Difference between revisions of "HiWish program"

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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>  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> Over 12,000 suggestions were made by the public; suggestions were made for targets in each of the 30 quadrangles of Mars.  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>
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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==
 
==Landslides==
  
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. 
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[[File:ESP 057191 2150landslidecropped.jpg|Landslide]]
  
<gallery class="center" widths="190px" heights="180px" >
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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.
 
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<gallery class="center" widths="380px" heights="360px">
File:ESP 057191 2150landslidecropped.jpg|Landslide
 
 
File:ESP 045981 1585landslide.jpg|Landslide
 
File:ESP 045981 1585landslide.jpg|Landslide
 
File:ESP 043963 1550landslide.jpg|Landslide
 
File:ESP 043963 1550landslide.jpg|Landslide
 
</gallery>
 
</gallery>
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==Hollows==
 
==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.
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[[File:28207 2250hollowsarrows.jpg|Hollows]]
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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.
 
The mantle covers wide expanses.  It has a smooth appearance.  It covers the irregular, created surface of the planet.
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
  
File:28207 2250hollowsarrows.jpg|Hollows
 
 
File:46325 2225hollows4.jpg|Hollows
 
File:46325 2225hollows4.jpg|Hollows
  
 
File:ESP 046325 2225hollowsmiddlelabeled.jpg|Hollows
 
File:ESP 046325 2225hollowsmiddlelabeled.jpg|Hollows
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File:Close view of hollows created when ice left the ground. 03.jpg|Close view of hollows.  Narrow ridges were made when hollows kept expanding.
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File:Close view of hollows created when ice left the ground.jpg|Close, color view of hollows.  The HiView program was used in the rgb color scheme.
  
 
</gallery>
 
</gallery>
  
 
==Mud Volcanoes==
 
==Mud Volcanoes==
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[[File:Mud volcanoes from around Mars 11.jpg|600pxr|Mud volcanoes from around Mars]]
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                                  Mud volcanoes from around Mars
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[[File:53381 2265mud.jpg|Mud volcanoes]]
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Mud volcanoes  They may have come through a zone of weakness in the rock here
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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>
 
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="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:570770 2100coneslabeled.jpg|Mud volcanoes
 
File:570770 2100coneslabeled.jpg|Mud volcanoes
File:53381 2265mud.jpg|Mud volcanoes  They may have come through a zone of weakness in the rock here.
 
  
 
File:52050 2200mudvolcanoes.jpg|Mud volcanoes
 
File:52050 2200mudvolcanoes.jpg|Mud volcanoes
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==Volcanic vents==
 
==Volcanic vents==
<gallery class="center" widths="190px" heights="180px" >
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File:30348 1925vent2.jpg|Volcanic vent with lava channel
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[[File:30348 1925vent2.jpg|Volcanic vent with lava channel]]
</gallery>
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                      Volcanic vent with lava channel
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[[File:ESP 030440 1945ventcropped.jpg|Volcanic vent]]
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                        Volcanic vent
  
 
==Lava Flows==
 
==Lava Flows==
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[[File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons]]
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                                Lava flow on Olympus Mons
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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>
 
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="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
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File:44828 2030lavaflow.jpg|Lava flows  These are common in large sections of Mars.
  
File:ESP 056023 1965lavaolympus.jpg|Lava flow on Olympus Mons
 
 
File:ESP 044840 1620lavaflow.jpg|Lava flow
 
File:ESP 044840 1620lavaflow.jpg|Lava flow
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File:WikiESP 035095 1975lavalobestharsiswide.jpg|Old and young lava flows
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File:68460 1945laveolympus.jpg|Lava flowing down a slope from [[Olympus Mons]]
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File:68460 1945lavechannel.jpg|Lava channel from Olympus Mons
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</gallery>
 
</gallery>
  
 
==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="190px" heights="180px" >
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[[File:40162 2065conesarrows2.jpg|Rootless cones ]]
File:40162 2065conesarrows2.jpg|Rootless cones
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                                                Rootless cones
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Rootless Cones are thought to be caused by lava flowing over ice or ground containing ice.<ref>https://www-sciencedirect-com.wikipedialibrary.idm.oclc.org/science/article/pii/S0019103523000507</ref> <ref> Czechowski, L., et al.  2023.  The formation of cone chains in the Chryse Planitia region on Mars and the thermodynamic aspects of this process.  Icarus:  Volume 396, 15 May 2023, 115473</ref>  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.
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<gallery class="center" widths="380px" heights="360px">
  
 
File:45384 2065cones2.jpg|Rootless cones
 
File:45384 2065cones2.jpg|Rootless cones
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==Dikes==
 
==Dikes==
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. 
 
