Difference between revisions of "What Mars Actually Looks Like!"

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Almost all of the sites that we have landed on Mars with spacecraft have been to the most drab and boring places on the planet.  This was done to ensure a safe landing.  This article will display many of the more exciting landscapes using HiRISE images.  HiRISE images can show detail down to the size of a small kitchen table.  With HiRISE we frequently even see spacecraft that have landed on the surface.  Many of the scenes shown here are about one would see at the height of a helicopter.   
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Almost all of the sites that we have landed on Mars with spacecraft have been to the most drab and boring places on the planet.  This was done to ensure a safe landing.  This article will display many of the more exciting landscapes using HiRISE images.  HiRISE images can show detail down to the size of a small kitchen table.  With HiRISE we frequently even see spacecraft that have landed on the surface.  Many of the scenes shown here are about one would see at the height of a helicopter.   
 
Most of the HiRISE images here were obtained through the HiWish program, a program where anyone could suggest places to be imaged with HiRISE.  To obtain the images, I studied wide angle CTX images to find sites that could contain interesting features.  I was lucky that many of my suggestions were photographed, and I was able to gather them together for this article.
 
Most of the HiRISE images here were obtained through the HiWish program, a program where anyone could suggest places to be imaged with HiRISE.  To obtain the images, I studied wide angle CTX images to find sites that could contain interesting features.  I was lucky that many of my suggestions were photographed, and I was able to gather them together for this article.
  
 
==Viking 1==
 
==Viking 1==
 
Viking 1 was the first successful spacecraft to land on Mars.  It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E).  July 20th was also the date when we first landed on the moon in 1969.
 
  
 
[[File:Mars Viking 11d128.png |thumb|300px|right|Rocks and dunes, as seen from Viking 1  Holes were dug by the digging tool.  Part of the meteorology boom is visible. ]]
 
[[File:Mars Viking 11d128.png |thumb|300px|right|Rocks and dunes, as seen from Viking 1  Holes were dug by the digging tool.  Part of the meteorology boom is visible. ]]
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Viking 1 was the first successful spacecraft to land on Mars.  It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E).  July 20th was also the date when we first landed on the moon in 1969.<br clear=all>
  
 
==Viking 2==
 
==Viking 2==
 
Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E).
 
  
 
[[File:Viking2lander1.jpg |thumb|300px|left| View from Viking 2 ]]
 
[[File:Viking2lander1.jpg |thumb|300px|left| View from Viking 2 ]]
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Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E).<br clear=all>
  
 
==Mars Pathfinder==
 
==Mars Pathfinder==
 
The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in [[Ares Vallis]].
 
  
 
[[File:Mars pathfinder panorama large.jpg |thumb|300px|right|Wide view from Mars pathfinder, showing Sojourner Rover ]]
 
[[File:Mars pathfinder panorama large.jpg |thumb|300px|right|Wide view from Mars pathfinder, showing Sojourner Rover ]]
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The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in [[Ares Vallis]].<br clear=all>
  
 
==Spirit Rover==
 
==Spirit Rover==
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The Spirit Rover landed on January 4, 2004 at 14.5684 S and 175.472636 E (184.527364 W).
 
The Spirit Rover landed on January 4, 2004 at 14.5684 S and 175.472636 E (184.527364 W).
  
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<gallery class="center" widths="380px" heights="360px">
 
File:Bonneville crater.jpg|Bonneville crater from Spirit Rover  Columbia Hills are in the right in the distance.  Spirit eventually drove to the Columbia Hills.
 
File:Bonneville crater.jpg|Bonneville crater from Spirit Rover  Columbia Hills are in the right in the distance.  Spirit eventually drove to the Columbia Hills.
 
File:Free Spirit.jpg|Wide view with Husband Hill in the distance to which Spirit eventually drove to.  Solar panels are visible.
 
File:Free Spirit.jpg|Wide view with Husband Hill in the distance to which Spirit eventually drove to.  Solar panels are visible.
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The Opportunity Rover landed on January 25, 2004 at 1.9462 S and 354.4734 E (5.5268 W).
 
The Opportunity Rover landed on January 25, 2004 at 1.9462 S and 354.4734 E (5.5268 W).
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
  
 
File:Opportunity Heat Shield.jpg|Wide view from Opportunity showing heat shield to the left and circular impact crater on the right
 
File:Opportunity Heat Shield.jpg|Wide view from Opportunity showing heat shield to the left and circular impact crater on the right
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==Phoenix==
 
==Phoenix==
 
Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis.
 
  
 
[[File:PIA13804-MarsPhoenixLander-Panorama-20080525b.jpg |thumb|300px|left|Wide view from Phoenix lander  Solar panels are visible.]]
 
[[File:PIA13804-MarsPhoenixLander-Panorama-20080525b.jpg |thumb|300px|left|Wide view from Phoenix lander  Solar panels are visible.]]
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Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis.<br clear=all>
  
 
==Curiosity Rover==
 
==Curiosity Rover==
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[[File:673885main PIA15986-full full.jpg |thumb|300px|right|Early view from Curiosity  Mount Sharp is in the distance.  The shadow of Rover is visible.  Mount Sharp at a height of about 3.4 miles is  taller than Mt. Whitney in California.]]
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The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W).  By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting.<br clear=all>
  
The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W).  By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting.
 
  
[[File:673885main PIA15986-full full.jpg |thumb|300px|center|Early view from Curiosity  Mount Sharp is in the distance.  The shadow of Rover is visible.  Mount Sharp at a height of about 3.4 miles is  taller than Mt. Whitney in California.]]
 
  
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<gallery class="center" widths="380px" heights="360px">
  
 
File:7623 mars-slip-face-downwind-sand-dune-namib-sol1196-pia20281-full2.jpg|Slip Face on Downwind Side of 'Namib' Sand Dune on Mars, as seen by Curiosity  Dune stands about 13 feet (4 meters) high.  Picture taken with Navcam.
 
File:7623 mars-slip-face-downwind-sand-dune-namib-sol1196-pia20281-full2.jpg|Slip Face on Downwind Side of 'Namib' Sand Dune on Mars, as seen by Curiosity  Dune stands about 13 feet (4 meters) high.  Picture taken with Navcam.
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The Martian surface displays many beautiful dark dunes.  For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.<ref>Lorenz, R. and  J. Zimbelman.  2014.  Dune Worlds
 
The Martian surface displays many beautiful dark dunes.  For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.<ref>Lorenz, R. and  J. Zimbelman.  2014.  Dune Worlds
 
How Windblown Sand Shapes Planetary Landscapes.  Springer.  NY.</ref>  The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.
 
How Windblown Sand Shapes Planetary Landscapes.  Springer.  NY.</ref>  The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.
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The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars.  However, we must remember that its atmosphere is only about 1 % as dense as the Earth's.  Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).<ref> https://www.space.com/30663-the-martian-dust-storms-a-breeze.html</ref>
  
 
[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]
 
[[File:ESP 034745 1665blue dunes.jpg|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>|600pxr|Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>]]
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                               Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>
 
                               Colorful dunes in the Mare Tyrrhenum quadrangle<ref>https://www.uahirise.org/ESP_057071_1890</ref>
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
  
 
File:61974 1710dunesrgb2.jpg|Dunes processed in the rgb color system
 
File:61974 1710dunesrgb2.jpg|Dunes processed in the rgb color system
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File:ESP 043821 2555dryice.jpg|Defrosting dunes in Mare Boreum quadrangle
 
File:ESP 043821 2555dryice.jpg|Defrosting dunes in Mare Boreum quadrangle
 
File:ESP 043821 2555dryicecolor.jpg|Color view of dunes defrosting  Ice is in the toughs of the polygons.
 
File:ESP 043821 2555dryicecolor.jpg|Color view of dunes defrosting  Ice is in the toughs of the polygons.
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File:ESP 046378 1415dunefield.jpg|Wide view of dune field
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File:46378 1415dunesirb.jpg|Close view of dunes
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File:46378 1415dunesirb2.jpg|Close view of dunes
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File:PSP 010277 1650fallingdunes.croppedjpg.jpg|Falling dunes  These “falling dunes” are a type of topographically-controlled sand dune that formed when down-slope winds were focused by local topography.  The dunes point to the lowest areas--in this photo that is toward the top.
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</gallery>
 
</gallery>
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[[File:ESP 031138 1380dunes.jpg|600pxr|Dunes  This image was named picture of the day for July 25, 2021]]
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                                  Dunes  This image was named picture of the day for July 25, 2021
  
 
==Layers==
 
==Layers==
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[[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]]
  
Layers and fault in Firsoff Crater in Oxia Palus quadrangle, as seen by HiRISE under HiWish program
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Layers and fault in Firsoff Crater in Oxia Palus quadrangle, as seen by HiRISE under [[HiWish program]]
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<gallery class="center"  widths="380px" heights="360px">
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File:Layers some with overhang ESP 26270 1820.jpg|Layers some with overhang.  This image was named HiRISE picture of the day
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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.
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File:Layered area with faults ESP 26270 1820.jpg|Layers  Dark parts are basalt sand that has settled on horizonal surfaces.
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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.
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File:Wikiesp 035896 1845crommelinbutte.jpg|thumb|300px|left|Layers in Crommelin Crater
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File:544858 1885topcloselayers5.jpg|thumb|300px|center|Layers in Danielson Crater in Oxia Palus quadrangle
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File:60331 1880layersclosecolor.jpg|thumb|right|300px|Color image of layers on the floor of Danielson Crater taken under the HiWish program
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</gallery>
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[[File:60331 1880widelayersdark.jpg|600pxr|Layers on the floor of Danielson Crater taken under the [[HiWish program]]  Box shows size of a football field.]]
  
[[File:Wikiesp 035896 1845crommelinbutte.jpg|thumb|300px|left|Layers in Crommelin Crater]]
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<gallery class="center" widths="190px" heights="180px" >
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File:Layers in Danielson Crater, as seen by HiRISE under HiWish program 01.jpg|Faults in Danielson Crater, as seen by HiRISE under HiWish program
  
[[File:544858 1885topcloselayers5.jpg|thumb|300px|center|Layers in Danielson Crater in Oxia Palus quadrangle]]
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File:Close view of layers in Danielson Crater, as seen by HiRISE under HiWish program 10.jpg|Faults and layers in Danielson Crater, as seen by HiRISE under HiWish program
  
[[File:60331 1880layersclosecolor.jpg|thumb|right|300px|Color image of layers on the floor of Danielson Crater taken under the HiWish program]]
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File:Layers in Danielson Crater, as seen by HiRISE under HiWish program 02.jpg|Wide view of layers in Danielson Crater, as seen by HiRISE under HiWish program.  Image was named HiRISE picture of the day.
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File:Layers in Danielson Crater, as seen by HiRISE under HiWish program 03.jpg|Close view of top of image of Danielson Crater, as seen by HiRISE (ESP_071634_1880).
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File:Layers in Danielson Crater, as seen by HiRISE under HiWish program 08.jpg|Close view of top of image of Danielson.  Arrows indicate parts that are enlarged.
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File:Layers in Danielson Crater, as seen by HiRISE under HiWish program 04.jpg|Layers in Danielson Crater with enlargements of some spots (indicated with arrows).
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File:Layers in Danielson Crater, as seen by HiRISE under HiWish program 06.jpg|Layers in Danielson Crater with enlargements of some spots (indicated with arrows).
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File:Close view of layers in Danielson Crater, as seen by HiRISE under HiWish program 07.jpg|Layers in Danielson Crater, as seen by HiRISE under HiWish program.
  
