Arcadia quadrangle

Arcadia is the name of a telescopic albedo feature located at 45° north latitude (N) and 260° east longitude (E) on Mars. The feature was named after a mountainous region in southern Greece.Blunck, J. 1982. Mars and its Satellites. Exposition Press. Smithtown, N.Y. The name was approved by the International Astronomical Union (IAU) in 1958.USGS Gazetteer of Planetary Nomenclature. Mars. http://planetarynames.wr.usgs.gov/.

The quadrangle contains Alba Patera, the largest volcano (by area and volume) in the Solar System, Mareotis Fossae and Tempe as well as Tempe Terra, a highly fractured block of ancient crust about the size of Alaska.

Large troughs (long narrow depressions) are called fossae in the geographical language used for Mars. This term is derived from a Latin 1st declension noun; therefore fossa is singular and fossae is plural.{{Cite web | url=http://www.marsartgallery.com/marsnames.html |title = Mars Art Gallery Martian Feature Name Nomenclature}} These troughs form when the crust is stretched until it breaks. The stretching can be due to the large weight of a nearby volcano. Fossae/pit craters are common near volcanoes in the Tharsis and Elysium system of volcanoes.Skinner, J., L. Skinner, and J. Kargel. 2007. Re-assessment of Hydrovolcanism-based Resurfacing within the Galaxias Fossae Region of Mars. Lunar and Planetary Science XXXVIII (2007) A trough often has two breaks with a middle section moving down, leaving steep cliffs along the sides; such a trough is called a graben.{{Cite web | url=http://hirise.lpl.arizona.edu/PSP_008641_2105 | title=HiRISE | Craters and Pit Crater Chains in Chryse Planitia (PSP_008641_2105)}} Lake George, in northern New York State, is a lake that sits in a graben. Pit craters are often associated with graben. Pit craters do not have rims or ejecta around them, like impact craters do. Studies have found that on Mars a fault may be as deep as 5 km, that is the break in the rock goes down to 5 km. Moreover, the crack or fault sometimes widens or dilates. This widening causes a void to form with a relatively high volume. When surface material slides into the void, a pit crater or a pit crater chain forms. On Mars, individual pit craters can join to form chains or even to form troughs that are sometimes scalloped.Wyrick, D., D. Ferrill, D. Sims, and S. Colton. 2003. Distribution, Morphology and Structural Associations of Martian Pit Crater Chains. Lunar and Planetary Science XXXIV (2003) Other ideas have been suggested for the formation of fossae and pit craters. There is evidence that they are associated with dikes of magma. Magma might move along, under the surface, breaking the rock and more importantly melting ice. The resulting action would cause a crack to form at the surface. Pit craters are not common on Earth. Sinkholes, where the ground falls into a hole (sometimes in the middle of a town) resemble pit craters on Mars. On Earth these holes are caused by limestone being dissolved, thereby causing a void.http://www.swri.edu/4org/d20/DEMPS/planetgeo/planetmars.html{{dead link|date=July 2017 |bot=InternetArchiveBot |fix-attempted=yes }}{{Cite web | url=http://www.msss.com/mars_images/moc/2004/01/29/index.html | title=Mars Global Surveyor MOC2-620 Release}}

Knowledge of the locations and formation mechanisms of pit craters and fossae is important for the future colonization of Mars because they may be reservoirs of water.Ferrill, D., D. Wyrick, A. Morris, D. Sims, and N. Franklin. 2004. Dilational fault slip and pit chain formation on Mars 14:10:4-12 Many grabens are found in the Arcadia quadrangle. Pictures below show examples of grabens in Arcadia.

Alba Patera.JPG|Graben near Alba Patera, as seen by THEMIS. Graben and catenae, collapse features, both caused by faults. When the crust is stretched, faults form and material falls into voids created by the stretching. Uranius Tholus (upper) and Ceraunius Tholus (largest) volcanoes are visible in wide context view, below and to the right of Alba Patera.

Cross cutting grabens in Arcadia.JPG|Forces from different directions caused this complex of grabens to form. Picture taken by THEMIS.

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

File:ESP 053754 2125lineofpits.jpg|Line of pits, as seen by HiRISE under HiWish program. Fossae often seem to start with a line of pits.

File:ESP 053805 2140troughs.jpg|Troughs (fossae), as seen by HiRISE under HiWish program

File:ESP 055521 2105troughscrater.jpg|Troughs (Fossae), as seen by HiRISE under HiWish program. Trough seems to have cut away part of a crater.

File:ESP 055310 2165troughschannels.jpg|Channels coming from a trough, as seen by HiRISE under HiWish program

File:Wide view of troughs and streaks and tars 82845 2125.jpg|Troughs with dark slope streaks on the wall and transverse aeolian ridges on the floor. The colored strip in the center is about 1 km across.

