Difference between revisions of "Amazonis quadrangle"

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This area is considered to be among the youngest parts of Mars because it has a very low density of craters. The Amazonia period is named after this area.  This quadrangle contains special, unusual features called the Medusae Fossae Formation and Sulci.  As per the rest of Mars, this region contains some very beautiful landscapes.
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This area is considered to be among the youngest parts of Mars because it has a very low density of craters. The Amazonia period is named after this area.  This quadrangle contains special, unusual features called Sulci and the Medusae Fossae Formation.  As per the rest of Mars, this region contains some very beautiful landscapes.
The Amazonis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) . The Amazonis quadrangle is also referred to as MC-8 (Mars Chart-8).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>  The quadrangle covers the area from 0° to 30° north latitude and 135° to 180° west longitude (225-180 E ). The Amazonis quadrangle contains the region called Amazonis Planitia.   
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The Amazonis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) . The Amazonis quadrangle is also referred to as MC-8 (Mars Chart-8).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>  The quadrangle covers the area from 0° to 30° north latitude and 135° to 180° west longitude (225-180 E ). The Amazonis quadrangle contains the classic region called Amazonis Planitia.  
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In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this region. The origins and significance of all features will be explained as they are currently understood.
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==Name==
 
==Name==
Its name derives from the mythical land of the Amazons.  In Greek mythology, the Amazons  were a tribe of warrior women believed to live in Asia Minor.  In this myth, amazons were the daughters of Ares and Harmonia (mythology) (a nymph of the Akmonian Wood).  They were brutal and aggressive--their main concern in life was war.<ref>https://www.theoi.com/Olympios/AresFamily.html#Amazones Apollonius Rhodius, ''Argonautica'' (''Book 2'', ln. 989)]</ref> <ref>http://sacred-texts.com/cla/argo/argo23.htm ARGONAUTICA, BOOK 2</ref>  
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Its name derives from the mythical land of the Amazons.  In Greek mythology, the Amazons  were a tribe of warrior women believed to live in Asia Minor.  In this myth, Amazons were the daughters of Ares and Harmonia (mythology) (a nymph of the Akmonian Wood).  They were brutal and aggressive--their main concern in life was war.<ref>https://www.theoi.com/Olympios/AresFamily.html#Amazones Apollonius Rhodius, ''Argonautica'' (''Book 2'', ln. 989)]</ref> <ref>http://sacred-texts.com/cla/argo/argo23.htm ARGONAUTICA, BOOK 2</ref>  
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==Medusae Fossae Formation==
 
==Medusae Fossae Formation==
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The Amazonis quadrangle is of great interest to scientists because it contains a major part of a formation, called the Medusae Fossae Formation. This unit is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. The surface of the formation has been eroded by the wind into a series of linear ridges called yardangs. These ridges generally point in direction of the prevailing winds that carved them and demonstrate the erosive power of Martian winds. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles,<ref>Grotzinger, J. and R. Milliken (eds.)  2012.  Sedimentary Geology of Mars.  SEPM</ref> and was most likely formed by the deposition of wind-blown dust or volcanic ash. Using a global climate model, a group of researchers concluded that the Medusae Fossae Formation could have easily been formed from ash from the volcanoes Apollinaris Mons, Arsia Mons, and possibly from Pavonis Mons.<ref>Kerber L., et al.  2012.  The disporsal of pyroclasts from ancient explosive volcanoes on Mars:  Implications for the friable layered deposits.  Icarus.  219:358-381.</ref>  Another evidence for a fine-grained composition is that the area gives almost no radar return.  For this reason it has been called a "stealth" region.<ref>ISBN 978-0-521-85226-5</ref>  Layers are seen in parts of the formation.  Images from spacecraft show that they have different degrees of hardness probably because of significant variations in the physical properties, composition, particle size, and/or cementation. Very few impact craters are visible throughout the area so the surface is relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>  Researchers found that nearly all the dust that falls out of the atmosphere and that coats everything on Mars has its origin in the Medusae Fossae formation.<ref>http://redplanet.asu.edu/?tag=medusae-fossae-formation</ref>  It turns out that the chemical elements (sulfur and chlorine) in this formation, in the atmosphere, and covering the surface are the same.  The amount of dust on Mars is sufficient to form a 2 to 12 meters thick layer over the entire planet.<ref>https://www.sciencedaily.com/releases/2018/07/180724120854.htm</ref> <ref>Lujendra Ojha, Kevin Lewis, Suniti Karunatillake, Mariek Schmidt. The Medusae Fossae Formation as the single largest source of dust on Mars. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05291-5</ref>  Since there are relatively few depositional features in the Medusae Fossae Formation, most of the materials being eroded are probably small enough to be suspended in the atmosphere and transported long distances.<ref>Tanaka, K. L. Dust and ice deposition in the Martian geologic record. Icarus 144, 254–266 (2000).</ref>
 
The Amazonis quadrangle is of great interest to scientists because it contains a major part of a formation, called the Medusae Fossae Formation. This unit is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. The surface of the formation has been eroded by the wind into a series of linear ridges called yardangs. These ridges generally point in direction of the prevailing winds that carved them and demonstrate the erosive power of Martian winds. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles,<ref>Grotzinger, J. and R. Milliken (eds.)  2012.  Sedimentary Geology of Mars.  SEPM</ref> and was most likely formed by the deposition of wind-blown dust or volcanic ash. Using a global climate model, a group of researchers concluded that the Medusae Fossae Formation could have easily been formed from ash from the volcanoes Apollinaris Mons, Arsia Mons, and possibly from Pavonis Mons.<ref>Kerber L., et al.  2012.  The disporsal of pyroclasts from ancient explosive volcanoes on Mars:  Implications for the friable layered deposits.  Icarus.  219:358-381.</ref>  Another evidence for a fine-grained composition is that the area gives almost no radar return.  For this reason it has been called a "stealth" region.<ref>ISBN 978-0-521-85226-5</ref>  Layers are seen in parts of the formation.  Images from spacecraft show that they have different degrees of hardness probably because of significant variations in the physical properties, composition, particle size, and/or cementation. Very few impact craters are visible throughout the area so the surface is relatively young.<ref>http://themis.asu.edu/zoom-20020416a</ref>  Researchers found that nearly all the dust that falls out of the atmosphere and that coats everything on Mars has its origin in the Medusae Fossae formation.<ref>http://redplanet.asu.edu/?tag=medusae-fossae-formation</ref>  It turns out that the chemical elements (sulfur and chlorine) in this formation, in the atmosphere, and covering the surface are the same.  The amount of dust on Mars is sufficient to form a 2 to 12 meters thick layer over the entire planet.<ref>https://www.sciencedaily.com/releases/2018/07/180724120854.htm</ref> <ref>Lujendra Ojha, Kevin Lewis, Suniti Karunatillake, Mariek Schmidt. The Medusae Fossae Formation as the single largest source of dust on Mars. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05291-5</ref>  Since there are relatively few depositional features in the Medusae Fossae Formation, most of the materials being eroded are probably small enough to be suspended in the atmosphere and transported long distances.<ref>Tanaka, K. L. Dust and ice deposition in the Martian geologic record. Icarus 144, 254–266 (2000).</ref>
  
An analysis of data from the ''[[2001 Mars Odyssey]]'' Neutron Spectrometer revealed that portions of the Medusae Fossae Formation contain water.<ref>Wilson, J. et al.  2018.  Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data.  Icarus: 299, 148-160.</ref>
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An analysis of data from the 2001 Mars Odyssey Neutron Spectrometer revealed that portions of the Medusae Fossae Formation contain water.<ref>Wilson, J. et al.  2018.  Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data.  Icarus: 299, 148-160.</ref>
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Image:Medusae Fossae THEMIS.jpg|Medusae Fossae Formation and its location relative to Olympus Mons, as seen by THEMIS.
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Image:Medusae Fossae Remnant.jpg|Plateau made up of Medusae Fossae materials and rootless cones, as seen by HiRISE
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Image:23664medussa.jpg|Yardangs in the Medusae Fossae formation
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WikiESP 035558 1830yardang.jpg|Yardangs, as seen by HiRISE under [[HiWish program]] Location is near Gordii Dorsum in the Amazonis quadrangle.  These yardangs are in the upper member of the Medusae Fossae Formation.
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35558 1830yardangs.jpg|Yardangs Location is near Gordii Dorsum in the Amazonis quadrangle. Note: this is an enlargement of previous image.
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35558 1830yardangsclose.jpg|Yardangs Location is near Gordii Dorsum in the Amazonis quadrangle. Note: this is an enlargement of previous image.
  
