasda, Patrick J.; Haldeman, Ethan B.; Wiens, Roger C.; Rapin, William; Bristow, Thomas F.; Bridges, John C.; Schwenzer, Susanne P.; Clark, Benton; Herkenhoff, Kenneth; Frydenvang, Jens; Lanza, Nina L.; Maurice, Sylvestre; Clegg, Samuel; Delapp, Dorothea M.; Sanford, Veronica L.; Bodine, Madeleine R.; McInroy, Rhonda (2017). "In situ detection of boron by ChemCam on Mars". Geophysical Research Letters. 44 (17): 8739–8748.</ref>
By 2018, researchers had concluded that Gale Crater has experienced many episodes of groundwater. As this was going on the chemistry of the groundwater changed. These chemical changes were the kind that would support life.<ref>Schwenzer, S. P.; et al. (2016). "Fluids during diagenesis and sulfate vein formation in sediments at Gale Crater, Mars". Meteorit. Planet. Sci. 51 (11): 2175–2202.</ref> <ref>L'Haridon, J., N. Mangold, W. Rapin, O. Forni, P.-Y. Meslin, E. Dehouck, M. Nachon, L. Le Deit, O. Gasnault, S. Maurice, R. Wiens. 2017. Identification and implications of iron detection within calcium sulfate mineralized veins by ChemCam at Gale crater, Mars, paper presented at 48th Lunar and Planetary Science Conference, The Woodlands, Tex., Abstract 1328.</ref> <ref>Lanza, N. L.; et al. (2016). "Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater". Geophys. Res. Lett. 43 (14): 7398–7407.</ref> <ref>Yen, A. S.; et al. (2017). "Multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in Gale Crater, Mars". Earth Planet. Sci. Lett. 471: 186–198.</ref>

<gallery class="center" widths="190px" heights="180px" >
File:Wikimudcracksdense.jpg|Mud cracks appearing as a network of ridges, as seen by Curiosity Rover.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:8415 MSL-Curiosity-Discolored-Fracture-Zones-in-Martian-Sandstone-PIA21649-full2.jpg|Silica-rich halos Geologists maintain that the silica in the halos went from older to younger young with the aid of groundwater. Scientists concluded that groundwater must have been present for a long time here.<ref>https://www.lanl.gov/discover/news-release-archive/2017/May/0530-halos-discovered-on-mars.php?source=newsroom</ref> <ref>https://mars.nasa.gov/news/high-silica-halos-shed-light-on-wet-ancient-mars/</ref>
Halopicture4.jpg|Fractures that went through both Murray mudstone and Stimson sandstone layers had silica deposited in them (shown in left drawing). After erosion removed most of Stimson layer, halos were found around the fractures by the Curiosity Rover. Because the Stimson was formed after the lake disappeared, water must have been in the ground for a long time after the lake dried up.
</gallery>

===Flower-like Concretion===

In the spring of 2022, pictures were circulated of a small feature imaged in Gale Crater by Curiosity that resembled a fossil.<ref>https://mars.nasa.gov/raw_images/1029787/?site=msl</ref> It was a type of concretion. That is it is a mineral formation that formed by minerals precipitating from water. Water going through the ground dissolves minerals. These minerals can then be deposited around a nucleus. The resulting structure will be harder than the ground around it. When erosion removes the softer ground, the structure (called a concretion) will remain.<ref> https://scitechdaily.com/curiosity-rover-finds-a-bizarre-rock-on-mars-that-looks-like-a-flower/</ref>

<gallery class="center" widths="380px" heights="360px">

File:Curiosityblackthorn.jpg|Concretions discovered by Curiosity in Gale Crater. the one that looks like a flower is called "Blackthorn."

</gallery>

=== Carbon 12===

[[File:CuriosityjpegPIA23974.width-1440.jpg|600pxr|One place where Curiosity measured Carbon 12 levels suggestive of life]]

One place where Curiosity measured Carbon 12 levels suggestive of life

Evidence of life on Mars was published on January 19, 2022. The study was carried out with measurements made by the Curiosity Rover which is exploring Gale Crater. Rover’s Tunable Laser Spectrometer (TLS) determined the abundance of carbon Isotopes in 24 samples. In many of the samples the relative amount of carbon 12 compared to carbon 13 suggested organisms altered the relative amounts of the isotopes. Living things incorporate more carbon 12 than carbon 13 in organic compounds. If we find more carbon 12 than expected, organisms may be the cause. Some of the results are what one would see in Australia from 2.7 billion year old sediment. The carbon 12 there was produced when methane was consumed by mats of microorganisms.<ref> https://www.sciencedaily.com/releases/2022/01/220117165551.htm</ref>

Each atom of carbon in the universe contains 6 particles, called protons. However, carbon atoms can contain different numbers of other particles, called neutrons. Most carbon contains 6 neutrons, but a certain percentage contain 7 or 8. Carbon 12 has 6 protons and 6 neutrons—that is the one mostly used by organisms. Many have heard of carbon 14. It does not exist very long and is used in dating things from the past.

Carbon 12 and carbon 13 are both stable, that is they do not change as time passes. On the other hand, carbon-14 is unstable and changes over precise periods of time. It has a half-life of 5,730 ± 40 years, so it is measured to date things. In 5,730 years half of it changes to nitrogen by throwing off an electron (Beta particle.) And then in 5,730 years another half changes to nitrogen.<ref>Godwin, H. 1962. Half-life of radiocarbon. Nature|volume=195|issue=4845|page=984|doi=10.1038/195984a0</ref> And this process continues until all the carbon is gone.<ref>http://www.nosams.whoi.edu/about/carbon_dating.html |title=What is carbon dating? |publisher=National Ocean Sciences Accelerator Mass Spectrometry Facility |uurl=https://web.archive.org/web/20070705182336/http://www.nosams.whoi.edu/about/carbon_dating.html</ref> Most of the carbon-14 on Earth comes from the action of cosmic rays on nitrogen in the atmosphere. But some has come from the nuclear tests between 1955 and 1980.

The samples that showed lower levels of carbon 13 then expected (maybe because of biology) were found in five locations over a nine year span, from August 2012 to July 2021. They include the Yellowknife Bay, Bagnold dunes, and Vera Rubin ridge (VRR). These different locations include a variety of materials--mudstone, sand, and sandstone.<ref> https://www.pnas.org/content/119/4/e2115651119</ref> <ref>House, C., et al. 2022. Depleted carbon isotope compositions observed at Gale crater, Mars. PNAS. January 25, 2022 119 (4) e2115651119</ref>

Although life could have produced the observed carbon ratios, other possibilities exist. Mars may have passed through a giant cloud containing an excess of carbon 12. Furthermore, the cloud could have lowered the temperature on Mars and caused the lighter carbon to settle on Mars glaciers. Our solar system passes through these clouds about every few hundred million years.<ref> https://www.youtube.com/watch?v=qEH6BxVDbDU</ref> <ref> https://www.nasa.gov/feature/goddard/2022/nasa-s-curiosity-rover-measures-intriguing-carbon-signature-on-mars</ref>
Another possible mechanism is that ultraviolet light (UV) could have reacted with carbon dioxide in the Martian air to produce organic compounds.
The third possibility is organisms creating methane that is enriched in carbon 12. The methane, a gas, would be converted to organic compounds in the air by UV, and then land on the ground.
This study suggests the existence of life on Mars, but it would nice to find some complex organic molecules like proteins, fats, enzymes, or nucleic acids (DNA, RNA) that are closely associated with living process, but none have so far been found. Also, small items that look like fossils would be the icing on the cake to scientists.

=== Meteorites===

Using date gathered with Mastcam, a team of researchers found what they believe to be iron meteorites. These meteorites stand out in multispectral observations as not having the usual ferrous or ferric absorption features as the surrounding surface.<ref>Wellington, D., et al. 2018. IRON METEORITE CANDIDATES WITHIN GALE CRATER, MARS, FROM MSL/MASTCAM MULTISPECTRAL OBSERVATIONS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1832.pdf</ref> One would expect to find many meteorites on the Martian surface because of billions of years of bombardment by asteroids of various sizes. Both the [[Spirit]] and [[Opportunity]] rovers on Mars found meteorites.<ref> Schröder C. et al. 2008. JGR, 113, E06S22, 10.1029/2007JE002990</ref> <ref>Ashley J. W. 2009. LPS XL, Abstract #2468.</ref> <ref> Ashley J. W. 2011. JGR, 116, E00F20, 10.1029/2010JE003672</ref> <ref>Arvidson R. E. et al. 2011. JGR, 116, E00F15, 10.1029/2010JE003746.</ref> <ref> Meslin P.-Y. et al. 2017. LPS XLVII, Abstract #2258</ref> <ref> Ashley J. W. and Herkenhoff K. E. 2017. LPS XLVII, Abstract #2656</ref> Meteoritic material may be very important for future colonists on the Red Planet. We may invent robotic machines to go out and collect and process iron meteorites.

<gallery class="center" widths="190px" heights="180px">
File:8149 msl-rover-curiosity-finds-meteorite-mars-pia21134-full2.jpg|Gray, golf ball-sized iron-nickel meteorite Type of meteorite was determined with laser pulses. Light lines are mineral veins. Meteorite was named “Egg Rock.”
File:8148 mars-meteor-egg-rock-pia21133-full2.jpg|Close view of Egg Rock The small white spots are where the laser hit it. Analysis with laser data showed it was an iron-nickel meteorite.
</gallery>

===Astronomy Observations===

<gallery class="center" widths="190px" heights="180px" >
File:5536 PIA17356 transit trio-full2eclipse.jpg|Eclipse of the sun by the Mars moon Phobos
File:6314 PIA18389 mercury transit-full2.jpg|Sunspots and the planet Mercury passing in front of sun
File:6205 PIA17937-MAIN ceres annotated1-full2.jpg|Planets, moons stars, asteroids, as seen by Curiosity
File:5970 PIA17936-MAIN-evening star annotated-full2.jpg|Earth and Moon, as seen from Mars by Curiosity
</gallery>

[[File:MSL TraverseMap Sol1996-br2.jpg |600px| Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.]]

Journey of Curiosity through March 22, 2018 Numbering of the dots along the line indicate the sol number of each drive. A sol is a Martian day—a little longer than an Earth day.

===Regolith for greenhouses===

The Martian [[regolith]] resembles basaltic soil from Hawaii.<ref>[http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html NASA Rover's First Soil Studies Help Fingerprint Martian Minerals ]</ref>

Conclusion: The regolith is a good base for making [[soil]] for [[greenhouse]]s in the Martian [[colony]].

===Future===

Since Curiosity is powered by radioactive isotopes, rather than solar panels, it may be exploring Mars for many, many years. About the only major potential problem in sight are the wheels. Fairly early on in the mission, it was noticed that the wheels had been punctured by sharp rocks. When driving over certain surfaces, Curiosity’s wheels were being pierced by sharp rocks sticking up. These rocks from hell were probably part of the underlying rock formation; as such they did not give, even when the one ton rover passed over them.<ref > Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> The wheels have parts that are very thin—those are the ones being affected by sharp rocks. Still, the people in charge of driving the rover are being very careful.

==Curiosity Trivia==

Bobak Ferdowsi, a young man in the control room for Curiosity, became popular with ladies after they saw him at his computer during the landing. He had a prominent Mohawk and received hundreds of marriage proposals via Twitter.<ref>Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.</ref> <ref>http://mix957gr.com/bobak-ferdowsi-becomes-internet-sensation-by-landing-mars-rover-hunk-of-the-day/?fbclid=IwAR2oHoYbXNsLnqJ-pstmEfeoD54v9MttJk3n5tXJ6EhwAnI5-O-yyzVb9mk</ref> <ref>https://www.facebook.com/StarTrekMovie/videos/10153724131948716/</ref>

==References==

{{reflist|colwidth=30em}}

==See Also==
*[[Oceans on Mars]]
*[[Rivers on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.

*Lakdawalla, E. 2018. The Design and Engineering of Curiosity: How the Mars Rover Performs its job. Springer Praxis Publishing. Chichester, UK </ref>
*Pyle, R. 2014. Curiosity. Prometheus Books. Amherst, N.Y.

== External links ==
*[ https://www.youtube.com/watch?v=LAL4F6IWC-Y Full Video of Curiosity Landing on Mars]
*[ https://www.youtube.com/watch?v=zqhK8dA7iO8 Five Years of Curiosity on Mars (public talk)]
*[ https://www.youtube.com/watch?v=3Z9zgMOjdPE The Curiosity Rover's Most Amazing Discoveries]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLanding.pdf Press kit for Curiosity]
*[ https://www.jpl.nasa.gov/news/press_kits/MSLLaunch.pdf Press Kit for Mars Science Laboratory launch]
*[https://www.youtube.com/watch?v=aTv6XPJKNBM Mars Global Surveyor Shows landing sites on a rotating globe]

*[https://www.jpl.nasa.gov/news/news.php?feature=7330&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190208-1 360 Video: Curiosity Rover Departs Vera Rubin Ridge]

[[category:Robotic Exploration]]

InSight Mission

2022-12-23T22:24:21Z

Suitupandshowup: /* Mission Discoveries */

NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) made a soft landing as planned on November 26, 2018 at 4.502 °N, 135.623 °E. InSight landed in a crater that is 25 meters in diameter Homestead hollow. This crater is filed with sediments from impacts. The sediments have been modified and transported by wind.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

It is the first space robotic explorer to study the inside of Mars: its crust, mantle, and core. It set down at exactly 2:52:59 p.m. EST. We found out about the landing by way of two small experimental Mars Cube One (MarCO) CubeSats. They were launched on the same rocket as InSight and relayed information from the lander. <ref>https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight</ref>
The launch took place with an Atlas V-401 from Vandenberg Air Force Base, California on May 5, 2018 7:05 a.m. ET. It’s main instruments are a seismometer (SEIS), a heat probe, and a radio science instrument (RISE).<ref>https://mars.nasa.gov/insight/spacecraft/instruments/summary/</ref>

See the [[Interior of Mars]] for more information of Mars' structure.

Artist’s conception of Insight lander sitting on Mars with instruments deployed

[[File:PIA22878b-annotatedinsightlanding.jpg |600pxr|Location of Insight]]

The red dot shows where InSight landed. It landed just about in the center of its landing ellipse. The location is in the Elysium quadrangle at about 4.5 N and 135.6 E (224.4 W).

==Spacecraft==

InSight weighs 794 pounds (360 kilograms). It is 19 feet 8 inches (6 meters) with solar panels deployed ("wingspan"), and its deck is 5 feet 1 inch (1.56 meters) in diameter.<ref>https://mars.nasa.gov/insight/spacecraft/about-the-lander/</ref> Since dust covering solar panels is a persistent problem for Mars missions, the solar panels on InSight are about two times larger than necessary.

[[File:ESP 058005 1845-lander-full-res.jpg |right|thumb|320px|InSight sitting on the surface, as seen by HiRISE]]

==Mission Activities==

December 19, 2018, InSight's seismometer was set onto the ground directly in front of the lander, about as far away as the arm can reach ---- 5.367 feet. Principal Investigator Bruce Banerdt, stated "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives." The seismometer allows scientists to peer into the Martian interior by studying ground motion — also known as marsquakes. Each marsquake acts as a kind of flashbulb that illuminates the structure of the planet's interior. By studying how seismic waves pass through the layers of the planet, scientists can deduce the depth and composition of these layers.<ref>https://mars.nasa.gov/news/8402/nasas-insight-places-first-instrument-on-mars/?site=insight</ref> InSight's seismometer is so sensitive that if Mars had an atmosphere, and a butterfly landed on the seismometer it's vibrations would be detected. It can detect ground motion that is only half the width of a hydrogen atom.

[[File:22280 PIA22959windshield.jpg|left|thumb|320px|InSights's seismometer with wind cover on the Martian surface.]]

[[File:PIA23045 hiresmole.jpg|right|thumb|320px|Parts of "mole" that will drill into Mars and take its temperature at different points]]

On February 13, 2019, NASA announced that the InSight lander has placed its second instrument on the Martian surface. New images confirm that the Heat Flow and Physical Properties Package, or HP3, was successfully deployed on Feb. 12 about 3 feet (1 meter) from InSight's seismometer. HP3 measures heat moving through Mars' subsurface.
Equipped with a self-hammering spike, mole, the instrument will burrow up to 16 feet (5 meters) below the surface, deeper than any previous mission to the Red Planet. This compares to, the Viking 1 lander which went down 8.6 inches (22 centimeters). While the Phoenix lander dug down 7 inches (18 centimeters).

HP3 looks a bit like an automobile jack but with a vertical metal tube up front to hold the 16-inch-long (40-centimeter-long) mole. A tether connects HP3's support structure to the lander, while a tether attached to the top of the mole features heat sensors to measure the temperature of the Martian subsurface. Meanwhile, heat sensors in the mole itself will measure the soil's thermal conductivity, that is how easily heat moves through the subsurface.

The mole will stop every 19 inches (50 centimeters) to take a thermal conductivity measurement of the soil. Because hammering creates friction and releases heat, the mole is first allowed to cool down for a good two days. Then it will be heated up by about 50 degrees Fahrenheit (10 degrees Celsius) over 24 hours. Temperature sensors within the mole measure how rapidly this happens, which tells scientists the conductivity of the soil.
If the mole encounters a large rock before reaching at least 10 feet (3 meters) down, the team will need a full Martian year (two Earth years) to filter noise out of their data. This is one reason the team carefully selected a landing site with few rocks and why it spent weeks picking where to place the instrument.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7335&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190213-4</ref>

In May 2021, the InSight team boasted the power output of the solar cells with a novel method. By using the scoop to drop sand grains on the panels, they raised the power by 30 watt-hours. When there was maximum wind, they caused sand to fall and then bounce along on the solar panels. The larger grains carried off the smaller dust particles in the wind. A big drawback to using solar panels on Mars is that they get covered with dust. However, sometimes we get lucky because passing dust devils clean the panels.<ref>https://www.jpl.nasa.gov/news/nasas-insight-mars-lander-gets-a-power-boost?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20210603-3</ref>

==Mission Discoveries==

InSight's seismometer recorded its first marsquake on April 6, 2019, and its largest seismic signal to date at 7:23 p.m. PDT (10:23 EDT) on May 22, 2019. That last event is believed to be a marsquake of magnitude 3.0.<ref>https://outlook.live.com/mail/inbox/id/AQMkADAwATExAGNiNy00YzQ1LTM4MjMtMDACLTAwCgBGAAADdsmEa%2FgtIEmBK%2FX8yb671wcAkr%2FaXi2mwEKimhNbcs0ITQAAAgEMAAAAkr%2FaXi2mwEKimhNbcs0ITQACxRb2xwAAAA%3D%3D</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> NASA's Mars InSight lander has measured and recorded for the first time ever a likely "marsquake." This is the first recorded vibration that seems to have originated inside Mars. It's greater duration is similar to that of moonquakes detected on the lunar surface during the Apollo missions,"said Lori Glaze, Planetary Science Division director at NASA Headquarters. Sismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> As of October 2019. Insight has found 21 Marsquakes.<ref>https://www.space.com/mars-insight-lander-burrowing-probe-hope.html?utm_source=Selligent&utm_medium=email&utm_campaign=8763&utm_content=20191016_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=pAsrLmboNLkM3OHTeP4JZwcN0DgadelbQged0iUjw8q_smkwBFQbBTBN4arp5CfWSRZEdakPqW36HVks02yDLWEFGsm9W%2Bsppz</ref> <ref>https://www.universetoday.com/143625/insight-has-already-detected-21-marsquakes/</ref>

As summary of Insight's first Martian year of operation reported that there were more than 450 events that appear to be of
tectonic origin. Three events had magnitudes between 3.1 and 3.6 and were at distances between 27.5° and 47°
(±10°) from the lander. They originating in the Cerberus Fossae region.<ref>Panning, M., et al. 2021. RESULTS FROM INSIGHT’S FIRST FULL MARTIAN YEAR. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 1533.pdf</ref>

The marsquakes measured by insight have led scientists to conclude that the three biggest events were from the Cerberus Fossae region. It is located about 1’500 km away. The tectonic graben system at Cerberus Fossae is caused by the great mass of Elysium Mons, a volcano in the Elysium Planitia region. Mars has a total seismic energy between that of the moon and the Earth.<ref>https://ethz.ch/en/news-and-events/eth-news/news/2020/02/seismicity-of-mars.html?fbclid=IwAR0HwOkxqG_QmBNn62TxW8yMKZDDNAtfB2LEIHGZ4zNvIjbGD8wFWZJaI6k</ref> <ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref> <ref>Giardini D et al.: The seismicity of Mars. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0539-8
</ref> <ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref> The top 8–11 km of the crust is highly altered and/or broken.<ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref>
All of the seismic event found so far are of tectonic origins--none were the result of impacts.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

Mars soil is strange--very cohesive. Holes dug on Mars showed no lip; it seems the soil was just pounded into the ground.<ref>https://www.space.com/mars-soil-weird-nasa-insight-lander.html?utm_source=Selligent&utm_medium=email&utm_campaign=9036&utm_content=20191022_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=6BJGMRJ6hO865ajoAYi4Nmpcq_wRcyNG4CEPalniT_t4eiV%2B%2BNyldqilky%2BFCzep%2BIlvwPHsKTQcyrSLTwmD0ToRMHgw5jd669</ref>

[[File:Rollingstonesrock.jpg|right|thumb|320px|Rock that was named "Rolling Stones Rock." One can see the trail the rock moved when InSight landed]]

[[File:Insight marsweather white.png|600pxr|Weather data from Insight]]

Insight has detected dust devils with the weather station.