Many areas on Mars, including the Arcadia quadrangle, experience the passage of giant dust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil passes it blows away the coating and exposes the underlying dark surface. Dust devils have been seen from the ground and from orbit. They have blown dust from the solar panels of the two Rovers on Mars, thereby greatly extending their lives.{{Cite web | url=http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html | title=Mars Exploration Rover}} The twin Rovers were designed to last for three months, instead they lasted more than six years. The first rover, Spirit, was last heard from in March 2010. Opportunity continued to explore Mars for over 14 years, and its mission was ended in August, 2018. The pattern of the tracks were shown to change every few months.{{cite web|url=http://mars.jpl.nasa.gov/spotlight/KenEdgett.html |title=Mars Exploration: Features |access-date=2012-01-19 |url-status=dead |archive-url=https://web.archive.org/web/20111028015730/http://mars.jpl.nasa.gov/spotlight/kenEdgett.html |archive-date=2011-10-28 }}

Many places on Mars show dark streaks on steep slopes like crater walls. It seems that the youngest streaks are dark; then they become lighter with age. Often they begin as a small narrow spot then widen and extend downhill for hundreds of meters. They have been seen to travel around obstacles, like boulders.http://www.space.com/image_of_day_080730.html{{dead link|date=October 2016 |bot=InternetArchiveBot |fix-attempted=yes }}

Several ideas have been advanced to explain the streaks. Some involve water or even the growth of organisms.{{cite web|url=http://www.spcae.com/scienceastronomy/streaks_mars_021211.html |title=Archived copy |access-date=2011-03-28 |url-status=dead |archive-url=https://web.archive.org/web/20150221231430/http://www.spcae.com/scienceastronomy/streaks_mars_021211.html |archive-date=2015-02-21 }}http://www.space.com/scienceastronomy/streaks_mars_streaks_030328.html{{dead link|date=October 2016 |bot=InternetArchiveBot |fix-attempted=yes }}http://www.space.com/scienceastronomy/mars_{{dead link|date=October 2016 |bot=InternetArchiveBot |fix-attempted=yes }}http://www.space.com/scienceastronomy/streaks_mars_021200.html {{Dead link|date=February 2022}} It is most generally accepted that they represent avalanches of dust. The streaks appear in areas covered with dust. When a thin layer of dust is removed, the underlying surface is dark. Much of the Martian surface is covered with dust. Fine dust settles out of the atmosphere covering everything. Much is known about this dust because the solar panels of the Mars rovers get covered with dust, thus reducing the electrical energy. The power of the rovers has been restored many times by the wind, in the form of dust devils, cleaning the panels and boosting the power.{{cite web|url=https://www.sciencedaily.com/releases/2009/02/090217101110.htm|access-date=2017-06-01|date=2009-02-19|title=Mars Spirit Rover Gets Energy Boost From Cleaner Solar Panels|work=Science Daily}}

Dust storms are frequent, especially when the spring season begins in the southern hemisphere. At that time, Mars is 40% closer to the Sun. The orbit of Mars is much more elliptical than Earth's. The difference between the farthest point from the Sun and the closest point to the Sun is very great for Mars, but only a slight amount for Earth. Also, every few years, the entire planet is engulfed in a global dust storm. When NASA's Mariner 9 craft arrived, nothing could be seen through the dust storm.{{Cite book |isbn = 0-517-00192-6|title = Atlas of the Solar System|last1 = Moore|first1 = Patrick|date = 1990-06-02| publisher=Crescent Books }}{{cite book|author=Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|access-date=7 March 2011|year=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7}}{{page needed|date=June 2017}} Other global dust storms have also been observed since then.

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, patterns emerged. 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 scimitars, curved knives. This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the many dark 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.{{cite journal | last1 = Burleigh | first1 = Kaylan J. | last2 = Melosh | first2 = Henry J. | last3 = Tornabene | first3 = Livio L. | last4 = Ivanov | first4 = Boris | last5 = McEwen | first5 = Alfred S. | last6 = Daubar | first6 = Ingrid J. | year = 2012 | title = Impact air blast triggers dust avalanches on Mars | journal = Icarus | volume = 217 | issue = 1| page = 194 | doi = 10.1016/j.icarus.2011.10.026 | bibcode=2012Icar..217..194B}}{{Cite web | url=http://redplanet.asu.edu/ |title = Red Planet Report | What's new with Mars}} Dark streaks can be seen in the image below of Tractus Catena that was taken by HiRISE.

52593 2140streaks.jpg|Dark slope streaks, as seen by HiRISE under HiWish program

File:82845 2125 dark slope streaks.jpg|Wide view of dark slope streaks on wall of trough.

File:Close view of dark slope streaks 82845 2125.jpg|Close view of dark slope streaks on wall of trough as seen by HiRISE under HiWish program. The image is about 1 km across.