Image:Medusae Fossae THEMIS.jpg|[[Medusae Fossae Formation]] and its location relative to Olympus Mons, as seen by THEMIS.
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WikiESP 036429 1925yardangscrater.jpg|Yardangs near a crater Location is in the Amazonis quadrangle.
Image:Medusae Fossae Remnant.jpg|Plateau made up of Medusae Fossae materials and rootless cones, as seen by [[HiRISE]]
 
Image:23664medussa.jpg|Yardangs in the Medusae Fossae formation, as seen by HiRISE under [[HiWish program]].
 
WikiESP 035558 1830yardang.jpg|Yardangs, as seen by HiRISE under HiWish program Location is near Gordii Dorsum in the Amazonis quadrangle.  These yardangs are in the upper member of the Medusae Fossae Formation.
 
35558 1830yardangs.jpg|Yardangs, as seen by HiRISE under HiWish program Location is near Gordii Dorsum in the Amazonis quadrangle. Note: this is an enlargement of previous image.
 
35558 1830yardangsclose.jpg|Yardangs, as seen by HiRISE under HiWish program Location is near Gordii Dorsum in the Amazonis quadrangle. Note: this is an enlargement of previous image.
 
WikiESP 036429 1925yardangscrater.jpg|Yardangs near a crater, as seen by HiRISE under HiWish program Location is in the Amazonis quadrangle.
 
 
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File:ESP 054784 1890yardangsclosecolor.jpg|Close, color view of yardangs,  as seen by HiRISE under HiWish program
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File:54784 1890yardangsclosecolor.jpg|Close, color view of yardangs  Box shows size of a football field.
File:54784 1890yardangformsclosecolor.jpg|Close, color view of yardangs,  as seen by HiRISE under HiWish program
 
File:54784 1890yardangsclosecolor.jpg|Close, color view of yardangs,  as seen by HiRISE under HiWish program Box shows size of a football field.
 
 
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==Sulci==
 
==Sulci==
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A very rugged terrain extends from the base of Olympus Mons, the largest volcano on Mars.  This terrain  is called Lycus Sulci.  Sulci is a Latin term for the furrows on the surface of a brain, so Lycus Sulci has many furrows or grooves.  The furrows are huge—up to a full kilometer deep.<ref>http://themis.asu.edu/zoom-20030606a</ref>  It would be extremely difficult to walk across it or to land a space ship there.  A picture of this area is shown below.
 
A very rugged terrain extends from the base of Olympus Mons, the largest volcano on Mars.  This terrain  is called Lycus Sulci.  Sulci is a Latin term for the furrows on the surface of a brain, so Lycus Sulci has many furrows or grooves.  The furrows are huge—up to a full kilometer deep.<ref>http://themis.asu.edu/zoom-20030606a</ref>  It would be extremely difficult to walk across it or to land a space ship there.  A picture of this area is shown below.
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Image:Sulci in Amazonis.JPG|Sulci in Amazonis, as seen by [[THEMIS]].  "Sulci" in Mars geography language means a furrow, like a furrow on a brain's surface.  This Sulci came from the basal scarp of [[Olympus Mons]]
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Image:Lycus Sulci.JPG|[[Lycus Sulci]], as seen by HiRISE.  Click on image for a better view of [[Dark Slope Streaks]].
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Image:Sulci in Amazonis.JPG|Sulci in Amazonis, as seen by THEMIS.  "Sulci" in Mars geography language means a furrow, like a furrow on a brain's surface.  This Sulci came from the basal scarp of [[Olympus Mons]]
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44802buttes.jpg|Layered features in Lycus Sulci, as seen by HiRISE under HiWish program
 
44802buttes.jpg|Layered features in Lycus Sulci, as seen by HiRISE under HiWish program
44802streaks.jpg|Dark slope streaks on mound in Lycus Sulci, as seen by HiRISE under HiWish program
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44802streaks.jpg|Dark slope streaks on mound in Lycus Sulci
 
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==Columnar Jointing==
 
==Columnar Jointing==
Lava flows sometimes cools to form large groups of more-or-less equally sized columns.<ref>http://volcano.oregonstate.edu/columnar-jointing</ref> Since Mars is largely covered by lava flow, it was expected that these joints were on Mars.  With the superior resolution of the HiRISE images, scientists finally found columnar jointing in various locations in 2009.  Pictures below show examples of columnar jointing both on Mars and on the Earth.  Many tourists travel to see these formations in our National Parks, like Yellowstone.
 
  
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Image:Columnar jointing, Marte Vallis.jpg|[[Columnar jointing]] in a crater in [[Marte Vallis]].
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[[File:Columnar jointing, Marte Vallis.jpg|600pxr|Columnar jointing in a crater in Marte Vallis]]
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                        Columnar jointing in a crater in Marte Vallis
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Lava flows sometimes cool to form large groups of more-or-less equally sized columns.<ref>http://volcano.oregonstate.edu/columnar-jointing</ref> Since Mars is largely covered by lava flow, it was expected that these joints were on Mars.  With the superior resolution of the HiRISE images, scientists finally found columnar jointing in various locations in 2009.  Pictures below show examples of columnar jointing both on Mars and on the Earth.  Many tourists travel to see these formations in our National Parks, like Yellowstone.
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Image:Parana traps.JPG|Columnar jointing on the Earth.
 
Image:Parana traps.JPG|Columnar jointing on the Earth.
 
Image:Sounkyo 01 a.jpg|Columnar jointing on the Earth.
 
Image:Sounkyo 01 a.jpg|Columnar jointing on the Earth.
Image:Columnar Jointing in Yellowstone.JPG|Columnar Jointing in [[Yellowstone National Park]].
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Image:Columnar Jointing in Yellowstone.JPG|Columnar Jointing in Yellowstone National Park.
 
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==Craters==
 
==Craters==
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Craters give us insight into what lies under the ground.  Since the collision that produces an impact crater is like a powerful explosion, rocks from deep underground are tossed onto the surface.  Hence, by examining the material or ejecta thrown out by the impact, we can see what lies deep under the surface.  Some craters, especially the more recent ones, will display layers on their walls.  These layers can help us tell the kinds of rocks that were formed in the past.  For example, layers that contain dark, blocky boulders likely originated as lava flows.
 
Craters give us insight into what lies under the ground.  Since the collision that produces an impact crater is like a powerful explosion, rocks from deep underground are tossed onto the surface.  Hence, by examining the material or ejecta thrown out by the impact, we can see what lies deep under the surface.  Some craters, especially the more recent ones, will display layers on their walls.  These layers can help us tell the kinds of rocks that were formed in the past.  For example, layers that contain dark, blocky boulders likely originated as lava flows.
 
As craters get larger (greater than 10 km in diameter) they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/</ref> The peak is caused by a rebound of the crater floor following the impact.<ref name="Kieffer1992">{{cite book|author=Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|accessdate=7 March 2011|date=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7</ref>  Scientists are eager to examine those central peaks because they contain samples of rocks from deep underground.  Instruments, called spectroscopes, can tell us the mineral composition of these rocks.   
 