  
<gallery class="center" widths="190px" heights="180px" >
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[[File:ESP 045981 2100dike2.jpg|Dike]]
  
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.
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</gallery>
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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.
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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.
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[[File:ESP 046403 2095dikecropped.jpg|thumb|400px|center|Dike in [[Syrtis Major quadrangle]]]]
  
 
==Troughs==
 
==Troughs==
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[[File:ESP 051781 2035troughs.jpg |Troughs]]
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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>
 
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="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
File:ESP 051781 2035troughs.jpg|Troughs
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File:56910 2100trough.jpg|Group of troughs
 
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: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.
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File:ESP 057834 2005troughmesa.jpg|Troughs cutting through mesa, as seen by HiRISE under HiWish program
 
</gallery>
 
</gallery>
  
 
==Faults==
 
==Faults==
Faults are visible in some parts of Mars.  They are most noticeable in places where many layers exist.  Sometimes their presence is know because they can change the direction of stream channels.
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Faults are visible in some parts of Mars.<ref> https://www.uahirise.org/ESP_052893_1835</ref> 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]]
 
[[File:Wikiesp 039404 1820landingfir.jpg|Layers and fault in Firsoff Crater|600pxr|Layers and fault in Firsoff Crater]]
  
<gallery class="center" widths="190px" heights="180px" >
 
  
File:60331 1880faultslabeled2.jpg|Faults in layered terrain
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Layers and fault in Firsoff Crater
File:27615 1880faults.jpg|Faults in layered terrain
 
  
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[[File:60331 1880faultslabeled2.jpg|thumb|300px|left|Faults in layered terrain]]
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[[File:27615 1880faults.jpg|thumb|300px|center|Faults in layered terrain]]
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[[File:71634 1880layersfaultslabeled.jpg|thumb|300px|Faults in layers in Danielson Crater]]
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<gallery class="center"  widths="380px" heights="360px">
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File:26086 1800fault.jpg|Fault that changed direction of stream.  CTX image is included for context.
  
 
</gallery>
 
</gallery>
  
 
==Mesas and layers==
 
==Mesas and layers==
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[[File:Layered hills around Mars 21.jpg|600pxr|File:Layered hills around Mars]]
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                      Layered hills around Mars
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[[File:58788 1890layerscolorlabeled2.jpg|Mesa with layers]]
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                        Mesa with layers
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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.
 
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="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:58563 2225mesa.jpg|Mesa
 
File:58563 2225mesa.jpg|Mesa
  
 
File:58524 1820layerscolor4labeled.jpg|Mesa with layers
 
File:58524 1820layerscolor4labeled.jpg|Mesa with layers
  
File:58788 1890layerscolorlabeled2.jpg|Mesa with layers visible
 
  
 
File:58919 1935mesalayers.jpg|Mesa with layers  Box is the size of a football field.
 
File:58919 1935mesalayers.jpg|Mesa with layers  Box is the size of a football field.
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==Layers in Craters==
 
==Layers in Craters==
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[[File:61161 2210pyramidcraterlabeled.jpg|Mesa in crater with layers]]
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            Layers in crater  They were protected from erosion by being in the crater.
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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.
 
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="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
 
File:61161 2210pyramidcraterlabeled.jpg|Layers in crater  They were protected from erosion by being in the 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: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>
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==Dipping Layers==
 
==Dipping Layers==
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.
 
  
<gallery class="center" widths="190px" heights="180px" >
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[[File:46180 2225dippinglayers.jpg|Dipping layers and brain terrain (right side of picture)]]
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              Dipping layers and brain terrain (right side of picture)
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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.  Another idea for their origin was presented at 55th LPSC (2024) by an international team of researchers.  They suggest that the layers are from past ice sheets.<ref>Blanc, E., et al.  2024.  ORIGIN OF WIDESPREAD LAYERED DEPOSITS ASSOCIATED WITH MARTIAN DEBRIS COVERED GLACIERS.  55th LPSC (2024).  1466.pdf</ref> 
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[[File:ESP 038002 1375dipping.jpg|thumb|300px|left|Wide view of dipping layers against slopes]]
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[[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.]]
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<gallery class="center" widths="380px" heights="360px">
  
File:46180 2225dippinglayers.jpg|Dipping layers and brain terrain (right side of picture)
 
 
File:ESP 035801 2210pyramidsismenius.jpg|Dipping layers against a mesa wall.
 
File:ESP 035801 2210pyramidsismenius.jpg|Dipping layers against a mesa wall.
File:ESP 019778 1385pyramid.jpg|Set of dipping layers in crater
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File:ESP 062082 2175dippingcropped.jpg|Dipping layers  These may be the remains of past layers of mantle that covered the whole area.
+
</gallery>
File:ESP 038002 1375dipping.jpg|Wide view of dipping layers against slopes
+
 
 +
[[File:ESP 019778 1385pyramid.jpg|Set of dipping layers in crater]]
 +
 
 +
 
 +
                                  Set of dipping layers in crater
 +
 
 +
<gallery class="center"  widths="380px" heights="360px">
 +
 
 +
File:Dipping layers in HiRISE image ESP 080402 2240 01.jpg| Wide view of dipping layers, as seen by HiRISE under the HiWish program.  The dark strip is where a computer problem is preventing the gathering of data.
 +
 
 +
File:Dipping layers in HiRISE image ESP 080402 2240 02.jpg|Group of dipping layers. Each layer represents a change in the Martian climate.
 +
 
 +
File:Dipping layers in HiRISE image ESP 080402 2240 03.jpg|Remaining parts of a group of dipping layers.  Erosion has removed most of the material.
 +
 
 +
File:Dipping layers in HiRISE image ESP 080402 2240 05.jpg|Close view of dipping layers that show the thin nature of the layers.
 +
 
 
</gallery>
 
</gallery>
  
 
==Boulders==
 
==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.  
 
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="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
+
File:Boulder track down crater wall ESP 081601 1615.jpg|Boulder rolled down crater wall and left a track
File:28497 2250boulderslabeled.jpg|Boulders near hollows
 
  
 
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: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:58904 2240brainsboulders.jpg|Boulders and brain terrain
 
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas  Box shows size of football field.
 