On 28 February 2019, the Heat and Physical Properties Package probe (HP³) started its drilling into the surface of Mars. The probe and its digging mole were intended to reach a maximum depth of 5 meters (16 ft) about two months after, but on 7 March 2019, the HP³ instrument's mole paused its digging. The mole had only gone down to about 35 cm (14 in)<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref>

At first, it was thought that maybe the mole hit a rock--that would have been hard to deal with. But in October 2019, scientists at JPL concluded that the mole could not go any farther because the soil on Mars does not provide necessary friction for drilling. Hence, the mole bounces around and makes a wide pit around itself instead of digging deeper. However, they devised a manoeuvre called "pinning" in which they press the side of the scoop against the mole to try and pin it to the side of the wall of the hole to increase friction to stop it from moving forward while digging.<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref> NASA reported that the pinning worked.<ref>https://mars.nasa.gov/news/8529/mars-insights-mole-is-moving-again/</ref>

NASA has gave up trying to deploy a heat flow probe in January, 2021. Almost two years of trying different approaches did not work. The team attempted to push down the mole with the scoop on the end of the lander’s robotic arm to prevent it from rebounding. They tried to tamp down regolith around the hole. They filled in the widening hole so the mole could gain more friction, but nothing worked.<ref>https://spacenews.com/nasa-ceases-efforts-to-deploy-mars-insight-heat-flow-probe</ref> <ref>https://www.jpl.nasa.gov/news/nasa-insights-mole-ends-its-journey-on-mars</ref>

On December 16, 2020, NASA reported that InSight had detected more than 480 quakes in a
little more than one Martian year after landing. However, none had greater than a 3.7 magnitude and none exhibited surface waves--only P and S waves. The lack of surface waves could be due to extensive fracturing in the top 6 miles (10 kilometers) below the lander. Or it could also mean that the quakes InSight detected are coming from deep within the planet. Deep quakes do not make strong surface waves.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight</ref>

By March, 2021, Insight had detected about 500 events, according to Philippe Lognonné, principal investigator.<ref>https://www.space.com/insight-mission-mars-core-size-finding?utm_source=Selligent&utm_medium=email&utm_campaign=SDC_Newsletter&utm_content=SDC_Newsletter+&utm_term=2946561</ref>

The timing of the quakes was a bit unusual. Once InSight began hearing quakes, they occurred every day. Then, in late June, quakes stopped. Just five quakes have been detected since then, all of them since September. Experts think Mars' wind is responsible for these seismically blank periods. The time when no quakes were measured was the windiest season of the Martian year. This idea is supported by the fact that it took a while before any quakes were found and that was also a windy time for a regional dust storm was finishing up.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight/</ref>

Journal articles published in July 2021 in the journal Science detailed what has been learned about the Martian interior to date. Its crust is probably 24- to 72-kilometers thick, while its lithosphere is about 500 kilometers thick. Like the Earth, Mars has a low-velocity layer under its lithosphere. The Martian crust is highly enriched (13 to 20 times as much) in radioactive elements that help to heat this layer, but at the expense of the interior. In other words, these heat producing elements lie more in the crust than in the deeper interior. Mars has a large (1830 kilometer) liquid core.<ref>https://science.sciencemag.org/content/373/6553/434</ref> <ref>Khan, A., et al. 2021. Upper mantle structure of Mars from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 434-438
DOI: 10.1126/science.abf2966</ref> <ref>https://www.technologyreview.com/2021/07/23/1030040/we-just-got-our-best-ever-look-at-the-inside-of-mars/</ref> <ref>https://science.sciencemag.org/content/373/6553/438</ref> <ref>Knapmeyer-Endrun, B. et al. 2021. Thickness and structure of the martian crust from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 438-443
DOI: 10.1126/science.abf8966</ref> The core has an average density of 5.7 to 6.3 grams per cubic centimeter. To achieve that density means that a great deal of light elements must be dissolved in an iron-nickel core. The number of Marsquakes that were detected was problably reduced by a large seismic core shadow as seen from InSight’s position on the planet. It would have been difficult to find quakes near Tharsis. Tharsis contains many huge volcanoes, including Olympus Mons. One might expect this region to produce many quakes, but they can not be found by InSight.<ref>https://science.sciencemag.org/content/373/6553/443</ref> <ref>Stahler, S. et al. 2021. Seismic detection of the martian core. Science. Vol. 373, Issue 6553, pp. 443-448
DOI: 10.1126/science.abi7730</ref> Quakes have an area where waves can't pass through; hence, we can't observe earthquakes form that region. To be technical, it is the angular distances of 104 to 140 degrees from a given earthquake. In that area, S waves are being stopped by the liquid core and P waves are being bent or refracted, by the liquid core.<ref>https://earthquake.usgs.gov/learn/glossary/?term=shadow%20zone</ref>

Mission scientists said that one 4.2-magnitude earthquake struck roughly 8,500 kilometers (5,280 miles) from InSight in August. This is much farther than the other quakes.<ref>https://www.sciencetimes.com/articles/33612/20210924/nasa-insight-mars-lander-detects-3-massive-earthquakes-red-planet.htm</ref> Furthermore, it lasted for almost an hour and a half.<ref> https://www.techtimes.com/articles/265793/20210924/nasa-insight-lander-mars-quakes-nasa-insight-lander-mars-quakes-magnitude-4-mars-quake-over-1-hour.htm</ref>

A large research team announced that they had determined details of the Martian the subsurface to about a depth of 200 m. Right beneath the surface is a 3 meter regolith layer of sandy material. Next, there is a 15 meter layer of blocky ejecta that came from past impacts. Under the blocker layer is a basalt lava flow. Between lava flows is a layer of sedimentary material. The upper basalt layer is of Amazonian age--about 1.7 billion years old. The lower basalt layer is of Hesperian age (3.6 billion years old).<ref>https://scitechdaily.com/nasas-mars-insight-lander-uses-wind-induced-vibrations-to-reveal-the-red-planets-subsurface-layers/</ref> <ref> Hobiger, M. et al. 2021. The shallow structure of Mars at the InSight
landing site from inversion of ambient vibrations. NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-26957-7</ref> The researchers used the faint vibrations induced by Martian winds to discover the subsurface structure.<ref> https://www.msn.com/en-us/news/technology/nasa-mars-lander-makes-1st-ever-map-of-red-planet-underground-by-listening-to-winds/ar-AAR3v7Q?ocid=uxbndlbing,</ref>

In an abstract released in February of 2022. researchers described what had been learned from InSight at that time--after almost 1000 Marsquakes had been detected. The crust is 20-35 km thick under insight.<ref> Knapmeyer-Endrun et al.,
Science, 373, 438-443, 2021 </ref> <ref>Kim et al., J. Geo Mantlephy. Res., Planets, in press, 2022</ref> <ref>Compaire et al.
J. Geophy. Res., Planets, 126, e2020JE006498, 2021</ref>
<ref> Schimmel et al. Earth and Space Science, 8,
e2021EA001755, 2021</ref> Seismic velocity was 7.8 Km/sec. The core has a radius of 1830 Km and a density of 6000 Kg/m cubed.<ref> Stähler et al., Science, 373, 443-448,
2021</ref> <ref> Khan et al., EPSL, 578, 2022</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf</ref> <ref>Lognonne, P. et al. 2022. SEIS achievement for Mars Seismology after 1000 sols of seismic monitoring. 53rd Lunar and Planetary Science Conference (2022). 2279.pdf</ref>

[[File:InSights Seismogramm5.png|center|thumb|320px|Magnitude 5 quake, as seen by InSight]]

In May, 2022, NASA announced that InSight detected the largest quake ever detected on Mars; it had an estimated magnitude of 5. This temblor occurred on May 4, 2022, the 1,222nd Martian day. Insight has observed more than 1,313 quakes since landing in November 2018. The largest previously recorded quake was an estimated magnitude 4.2 detected Aug. 25, 2021.<ref>https://www.jpl.nasa.gov/news/nasas-insight-records-monster-quake-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220509-1</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101543</ref> <ref>Kawamura. T., et al. 2022. S1222a - the largest Marsquake detected by InSight. Geophysical Research Letters. doi: 10.1029/2022GL101543</ref>

[[File:Troughs in Elysium Planitia.JPG|600pxr|Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes]]

Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes

Research published in August, 2022 suggested that "uncemented material" largely fills in the region under InSight. That implies that little water is present. Although the ground has much pore space, the pore spaces probably are largely just full of air, rather than ice or other cementing material. It was thought that perhaps there could be ice- or liquid water-saturated layers within the upper 300 m beneath InSight, but this study shows that is not the case. Had there been cement between soil particles, it has likely been broken by impacts or marsquakes. InSight measures the speed of seismic waves within the crust. These velocities change depending on rock type and the material that fills the pores within rocks. Hence, the amount of pore space can be measured. The velocity of these waves would be different going through ice or air.<ref> https://www.msn.com/en-us/news/technology/equatorial-mars-is-surprisingly-dry-nasas-insight-lander-finds/ar-AA10zrBw</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL099250</ref> <ref>Wright, V., et al. 2022. A minimally cemented shallow crust beneath InSight. Geophysical Research Letters. doi: 10.1029/2022GL099250 </ref>

NASA announced on September 19, 2022 that Insight had detected audio and seismic waves from an impact. In other words, they heard the impact.
Researchers calculated where the impact happened, and then found the resulting craters with CTX and HiRISE. The body entered Mars’ atmosphere on Sept. 5, 2021. It then blew apart into at least three pieces. Each of them made a crater. Scientists studied the seismic recordings to see what an impact event looks like. They were then able to discover three other impacts that occurred on May 27, 2020; Feb. 18, 2021; and Aug. 31, 2021. The size of the quakes produced by these impacts was small--no more than magnitude 2.0.<ref>https://www.nature.com/articles/s41561-022-01014-0</ref> <ref>Garcia, R.F., Daubar, I.J., Beucler, É. et al. Newly formed craters on Mars located using seismic and acoustic wave data from InSight. Nat. Geosci. (2022). https://doi.org/10.1038/s41561-022-01014-0</ref> <ref>https://www.jpl.nasa.gov/news/nasas-insight-hears-its-first-meteoroid-impacts-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Daily09192022</ref>

[[File:Insightimpacecrater.jpg|center|thumb|320px|Impact craters that InSight heard and that scientists were are to photograph with HiRISE. the projectile broke apart as it entered the Martian atmosphere.]]

The sound can be heard at https://www.youtube.com/watch?v=439Hg8aAars

[[File:Insightselfydust.jpg|center|thumb|320px|Selfie of Insight as of April, 2022. Since solar panels are almost totally covered with dust, Insight may not last much longer. However it was still going as of October, 2022]]

On October 27, 2022, NASA described a new impact that was seen with orbiting cameras and detected by Insight. This discovery was published in the journal Science.
The impacting body is estimated to have been 16 to 39 feet (5 to 12 meters) across. It would have burned up in Earth’s atmosphere. The crater produced by the impact was larger than a football field and was 70 feet (21 meters) deep. Pieces of ejecta flew as far as 23 miles (37 kilometers) away.

<gallery class="center" widths="380px" heights="360px">
File:Newcraterctxbeforeafter.jpg|Before and after pictures of site where the new crater was formed. Pictures are from CTX.
File:Newcratericesize.jpeg|Close view of new crater, as seen by HiRISE. Sizes are indicated. White dots are boulder-sized chunks of ice that were blown out by the impact.
</gallery>

The impact happened on December 24, 2021 and was measured to have made a marsquake of magnitude 4 by InSight. This may have been the largest impact that has ever been observed. Chunks of ice that were excavated were the biggest ever found this close to the equator. That's good news for future colonists--maybe ice is more widespread than previously thought.<ref>https://mars.nasa.gov/news/9289/nasas-insight-lander-detects-stunning-meteoroid-impact-on-mars/?s=03&fbclid=IwAR2wjZ6yhSZ1XrU553LOZ8R8jJugkkv79uHMvLkZRqfn03ed_6X8Q-ncj5c</ref>

InSight found that nearly all the Marsquakes originated near Cerberus Fossae. Researchers have discovered that there is a large plume under the area. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). The uplift caused by this plume stretched the crust, cracking it to form Cerberus Fossae. Plumes like this are like the plume under Hawaii.

Besides being the focus of Marsquakes, other forms of evidence for the plume are (1) a rise of a mile above the surroundings, (2) crater floors tilted away from the rise, and (3) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.
The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

On December 21, 2022, NASA declared the mission finished when they were unable to contact the lander after two consecutive attempts.
The solar panels had too much dust on them to function<ref>https://www.jpl.nasa.gov/news/nasa-retires-insight-mars-lander-mission-after-years-of-science?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20221221-3</ref>

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Cerberus Fossae]]

*[[Elysium quadrangle]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Interior of Mars]]
*[[Geography of Mars]]

==Recommended reading==

*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://www.jpl.nasa.gov/missions/insight/ JPL Mission to Mars InSight]

==External links==

*[https://www.youtube.com/watch?v=439Hg8aAars NASA's InSight hears its first meteoroid impacts on Mars]

*[https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight Mars InSight Mission]
*[https://www.youtube.com/watch?v=bGD_YF64Nwk Mission Control Live: NASA InSight Mars Landing]
*[https://www.youtube.com/watch?v=lGwM30F4Oao How NASA's Next Mars Mission Will Take the Red Planet's Pulse | Decoder]

*[https://mars.nasa.gov/insight/timeline/surface-operations/ Timeline of Surface Operations]

*[https://usc-marshall-panopto-demo.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=399919d8-faf3-4feb-bdec-aae80114eeb6 / Update on InSight from Mars Society Convention 2019]

*[https://www.youtube.com/watch?v=kca3Y8XUK1c InSight Live Q&A: Journey to the Center of Mars with the Lander Team]

*https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf InSight Seismology after 1000 sols of seismic monitoring

[[Category:Lander Missions]]

InSight Mission

2022-12-23T22:23:30Z

Suitupandshowup: /* Mission Discoveries */ added new info and ref

NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) made a soft landing as planned on November 26, 2018 at 4.502 °N, 135.623 °E. InSight landed in a crater that is 25 meters in diameter Homestead hollow. This crater is filed with sediments from impacts. The sediments have been modified and transported by wind.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

It is the first space robotic explorer to study the inside of Mars: its crust, mantle, and core. It set down at exactly 2:52:59 p.m. EST. We found out about the landing by way of two small experimental Mars Cube One (MarCO) CubeSats. They were launched on the same rocket as InSight and relayed information from the lander. <ref>https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight</ref>
The launch took place with an Atlas V-401 from Vandenberg Air Force Base, California on May 5, 2018 7:05 a.m. ET. It’s main instruments are a seismometer (SEIS), a heat probe, and a radio science instrument (RISE).<ref>https://mars.nasa.gov/insight/spacecraft/instruments/summary/</ref>

See the [[Interior of Mars]] for more information of Mars' structure.

Artist’s conception of Insight lander sitting on Mars with instruments deployed

[[File:PIA22878b-annotatedinsightlanding.jpg |600pxr|Location of Insight]]

The red dot shows where InSight landed. It landed just about in the center of its landing ellipse. The location is in the Elysium quadrangle at about 4.5 N and 135.6 E (224.4 W).

==Spacecraft==

InSight weighs 794 pounds (360 kilograms). It is 19 feet 8 inches (6 meters) with solar panels deployed ("wingspan"), and its deck is 5 feet 1 inch (1.56 meters) in diameter.<ref>https://mars.nasa.gov/insight/spacecraft/about-the-lander/</ref> Since dust covering solar panels is a persistent problem for Mars missions, the solar panels on InSight are about two times larger than necessary.

[[File:ESP 058005 1845-lander-full-res.jpg |right|thumb|320px|InSight sitting on the surface, as seen by HiRISE]]

==Mission Activities==

December 19, 2018, InSight's seismometer was set onto the ground directly in front of the lander, about as far away as the arm can reach ---- 5.367 feet. Principal Investigator Bruce Banerdt, stated "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives." The seismometer allows scientists to peer into the Martian interior by studying ground motion — also known as marsquakes. Each marsquake acts as a kind of flashbulb that illuminates the structure of the planet's interior. By studying how seismic waves pass through the layers of the planet, scientists can deduce the depth and composition of these layers.<ref>https://mars.nasa.gov/news/8402/nasas-insight-places-first-instrument-on-mars/?site=insight</ref> InSight's seismometer is so sensitive that if Mars had an atmosphere, and a butterfly landed on the seismometer it's vibrations would be detected. It can detect ground motion that is only half the width of a hydrogen atom.

[[File:22280 PIA22959windshield.jpg|left|thumb|320px|InSights's seismometer with wind cover on the Martian surface.]]

[[File:PIA23045 hiresmole.jpg|right|thumb|320px|Parts of "mole" that will drill into Mars and take its temperature at different points]]

On February 13, 2019, NASA announced that the InSight lander has placed its second instrument on the Martian surface. New images confirm that the Heat Flow and Physical Properties Package, or HP3, was successfully deployed on Feb. 12 about 3 feet (1 meter) from InSight's seismometer. HP3 measures heat moving through Mars' subsurface.
Equipped with a self-hammering spike, mole, the instrument will burrow up to 16 feet (5 meters) below the surface, deeper than any previous mission to the Red Planet. This compares to, the Viking 1 lander which went down 8.6 inches (22 centimeters). While the Phoenix lander dug down 7 inches (18 centimeters).

HP3 looks a bit like an automobile jack but with a vertical metal tube up front to hold the 16-inch-long (40-centimeter-long) mole. A tether connects HP3's support structure to the lander, while a tether attached to the top of the mole features heat sensors to measure the temperature of the Martian subsurface. Meanwhile, heat sensors in the mole itself will measure the soil's thermal conductivity, that is how easily heat moves through the subsurface.

The mole will stop every 19 inches (50 centimeters) to take a thermal conductivity measurement of the soil. Because hammering creates friction and releases heat, the mole is first allowed to cool down for a good two days. Then it will be heated up by about 50 degrees Fahrenheit (10 degrees Celsius) over 24 hours. Temperature sensors within the mole measure how rapidly this happens, which tells scientists the conductivity of the soil.
If the mole encounters a large rock before reaching at least 10 feet (3 meters) down, the team will need a full Martian year (two Earth years) to filter noise out of their data. This is one reason the team carefully selected a landing site with few rocks and why it spent weeks picking where to place the instrument.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7335&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190213-4</ref>

In May 2021, the InSight team boasted the power output of the solar cells with a novel method. By using the scoop to drop sand grains on the panels, they raised the power by 30 watt-hours. When there was maximum wind, they caused sand to fall and then bounce along on the solar panels. The larger grains carried off the smaller dust particles in the wind. A big drawback to using solar panels on Mars is that they get covered with dust. However, sometimes we get lucky because passing dust devils clean the panels.<ref>https://www.jpl.nasa.gov/news/nasas-insight-mars-lander-gets-a-power-boost?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20210603-3</ref>

==Mission Discoveries==

InSight's seismometer recorded its first marsquake on April 6, 2019, and its largest seismic signal to date at 7:23 p.m. PDT (10:23 EDT) on May 22, 2019. That last event is believed to be a marsquake of magnitude 3.0.<ref>https://outlook.live.com/mail/inbox/id/AQMkADAwATExAGNiNy00YzQ1LTM4MjMtMDACLTAwCgBGAAADdsmEa%2FgtIEmBK%2FX8yb671wcAkr%2FaXi2mwEKimhNbcs0ITQAAAgEMAAAAkr%2FaXi2mwEKimhNbcs0ITQACxRb2xwAAAA%3D%3D</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> NASA's Mars InSight lander has measured and recorded for the first time ever a likely "marsquake." This is the first recorded vibration that seems to have originated inside Mars. It's greater duration is similar to that of moonquakes detected on the lunar surface during the Apollo missions,"said Lori Glaze, Planetary Science Division director at NASA Headquarters. Sismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> As of October 2019. Insight has found 21 Marsquakes.<ref>https://www.space.com/mars-insight-lander-burrowing-probe-hope.html?utm_source=Selligent&utm_medium=email&utm_campaign=8763&utm_content=20191016_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=pAsrLmboNLkM3OHTeP4JZwcN0DgadelbQged0iUjw8q_smkwBFQbBTBN4arp5CfWSRZEdakPqW36HVks02yDLWEFGsm9W%2Bsppz</ref> <ref>https://www.universetoday.com/143625/insight-has-already-detected-21-marsquakes/</ref>

As summary of Insight's first Martian year of operation reported that there were more than 450 events that appear to be of
tectonic origin. Three events had magnitudes between 3.1 and 3.6 and were at distances between 27.5° and 47°
(±10°) from the lander. They originating in the Cerberus Fossae region.<ref>Panning, M., et al. 2021. RESULTS FROM INSIGHT’S FIRST FULL MARTIAN YEAR. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 1533.pdf</ref>

The marsquakes measured by insight have led scientists to conclude that the three biggest events were from the Cerberus Fossae region. It is located about 1’500 km away. The tectonic graben system at Cerberus Fossae is caused by the great mass of Elysium Mons, a volcano in the Elysium Planitia region. Mars has a total seismic energy between that of the moon and the Earth.<ref>https://ethz.ch/en/news-and-events/eth-news/news/2020/02/seismicity-of-mars.html?fbclid=IwAR0HwOkxqG_QmBNn62TxW8yMKZDDNAtfB2LEIHGZ4zNvIjbGD8wFWZJaI6k</ref> <ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref> <ref>Giardini D et al.: The seismicity of Mars. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0539-8
</ref> <ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref> The top 8–11 km of the crust is highly altered and/or broken.<ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref>
All of the seismic event found so far are of tectonic origins--none were the result of impacts.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

Mars soil is strange--very cohesive. Holes dug on Mars showed no lip; it seems the soil was just pounded into the ground.<ref>https://www.space.com/mars-soil-weird-nasa-insight-lander.html?utm_source=Selligent&utm_medium=email&utm_campaign=9036&utm_content=20191022_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=6BJGMRJ6hO865ajoAYi4Nmpcq_wRcyNG4CEPalniT_t4eiV%2B%2BNyldqilky%2BFCzep%2BIlvwPHsKTQcyrSLTwmD0ToRMHgw5jd669</ref>

[[File:Rollingstonesrock.jpg|right|thumb|320px|Rock that was named "Rolling Stones Rock." One can see the trail the rock moved when InSight landed]]

[[File:Insight marsweather white.png|600pxr|Weather data from Insight]]

Insight has detected dust devils with the weather station.