As craters get larger (greater than 10 km in diameter) they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/</ref> The peak is caused by a rebound of the crater floor following the impact.<ref name="Kieffer1992">{{cite book|author=Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|accessdate=7 March 2011|date=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7</ref>  Scientists are eager to examine those central peaks because they contain samples of rocks from deep underground.  Instruments, called spectroscopes, can tell us the mineral composition of these rocks.   
We believe that pits in Tooting Crater are caused by hot ejecta falling on ground containing ice.  The pits are formed by heat forming steam that rushes out from groups of pits simultaneously, thereby blowing away from the pit ejecta.<ref>Boyce, J. et al.  2012.  Origin of small pits in martian impact craters.  Icarus.  221: 262-275.</ref><ref>Tornabene, L. et al.  2012.  Widespread crater-related pitted materials on Mars.  Further evidence for the role of target volatiles during the impact process.  Icarus.  220: 348-368.</ref>
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We believe that pits in Tooting Crater are caused by hot ejecta falling on ground containing ice.  The pits are formed by heat forming steam that rushes out from groups of pits simultaneously, thereby blowing away from the pit ejecta.<ref>Boyce, J. et al.  2012.  Origin of small pits in martian impact craters.  Icarus.  221: 262-275.</ref> <ref>Tornabene, L. et al.  2012.  Widespread crater-related pitted materials on Mars.  Further evidence for the role of target volatiles during the impact process.  Icarus.  220: 348-368.</ref>
  
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Based on study of years of HiRISE images, researchers believe over 200 new craters are formed each year on Mars, based on study of years of HiRISE images.<ref>http://www.space.com/21198-mars-asteroid-strikes-common.html | title=Pow! Mars Hit by Space Rocks 200 Times a Year</ref><ref>http://www.universetoday.com/109020/brand-new-impact-crater-shows-up-on-mars/ |title = Brand New Impact Crater Shows up on Mars|</ref>
  
  
[[File:PIA18381-Mars-FreshAsteroidImpact2012-Before27March-After28March.jpg|thumb|right|200px|Fresh [[asteroid]] impact on Mars {{coord|3.34|N|219.38|E|globe:Mars}} - ''before''/March 27 & ''after''/March 28, 2012 ([[Mars Reconnaissance Orbiter|MRO]]).<ref name="NASA-20140522">{{cite web |last=Webster |first=Guy |last2=Brown |first2=Dwayne |title=NASA Mars Weathercam Helps Find Big New Crater |url=http://www.jpl.nasa.gov/news/news.php?release=2014-162 |date=22 May 2014 |work=[[NASA]] |accessdate=22 May 2014 }}</ref>]]
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[[File:PIA18381-Mars-FreshAsteroidImpact2012-Before27March-After28March.jpg|thumb|right|200px|Fresh [[asteroid]] impact on Mars 3.34 N and 219.38 E| - ''before''/March 27 & ''after''/March 28, 2012<ref>Webster |first=Guy |last2=Brown |first2=Dwayne |title=NASA Mars Weathercam Helps Find Big New Crater |url=http://www.jpl.nasa.gov/news/news.php?release=2014-162 |date=22 May 2014 |work=[[NASA]]</ref>]]
  
 
==Pedestal Craters==
 
==Pedestal Craters==
  
A pedestal crater is an impact crater with its ejecta sitting on a raised platform above the surrounding terrain. They form when an impact crater ejects material which forms an erosion resistant layer, thus protecting the immediate area from erosion. As a result of this hard covering, the crater and its ejecta become elevated, after erosion removes the softer material beyond the ejecta.  Some pedestals have been accurately measured to be hundreds of meters above the surrounding area.  This means that hundreds of meters of material were eroded away.  Pedestal craters were first observed during the Mariner missions.<ref>Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''.  LPSC</ref> <ref>http://themis.asu.edu/feature/8</ref>
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A pedestal crater is an impact crater with its ejecta sitting on a raised platform above the surrounding terrain. They form when an impact crater ejects material which forms an erosion resistant layer, thus protecting the underlying materials from erosion. As a result of this hard covering, the crater and its ejecta become elevated, after erosion removes the softer material beyond the ejecta.  Some pedestals have been accurately measured to be hundreds of meters above the surrounding area.  This means that hundreds of meters of material were eroded away.  Pedestal craters were first observed during the Mariner missions.<ref>Bleacher, J. and S. Sakimoto. ''Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates''.  LPSC</ref> <ref>http://themis.asu.edu/feature/8</ref>
  
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Image:Pedestal crater and streaks.jpg|[[Pedestal crater]] in Amazonis with Dark Slope Streaks, as seen by HiRISE.
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Image:Pedestal crater and streaks.jpg|Pedestal crater in Amazonis with Dark Slope Streaks, as seen by HiRISE.
ESP 045462 1920pedestal.jpg|Pedestal crater with layers, as seen by HiRISE under HiWish program
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ESP 045462 1920pedestal.jpg|Pedestal crater with layers, as seen by HiRISE under [[HiWish program]]
File:ESP 055338 1865pedestal.jpg|Pedestal crater, as seen by HiRISE under HiWish program
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File:ESP 055338 1865pedestal.jpg|Pedestal crater
  
 
Image:Pedestal crater3.jpg|Pedestal craters form when the ejecta from impacts protect the underlying material from erosion.  As a result of this process, craters appear perched above their surroundings.
 
Image:Pedestal crater3.jpg|Pedestal craters form when the ejecta from impacts protect the underlying material from erosion.  As a result of this process, craters appear perched above their surroundings.
Image:Pedestaldrawingcolor2.jpg|Drawing shows a later idea of how some pedestal craters form.  In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further.  Heat and wind from the impact hardens the surface against erosion.  This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.
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Image:Tooting Crater.JPG|Wall of [[Tooting Crater]], as seen by HiRISE
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Image:Pettit Crater Rim.JPG|[[Pettit Crater]] rim, as seen by HiRISE
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[[File:Pedestaldrawingcolor2.jpg|600pxr|Drawing shows a later idea of how some pedestal craters form.  In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further.  Heat and wind from the impact hardens the surface against erosion.  This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.]]
Image:Nicholson Crater Mound.JPG|Nicholson mound with dark streaks, as seen by HiRISE
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Drawing shows a later idea of how some pedestal craters form. In this way of thinking, an impacting projectile goes into an ice-rich layer—but no further.  Heat and wind from the impact hardens the surface against erosion.  This hardening can be accomplished by the melting of ice which produces a salt/mineral solution thereby cementing the surface.
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Image:Pettit Crater Rim.JPG|Pettit Crater rim, as seen by HiRISE
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Image:Nicholson Crater Mound.JPG|Nicholson mound with dark streaks, as seen by HiRISE Nicholson Crater sits right on the equator.
 
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==Linear ridge networks==
 
==Linear ridge networks==
Linear ridge networks are found in various places on Mars in and around craters.<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>  Ridges often appear as mostly straight segments that intersect in a lattice-like manner.  They are hundreds of meters long, tens of meters high, and several meters wide.  There origin is not completely understood.  One idea for their origin is that impacts created fractures in the surface, these fractures later acted as channels for fluids.  Fluids turned into hard ridges.  With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind.  Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation.<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>Mustard et al., 2007.  Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 1. Ancient impact melt in the Isidis Basin and implications for the transition from the Noachian to Hesperian, J. Geophys. Res., 112.</ref> <ref>Mustard et al.,  2009.  Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis Basin, J. Geophys. Res., 114, doi:10.1029/2009JE003349.</ref>  Water here could have supported past life in these locations.  Clay may also preserve fossils or other traces of past life.
 