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
 
File:ESP 045415 2220boulders.jpg|Color view of boulders
  
File:59458 2145boulders.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]]
  
</gallery>
+
                                  Boulders formed from break up of a mesa
  
 
==Yardangs==
 
==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>
 
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="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
File:61167 1735yardangs.jpg|Yardangs
+
 
 
File:61167 1735yardangs3.jpg|Yardangs
 
File:61167 1735yardangs3.jpg|Yardangs
 
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
 
File:ESP 045831 1750yardangswide.jpg|Wide view of yardangs in Amazonis quadrangle
 
File:ESP 047915 1815yardangs.jpg|Wide view of yardangs
 
File:ESP 047915 1815yardangs.jpg|Wide view of yardangs
 
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs
 
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs
 +
 +
File:Wide view of field of yardings.jpg|Wide view of yardangs in Arabia quadrangle
 +
File:ESP 061610 1895yardangsclose.jpg|Close view of yardangs, these features are shaped by the wind.
 
</gallery>
 
</gallery>
  
 
==Ring-Mold Craters==
 
==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.
 
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="190px" heights="180px" >
+
Another, later idea,  for their formation suggests that the crater was buried with mantle.  Since the center of the crater is deeper, the mantle will get compacted more.  The weight of the sediment would make it more resistant to later erosion. Later, will be greater along the edge; a plateau will be left in the middle, which is what we see with some right mold craters.  It was thought that ring-mold craters could only exist in areas with large amounts of ground ice.  However, with more extensive analysis of larger areas, it was found the ring mold craters are sometimes formed where there is not as much ice underground.<ref>https://www-sciencedirect-com.wikipedialibrary.idm.oclc.org/science/article/pii/S0019103518301532</ref>  <ref>Baker, D. and L. Carter.  2019.  Probing supraglacial debris on Mars 2: Crater morphology.  Icarus.  Volume 319.  Pages 264-280</ref>
File:52260 2165ringmoldcraters2.jpg|Ring mold craters  They may contain ice.
+
 
 +
<gallery class="center" widths="380px" heights="360px">
 +
 
 
26055ringmoldcrater.jpg|Close view of ring mold crater.  
 
26055ringmoldcrater.jpg|Close view of ring mold crater.  
 
File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
 
File:60858 2160ring.jpg|Ring-mold crater from the Picture of the Day 11/18/19
Line 174: Line 300:
  
 
==Dark Slope Streaks==
 
==Dark Slope Streaks==
 +
 +
[[File:Dark slope streaks on Mars 24.jpg|600pxr|Dark slope streaks]]
 +
 +
                                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>
 
[[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>
 
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="190px" heights="180px" >
 
File:55480 2060streaks.jpg|Dark slope streaks on a mound
 
File:23677streakslabeled.jpg|Streaks often start at a small point and then expand down slope.
 
File:55107 1930streaksboulders2.jpg|Dark slope streaks  As these streaks moved down, boulders changed their appearance.
 
File:55480 2060streaksobstacles.jpg|Some of the streaks here were affected by boulders.
 
  
File:ESP 046188 1855streakslabeled2.jpg|Streaks along a mesa
+
[[File:ESP 046188 1855streakslabeled2.jpg|600 pxr|Streaks along a mesa]]
 +
 
 +
                            Streaks along a mesa
 +
 
 +
<gallery class="center"  widths="380px" heights="360px">
 
File:ESP 045435 2055troughlayers.jpg|Dark slope streaks in a trough
 
File:ESP 045435 2055troughlayers.jpg|Dark slope streaks in a trough
  
 
</gallery>
 
</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==
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. 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>
+
 
 +
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>  They have been seen from the surface by the Perseverance Rover.<ref>https://www.jpl.nasa.gov/images/pia26074-martian-whirlwind-takes-the-thorofare</ref>  Dust devils are common.<ref>https://www.uahirise.org/ESP_042201_1715</ref>  One team of researchers have calculated that on average 1 dust devil happens every sol (day on Mars) for each square kilometer.<ref> https://scholarworks.boisestate.edu/cgi/viewcontent.cgi?article=1207&context=physics_facpubs</ref> <ref>Jackson, Brian; Lorenz, Ralph; and Davis, Karan. (2018). "A Framework for Relating the Structures and Recovery Statistics in Pressure Time-Series Surveys for Dust Devils". Icarus, 299, 166-174. http://dx.doi.org/10.1016/j.icarus.2017.07.027</ref>
  
 
[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]
 
[[File:ESP 057581 1340devils.jpg |Dust devil tracks near crater|600pxr|Dust devil tracks near crater]]
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
  
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle  Dark material is visible in the troughs of polygons.
 
 
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
 
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
 
  
 
File:ESP 036631 2335devilsbottom.jpg|Dust devil tracks in Casius quadrangle
 
File:ESP 036631 2335devilsbottom.jpg|Dust devil tracks in Casius quadrangle
  
 
</gallery>
 
</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==
 
==Dunes==
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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.
 
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.
  