On 28 February 2019, the Heat and Physical Properties Package probe (HP³) started its drilling into the surface of Mars. The probe and its digging mole were intended to reach a maximum depth of 5 meters (16 ft) about two months after, but on 7 March 2019, the HP³ instrument's mole paused its digging. The mole had only gone down to about 35 cm (14 in)<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref>

At first, it was thought that maybe the mole hit a rock--that would have been hard to deal with. But in October 2019, scientists at JPL concluded that the mole could not go any farther because the soil on Mars does not provide necessary friction for drilling. Hence, the mole bounces around and makes a wide pit around itself instead of digging deeper. However, they devised a manoeuvre called "pinning" in which they press the side of the scoop against the mole to try and pin it to the side of the wall of the hole to increase friction to stop it from moving forward while digging.<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref> NASA reported that the pinning worked.<ref>https://mars.nasa.gov/news/8529/mars-insights-mole-is-moving-again/</ref>

NASA has gave up trying to deploy a heat flow probe in January, 2021. Almost two years of trying different approaches did not work. The team attempted to push down the mole with the scoop on the end of the lander’s robotic arm to prevent it from rebounding. They tried to tamp down regolith around the hole. They filled in the widening hole so the mole could gain more friction, but nothing worked.<ref>https://spacenews.com/nasa-ceases-efforts-to-deploy-mars-insight-heat-flow-probe</ref> <ref>https://www.jpl.nasa.gov/news/nasa-insights-mole-ends-its-journey-on-mars</ref>

On December 16, 2020, NASA reported that InSight had detected more than 480 quakes in a
little more than one Martian year after landing. However, none had greater than a 3.7 magnitude and none exhibited surface waves--only P and S waves. The lack of surface waves could be due to extensive fracturing in the top 6 miles (10 kilometers) below the lander. Or it could also mean that the quakes InSight detected are coming from deep within the planet. Deep quakes do not make strong surface waves.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight</ref>

By March, 2021, Insight had detected about 500 events, according to Philippe Lognonné, principal investigator.<ref>https://www.space.com/insight-mission-mars-core-size-finding?utm_source=Selligent&utm_medium=email&utm_campaign=SDC_Newsletter&utm_content=SDC_Newsletter+&utm_term=2946561</ref>

The timing of the quakes was a bit unusual. Once InSight began hearing quakes, they occurred every day. Then, in late June, quakes stopped. Just five quakes have been detected since then, all of them since September. Experts think Mars' wind is responsible for these seismically blank periods. The time when no quakes were measured was the windiest season of the Martian year. This idea is supported by the fact that it took a while before any quakes were found and that was also a windy time for a regional dust storm was finishing up.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight/</ref>

Journal articles published in July 2021 in the journal Science detailed what has been learned about the Martian interior to date. Its crust is probably 24- to 72-kilometers thick, while its lithosphere is about 500 kilometers thick. Like the Earth, Mars has a low-velocity layer under its lithosphere. The Martian crust is highly enriched (13 to 20 times as much) in radioactive elements that help to heat this layer, but at the expense of the interior. In other words, these heat producing elements lie more in the crust than in the deeper interior. Mars has a large (1830 kilometer) liquid core.<ref>https://science.sciencemag.org/content/373/6553/434</ref> <ref>Khan, A., et al. 2021. Upper mantle structure of Mars from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 434-438
DOI: 10.1126/science.abf2966</ref> <ref>https://www.technologyreview.com/2021/07/23/1030040/we-just-got-our-best-ever-look-at-the-inside-of-mars/</ref> <ref>https://science.sciencemag.org/content/373/6553/438</ref> <ref>Knapmeyer-Endrun, B. et al. 2021. Thickness and structure of the martian crust from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 438-443
DOI: 10.1126/science.abf8966</ref> The core has an average density of 5.7 to 6.3 grams per cubic centimeter. To achieve that density means that a great deal of light elements must be dissolved in an iron-nickel core. The number of Marsquakes that were detected was problably reduced by a large seismic core shadow as seen from InSight’s position on the planet. It would have been difficult to find quakes near Tharsis. Tharsis contains many huge volcanoes, including Olympus Mons. One might expect this region to produce many quakes, but they can not be found by InSight.<ref>https://science.sciencemag.org/content/373/6553/443</ref> <ref>Stahler, S. et al. 2021. Seismic detection of the martian core. Science. Vol. 373, Issue 6553, pp. 443-448
DOI: 10.1126/science.abi7730</ref> Quakes have an area where waves can't pass through; hence, we can't observe earthquakes form that region. To be technical, it is the angular distances of 104 to 140 degrees from a given earthquake. In that area, S waves are being stopped by the liquid core and P waves are being bent or refracted, by the liquid core.<ref>https://earthquake.usgs.gov/learn/glossary/?term=shadow%20zone</ref>

Mission scientists said that one 4.2-magnitude earthquake struck roughly 8,500 kilometers (5,280 miles) from InSight in August. This is much farther than the other quakes.<ref>https://www.sciencetimes.com/articles/33612/20210924/nasa-insight-mars-lander-detects-3-massive-earthquakes-red-planet.htm</ref> Furthermore, it lasted for almost an hour and a half.<ref> https://www.techtimes.com/articles/265793/20210924/nasa-insight-lander-mars-quakes-nasa-insight-lander-mars-quakes-magnitude-4-mars-quake-over-1-hour.htm</ref>

A large research team announced that they had determined details of the Martian the subsurface to about a depth of 200 m. Right beneath the surface is a 3 meter regolith layer of sandy material. Next, there is a 15 meter layer of blocky ejecta that came from past impacts. Under the blocker layer is a basalt lava flow. Between lava flows is a layer of sedimentary material. The upper basalt layer is of Amazonian age--about 1.7 billion years old. The lower basalt layer is of Hesperian age (3.6 billion years old).<ref>https://scitechdaily.com/nasas-mars-insight-lander-uses-wind-induced-vibrations-to-reveal-the-red-planets-subsurface-layers/</ref> <ref> Hobiger, M. et al. 2021. The shallow structure of Mars at the InSight
landing site from inversion of ambient vibrations. NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-26957-7</ref> The researchers used the faint vibrations induced by Martian winds to discover the subsurface structure.<ref> https://www.msn.com/en-us/news/technology/nasa-mars-lander-makes-1st-ever-map-of-red-planet-underground-by-listening-to-winds/ar-AAR3v7Q?ocid=uxbndlbing,</ref>

In an abstract released in February of 2022. researchers described what had been learned from InSight at that time--after almost 1000 Marsquakes had been detected. The crust is 20-35 km thick under insight.<ref> Knapmeyer-Endrun et al.,
Science, 373, 438-443, 2021 </ref> <ref>Kim et al., J. Geo Mantlephy. Res., Planets, in press, 2022</ref> <ref>Compaire et al.
J. Geophy. Res., Planets, 126, e2020JE006498, 2021</ref>
<ref> Schimmel et al. Earth and Space Science, 8,
e2021EA001755, 2021</ref> Seismic velocity was 7.8 Km/sec. The core has a radius of 1830 Km and a density of 6000 Kg/m cubed.<ref> Stähler et al., Science, 373, 443-448,
2021</ref> <ref> Khan et al., EPSL, 578, 2022</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf</ref> <ref>Lognonne, P. et al. 2022. SEIS achievement for Mars Seismology after 1000 sols of seismic monitoring. 53rd Lunar and Planetary Science Conference (2022). 2279.pdf</ref>

[[File:InSights Seismogramm5.png|center|thumb|320px|Magnitude 5 quake, as seen by InSight]]

In May, 2022, NASA announced that InSight detected the largest quake ever detected on Mars; it had an estimated magnitude of 5. This temblor occurred on May 4, 2022, the 1,222nd Martian day. Insight has observed more than 1,313 quakes since landing in November 2018. The largest previously recorded quake was an estimated magnitude 4.2 detected Aug. 25, 2021.<ref>https://www.jpl.nasa.gov/news/nasas-insight-records-monster-quake-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220509-1</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101543</ref> <ref>Kawamura. T., et al. 2022. S1222a - the largest Marsquake detected by InSight. Geophysical Research Letters. doi: 10.1029/2022GL101543</ref>

[[File:Troughs in Elysium Planitia.JPG|600pxr|Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes]]

Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes

Research published in August, 2022 suggested that "uncemented material" largely fills in the region under InSight. That implies that little water is present. Although the ground has much pore space, the pore spaces probably are largely just full of air, rather than ice or other cementing material. It was thought that perhaps there could be ice- or liquid water-saturated layers within the upper 300 m beneath InSight, but this study shows that is not the case. Had there been cement between soil particles, it has likely been broken by impacts or marsquakes. InSight measures the speed of seismic waves within the crust. These velocities change depending on rock type and the material that fills the pores within rocks. Hence, the amount of pore space can be measured. The velocity of these waves would be different going through ice or air.<ref> https://www.msn.com/en-us/news/technology/equatorial-mars-is-surprisingly-dry-nasas-insight-lander-finds/ar-AA10zrBw</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL099250</ref> <ref>Wright, V., et al. 2022. A minimally cemented shallow crust beneath InSight. Geophysical Research Letters. doi: 10.1029/2022GL099250 </ref>

NASA announced on September 19, 2022 that Insight had detected audio and seismic waves from an impact. In other words, they heard the impact.
Researchers calculated where the impact happened, and then found the resulting craters with CTX and HiRISE. The body entered Mars’ atmosphere on Sept. 5, 2021. It then blew apart into at least three pieces. Each of them made a crater. Scientists studied the seismic recordings to see what an impact event looks like. They were then able to discover three other impacts that occurred on May 27, 2020; Feb. 18, 2021; and Aug. 31, 2021. The size of the quakes produced by these impacts was small--no more than magnitude 2.0.<ref>https://www.nature.com/articles/s41561-022-01014-0</ref> <ref>Garcia, R.F., Daubar, I.J., Beucler, É. et al. Newly formed craters on Mars located using seismic and acoustic wave data from InSight. Nat. Geosci. (2022). https://doi.org/10.1038/s41561-022-01014-0</ref> <ref>https://www.jpl.nasa.gov/news/nasas-insight-hears-its-first-meteoroid-impacts-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Daily09192022</ref>

[[File:Insightimpacecrater.jpg|center|thumb|320px|Impact craters that InSight heard and that scientists were are to photograph with HiRISE. the projectile broke apart as it entered the Martian atmosphere.]]

The sound can be heard at https://www.youtube.com/watch?v=439Hg8aAars

[[File:Insightselfydust.jpg|center|thumb|320px|Selfie of Insight as of April, 2022. Since solar panels are almost totally covered with dust, Insight may not last much longer. However it was still going as of October, 2022]]

On October 27, 2022, NASA described a new impact that was seen with orbiting cameras and detected by Insight. This discovery was published in the journal Science.
The impacting body is estimated to have been 16 to 39 feet (5 to 12 meters) across. It would have burned up in Earth’s atmosphere. The crater produced by the impact was larger than a football field and was 70 feet (21 meters) deep. Pieces of ejecta flew as far as 23 miles (37 kilometers) away.

<gallery class="center" widths="380px" heights="360px">
File:Newcraterctxbeforeafter.jpg|Before and after pictures of site where the new crater was formed. Pictures are from CTX.
File:Newcratericesize.jpeg|Close view of new crater, as seen by HiRISE. Sizes are indicated. White dots are boulder-sized chunks of ice that were blown out by the impact.
</gallery>

The impact happened on December 24, 2021 and was measured to have made a marsquake of magnitude 4 by InSight. This may have been the largest impact that has ever been observed. Chunks of ice that were excavated were the biggest ever found this close to the equator. That's good news for future colonists--maybe ice is more widespread than previously thought.<ref>https://mars.nasa.gov/news/9289/nasas-insight-lander-detects-stunning-meteoroid-impact-on-mars/?s=03&fbclid=IwAR2wjZ6yhSZ1XrU553LOZ8R8jJugkkv79uHMvLkZRqfn03ed_6X8Q-ncj5c</ref>

InSight found that nearly all the Marsquakes originated near Cerberus Fossae. Researchers have discovered that there is a large plume under the area. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). The uplift caused by this plume stretched the crust, cracking it to form Cerberus Fossae. Plumes like this are like the plume under Hawaii.

Besides being the focus of Marsquakes, other forms of evidence for the plume are (1) a rise of a mile above the surroundings, (2) crater floors tilted away from the rise, and (3) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.
The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

On December 21, 2022, NASA declared the mission finished when they were unable to contact the lander after two consecutive attempts.
The solar panels had too much dust on them to function<ref>https://www.jpl.nasa.gov/news/nasa-retires-insight-mars-lander-mission-after-years-of-science?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20221221-3</ref> leading them to conclude the spacecraft’s solar-powered batteries have run out of energy – a state engineers refer to as “dead bus.”

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Cerberus Fossae]]

*[[Elysium quadrangle]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Interior of Mars]]
*[[Geography of Mars]]

==Recommended reading==

*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://www.jpl.nasa.gov/missions/insight/ JPL Mission to Mars InSight]

==External links==

*[https://www.youtube.com/watch?v=439Hg8aAars NASA's InSight hears its first meteoroid impacts on Mars]

*[https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight Mars InSight Mission]
*[https://www.youtube.com/watch?v=bGD_YF64Nwk Mission Control Live: NASA InSight Mars Landing]
*[https://www.youtube.com/watch?v=lGwM30F4Oao How NASA's Next Mars Mission Will Take the Red Planet's Pulse | Decoder]

*[https://mars.nasa.gov/insight/timeline/surface-operations/ Timeline of Surface Operations]

*[https://usc-marshall-panopto-demo.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=399919d8-faf3-4feb-bdec-aae80114eeb6 / Update on InSight from Mars Society Convention 2019]

*[https://www.youtube.com/watch?v=kca3Y8XUK1c InSight Live Q&A: Journey to the Center of Mars with the Lander Team]

*https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf InSight Seismology after 1000 sols of seismic monitoring

[[Category:Lander Missions]]

InSight Mission

2022-12-20T22:08:39Z

Suitupandshowup: /* Mission Discoveries */ added ref

NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) made a soft landing as planned on November 26, 2018 at 4.502 °N, 135.623 °E. InSight landed in a crater that is 25 meters in diameter Homestead hollow. This crater is filed with sediments from impacts. The sediments have been modified and transported by wind.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

It is the first space robotic explorer to study the inside of Mars: its crust, mantle, and core. It set down at exactly 2:52:59 p.m. EST. We found out about the landing by way of two small experimental Mars Cube One (MarCO) CubeSats. They were launched on the same rocket as InSight and relayed information from the lander. <ref>https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight</ref>
The launch took place with an Atlas V-401 from Vandenberg Air Force Base, California on May 5, 2018 7:05 a.m. ET. It’s main instruments are a seismometer (SEIS), a heat probe, and a radio science instrument (RISE).<ref>https://mars.nasa.gov/insight/spacecraft/instruments/summary/</ref>

See the [[Interior of Mars]] for more information of Mars' structure.

Artist’s conception of Insight lander sitting on Mars with instruments deployed

[[File:PIA22878b-annotatedinsightlanding.jpg |600pxr|Location of Insight]]

The red dot shows where InSight landed. It landed just about in the center of its landing ellipse. The location is in the Elysium quadrangle at about 4.5 N and 135.6 E (224.4 W).

==Spacecraft==

InSight weighs 794 pounds (360 kilograms). It is 19 feet 8 inches (6 meters) with solar panels deployed ("wingspan"), and its deck is 5 feet 1 inch (1.56 meters) in diameter.<ref>https://mars.nasa.gov/insight/spacecraft/about-the-lander/</ref> Since dust covering solar panels is a persistent problem for Mars missions, the solar panels on InSight are about two times larger than necessary.

[[File:ESP 058005 1845-lander-full-res.jpg |right|thumb|320px|InSight sitting on the surface, as seen by HiRISE]]

==Mission Activities==

December 19, 2018, InSight's seismometer was set onto the ground directly in front of the lander, about as far away as the arm can reach ---- 5.367 feet. Principal Investigator Bruce Banerdt, stated "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives." The seismometer allows scientists to peer into the Martian interior by studying ground motion — also known as marsquakes. Each marsquake acts as a kind of flashbulb that illuminates the structure of the planet's interior. By studying how seismic waves pass through the layers of the planet, scientists can deduce the depth and composition of these layers.<ref>https://mars.nasa.gov/news/8402/nasas-insight-places-first-instrument-on-mars/?site=insight</ref> InSight's seismometer is so sensitive that if Mars had an atmosphere, and a butterfly landed on the seismometer it's vibrations would be detected. It can detect ground motion that is only half the width of a hydrogen atom.

[[File:22280 PIA22959windshield.jpg|left|thumb|320px|InSights's seismometer with wind cover on the Martian surface.]]

[[File:PIA23045 hiresmole.jpg|right|thumb|320px|Parts of "mole" that will drill into Mars and take its temperature at different points]]

On February 13, 2019, NASA announced that the InSight lander has placed its second instrument on the Martian surface. New images confirm that the Heat Flow and Physical Properties Package, or HP3, was successfully deployed on Feb. 12 about 3 feet (1 meter) from InSight's seismometer. HP3 measures heat moving through Mars' subsurface.
Equipped with a self-hammering spike, mole, the instrument will burrow up to 16 feet (5 meters) below the surface, deeper than any previous mission to the Red Planet. This compares to, the Viking 1 lander which went down 8.6 inches (22 centimeters). While the Phoenix lander dug down 7 inches (18 centimeters).

HP3 looks a bit like an automobile jack but with a vertical metal tube up front to hold the 16-inch-long (40-centimeter-long) mole. A tether connects HP3's support structure to the lander, while a tether attached to the top of the mole features heat sensors to measure the temperature of the Martian subsurface. Meanwhile, heat sensors in the mole itself will measure the soil's thermal conductivity, that is how easily heat moves through the subsurface.

The mole will stop every 19 inches (50 centimeters) to take a thermal conductivity measurement of the soil. Because hammering creates friction and releases heat, the mole is first allowed to cool down for a good two days. Then it will be heated up by about 50 degrees Fahrenheit (10 degrees Celsius) over 24 hours. Temperature sensors within the mole measure how rapidly this happens, which tells scientists the conductivity of the soil.
If the mole encounters a large rock before reaching at least 10 feet (3 meters) down, the team will need a full Martian year (two Earth years) to filter noise out of their data. This is one reason the team carefully selected a landing site with few rocks and why it spent weeks picking where to place the instrument.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7335&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190213-4</ref>

In May 2021, the InSight team boasted the power output of the solar cells with a novel method. By using the scoop to drop sand grains on the panels, they raised the power by 30 watt-hours. When there was maximum wind, they caused sand to fall and then bounce along on the solar panels. The larger grains carried off the smaller dust particles in the wind. A big drawback to using solar panels on Mars is that they get covered with dust. However, sometimes we get lucky because passing dust devils clean the panels.<ref>https://www.jpl.nasa.gov/news/nasas-insight-mars-lander-gets-a-power-boost?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20210603-3</ref>

==Mission Discoveries==

InSight's seismometer recorded its first marsquake on April 6, 2019, and its largest seismic signal to date at 7:23 p.m. PDT (10:23 EDT) on May 22, 2019. That last event is believed to be a marsquake of magnitude 3.0.<ref>https://outlook.live.com/mail/inbox/id/AQMkADAwATExAGNiNy00YzQ1LTM4MjMtMDACLTAwCgBGAAADdsmEa%2FgtIEmBK%2FX8yb671wcAkr%2FaXi2mwEKimhNbcs0ITQAAAgEMAAAAkr%2FaXi2mwEKimhNbcs0ITQACxRb2xwAAAA%3D%3D</ref> <ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> NASA's Mars InSight lander has measured and recorded for the first time ever a likely "marsquake." This is the first recorded vibration that seems to have originated inside Mars. It's greater duration is similar to that of moonquakes detected on the lunar surface during the Apollo missions,"said Lori Glaze, Planetary Science Division director at NASA Headquarters. Sismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon.<ref>https://www.jpl.nasa.gov/news/news.php?feature=7383&utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily-20190605-1</ref> As of October 2019. Insight has found 21 Marsquakes.<ref>https://www.space.com/mars-insight-lander-burrowing-probe-hope.html?utm_source=Selligent&utm_medium=email&utm_campaign=8763&utm_content=20191016_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=pAsrLmboNLkM3OHTeP4JZwcN0DgadelbQged0iUjw8q_smkwBFQbBTBN4arp5CfWSRZEdakPqW36HVks02yDLWEFGsm9W%2Bsppz</ref> <ref>https://www.universetoday.com/143625/insight-has-already-detected-21-marsquakes/</ref>

As summary of Insight's first Martian year of operation reported that there were more than 450 events that appear to be of
tectonic origin. Three events had magnitudes between 3.1 and 3.6 and were at distances between 27.5° and 47°
(±10°) from the lander. They originating in the Cerberus Fossae region.<ref>Panning, M., et al. 2021. RESULTS FROM INSIGHT’S FIRST FULL MARTIAN YEAR. 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548). 1533.pdf</ref>

The marsquakes measured by insight have led scientists to conclude that the three biggest events were from the Cerberus Fossae region. It is located about 1’500 km away. The tectonic graben system at Cerberus Fossae is caused by the great mass of Elysium Mons, a volcano in the Elysium Planitia region. Mars has a total seismic energy between that of the moon and the Earth.<ref>https://ethz.ch/en/news-and-events/eth-news/news/2020/02/seismicity-of-mars.html?fbclid=IwAR0HwOkxqG_QmBNn62TxW8yMKZDDNAtfB2LEIHGZ4zNvIjbGD8wFWZJaI6k</ref> <ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref> <ref>Giardini D et al.: The seismicity of Mars. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0539-8
</ref> <ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref> The top 8–11 km of the crust is highly altered and/or broken.<ref>Lognonné P et al.: Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0536-y</ref>
All of the seismic event found so far are of tectonic origins--none were the result of impacts.<ref>Banerdt B et al.: Initial results from the InSight mission on Mars, Nature Geoscience, 24 February 2020, doi: 10.1038/s41561-020-0544-y</ref>

Mars soil is strange--very cohesive. Holes dug on Mars showed no lip; it seems the soil was just pounded into the ground.<ref>https://www.space.com/mars-soil-weird-nasa-insight-lander.html?utm_source=Selligent&utm_medium=email&utm_campaign=9036&utm_content=20191022_SDC_Newsletter+-+adhoc+&utm_term=2946561&m_i=6BJGMRJ6hO865ajoAYi4Nmpcq_wRcyNG4CEPalniT_t4eiV%2B%2BNyldqilky%2BFCzep%2BIlvwPHsKTQcyrSLTwmD0ToRMHgw5jd669</ref>

[[File:Rollingstonesrock.jpg|right|thumb|320px|Rock that was named "Rolling Stones Rock." One can see the trail the rock moved when InSight landed]]

[[File:Insight marsweather white.png|600pxr|Weather data from Insight]]

Insight has detected dust devils with the weather station.