[[File:60331 1880widelayersdark.jpg|600pxr|Layers on the floor of Danielson Crater taken under the HiWish program  Box shows size of a football field.]]
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</gallery>
  
 
==Glaciers==
 
==Glaciers==
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There are large areas on Mars that contain what is thought to be ice moving under a cover of debris.  A few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>
 
There are large areas on Mars that contain what is thought to be ice moving under a cover of debris.  A few meters of debris can preserve ice for long periods of time.<ref>Head, J. W.; et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change". Earth and Planetary Science Letters. 241 (3): 663–671.</ref>
  
Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.<ref>Head, J. and D. Marchant.  2006.  Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars:  Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band.  Lunar. Planet. Sci. 37.  Abstract 1127</ref> <ref>Head, J. and D. Marchant.  2006.  Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars:  Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems.  Lunar. Planet. Sci. 37.  Abstract 1128</ref> <ref>Head, J., et al.  2006.  Extensive valley glacier deposits in the northern mid-latitudes of Mars:  Evidence for the late Amazonian obliquity-driven climate change.  Earth Planet. Sci. Lett. 241.  663-671</ref> <ref>Head, J., et al.  2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation.  Geophys. Res Lett.  33</ref> Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al.  2002.  Lunar Planet. Sci:  33.  Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> Lineated valley fill (LVF)are lines of ridges in valleys.<ref>Carr, M.  2006.  The Surface of Mars.  Cambridge University Press.  ISBN|978-0-521-87201-0</ref> <ref>Squyres, S.  1978.  Martian fretted terrain:  Flow of erosional debris.  Icarus: 34. 600-613.</ref> <ref>Levy, J. et al.  2007.  Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars:  Evidence for phases of glacial modification of the dichotomy boundary.  J. Geophys. Res.  112</ref>  These lines may have developed as other glaciers moved down valleys.  Some of these glaciers seem to come from material sitting around mesas and buttes.<ref>Baker, D., et al.  2009.  Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars:  Evidence for extensive mid-latitude glaciation in the Late Amazonian.  Icarus:  207. 186-209.</ref>  Lobate debris aprons  (LDA) is the name given to these glaciers.  All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.<ref>Marchant, D. and J. Head.  2007.  Antarctic dry valleys:  Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars.  Icarus:  192.187-222</ref> <ref>Dickson, J., et al.  2008.  Late Amazonian glaciation at the dichotomy boundary on Mars:  Evidence for glacial thickness maxima and multiple glacial phases.  Geology:  36 (5) 411-415</ref> <ref>Kress, A., et al.  2006.  The nature of the transition from lobate debris aprons to lineated valley fill:  Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars.  Lunar. Planet. Sci. 37.  Abstract 1323</ref>
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Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.<ref>Head, J. and D. Marchant.  2006.  Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars:  Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band.  Lunar. Planet. Sci. 37.  Abstract 1127</ref> <ref>Head, J. and D. Marchant.  2006.  Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars:  Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems.  Lunar. Planet. Sci. 37.  Abstract 1128</ref> <ref>Head, J., et al.  2006.  Extensive valley glacier deposits in the northern mid-latitudes of Mars:  Evidence for the late Amazonian obliquity-driven climate change.  Earth Planet. Sci. Lett. 241.  663-671</ref> <ref>Head, J., et al.  2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation.  Geophys. Res Lett.  33</ref> Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.<ref>Garvin, J. et al.  2002.  Lunar Planet. Sci:  33.  Abstract # 1255.</ref> <ref>http://photojournal.jpl.nasa.gov/catalog/PIA09662</ref> Lineated valley fill (LVF) are lines of ridges in valleys.<ref>Carr, M.  2006.  The Surface of Mars.  Cambridge University Press.  ISBN|978-0-521-87201-0</ref> <ref>Squyres, S.  1978.  Martian fretted terrain:  Flow of erosional debris.  Icarus: 34. 600-613.</ref> <ref>Levy, J. et al.  2007.  Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars:  Evidence for phases of glacial modification of the dichotomy boundary.  J. Geophys. Res.  112</ref>  These lines may have developed as other glaciers moved down valleys.  Some of these glaciers seem to come from material sitting around mesas and buttes.<ref>Baker, D., et al.  2009.  Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars:  Evidence for extensive mid-latitude glaciation in the Late Amazonian.  Icarus:  207. 186-209.</ref>  Lobate debris aprons  (LDA) is the name given to these glaciers.  All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.<ref>Marchant, D. and J. Head.  2007.  Antarctic dry valleys:  Microclimate zonation, variable geomorphic processes, and implications for assessing climatic change on Mars.  Icarus:  192.187-222</ref> <ref>Dickson, J., et al.  2008.  Late Amazonian glaciation at the dichotomy boundary on Mars:  Evidence for glacial thickness maxima and multiple glacial phases.  Geology:  36 (5) 411-415</ref> <ref>Kress, A., et al.  2006.  The nature of the transition from lobate debris aprons to lineated valley fill:  Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region on Mars.  Lunar. Planet. Sci. 37.  Abstract 1323</ref>
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:ESP 050176 2245glacier.jpg|Glacier leaving a valley in the Ismenius Lacus quadrangle
 
File:ESP 050176 2245glacier.jpg|Glacier leaving a valley in the Ismenius Lacus quadrangle
 
File:Hollows as seen by hirise under hiwish program.jpg|Concentric crater fill  The concentric lines are  formed from ice moving away from the crater walls.  This crater is mostly full of ice.
 
File:Hollows as seen by hirise under hiwish program.jpg|Concentric crater fill  The concentric lines are  formed from ice moving away from the crater walls.  This crater is mostly full of ice.
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<gallery class="center" widths="380px" heights="360px">
<gallery class="center" widths="190px" heights="180px" >
 
 
File:ESP 046840 2130lvf.jpg|Lineated Valley Flow in valley
 
File:ESP 046840 2130lvf.jpg|Lineated Valley Flow in valley
 
File:53630 2195lvf.jpg|Lineated Valley Flow, as seen by HiRISE under the HiWish program
 
File:53630 2195lvf.jpg|Lineated Valley Flow, as seen by HiRISE under the HiWish program
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==Gullies==
 
==Gullies==
  
[[Martian gullies]] are networks of narrow channels and their associated downslope  deposits, found on steep slopes.  A high concentration occurs near 40 degrees north and south of the equator.  Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref name="Malin, M. 2000">Malin, M., Edgett, K.  2000.  Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters.  They were believed to be caused by recent running water, but with more observations it was shown that pieces of dry ice moving down slopes could cause them.
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[[Martian gullies]] are networks of narrow channels and their associated downslope  deposits, found on steep slopes.  A high concentration occurs near 40 degrees north and south of the equator.  Usually, each gully has an ''alcove'' at its head, a fan-shaped ''apron'' at its base, and a ''channel'' linking the two.<ref name="Malin, M. 2000">Malin, M., Edgett, K.  2000.  Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.</ref> They are believed to be relatively young because they have few, if any craters.  They were believed to be caused by recent running water, but with more observations other ideas emerged.  In summary of our present understanding of gullies it can be said:  A number of studies have demonstrated that gullies are being modified on present day Mars. <ref>C.M. Dundas, A.S. McEwen, S. Diniega, C.J. Hansen, S. Byrne, J.N. McElwaine.  The formation of gullies on Mars today.  Geol. Soc. London Spec. Publ., 467 (2019), pp. 67-94, 10.1144/SP467.5</ref> <ref>C.M. Dundas, S. Diniega, C.J. Hansen, S. Byrne, A.S. McEwen.  Seasonal activity and morphological changes in Martian gullies.  Icarus, 220 (2012), pp. 124-143, 10.1016/j.icarus.2012.04.005 </ref> <ref>.M. Dundas, S. Diniega, A.S. McEwen.  Long-term monitoring of Martian gully formation and evolution with MRO/HiRISE.  Icarus, 251 (2015), pp. 244-263, 10.1016/j.icarus.2014.05.013</ref> <ref>J. Raack, S.J. Conway, T. Heyer, V.T. Bickel, M. Philippe, H. Hiesinger, A. Johnsson, M. Massé.  Present-day gully activity in Sisyphi Cavi, Mars - flow-like features and block movements.  Icarus, 350 (2020), 10.1016/j.icarus.2020.113899. article #113899</Ref>  Today, liquid water cannot exist on the Red planet because the both the pressure and the temperature are too low.  Researchers have proposed other mechanisms that could account for gully formation without liquid water.<ref>S.J. Conway, T. de Haas, T.N. Harrison.  Martian gullies: a comprehensive review of observations, mechanisms and insights from Earth analogues.  Geol. Soc. London Spec. Publ., 467 (2019), pp. 7-66, 10.1144/SP467.14</ref>  Most involve dry ice (solid carbon dioxide) accumulating during cold seasons and then changing to a gas in the spring.  The gas coming off could start material moving down slopes.  The gas mixed with sand and other debris could act like water to erode channels.  Also, pieces of dry ice could easily side down due to the lubricating effect of gas coming off the dry ice.
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<gallery class="center"  widths="380px" heights="360px">
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File:Channels on Southern Sand Dunes with ice blocks visible ESP 079809 1325.jpg|Channels on sand dunes, as seen by HiRISE.  Arrows show chunks of ice that moved down to enlarge gullies.
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</gallery>
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However, one wonders if these processes could account for the formation of all the gullies.  Maybe, liquid water was sometimes necessary, especially to move large boulders.  A study of over 700 sites, published in 2022 in Icarus, concluded that liquid water would not have been needed.  During the duration of the study many large boulders were moved—one being 5 meters across.  Many types of changes were seen in gullies.  Some channels were extended, new channels were formed, and other channels were filled with new debris.<ref> Dundas, C., et al.  2022.  Martian gully activity and the gully sediment transport system.  Icarus.  (in press) </ref>  <ref>https://www.sciencedirect.com/science/article/pii/S0019103522002408#bb0145</ref>  Perhaps, some water was involved in the past, but all the gullies seen today could have been made without water.  
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:ESP 039621 1315gullies.jpg|Gullies with alcove, channel, and apron labeled   
 
File:ESP 039621 1315gullies.jpg|Gullies with alcove, channel, and apron labeled   
 
File:47395 1415gullycurvedchannels.jpg|Gullies in Argyre quadrangle  Curved channels were thought to need running water to form.
 