<gallery class="center" widths="190px" heights="180px" >
+
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>  Since we have imaged Mars for many years, we have been able to detect some movement in dunes.<ref>https://www.uahirise.org/hipod/ESP_043617_1885</ref>
 +
 
 +
[[File:ESP 046378 1415dunescolor.jpg|thumb|300px|right|Dunes]]
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 +
[[File:33272 1400dunes.jpg|thumb|300px|left|Dunes]]
  
File:33272 1400dunes.jpg|Dunes
+
<gallery class="center"  widths="380px" heights="360px">
  
 
File:59628 1275dunes.jpg|Dunes in Hellas quadrangle
 
File:59628 1275dunes.jpg|Dunes in Hellas quadrangle
  
File:59658 1415dunes.jpg|Dunes The location is the Noachis quadrangle
 
  
File:58089 2170duneswidemarsp.jpg|Dunes The location is the Ismenius Lacus 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
  
</gallery>
+
 
 +
[[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==
 
==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.
 
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="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
File:ESP 018857 2225alpineglacier.jpg|Glacier moving out of a valley  This is similar to glaciers on the Earth.
+
 
 
File:ESP 050176 2245glacier.jpg|Glacier moving out of a valley
 
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: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: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.
 
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
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Image:ESP_020319flowcontext.jpg|Context for the next image of the end of a glacier.
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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. 
 +
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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>
 
</gallery>
  
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[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]
 
[[File:ESP 057389 2195ldacropped.jpg|thumb|300px|right|Lobate Debris Aprons (LDA) around a mound]]
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:ESP 036580 2260ldacropped.jpg|Lobate debris apron
 
File:ESP 036580 2260ldacropped.jpg|Lobate debris apron
 
File:ESP 036619 2275ldacropped.jpg|Lobate debris apron
 
File:ESP 036619 2275ldacropped.jpg|Lobate debris apron
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==Lineated Valley Fill (LVF) ==
 
==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.
+
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 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.]]
  
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[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of  Lineated Valley Fill (LVF)]]
 
[[File:46061 2190closelvf..jpg|thumb|400px|center|Close view of  Lineated Valley Fill (LVF)]]
  
<gallery class="center" widths="190px" heights="180px" >
 
  
 +
<gallery class="center"  widths="380px" heights="360px">
 
File:ESP 055408 1375lvf2.jpg|Lineated Valley Fill
 
File:ESP 055408 1375lvf2.jpg|Lineated Valley Fill
 
File:ESP 046840 2130lvf.jpg|Lineated Valley Fill in valley
 
File:ESP 046840 2130lvf.jpg|Lineated Valley Fill in valley
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==Concentric Crater Fill (CCF) ==
 
==Concentric Crater Fill (CCF) ==
 +
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[[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.
 
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="190px" heights="180px" >
+
 
Image: ESP_046622_1365ccf.jpg|Concentric Crater Fill  Lat: 43.1° S Long: 219.8°E (140.2 W)
+
 
 +
<gallery class="center" widths="380px" heights="360px">
 
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill
 
Image: ESP_046622_1365ccfclosecolor.jpg|Close, color view of Concentric Crater Fill
  
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==Brain Terrain==
 
==Brain Terrain==
 +
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[[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>
 
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="190px" heights="180px" >
 
  
 +
<gallery class="center"  widths="380px" heights="360px">
 
File:25246brainseroding.jpg|Brain terrain
 
File:25246brainseroding.jpg|Brain terrain
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle
+
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:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
File:45917 2220brainsopenclosed.jpg|Open and closed brain terrain
+
 
 
File:53630 2195brainslvf.jpg|Brains on surface of leaneted valley fill
 
File:53630 2195brainslvf.jpg|Brains on surface of leaneted valley fill
 
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
 
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
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==Ice Cap Layers==
 
==Ice Cap Layers==
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[[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).
 
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="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
  
File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap  This photo was named picture of the day for January 21, 2019.
 
 
File:ESP 061636 2620nicecaplayerscroppedlabeled.jpg|Northern ice cap layers
 
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 044934 2670icecaplayers.jpg|Layers exposed in ice cap in Mare Boreum quadrangle
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==Spiders==
 
==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>    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>
 
  
<gallery class="center" widths="190px" heights="180px" >
+
[[File:Spiders on Mars 23.jpg|600pxr|Spiders and plumes]]
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 +
                            Spiders and plumes
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 +
 
 +
[[File:56839 1000spiderslabeled.jpg |Close view of spiders]]
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 +
 
 +
                          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>
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 +
<gallery class="center" widths="380px" heights="360px">
  
File:56839 1000spiderslabeled.jpg|Close view of spiders
 
  
 
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program  
 
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program  
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==Mantle==
 
==Mantle==
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[[File:37167 1445mantlelabeled.jpg|Mantle  Mantle covers the surface irregularities on Mars]]
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                            Mantle  Mantle covers the surface irregularities on Mars
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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.
 
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="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
File:37167 1445mantlelabeled.jpg|Mantle  Mantle covers the surface irregularities on Mars.
 
  
File:54742 1485mantle.jpg|Mantle in a crater  The mantle here has made everything look smooth on one side of the crater.
 
 
File:46294 1395mantle.jpg|Comparison of  terrain  with and without a covering of mantle
 
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
 
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
 
45917 2220gulliesmantle.jpg|Close view that displays the thickness of the mantle, as seen by HiRISE under HiWish program
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</gallery>
 
</gallery>
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[[File:54742 1485mantle.jpg|Mantle in a crater  The mantle here has made everything look smooth on one side of the crater.]]
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    Mantle in a crater  The mantle here has made everything look smooth on one side of the crater.
  