On 28 February 2019, the Heat and Physical Properties Package probe (HP³) started its drilling into the surface of Mars. The probe and its digging mole were intended to reach a maximum depth of 5 meters (16 ft) about two months after, but on 7 March 2019, the HP³ instrument's mole paused its digging. The mole had only gone down to about 35 cm (14 in)<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref>

At first, it was thought that maybe the mole hit a rock--that would have been hard to deal with. But in October 2019, scientists at JPL concluded that the mole could not go any farther because the soil on Mars does not provide necessary friction for drilling. Hence, the mole bounces around and makes a wide pit around itself instead of digging deeper. However, they devised a manoeuvre called "pinning" in which they press the side of the scoop against the mole to try and pin it to the side of the wall of the hole to increase friction to stop it from moving forward while digging.<ref>[https://www.jpl.nasa.gov/news/news.php?feature=7511] Jet Propulsion Lab, NASA. 3 October 2019.</ref> NASA reported that the pinning worked.<ref>https://mars.nasa.gov/news/8529/mars-insights-mole-is-moving-again/</ref>

NASA has gave up trying to deploy a heat flow probe in January, 2021. Almost two years of trying different approaches did not work. The team attempted to push down the mole with the scoop on the end of the lander’s robotic arm to prevent it from rebounding. They tried to tamp down regolith around the hole. They filled in the widening hole so the mole could gain more friction, but nothing worked.<ref>https://spacenews.com/nasa-ceases-efforts-to-deploy-mars-insight-heat-flow-probe</ref> <ref>https://www.jpl.nasa.gov/news/nasa-insights-mole-ends-its-journey-on-mars</ref>

On December 16, 2020, NASA reported that InSight had detected more than 480 quakes in a
little more than one Martian year after landing. However, none had greater than a 3.7 magnitude and none exhibited surface waves--only P and S waves. The lack of surface waves could be due to extensive fracturing in the top 6 miles (10 kilometers) below the lander. Or it could also mean that the quakes InSight detected are coming from deep within the planet. Deep quakes do not make strong surface waves.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight</ref>

By March, 2021, Insight had detected about 500 events, according to Philippe Lognonné, principal investigator.<ref>https://www.space.com/insight-mission-mars-core-size-finding?utm_source=Selligent&utm_medium=email&utm_campaign=SDC_Newsletter&utm_content=SDC_Newsletter+&utm_term=2946561</ref>

The timing of the quakes was a bit unusual. Once InSight began hearing quakes, they occurred every day. Then, in late June, quakes stopped. Just five quakes have been detected since then, all of them since September. Experts think Mars' wind is responsible for these seismically blank periods. The time when no quakes were measured was the windiest season of the Martian year. This idea is supported by the fact that it took a while before any quakes were found and that was also a windy time for a regional dust storm was finishing up.<ref>https://mars.nasa.gov/news/8817/3-things-weve-learned-from-nasas-mars-insight/</ref>

Journal articles published in July 2021 in the journal Science detailed what has been learned about the Martian interior to date. Its crust is probably 24- to 72-kilometers thick, while its lithosphere is about 500 kilometers thick. Like the Earth, Mars has a low-velocity layer under its lithosphere. The Martian crust is highly enriched (13 to 20 times as much) in radioactive elements that help to heat this layer, but at the expense of the interior. In other words, these heat producing elements lie more in the crust than in the deeper interior. Mars has a large (1830 kilometer) liquid core.<ref>https://science.sciencemag.org/content/373/6553/434</ref> <ref>Khan, A., et al. 2021. Upper mantle structure of Mars from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 434-438
DOI: 10.1126/science.abf2966</ref> <ref>https://www.technologyreview.com/2021/07/23/1030040/we-just-got-our-best-ever-look-at-the-inside-of-mars/</ref> <ref>https://science.sciencemag.org/content/373/6553/438</ref> <ref>Knapmeyer-Endrun, B. et al. 2021. Thickness and structure of the martian crust from InSight seismic data. Science. Vol. 373, Issue 6553, pp. 438-443
DOI: 10.1126/science.abf8966</ref> The core has an average density of 5.7 to 6.3 grams per cubic centimeter. To achieve that density means that a great deal of light elements must be dissolved in an iron-nickel core. The number of Marsquakes that were detected was problably reduced by a large seismic core shadow as seen from InSight’s position on the planet. It would have been difficult to find quakes near Tharsis. Tharsis contains many huge volcanoes, including Olympus Mons. One might expect this region to produce many quakes, but they can not be found by InSight.<ref>https://science.sciencemag.org/content/373/6553/443</ref> <ref>Stahler, S. et al. 2021. Seismic detection of the martian core. Science. Vol. 373, Issue 6553, pp. 443-448
DOI: 10.1126/science.abi7730</ref> Quakes have an area where waves can't pass through; hence, we can't observe earthquakes form that region. To be technical, it is the angular distances of 104 to 140 degrees from a given earthquake. In that area, S waves are being stopped by the liquid core and P waves are being bent or refracted, by the liquid core.<ref>https://earthquake.usgs.gov/learn/glossary/?term=shadow%20zone</ref>

Mission scientists said that one 4.2-magnitude earthquake struck roughly 8,500 kilometers (5,280 miles) from InSight in August. This is much farther than the other quakes.<ref>https://www.sciencetimes.com/articles/33612/20210924/nasa-insight-mars-lander-detects-3-massive-earthquakes-red-planet.htm</ref> Furthermore, it lasted for almost an hour and a half.<ref> https://www.techtimes.com/articles/265793/20210924/nasa-insight-lander-mars-quakes-nasa-insight-lander-mars-quakes-magnitude-4-mars-quake-over-1-hour.htm</ref>

A large research team announced that they had determined details of the Martian the subsurface to about a depth of 200 m. Right beneath the surface is a 3 meter regolith layer of sandy material. Next, there is a 15 meter layer of blocky ejecta that came from past impacts. Under the blocker layer is a basalt lava flow. Between lava flows is a layer of sedimentary material. The upper basalt layer is of Amazonian age--about 1.7 billion years old. The lower basalt layer is of Hesperian age (3.6 billion years old).<ref>https://scitechdaily.com/nasas-mars-insight-lander-uses-wind-induced-vibrations-to-reveal-the-red-planets-subsurface-layers/</ref> <ref> Hobiger, M. et al. 2021. The shallow structure of Mars at the InSight
landing site from inversion of ambient vibrations. NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-26957-7</ref> The researchers used the faint vibrations induced by Martian winds to discover the subsurface structure.<ref> https://www.msn.com/en-us/news/technology/nasa-mars-lander-makes-1st-ever-map-of-red-planet-underground-by-listening-to-winds/ar-AAR3v7Q?ocid=uxbndlbing,</ref>

In an abstract released in February of 2022. researchers described what had been learned from InSight at that time--after almost 1000 Marsquakes had been detected. The crust is 20-35 km thick under insight.<ref> Knapmeyer-Endrun et al.,
Science, 373, 438-443, 2021 </ref> <ref>Kim et al., J. Geo Mantlephy. Res., Planets, in press, 2022</ref> <ref>Compaire et al.
J. Geophy. Res., Planets, 126, e2020JE006498, 2021</ref>
<ref> Schimmel et al. Earth and Space Science, 8,
e2021EA001755, 2021</ref> Seismic velocity was 7.8 Km/sec. The core has a radius of 1830 Km and a density of 6000 Kg/m cubed.<ref> Stähler et al., Science, 373, 443-448,
2021</ref> <ref> Khan et al., EPSL, 578, 2022</ref> <ref>https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf</ref> <ref>Lognonne, P. et al. 2022. SEIS achievement for Mars Seismology after 1000 sols of seismic monitoring. 53rd Lunar and Planetary Science Conference (2022). 2279.pdf</ref>

[[File:InSights Seismogramm5.png|center|thumb|320px|Magnitude 5 quake, as seen by InSight]]

In May, 2022, NASA announced that InSight detected the largest quake ever detected on Mars; it had an estimated magnitude of 5. This temblor occurred on May 4, 2022, the 1,222nd Martian day. Insight has observed more than 1,313 quakes since landing in November 2018. The largest previously recorded quake was an estimated magnitude 4.2 detected Aug. 25, 2021.<ref>https://www.jpl.nasa.gov/news/nasas-insight-records-monster-quake-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=daily20220509-1</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL101543</ref> <ref>Kawamura. T., et al. 2022. S1222a - the largest Marsquake detected by InSight. Geophysical Research Letters. doi: 10.1029/2022GL101543</ref>

[[File:Troughs in Elysium Planitia.JPG|600pxr|Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes]]

Types of troughs in Cerberus Fossae near where InSight has detected Marsquakes

Research published in August, 2022 suggested that "uncemented material" largely fills in the region under InSight. That implies that little water is present. Although the ground has much pore space, the pore spaces probably are largely just full of air, rather than ice or other cementing material. It was thought that perhaps there could be ice- or liquid water-saturated layers within the upper 300 m beneath InSight, but this study shows that is not the case. Had there been cement between soil particles, it has likely been broken by impacts or marsquakes. InSight measures the speed of seismic waves within the crust. These velocities change depending on rock type and the material that fills the pores within rocks. Hence, the amount of pore space can be measured. The velocity of these waves would be different going through ice or air.<ref> https://www.msn.com/en-us/news/technology/equatorial-mars-is-surprisingly-dry-nasas-insight-lander-finds/ar-AA10zrBw</ref> <ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL099250</ref> <ref>Wright, V., et al. 2022. A minimally cemented shallow crust beneath InSight. Geophysical Research Letters. doi: 10.1029/2022GL099250 </ref>

NASA announced on September 19, 2022 that Insight had detected audio and seismic waves from an impact. In other words, they heard the impact.
Researchers calculated where the impact happened, and then found the resulting craters with CTX and HiRISE. The body entered Mars’ atmosphere on Sept. 5, 2021. It then blew apart into at least three pieces. Each of them made a crater. Scientists studied the seismic recordings to see what an impact event looks like. They were then able to discover three other impacts that occurred on May 27, 2020; Feb. 18, 2021; and Aug. 31, 2021. The size of the quakes produced by these impacts was small--no more than magnitude 2.0.<ref>https://www.nature.com/articles/s41561-022-01014-0</ref> <ref>Garcia, R.F., Daubar, I.J., Beucler, É. et al. Newly formed craters on Mars located using seismic and acoustic wave data from InSight. Nat. Geosci. (2022). https://doi.org/10.1038/s41561-022-01014-0</ref> <ref>https://www.jpl.nasa.gov/news/nasas-insight-hears-its-first-meteoroid-impacts-on-mars?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Daily09192022</ref>

[[File:Insightimpacecrater.jpg|center|thumb|320px|Impact craters that InSight heard and that scientists were are to photograph with HiRISE. the projectile broke apart as it entered the Martian atmosphere.]]

The sound can be heard at https://www.youtube.com/watch?v=439Hg8aAars

[[File:Insightselfydust.jpg|center|thumb|320px|Selfie of Insight as of April, 2022. Since solar panels are almost totally covered with dust, Insight may not last much longer. However it was still going as of October, 2022]]

On October 27, 2022, NASA described a new impact that was seen with orbiting cameras and detected by Insight. This discovery was published in the journal Science.
The impacting body is estimated to have been 16 to 39 feet (5 to 12 meters) across. It would have burned up in Earth’s atmosphere. The crater produced by the impact was larger than a football field and was 70 feet (21 meters) deep. Pieces of ejecta flew as far as 23 miles (37 kilometers) away.

<gallery class="center" widths="380px" heights="360px">
File:Newcraterctxbeforeafter.jpg|Before and after pictures of site where the new crater was formed. Pictures are from CTX.
File:Newcratericesize.jpeg|Close view of new crater, as seen by HiRISE. Sizes are indicated. White dots are boulder-sized chunks of ice that were blown out by the impact.
</gallery>

The impact happened on December 24, 2021 and was measured to have made a marsquake of magnitude 4 by InSight. This may have been the largest impact that has ever been observed. Chunks of ice that were excavated were the biggest ever found this close to the equator. That's good news for future colonists--maybe ice is more widespread than previously thought.<ref>https://mars.nasa.gov/news/9289/nasas-insight-lander-detects-stunning-meteoroid-impact-on-mars/?s=03&fbclid=IwAR2wjZ6yhSZ1XrU553LOZ8R8jJugkkv79uHMvLkZRqfn03ed_6X8Q-ncj5c</ref>

InSight found that nearly all the Marsquakes originated near Cerberus Fossae. Researchers have discovered that there is a large plume under the area. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). The uplift caused by this plume stretched the crust, cracking it to form Cerberus Fossae. Plumes like this are like the plume under Hawaii.

Besides being the focus of Marsquakes, other forms of evidence for the plume are (1) a rise of a mile above the surroundings, (2) crater floors tilted away from the rise, and (3) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.
The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

==References==
{{reflist|colwidth=30em}}

==See Also==

*[[Cerberus Fossae]]

*[[Elysium quadrangle]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Interior of Mars]]
*[[Geography of Mars]]

==Recommended reading==

*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://www.jpl.nasa.gov/missions/insight/ JPL Mission to Mars InSight]

==External links==

*[https://www.youtube.com/watch?v=439Hg8aAars NASA's InSight hears its first meteoroid impacts on Mars]

*[https://mars.nasa.gov/news/8392/nasa-insight-lander-arrives-on-martian-surface/?site=insight Mars InSight Mission]
*[https://www.youtube.com/watch?v=bGD_YF64Nwk Mission Control Live: NASA InSight Mars Landing]
*[https://www.youtube.com/watch?v=lGwM30F4Oao How NASA's Next Mars Mission Will Take the Red Planet's Pulse | Decoder]

*[https://mars.nasa.gov/insight/timeline/surface-operations/ Timeline of Surface Operations]

*[https://usc-marshall-panopto-demo.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=399919d8-faf3-4feb-bdec-aae80114eeb6 / Update on InSight from Mars Society Convention 2019]

*[https://www.youtube.com/watch?v=kca3Y8XUK1c InSight Live Q&A: Journey to the Center of Mars with the Lander Team]

*https://www.hou.usra.edu/meetings/lpsc2022/pdf/2279.pdf InSight Seismology after 1000 sols of seismic monitoring

[[Category:Lander Missions]]

Geological processes that have shaped Mars: Why Mars looks like it does

2022-12-09T17:23:24Z

Suitupandshowup: /* Igneous effects */ added new info and ref

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:Mars, Earth size comparison.jpg|left|thumb|px|Earth and Mars Earth is much bigger, but both have the same land area. Mars has about one third the gravity of the Earth.]]

Mars looks like it does because of certain geological processes. Some of them are common to both the Earth and Mars. However, others are rare or nonexistent on the Earth. Mars shows an extremely old record of the past that is lacking on the Earth. Plate tectonics and vigorous air and water erosion has wiped out nearly all of the past geology of the Earth. In contrast, much of the Martian surface is billions of years old. Another factor that has affected the appearance of Mars is its extreme cold. The coldness of the planet makes carbon dioxide significant. It has influenced Mars both as a gas and as a solid. As a greenhouse gas, early in the history of the planet, it may have been thick enough in the atmosphere to help raise the temperature enough to permit water to flow, to carve rivers, to form lakes and an ocean. Indeed, it may have been warm enough from carbon dioxide for life to first originate on Mars and then travel to the Earth on meteorites. Today, as a solid, carbon dioxide (dry ice) produces the ubiquitous gullies found in numerous areas of the planet.

==Erosion Related==

As on the Earth material was laid down and then later eroded. Many spectacular scenes are present with places that were mostly eroded, but with remnants remaining in the form of buttes and mesas. Sometimes, sediments were put down in layers. As a result beautiful places were created. On the Earth we admire such layers in Monument Valley and many beautiful canyons. The same types of landscapes show up on Mars.
The top layer of buttes and mesas is hard and resistant to erosion. It protects the lower layers from being eroded away. On Mars that hard, cap rock could be made from a lava flow. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area.

<gallery class="center" widths="380px" heights="360px">

File:16 21 2117 monument valley.jpg|Spearhead Mesa in Monument Valley Note the flat top and steep walls that are characteristic of mesas.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it.

File:58563 2225mesa.jpg|Mesa

File:45016 2080mesas.jpg|Mesas, as seen by HiRISE under HiWish program These are like the ones in Monument Valley

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte: Buttes have a much smaller area than mesas, but both have a hard cap rock on the top. Box shows the size of a football field.

</gallery>

As on the Earth, there are landslides. However, they could be a little different since Mars has only about a third of Earth’s gravity.

<gallery class="center" widths="380px" heights="360px">

File:ESP 043963 1550landslide.jpg|Landslide

</gallery>

Common features in certain areas of the Earth’s surface are “Yardangs.” They are found in desert areas which contain much sand. The wind blows sand and shapes the relatively soft grained deposits into the long, boat shapes of yardangs. On Mars it is thought that these forms are the result of the weathering of huge ash deposits from volcanoes. Mars has the biggest known volcanoes in the solar system. Many probably threw out much fine-grained material which was easily eroded to make vast fields of yardangs. Regions called the “Medusa Fossae Formation and Electris deposits contain thousands of yardangs.

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs.jpg|Yardangs
</gallery>

Unlike the Earth, Mars shows landscapes that are billions of years old. In that time material has been deposited and then eroded and/or greatly changed. Some features have been “inverted.” Low areas turned into high areas. Low areas like stream beds were filled with erosion-resistant materials like lava and large rocks. Later, the surrounding, softer ground became eroded. As a result, the old stream bed now appears raised. We can tell it was originally a stream bed since the overall shape from above still looks like a stream with curves and branches.

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Inverted streams Here a branched stream became filled with hard material and then the surrounding ground was eroded.]]

Another structure made with erosion is a “pedestal crater.” They are abundant in regions far from the equator. These craters seem to sit on little circular shelves or pedestals.<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> In the impacting process, ejecta fell about the crater and protected the underlying ground from erosion. These craters occur where we think there was a great deal of ice in the ground. So, much of the material that disappeared was just ice. With that being said, pedestal craters give us an indication of how much ice was in the region. In some places hundreds of meters of ice-rich ground were removed to make pedestal craters.<ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

[[File:ESP 037528 2350pedestal.jpg |thumb|left|px||Pedestal crater Surface close to crater was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

[[Image:Pedestal crater3.jpg |thumb|right|px||Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings]]

[[File:Pedestaldrawingcolor2.jpg|thumb|600px|center|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

Some structures on Mars are being “exhumed.” Craters are observed that are being uncovered. In the past, impacts produced craters. Later, they were buried. Now they are in the process of being uncovered by erosion. When an asteroid strikes the surface it generates a hole and throws out ejecta all around it. A circular hole is the result. If we see a half of a crater, we know that that it is being exposed by erosion. Impacts do not produce half holes!

<gallery class="center" widths="380px" heights="360px">

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]
</gallery>

==Craters==

Impact craters occur on both the Earth and Mars. However, due to the extreme age of the Martian surface, most of Mars shows a high density of impact craters especially in the southern hemisphere. Craters do not last long on the Earth. Remember, the Earth experiences a great deal more erosion due to its thick atmosphere and abundant water. And, at intervals, the crust is taken into the Earth at plate boundaries. We know a fair amount about impact craters because the Earth has impact craters like Meteor Crater in Arizona that we can study easily.