File:47395 1415gullycurvedchannels.jpg|Gullies in Argyre quadrangle  Curved channels were thought to need running water to form.
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File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program
 
File:57707 1410gullycolorwide.jpg|Color view of Gullies, as seen by HiRISE under HiWish program
 
File:Gullies near Newton Crater2185.jpg|Gullies  in Phaethontis quadrangle  Ridges at the end of the gullies may be the remains of old glaciers.<ref>https://www.uahirise.org/ESP_057450_1410</ref>
 
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>
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File:Close view of gully.jpg|Close view of gully in crater, as seen by HiRISE
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</gallery>
 +
<gallery class="center"  widths="380px" heights="360px">
 +
File:Close view of gullies ESP 080430 2310 01.jpg|Gullies on crater wall  The bright apron is a bit unusual.
 +
File:Close view of gullies ESP 080430 2310 02.jpg|Gully on crater wall  The bright apron is a bit unusual.
 
</gallery>
 
</gallery>
  
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There are thousands of channels that were probably caused by running water in the past on Mars.  Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref>
 
There are thousands of channels that were probably caused by running water in the past on Mars.  Some are large; some are tiny.<ref>https://en.wikipedia.org/wiki/Outflow_channels</ref> <ref>Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> <ref>Baker, V.R.; Carr, M.H.; Gulick, V.C.; Williams, C.R. & Marley, M.S. "Channels and Valley Networks". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. & Matthews, M.S. Mars. Tucson, AZ: University of Arizona Press.</ref> <ref>Burr, D.M., McEwan, A.S., and Sakimoto, S.E. (2002). "Recent aqueous floods from the Cerberus Fossae, Mars". Geophys. Res. Lett., 29(1), 10.1029/2001G1013345.</ref> <ref>^ Baker, V.R. (1982). The Channels of Mars. Austin: Texas University Press.</ref>
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
WikiESP 033729 1410stream.jpg|Small branched channel
 
WikiESP 033729 1410stream.jpg|Small branched channel
 
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
 
File:ESP 041974 1740channel.jpg|Channel in the Sinus Sabaeus quadrangle
File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel  These were shaped by running water.
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File:ESP 052677 2075streamlined.jpg|Streamlined forms in wide channel  These were shaped by running water.<ref>https://www.uahirise.org/ESP_045833_1845</ref>
 
File:WikiESP 039594 1365oxbow.jpg|An oxbow means that water flowed long enough to make a meander before the stream made a shortcut across the meanders.
 
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>
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 +
== Inverted relief ==
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Some places on Mars show inverted relief. In these locations, a stream bed may be a raised feature, instead of a valley. Inverted former stream channels may be caused by the deposition of large rocks, cementation, or maybe by lava moving down the channel. In either case later erosion would erode the surrounding land and leave the old channel as a raised ridge because the ridge would be more resistant to erosion. The image below, taken with HiRISE show curved ridges that are old channels that have become inverted.  They have the shape of streams but are above ground.<ref>http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_002279_1735</ref>
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[[File:ESP 057453 2050ridges.jpg|thumb|500px|center|Possible inverted streams, as seen by HiRISE under HiWish program]]
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[[File:ESP 077583 2255inverted.jpg|thumb|500px|center|Inverted stream, a stream bed has been filled with hard materials that did not erode away like the surroundings]]
  
 
==Troughs==
 
==Troughs==
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The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.”  Some of them show evidence that lava and/or water have come out of them in the past.  They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>
 
The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.”  Some of them show evidence that lava and/or water have come out of them in the past.  They can be very long.<ref>https://en.wikipedia.org/wiki/Fossa_(geology)</ref> <ref>James W. Head; Lionel Wilson; Karl L. Mitchell (2003). "Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release". Geophysical Research Letters. 30 (11): 2265. Bibcode:2003GeoRL..30k..31H. doi:10.1029/2003GL017135</ref> <ref>Burr, D. et al. 2002. Repeated aqueous flooding from the Cerberus Fossae: evidence for very recently extant deep groundwater on Mars. Icarus. 159: 53-73.</ref>
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:Troughs in Elysium Planitia.jpg|Troughs in the Elysium Planitia
 
File:Troughs in Elysium Planitia.jpg|Troughs in the Elysium Planitia
 
File:ESP 051781 2035troughs.jpg|Troughs in Amenthes quadrangle
 
File:ESP 051781 2035troughs.jpg|Troughs in Amenthes quadrangle
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==Craters==
 
==Craters==
  
Most of the surface of Mars is over a billion years old.  Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time.  So, impact craters are a major surface feature.  There is a rich variety of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>
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Most of the surface of Mars is over a billion years old.  Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time.  So, impact craters are a major surface feature.  There is a rich variety of craters on the planet.<ref>https://en.wikipedia.org/wiki/List_of_craters_on_Mars</ref> <ref>Carr, M.H. (2006) The surface of Mars; Cambridge University Press: Cambridge, UK</ref>   We have found that Mars is hit by 200 impacts/year.<ref>https://www.space.com/21198-mars-asteroid-strikes-common.html</ref> <ref>https://www.sciencedirect.com/science/article/abs/pii/S0019103513001693?via%3Dihub</ref> <ref>Daubar, I., et al.  2013.  The current martian cratering rate.  Icarus.  Volume 225. 506-516. </ref>
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[[File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program  The impact reached down to a layer that is light-toned.  That light-toned material was then deposited on a dark surface.
 
[[File:ESP 059649 1695craterpretty.jpg |Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program  The impact reached down to a layer that is light-toned.  That light-toned material was then deposited on a dark surface.
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<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
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File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.
 
File:ESP 046046 2095craterandejecta.jpg|This is a fairly young crater as it still shows ejecta, layers, and a rim.
File:26079secondaries.jpg|Group of secondary craters  These are formed from material that is blasted way up in the air from the impact.
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 +
File:26079secondaries.jpg|Group of secondary craters  These are formed from material that is blasted way up in the air from the impact.<ref>https://www.uahirise.org/hipod/ESP_046876_1465</ref>
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 +
File:Secondary craters ESP 081458 1425.jpg|Secondry craters, as seen by HiRISE under HiWish program  These were made from material thrown in the air by primary impact of large body nearby.
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File:ESP 046876 1465secondarycraters.jpg|Group of secondary craters  They are small and the same age.  They formed from material that was blasted way up in the air from an impact.
 +
 
 
File:ESP 048062 1425gulliesridges.jpg|Crater containing gullies and depressions  The curved depressions are formed when the ground loses ice.  Gullies may be due to water or dry ice moving down the walls.
 
File:ESP 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:48131 2055pitsforming.jpg|Close view of pits on floor of crater  A box shows the size of a football field. Note: This is an enlargement of the previous image of a crater.
 
File:48131 2055pitsforming.jpg|Close view of pits on floor of crater  A box shows the size of a football field. Note: This is an enlargement of the previous image of a crater.
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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>
 
File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle  These layered features are quite common in some regions of Mars.
 
File:ESP 049884 2125pyramid.jpg|Layered feature in crater in Casius quadrangle  These layered features are quite common in some regions of Mars.
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File:ESP 052260 2165ringmold.jpg|Wide view of ring-mold crater on the floor of a larger crater
 
File:ESP 052260 2165ringmold.jpg|Wide view of ring-mold crater on the floor of a larger crater
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File:52260 2165ringmoldclose.jpg|Close view of ring-mold craters (indicated with arrows)  Surface between the ring-mold craters is covered with brain terrain.
 
File:52260 2165ringmoldclose.jpg|Close view of ring-mold craters (indicated with arrows)  Surface between the ring-mold craters is covered with brain terrain.
File:29565 2075newcratercomposite.jpg|New, small crater  We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet.
+
 
 +
File:29565 2075newcratercomposite.jpg|New, small crater  We have detected many new craters on Mars that have impacted the planet since good cameras have orbited the planet. To see before and after photos of a new impact go to https://static.uahirise.org/images/2020/details/cut/ESP_062948_2175.gif
 +
 
 
File:Iceincraterscomparison.jpg|Exposed ice in small craters  The fresh ice had almost disappeared when the second picture was taken.  This set of images is good evidence that ice lies under a thin layer of debris.
 
File:Iceincraterscomparison.jpg|Exposed ice in small craters  The fresh ice had almost disappeared when the second picture was taken.  This set of images is good evidence that ice lies under a thin layer of debris.
File:ESP 037528 2350pedestal.jpg|Pedestal crater  The surface was protected from erosion by the ejecta.  In the past all the surrounding ground was at the level of the pedestal.  Most of the loss is thought to be from the loss of ice.
+
 
 +
File:ESP 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.<ref>S.J. Kadish, J.W. Head.  2011.  Impacts into non-polar ice-rich paleodeposits on Mars: excess ejecta craters, perched craters and pedestal craters as clues to Amazonian climate history.  Icarus, 215, pp. 34-46</ref> <ref>S.J. Kadish, J.W. Head.  2014. The ages of pedestal craters on Mars: evidence for a late Amazonian extended periodic emplacement of decameters-thick mid-latitude ice deposits.  Planet. Space Sci., 91, pp. 91-100</ref>
 +
 
 +
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.
  
File:ESP 059649 1695craterpretty.jpg|Young crater with bright ejecta in the Phoenicis Lacus quadrangle as seen by HiRISE under HiWish program  The impact reached down to a layer that is light-toned.  That light-toned material was then deposited on a dark surface.
 
 
</gallery>
 
</gallery>
 +
Scientists love to study central peaks of craters because they contain samples of material from deep under a surface.  Durning an impact, the ground is pushed down.  It then rebounds and brings up rocks from deep underground.<ref> https://www.uahirise.org/ESP_013514_1630</ref>
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<gallery class="center"  widths="380px" heights="360px">
  
==Scalloped Terrain==
+
File:ESP 013514 1630centralcolors.jpg|Central peak of an impact crater, as seen by HiRISE  Colors show different minerals--some used to be deep underground.
  