 
==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.  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="190px" heights="180px" >
+
[[File:56942 1075icepolygonslabeled2.jpg|Polygons]]
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 +
 
 +
                                  Polygons
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 +
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.
 +
 
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 +
<gallery class="center" widths="380px" heights="360px">
  
File:56942 1075icepolygonslabeled2.jpg|Polygons
 
 
File:56148 1145polygonsveryclose.jpg|Enlarged view of polygons that shows polygons of varying sizes.  Dark lines are defects in processing.
 
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:56148 1145polygons.jpg|Close view of polygons
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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.
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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.
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</gallery>
 
</gallery>
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[[File:43821 2555dunesdefrosting2.jpg|Defrosting dune--white areas still contain frost]]
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 +
      Defrosting dune--white areas still contain frost.  Frost is in low parts of polygons.
  
 
==Scalloped Terrain==
 
==Scalloped Terrain==
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>http://www.uahirise.org/ESP_038821_1235</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="190px" heights="180px" >
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[[File:37461 2255scallopslabeled2.jpg|Scalloped terrain  This feature is important it may point future colonists to water supplies.]]
File:37461 2255scallopslabeled2.jpg|Scalloped terrain  This feature is important it may point future colonists to water supplies.
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 +
      Scalloped terrain  This feature is important it may point future colonists to water supplies.
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 +
 
 +
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>
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 +
<gallery class="center"  widths="380px" heights="360px">
 +
 
 
File:46916 2270scallopsmerging.jpg|Scalloped terrain
 
File:46916 2270scallopsmerging.jpg|Scalloped terrain
 
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia  
 
File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia  
Line 346: Line 596:
  
 
==Pingos==
 
==Pingos==
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="190px" heights="180px" >
+
[[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)]]
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>
 
</gallery>
 +
 
==Gullies==
 
==Gullies==
[[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="190px" heights="180px" >
+
[[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.<ref>https://www.uahirise.org/hipod/ESP_014074_1445</ref>  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:ESP 046386 1420gullies.jpg|Gullies
File:50858 1435gullylabeled.jpg|Gullies with parts labeled--Alcove, Channel, Apron
 
  
 
File:47395 1415gullycurvedchannels.jpg|Gullies    Curved channels were thought to need running water to form.
 
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.
 
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.
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>
 
</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==
 
==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>
 
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="190px" heights="180px" >
+
<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:52030 1560crater.jpg|Average crater showing layers
  
 
File:54774 1700colorcraterejecta.jpg|Crater and part of its ejecta
 
File:54774 1700colorcraterejecta.jpg|Crater and part of its ejecta
File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.
 
 
File:ESP 055252 1385brainscolorclose.jpg|Edge of crater with brain terrain on its floor
 
  
 
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 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 048131 2055crater.jpg|Crater with pits and holes on floor  The shapes on the floor occurred when ice left the ground.
  
File:52260 2165ringmoldclose.jpg|Close view of three 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.
 
 
File:ESP 046548 2355pedestalbutterfly.jpg|Pedestal crater with a butterfly shape.  this may have formed from a low angle impact.
 
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: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.
Line 386: Line 660:
 
File:61167 1735crater.jpg|Crater with thin ejecta  The color strip for HiRISE images is only in the center of images.
 
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.]]
  
</gallery>
+
 
 +
  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==
 
==Hellas Floor Features==
 +
 +
[[File:Shapes on the floor of Hellas 17.jpg|600pxr|Hellas floor shapes]]
 +
 +
                              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 &#124; 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.
 
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 &#124; 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.
  
<gallery class="center" widths="190px" heights="180px" >
+
[[File:55146 1425hellisfloorcropped.jpg|thumb|400px|center|Features on floor of Hellas impact basin.]]
File:55146 1425hellisfloor.jpg|Wide view of features on floor of Hellas impact basin.  The exact origin of these shapes is unknown at present.
+
 
 +
 
 +
[[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==
  
File:55146 1425hellisfloorcropped.jpg|Features on floor of Hellas impact basin.
+
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>
 
</gallery>
 +
 +
[[File: ESP 045779 1730meander.jpg|600pxr|Channel showing an old oxbow and a cutoff, as seen by HiRISE under HiWish program]]
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 +
                              Channel showing an old oxbow and a cutoff
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[[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.
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[[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.
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[[File: ESP 052494 1395meanders.jpg|600pxr|Channel  Arrows indicate evidence of a meander.]]
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                Channel  Arrows indicate evidence of a meander.
  
 
==Channels==
 
==Channels==
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[[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.
 
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="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:41974 1740channellabeled.jpg|Old river valley in the Sinus Sabaeus quadrangle
 
File:41974 1740channellabeled.jpg|Old river valley in the Sinus Sabaeus quadrangle
File:ESP 056917 2170channels3.jpg|Old river channel with branches
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WikiESP 033729 1410stream.jpg|Small branched channel
 
WikiESP 033729 1410stream.jpg|Small branched channel
Line 410: Line 742:
 
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.
 
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.
  
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>
  
 
==Streamlined Shapes==
 
==Streamlined Shapes==
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.  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="190px" heights="180px" >
+
[[File:ESP 045860 2085streamlinedcroppedlabeled.jpg|Streamlined shapes made by running water]]
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel  These forms were shaped by running water.
+
 
 +
 
 +
                          Streamlined shapes made by running water
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 +
 
 +
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: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
 
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>
 
</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==
 
==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.”
 
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="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
  
File:ESP 055431 1430invertedstream.jpg|Inverted Stream channel  it was once a stream, now it is a curved ridge.
+
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>
 
</gallery>
  
 
==Exhumed Craters==
 
==Exhumed Craters==
Exhumed terrain appears to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</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.
 