  
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[[File:ESP 036745 1905top.jpg|600pxr|Linear ridge networks]]
Image:26552sharpridges.jpg|Narrow ridges, as seen by HiRISE under HiWish program. The ridges may be the result of impacts fracturing the surface.
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ESP 036745 1905top.jpg|Linear ridge networks, as seen by HiRISE under HiWish program
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                                            Linear ridge networks
36745 1905lridgesshort.jpg|Close-up of ridge network, as seen by HiRISE under HiWish program This is an enlargement of a previous image.
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36745 1905ridgesx.jpg|Close-up of ridge network, as seen by HiRISE under HiWish program This is an enlargement of a previous image.
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Linear ridge networks are found in various places on Mars in and around craters.<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>  Ridges often appear as mostly straight segments that intersect in a lattice-like manner.  They are hundreds of meters long, tens of meters high, and several meters wide.  There origin is not completely understood.  One idea for their origin is that impacts created fractures in the surface, these fractures later acted as channels for fluids.  Fluids turned into hard ridges.  With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind.  Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation.<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>Mustard et al., 2007.  Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 1. Ancient impact melt in the Isidis Basin and implications for the transition from the Noachian to Hesperian, J. Geophys. Res., 112.</ref> <ref>Mustard et al.,  2009.  Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis Basin, J. Geophys. Res., 114, doi:10.1029/2009JE003349.</ref>  Water here could have supported past life.  Clay may also preserve fossils or other traces of past life.
ESP 036745 1905ridges.jpg|Linear ridge networks, as seen by HiRISE under HiWish program
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36745 1905layers.jpg|Close-up of layers and ridges, as seen by HiRISE under HiWish program
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<gallery class="center" widths="380px" heights="360px">
</gallery>
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Image:26552sharpridges.jpg|Narrow ridges  The ridges may be the result of impacts fracturing the surface.
  
<gallery class="center" widths="190px" heights="180px">
 
ESP 047611 1915polygons.jpg|Wide view of polygon ridges, as seen by HiRISE under HiWish program
 
  
47611 1915ridgesclose.jpg|Polygonal ridges, as seen by HiRISE under HiWish program
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36745 1905lridgesshort.jpg|Close-up of ridge network  This is an enlargement of a previous image.
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36745 1905ridgesx.jpg|Close-up of ridge network, as seen by HiRISE under [[HiWish program]] This is an enlargement of a previous image.
  
47611 1915ridgescloseshadows.jpg|Polygonal ridges, as seen by HiRISE under HiWish program
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</gallery>
  
47611 1915ridgesstreaks.jpg|Polygonal ridges, as seen by HiRISE under HiWish program
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<gallery class="center"  widths="380px" heights="360px">
  
47611 1915ridgessuperclose.jpg|Close view of polygonal ridges, as seen by HiRISE under HiWish program
 
  
 
ESP 047611 1915closecolor.jpg|Close, color view of polygonal ridges, as seen by HiRISE under HiWish program
 
ESP 047611 1915closecolor.jpg|Close, color view of polygonal ridges, as seen by HiRISE under HiWish program
 
</gallery>
 
</gallery>
  
<gallery class="center" widths="190px" heights="180px">
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<gallery class="center" widths="380px" heights="360px">
File:ESP 054850 1900ridges.jpg|Wide view of large ridge network,  as seen by HiRISE under HiWish program
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File:ESP 054850 1900ridges.jpg|Wide view of large ridge network
  
File:54850 1900ridges.jpg|Close view of ridge network, as seen by HiRISE under HiWish program Box shows size of football field.
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File:54850 1900ridges.jpg|Close view of ridge network  Box shows size of football field.
  
File:54850 1900ridgescontact.jpg|Close view of contact between ridge network and overlying layer,  as seen by HiRISE under HiWish program
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File:54850 1900ridgescontact.jpg|Close view of contact between ridge network and overlying layer
  
File:54850 1900ridgesclosecolor.jpg|Close, color view of ridges, as seen by HiRISE under HiWish program
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File:54850 1900ridgesclosecolor.jpg|Close, color view of ridges, as seen by HiRISE under [[HiWish program]]
  
 
</gallery>
 
</gallery>
  
 
==Dark Slope Streaks==
 
==Dark Slope Streaks==
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 +
[[File:ESP 043128 2005mesastreaks.jpg|600pxr|Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]]]
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                              Dark slope streaks on layered mesa, as seen by HiRISE under [[HiWish program]]
 +
 
Dark slope streaks are narrow, avalanche-like features common on dust-covered slopes in the equatorial regions.<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> They form in relatively steep sites, such as along escarpments and impact crater walls.<ref>Schorghofer, N.; Aharonson, O.; Khatiwala, S. (2002). Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126, </ref> Although first recognized in Viking Orbiter images from the late 1970s,<ref>Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. ''J. Geophys. Res.,'' '''87'''(B2), 1164–1178.</ref> <ref>Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in ''Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246,'' pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.</ref> dark slope streaks were not studied in detail until higher-resolution images from the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft became available in the late 1990s and 2000s.<ref>Sullivan, R. ''et al.'' (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. ''J. Geophys. Res.,'' '''106'''(E10), 23,607–23,633.</ref> <ref>Chuang, F.C. ''et al.''  2007.  HiRISE Observations of Slope Streaks on Mars. ''Geophys. Res. Lett.,'' '''34''' L20204, </ref>
 
Dark slope streaks are narrow, avalanche-like features common on dust-covered slopes in the equatorial regions.<ref>Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. ''Icarus,'' '''205''' 154–164.</ref> They form in relatively steep sites, such as along escarpments and impact crater walls.<ref>Schorghofer, N.; Aharonson, O.; Khatiwala, S. (2002). Slope Streaks on Mars: Correlations with Surface Properties and the Potential Role of Water. ''Geophys. Res. Lett.,'' '''29'''(23), 2126, </ref> Although first recognized in Viking Orbiter images from the late 1970s,<ref>Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. ''J. Geophys. Res.,'' '''87'''(B2), 1164–1178.</ref> <ref>Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in ''Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246,'' pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.</ref> dark slope streaks were not studied in detail until higher-resolution images from the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft became available in the late 1990s and 2000s.<ref>Sullivan, R. ''et al.'' (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. ''J. Geophys. Res.,'' '''106'''(E10), 23,607–23,633.</ref> <ref>Chuang, F.C. ''et al.''  2007.  HiRISE Observations of Slope Streaks on Mars. ''Geophys. Res. Lett.,'' '''34''' L20204, </ref>
  
 
The physical process that produces dark slope streaks is still uncertain. They are most likely caused by the mass movement of loose, fine-grained material on oversteepened slopes (i.e., dust avalanches).<ref>Sullivan, R.; Daubar, I.; Fenton, L.; Malin, M.; Veverka, J. (1999). Mass-Movement Considerations for Dark Slope Streaks Imaged by the Mars Orbiter Camera. 30th Lunar and Planetary Science Conference, Abstract #1809. http://www.lpi.usra.edu/meetings/LPSC99/pdf/1809.pdf.</ref><ref>Barlow, 2008, p. 141.</ref> The avalanching disturbs and removes a bright surface layer of dust to expose a darker substrate.<ref name=Ferris>Ferris, J. C.; Dohm, J.M.; Baker, V.R.; Maddock III, T. (2002). Dark Slope Streaks on Mars: Are Aqueous Processes Involved? ''Geophys. Res. Lett.,'' '''29'''(10), 1490, . http://www.agu.org/journals/ABS/2002/2002GL014936.shtml.</ref>
 
The physical process that produces dark slope streaks is still uncertain. They are most likely caused by the mass movement of loose, fine-grained material on oversteepened slopes (i.e., dust avalanches).<ref>Sullivan, R.; Daubar, I.; Fenton, L.; Malin, M.; Veverka, J. (1999). Mass-Movement Considerations for Dark Slope Streaks Imaged by the Mars Orbiter Camera. 30th Lunar and Planetary Science Conference, Abstract #1809. http://www.lpi.usra.edu/meetings/LPSC99/pdf/1809.pdf.</ref><ref>Barlow, 2008, p. 141.</ref> The avalanching disturbs and removes a bright surface layer of dust to expose a darker substrate.<ref name=Ferris>Ferris, J. C.; Dohm, J.M.; Baker, V.R.; Maddock III, T. (2002). Dark Slope Streaks on Mars: Are Aqueous Processes Involved? ''Geophys. Res. Lett.,'' '''29'''(10), 1490, . http://www.agu.org/journals/ABS/2002/2002GL014936.shtml.</ref>
  