Scalloped topography  is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially  prominent in the region of Utopia Planitia.<ref name=ref1>{{cite journal | 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 | bibcode=2009JGRE..114.4005L}}</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref>  Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>http://www.uahirise.org/ESP_038821_1235</ref>  Scalloped  topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.<ref name="Dundas, C. 2015">{{cite journal | last1 = Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>
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</gallery>
  
[[File:46916 2270scallopsmerging.jpg| |thumb|300px|left|Scalloped terrain in Casius quadrangle ]]
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==Scalloped Terrain==
  
[[File:37461 2255scallopedscale.jpg| thumb|300px|center|Scalloped terrain in Utopia Planitia in the Casius quadrangle]]
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Scalloped topography  is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially  prominent in the region of Utopia Planitia.<ref> Lefort | first1 = A. | last2 = Russell | first2 = P. | last3 = Thomas | first3 = N. | last4 = McEwen | first4 = A.S. | last5 = Dundas | first5 = C.M. | last6 = Kirk | first6 = R.L. | year = 2009 | title = HiRISE observations of periglacial landforms in Utopia Planitia | url = http://www.agu.org/pubs/crossref/2009/2008JE003264.shtml | journal = Journal of Geophysical Research | volume = 114 | issue = | page = E04005 | doi = 10.1029/2008JE003264 |</ref> <ref>Morgenstern A, Hauber E, Reiss D, van Gasselt S, Grosse G, Schirrmeister L (2007): Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars. Journal of Geophysical Research: Planets 112, E06010.</ref>  Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.<ref>http://www.uahirise.org/ESP_038821_1235</ref> <ref>https://www.uahirise.org/hipod/PSP_001938_2265</ref> <ref>Dundas, C., et al.  2015.  Modeling the development of martian sublimation thermokarst landforms.  Icarus: 262, 154-169.</ref>  Scalloped  topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.<ref name="Dundas, C. 2015">Dundas | first1 = C. | last2 = Bryrne | first2 = S. | last3 = McEwen | first3 = A. | year = 2015 | title = Modeling the development of martian sublimation thermokarst landforms | url = | journal = Icarus | volume = 262 | issue = | pages = 154–169 | doi=10.1016/j.icarus.2015.07.033 </ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.</ref>
  
[[File:37461 2255scallopedclose.jpg| thumb|300px|right|Scalloped terrain in Utopia Planitia]]
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<gallery class="center"  widths="380px" heights="360px">
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File:46916 2270scallopsmerging.jpg|Scalloped terrain in Casius quadrangle
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File:37461 2255scallopedscale.jpg|Scalloped terrain in Utopia Planitia in the Casius quadrangle
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File:37461 2255scallopedclose.jpg|Scalloped terrain in Utopia Planitia
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</gallery>
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<br clear=all>
  
 
==Brain Terrain==
 
==Brain Terrain==
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Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze.  Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>
 
Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze.  Some ridges may consist of an ice core, so they may be sources of water for future colonists.<ref> Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.</ref>
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle
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File:45917 2220openclosedbrains.jpg|Labeled picture of open and closed brain terrain in the Ismenius Lacus quadrangle Closed-cell brain terrain may still contain an ice core.<ref>Levy, J., et al.  2009.  Concentric crater fill in Utopia Planitia:  History and interaction between glacial "brain terrain" and periglacial mantle processes. Icarus: 202, 462-476.</ref>
 
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
 
File:ESP 035208 2215brainslabeledmarspedia.jpg|Wide view of brain terrain in the Ismenius Lacus quadrangle
 
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
 
File:45917 2220brainsforming.jpg|Brain terrain forming in Ismenius Lacus quadrangle
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==Linear Ridge Networks==
 
==Linear Ridge Networks==
  
This terrain appears over much of the planet.  It consists of groups of narrow ridges that often meet at close to right angles.  We are not sure of how it originated. It may have been caused by fluids moving into cracks that were created by impacts.  The fluids then became hard and erosion resistant.<ref>Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref> <ref>Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276.</ref> <ref>Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.</ref> <ref>Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus: 281, 200-219.</ref> <ref>E. K. Ebinger E., J. Mustard. 2015. LINEAR RIDGES IN THE NILOSYRTIS REGION OF MARS: IMPLICATIONS FOR SUBSURFACE FLUID FLOW. 46th Lunar and Planetary Science Conference (2015) 2034.pdf</ref> <ref>Saper, L., J. Mustard. 2013. Extensive linear ridge networks in Nili Fossae and Nilosyrtis, Mars: implications for fluid flow in the ancient crust. Geophysical Research letters: 40, 245-249.</ref> <ref>Kerber L.,  Schwamb M., Portyankina G.  Hansen C. J.  Aye K.-M. Global Polygonal Ridge Networks:  Evidence for Pervasive Noachian Crustal Groundwater Circulation [#2972]. pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2972.pdf49th</ref>
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[[File:46269 1770ridgesmesa.jpg|Close view of ridge network, as seen by HiRISE under HiWish program
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|600pxr|Close view of ridge network, as seen by HiRISE under HiWish program]]
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Close view of ridge network, as seen by HiRISE under HiWish program
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This terrain appears over much of the planet.  However, there is a heavy concentration of these features, also called irregular polygonal ridge networks, in the Nili Fossae region.<ref>Pascuzzo, A., et al.  2019.  The formation of irregular polygonal ridge networks, Nili Fossae, Mars:
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Implications for extensive subsurface channelized fluid flow in the Noachian.  Icarus: 319, 852-868.</ref>  These networks consist of groups of narrow ridges that often meet at close to right angles.  We are not sure of how it originated.<ref>https://www.uahirise.org/hipod/PSP_008189_2080</ref>
 +
They may have been caused by fluids moving into cracks that were created by impacts.  The fluids then became hard and erosion resistant.<ref>Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref> <ref>Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276.</ref> <ref>Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.</ref> <ref>Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus: 281, 200-219.</ref> <ref>E. K. Ebinger E., J. Mustard. 2015. LINEAR RIDGES IN THE NILOSYRTIS REGION OF MARS: IMPLICATIONS FOR SUBSURFACE FLUID FLOW. 46th Lunar and Planetary Science Conference (2015) 2034.pdf</ref> <ref>Saper, L., J. Mustard. 2013. Extensive linear ridge networks in Nili Fossae and Nilosyrtis, Mars: implications for fluid flow in the ancient crust. Geophysical Research letters: 40, 245-249.</ref> <ref>Kerber L.,  Schwamb M., Portyankina G.  Hansen C. J.  Aye K.-M. Global Polygonal Ridge Networks:  Evidence for Pervasive Noachian Crustal Groundwater Circulation [#2972]. pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 2972.pdf49th</ref>  We are not totally sure of the exact ways these ridges were created.  Over 14,000 people from around the world helped map them, so that scientists could better understand them.  Some ridges contain clays, so water may have been involved in their formation because clays need water to form.<ref>https://news.asu.edu/20220405-citizen-scientists-help-map-ridge-networks-may-hold-records-ancient-groundwater-mars</ref> <ref>Khuller, A., et al.  2022.  Irregular polygonal ridge networks in ancient Noachian terrain on Mars.  Icarus. 374.  114833</ref>
 
    
 
    
<gallery class="center" widths="190px" heights="180px" >
+
<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 036745 1905top.jpg|Ridge network in Amazonis quadrangle  
 +
File:ESP 046269 1770ridegenetworkmiddle.jpg|Ridge network in Mare Tyrrhenum quadrangle
 +
 +
File:46269 1770ridges2.jpg|Close view of ridge network
 
</gallery>
 
</gallery>
  
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Yardangs form from fine-grained material.  They are shaped by the wind and show the direction of the prevailing winds.  Much of this fine-grained material probably has its origin in the many large volcanoes on the planet.  Yardangs are especially common  in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref>  Because they exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>
 
Yardangs form from fine-grained material.  They are shaped by the wind and show the direction of the prevailing winds.  Much of this fine-grained material probably has its origin in the many large volcanoes on the planet.  Yardangs are especially common  in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.<ref>http://adsabs.harvard.edu/abs/1979JGR....84.8147W SAO/NASA ADS Astronomy Abstract Service: Yardangs on Mars</ref>  Because they exhibit very few impact craters they are believed to be relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:61167 1735yardangs3.jpg|Yardangs
 
File:61167 1735yardangs3.jpg|Yardangs
 
File:35558 1830yardangs.jpg|Yardangs in Amazonis quadrangle
 
File:35558 1830yardangs.jpg|Yardangs in Amazonis quadrangle
 
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 045831 1750yardangscolor.jpg|Close, color view of yardangs in Amazonis quadrangle  
 
File:ESP 045831 1750yardangscolor.jpg|Close, color view of yardangs in Amazonis quadrangle  
 
+
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>
  
 
==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; consequently exposing a dark layer.<ref>https://www.uahirise.org/ESP_058427_1080</ref>  Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> The 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; consequently exposing a dark layer.<ref>https://www.uahirise.org/ESP_058427_1080</ref>  Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov</ref> The dust devils can be 650 meters high and 50 meters across.<ref> https://www.uahirise.org/ESP_061787_2140</ref>  The pattern of the tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>
[[Image:dust_devils.gif|thumb|right|300px|Dust devils photographed by Mars Rover Spirit]]
 
  
<gallery class="center" widths="190px" heights="180px" >
+
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> In the first 216 Martian days (Sols), the Perseverance Rover in Jezero Crater found that at least four dust devils passed Perseverance on a typical Martian day and that more than one per hour passes by during a peak hourlong period just after noon.<ref>https://www.jpl.nasa.gov/news/nasas-perseverance-studies-the-wild-winds-of-jezero-crater?utm_source=iContact&utm_medium=email&utm_campaign=nasajpl&utm_content=Day%20in%20Review%20-%206-1-22</ref>
 +
<ref>https://www.science.org/doi/10.1126/sciadv.abn3783</ref> <ref> Newman, C., et al.  2022.  The dynamic atmospheric and aeolian environment of Jezero crater, Mars.  Science Advances.  Vol. 8.  Number 21</ref>  Perseverance Rover recorded a tall dust devil in the distance on Aug. 30, 2023.
 +
Scientists calculated that the dust devil was about 2.5 miles (4 kilometers) away and was moving east to west at  about 12 mph (19 kph). Its width was about 200 feet (60 meters). Even though only the bottom 387 feet (118 meters) of the devil was visible in the camera frame, scientists estimated its total  height at about 1.2 miles (2 kilometers)  using the dust devil's shadow.<ref>https://www.jpl.nasa.gov/images/pia26074-martian-whirlwind-takes-the-thorofare</ref>
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<gallery class="center" widths="380px" heights="360px">
 +
File:PIA26074-MarsPerseveranceRover-Whirlwind-20230830.gif|Dust devil as seen by Perseverance rover It is 5 times taller than the Empire State Building
 
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
 
File:ESP 036297 2370devils.jpg|Dust Devil Tracks
 
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle  Dark material is visible in the troughs of polygons.
 