  
<gallery class="center" widths="190px" heights="180px" >
+
[[File:ESP 055550 1660exhumed.jpg|Exhumed crater  This crater was covered over and now it is being uncovered or "exhumed."]]
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|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).
 
  
</gallery>
+
[[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==
 
==Pedestal Craters==
A Pedestal crater is a crater with its ejecta sitting above the surrounding terrain.  Its ejecta form a raised platform (like a pedestal). 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="190px" heights="180px" >
+
[[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 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).
 
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).
  
Line 456: Line 817:
  
 
==Ridges==
 
==Ridges==
Ridge fields are another feature that we do not yet fully understand.  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="190px" heights="180px" >
+
[[File:36745 1905ridgesv2.jpg |Close view of ridges  We are sure how these were formed, but we have come up with a few possibilities.]]
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>Kerber, L., et al.
 +
2017.  Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation.  Icarus.  Volume 281.  Pages 200-219</ref> <ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref> <ref>Pascuzzo, A., et al2019.  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.<ref> https://www.uahirise.org/hipod/ESP_077982_1920</ref>  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: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: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:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle
 +
 
</gallery>
 
</gallery>
 +
 +
 +
[[File:ESP 036745 1905top.jpg|Ridge network in Amazonis quadrangle ]]
 +
 +
                              Ridge network in Amazonis quadrangle
  
 
==Layers==
 
==Layers==
Line 469: Line 846:
 
[[File:44507 1880longlayersdanielson.jpg|600pxr|Layers in Dannielson Crater, as seen by HiRISE under HiWish program]]
 
[[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.  They are found in many low places like craters.  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.
+
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>
 
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">
  
<gallery class="center" widths="190px" heights="180px" >
 
 
File: 54763_1500layers2.jpg
 
File: 54763_1500layers2.jpg
 
File: 54763_1500layerscolor.jpg
 
File: 54763_1500layerscolor.jpg
Line 480: Line 857:
  
 
File:59619 1845layers2labeled.jpg|Layers  Different colors of the rocks means they contain different minerals.
 
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.
 +
 +
File:Layers some with overhang ESP 26270 1820.jpg|Layers some with overhang.  This image was named HiRISE picture of the day.
 +
File:Layers and layered mounds ESP 26270 1820.jpg|Layers and layered mounds.  Each layer records some sort of change and water may have been involved.  This image was named HiRISE picture of the day.
 +
File:Layered area with faults ESP 26270 1820.jpg|Layers  Dark parts are basalt sand that has settled on horizonal surfaces.  This image was named HiRISE picture of the day.
 +
 +
File:Color view of layers 26270 1820.jpg|Close, color view of layers.  Light brown is from dust falling from sky.  Dark parts are basalt sand that has settled on horizonal surfaces.  This image was named HiRISE picture of the day.
  
 
</gallery>
 
</gallery>
 +
 +
[[File:Wide view of layers ESP 27747 1820.jpg|600pxr|Layers and faults in Arabia quadrangle]]
 +
 +
      Layers and faults in Arabia quadrangle--HiRISE Picture of the Day  (September 25, 2021)
 +
 +
  
 
[[File:544858 1885topcloselayers5.jpg|thumb|400px|center|Close view of layers, as seen by HiRISE under HiWish program  Location is  Danielson Crater.]]
 
[[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).
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[[File:ESP 047499 2245ribslabeled.jpg|500pxr|Ribbed terrain begins with cracks that eventually widen to produce hollows]]
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                Ribbed terrain begins with cracks that eventually widen to produce hollows
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[[File:28339 2245ribbbed.jpg|thumb|400px|center|Wide view of ribbed terrain.]]
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 +
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 +
[[File:ESP 025174 2245ribs.jpg|500pxr|Wide view of ribbed terrain.]]
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                              Wide view of ribbed terrain.
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[[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.
 +
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[[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]]
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[[File:44757 2185fracturesblocks.jpg|thumb|300px|center|Blocks forming]]
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[[File: 47577 1515blocks.jpg|thumb|400px|right|Surface breaking up into cube-shaped blocks]]
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[[File: 46684 1280breaking.jpg|thumb|500px|center|Layers breaking up into boulders in Galle Crater, as seen by HiRISE under HiWish program]]
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[[File:45377 2170blocks2.jpg|500pxr|Fractures forming large blocks  Box shows size of a football field]]
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 +
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                Fractures forming large blocks  Box shows size of a football field
 +
 +
==Volcanoes under ice==
 +
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[[Image:25755concentriccracks.jpg|500pxr|Large group of concentric cracks  Location is [[Ismenius Lacus quadrangle]].  Cracks were formed by a volcano under ice.]]
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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> <ref>Levy, J. et al.  2017. Candidate volcanic and impact-induced ice depressions on Mars.  Icarus. Volume 285.  Pages 185-194</ref>  Candidate volcanic and impact-induced ice depressions on Mars    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>
 +
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[[File:25755 2200collapse.jpg|thumb|400px|left|Close view of fractures from volcano under ice.]]
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[[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. 
 +
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[[File:49955 1665rslcolorarrows (1).jpg|500pxr|Recurrent slope lineae (RSL)  They form in warm seasons.]]
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 +
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                  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==
 
==How to suggest image==
Line 490: Line 959:
  
 
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.
 