<gallery class="center" widths="190px" heights="180px">
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<gallery class="center" widths="380px" heights="360px">
ESP 043128 2005mesastreaks.jpg|Dark slope streaks on layered mesa, as seen by HiRISE under HiWish program
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Esp 036851 1995mesastreaks.jpg|Dark slope streaks on mesa, as seen by HiRISE under HiWish program Location is Amazonis quadrangle.
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Esp 036851 1995mesastreaks.jpg|Dark slope streaks on mesa
ESP 036956 1895layers.jpg|Layers in Gordii Dorsum Region, as seen by HiRISE under HiWish program. Dark lines are [[Dark Slope Streaks]].
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ESP 036956 1895layers.jpg|Layers in Gordii Dorsum Region  Dark lines are Dark Slope Streaks.
 
</gallery>
 
</gallery>
  
Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. The team of scientists was led by Kaylan Burleigh, an undergraduate at the University of Arizona.  After counting some 65,000 dark streaks around the impact site of a group of 5 new craters, the team of scientists saw patterns.  The number of streaks was greatest closer to the impact site.  So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site.  The curved wings resembled curved knives, called scimitars.  This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the streaks.  At first it was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes.
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Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. The team, who did the study, was led by Kaylan Burleigh, an undergraduate at the University of Arizona.  After counting some 65,000 dark streaks around the impact site of a group of 5 new craters, the team of scientists saw patterns.  The number of streaks was greatest closer to the impact site.  So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site.  The curved wings resembled curved knives, called scimitars.  This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the streaks.  At first it was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes.
 
The crater cluster lies near the equator 510 miles south of Olympus Mons, on a type of terrain called the Medusae Fossae formation.  The formation is coated with dust and contains wind-carved ridges called yardangs.  Yardangs have steep slopes thickly covered with dust, so when the sonic boom of the airblast arrived from the impacts dust started to move down slopes.
 
The crater cluster lies near the equator 510 miles south of Olympus Mons, on a type of terrain called the Medusae Fossae formation.  The formation is coated with dust and contains wind-carved ridges called yardangs.  Yardangs have steep slopes thickly covered with dust, so when the sonic boom of the airblast arrived from the impacts dust started to move down slopes.
 
Using photos from Mars Global Surveyor and HiRISE camera on NASA's Mars Reconnaissance Orbiter, scientists have found about 20 new impacts each year on Mars.  Because the spacecraft have been imaging Mars almost continuously for a span of 14 years, newer images with suspected recent craters can be compared to older images to determine when the craters were formed.  Since the craters were spotted in a HiRISE image from February 2006, but were not present in a Mars Global Surveyor image taken in May 2004, the impact occurred in that time frame.
 
Using photos from Mars Global Surveyor and HiRISE camera on NASA's Mars Reconnaissance Orbiter, scientists have found about 20 new impacts each year on Mars.  Because the spacecraft have been imaging Mars almost continuously for a span of 14 years, newer images with suspected recent craters can be compared to older images to determine when the craters were formed.  Since the craters were spotted in a HiRISE image from February 2006, but were not present in a Mars Global Surveyor image taken in May 2004, the impact occurred in that time frame.
Line 138: Line 165:
 
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>
 
<ref>http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html</ref>
  
<gallery class="center" widths="190px" heights="180px">
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<gallery class="center" widths="380px" heights="360px">
 
Image:2764streaks.jpg|Image indicates crater cluster and curved lines formed by airblast from meteorites.  Meteorites caused airblast which caused dust avalanches on steep slopes.  Image is from HiRISE.
 
Image:2764streaks.jpg|Image indicates crater cluster and curved lines formed by airblast from meteorites.  Meteorites caused airblast which caused dust avalanches on steep slopes.  Image is from HiRISE.
ESP 046583 1960mesa.jpg|Mesa with dark slope streaks, as seen by HiRISE under HiWish program
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Image:2764streaksclose.jpg|Close up of previous image along light/dark boundary.  Dark line in middle of image shows border between light and dark area of curved lines.  Green arrows show high areas of ridges.  Loose dust moved down steep slopes when it felt the airblast from meteorite strikes.  Image is from HiRISE.
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</gallery>
 
</gallery>
  
 
==Streamlined shapes==
 
==Streamlined shapes==
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[[File:ESP 035480 2015streamlined.jpg|600pxr|Streamlined shape showing layers, as seen by HiRISE under [[HiWish program]]]]
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                            Streamlined shape showing layers, as seen by HiRISE under [[HiWish program]]
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When a fluid moves by a feature like a mound, it will become streamlined.  Often flowing water makes the shape and later lava flows spread over the region.  In the pictures below this has occurred.
 
When a fluid moves by a feature like a mound, it will become streamlined.  Often flowing water makes the shape and later lava flows spread over the region.  In the pictures below this has occurred.
  
<gallery class="center" widths="190px" heights="180px">
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<gallery class="center" widths="380px" heights="360px">
ESP 045133 1970lava.jpg|Wide view of streamlined shape and rafts of lava, as seen by HiRISE under HiWish program
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45133 1970lavascalebottom.jpg|Closer view of previous image, showing layers, as seen by HiRISE under HiWish program
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45133 1970lavascalebottom.jpg|Streamlined island showing layers
45133 1970lvarafts.jpg|Close view of lava rafts from previous images, as seen by HiRISE under HiWish program
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45133 1970lvarafts.jpg|Close view of lava rafts from previous images
Image:Marte Vallis Island.JPG|Streamlined Island in [[Marte Vallis]], as seen by HiRISE.  Click on image for good view of [[Dark Slope Streaks]].  Island is just to the west of [[Pettit Crater]].  Scale bar is 500 meters long.
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Image:Marte Vallis Island.JPG|Streamlined Island in Marte Vallis, as seen by HiRISE.  Island is just to the west of Pettit Crater.  Scale bar is 500 meters long.
Image:ESP 035480 2015streamlined.jpg|Streamlined shape showing layers, as seen by HiRISE under HiWish program
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ESP 045845 2000layers.jpg|Streamlined shapes and layers, as seen by HiRISE under HiWish program
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ESP 046478 1975streamlined.jpg|Streamlined feature
ESP 045898 1885streamlined.jpg|Streamlined shapes and layers, as seen by HiRISE under HiWish program
 
ESP 045911 1995streamlined.jpg|Streamlined shapes, as seen by HiRISE under HiWish program
 
ESP 046188 1855streaks.jpg|Dark slope streaks, as seen by HiRISE under HiWish program
 
ESP 046478 1975streamlined.jpg|Streamlined feature, as seen by HiRISE under HiWish program
 
 
</gallery>
 
</gallery>
  
 
==Layers==
 
==Layers==
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Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways.  Volcanoes, wind, or water can produce layers.<ref>http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE &#124; High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |</ref>
 
Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways.  Volcanoes, wind, or water can produce layers.<ref>http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE &#124; High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |</ref>
 
A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.<ref>Grotzinger, J. and R. Milliken (eds.).  2012.  Sedimentary Geology of Mars.  SEPM.</ref>
 
A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.<ref>Grotzinger, J. and R. Milliken (eds.).  2012.  Sedimentary Geology of Mars.  SEPM.</ref>
Sometimes the layers are of different colors.  Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.  The Mars Rover Opportunity examined such layers close-up with several instruments.  Some layers are made up of fine particles because they seem to break up into find dust.  Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders.  Basalt has been identified on Mars in many places.  Instruments on orbiting spacecraft have detected clay (also called [[phyllosilicate]]) in some layers.  Finding clay is important because it has to have water to form.  Evidence of past life may be found in clay deposits.
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Sometimes the layers are of different colors.  Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.  The Mars Rover Opportunity examined such layers close-up with several instruments.  Some layers are made up of fine particles because they seem to break up into find dust.  Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders.  Basalt has been identified on Mars in many places.  Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers.  Finding clay is important because it has to have water to form.  Evidence of past life may be found in clay deposits.
 