File:ESP 048078 1160devils.jpg|Dust devil tracks in Hellas quadrangle  Dark material is visible in the troughs of polygons.
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 +
File:ESP 061787 2140devilcropped.jpg
 
</gallery>
 
</gallery>
  
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They form in relatively steep terrain, such as along cliffs and  crater  walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S.  2002.  Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref>  The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
 
They form in relatively steep terrain, such as along cliffs and  crater  walls.<ref name= Schorghofer02>Schorghofer, N.; Aharonson, O.; Khatiwala, S.  2002.  Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126.</ref>  The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.<ref>Sullivan, R. et al.  2001.  Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.</ref>
  
<gallery class="center" widths="190px" heights="180px" >
+
Dry ice accumulates just under the surface during cold Martian nights and then changes to a gas in the morning. That gas creates enough wind to disturb dust particles and send them down steep slopes. As the bright dust slides down it reveals the underlying dark volcanic rocks. This process was discovered by measuring temperatures in the area. At the recorded temperatures, carbon dioxide from the air should have frozen on the surface, but it was not visible. It was concluded that the dry ice was forming just under the surface rather than on top..<ref>https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JE006988</ref> <ref>Lange, S., et al.  2022.  Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks.  JGR Planets.  Volume127, Issue4.  e2021JE006988</ref>
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<gallery class="center" widths="380px" heights="360px">
 
File: ESP 045435 2055troughlayers.jpg | Dark slope streaks in trough  Layers are also visible in the image.  
 
File: ESP 045435 2055troughlayers.jpg | Dark slope streaks in trough  Layers are also visible in the image.  
 
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks  
 
File:PIA22240slopstreaks.jpg | Close view of dark slope streaks  
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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>  Lava flows can also move around an create what appear to be layers, especially if it fluid like water.  Basalt flows can often be that way.<ref>https://www.uahirise.org/ESP_057978_1875</ref>
 
Large areas of Mars are covered with lava flows.<ref>https://en.wikipedia.org/wiki/Volcanology_of_Mars</ref> <ref>Head, J.W.  2007.  The Geology of Mars: New Insights and Outstanding Questions in The Geology of Mars: Evidence from Earth-Based Analogs, Chapman, M., Ed; Cambridge University Press: Cambridge UK</ref> <ref>Carr, Michael H. (1973). "Volcanism on Mars". Journal of Geophysical Research. 78 (20): 4049–4062.</ref> <ref>Barlow, N.G.  2008.  Mars: An Introduction to Its Interior, Surface, and Atmosphere; Cambridge University Press: Cambridge, UK</ref>  Lava flows can also move around an create what appear to be layers, especially if it fluid like water.  Basalt flows can often be that way.<ref>https://www.uahirise.org/ESP_057978_1875</ref>
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:ESP 044840 1620lavaflow.jpg|Lava flows in Phoenicis Lacus quadrangle
 
File:ESP 044840 1620lavaflow.jpg|Lava flows in Phoenicis Lacus quadrangle
 
File:45133 1970lvarafts.jpg|Rafts of lava in Amazonis quadrangle
 
File:45133 1970lvarafts.jpg|Rafts of lava in Amazonis quadrangle
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==Mud Volcanoes==
 
==Mud Volcanoes==
  
Mud volcanoes are very common in the Mare Acidalium quadrangle.  Because they bring up mud from underground, they may hold sources of evidence of life.<ref>Wheatley, D., et al.,  2019.  Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization.  Icarus.  In Press</ref>  Being underground the mud was protected from radiation on the surface.  Methane has been detected on Mars; methane may be produced by certain bacteria.  Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>
+
Mud volcanoes are very common in the Mare Acidalium quadrangle.  Because they bring up mud from underground, they may hold evidence of life.<ref>Wheatley, D., et al.,  2019.  Clastic pipes and mud volcanism across Mars: Terrestrial analog evidence of past Martian groundwater and subsurface fluid mobilization.  Icarus.  In Press</ref>  Being underground the mud was protected from radiation on the surface.  Methane has been detected on Mars; methane may be produced by certain bacteria.  Some scientists speculate that methane may come from mud volcanoes.<ref>https://hirise.lpl.arizona.edu/ESP_055307_2215</ref>
  
 
[[File:52050 2200mudvolcanoes.jpg |thumb|300px|left| Mud volcanoes in Mare Acidalium quadrangle]]
 
[[File:52050 2200mudvolcanoes.jpg |thumb|300px|left| Mud volcanoes in Mare Acidalium quadrangle]]
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==Rootless cones==
 
==Rootless cones==
 +
 +
Rootless Cones are believed 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 which blows out a ring or cone. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form.
  
 
[[File:Wikiesp37643 2060cones.jpg|thumb|300px|right|Rootless cones formed when lava flowed over ice or ice-rich ground.  The sharp bend in the line of cones may have been caused by the lava changing direction.]]
 
[[File:Wikiesp37643 2060cones.jpg|thumb|300px|right|Rootless cones formed when lava flowed over ice or ice-rich ground.  The sharp bend in the line of cones may have been caused by the lava changing direction.]]
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==Honeycomb Terrain==
 
==Honeycomb Terrain==
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 +
[[File: ESP_049330_1425honeycomb.jpg|thumb|300px|right|Honeycomb terrain in Hellas quadrangle]]
  
 
Honeycomb terrain is found on parts of the floor of Hellas Planitia.  It may be due to rising bodies of ice followed by erosion.<ref>Bernhardt, H.; et al. (2016). "The honeycomb terrain on the Hellas basin floor, mars: a case for salt or ice diapirism: hellas honeycombs as salt/ice diapirs". J. Geophys. Res. 121: 714–738.</ref> <ref>Weiss, D., J. Head. 2017. HYDROLOGY OF THE HELLAS BASIN AND THE EARLY MARS CLIMATE: WAS THE HONEYCOMB TERRAIN FORMED BY SALT OR ICE DIAPIRISM? Lunar and Planetary Science XLVIII. 1060.pdf</ref> <ref>Weiss, D.; Head, J. (2017). "Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate". Icarus. 284: 249–263.</ref>
 
Honeycomb terrain is found on parts of the floor of Hellas Planitia.  It may be due to rising bodies of ice followed by erosion.<ref>Bernhardt, H.; et al. (2016). "The honeycomb terrain on the Hellas basin floor, mars: a case for salt or ice diapirism: hellas honeycombs as salt/ice diapirs". J. Geophys. Res. 121: 714–738.</ref> <ref>Weiss, D., J. Head. 2017. HYDROLOGY OF THE HELLAS BASIN AND THE EARLY MARS CLIMATE: WAS THE HONEYCOMB TERRAIN FORMED BY SALT OR ICE DIAPIRISM? Lunar and Planetary Science XLVIII. 1060.pdf</ref> <ref>Weiss, D.; Head, J. (2017). "Salt or ice diapirism origin for the honeycomb terrain in Hellas basin, Mars?: Implications for the early martian climate". Icarus. 284: 249–263.</ref>
  
[[File: ESP_049330_1425honeycomb.jpg|thumb|300px|right|Honeycomb terrain in Hellas quadrangle]]
 
  
 +
<br clear=all>
 
==Fractured Surface and Blocks==
 
==Fractured Surface and Blocks==
  
 +
[[File:44757 2185closeleft.jpg |thumb|300px|left| Rock breaking up into cube-shaped blocks]]
 
In many places on Mars bedrock breaks up into large blocks.  Sometimes the blocks form what look like perfect cubes.  Although one may think these shapes had to be made by intelligent aliens, this is a natural process.  The salt you put on your food also breaks up into cubes.  Check your salt out with a magnifying glass.
 
In many places on Mars bedrock breaks up into large blocks.  Sometimes the blocks form what look like perfect cubes.  Although one may think these shapes had to be made by intelligent aliens, this is a natural process.  The salt you put on your food also breaks up into cubes.  Check your salt out with a magnifying glass.
[[File:44757 2185closeleft.jpg |thumb|300px|left| Rock breaking up into cube-shaped blocks]]
 
  
 +
<br clear=all>
 
==Fractured Ground==
 
==Fractured Ground==
  
 
Some places on Mars break up with large fractures that create a terrain with mesas and valleys. Some of these can be quite pretty.
 
Some places on Mars break up with large fractures that create a terrain with mesas and valleys. Some of these can be quite pretty.
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:ESP 048878 2095fractures.jpg|Wide view of fractured ground
 
File:ESP 048878 2095fractures.jpg|Wide view of fractured ground
 
File:48878 2095fractures.jpg|Close view of fractured ground
 
File:48878 2095fractures.jpg|Close view of fractured ground
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Groups of layers that are tilted are common in some areas of Mars.  They represent material that once covered a wide area.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288</ref>    The layers may be related to changes in the climate in the past.  They may have been shaped by the wind.
 
Groups of layers that are tilted are common in some areas of Mars.  They represent material that once covered a wide area.<ref>Carr, M. 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys. Res. 106, 23571-23593.</ref> <ref>Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288</ref>    The layers may be related to changes in the climate in the past.  They may have been shaped by the wind.
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:ESP 050793 1365pyramids.jpg| Wide view of layered features in Hellas quadrangle
 
File:ESP 050793 1365pyramids.jpg| Wide view of layered features in Hellas quadrangle
 
File:50793 1365layers2.jpg|Close view of layered features in Hellas quadrangle  Each layer may represent a change in the climate.
 
File:50793 1365layers2.jpg|Close view of layered features in Hellas quadrangle  Each layer may represent a change in the climate.
 
File:ESP 035801 2210pyramidsismenius.jpg|Tilted layers in Ismenius Lacus  These sets of layers can often be seen leaning against slopes.
 
File:ESP 035801 2210pyramidsismenius.jpg|Tilted layers in Ismenius Lacus  These sets of layers can often be seen leaning against slopes.
 +
</gallery>
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<gallery class="center"  widths="380px" heights="360px">
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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.
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 +
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.
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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>
  
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Much of the surface of Mars is covered with hard, basalt volcanic rock.  When the rock breaks down it often forms large boulders the size of houses.
 
Much of the surface of Mars is covered with hard, basalt volcanic rock.  When the rock breaks down it often forms large boulders the size of houses.
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas in Elysium quadrangle  Box shows size of football field.
 
File:48878 2095fracturesboulders.jpg| Fractures with boulders in low areas in Elysium quadrangle  Box shows size of football field.
 
File:ESP 045415 2220boulders.jpg|Color view of boulders
 
File:ESP 045415 2220boulders.jpg|Color view of boulders
 
File:45575 2535dunebouldertracks.jpg| Close view of dunes showing boulders with arrows  If you click on image to enlarge, you can see the tracks left by the boulders as they traveled down the dune.
 