<gallery class="center" widths="380px" heights="360px">

File:Barringer Crater USGS.jpg|Meteor Crater in Arizona
</gallery>

We know that a new crater will have a rim and ejecta around it. Large ones may have a central uplift and maybe a ring around the middle of the floor. We know that the impact brings up material from deep underground.<ref>https://www.uahirise.org/hipod/PSP_007464_1985</ref> If we study the rocks in the central mound and in the ejecta, we can learn about what is deep underground. During an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE Colors show different minerals--some used to be deep underground.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterejectarim.jpg|Young crater showing layers, rim, and ejecta. Ejecta was thrown out by the force of impact.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.
</gallery>

The heat from an impact into ice-rich ground may produce channels emanating from the edge of the ejecta. These have been seen around a number of craters.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

</gallery>

Mars shows some interesting variations to the usual appearance of craters. At times the force of an impact reaches down to a different type of layer. The lower layer may be of a different color; therefore the ejecta that is spread on the landscape may be a different color.

<gallery class="center" widths="380px" heights="360px">
File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta Impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:29565 2075newcratercomposite.jpg|New, small crater Meteorite that hit here throw up dark material that was under a layer of bright, surface dust. We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref>

File:ESP 011425 1775newcrater.jpg|Dark ejecta of a new crater covers the bright surroundings.
</gallery>

Sometimes it looks as if an impact caused rocks to melt and when the molted rocks landed on the crater floor steam explosions occurred with ice-rich ground. What results is ground with a high density of pits.

<gallery class="center" widths="380px" heights="360px">
File:ESP 012531 1435pits.jpg|Floor of Hale Crater showing pits from steam explosions when hot, melt from an impact landed.

</gallery>

On occasion, an impact may go down to ice-rich ground or maybe to a layer of ice. Indeed, a number of craters expose ice on their floors which after a period of time disappears into the thin Martian atmosphere.

<gallery class="center" widths="380px" heights="360px">

File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
</gallery>

Then there is a type of crater which is common in locations we think contain much ice. Called “ring-mold” craters, they may be caused by a rebound of an ice layer. Experiments in labs confirm that this behavior can occur. Ring-mold craters are called that because they resemble ring-molds used in baking.

<gallery class="center" widths="380px" heights="360px">

File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.

26055ringmoldcrater.jpg|Close view of ring mold crater.
</gallery>

[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Now, during the impact process much material is sent flying in the air. Some of it will come down and create new craters. These are called secondary craters. They can be identified by all being of the same age. In addition, sometimes molted rock is produced by the impact. If molten rock lands on ice-rich ground, an area with a high density of pits will form. The hot molten rocks cause ice in the ground to burst into steam and cause pits to form.

<gallery class="center" widths="380px" heights="360px">

File:ESP 030244 2040secondarycraters.jpg|Secondary craters These are formed from material that is blasted way up in the air from the impact. Evidence that they are secondary craters is that they are all of the same age.
</gallery>

==Glaciers==

Mars may have had much water in past ages. Much of that water is now frozen in the ground and locked up in glacier-like forms. Many features have been found that are like glaciers—in that they are mostly made of ice and flow like glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> That means they move slowly and in a downhill direction. For ice to exist under today’s climate conditions, it must be covered with a layer of debris—dust, rocks, etc. A layer several meters or a few tens of meters thick will preserve ice for millions of years. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> Under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>
Martian glaciers show evidence of movement on their surfaces and in their shapes. The actual existence of water ice in some of them has been proven with radar studies from orbit. <ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> Some of them look just like alpine glaciers on the Earth. Most show piles of debris called moraine. This was material that was removed from one place and moved along to another by ice. Also, shapes looking just like eskers of terrestrial glaciers are common in places. Eskers form from streams moving under glaciers. These streams deposit rocks in tunnels in the ice at the bottom of glaciers. When the ice goes away, curved ridges stay behind.

<gallery class="center" widths="380px" heights="360px">

File:R0502109dorsaargentea.jpg|Possible eskers indicated by arrows. Eskers form under glaciers.

Wikilau.jpg|Lau Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Curved ridges are probably eskers which formed under glaciers.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.

File: Wikielephantglacier.jpg|Glacier in Greenland Glacier spreads out when it leaves valley.
</gallery>

For Mars, a number of names have been applied to these glacier-like forms. Some of them are tongue-shaped glaciers, lobate debris aprons (LDA’s), lineated valley fill (LVF), and concentric crater fill (CCF).<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 035327 2255tongues.jpg|Tongue-shaped glaciers These were made when a flow encountered an obstacle that made it split into two.
File:ESP 036619 2275ldalabeled.jpg|Lobate debris apron LDA) around a mound <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust . <ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref>

File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are now almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed. <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>
</gallery>

[[File:ESP 052138 1435lvf.jpg|thumb|600px|center|Lineated valley fill, as seen by HiRISE under [[HiWish program]]]]

==Ice in the ground==

Mars has some unique landscapes and features that are common just to it. Since so much water is frozen in the ground and since the thin atmosphere of Mars allows ground ice to disappear when it became exposed, unreal scenes can develop. Under current conditions on Mars, ice sublimates when exposed to the air. In that process, ice goes directly to a gas instead of first melting. It often starts with small, narrow cracks that get larger and larger. Once ice leaves the ground there is not much left except dust. And winds will eventually carry the dust away. The end result is various shaped holes, pits, canyons, and hollows. Some of these forms are called brain terrain, ribbed terrain, hollows, scalloped terrain, and exposed ice sheets. <ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> All of these may be of use to future colonists who need to find supplies of water.

[[File:45917 2220brainsopenclosed.jpg|Open an closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>]]

Open and closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows.

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> <ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref>
PIA22078 hireswideview.jpg|Wide view of triangular depression The colored strip shows the part of the image that can be seen in color. The wall at the top of the depression contains pure ice. This wall faces the south pole. <ref>Supplementary Materials Exposed subsurface ice sheets in the Martian mid-latitudes Colin M. Dundas, Ali M. Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, Nathaniel E. Putzig, Donna Viola, Sarah Sutton, Erin Clark, John W. Holt</ref>

PIA22077 hirescloseblue.jpg|Close, color view of wall containing ice from previous image <ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> <ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref>
</gallery>

[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of hollowed terrain caused by ice leaving the ground Box shows size of football field.]]

Close view of terrain caused by ice leaving the ground Box shows size of football field.

Other signs of water ice in the ground are: lobed (rampart craters), patterned ground, and possible pingos. Pattered ground or polygonal ground is common in ice-rich areas on Earth.

<gallery class="center" widths="380px" heights="360px">

File:56942 1075icepolygonslabeled2.jpg|Polygons Ice is in the low troughs that lie between the polygons.<ref>https://www.uahirise.org/ESP_047247_1150</ref>

</gallery>

Pingos are mounds that contain a core of ice.<ref>http://www.uahirise.org/ESP_046359_1250</ref> <ref>Soare, E., et al. 2019.</ref> <ref> Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref> They often have cracks on their surfaces. Cracks form when water freezes and expands. Pingos would be useful as sources of water for future colonies on the planet.

<gallery class="center" widths="380px" heights="360px">
51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.
ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program
</gallery>

Craters with ejecta that look like they were made by an impact into mud are called lobed or rampart craters. They were discovered by early, orbital missions to Mars. They are most common where we expect ice in the ground.

<gallery class="center" widths="380px" heights="360px">
File:Mars rampart crater.jpg|Yuty Crater showing lobe and rampart morphology; it looks like mud was formed during the impact.

</gallery>

Channels are sometimes found in a crater's ejecta or along the edges of the ejecta. Heat from the ejecta probably melted ice in the ground. Much heat is produced with an impact.

<gallery class="center" widths="380px" heights="360px">
File:ESP 055530 2180channels.jpg

</gallery>

==Liquid water==

Mars used to have lots of water and maybe a much thicker atmosphere billions of years ago. With liquid water, life is possible. Indeed, life may have first appeared on Mars before it occurred on Earth. Martian organisms could have been knocked off Mars by low angle asteroid impacts and found their way to Earth. Perhaps, the DNA of all Earthly organisms, included us, still contains genes from early Martian life. When we have samples of Mars brought back to Earth, we may find traces of DNA that are like ours.
Data are still being gathered and ideas debated, but scientists think that once Mars cooled down and lost its magnetic field, the solar wind may have carried away much of its atmosphere. In addition, some researchers have suggested that some of the atmosphere was splashed out by impacts. After the planet cooled, water became frozen in the polar ice caps and in the ground. But, for some period there was liquid water.

[[File:Mars vs Earth Solar Wind-1024x576.png|Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field]]

Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field

[[File:Mavenargoninfographic2.jpg|This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.]]

This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.

Huge amounts of water had to be present to carve the many outflow channels and produce the valley networks. Many of the outflow channels begin in "Chaos Terrain." Such a landscape often is where the ground seems to have just collapsed into giant blocks.<ref>https://marsed.asu.edu/mep/ice/chaos-terrain</ref> <ref>https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-9213-9_46-2</ref> It is believed that a shell of ice was created when the planet's climate cooled. Perhaps, at times the shell was broken by asteroid impacts, movements of magma, or faults. Such events would allow pressurized water to rapidly escape from under the shell of ice (shell has been called a cryosphere). Evidence is accumulating for the existence of an ocean. Lakes existed in low spots, especially craters.

[[File:ESP 056689 2210channelslowspotcropped.jpg |thumb|right|px||Channels that empty into a low area that could have been a lake Arrows show channels that lead to a low area that could have hosted a lake.]]

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel

These forms were shaped by running water.

<gallery class="center" widths="380px" heights="360px">

File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.

File:Ravi Vallis.jpg|Ravi Vallis was formed when the ground released a great flood of water from Aromatum Chaos. Maybe it started when hot magma moved under the ground.

File:Ister Chaos.jpg|Ister Chaos Water may have come out of this landscape when the ground broke up into blocks.<ref>https://www.uahirise.org/hipod/PSP_008311_1835</ref>

File:Branched Channels from Viking.jpg|These valley networks look like they were made from precipitation.
</gallery>

At present, it is hotly debated just how long water stayed around. The sun was not as strong billions of years ago. Greenhouse gases like carbon dioxide, methane, and hydrogen may have made Mars warm enough for liquid water. Massive volcanoes would have given up many of these gases, along with water vapor.

[[File: Olympus Mons Side View.svg.png|thumb|left|300px|Height of Olympus Mons compared to tall mountains on Earth]]

Maybe the water just existed for short periods. Some studies have showed that large impacts into icy ground could release water and change the local climate for thousands of years. Also, impacts may have punctured an ice shell and allowed pressurized water to flow out for a time. Any water moving on the surface would quickly freeze at the top. But, it would continue to flow under the ice for a long time and make many of the channels we see today. Heat to allow water to flow may have been from underground flows of magma. On the other hand, many of the features created by liquid water could have formed under massive ice sheets where water was insulated from the Martian atmosphere.
 
==Layers==

Many locations display layered formations. Some are mostly just made of ice and dust. These types of layers are common in the polar ice caps, especially the northern ice cap.<ref>https://www.uahirise.org/hipod/PSP_008244_2645</ref> Other, rockier layers, are visible in the walls of impact craters and canyon walls.

<gallery class="center" widths="380px" heights="360px">

File:PSP 008244 2645northicecaplabeled.jpg|Layers in northern ice cap that are exposed along a cliff

File:ESP 054515 2595icecaplayers.jpg|Close view of many layers exposed in northern ice cap
File: 57080 1380layerscratercolor.jpg|Layers in crater wall in Phaethontis quadrangle, as seen by HiRISE under HiWish program
48980 1725layersclose2.jpg|Close view of layers in Louros Valles
</gallery>

And then there are layers that may be more recent, they may be connected to repeated climate changes. Some have regularity to them. The climate of Mars changes drastically due to changes in the tilt of its rotational axis. At times, like now, it is close to the Earth’s 23.5 degrees. But, at times it may be as much as 70 degrees.<ref> Schorghofer, Norbert (2008). "Temperature response of Mars to Milankovitch cycles". Geophysical Research Letters. 35 (18): doi:10.1029/2008GL034954.</ref> <ref>ouma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref>Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Tilt governs the seasons and where ice is distributed. Currently, the largest deposit of ice is at the poles. At other times could have been at mid-latitudes. Imagine how it would be to have Pittsburgh under an ice cap. Mars may have had ice caps at the latitude of Pittsburgh.

<gallery class="center" widths="380px" heights="360px">

File:Mars Ice Age PIA04933 modest.jpg|How Mars may have looked with a greater tilt of Mars' rotational axis caused increased solar heating at the poles. This larger tilt would make a surface deposit of ice and dust down to about 30 degrees latitude in both hemispheres.
</gallery>

There is an ice-rich material that falls from the sky. It is called latitude dependent mantle.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It is thought to come from snow and ice-coated dust. At times, there is a lot of dust in the air. When that happens, moisture will freeze onto dust grains. When the ice-coated dust particle gets heavy enough, it will fall. Recent accumulations of this mantle look smooth. In some places the mantle is layered. Some formations, particularly in protected spots in craters and against mounds, suggest that these layered formations had many more layers. The wind sometimes shapes them into layered mounds.

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.
[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210dipping.jpg|Layers leaning against a mound The mound protected them from erosion.
</gallery>

The older layers visible on crater and canyon walls may have different sources. Some are from lava flows or ash from volcanoes. Some may have formed under water like most layered sedimentary rocks on the Earth.<ref>https://www.uahirise.org/PSP_008391_1790</ref> Curiosity, our robotic explorer, has found that layers in Gale Crater were made from sediments at the bottom of a lake. Some may be just from dust and debris settling in low areas and then being cemented by rising groundwater carrying minerals like sulfates and silica.<ref> Rates and mechanisms of chemical weathering of ferromagnesian silicate minerals on Mars | date = 1993 | last1 = Burns | first1 = Roger G | journal = Geochimica et Cosmochimica Acta | volume = 57 | issue = 19 | pages = 4555–4574 |</ref> <ref>{{cite journal | doi = 10.1029/92JE02055 | title = Rates of Oxidative Weathering on the Surface of Mars | date = 1993 | last1 = Burns | first1 = Roger G. | last2 = Fisher | first2 = Duncan S. | journal = Journal of Geophysical Research | volume = 98 | issue = E2 | pages = 3365–3372 |</ref> <ref>Hurowitz | first1 = J. A. | last2 = Fischer | first2 = W. W. | last3 = Tosca | first3 = N. J. | last4 = Milliken | first4 = R. E. | year = 2010 | title = Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars | url = https://authors.library.caltech.edu/18444/2/ngeo831-s1.pdf| journal = Nat. Geosci. | volume = 3 | issue = 5| pages = 323–326 | doi = 10.1038/ngeo831 | </ref> Sometimes a crater may have been filled up with layered rocks and then the rocks may have been eroded by the wind in such a way to just leave a layered mound in the center of the crater. Gale crater, where Curiosity is exploring, was like that.

<gallery class="center" widths="380px" heights="360px">

Image:Topographic Map of Gale Crater.jpg|Gale Crater with Aeolis Mons rising from the center. The noted [[Curiosity]] landing area is near Peace Vallis in Aeolis Palus. Curiosity landed in the northern part of the crater. Colors indicate elevation.

File:Marscratermounds.jpg|Some layers form mounds in the center of craters. They could have been made by the erosion of layers that were deposited after the impact.

</gallery>

[[File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|600pxr|Rock layers in the Murray Buttes area in lower Mount Sharp They look like rocks formed at the bottom of lakes and their chemistry proves it.]]

Rock layers in the Murray Buttes area in lower Mount Sharp

==Igneous effects==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

<gallery class="center" widths="380px" heights="360px">
File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons

</gallery>

Igneous refers to rock that is heated to a molten condition. On Mars, this is a major shaper of landscapes. Lava comes out of the ground at holes called vents. Flows of lava can be about as fluid as water and move long distances. Sometimes the top cools to a solid, but the liquid rock continues to flow underneath a hard crust. Giant pieces of this stiff crust can move around as “lava rafts.”

<gallery class="center" widths="380px" heights="360px">

File:ESP 054891 2040lavarafts.jpg|Lava rafts
</gallery>

In other places, lava travels in channels. When they make a hard crust, lave tunnels are created. A picture below shows lava tunnels.<ref> https://www.uahirise.org/PSP_009501_1755</ref> After the liquid lava moves away, an empty tunnel can be formed. These are significant for future colonists as they may be where our first colonies will be built. There people would be protected from surface radiation. We have already found spots that might be openings to these tunnels in HiRISE images.

[[File:PSP 009501 1755lavatube.jpg |Lava tubes and lava tunnels Future colonists may live in lava tunnels.]]

[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|left|Possible cave entrance to a lava tunnel Future colonies may live in caves for protection from weather and radiation.]]

[[File:Tharsis mons Viking.jpg |right|thumb|px|Some of the Martian volcanoes, as seen by Viking 1]]

There are huge volcanoes that were noticed by our first spacecraft to orbit the planet. The first satellite to orbit the planet was only able to see a few volcanoes peeking above a massive global dust storm. Since Mars has not had plate tectonics for nearly all of its history, volcanoes can grow very large.<ref>https://www.jpl.nasa.gov/edu/learn/video/mars-in-a-minute-how-did-mars-get-such-enormous-mountains/</ref> Lava and ash can erupt from the same spot for long periods of time. On the Earth, the plates move so volcanoes can only grow so big.

<gallery class="center" widths="380px" heights="360px">

File:Olympus Mons alt.jpg|Olympus Mons, tallest volcano in solar system The mass of volcanoes on mars stretches and cracks the crust causing faults.

</gallery>

Volcanoes are only the surface manifestations of liquid rock. There is more molted rock moving under the surface than what we see above ground in volcanoes. Molted rock is called magma when underground. Stretching out around volcanoes underground are various structures. Vast linear walls, called dikes radiate out from volcanoes. On Mars they can be many miles in length. Many form by moving along cracks or weak parts of rocks. Some scientists have suggested that they from long troughs when they melt ground ice. Troughs are some of the longest features on Mars.

<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 2100dike2.jpg|Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

</gallery>

Besides the direct action of lava and magma, volcanoes affect Mars with just their weight. The mass of a volcano stretches the crust and makes cracks form. The large canyon system of Valles Marineris may have been started with some sort of stretching of the crust. But, its stretching may have been caused by rising mantle plumes or maybe the rise of Tharsis where so many volcanoes are located.<ref>https://astronomy.com/magazine/ask-astro/2013/08/valles-marineris</ref> Cracks in the crust are called faults. Faults on Mars are often double faults. A center section is lower than the sides. This arrangement is called a graben. On the Earth they can turn into lakes like Lake George in New York State. Graben on Mars can be thousands of miles long.

Researchers have discovered that there is a large plume under Cerberus Fossae. It is almost the area of the continental United States. The plume is warmer than its surroundings by 95 to 285 degrees Celsius (171 to 513 degrees Fahrenheit). Plumes like this are like the plume under Hawaii.

Evidence for the plume are (1) origin of nearly all Marsquakes, (2) a rise of a mile above the surroundings, (3) crater floors tilted away from the rise, and (4) slight variations in the gravity field showing that the uplift is supported from deep within the planet.
Cerberus Fossae is in Elysium Planitia, a site of the youngest known volcanic eruption on Mars. That eruption produced a small explosion of volcanic ash around 53,000 years ago--a short time in geology.

The discovery of a plume increases the chance of life. Heat from the plume could melt ground ice; consequently, allowing chemical reactions that could sustain life.<ref>A. Broquet, J. C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nature Astronomy, 2022; DOI: 10.1038/s41550-022-01836-3</ref> <ref>https://www.sciencedaily.com/releases/2022/12/221205121545.htm</ref> <ref>https://www.nature.com/articles/s41550-022-01836-3</ref>

<gallery class="center" widths="380px" heights="360px">

File:Troughs in Elysium Planitia.jpg|Troughs showing layers The center section of the picture is in color. With HiRISE only a strip in the middle is in color. These troughs are in Cerberus Fossae, as seen by HiRISE under the HiWish program. Location is 15.819 N and 161.448 E. Cerberus Fossae is the source of most of the Marsqukes detected by the InSight mission.

ESP 046251 2165graben.jpg|Straight trough is a fossa that would be classified as a graben. Curved channels may have carried lava/water from the fossa. Picture taken with HiRISE under [[HiWish program]].

File:ESP 057834 2005troughmesa.jpg|Trough or graben cutting through mesa
</gallery>

Sometimes lava moves over frozen ground. That results in steam explosions. Large fields of small cones can be produced when this happens. Those cones are called “rootless cones” since they do not go down very far.

<gallery class="center" widths="380px" heights="360px">

File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones
File:45384 2065cones2.jpg|Close view of rootless cones
</gallery>

Volcanoes sometimes explode with great amounts of ash that travels long distances, covering everything. Some of the layers seen on Mars are probably from these ash deposits. These deposits do not contain boulders and are easily eroded by just the wind. Two areas on Mars have widespread and thick deposits made in this way; they are called the Medusae Fossae Formation and the Electris deposits. These relatively soft deposits often form shapes called yardangs. They are sort of boat shaped and show the direction of the prevailing wind when they were created.

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
</gallery>

Much of the atmosphere of Mars came from volcanoes. Volcanoes give off large amounts of carbon dioxide and water, along with other chemicals. Some of these chemical compounds are “greenhouse gases” that served to heat up early Mars.
A few places are thought to be where volcanoes erupted under ice. The shapes that resulted look like those made on Earth when a volcano erupted under the ice.

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

==Bright dust==

A thin coating of bright-toned dust covers almost all parts of Mars. It has a rust brown color. It is not too noticeable until it is not here. Some things remove the dust and then reveal the dark underlying surface. The contrast between this thin coating and the underlying dark rock is striking. Much of the difference derives from how NASA pictures are processed.<ref> Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> To bring out more detail, the brightest tone is considered white, while the darkest black. It only takes a very thin layer of dust to make a difference in the over-all appearance of a picture. Experiments on Earth found that the layer may be only as thick as the diameter of a human hair.<ref> https://en.wikipedia.org/wiki/Micrometre
</ref> Incidentally, the dust has the color of rust because it is rust—it is oxidized iron.