A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.<ref>Grotzinger, J. and R. Milliken (eds.).  2012.  Sedimentary Geology of Mars.  SEPM.</ref>
 
A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.<ref>Grotzinger, J. and R. Milliken (eds.).  2012.  Sedimentary Geology of Mars.  SEPM.</ref>
 
Layers can be hardened by the action of groundwater.  Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through.  When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together.
 
Layers can be hardened by the action of groundwater.  Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through.  When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together.
<gallery class="center" widths="190px" heights="180px">
 
ESP 047137 2075layers.jpg|Wide view of layers, as seen by HiRISE under HiWish program.
 
47137 2075layersclose.jpg|Close view of layers, as seen by HiRISE under HiWish program.
 
ESP 045198 1900craterlayers.jpg|Wide view of scarp showing layers, as seen by HiRISE under HiWish program
 
45198 1900craterlayersclose.jpg|Close view of layers from previous image,  as seen by HiRISE under HiWish program
 
ESP 045435 2055troughlayers.jpg|Layers in trough and dark slope streaks,  as seen by HiRISE under HiWish program
 
ESP 047678 1860layers.jpg|Wide view of layers, as seen by HiRISE under HiWish program
 
  
52372 1815layersclose.jpg|Layers and [[dark slope streak]]s,  as seen by HiRISE under HiWish program
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<gallery class="center"  widths="380px" heights="360px">
File:ESP 053795 1905layers.jpg|Layered mesas, as seen by HiRISE under HiWish program
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ESP 047137 2075layers.jpg|Wide view of layers
File:ESP 053861 1920ridges.jpg|Wide view of ridges and layers, as seen by HiRISE under HiWish program
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47137 2075layersclose.jpg|Close view of layers, as seen by HiRISE under [[HiWish program]].
File:53861 1920layers.jpg|Close view of layers,  as seen by HiRISE under HiWish program
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ESP 045198 1900craterlayers.jpg|Wide view of scarp showing layers
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ESP 045435 2055troughlayers.jpg|Layers in trough and dark slope streaks
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File:ESP 053795 1905layers.jpg|Layered mesas
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</gallery>
 
</gallery>
  
 
==Dust devils==
 
==Dust devils==
Dust devil tracks can be very pretty.  They are caused by giant dust devils removing bright colored dust from the Martian surface; thereby exposing a dark layer.  Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit]. Marsrovers.jpl.nasa.gov. Retrieved on 7 August 2011.</ref> The pattern of  tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>  A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 m and last at least 26 minutes.<ref>Reiss, D. et al.  2011.  Multitemporal observations of identical active dust devils on Mars with High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC).  Icarus.  215:358-369.</ref>
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<gallery class="center" widths="190px" heights="180px">
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Dust devils can create very pretty tracksGiant Martian dust devils remove bright colored dust from the Martian surface; thereby exposing a dark layer. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface creating tracks. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will be enough.    The width of a single human hair ranges from approximately 20 to 200 microns (μm); consequently, the dust that can cover dust devil tracks may only be the thickness of a human hair.<ref>https://en.wikipedia.org/wiki/Micrometre</ref> Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.<ref>http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov. Retrieved on 7 August 2011.</ref> The pattern of  tracks has been shown to change every few months.<ref>http://hirise.lpl.arizona.edu/PSP_005383_1255</ref>  A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 m and last at least 26 minutes.<ref>Reiss, D. et al.  2011.  Multitemporal observations of identical active dust devils on Mars with High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC).  Icarus.  215:358-369.</ref>
Image:MarsDustDevi-AmazonisPlanitia-MGS-MOC-20010401-E03-00938.gif|[[Dust devil tracks|Martian Dust Devil]] - in [[Amazonis Planitia]] (April 10, 2001) ([http://www.nasa.gov/mission_pages/MRO/multimedia/pia15116.html also]) ([https://www.youtube.com/watch?v=0t0LWFHB8Qo video (02:19)]).
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<gallery class="center" widths="380px" heights="360px">
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Image:Mars-DustDevil-20170215.jpg|A dust devil on hilly terrain in the Amazonis region.
 
Image:Mars-DustDevil-20170215.jpg|A dust devil on hilly terrain in the Amazonis region.
 
</gallery>
 
</gallery>
  
 
==More images from Amazonis quadrangle==
 
==More images from Amazonis quadrangle==
<gallery class="center" widths="190px" heights="180px">
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Image:Map of Amazonis.JPG|Map of Amazonis quadrangle.
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<gallery class="center" widths="380px" heights="360px">
Image:23664medussa.jpg|Yardangs in the Medusae Fossae formation, as seen by HiRISE under [[HiWish program]].
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Image:Map of Amazonis.JPG|Map of Amazonis quadrangle. Green rectangles are places that were imaged by the high resolution camera on the mars Global SurveyorNotice Nicholson crater at the bottom--it sits right at the equator.
Image:Tartarus Colles Channel.JPG|[[Tartarus Colles]] channel, as seen by HiRISEScale bar is 500 meters. Click on image to see bridge across channel.
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Image:Olympus Mons Scarp.JPG|Olympus Mons scarp, as seen by HiRISE. Scale bar is 500 meters long.
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Image:Channels From Fissure.JPG|Channels From Fissure, as seen by HiRISE. The fissure probably started the water flowing to make the channel.   
Image:Channels From Fissure.JPG|Channels From Fissure, as seen by HiRISE. The fissure probably started the water flowing to make the channel.  The channels look somewhat better in the enlarged view of the original image.
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Image:ESP_024997ridges.jpg|Possible inverted stream channels in [[Phlegra Dorsa]] region, as seen by HiRISE under [[HiWish program]]. The ridges were probably once stream valleys that have become full of sediment and cemented.  So, they became hardened against erosion which removed surrounding material.
 
Image:26552surfaces.jpg|Surfaces in Amazonis quadrangle, as seen by HiRISE under HiWish program.
 
 
</gallery>
 
</gallery>
  
<gallery class="center" widths="190px" heights="180px">
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[[File:ESP_024997ridges.jpg|600pxr|Possible inverted stream channels in Phlegra Dorsa region, as seen by HiRISE under [[HiWish program]]. The ridges were probably once stream valleys that have become full of sediment and cemented.  So, they became hardened against erosion which removed surrounding material.
ESP 048640 2100lavasurface.jpg|Lava flows affected by obstacles, as seen by HiRISE under HiWish program Arrows show two obstacles that are changing the flow.
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]]
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Possible inverted stream channels in Phlegra Dorsa region, as seen by HiRISE under [[HiWish program]]. The ridges were probably once stream valleys that have become full of sediment and cemented.  So, they became hardened against erosion which removed surrounding material.
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<gallery class="center" widths="380px" heights="360px">
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ESP 048640 2100lavasurface.jpg|Lava flows affected by obstacles, as seen by HiRISE under [[HiWish program]] Arrows show two obstacles that are changing the flow.
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48640 2100lavasurfacescaled.jpg|View of a lava lobe The box shows the size of a football field.
  
48640 2100lavasurfacescaled.jpg|View of a lava lobe, as seen by HiRISE under HiWish program The box shows the size of a football field.
 
48640 2100lavasurfacescaledclose.jpg|Close view of a lava lobe, as seen by HiRISE under HiWish program The box shows the size of a football field.
 