File:45575 2535dunebouldertracks.jpg| Close view of dunes showing boulders with arrows  If you click on image to enlarge, you can see the tracks left by the boulders as they traveled down the dune.
 +
45575 2535duneboulders.jpg|Boulder and boulder tracks, as seen by HiRISE under HiWish program  The arrow shows a boulder that  has made a track in the sand as it rolled down dune.
 +
45575 2535dunebouldertracks.jpg|Boulders and tracks, as seen by HiRISE under HiWish program  The arrows show a boulders that have produced a track by rolling down dune.
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</gallery>
 
</gallery>
  
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Some places on Mars have surfaces that are covered with hollows.  Sometimes they form large holes, sometimes curved canyons.  They can be pretty and would be fun to explore on foot in the future.  This terrain may have developed from what has been called ribbed terrain.  Either way, these scenes were caused as ice left the ground.
 
Some places on Mars have surfaces that are covered with hollows.  Sometimes they form large holes, sometimes curved canyons.  They can be pretty and would be fun to explore on foot in the future.  This terrain may have developed from what has been called ribbed terrain.  Either way, these scenes were caused as ice left the ground.
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:ESP 043688 2245hollows.jpg|Wide view of hollows in ground, probably from ice leaving the ground
 
File:ESP 043688 2245hollows.jpg|Wide view of hollows in ground, probably from ice leaving the ground
 
File:ESP 043688 2245closecolor.jpg|Close color view  of hollows in ground, probably from ice leaving the ground
 
File:ESP 043688 2245closecolor.jpg|Close color view  of hollows in ground, probably from ice leaving the ground
 
File:ESP 026042 1470hollows.jpg| Hollows in ground, probably from ice leaving the ground  Location is Hellas Montes Region.
 
File:ESP 026042 1470hollows.jpg| Hollows in ground, probably from ice leaving the ground  Location is Hellas Montes Region.
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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>
  
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Many, large areas of Mars have eroded such that there are many mesas.  Some show layers.  Mesas show how the kind of material that covered a wide area.  Mesas are what are left after the  ground is mostly  eroded.
 
Many, large areas of Mars have eroded such that there are many mesas.  Some show layers.  Mesas show how the kind of material that covered a wide area.  Mesas are what are left after the  ground is mostly  eroded.
  
<gallery class="center" widths="190px" heights="180px" >
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<gallery class="center" widths="380px" heights="360px">
 
File:47441 1800mesaclose.jpg|Mesa with box showing size of football field
 
File:47441 1800mesaclose.jpg|Mesa with box showing size of football field
 
File:47421 1890bigbutte.jpg|Layered mesa with box showing size of football field
 
File:47421 1890bigbutte.jpg|Layered mesa with box showing size of football field
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Mars shows various mass movements like landslides.  There are many steep slopes for material to move down, especially in craters and canyons.
 
Mars shows various mass movements like landslides.  There are many steep slopes for material to move down, especially in craters and canyons.
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:ESP 043963 1550landslide.jpg|Landslide
 
File:ESP 043963 1550landslide.jpg|Landslide
 
File:ESP 045981 1585landslide.jpg|Landslide
 
File:ESP 045981 1585landslide.jpg|Landslide
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==Latitude Dependent Mantle==
 
==Latitude Dependent Mantle==
  
Latitude Dependent Mantle is very common in certain latitudes.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref>    It often appears as a smooth covering.  A certain percentage of it consists of ice.  It may be a major source of water for future colonists because it has a widespread distribution.  Sometimes mantle displays layers because it was deposited at different times.
+
Latitude Dependent Mantle is very common in certain latitudes.<ref>Kreslavsky, M., J. Head, J. 2002. Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.</ref>    It often appears as a smooth covering.  A certain percentage of it consists of ice.  It may be a major source of water for future colonists because it has a widespread distribution.  Sometimes mantle displays layers because it was deposited at different times. It can be as thick as 90 meters.<ref>https://www-sciencedirect-com.wikipedialibrary.idm.oclc.org/science/article/pii/S0019103520305091</ref> <ref>Berman, D., et al.  2021.  Ice-rich landforms of the southern mid-latitudes of Mars: A case study in Nereidum Monte.  Icarus.  Icarus.  Volume 355.  114170</ref>
<gallery class="center" widths="190px" heights="180px" >
+
 
 +
<gallery class="center" widths="380px" heights="360px">
 
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
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File:2509mantlelayers.jpg|Mantle layers with layers
 
File:2509mantlelayers.jpg|Mantle layers with layers
 
</gallery>
 
</gallery>
 
  
 
==Exhumed craters==
 
==Exhumed craters==
  
Exhumed craters seem 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 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.
+
Exhumed craters seem to be in the process of being uncovered.<ref>https://archive.org/details/PLAN-PIA06808</ref> <ref> https://www.uahirise.org/PSP_001374_1805</ref>  The surface of Mars is very old.  Places have been covered, uncovered, and covered again by sediments.  The pictures below show a crater that is being exposed by erosion.  When a crater forms, it will destroy what's under it.  In the example below, only part of the crater is visible.  Had the crater been created  after the layered feature, it would have removed part of the feature and we would see the entire crater.
  
<gallery class="center" widths="190px" heights="180px">
+
<gallery class="center" widths="380px" heights="360px">
  
 
File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters, as seen by HiRISE under HiWish program
 
File:ESP 057652 2215pyramidexhumed.jpg|Wide view of exhumed craters, as seen by HiRISE under HiWish program
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</gallery>
 
</gallery>
  
==Swiss Cheese Terrain==
+
==Swiss Cheese Terrain==
  
 
Parts of Mare Australe show pits that make the surface look like Swiss cheese.<ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
 
Parts of Mare Australe show pits that make the surface look like Swiss cheese.<ref>Thomas,P., M. Malin, P. James, B. Cantor, R. Williams, P. Gierasch
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Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes.  2013.  Time scales of erosion and deposition recorded in the residual south polar cap of mars
 
Icarus: 203, 352–375 http://doi.org/10.1016/j.icarus.2009.05.014</ref> <ref>Thomas, P., W.Calvin, P. Gierasch, R. Haberle, P. James, S. Sholes.  2013.  Time scales of erosion and deposition recorded in the residual south polar cap of mars
 
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee.  2016.  Mass balance of Mars’ residual south polar cap from CTX images and other data Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap.  These circular pits have steep walls that work to focus sunlight, thereby increasing erosion.  For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.<ref> Buhler, Peter,  Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head.  2017.  How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats.  Icarus:  286, 69-9.</ref>
 
Icarus: 225: 923–932 http://doi.org/10.1016/j.icarus.2012.08.038</ref> <ref>Thomas, P., W. Calvin, B. Cantor, R. Haberle, P. James, S. Lee.  2016.  Mass balance of Mars’ residual south polar cap from CTX images and other data Icarus: 268, 118–130 http://doi.org/10.1016/j.icarus.2015.12.038</ref> These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap.  These circular pits have steep walls that work to focus sunlight, thereby increasing erosion.  For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.<ref> Buhler, Peter,  Andrew Ingersoll, Bethany Ehlmann, Caleb Fassett, James Head.  2017.  How the martian residual south polar cap develops quasi-circular and heart-shaped pits, troughs, and moats.  Icarus:  286, 69-9.</ref>
[[File:South Pole Terrain.jpg|thumb|300px|center| Swiss Cheese Terrain near South Pole, as seen by HiRISE]]
+
 
 +
<gallery class="center"  widths="380px" heights="360px">
 +
File:South Pole Terrain.jpg|Swiss Cheese Terrain near South Pole, as seen by HiRISE
 +
File:ESP 058515 0955closechanges.jpg|Changes in Swiss Cheese Terrain from August 2009 to January 2019
 +
</gallery>
 +
 
 +
<gallery class="center" widths="500px">
 +
File:ESP 014274 0955southpole3.jpg|wiss Cheese Terrain August 2009
 +
File:ESP 058515 0955southpole2.jpg|Swiss Cheese Terrain January 2019
 +
</gallery>
  
 
==Ice Cap Layers==
 
==Ice Cap Layers==
  
The northern ice cap of Mars displays many layers of ice that accumulated when the climate changed.  These are visible when there is a canyon in the ice.
+
The northern ice cap of Mars displays many layers of ice that accumulated when the climate changed.  These are visible when there is a canyon in the ice.  The climate of Mars changes greatly due to the large changes in the tilt of Mars.  Mars does not have a large moon to stabilize its' tilt.
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
  
 
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
 
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
 
File:ESP 036863 2670icecaplayers.jpg| Layers exposed in ice cap in Mare Boreum quadrangle
 
ESP_052405_2595icelayers.jpg|Layers in northern ice cap    Some of the layers are at different angles because erosion took away some layers to the right.
 
ESP_052405_2595icelayers.jpg|Layers in northern ice cap    Some of the layers are at different angles because erosion took away some layers to the right.
 +
 +
File:ESP 054515 2595layersicecap.jpg|Layers in northern ice cap  This photo was named picture of the day for January 21, 2019.
 +
 +
File:69629 2605npolarlayerswide.jpg|Layers in northern ice cap
 
</gallery>
 
</gallery>
  
 
==Spiders==
 
==Spiders==
  
The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al.  2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion  Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>  This results in the appearance of dark plumes that are often blown in one direction by local winds.  This dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>
+
The official name for spiders is "araneiforms."As the temperature goes up in the spring, pressurized carbon dioxide gas and dark dust are released from under slabs of ice.<ref>Portyankina, G., et al.  2019. How Martian araneiforms get their shapes: morphological analysis and diffusion-limited aggregation model for polar surface erosion  Icarus. https://doi.org/10.1016/j.icarus.2019.02.032</ref>  This results in the appearance of dark plumes that are often blown in one direction by local winds.  This dust darkens channels under the ice and forms dark shapes that resemble spiders.<ref>Kieffer H, Christensen P, Titus T. 2006 Aug 17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap. Nature: 442(7104):793-6.</ref> <ref>https://mars.nasa.gov/resources/possible-development-stages-of-martian-spiders/</ref> <ref>http://themis.asu.edu/news/gas-jets-spawn-dark-spiders-and-spots-mars-icecap</ref> <ref>http://spaceref.com/mars/how-gas-carves-channels-on-mars.html</ref>  This process was demonstrated in laboratory simulations involving slabs of dry ice placed on glass spheres of different sizes.<ref>https://www.nature.com/articles/s41598-021-82763-7.pdf</ref> <ref>McKeown, L., et al.  2021.  The formation of araneiforms by carbon dioxide venting and vigorous sublimation dynamics under martian atmospheric
[[File:47609 0985spiders.jpg|thumb|300px|right| Spiders and plumes, as seen by HiRISE under HiWish program ]]
+
pressure.  Scientific Reports.</ref> <ref>https://www.livescience.com/spiders-on-mars-explained-dry-ice.html?utm_source=Selligent&utm_medium=email&utm_campaign=LVS_newsletter&utm_content=LVS_newsletter+&utm_term=2946561</ref>
 +
 
 +
<gallery class="center"  widths="380px" heights="360px">
 +
File:47609 0985spiders.jpg|Spiders and plumes, as seen by HiRISE under HiWish program  
 +
File:Spidersmarspedia.jpg|Close view of spiders
 +
</gallery>
  
 
==Polygonal Patterned Ground==
 
==Polygonal Patterned Ground==
Many surfaces on Mars display “polygonal patterned ground.”  The polygons can be of different shapes and sizes.  They are believed to be caused by ice in the ground.  These may still be another marker for underground ice that could be used by future colonists.  Before we land crews on Mars, we may very well have detailed maps for where the colonists can obtain water.
 