Dark slope streaks occur when bright dust avalanches down steep slopes like crater walls. They can be very long and elaborate. These movements are affected by obstacles like boulders. A streak may split into two when encountering a boulder. They may be initiated when an impact happens nearby.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars" ''Icarus'' 2012; 217 (1) 194 </ref><ref>http://redplanet.asu.edu/</ref>
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>

[[File:ESP 043128 2005mesastreaks.jpg|600pxr|Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]]]

Dark slope streaks on layered mesa

[[File:55107 1930streaksboulders2.jpg|thumb|500px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

<gallery class="center" widths="380px" heights="360px">

</gallery>

Another thing that causes light and dark patterns is a dust devil. These miniature tornadoes remove the bright dust and make straight and/or curved tracks. They are common especially in areas with much dust cover and at certain times of the day. They have been observed both from orbit and from the ground.<ref>https://www.uahirise.org/ESP_042201_1715</ref> We even have movies of them in action. They can form beautiful scenes. And, the arrangement of the tracks can be different in just a few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">
</gallery>

The atmosphere of Mars contains a great deal of fine dust. Large dust storms happen just about every Martian year. A year on Mars is about 23 of our months. Dust storms typically occur when it is spring or summer in the southern hemisphere. At that time, Mars is at its closest to the sun. Unlike the Earth, Mars has a very elliptical orbit which brings it much closer to the sun than at other times. This makes for differences in season both in intensity and length. For example the southern summer is much shorter than that of the north. However, the summer season in the southern hemisphere is much more intense.

[[File:Marsorbitsolarsystem.gif|Comparrsion of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle.<ref> https://www.compadre.org/osp/items/detail.cfm?ID=9757</ref> <ref> https://www.compadre.org/osp/items/detail.cfm?ID=7305</ref>]]

Comparison of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle. Mars changes its distances to sun a great deal--this changes makes drastic seasonal changes.

==Dry Ice==

Some of the strangest things on Mars involve dry ice—solid carbon dioxide. The cold conditions on Mars cause much of the carbon dioxide to freeze out of the atmosphere. Both ice caps contain some dry ice. Each year about 25% of the atmosphere freezes out onto the poles. This is so much that the gravity of the planet shifts. <ref>NASA/Goddard Space Flight Center. "New gravity map gives best view yet inside Mars." ScienceDaily. ScienceDaily, 21 March 2016. https://www.sciencedaily.com/releases/2016/03/160321154013.htm.</ref> <ref>Antonio Genova, Sander Goossens, Frank G. Lemoine, Erwan Mazarico, Gregory A. Neumann, David E. Smith, Maria T. Zuber. Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science. Icarus, 2016; 272: 228 DOI: 10.1016/j.icarus.2016.02.05</ref> Winds and weather systems that almost look like the Earth’s are produced by so much dry ice changing to a gas at these times.

[[File:PIA00190-MC-30-MareAustraleRegion-19980605.jpg |right|thumb|px| Region of South Pole with ice cap Southern ice cap is much smaller than the North’s.]]

[[File:Mars NPArea-PIA00161.jpg |left|thumb|px| Spiral troughs in the northern ice cap]]

<gallery class="center" widths="380px" heights="360px">

File:Marscyclone hst.jpg|Cyclone on Mars, as seen by HST
</gallery>

In the winter dry ice accumulates. So, large areas appear white. When things warm up in the spring, the landscape gets many dark spots and areas. <ref>https://mars.jpl.nasa.gov/mgs/msss/camera/images/dune_defrost_6_2001/</ref><ref>SPRING DEFROSTING OF MARTIAN POLAR REGIONS: MARS GLOBAL SURVEYOR MOC AND TES MONITORING OF THE RICHARDSON CRATER DUNE FIELD, 1999–2000. K. S. Edgett, K. D. Supulver, and M. C. Malin, Malin Space Science Systems, P.O. Box 910148, San Diego, CA 92191-0148, USA.</ref> <ref>K.-Michael Aye, K., et al. PROBING THE MARTIAN SOUTH POLAR WINDS BY MAPPING CO2 JET DEPOSITS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2841.pdf</ref> In the past, observers thought that Mars was full of life. They saw the northern ice cap get smaller and smaller. At the same time, they watched the area get darker. They concluded that the darkening was vegetation growing from the water coming out of the ice caps. What was happening was the dry ice was disappearing. Today, we can watch this darkening occur in great detail. <ref>http://www.jpl.nasa.gov/news/news.php?release=2013-034</ref>

<gallery class="center" widths="380px" heights="360px">

43821 2555defrostingdune2.jpg|Defrosting surface Frost is disappearing in patches from a dune and from the surrounding surface. Note: the north side (side near top) has not defrosted because the sun is coming from the other side.

File:ESP 011605 1170defrosting.jpg|Defrosting The dark spots are where the ice has gone. We now can see the underlying dark surface.

</gallery>

In some places, there are many geyser-like eruptions of gas and dark dust.<ref>https://www.uahirise.org/</ref> High pressure gas and dust explode out of the ground. Winds often blow these eruptions into dark plumes. After many observations, scientists concluded that what happens is that a transparent-translucent dry ice slab forms in the winter. With increased sun in the spring, pressure builds up under this slab as light heats cavities under the slab and causes dry ice to turn into a gas. At weak areas in the slab, the gas comes out along with dark dust.<ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> The channels may get dark from the dust and make a pattern that looks like a spider. These patterns are called “spiders.” <ref>http://mars.jpl.nasa.gov/multimedia/images/2016/possible-development-stages-of-martian-spiders</ref> <ref>http://spaceref.com/mars/growth-of-a-martian-trough-network.html</ref> <ref>Benson, M. 2012. Planetfall: New Solar System Visions</ref> <ref>http://www.astrobio.net/topic/solar-system/mars/spiders-invade-mars/</ref> <ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>Portyankina, G., et al. 2017. Present-day erosion of Martian polar terrain by the seasonal CO2 jets. Icarus: 282, 93-103.</ref> The official name for spiders is "araneiforms."<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>

<gallery class="center" widths="380px" heights="360px">

File:Spiders2eruptionlabeled2.jpg|Drawing showing the cause of plumes and spiders. In the spring, sunlight goes through a clear slap of dry ice. It heats up the dark ground. Heat causes dry ice to turn into a gas and pressurize. When pressure is great enough a dark plume of carbon dioxide gas and dark dust erupt. Wind will form it into a fan shape plume.

</gallery>

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

<gallery class="center" widths="380px" heights="360px">

ESP 048845 1010spiders.jpg|Wide view of crater that contains examples of spiders
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
</gallery>

Around the southern cap, dry ice makes round, low areas that look like Swiss cheese. <ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data
Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> So, it is called “Swiss cheese terrain.” The roundness of the pits is believed to be related to the low angle of the sun.<ref>Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

[[File:South Pole Terrain.jpg|600pxr|HiRISE view of South Pole Terrain.]]
HiRISE view of South Pole Terrain.

<gallery class="center" widths="380px" heights="360px">
</gallery>

The ice caps contain a great deal of water ice. The northern cap has a covering of dry ice only 1 meter thick in the winter, but the southern cap always has a coating of dry ice up to 8 meters thick. Large deposits of dry ice are also buried in the water ice of the cap at some locations.

<gallery class="center" widths="380px" heights="360px">
</gallery>

==Gullies==

Since 2000, researchers have been studying gullies that are common in the mid-latitudes on steep slopes. They look like they were carved by liquid water. After many years of observations, it has been concluded that today they are being made by chunks of dry ice sliding down slopes.<ref>Vincendon, M. 2015. JGR:120, 1859–1879.</ref> <ref> Pilorget | first1 = C. | last2 = Forget | first2 = F. | year = 2016 | title = Formation of gullies on Mars by debris flows triggered by CO2 sublimation | url = | journal = Nature Geoscience | volume = 9 | issue = | pages = 65–69 | doi = 10.1038/ngeo2619 | </ref> <ref>Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.</ref> However, some scientists concede that water may have been involved in their formation in the past.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm</ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 047956 1420gullies.jpg|Crater with gullies, as seen by HiRISE under HiWish program
File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
</gallery>

[[File:Gullies near Newton Crater.jpg|600pxr|Gullies near Newton Crater]]
Gullies near Newton Crater

==Other features==

The surface of Mars is very old—billions of years. This is plenty of time for rocks to have broken down into sand. In low places, like crater floors, sand accumulates and makes dunes. Some are quite pretty. And the colors used by NASA make them even more pretty—they can appear blue, purple, green, or turquoise.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:61974 1710dunesrgb2.jpg|Dunes
File:ESP 046378 1415dunefield.jpg|Black and white, wide view of dunes
File:ESP 55095 2170dunes.jpg|Dunes near Sklodowski Crater in North Arabia Terra
</gallery>

Related to dunes are something called transverse aeolian ridges (TAR’s). They look like small dunes. They are often parallel to each other. They generally are in low areas and one of the most common landforms on Mars.<ref>http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1598.pdf|format=PDF|type=conference paper|title=Investigations of transverse aeolian ridges on Mars|first1=Daniel C.|last1=Berman|first2=Matthew R.|last2=Balme|year=2012|publisher=Lunar and Planetary Science Conference</ref> They are mid-way in height between dunes and ripples; they are not well understood.<ref>http://www.uahirise.org/ESP_042625_1655</ref> <ref>Berman, D., et al. 2018. High-resolution investigations of Transverse Aeolian Ridges on Mars: Icarus: 312, 247-266.</ref>

<gallery class="center" widths="380px" heights="360px">

File:64038 2155tarslabeled.jpg|Transverse Aeolian Ridges, as seen by HiRISE under HiWish program

File:ESP 039563 1730tars.jpg|Transverse Aeolian Ridges (TAR’s) between yardangs We do not totally understand these.
File:ESP 042625 1655tars.jpg|Wide view of Transverse Aeolian Ridges (TAR’s) near a channel
</gallery>

Some landscape expressions are mysteries.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>

In rocks of certain ages, often at the bottom of low spots are complex arrangements of ridges.
These are walls of rock.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>

There are different ideas for what caused them. Over 14,000 people from around the world helped map them, so that scientists could better understand them. The team of volunteers found 952 polygonal ridge networks in an area that measures about a fifth of Mars’ total surface area. Some ridges contain clays, so water may have been involved in their formation because clays need water to be formed.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al. 2022. Irregular polygonal ridge networks in ancient Noachian terrain on Mars. Icarus. 374. 114833</ref>

[[File:ESP 036745 1905top.jpg|600pxr|Linear ridge networks]]
Linear ridge networks

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
</gallery>

[[File:Ridgesmappedbycitizens.jpg|600pxr|Map of Linear ridge networks]]

Map of Linear ridge networks

Of eerie beauty are odd arrangements visible on the bottom of the Hellas Impact basin. We are not sure exactly what caused them. They have been called honeycomb terrain or banded terrain.

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Honeycomb terrain on floor of Hellas Basin The exact origin of these shapes is unknown at present.

<gallery class="center" widths="380px" heights="360px">

</gallery>

Mars is one planet that we can see the surface clearly. Its super thin atmosphere (about 1% of the Earth’s) makes it easy to observe. Early telescopes revealed many markings and patterns. As we sent better and better cameras to examine it, more mysteries and more beautiful scenes emerged. We were able to answer many questions, but always more questions arose concerning what we were seeing.

<gallery class="center" widths="380px" heights="360px">

</gallery>

==References==

{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]

*[https://www.youtube.com/watch?v=jcaawA7d0ro Sublimation of Dry Ice]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

Geological processes that have shaped Mars: Why Mars looks like it does

2022-12-09T17:20:48Z

Suitupandshowup: /* Igneous effects */

Article written by Jim Secosky. Jim is a retired science teacher who has used the Hubble Space Telescope, the Mars Global Surveyor, and HiRISE.

[[File:Mars, Earth size comparison.jpg|left|thumb|px|Earth and Mars Earth is much bigger, but both have the same land area. Mars has about one third the gravity of the Earth.]]

Mars looks like it does because of certain geological processes. Some of them are common to both the Earth and Mars. However, others are rare or nonexistent on the Earth. Mars shows an extremely old record of the past that is lacking on the Earth. Plate tectonics and vigorous air and water erosion has wiped out nearly all of the past geology of the Earth. In contrast, much of the Martian surface is billions of years old. Another factor that has affected the appearance of Mars is its extreme cold. The coldness of the planet makes carbon dioxide significant. It has influenced Mars both as a gas and as a solid. As a greenhouse gas, early in the history of the planet, it may have been thick enough in the atmosphere to help raise the temperature enough to permit water to flow, to carve rivers, to form lakes and an ocean. Indeed, it may have been warm enough from carbon dioxide for life to first originate on Mars and then travel to the Earth on meteorites. Today, as a solid, carbon dioxide (dry ice) produces the ubiquitous gullies found in numerous areas of the planet.

==Erosion Related==

As on the Earth material was laid down and then later eroded. Many spectacular scenes are present with places that were mostly eroded, but with remnants remaining in the form of buttes and mesas. Sometimes, sediments were put down in layers. As a result beautiful places were created. On the Earth we admire such layers in Monument Valley and many beautiful canyons. The same types of landscapes show up on Mars.
The top layer of buttes and mesas is hard and resistant to erosion. It protects the lower layers from being eroded away. On Mars that hard, cap rock could be made from a lava flow. Many, large areas of Mars have eroded in such a fashion. The remaining structures are called mesas or buttes—if they are small in area. Some mesas and buttes show layers. Mesas show the kind of material that covered a wide area.

<gallery class="center" widths="380px" heights="360px">

File:16 21 2117 monument valley.jpg|Spearhead Mesa in Monument Valley Note the flat top and steep walls that are characteristic of mesas.

Image:Glacier as seen by ctx.JPG|Mesa in Ismenius Lacus quadrangle, as seen by CTX. Mesa has several glaciers eroding it.

File:58563 2225mesa.jpg|Mesa

File:45016 2080mesas.jpg|Mesas, as seen by HiRISE under HiWish program These are like the ones in Monument Valley

File:55119 2080ridgesmesafootballlabeled3.jpg|Butte: Buttes have a much smaller area than mesas, but both have a hard cap rock on the top. Box shows the size of a football field.

</gallery>

As on the Earth, there are landslides. However, they could be a little different since Mars has only about a third of Earth’s gravity.

<gallery class="center" widths="380px" heights="360px">

File:ESP 043963 1550landslide.jpg|Landslide

</gallery>

Common features in certain areas of the Earth’s surface are “Yardangs.” They are found in desert areas which contain much sand. The wind blows sand and shapes the relatively soft grained deposits into the long, boat shapes of yardangs. On Mars it is thought that these forms are the result of the weathering of huge ash deposits from volcanoes. Mars has the biggest known volcanoes in the solar system. Many probably threw out much fine-grained material which was easily eroded to make vast fields of yardangs. Regions called the “Medusa Fossae Formation and Electris deposits contain thousands of yardangs.

<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs.jpg|Yardangs
</gallery>

Unlike the Earth, Mars shows landscapes that are billions of years old. In that time material has been deposited and then eroded and/or greatly changed. Some features have been “inverted.” Low areas turned into high areas. Low areas like stream beds were filled with erosion-resistant materials like lava and large rocks. Later, the surrounding, softer ground became eroded. As a result, the old stream bed now appears raised. We can tell it was originally a stream bed since the overall shape from above still looks like a stream with curves and branches.

[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Inverted streams Here a branched stream became filled with hard material and then the surrounding ground was eroded.]]

Another structure made with erosion is a “pedestal crater.” They are abundant in regions far from the equator. These craters seem to sit on little circular shelves or pedestals.<ref>https://www.uahirise.org/hipod/PSP_008508_1870</ref> In the impacting process, ejecta fell about the crater and protected the underlying ground from erosion. These craters occur where we think there was a great deal of ice in the ground. So, much of the material that disappeared was just ice. With that being said, pedestal craters give us an indication of how much ice was in the region. In some places hundreds of meters of ice-rich ground were removed to make pedestal craters.<ref> Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''. LPSC</ref> <ref> https://web.archive.org/web/20100118173819/http://themis.asu.edu/feature_utopiacraters</ref> <ref> = McCauley, John F. 1972. Mariner 9 Evidence for Wind Erosion in the Equatorial and Mid-Latitude Regions of Mars. Journal of Geophysical Research: 78, 4123–4137(JGRHomepage). |doi = 10.1029/JB078i020p04123</ref>

[[File:ESP 037528 2350pedestal.jpg |thumb|left|px||Pedestal crater Surface close to crater was protected from erosion by the ejecta. In the past all the surrounding ground was at the level of the pedestal. Most of the loss is thought to be from the loss of ice."]]

[[Image:Pedestal crater3.jpg |thumb|right|px||Pedestal craters form when the ejecta from impacts protect the underlying material from erosion. As a result of this process, craters appear perched above their surroundings]]

[[File:Pedestaldrawingcolor2.jpg|thumb|600px|center|Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further. Heat and wind from the impact hardens the surface against erosion. This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]

Some structures on Mars are being “exhumed.” Craters are observed that are being uncovered. In the past, impacts produced craters. Later, they were buried. Now they are in the process of being uncovered by erosion. When an asteroid strikes the surface it generates a hole and throws out ejecta all around it. A circular hole is the result. If we see a half of a crater, we know that that it is being exposed by erosion. Impacts do not produce half holes!

<gallery class="center" widths="380px" heights="360px">

File:57652 2215exhumed.jpg|Close view of exhumed crater This crater is and was under a set of dipping layers.
[[File:ESP 055550 1660exhumed.jpg|Exhumed crater This crater was covered over and now it is being uncovered or "exhumed."]]
</gallery>

==Craters==

Impact craters occur on both the Earth and Mars. However, due to the extreme age of the Martian surface, most of Mars shows a high density of impact craters especially in the southern hemisphere. Craters do not last long on the Earth. Remember, the Earth experiences a great deal more erosion due to its thick atmosphere and abundant water. And, at intervals, the crust is taken into the Earth at plate boundaries. We know a fair amount about impact craters because the Earth has impact craters like Meteor Crater in Arizona that we can study easily.

<gallery class="center" widths="380px" heights="360px">

File:Barringer Crater USGS.jpg|Meteor Crater in Arizona
</gallery>

We know that a new crater will have a rim and ejecta around it. Large ones may have a central uplift and maybe a ring around the middle of the floor. We know that the impact brings up material from deep underground.<ref>https://www.uahirise.org/hipod/PSP_007464_1985</ref> If we study the rocks in the central mound and in the ejecta, we can learn about what is deep underground. During an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE Colors show different minerals--some used to be deep underground.

</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 046046 2095craterejectarim.jpg|Young crater showing layers, rim, and ejecta. Ejecta was thrown out by the force of impact.

Wikisinton.jpg|West side of Sinton Crater, as seen by CTX camera (on [[Mars Reconnaissance Orbiter]]) A central peak is visible--it occurs in larger craters and is caused by a rebound from the force of the impact.
</gallery>

The heat from an impact into ice-rich ground may produce channels emanating from the edge of the ejecta. These have been seen around a number of craters.

<gallery class="center" widths="380px" heights="360px">

File:ESP 057139 2140channels.jpg|Channels These channels are in the ejecta of a crater; hence, they may have formed from warm ejecta melting ground ice.

</gallery>

Mars shows some interesting variations to the usual appearance of craters. At times the force of an impact reaches down to a different type of layer. The lower layer may be of a different color; therefore the ejecta that is spread on the landscape may be a different color.

<gallery class="center" widths="380px" heights="360px">
File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta Impact reached down to a layer that is light-toned. That light-toned material was then deposited on a dark surface.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:29565 2075newcratercomposite.jpg|New, small crater Meteorite that hit here throw up dark material that was under a layer of bright, surface dust. We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref>

File:ESP 011425 1775newcrater.jpg|Dark ejecta of a new crater covers the bright surroundings.
</gallery>

Sometimes it looks as if an impact caused rocks to melt and when the molted rocks landed on the crater floor steam explosions occurred with ice-rich ground. What results is ground with a high density of pits.

<gallery class="center" widths="380px" heights="360px">
File:ESP 012531 1435pits.jpg|Floor of Hale Crater showing pits from steam explosions when hot, melt from an impact landed.

</gallery>

On occasion, an impact may go down to ice-rich ground or maybe to a layer of ice. Indeed, a number of craters expose ice on their floors which after a period of time disappears into the thin Martian atmosphere.

<gallery class="center" widths="380px" heights="360px">

File:Iceincraterscomparison.jpg|Exposed ice in small craters The fresh ice had almost disappeared when the second picture was taken. This set of images is good evidence that ice lies under a thin layer of debris.
</gallery>

Then there is a type of crater which is common in locations we think contain much ice. Called “ring-mold” craters, they may be caused by a rebound of an ice layer. Experiments in labs confirm that this behavior can occur. Ring-mold craters are called that because they resemble ring-molds used in baking.

<gallery class="center" widths="380px" heights="360px">

File:52260 2165ringmoldcraters2.jpg|Ring mold craters They may contain ice.

26055ringmoldcrater.jpg|Close view of ring mold crater.
</gallery>

[[File:Ringmolddiagramlabeled.jpg|600pxr|Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.]]
Ring-mold craters form when an impact goes through to an ice layer. The rebound forms the ring-mold shape, and then dust and debris settle on the top to insulate the ice.