 
</gallery>
 
</gallery>
  
  
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[[File:48640 2100lavasurfacescaledclose.jpg|600pxr|Close view of a lava lobe The box shows the size of a football field.]]
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                    Close view of a lava lobe The box shows the size of a football field.
  
 
==See also==
 
==See also==
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==External links==
 
==External links==
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*[https://www.uahirise.org/PSP_005383_1255 Changes in dust devil tracks]
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*[https://static.uahirise.org/images/2020/details/cut/ESP_063204_1800.gif Looking for Slope Streaks-old and new pictures of streaks]
  
  
 
[[Category:Mars Atlas]]
 
[[Category:Mars Atlas]]

Revision as of 10:07, 27 March 2020

Mars topography (MOLA dataset) HiRes (1).jpg
MC-08 Amazonis 0–30° N 135–180° W Quadrangles Atlas

This area is considered to be among the youngest parts of Mars because it has a very low density of craters. The Amazonia period is named after this area. This quadrangle contains special, unusual features called Sulci and the Medusae Fossae Formation. As per the rest of Mars, this region contains some very beautiful landscapes. The Amazonis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) . The Amazonis quadrangle is also referred to as MC-8 (Mars Chart-8).[1] The quadrangle covers the area from 0° to 30° north latitude and 135° to 180° west longitude (225-180 E ). The Amazonis quadrangle contains the classic region called Amazonis Planitia.


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

Name

Its name derives from the mythical land of the Amazons. In Greek mythology, the Amazons were a tribe of warrior women believed to live in Asia Minor. In this myth, Amazons were the daughters of Ares and Harmonia (mythology) (a nymph of the Akmonian Wood). They were brutal and aggressive--their main concern in life was war.[2] [3]

Medusae Fossae Formation

The Amazonis quadrangle is of great interest to scientists because it contains a major part of a formation, called the Medusae Fossae Formation. This unit is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. The surface of the formation has been eroded by the wind into a series of linear ridges called yardangs. These ridges generally point in direction of the prevailing winds that carved them and demonstrate the erosive power of Martian winds. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles,[4] and was most likely formed by the deposition of wind-blown dust or volcanic ash. Using a global climate model, a group of researchers concluded that the Medusae Fossae Formation could have easily been formed from ash from the volcanoes Apollinaris Mons, Arsia Mons, and possibly from Pavonis Mons.[5] Another evidence for a fine-grained composition is that the area gives almost no radar return. For this reason it has been called a "stealth" region.[6] Layers are seen in parts of the formation. Images from spacecraft show that they have different degrees of hardness probably because of significant variations in the physical properties, composition, particle size, and/or cementation. Very few impact craters are visible throughout the area so the surface is relatively young.[7] Researchers found that nearly all the dust that falls out of the atmosphere and that coats everything on Mars has its origin in the Medusae Fossae formation.[8] It turns out that the chemical elements (sulfur and chlorine) in this formation, in the atmosphere, and covering the surface are the same. The amount of dust on Mars is sufficient to form a 2 to 12 meters thick layer over the entire planet.[9] [10] Since there are relatively few depositional features in the Medusae Fossae Formation, most of the materials being eroded are probably small enough to be suspended in the atmosphere and transported long distances.[11]

An analysis of data from the 2001 Mars Odyssey Neutron Spectrometer revealed that portions of the Medusae Fossae Formation contain water.[12]

Sulci

A very rugged terrain extends from the base of Olympus Mons, the largest volcano on Mars. This terrain is called Lycus Sulci. Sulci is a Latin term for the furrows on the surface of a brain, so Lycus Sulci has many furrows or grooves. The furrows are huge—up to a full kilometer deep.[13] It would be extremely difficult to walk across it or to land a space ship there. A picture of this area is shown below.

Columnar Jointing

Columnar jointing in a crater in Marte Vallis

                       Columnar jointing in a crater in Marte Vallis


Lava flows sometimes cool to form large groups of more-or-less equally sized columns.[14] Since Mars is largely covered by lava flow, it was expected that these joints were on Mars. With the superior resolution of the HiRISE images, scientists finally found columnar jointing in various locations in 2009. Pictures below show examples of columnar jointing both on Mars and on the Earth. Many tourists travel to see these formations in our National Parks, like Yellowstone.

Craters

Craters give us insight into what lies under the ground. Since the collision that produces an impact crater is like a powerful explosion, rocks from deep underground are tossed onto the surface. Hence, by examining the material or ejecta thrown out by the impact, we can see what lies deep under the surface. Some craters, especially the more recent ones, will display layers on their walls. These layers can help us tell the kinds of rocks that were formed in the past. For example, layers that contain dark, blocky boulders likely originated as lava flows. As craters get larger (greater than 10 km in diameter) they usually have a central peak.[15] The peak is caused by a rebound of the crater floor following the impact.[16] Scientists are eager to examine those central peaks because they contain samples of rocks from deep underground. Instruments, called spectroscopes, can tell us the mineral composition of these rocks. We believe that pits in Tooting Crater are caused by hot ejecta falling on ground containing ice. The pits are formed by heat forming steam that rushes out from groups of pits simultaneously, thereby blowing away from the pit ejecta.[17] [18]

Based on study of years of HiRISE images, researchers believe over 200 new craters are formed each year on Mars, based on study of years of HiRISE images.[19][20]


- before/March 27 & after/March 28, 2012[21]

Pedestal Craters

A pedestal crater is an impact crater with its ejecta sitting on a raised platform above the surrounding terrain. They form when an impact crater ejects material which forms an erosion resistant layer, thus protecting the underlying materials from erosion. As a result of this hard covering, the crater and its ejecta become elevated, after erosion removes the softer material beyond the ejecta. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. Pedestal craters were first observed during the Mariner missions.[22] [23]

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

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


Linear ridge networks

Linear ridge networks

                                            Linear ridge networks

Linear ridge networks are found in various places on Mars in and around craters.[24] Ridges often appear as mostly straight segments that intersect in a lattice-like manner. They are hundreds of meters long, tens of meters high, and several meters wide. There origin is not completely understood. One idea for their origin is that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids turned into hard ridges. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind. Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation.[25] [26] [27] Water here could have supported past life. Clay may also preserve fossils or other traces of past life.

Dark Slope Streaks

Dark slope streaks on layered mesa, as seen by HiRISE under HiWish program

                             Dark slope streaks on layered mesa, as seen by HiRISE under HiWish program

Dark slope streaks are narrow, avalanche-like features common on dust-covered slopes in the equatorial regions.[28] They form in relatively steep sites, such as along escarpments and impact crater walls.[29] Although first recognized in Viking Orbiter images from the late 1970s,[30] [31] dark slope streaks were not studied in detail until higher-resolution images from the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft became available in the late 1990s and 2000s.[32] [33]

The physical process that produces dark slope streaks is still uncertain. They are most likely caused by the mass movement of loose, fine-grained material on oversteepened slopes (i.e., dust avalanches).[34][35] The avalanching disturbs and removes a bright surface layer of dust to expose a darker substrate.[36]

Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. The team, who did the study, was led by Kaylan Burleigh, an undergraduate at the University of Arizona. After counting some 65,000 dark streaks around the impact site of a group of 5 new craters, the team of scientists saw patterns. The number of streaks was greatest closer to the impact site. So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site. The curved wings resembled curved knives, called scimitars. This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the streaks. At first it was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes. The crater cluster lies near the equator 510 miles south of Olympus Mons, on a type of terrain called the Medusae Fossae formation. The formation is coated with dust and contains wind-carved ridges called yardangs. Yardangs have steep slopes thickly covered with dust, so when the sonic boom of the airblast arrived from the impacts dust started to move down slopes. Using photos from Mars Global Surveyor and HiRISE camera on NASA's Mars Reconnaissance Orbiter, scientists have found about 20 new impacts each year on Mars. Because the spacecraft have been imaging Mars almost continuously for a span of 14 years, newer images with suspected recent craters can be compared to older images to determine when the craters were formed. Since the craters were spotted in a HiRISE image from February 2006, but were not present in a Mars Global Surveyor image taken in May 2004, the impact occurred in that time frame. The largest crater in the cluster is about 22 meters (72 feet) in diameter--close to the area of a basketball court. As the meteorite traveled through the Martian atmosphere it probably broke up; hence a tight group of impact craters resulted. Dark slope streaks have been seen for some time, and many ideas have been advanced to explain them. This research may have finally solved this mystery.[37][38] [39]

Streamlined shapes

Streamlined shape showing layers, as seen by HiRISE under HiWish program

                           Streamlined shape showing layers, as seen by HiRISE under HiWish program


When a fluid moves by a feature like a mound, it will become streamlined. Often flowing water makes the shape and later lava flows spread over the region. In the pictures below this has occurred.