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==
 
==References==
 
{{reflist|colwidth=30em}}
 
{{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]
 +
 +
* McEwen, A., et al.  2024.  The high-resolution imaging science experiment (HiRISE) in the MRO extended science phases (2009–2023).  Icarus.  Available online 16 September 2023, 115795.  In Press.
 +
 
==See Also==
 
==See Also==
 +
 
*[[Geography of Mars]]
 
*[[Geography of Mars]]
 
*[[Glaciers on Mars]]
 
*[[Glaciers on Mars]]
Line 504: Line 1,006:
 
*[[Sublimation landscapes on Mars]]
 
*[[Sublimation landscapes on Mars]]
 
*[[Viking 2]]
 
*[[Viking 2]]
 +
 
==Recommended reading==
 
==Recommended reading==
 +
 
*Grotzinger, J., R. Milliken (eds.).  2012.  Sedimentary Geology of Mars.  Tulsa:  Society for Sedimentary Geology.
 
*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
 
*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]
 
*[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
== External links ==
+
* Lorenz, R., J. Zimbelman.  2014.  Dune Worlds:  How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.

Latest revision as of 10:20, 27 March 2024

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.[1] [2] [3] It started in January 2010. Three thousand people signed up in the first few months of the program.[4] [5] 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.[6] [7] The first images were released in April 2010.[8] 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.[9]

Landslides

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.

Hollows

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.

Mud Volcanoes

Mud volcanoes from around Mars

                                 Mud volcanoes from around Mars

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.[10] 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.[11]

Volcanic vents

Volcanic vent with lava channel

                      Volcanic vent with lava channel


Volcanic vent

                        Volcanic vent

Lava Flows

Lava flow on Olympus Mons


                               Lava flow on Olympus Mons


Large areas of Mars are covered with lava flows.[12] [13] [14] [15] 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.[16]

Rootless Cones

Rootless cones

                                               Rootless cones

Rootless Cones are thought to be caused by lava flowing over ice or ground containing ice.[17] [18] 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.

Dikes

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.[19] On Mars many faults are due to stretching of the crust. The mass of huge volcanoes pull at the crust until it cracks.

Troughs

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.[20] [21] [22]

Faults

Faults are visible in some parts of Mars.[23] They are most noticeable in places where many layers exist. Sometimes their presence is known because they can change the direction of stream channels.

Layers and fault in Firsoff Crater


Layers and fault in Firsoff Crater


Faults in layered terrain
Faults in layered terrain
Faults in layers in Danielson Crater

Mesas and layers

File:Layered hills around Mars

                      Layered hills around Mars

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.

Layers in Craters

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.

Dipping Layers

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. Another idea for their origin was presented at 55th LPSC (2024) by an international team of researchers. They suggest that the layers are from past ice sheets.[25]

Wide view of dipping layers against slopes
Dipping layers These may be the remains of past layers of mantle that covered the whole area.

Set of dipping layers in crater


                                 Set of dipping layers in crater

Boulders

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.

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.

Color view of boulders

                                  Boulders formed from break up of a mesa

Yardangs

Yardangs


                                               Yardangs


Yardangs develop from fine-grained material. They are shaped by the wind and show the direction of the dominant winds.[26] [27] 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.[28] Because yardangs exhibit very few impact craters they are believed to be relatively young.[29] The largest single source of dust in the air on Mars comes from the Medusae Fossae Formation.[30]

Ring-Mold Craters

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.[31] [32] One popular idea for their formation is an impact into ice--Ice that is covered by a layer of debris.[33] 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[34] [35] [36] 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.

Another, later idea, for their formation suggests that the crater was buried with mantle. Since the center of the crater is deeper, the mantle will get compacted more. The weight of the sediment would make it more resistant to later erosion. Later, will be greater along the edge; a plateau will be left in the middle, which is what we see with some right mold craters. It was thought that ring-mold craters could only exist in areas with large amounts of ground ice. However, with more extensive analysis of larger areas, it was found the ring mold craters are sometimes formed where there is not as much ice underground.[37] [38]

Dark Slope Streaks

Dark slope streaks

                                Dark slope streaks

Some of the streaks here were affected by boulders.


              Streaks around a mound.  Some of the streaks here were affected by boulders.
Dark slope streaks As these streaks moved down, boulders changed their appearance.


Dark slope streaks are avalanche-like features common on dust-covered slopes.[39] These streaks have never been observed on the Earth.[40] They form in relatively steep terrain, such as along cliffs and crater walls.[41] 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.[42]


Streaks along a mesa

                            Streaks along a mesa

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.[43] [44]

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.[45] Dust devils on Mars have been photographed both from the ground and from orbit.[46] They helped scientists by blowing dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.[47] Dust devils can be 650 meters high and 50 meters across.[48] The pattern of the tracks has been shown to change every few months.[49] They have been seen from the surface by the Perseverance Rover.[50] Dust devils are common.[51] One team of researchers have calculated that on average 1 dust devil happens every sol (day on Mars) for each square kilometer.[52] [53]

Dust devil tracks near crater

Dust devil tracks in Hellas quadrangle Dark material is visible in the troughs of polygons.

                            Dust devil tracks in Casius quadrangle

Dunes

Colorful dunes in the Mare Tyrrhenum quadrangle[55]

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..[56] 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).[57] Since we have imaged Mars for many years, we have been able to detect some movement in dunes.[58]

Dunes
Dunes

Dunes The location is the Ismenius Lacus quadrangle

Colorful dunes in the Mare Tyrrhenum quadrangle|Dunes The location is the Ismenius Lacus quadrangle


Dunes The location is the Noachis quadrangle

                       Dunes The location is the Noachis quadrangle

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

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.[59] 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.