Now, during the impact process much material is sent flying in the air. Some of it will come down and create new craters. These are called secondary craters. They can be identified by all being of the same age. In addition, sometimes molted rock is produced by the impact. If molten rock lands on ice-rich ground, an area with a high density of pits will form. The hot molten rocks cause ice in the ground to burst into steam and cause pits to form.

<gallery class="center" widths="380px" heights="360px">

File:ESP 030244 2040secondarycraters.jpg|Secondary craters These are formed from material that is blasted way up in the air from the impact. Evidence that they are secondary craters is that they are all of the same age.
</gallery>

==Glaciers==

Mars may have had much water in past ages. Much of that water is now frozen in the ground and locked up in glacier-like forms. Many features have been found that are like glaciers—in that they are mostly made of ice and flow like glaciers. <ref name="SquyresCarr">cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = | journal = Science | volume = 213 | issue = | pages = 249–253 | doi = 10.1126/science.231.4735.249 | </ref> <ref name="Headetal2010">cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | url = | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | </ref> <ref name="HoltetalSHARAD">cite journal | last1 = Holt | first1 = J.W. | display-authors = 1 | last2 = et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | url = | journal = Science | volume = 322 | issue = | pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078|</ref> <ref name="MorganetalDeuteronilus">| last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | url = | journal = Icarus | volume = 202 | issue = | pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 |</ref > <ref name="Plautetal">cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | doi = 10.1029/2008gl036379 | journal = Geophys. Res. Lett. | volume = 36 | issue = | page = L02203 | </ref> <ref name="Bakeretal2010">cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | url = | journal = Icarus | volume = 207 | issue = | pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | </ref> <ref name="ArfstromHartmann">cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | url = | journal = Icarus | volume = 174 | issue = | pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 |</ref> That means they move slowly and in a downhill direction. For ice to exist under today’s climate conditions, it must be covered with a layer of debris—dust, rocks, etc. A layer several meters or a few tens of meters thick will preserve ice for millions of years. <ref name="WilliamsSnowpack">cite journal | last1 = Williams | first1 = K. E. | display-authors = 1 | last2 = et al | year = 2008 | title = Stability of mid-latitude snowpacks on Mars | url = | journal = Icarus | volume = 196 | issue = 2| pages = 565–577 | doi=10.1016/j.icarus.2008.03.017 |</ref> Under today’s conditions any exposed ice would undergo [[sublimation]] and disappear into the thin Martian atmosphere. That is, it would go directly from a solid to a gas. But, the isulating effect of surface material prevents loss of ice.<ref name="Plautetal" /> <ref name="WilliamsSnowpack" /> <ref name="Head, J. 2005">cite journal | doi = 10.1038/nature03359 | last1 = Head | first1 = J. | date = 2005 | last2 = Neukum | first2 = G. | last3 = Jaumann | first3 = R. | last4 = Hiesinger | first4 = H. | last5 = Hauber | first5 = E. | last6 = Carr | first6 = M. | last7 = Masson | first7 = P. | last8 = Foing | first8 = B. | last9 = Hoffmann | first9 = H. | last10 = Kreslavsky | first10 = M. | last11 = Werner | first11 = S. | last12 = Milkovich | first12 = S. | last13 = Van Gasselt | first13 = S. | last14 = Co-Investigator Team | first14 = The Hrsc | title = Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars | url = | journal=Nature | volume = 434 | issue = 7031| pages = 346–350 | pmid=15772652|</ref> <ref> Head, J., et al. 2009. Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits. Earth and Planetary Science Letters. Doi:10.1016/j.epsl.2009.06.041</ref>
Martian glaciers show evidence of movement on their surfaces and in their shapes. The actual existence of water ice in some of them has been proven with radar studies from orbit. <ref>http://news.discovery.com/space/mars-ice-sheet-climate.html</ref> Some of them look just like alpine glaciers on the Earth. Most show piles of debris called moraine. This was material that was removed from one place and moved along to another by ice. Also, shapes looking just like eskers of terrestrial glaciers are common in places. Eskers form from streams moving under glaciers. These streams deposit rocks in tunnels in the ice at the bottom of glaciers. When the ice goes away, curved ridges stay behind.

<gallery class="center" widths="380px" heights="360px">

File:R0502109dorsaargentea.jpg|Possible eskers indicated by arrows. Eskers form under glaciers.

Wikilau.jpg|Lau Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Curved ridges are probably eskers which formed under glaciers.
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:ESP 018857 2225alpineglacier.jpg |Alpine glacier moving from a valley Lat: 42.2° N Long: 50.5° . Note how it spreads out when leaving the valley.

File: Wikielephantglacier.jpg|Glacier in Greenland Glacier spreads out when it leaves valley.
</gallery>

For Mars, a number of names have been applied to these glacier-like forms. Some of them are tongue-shaped glaciers, lobate debris aprons (LDA’s), lineated valley fill (LVF), and concentric crater fill (CCF).<ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref> <ref>Plaut, J. et al. 2008. Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars. Lunar and Planetary Science XXXIX. 2290.pdf</ref> <ref>http://hirise.lpl.arizona.edu/PSP_009535_2240</ref> <ref>Carr, M. 2006. The Surface of Mars. Cambridge University Press. ISBN|978-0-521-87201-0</ref> <ref>Squyres, S. 1978. Martian fretted terrain: Flow of erosional debris. Icarus: 34. 600-613.</ref> <ref>Levy,J. et al. 2007. Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars: Evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112</ref> <ref>Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.</ref>
<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185</ref>

<gallery class="center" widths="380px" heights="360px">

File:ESP 035327 2255tongues.jpg|Tongue-shaped glaciers These were made when a flow encountered an obstacle that made it split into two.
File:ESP 036619 2275ldalabeled.jpg|Lobate debris apron LDA) around a mound <ref>Baker, D., et al. 2009. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.</ref> <ref>Marchant, D. and J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars. Icarus: 192.187-222</ref> <ref>Dickson, J., et al. 2008. Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases. Geology: 36 (5) 411-415</ref> <ref>Kress, A., et al. 2006. The nature of the transition from lobate debris aprons to lineated valley fill: Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars. Lunar. Planet. Sci. 37. Abstract 1323</ref>
</gallery>

<gallery class="center" widths="380px" heights="360px">

File:30707946 10212010896087124 5214252926280663040 nccf.jpg|Concentric Crater Fill, as seen by CTX This crater was bowl shaped when formed; now it is full of ice and dust . <ref>Levy, J., J. Head, D. Marchant. 2010. Concentric Crater fill in the northern mid-latitudes of Mars: Formation process and relationships to similar landforms of glacial origin. Icarus 2009, 390-404.</ref> <ref>Levy, J., J. Head, J. Dickson, C. Fassett, G. Morgan, S. Schon. 2010. Identification of gully debris flow deposits in Protonilus Mensae, Mars: Characterization of a water-bearing, energetic gully-forming process. Earth Planet. Sci. Lett. 294, 368–377.</ref> <ref>http://hirise.lpl.arizona.edu/ESP_032569_2225</ref> <ref>Garvin, J., S. Sakimoto, J. Frawley. 2003. Craters on Mars: Geometric properties from gridded MOLA topography. In: Sixth International Conference on Mars. July 20–25, 2003, Pasadena, California. Abstract 3277.</ref>

File:Ccffigurecaptioned.jpg| The depth of craters can be predicted based upon the observed diameter. Many craters are now almost full, instead of having bowl shape; consequently, it is believed that they have added ice, dust, and other debris since they were formed. <ref>Dickson, J., et al. 2009. Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars: Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes. Earth and Planetary Science Letters.</ref> <ref>cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|author=|date=|website=hirise.lpl.arizona.edu</ref> <ref>Levy, J. et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial processes. Icarus: 202. 462-476.</ref>
</gallery>

[[File:ESP 052138 1435lvf.jpg|thumb|600px|center|Lineated valley fill, as seen by HiRISE under [[HiWish program]]]]

==Ice in the ground==

Mars has some unique landscapes and features that are common just to it. Since so much water is frozen in the ground and since the thin atmosphere of Mars allows ground ice to disappear when it became exposed, unreal scenes can develop. Under current conditions on Mars, ice sublimates when exposed to the air. In that process, ice goes directly to a gas instead of first melting. It often starts with small, narrow cracks that get larger and larger. Once ice leaves the ground there is not much left except dust. And winds will eventually carry the dust away. The end result is various shaped holes, pits, canyons, and hollows. Some of these forms are called brain terrain, ribbed terrain, hollows, scalloped terrain, and exposed ice sheets. <ref>Levy, J., et al. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> All of these may be of use to future colonists who need to find supplies of water.

[[File:45917 2220brainsopenclosed.jpg|Open an closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>]]

Open and closed brain terrain <ref >Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>

[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]

Ribbed terrain begins with cracks that eventually widen to produce hollows.

<gallery class="center" widths="380px" heights="360px">

File:46916 2270scallopsmerging.jpg|Scalloped terrain <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. 2009. "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research. 114 (E4). </ref> <ref> Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research: Planets. 112 (E6): E06010.</ref> <ref> Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. 2009. "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars" (PDF). Lunar and Planetary Science. 40. p. 2178, abstract 2178. </ref> <ref>Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus. 205 (1): 259. </ref>
PIA22078 hireswideview.jpg|Wide view of triangular depression The colored strip shows the part of the image that can be seen in color. The wall at the top of the depression contains pure ice. This wall faces the south pole. <ref>Supplementary Materials Exposed subsurface ice sheets in the Martian mid-latitudes Colin M. Dundas, Ali M. Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, Nathaniel E. Putzig, Donna Viola, Sarah Sutton, Erin Clark, John W. Holt</ref>

PIA22077 hirescloseblue.jpg|Close, color view of wall containing ice from previous image <ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice]. NASA Press Release. 11 January 2018.</ref> <ref>[http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars Ice cliffs spotted on Mars]. ''Science News''. Paul Voosen. 11 January 2018.</ref> <ref>Dundas, E., et al. 2018. Exposed subsurface ice sheets in the martian mid-latitudes. Science. 359. 199.</ref> <ref> http://spaceref.com/mars/steep-slopes-on-mars-reveal-structure-of-buried-ice.html</ref>
</gallery>

[[File: 46325 2225hollowsclose2.jpg|600pxr|Close view of hollowed terrain caused by ice leaving the ground Box shows size of football field.]]

Close view of terrain caused by ice leaving the ground Box shows size of football field.

Other signs of water ice in the ground are: lobed (rampart craters), patterned ground, and possible pingos. Pattered ground or polygonal ground is common in ice-rich areas on Earth.

<gallery class="center" widths="380px" heights="360px">

File:56942 1075icepolygonslabeled2.jpg|Polygons Ice is in the low troughs that lie between the polygons.<ref>https://www.uahirise.org/ESP_047247_1150</ref>

</gallery>

Pingos are mounds that contain a core of ice.<ref>http://www.uahirise.org/ESP_046359_1250</ref> <ref>Soare, E., et al. 2019.</ref> <ref> Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. https://doi.org/10.1016/j.icarus.2019.03.010</ref> They often have cracks on their surfaces. Cracks form when water freezes and expands. Pingos would be useful as sources of water for future colonies on the planet.

<gallery class="center" widths="380px" heights="360px">
51230 2200pingos.jpg|Close view of possible pingos Pingos contain a core of pure ice; they would be useful for a source of water by future colonists.
ESP 046359 1250-2pingoscale.jpg|Close view of possible pingo with scale, as seen by HiRISE under HiWish program
</gallery>

Craters with ejecta that look like they were made by an impact into mud are called lobed or rampart craters. They were discovered by early, orbital missions to Mars. They are most common where we expect ice in the ground.

<gallery class="center" widths="380px" heights="360px">
File:Mars rampart crater.jpg|Yuty Crater showing lobe and rampart morphology; it looks like mud was formed during the impact.

</gallery>

Channels are sometimes found in a crater's ejecta or along the edges of the ejecta. Heat from the ejecta probably melted ice in the ground. Much heat is produced with an impact.

<gallery class="center" widths="380px" heights="360px">
File:ESP 055530 2180channels.jpg

</gallery>

==Liquid water==

Mars used to have lots of water and maybe a much thicker atmosphere billions of years ago. With liquid water, life is possible. Indeed, life may have first appeared on Mars before it occurred on Earth. Martian organisms could have been knocked off Mars by low angle asteroid impacts and found their way to Earth. Perhaps, the DNA of all Earthly organisms, included us, still contains genes from early Martian life. When we have samples of Mars brought back to Earth, we may find traces of DNA that are like ours.
Data are still being gathered and ideas debated, but scientists think that once Mars cooled down and lost its magnetic field, the solar wind may have carried away much of its atmosphere. In addition, some researchers have suggested that some of the atmosphere was splashed out by impacts. After the planet cooled, water became frozen in the polar ice caps and in the ground. But, for some period there was liquid water.

[[File:Mars vs Earth Solar Wind-1024x576.png|Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field]]

Artist’s conception of how the solar wind strikes Mars, but does not reach the Earth’s surface because of the Earth’s magnetic field

[[File:Mavenargoninfographic2.jpg|This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.]]

This poster made by NASA shows the different ways that Mars lost most of its atmosphere after its magnetic field disappeared.

Huge amounts of water had to be present to carve the many outflow channels and produce the valley networks. Many of the outflow channels begin in "Chaos Terrain." Such a landscape often is where the ground seems to have just collapsed into giant blocks.<ref>https://marsed.asu.edu/mep/ice/chaos-terrain</ref> <ref>https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-9213-9_46-2</ref> It is believed that a shell of ice was created when the planet's climate cooled. Perhaps, at times the shell was broken by asteroid impacts, movements of magma, or faults. Such events would allow pressurized water to rapidly escape from under the shell of ice (shell has been called a cryosphere). Evidence is accumulating for the existence of an ocean. Lakes existed in low spots, especially craters.

[[File:ESP 056689 2210channelslowspotcropped.jpg |thumb|right|px||Channels that empty into a low area that could have been a lake Arrows show channels that lead to a low area that could have hosted a lake.]]

[[File:ESP 052677 2075streamlined.jpg |Streamlined forms in wide channel These forms were shaped by running water.]]

Streamlined forms in wide channel

These forms were shaped by running water.

<gallery class="center" widths="380px" heights="360px">

File:ESP 056800 1385channels.jpg|Crater with channels Arrows show channels that carried water into and out of crater.

File:Ravi Vallis.jpg|Ravi Vallis was formed when the ground released a great flood of water from Aromatum Chaos. Maybe it started when hot magma moved under the ground.

File:Ister Chaos.jpg|Ister Chaos Water may have come out of this landscape when the ground broke up into blocks.<ref>https://www.uahirise.org/hipod/PSP_008311_1835</ref>

File:Branched Channels from Viking.jpg|These valley networks look like they were made from precipitation.
</gallery>

At present, it is hotly debated just how long water stayed around. The sun was not as strong billions of years ago. Greenhouse gases like carbon dioxide, methane, and hydrogen may have made Mars warm enough for liquid water. Massive volcanoes would have given up many of these gases, along with water vapor.

[[File: Olympus Mons Side View.svg.png|thumb|left|300px|Height of Olympus Mons compared to tall mountains on Earth]]

Maybe the water just existed for short periods. Some studies have showed that large impacts into icy ground could release water and change the local climate for thousands of years. Also, impacts may have punctured an ice shell and allowed pressurized water to flow out for a time. Any water moving on the surface would quickly freeze at the top. But, it would continue to flow under the ice for a long time and make many of the channels we see today. Heat to allow water to flow may have been from underground flows of magma. On the other hand, many of the features created by liquid water could have formed under massive ice sheets where water was insulated from the Martian atmosphere.
 
==Layers==

Many locations display layered formations. Some are mostly just made of ice and dust. These types of layers are common in the polar ice caps, especially the northern ice cap.<ref>https://www.uahirise.org/hipod/PSP_008244_2645</ref> Other, rockier layers, are visible in the walls of impact craters and canyon walls.

<gallery class="center" widths="380px" heights="360px">

File:PSP 008244 2645northicecaplabeled.jpg|Layers in northern ice cap that are exposed along a cliff

File:ESP 054515 2595icecaplayers.jpg|Close view of many layers exposed in northern ice cap
File: 57080 1380layerscratercolor.jpg|Layers in crater wall in Phaethontis quadrangle, as seen by HiRISE under HiWish program
48980 1725layersclose2.jpg|Close view of layers in Louros Valles
</gallery>

And then there are layers that may be more recent, they may be connected to repeated climate changes. Some have regularity to them. The climate of Mars changes drastically due to changes in the tilt of its rotational axis. At times, like now, it is close to the Earth’s 23.5 degrees. But, at times it may be as much as 70 degrees.<ref> Schorghofer, Norbert (2008). "Temperature response of Mars to Milankovitch cycles". Geophysical Research Letters. 35 (18): doi:10.1029/2008GL034954.</ref> <ref>ouma | first1 = J. | last2 = Wisdom | first2 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | url = | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 |</ref> <ref>Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | url = | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 |</ref> Tilt governs the seasons and where ice is distributed. Currently, the largest deposit of ice is at the poles. At other times could have been at mid-latitudes. Imagine how it would be to have Pittsburgh under an ice cap. Mars may have had ice caps at the latitude of Pittsburgh.

<gallery class="center" widths="380px" heights="360px">

File:Mars Ice Age PIA04933 modest.jpg|How Mars may have looked with a greater tilt of Mars' rotational axis caused increased solar heating at the poles. This larger tilt would make a surface deposit of ice and dust down to about 30 degrees latitude in both hemispheres.
</gallery>

There is an ice-rich material that falls from the sky. It is called latitude dependent mantle.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref> It is thought to come from snow and ice-coated dust. At times, there is a lot of dust in the air. When that happens, moisture will freeze onto dust grains. When the ice-coated dust particle gets heavy enough, it will fall. Recent accumulations of this mantle look smooth. In some places the mantle is layered. Some formations, particularly in protected spots in craters and against mounds, suggest that these layered formations had many more layers. The wind sometimes shapes them into layered mounds.

[[File:54742 1485mantle.jpg|Mantle in a crater The mantle here has made everything look smooth on one side of the crater.]]

Mantle in a crater The mantle here has made everything look smooth on one side of the crater.
[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]

Layers in crater They were protected from erosion by being in the crater.

<gallery class="center" widths="380px" heights="360px">

File:ESP 035801 2210dipping.jpg|Layers leaning against a mound The mound protected them from erosion.
</gallery>

The older layers visible on crater and canyon walls may have different sources. Some are from lava flows or ash from volcanoes. Some may have formed under water like most layered sedimentary rocks on the Earth.<ref>https://www.uahirise.org/PSP_008391_1790</ref> Curiosity, our robotic explorer, has found that layers in Gale Crater were made from sediments at the bottom of a lake. Some may be just from dust and debris settling in low areas and then being cemented by rising groundwater carrying minerals like sulfates and silica.<ref> Rates and mechanisms of chemical weathering of ferromagnesian silicate minerals on Mars | date = 1993 | last1 = Burns | first1 = Roger G | journal = Geochimica et Cosmochimica Acta | volume = 57 | issue = 19 | pages = 4555–4574 |</ref> <ref>{{cite journal | doi = 10.1029/92JE02055 | title = Rates of Oxidative Weathering on the Surface of Mars | date = 1993 | last1 = Burns | first1 = Roger G. | last2 = Fisher | first2 = Duncan S. | journal = Journal of Geophysical Research | volume = 98 | issue = E2 | pages = 3365–3372 |</ref> <ref>Hurowitz | first1 = J. A. | last2 = Fischer | first2 = W. W. | last3 = Tosca | first3 = N. J. | last4 = Milliken | first4 = R. E. | year = 2010 | title = Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars | url = https://authors.library.caltech.edu/18444/2/ngeo831-s1.pdf| journal = Nat. Geosci. | volume = 3 | issue = 5| pages = 323–326 | doi = 10.1038/ngeo831 | </ref> Sometimes a crater may have been filled up with layered rocks and then the rocks may have been eroded by the wind in such a way to just leave a layered mound in the center of the crater. Gale crater, where Curiosity is exploring, was like that.

<gallery class="center" widths="380px" heights="360px">

Image:Topographic Map of Gale Crater.jpg|Gale Crater with Aeolis Mons rising from the center. The noted [[Curiosity]] landing area is near Peace Vallis in Aeolis Palus. Curiosity landed in the northern part of the crater. Colors indicate elevation.

File:Marscratermounds.jpg|Some layers form mounds in the center of craters. They could have been made by the erosion of layers that were deposited after the impact.

</gallery>

[[File:8021 mars-curiosity-rover-msl-rock-layers-PIA21043-full2murray.jpg|600pxr|Rock layers in the Murray Buttes area in lower Mount Sharp They look like rocks formed at the bottom of lakes and their chemistry proves it.]]

Rock layers in the Murray Buttes area in lower Mount Sharp

==Igneous effects==

[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]

Volcanic vent with lava channel

<gallery class="center" widths="380px" heights="360px">
File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons

</gallery>

Igneous refers to rock that is heated to a molten condition. On Mars, this is a major shaper of landscapes. Lava comes out of the ground at holes called vents. Flows of lava can be about as fluid as water and move long distances. Sometimes the top cools to a solid, but the liquid rock continues to flow underneath a hard crust. Giant pieces of this stiff crust can move around as “lava rafts.”

<gallery class="center" widths="380px" heights="360px">

File:ESP 054891 2040lavarafts.jpg|Lava rafts
</gallery>

In other places, lava travels in channels. When they make a hard crust, lave tunnels are created. A picture below shows lava tunnels.<ref> https://www.uahirise.org/PSP_009501_1755</ref> After the liquid lava moves away, an empty tunnel can be formed. These are significant for future colonists as they may be where our first colonies will be built. There people would be protected from surface radiation. We have already found spots that might be openings to these tunnels in HiRISE images.