Layers

Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.[40] A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.[41] Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydrated minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Some layers are made up of fine particles because they seem to break up into find dust. Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders. Basalt has been identified on Mars in many places. Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers. Finding clay is important because it has to have water to form. Evidence of past life may be found in clay deposits. A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.[42] Layers can be hardened by the action of groundwater. Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through. When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together.

Dust devils

Dust devils can create very pretty tracks. Giant Martian dust devils remove bright colored dust from the Martian surface; thereby exposing a dark layer. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface creating tracks. It does not take too much fine dust to cover those tracks--experiments in Earth laboratories demonstrate that only a few 10's of microns of dust will be enough. The width of a single human hair ranges from approximately 20 to 200 microns (μm); consequently, the dust that can cover dust devil tracks may only be the thickness of a human hair.[43] Dust devils on Mars have been photographed both from the ground and high overhead from orbit. They have even blown dust off the solar panels of two Rovers on Mars, thereby greatly extending their useful lifetime.[44] The pattern of tracks has been shown to change every few months.[45] A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 m and last at least 26 minutes.[46]

More images from Amazonis quadrangle

Possible inverted stream channels in Phlegra Dorsa region, as seen by HiRISE under HiWish program. The ridges were probably once stream valleys that have become full of sediment and cemented. So, they became hardened against erosion which removed surrounding material.

Possible inverted stream channels in Phlegra Dorsa region, as seen by HiRISE under HiWish program. The ridges were probably once stream valleys that have become full of sediment and cemented. So, they became hardened against erosion which removed surrounding material.



Close view of a lava lobe The box shows the size of a football field.

                   Close view of a lava lobe The box shows the size of a football field.

See also

References

  1. Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. Mars. University of Arizona Press: Tucson, 1992.
  2. https://www.theoi.com/Olympios/AresFamily.html#Amazones Apollonius Rhodius, Argonautica (Book 2, ln. 989)]
  3. http://sacred-texts.com/cla/argo/argo23.htm ARGONAUTICA, BOOK 2
  4. Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM
  5. Kerber L., et al. 2012. The disporsal of pyroclasts from ancient explosive volcanoes on Mars: Implications for the friable layered deposits. Icarus. 219:358-381.
  6. ISBN 978-0-521-85226-5
  7. http://themis.asu.edu/zoom-20020416a
  8. http://redplanet.asu.edu/?tag=medusae-fossae-formation
  9. https://www.sciencedaily.com/releases/2018/07/180724120854.htm
  10. Lujendra Ojha, Kevin Lewis, Suniti Karunatillake, Mariek Schmidt. The Medusae Fossae Formation as the single largest source of dust on Mars. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-05291-5
  11. Tanaka, K. L. Dust and ice deposition in the Martian geologic record. Icarus 144, 254–266 (2000).
  12. Wilson, J. et al. 2018. Equatorial locations of water on Mars: Improved resolution maps based on Mars Odyssey Neutron Spectrometer data. Icarus: 299, 148-160.
  13. http://themis.asu.edu/zoom-20030606a
  14. http://volcano.oregonstate.edu/columnar-jointing
  15. http://www.lpi.usra.edu/publications/slidesets/stones/
  16. {{cite book|author=Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ%7Caccessdate=7 March 2011|date=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7
  17. Boyce, J. et al. 2012. Origin of small pits in martian impact craters. Icarus. 221: 262-275.
  18. Tornabene, L. et al. 2012. Widespread crater-related pitted materials on Mars. Further evidence for the role of target volatiles during the impact process. Icarus. 220: 348-368.
  19. http://www.space.com/21198-mars-asteroid-strikes-common.html | title=Pow! Mars Hit by Space Rocks 200 Times a Year
  20. http://www.universetoday.com/109020/brand-new-impact-crater-shows-up-on-mars/ |title = Brand New Impact Crater Shows up on Mars|
  21. Webster |first=Guy |last2=Brown |first2=Dwayne |title=NASA Mars Weathercam Helps Find Big New Crater |url=http://www.jpl.nasa.gov/news/news.php?release=2014-162 |date=22 May 2014 |work=NASA
  22. Bleacher, J. and S. Sakimoto. Pedestal Craters, A Tool For Interpreting Geological Histories and Estimating Erosion Rates. LPSC
  23. http://themis.asu.edu/feature/8
  24. 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.
  25. 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.
  26. Mustard et al., 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 1. Ancient impact melt in the Isidis Basin and implications for the transition from the Noachian to Hesperian, J. Geophys. Res., 112.
  27. Mustard et al., 2009. Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis Basin, J. Geophys. Res., 114, doi:10.1029/2009JE003349.
  28. Chuang, F.C.; Beyer, R.A.; Bridges, N.T. (2010). Modification of Martian Slope Streaks by Eolian Processes. Icarus, 205 154–164.
  29. 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,
  30. Morris, E.C. (1982). Aureole Deposits of the Martian Volcano Olympus Mons. J. Geophys. Res., 87(B2), 1164–1178.
  31. Ferguson,H.M.; Lucchitta, B.K. (1984). Dark Streaks on Talus Slopes, Mars in Reports of the Planetary Geology Program 1983, NASA Tech. Memo., TM-86246, pp. 188–190. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840015363_1984015363.pdf.
  32. Sullivan, R. et al. (2001). Mass Movement Slope Streaks Imaged by the Mars Orbiter Camera. J. Geophys. Res., 106(E10), 23,607–23,633.
  33. Chuang, F.C. et al. 2007. HiRISE Observations of Slope Streaks on Mars. Geophys. Res. Lett., 34 L20204,
  34. Sullivan, R.; Daubar, I.; Fenton, L.; Malin, M.; Veverka, J. (1999). Mass-Movement Considerations for Dark Slope Streaks Imaged by the Mars Orbiter Camera. 30th Lunar and Planetary Science Conference, Abstract #1809. http://www.lpi.usra.edu/meetings/LPSC99/pdf/1809.pdf.
  35. Barlow, 2008, p. 141.
  36. Ferris, J. C.; Dohm, J.M.; Baker, V.R.; Maddock III, T. (2002). Dark Slope Streaks on Mars: Are Aqueous Processes Involved? Geophys. Res. Lett., 29(10), 1490, . http://www.agu.org/journals/ABS/2002/2002GL014936.shtml.
  37. Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars" Icarus 2012; 217 (1) 194
  38. http://redplanet.asu.edu/
  39. http://phys.org/news/2011-12-meteorite-shockwaves-trigger-avalanches-mars.html
  40. http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |
  41. Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.
  42. Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.
  43. https://en.wikipedia.org/wiki/Micrometre
  44. http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html Mars Exploration Rover Mission: Press Release Images: Spirit. Marsrovers.jpl.nasa.gov. Retrieved on 7 August 2011.
  45. http://hirise.lpl.arizona.edu/PSP_005383_1255
  46. Reiss, D. et al. 2011. Multitemporal observations of identical active dust devils on Mars with High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC). Icarus. 215:358-369.

External links