Lobate Debris Aprons (LDA’s)

Lobate debris aprons (LDAs), first seen by the Viking Orbiters, look like piles of rock debris below cliffs.[60] [61] They slope away from mesas and buttes. The Mars Reconnaissance Orbiter's Shallow Radar found pure ice in LDA’s around many mesas.[62] Based on this data, LDA’s are considered to be glaciers covered with a thin layer of rocks.[63][64] [65] [66] [67] [68]

Lobate Debris Aprons (LDA) around a mound

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.[69] 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.

Wide view of Lineated Valley Fill (LVF) Lat: 38.7° N Long: 45.7°E (314.3 W)
Close view of Lineated Valley Fill (LVF)


Concentric Crater Fill (CCF)

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.[70] It is common in the mid-latitudes of Mars,[71] [72] and is widely accepted as caused by glacial movement.[73] [74] The Ismenius Lacus quadrangle contains examples of concentric crater fill.


Brain Terrain

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.[75] 

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. [76]


Ice Cap Layers

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).


Spiders

Spiders and plumes

                            Spiders and plumes


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.[78] [79] 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.[80] [81] [82] [83] The process of making spiders was demonstrated in laboratory simulations involving slabs of dry ice and glass spheres of different sizes.[84] [85] [86]

Mantle

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).[87] 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.

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

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.[88] [89]

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.


Defrosting dune--white areas still contain frost


      Defrosting dune--white areas still contain frost.  Frost is in low parts of polygons.

Scalloped Terrain

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.”[90] [91] 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.[92] [93] [94] Scalloped topography may be of great importance for future colonization of Mars because radar studies reveal it is ice-rich.[95] [96] [97]

Pingos

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.

Gullies

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.[98] 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.[99] 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.

Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.[100]


Gullies in Phaethontis quadrangle Ridges at the end of the gullies may be the remains of old glaciers.[101]

Craters

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.[102] [103]

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.[104] [105] [106]

Hellas Floor Features

Hellas floor shapes

                             Hellas floor features

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." [107] [108] [109] This terrain has also been called "taffy pull" terrain, and it lies near honeycomb terrain, another strange surface.[110] 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.[111] How these shapes were made is still a mystery, although some explanations have been advanced.

Features on floor of Hellas impact basin.


Close view of center of a Hellas floor feature

                            Close view of center of a Hellas floor feature

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.[112] Finding them on Mars means that water probably flowed for a long time.

Channel showing an old oxbow and a cutoff, as seen by HiRISE under HiWish program

                              Channel showing an old oxbow and a cutoff

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.


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.


Channel Arrows indicate evidence of a meander.


               Channel   Arrows indicate evidence of a meander.

Channels

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.[113] [114] [115] [116] [117] 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.

Streamlined Shapes

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.[118] 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.


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

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.”


Exhumed Craters

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.[119] [120] 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.


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).
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

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).[121] 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. [122] [123] [124]

Ridges

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.[125] [126] [127] 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.[128] These fields can be quite complex and beautiful.


Ridge network in Amazonis quadrangle

                              Ridge network in Amazonis quadrangle

Layers

Layers in Dannielson Crater, as seen by HiRISE under HiWish program

Layers of rocks and other materials are very common on Mars.[129] They are found in many low places like craters.[130] The widespread occurrence of layering on the Red Planet has great significance. On Earth, much layering originates in bodies of water.[131] 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. [132] [133] Many microbes live deep underground.[134] [135] [136] Life under the Martian surface might find it easier since it would be protected from high levels of radiation.[137] 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.[138] [139]

Layers and faults in Arabia quadrangle

      Layers and faults in Arabia quadrangle--HiRISE Picture of the Day  (September 25, 2021)


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).

Ribbed terrain begins with cracks that eventually widen to produce hollows

                Ribbed terrain begins with cracks that eventually widen to produce hollows
Wide view of ribbed terrain.


Wide view of ribbed terrain.

                             Wide view of ribbed terrain.
Close, color view of ribbed terrain.

Blocks and boulders forming

Some places on Mars show rocks breaking into boulders or cube-shaped blocks.

Crossing joints, as seen by HiRISE under HiWish program


                             Crossing joints, as seen by HiRISE under HiWish program
Rocks forming


Blocks forming
Surface breaking up into cube-shaped blocks
Layers breaking up into boulders in Galle Crater, as seen by HiRISE under HiWish program

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

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.[140] [141] Candidate volcanic and impact-induced ice depressions on Mars 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.[142] Sites like this may have recently had held liquid water; therefore, they may be good places to search for evidence of life.[143][144]

Close view of fractures from volcano under ice.
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.[145] [146] [147] Evidence is still being gathered on this feature.

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.[148]

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

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  147. http://redplanet.asu.edu/?tag=recurring-slope-lineae%7Ctitle=recurring slope lineae - Red Planet Report|website=redplanet.asu.edu|
  148. McEwen, A., et al. 2017. Mars The Prestine Beauty of the Red Planet. University of Arizona Press. Tucson

External links

  • McEwen, A., et al. 2024. The high-resolution imaging science experiment (HiRISE) in the MRO extended science phases (2009–2023). Icarus. Available online 16 September 2023, 115795. In Press.

See Also

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
  • 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.