  
<gallery class="center" widths="190px" heights="180px" >
+
Many surfaces on Mars display “polygonal patterned ground.”  The polygons can be of different shapes and sizes.  They are believed to be caused by ice in the ground.<ref>https://www.uahirise.org/ESP_047247_1150</ref>  Like permafrost regions on Earth, this permanently frozen water is still active.
 +
 
 +
With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction. Over long periods of cyclic cracking, a honeycomb-like polygonal pattern arises.<ref>https://www.uahirise.org/ESP_066782_1110</ref>
 +
 
 +
The patterns formed may yet be another marker for underground ice that could be used by future colonists.  Before we land crews on Mars, we may very well have detailed maps for where the colonists can obtain water.
 +
 
 +
<gallery class="center" widths="380px" heights="360px">
 
File:ESP 049660 1200polygonswide.jpg|Wide view of large and small polygons
 
File:ESP 049660 1200polygonswide.jpg|Wide view of large and small polygons
  
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</gallery>
 
</gallery>
  
<gallery class="center" widths="190px" heights="180px" >
+
<gallery class="center" widths="380px" heights="360px">
 
File:56148 1145polygonswide.jpg|Wide view of crater floor that is covered with polygons  Low places still contain frost.  Image taken with HiRISE under HiWish program.
 
File:56148 1145polygonswide.jpg|Wide view of crater floor that is covered with polygons  Low places still contain frost.  Image taken with HiRISE under HiWish program.
  
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==Notes about pictures==
 
==Notes about pictures==
  
Most pictures from spacecraft have some sort of enhancement.  For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching.  In that process the darkest parts are set to black while the lightest parts are set to be white.  The colors for HiRISE images are different than the human eye would see.  HiRISE only sees in only 3 colors and sometimes infrared is used  rather than red.  Displaying colors in this way allows us to better identify rocks and minerals.
+
Most pictures from spacecraft have some sort of enhancement.  For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching.  In that process the darkest parts are set to black while the lightest parts are set to be white.  The colors for HiRISE images are different than the human eye would see.  HiRISE only sees in only 3 colors and sometimes infrared is used  rather than red.<ref> https://repository.si.edu/bitstream/handle/10088/19366/nasm_201048.pdf?sequence=1&isAllowed=y</ref> <ref>Delamere, W., et al2010.  Color imaging of Mars by the High Resolution Imaging Science Experiment (HiRISE).  Icarus.  205 pp. 38–52</ref>    Displaying colors in this way allows us to better identify rocks and minerals.
 
HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.<ref>McEwen, A., et al.  2017.  Mars  The  Prestine Beauty of the Red Planet.  University of Arizona Press.  Tucson</ref>
 
HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.<ref>McEwen, A., et al.  2017.  Mars  The  Prestine Beauty of the Red Planet.  University of Arizona Press.  Tucson</ref>
 +
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<gallery class="center"  widths="380px" heights="360px">
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File:ESP 025698 1485pinksalt.jpg|HiRISE image with pink color representing chloride salt.
 +
</gallery>
 +
  
  
 
[[File:60331 1880widecolorband.jpg|Wide view of layers in Danielson Crater  The center band is in color|600pxr|Wide view of layers in Danielson Crater  The center band is in color.]]
 
[[File:60331 1880widecolorband.jpg|Wide view of layers in Danielson Crater  The center band is in color|600pxr|Wide view of layers in Danielson Crater  The center band is in color.]]
                                                Wide view of layers in Danielson Crater  The center band is in color.
+
    Wide view of layers in Danielson Crater  The center band is in color.
  
 
==References==
 
==References==
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*[[Martian gullies]]
 
*[[Martian gullies]]
 
*[[Sublimation]]
 
*[[Sublimation]]
 +
*[[Sublimation landscapes on Mars]]
 +
*[[Water]]
  
* [[Sublimation landscapes on Mars]]
+
==Further reading==
  
*[[Water]]
+
* Lorenz, R.  2014.  The Dune Whisperers.  The Planetary Report: 34, 1, 8-14
 +
* Lorenz, R., J. Zimbelman.  2014.  Dune Worlds:  How Windblown Sand Shapes Planetary Landscapes. Springer Praxis Books / Geophysical Sciences.
  
 
== External links ==
 
== External links ==
 +
 +
*[https://www.uahirise.org/PSP_007820_1505  Layered Sediments in Hellas Planitia]
 +
 +
*[https://www.uahirise.org/PSP_005383_1255 Changes in dust devil tracks]
 +
 +
*[https://static.uahirise.org/images/2020/details/cut/ESP_062948_2175.gif  before and after pictures of a new impact]
 +
 +
*[https://static.uahirise.org/images/2020/details/cut/ESP_063204_1800.gif Looking for Slope Streaks-old and new pictures of streaks]]
 +
 +
* [https://www.youtube.com/watch?v=uopweFSovUM&t=4s Seeing the wonders of Mars with HiRISE under the HiWish program]
 +
 +
* [https://www.youtube.com/watch?v=4dIktDIUTr4 The strange beauty of Mars with HiRISE and HiWish]
 +
 +
* [https://www.youtube.com/watch?v=PAwtP23EHGc 0:25 / 0:48 Zooming in on Mars with HiRISE images from HiWish program]
 +
 +
*[https://www.youtube.com/watch?v=b7q1Xyz_LBc Features of Mars with HiRISE under HiWish program]  Shows nearly all major features discovered on Mars.  This would be good for teachers covering Mars.
 +
 +
*[https://www.youtube.com/watch?v=Rws1mj1mnIc A trip to Mars with Hubble, Viking, and HiRISE]
 +
 +
*[https://www.youtube.com/watch?v=EtyLFJGV9nw Mars through HiRISE under the HiWish program]
 +
 +
*[https://www.youtube.com/watch?v=_g8QcVvaHrk Beautiful Mars as seen by HiRISE under HiWish program]
 +
 +
* [https://www.youtube.com/watch?v=nhYQEzK-MYE&t=17s HiRISE images from HiWish Program]
  
 
* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]
 
* [https://www.youtube.com/watch?v=_sUUKcZaTgA Martian Ice - Jim Secosky - 16th Annual International Mars Society Convention]

Latest revision as of 08:58, 20 February 2024

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


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

Viking 1

Rocks and dunes, as seen from Viking 1 Holes were dug by the digging tool. Part of the meteorology boom is visible.

Viking 1 was the first successful spacecraft to land on Mars. It landed on July 20, 1976 at 22.27 N and 47.95 W (312.05 E). July 20th was also the date when we first landed on the moon in 1969.

Viking 2

View from Viking 2

Viking 2 landed on September 3, 1976 at 47.64 N and 275.71 W (84.29 E).

Mars Pathfinder

Wide view from Mars pathfinder, showing Sojourner Rover

The Mars Pathfinder landed on July 4, 1997 at 19 degrees 7’ 48” in Ares Vallis.

Spirit Rover

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

Opportunity Rover

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

Phoenix

Wide view from Phoenix lander Solar panels are visible.

Phoenix landed in the far North of Mars on May 25, 2008 at 68.22 N and 125.7 W (234.3 E) in Vastitas Borealis.

Curiosity Rover

Early view from Curiosity Mount Sharp is in the distance. The shadow of Rover is visible. Mount Sharp at a height of about 3.4 miles is taller than Mt. Whitney in California.

The Curiosity Rover landed on August 6, 2012 at Gale Crater in Aeolis Palus at 4.5895 S and 137.4417 E (222.5583 W). By this time scientists were able to be more precise with their landings, so Curiosity has been able to get views of Mars that are pretty exciting.


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

Dunes

The Martian surface displays many beautiful dark dunes. For many years, scientists thought dark dunes were composed of the grains of sand from the volcanic rock basalt; this was confirmed by rovers on the surface.[1] The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.

The presence of dunes on Mars and the observations that they do change is clear proof that there is air on Mars. However, we must remember that its atmosphere is only about 1 % as dense as the Earth's. Hence, a wind speed of a 60-mph storm on Mars would feel more like 6 mph (9.6 km/hr).[2]

Colorful dunes in the Mare Tyrrhenum quadrangle[4]

                             Colorful dunes in the Mare Tyrrhenum quadrangle[5]

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

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

Layers

Many places on Mars show rocks arranged in layers. Volcanoes, wind, or water can produce layers.[6] Layers can be hardened by the action of groundwater.

Layers and fault in Firsoff Crater

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

Layers on the floor of Danielson Crater taken under the HiWish program Box shows size of a football field.

Glaciers

There are large areas on Mars that contain what is thought to be ice moving under a cover of debris. A few meters of debris can preserve ice for long periods of time.[7]

Several types of landforms have been identified as probably dirt and rock debris covering huge deposits of ice.[8] [9] [10] [11] Concentric crater fill (CCF) contains dozens to hundreds of concentric ridges that are caused by the movements of sometimes hundreds of meter thick accumulations of ice in craters.[12] [13] Lineated valley fill (LVF) are lines of ridges in valleys.[14] [15] [16] These lines may have developed as other glaciers moved down valleys. Some of these glaciers seem to come from material sitting around mesas and buttes.[17] Lobate debris aprons (LDA) is the name given to these glaciers. All of these features that are believed to contain large amounts of ice are found in the mid-latitudes in both the Northern and Southern hemispheres.[18] [19] [20]

Mesa with Lobate Debris Aprons (LDA) Orbiting radars have detected ice in LDA’s under a thin cover of debris.
Lobate Debris Aprons (LDA) around a mound
Labeled view of Lineated Valley Flow and glacier


Gullies

Martian gullies are networks of narrow channels and their associated downslope deposits, found on steep slopes. A high concentration occurs near 40 degrees north and south of the equator. Usually, each gully has an alcove at its head, a fan-shaped apron at its base, and a channel linking the two.[21] They are believed to be relatively young because they have few, if any craters. They were believed to be caused by recent running water, but with more observations other ideas emerged. In summary of our present understanding of gullies it can be said: A number of studies have demonstrated that gullies are being modified on present day Mars. [22] [23] [24] [25] Today, liquid water cannot exist on the Red planet because the both the pressure and the temperature are too low. Researchers have proposed other mechanisms that could account for gully formation without liquid water.[26] Most involve dry ice (solid carbon dioxide) accumulating during cold seasons and then changing to a gas in the spring. The gas coming off could start material moving down slopes. The gas mixed with sand and other debris could act like water to erode channels. Also, pieces of dry ice could easily side down due to the lubricating effect of gas coming off the dry ice.