[[File:PSP 009501 1755lavatube.jpg |Lava tubes and lava tunnels Future colonists may live in lava tunnels.]]

[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|left|Possible cave entrance to a lava tunnel Future colonies may live in caves for protection from weather and radiation.]]

[[File:Tharsis mons Viking.jpg |right|thumb|px|Some of the Martian volcanoes, as seen by Viking 1]]

There are huge volcanoes that were noticed by our first spacecraft to orbit the planet. The first satellite to orbit the planet was only able to see a few volcanoes peeking above a massive global dust storm. Since Mars has not had plate tectonics for nearly all of its history, volcanoes can grow very large.<ref>https://www.jpl.nasa.gov/edu/learn/video/mars-in-a-minute-how-did-mars-get-such-enormous-mountains/</ref> Lava and ash can erupt from the same spot for long periods of time. On the Earth, the plates move so volcanoes can only grow so big.

<gallery class="center" widths="380px" heights="360px">

File:Olympus Mons alt.jpg|Olympus Mons, tallest volcano in solar system The mass of volcanoes on mars stretches and cracks the crust causing faults.

</gallery>

Volcanoes are only the surface manifestations of liquid rock. There is more molted rock moving under the surface than what we see above ground in volcanoes. Molted rock is called magma when underground. Stretching out around volcanoes underground are various structures. Vast linear walls, called dikes radiate out from volcanoes. On Mars they can be many miles in length. Many form by moving along cracks or weak parts of rocks. Some scientists have suggested that they from long troughs when they melt ground ice. Troughs are some of the longest features on Mars.

<gallery class="center" widths="380px" heights="360px">
File:ESP 045981 2100dike2.jpg|Dike Notice how straight it is. Magma moved along underground and then rose up along a fault. Afterwards, softer material eroded and left the harder dike behind.

</gallery>

Besides the direct action of lava and magma, volcanoes affect Mars with just their weight. The mass of a volcano stretches the crust and makes cracks form. The large canyon system of Valles Marineris may have been started with some sort of stretching of the crust. But, its stretching may have been caused by rising mantle plumes or maybe the rise of Tharsis where so many volcanoes are located.<ref>https://astronomy.com/magazine/ask-astro/2013/08/valles-marineris</ref> Cracks in the crust are called faults. Faults on Mars are often double faults. A center section is lower than the sides. This arrangement is called a graben. On the Earth they can turn into lakes like Lake George in New York State. Graben on Mars can be thousands of miles long.

<gallery class="center" widths="380px" heights="360px">

File:Troughs in Elysium Planitia.jpg|Troughs showing layers The center section of the picture is in color. With HiRISE only a strip in the middle is in color. These troughs are in Cerberus Fossae, as seen by HiRISE under the HiWish program. Location is 15.819 N and 161.448 E. Cerberus Fossae is the source of most of the Marsqukes detected by the InSight mission.

ESP 046251 2165graben.jpg|Straight trough is a fossa that would be classified as a graben. Curved channels may have carried lava/water from the fossa. Picture taken with HiRISE under [[HiWish program]].

File:ESP 057834 2005troughmesa.jpg|Trough or graben cutting through mesa
</gallery>

Sometimes lava moves over frozen ground. That results in steam explosions. Large fields of small cones can be produced when this happens. Those cones are called “rootless cones” since they do not go down very far.

<gallery class="center" widths="380px" heights="360px">

File:ESP 045384 2065lavaice.jpg|Wide view of large field of rootless cones
File:45384 2065cones2.jpg|Close view of rootless cones
</gallery>

Volcanoes sometimes explode with great amounts of ash that travels long distances, covering everything. Some of the layers seen on Mars are probably from these ash deposits. These deposits do not contain boulders and are easily eroded by just the wind. Two areas on Mars have widespread and thick deposits made in this way; they are called the Medusae Fossae Formation and the Electris deposits. These relatively soft deposits often form shapes called yardangs. They are sort of boat shaped and show the direction of the prevailing wind when they were created.

<gallery class="center" widths="380px" heights="360px">

File:61167 1735yardangs3.jpg|Yardangs
</gallery>

Much of the atmosphere of Mars came from volcanoes. Volcanoes give off large amounts of carbon dioxide and water, along with other chemicals. Some of these chemical compounds are “greenhouse gases” that served to heat up early Mars.
A few places are thought to be where volcanoes erupted under ice. The shapes that resulted look like those made on Earth when a volcano erupted under the ice.

[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.]]

Large group of concentric cracks Location is [[Ismenius Lacus quadrangle]]. Cracks were formed by a volcano under ice.

==Bright dust==

A thin coating of bright-toned dust covers almost all parts of Mars. It has a rust brown color. It is not too noticeable until it is not here. Some things remove the dust and then reveal the dark underlying surface. The contrast between this thin coating and the underlying dark rock is striking. Much of the difference derives from how NASA pictures are processed.<ref> Sullivan, R. et al. 2001. Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref> To bring out more detail, the brightest tone is considered white, while the darkest black. It only takes a very thin layer of dust to make a difference in the over-all appearance of a picture. Experiments on Earth found that the layer may be only as thick as the diameter of a human hair.<ref> https://en.wikipedia.org/wiki/Micrometre
</ref> Incidentally, the dust has the color of rust because it is rust—it is oxidized iron.

Dark slope streaks occur when bright dust avalanches down steep slopes like crater walls. They can be very long and elaborate. These movements are affected by obstacles like boulders. A streak may split into two when encountering a boulder. They may be initiated when an impact happens nearby.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars" ''Icarus'' 2012; 217 (1) 194 </ref><ref>http://redplanet.asu.edu/</ref>
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>

[[File:ESP 043128 2005mesastreaks.jpg|600pxr|Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]]]

Dark slope streaks on layered mesa

[[File:55107 1930streaksboulders2.jpg|thumb|500px|right|Dark slope streaks As these streaks moved down, boulders changed their appearance.]]

<gallery class="center" widths="380px" heights="360px">

</gallery>

Another thing that causes light and dark patterns is a dust devil. These miniature tornadoes remove the bright dust and make straight and/or curved tracks. They are common especially in areas with much dust cover and at certain times of the day. They have been observed both from orbit and from the ground.<ref>https://www.uahirise.org/ESP_042201_1715</ref> We even have movies of them in action. They can form beautiful scenes. And, the arrangement of the tracks can be different in just a few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>

[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]

<gallery class="center" widths="380px" heights="360px">
</gallery>

The atmosphere of Mars contains a great deal of fine dust. Large dust storms happen just about every Martian year. A year on Mars is about 23 of our months. Dust storms typically occur when it is spring or summer in the southern hemisphere. At that time, Mars is at its closest to the sun. Unlike the Earth, Mars has a very elliptical orbit which brings it much closer to the sun than at other times. This makes for differences in season both in intensity and length. For example the southern summer is much shorter than that of the north. However, the summer season in the southern hemisphere is much more intense.

[[File:Marsorbitsolarsystem.gif|Comparrsion of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle.<ref> https://www.compadre.org/osp/items/detail.cfm?ID=9757</ref> <ref> https://www.compadre.org/osp/items/detail.cfm?ID=7305</ref>]]

Comparison of the orbits of Earth and Mars. The Earth’s orbit is almost a perfect circle. Mars changes its distances to sun a great deal--this changes makes drastic seasonal changes.

==Dry Ice==

Some of the strangest things on Mars involve dry ice—solid carbon dioxide. The cold conditions on Mars cause much of the carbon dioxide to freeze out of the atmosphere. Both ice caps contain some dry ice. Each year about 25% of the atmosphere freezes out onto the poles. This is so much that the gravity of the planet shifts. <ref>NASA/Goddard Space Flight Center. "New gravity map gives best view yet inside Mars." ScienceDaily. ScienceDaily, 21 March 2016. https://www.sciencedaily.com/releases/2016/03/160321154013.htm.</ref> <ref>Antonio Genova, Sander Goossens, Frank G. Lemoine, Erwan Mazarico, Gregory A. Neumann, David E. Smith, Maria T. Zuber. Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science. Icarus, 2016; 272: 228 DOI: 10.1016/j.icarus.2016.02.05</ref> Winds and weather systems that almost look like the Earth’s are produced by so much dry ice changing to a gas at these times.

[[File:PIA00190-MC-30-MareAustraleRegion-19980605.jpg |right|thumb|px| Region of South Pole with ice cap Southern ice cap is much smaller than the North’s.]]

[[File:Mars NPArea-PIA00161.jpg |left|thumb|px| Spiral troughs in the northern ice cap]]

<gallery class="center" widths="380px" heights="360px">

File:Marscyclone hst.jpg|Cyclone on Mars, as seen by HST
</gallery>

In the winter dry ice accumulates. So, large areas appear white. When things warm up in the spring, the landscape gets many dark spots and areas. <ref>https://mars.jpl.nasa.gov/mgs/msss/camera/images/dune_defrost_6_2001/</ref><ref>SPRING DEFROSTING OF MARTIAN POLAR REGIONS: MARS GLOBAL SURVEYOR MOC AND TES MONITORING OF THE RICHARDSON CRATER DUNE FIELD, 1999–2000. K. S. Edgett, K. D. Supulver, and M. C. Malin, Malin Space Science Systems, P.O. Box 910148, San Diego, CA 92191-0148, USA.</ref> <ref>K.-Michael Aye, K., et al. PROBING THE MARTIAN SOUTH POLAR WINDS BY MAPPING CO2 JET DEPOSITS. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2841.pdf</ref> In the past, observers thought that Mars was full of life. They saw the northern ice cap get smaller and smaller. At the same time, they watched the area get darker. They concluded that the darkening was vegetation growing from the water coming out of the ice caps. What was happening was the dry ice was disappearing. Today, we can watch this darkening occur in great detail. <ref>http://www.jpl.nasa.gov/news/news.php?release=2013-034</ref>

<gallery class="center" widths="380px" heights="360px">

43821 2555defrostingdune2.jpg|Defrosting surface Frost is disappearing in patches from a dune and from the surrounding surface. Note: the north side (side near top) has not defrosted because the sun is coming from the other side.

File:ESP 011605 1170defrosting.jpg|Defrosting The dark spots are where the ice has gone. We now can see the underlying dark surface.

</gallery>

In some places, there are many geyser-like eruptions of gas and dark dust.<ref>https://www.uahirise.org/</ref> High pressure gas and dust explode out of the ground. Winds often blow these eruptions into dark plumes. After many observations, scientists concluded that what happens is that a transparent-translucent dry ice slab forms in the winter. With increased sun in the spring, pressure builds up under this slab as light heats cavities under the slab and causes dry ice to turn into a gas. At weak areas in the slab, the gas comes out along with dark dust.<ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> The channels may get dark from the dust and make a pattern that looks like a spider. These patterns are called “spiders.” <ref>http://mars.jpl.nasa.gov/multimedia/images/2016/possible-development-stages-of-martian-spiders</ref> <ref>http://spaceref.com/mars/growth-of-a-martian-trough-network.html</ref> <ref>Benson, M. 2012. Planetfall: New Solar System Visions</ref> <ref>http://www.astrobio.net/topic/solar-system/mars/spiders-invade-mars/</ref> <ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>Portyankina, G., et al. 2017. Present-day erosion of Martian polar terrain by the seasonal CO2 jets. Icarus: 282, 93-103.</ref> The official name for spiders is "araneiforms."<ref>Portyankina, G., et al. 2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>

<gallery class="center" widths="380px" heights="360px">

File:Spiders2eruptionlabeled2.jpg|Drawing showing the cause of plumes and spiders. In the spring, sunlight goes through a clear slap of dry ice. It heats up the dark ground. Heat causes dry ice to turn into a gas and pressurize. When pressure is great enough a dark plume of carbon dioxide gas and dark dust erupt. Wind will form it into a fan shape plume.

</gallery>

[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]

Close view of spiders

<gallery class="center" widths="380px" heights="360px">

ESP 048845 1010spiders.jpg|Wide view of crater that contains examples of spiders
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program
</gallery>

Around the southern cap, dry ice makes round, low areas that look like Swiss cheese. <ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
South polar residual cap of Mars: features, stratigraphy, and changes
Icarus, 174 (2 SPEC. ISS.). 2005. pp. 535–559. http://doi.org/10.1016/j.icarus.2004.07.028</ref> <ref>Thomas, P., P. James, W. Calvin, R. Haberle, M. Malin. 2009. Residual south polar cap of Mars: stratigraphy, history, and implications of recent changes
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes. 2013. Time scales of erosion and deposition recorded in the residual south polar cap of mars
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee. 2016. Mass balance of Mars’ residual south polar cap from CTX images and other data
Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> So, it is called “Swiss cheese terrain.” The roundness of the pits is believed to be related to the low angle of the sun.<ref>Buhler, Peter, Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head. 2017. How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats. Icarus: 286, 69-9.</ref>

[[File:South Pole Terrain.jpg|600pxr|HiRISE view of South Pole Terrain.]]
HiRISE view of South Pole Terrain.

<gallery class="center" widths="380px" heights="360px">
</gallery>

The ice caps contain a great deal of water ice. The northern cap has a covering of dry ice only 1 meter thick in the winter, but the southern cap always has a coating of dry ice up to 8 meters thick. Large deposits of dry ice are also buried in the water ice of the cap at some locations.

<gallery class="center" widths="380px" heights="360px">
</gallery>

==Gullies==

Since 2000, researchers have been studying gullies that are common in the mid-latitudes on steep slopes. They look like they were carved by liquid water. After many years of observations, it has been concluded that today they are being made by chunks of dry ice sliding down slopes.<ref>Vincendon, M. 2015. JGR:120, 1859–1879.</ref> <ref> Pilorget | first1 = C. | last2 = Forget | first2 = F. | year = 2016 | title = Formation of gullies on Mars by debris flows triggered by CO2 sublimation | url = | journal = Nature Geoscience | volume = 9 | issue = | pages = 65–69 | doi = 10.1038/ngeo2619 | </ref> <ref>Schorghofer, N., K. Edgett. 2005. Seasonal surface frost at low latitudes on Mars. Icarus: 180, 321-334.</ref> However, some scientists concede that water may have been involved in their formation in the past.<ref>Harrington |first=J.D. |last2=Webster |first2=Guy |title=RELEASE 14-191 – NASA Spacecraft Observes Further Evidence of Dry Ice Gullies on Mars |url=http://www.nasa.gov/press/2014/july/nasa-spacecraft-observes-further-evidence-of-dry-ice-gullies-on-mars |</ref> <ref>CNRS. "Gullies on Mars sculpted by dry ice rather than liquid water." ScienceDaily. ScienceDaily, 22 December 2015. www.sciencedaily.com/releases/2015/12/151222082255.htm</ref> <ref>http://www.skyandtelescope.com/astronomy-news/martian-gullies-triggered-by-exploding-dry-ice-122320158</ref>

<gallery class="center" widths="380px" heights="360px">

ESP 047956 1420gullies.jpg|Crater with gullies, as seen by HiRISE under HiWish program
File:47395 1415gullycurvedchannels.jpg|Gullies Curved channels were thought to need running water to form.
</gallery>

[[File:Gullies near Newton Crater.jpg|600pxr|Gullies near Newton Crater]]
Gullies near Newton Crater

==Other features==

The surface of Mars is very old—billions of years. This is plenty of time for rocks to have broken down into sand. In low places, like crater floors, sand accumulates and makes dunes. Some are quite pretty. And the colors used by NASA make them even more pretty—they can appear blue, purple, green, or turquoise.

[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]

Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>

[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]

<gallery class="center" widths="380px" heights="360px">

File:61974 1710dunesrgb2.jpg|Dunes
File:ESP 046378 1415dunefield.jpg|Black and white, wide view of dunes
File:ESP 55095 2170dunes.jpg|Dunes near Sklodowski Crater in North Arabia Terra
</gallery>

Related to dunes are something called transverse aeolian ridges (TAR’s). They look like small dunes. They are often parallel to each other. They generally are in low areas and one of the most common landforms on Mars.<ref>http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1598.pdf|format=PDF|type=conference paper|title=Investigations of transverse aeolian ridges on Mars|first1=Daniel C.|last1=Berman|first2=Matthew R.|last2=Balme|year=2012|publisher=Lunar and Planetary Science Conference</ref> They are mid-way in height between dunes and ripples; they are not well understood.<ref>http://www.uahirise.org/ESP_042625_1655</ref> <ref>Berman, D., et al. 2018. High-resolution investigations of Transverse Aeolian Ridges on Mars: Icarus: 312, 247-266.</ref>

<gallery class="center" widths="380px" heights="360px">

File:64038 2155tarslabeled.jpg|Transverse Aeolian Ridges, as seen by HiRISE under HiWish program

File:ESP 039563 1730tars.jpg|Transverse Aeolian Ridges (TAR’s) between yardangs We do not totally understand these.
File:ESP 042625 1655tars.jpg|Wide view of Transverse Aeolian Ridges (TAR’s) near a channel
</gallery>

Some landscape expressions are mysteries.<ref>Pascuzzo, A., et al. 2019. The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
Implications for extensive subsurface channelized fluid flow in the Noachian. Icarus: 319, 852-868</ref>

In rocks of certain ages, often at the bottom of low spots are complex arrangements of ridges.
These are walls of rock.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>

There are different ideas for what caused them. Over 14,000 people from around the world helped map them, so that scientists could better understand them. The team of volunteers found 952 polygonal ridge networks in an area that measures about a fifth of Mars’ total surface area. Some ridges contain clays, so water may have been involved in their formation because clays need water to be formed.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al. 2022. Irregular polygonal ridge networks in ancient Noachian terrain on Mars. Icarus. 374. 114833</ref>

[[File:ESP 036745 1905top.jpg|600pxr|Linear ridge networks]]
Linear ridge networks

<gallery class="center" widths="380px" heights="360px">

File:ESP 048236 2105ridgeswide.jpg|Wide view of linear ridge network Location is Casius quadrangle.
File:48236 2105ridges2.jpg|Close view of linear ridge network Location is Casius quadrangle.
</gallery>

[[File:Ridgesmappedbycitizens.jpg|600pxr|Map of Linear ridge networks]]

Map of Linear ridge networks

Of eerie beauty are odd arrangements visible on the bottom of the Hellas Impact basin. We are not sure exactly what caused them. They have been called honeycomb terrain or banded terrain.

[[File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin. The exact origin of these shapes is unknown at present.]]

Wide view of features on floor of Hellas impact basin.

[[File:55146 1425hellascenter.jpg|Close view of center of a Hellas floor feature]]

Close view of center of a Hellas floor feature

[[File: ESP 033995 1410bands.jpg|600pxr|Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE]]
Close-up of banded terrain on the floor of the Hellas basin, as seen by HiRISE

[[File:ESP 055067 1420ridgenetwork.jpg|600pxr|Floor features in Hellas Planitia]]

Honeycomb terrain on floor of Hellas Basin The exact origin of these shapes is unknown at present.

<gallery class="center" widths="380px" heights="360px">

</gallery>

Mars is one planet that we can see the surface clearly. Its super thin atmosphere (about 1% of the Earth’s) makes it easy to observe. Early telescopes revealed many markings and patterns. As we sent better and better cameras to examine it, more mysteries and more beautiful scenes emerged. We were able to answer many questions, but always more questions arose concerning what we were seeing.

<gallery class="center" widths="380px" heights="360px">

</gallery>

==References==

{{reflist|colwidth=30em}}

== External links ==

* [https://www.youtube.com/watch?v=D-SCOHj8u-A Water on Mars - James Secosky - 2021 Mars Society Virtual Convention -- Tells where water was and where ice is today on Mars (34 minutes)]

* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]

* https://mail.google.com/mail/u/0/?tab=wm&pli=1#inbox/FMfcgzGrbHtSWzJjdRzftxgXCrbxXNnK Water on Mars - A Literature Review" by Mohammad Nazari-Sharabian

* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]

* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]

*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program] Shows nearly all major features discovered on Mars. This would be good for teachers covering Mars.

*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]

*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]

*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]

* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]

* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=RYG-HLr33CM Martian Geology - Jim Secosky - 16th Annual International Mars Society Convention]
*[https://www.youtube.com/watch?v=ZNTNzQy1_UA Walks on Mars - Jim Secosky - 16th Annual International Mars Society Convention]

*[https://www.youtube.com/watch?v=jcaawA7d0ro Sublimation of Dry Ice]

* [https://www.youtube.com/watch?v=NiT02piO40c The Geological History of Water on Mars and Astrobiological Implications (Vic Baker)]

* [https://www.youtube.com/watch?v=z6B742f8yPs Mars Bunker: Martian Ice Revealed]

* [https://www.youtube.com/watch?v=RWNXJk0Y01k The Evolution of Water on Mars]

==See Also==

*[[Geography of Mars]]
*[[Glaciers on Mars]]
*[[High Resolution Imaging Science Experiment (HiRISE)]]
*[[Layers on Mars]]
*[[Martian features that are signs of water ice]]
*[[Martian gullies]]
*[[Rivers on Mars]]
*[[Sublimation]]
*[[Sublimation landscapes on Mars]]

==Recommended reading==

*Grotzinger, J., R. Milliken (eds.). 2012. Sedimentary Geology of Mars. Tulsa: Society for Sedimentary Geology.
*Kieffer, H., et al. (eds) 1992. Mars. The University of Arizona Press. Tucson
*[https://history.nasa.gov/SP-4212/ch11.html history.nasa.gov/SP-4212/ch11]
* Lorenz, R. 2014. The Dune Whisperers. The Planetary Report: 34, 1, 8-14
* Lorenz, R., J. Zimbelman. 2014. Dune Worlds: How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.