However, one wonders if these processes could account for the formation of all the gullies. Maybe, liquid water was sometimes necessary, especially to move large boulders. A study of over 700 sites, published in 2022 in Icarus, concluded that liquid water would not have been needed. During the duration of the study many large boulders were moved—one being 5 meters across. Many types of changes were seen in gullies. Some channels were extended, new channels were formed, and other channels were filled with new debris.[27] [28] Perhaps, some water was involved in the past, but all the gullies seen today could have been made without water.

Channels

There are thousands of channels that were probably caused by running water in the past on Mars. Some are large; some are tiny.[30] [31] [32] [33] [34]

Inverted relief

Some places on Mars show inverted relief. In these locations, a stream bed may be a raised feature, instead of a valley. Inverted former stream channels may be caused by the deposition of large rocks, cementation, or maybe by lava moving down the channel. In either case later erosion would erode the surrounding land and leave the old channel as a raised ridge because the ridge would be more resistant to erosion. The image below, taken with HiRISE show curved ridges that are old channels that have become inverted. They have the shape of streams but are above ground.[36]


Possible inverted streams, as seen by HiRISE under HiWish program


Inverted stream, a stream bed has been filled with hard materials that did not erode away like the surroundings

Troughs

The great weight of several huge volcanoes on Mars has stretched the crust and made it break into cracks called, “troughs” or “fossae.” Some of them show evidence that lava and/or water have come out of them in the past. They can be very long.[37] [38] [39]

Craters

Most of the surface of Mars is over a billion years old. Because Mars has not had active plate tectonics for a very long time (if it ever had active plate tectonics), impact craters stay for a long time. So, impact craters are a major surface feature. There is a rich variety of craters on the planet.[40] [41] We have found that Mars is hit by 200 impacts/year.[42] [43] [44]


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


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


Scientists love to study central peaks of craters because they contain samples of material from deep under a surface. Durning an impact, the ground is pushed down. It then rebounds and brings up rocks from deep underground.[49]

Scalloped Terrain

Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is especially prominent in the region of Utopia Planitia.[50] [51] Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as "scalloped depressions" or simply "scallops". Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. The usual scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp.[52] [53] [54] Scalloped topography may be of great importance for future colonization of Mars because it may point to deposits of pure ice.[55] [56]


Brain Terrain

Brain terrain is a region of maze-like ridges 3–5 meters high. A person could wander between these ridges like a rat in a maze. Some ridges may consist of an ice core, so they may be sources of water for future colonists.[57]

Ribbed terrain

Ribbed terrain forms as ice leaves the ground along cracks in a process called " sublimation." Much of the ground is ice so that when the ice disappears the ground collapses.[59]

Wide view of ribbed terrain in Ismenius Lacus quadrangle

Ribbed terrain
Ribbed terrain The box is the size of a football field

Linear Ridge Networks

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

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

This terrain appears over much of the planet. However, there is a heavy concentration of these features, also called irregular polygonal ridge networks, in the Nili Fossae region.[60] These networks consist of groups of narrow ridges that often meet at close to right angles. We are not sure of how it originated.[61] They may have been caused by fluids moving into cracks that were created by impacts. The fluids then became hard and erosion resistant.[62] [63] [64] [65] [66] [67] [68] We are not totally sure of the exact ways these ridges were created. Over 14,000 people from around the world helped map them, so that scientists could better understand them. Some ridges contain clays, so water may have been involved in their formation because clays need water to form.[69] [70]

Yardangs

Yardangs form from fine-grained material. They are shaped by the wind and show the direction of the prevailing winds. Much of this fine-grained material probably has its origin in the many large volcanoes on the planet. Yardangs are especially common in what's called the "Medusae Fossae Formation." This formation is found in the Amazonis quadrangle and near the equator.[71] Because they exhibit very few impact craters they are believed to be relatively young.[72]

Dust Devil Tracks

Dust devil tracks can be very beautiful. They are made by giant dust devils removing bright colored dust from the Martian surface; consequently exposing a dark layer.[73] Dust devils on Mars have been photographed both from the ground and from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.[74] The dust devils can be 650 meters high and 50 meters across.[75] The pattern of the tracks has been shown to change every few months.[76]

Dust devils are common.[77] One team of researchers have calculated that on average 1 dust devil happens every sol (day on Mars) for each square kilometer.[78] [79] In the first 216 Martian days (Sols), the Perseverance Rover in Jezero Crater found that at least four dust devils passed Perseverance on a typical Martian day and that more than one per hour passes by during a peak hourlong period just after noon.[80] [81] [82] Perseverance Rover recorded a tall dust devil in the distance on Aug. 30, 2023. Scientists calculated that the dust devil was about 2.5 miles (4 kilometers) away and was moving east to west at about 12 mph (19 kph). Its width was about 200 feet (60 meters). Even though only the bottom 387 feet (118 meters) of the devil was visible in the camera frame, scientists estimated its total height at about 1.2 miles (2 kilometers) using the dust devil's shadow.[83]

Dark Slope Streaks

Dark slope streaks are avalanche-like features common on dust-covered slopes, especially in the equatorial regions.[84] These streaks have never been observed on the Earth.[85] They form in relatively steep terrain, such as along cliffs and crater walls.[86] The darkest streaks are only about 10% darker than their surroundings. The streaks seem much darker because of contrast enhancement in the image processing.[87]

Dry ice accumulates just under the surface during cold Martian nights and then changes to a gas in the morning. That gas creates enough wind to disturb dust particles and send them down steep slopes. As the bright dust slides down it reveals the underlying dark volcanic rocks. This process was discovered by measuring temperatures in the area. At the recorded temperatures, carbon dioxide from the air should have frozen on the surface, but it was not visible. It was concluded that the dry ice was forming just under the surface rather than on top..[88] [89]

Lava

Large areas of Mars are covered with lava flows.[90] [91] [92] [93] Lava flows can also move around an create what appear to be layers, especially if it fluid like water. Basalt flows can often be that way.[94]

Mud Volcanoes

Mud volcanoes are very common in the Mare Acidalium quadrangle. Because they bring up mud from underground, they may hold evidence of life.[95] Being underground the mud was protected from radiation on the surface. Methane has been detected on Mars; methane may be produced by certain bacteria. Some scientists speculate that methane may come from mud volcanoes.[96]

Mud volcanoes in Mare Acidalium quadrangle
Close view of mud volcano, as seen by HiRISE
Mud volcanoes

Rootless cones

Rootless Cones are believed to be caused by lava flowing over ice or ground containing ice.[97] [98] Heat from the lava causes the ice to quickly change to steam which blows out a ring or cone. Some of the forms do not have the shape of rings or cones because maybe the lava moved too quickly; thereby not allowing a complete cone shape to form.

Rootless cones formed when lava flowed over ice or ice-rich ground. The sharp bend in the line of cones may have been caused by the lava changing direction.
Close view of rootless cones, as seen by HiRISE under the HiWish program
Close view of rootless cones showing wakes caused by lava moving
Wide view of field of rootless cones in Elysium quadrangle

Honeycomb Terrain

Honeycomb terrain in Hellas quadrangle

Honeycomb terrain is found on parts of the floor of Hellas Planitia. It may be due to rising bodies of ice followed by erosion.[99] [100] [101]



Fractured Surface and Blocks

Rock breaking up into cube-shaped blocks

In many places on Mars bedrock breaks up into large blocks. Sometimes the blocks form what look like perfect cubes. Although one may think these shapes had to be made by intelligent aliens, this is a natural process. The salt you put on your food also breaks up into cubes. Check your salt out with a magnifying glass.


Fractured Ground

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

Dipping layers

Groups of layers that are tilted are common in some areas of Mars. They represent material that once covered a wide area.[102] [103] The layers may be related to changes in the climate in the past. They may have been shaped by the wind.

Boulders

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

Hollows

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

Mesas

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

Landslides

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

Latitude Dependent Mantle

Latitude Dependent Mantle is very common in certain latitudes.[104] It often appears as a smooth covering. A certain percentage of it consists of ice. It may be a major source of water for future colonists because it has a widespread distribution. Sometimes mantle displays layers because it was deposited at different times. It can be as thick as 90 meters.[105] [106]

Exhumed craters

Exhumed craters seem to be in the process of being uncovered.[107] [108] The surface of Mars is very old. Places have been covered, uncovered, and covered again by sediments. The pictures below show a crater that is being exposed by erosion. When a crater forms, it will destroy what's under it. In the example below, only part of the crater is visible. Had the crater been created after the layered feature, it would have removed part of the feature and we would see the entire crater.

Swiss Cheese Terrain

Parts of Mare Australe show pits that make the surface look like Swiss cheese.[109] [110] [111] [112] These pits are in a 1-10 meter thick layer of dry ice that lies on a much larger water ice cap. These circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters in necessary.[113]

Ice Cap Layers

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

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.[114] This results in the appearance of dark plumes that are often blown in one direction by local winds. This dust darkens channels under the ice and forms dark shapes that resemble spiders.[115] [116] [117] [118] This process was demonstrated in laboratory simulations involving slabs of dry ice placed on glass spheres of different sizes.[119] [120] [121]

Polygonal Patterned Ground

Many surfaces on Mars display “polygonal patterned ground.” The polygons can be of different shapes and sizes. They are believed to be caused by ice in the ground.[122] Like permafrost regions on Earth, this permanently frozen water is still active.

With the changing seasons, alternate cooling and warming causes the ice-cemented soil to contract and expand. With the right conditions, cracks are made into the hard frozen ground releasing the stresses caused by contraction. Over long periods of cyclic cracking, a honeycomb-like polygonal pattern arises.[123]

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

Notes about pictures

Most pictures from spacecraft have some sort of enhancement. For many views of Mars there is not much contrast, so the contrast is enhanced in a process known as stretching. In that process the darkest parts are set to black while the lightest parts are set to be white. The colors for HiRISE images are different than the human eye would see. HiRISE only sees in only 3 colors and sometimes infrared is used rather than red.[124] [125] Displaying colors in this way allows us to better identify rocks and minerals. HiRISE images are about 5 km wide with a 1 km wide band in the center that is in color.[126]


Wide view of layers in Danielson Crater The center band is in color.

    Wide view of layers in Danielson Crater  The center band is in color.

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See Also

Further reading

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

External links