{{main|Martian Gullies}}

The Arcadia quadrangle is the location of gullies that may be due to recent flowing water. Gullies occur on steep slopes, especially on the walls of craters. Gullies are believed to be relatively young because they have few, if any craters. Moreover, they lie on top of sand dunes which themselves are considered to be quite young. Usually, each gully has an alcove, channel, and apron. Some studies have found that gullies occur on slopes that face all directions,{{cite journal | last1=Edgett |first1= K. |year= 2003 |title= Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit |journal= Lunar Planet. Sci. |volume=34 |at=Abstract 1038 | url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1038.pdf | bibcode = 2003LPI....34.1038E |display-authors=etal}} others have found that the greater number of gullies are found on poleward facing slopes, especially from 30 to 44 S.{{cite journal | last1 = Dickson | first1 = J | last2 = Head | first2 = J | last3 = Kreslavsky | first3 = M | title = Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography | doi = 10.1016/j.icarus.2006.11.020 | url = http://www.planetary.brown.edu/pdfs/3138.pdf | year = 2007 | pages = 315–323 | volume = 188 | issue = 2 | journal = Icarus | bibcode = 2007Icar..188..315D | access-date = 2012-03-13 | archive-date = 2017-07-06 | archive-url = https://web.archive.org/web/20170706040142/http://planetary.brown.edu/pdfs/3138.pdf | url-status = dead }}

Although many ideas have been put forward to explain them,{{Cite web|url=http://www.psrd.hawaii.edu/Aug03/MartianGullies.html|title = PSRD: Gullied Slopes on Mars}} the most popular involve liquid water coming from an aquifer, from melting at the base of old glaciers, or from the melting of ice in the ground when the climate was warmer.{{cite journal | last1= Heldmann | first1= J | title= Observations of martian gullies and constraints on potential formation mechanisms | journal= Icarus | volume= 168 | issue= 2 | pages= 285–304 | year = 2004 | doi = 10.1016/j.icarus.2003.11.024 | bibcode=2004Icar..168..285H| url= https://zenodo.org/record/1259029 }}Forget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK. Because liquid water mayu have been involved in their formation, and that they could be very young, some scientists look to the gullies to search for signs of past life.

There is evidence for all three theories. Most of the gully alcove heads occur at the same level, just as one would expect of an aquifer. Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin. One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. Aquifers are layer that allow water to flow. They may consist of porous sandstone. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies.{{Cite web | url=http://www.space.com/scienceastronomy/mars_aquifer_041112.html |title = Mars Gullies Likely Formed by Underground Aquifers|website = Space.com|date = 12 November 2004}} Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.Harris, A and E. Tuttle. 1990. Geology of National Parks. Kendall/Hunt Publishing Company. Dubuque, Iowa

As for the next theory, much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.{{cite journal | last1= Malin | first1= Michael C. | last2= Edgett | first2= Kenneth S. | s2cid= 129376333 | title= Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission | journal= Journal of Geophysical Research | volume= 106 | issue= E10 | pages= 23429–23570 | year= 2001 | doi= 10.1029/2000JE001455 | bibcode = 2001JGR...10623429M | doi-access= free }}{{cite journal | pmid = 11473309 | author1-link = John F. Mustard | last1 = Mustard | first1 = JF | year = 2001 | pages = 411–4 | issue = 6845 | last2 = Cooper | volume = 412 | first2 = CD | journal = Nature | last3 = Rifkin | first3 = MK | title = Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. | url = http://www.planetary.brown.edu/pdfs/2610.pdf | doi = 10.1038/35086515 | bibcode = 2001Natur.412..411M | s2cid = 4409161 | access-date = 2012-03-13 | archive-date = 2016-06-10 | archive-url = https://web.archive.org/web/20160610025332/http://www.planetary.brown.edu/pdfs/2610.pdf | url-status = dead }}{{cite journal | last1= Carr | first1= Michael H. | title= Mars Global Surveyor observations of Martian fretted terrain | journal= Journal of Geophysical Research | volume= 106 | issue= E10 | pages= 23571–23595 | year= 2001 | doi = 10.1029/2000JE001316 | bibcode=2001JGR...10623571C}} This ice-rich mantle, a few yards thick, smooths the land, but in places it has a bumpy texture, resembling the surface of a basketball. The mantle may be like a glacier and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.[https://web.archive.org/web/20131224133733/http://www.nbcnews.com/id/15702457 NBC News]{{cite journal | last1 = Head | first1 = J. W. | last2 = Marchant | first2 = D. R. | last3 = Kreslavsky | first3 = M. A. | title = From the Cover: Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin | journal = Proceedings of the National Academy of Sciences | volume = 105 | pages = 13258–63 | year = 2008 | doi = 10.1073/pnas.0803760105 |bibcode = 2008PNAS..10513258H | pmid=18725636 | pmc=2734344 | issue=36| doi-access = free }} Because there are few craters on this mantle, the mantle is relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE.{{cite journal | last1 = Christensen | first1 = PR | title = Formation of recent martian gullies through melting of extensive water-rich snow deposits. | journal = Nature | volume = 422 | issue = 6927 | pages = 45–8 | year = 2003 | pmid = 12594459 | doi = 10.1038/nature01436 |bibcode = 2003Natur.422...45C | s2cid = 4385806 }}

The ice-rich mantle may be the result of climate changes.{{Cite web |url=http://news.nationalgeographic.com/news/2008/03/080319-mars-gullies_2.html |title=Melting Snow Created Mars Gullies, Expert Says |access-date=2012-03-13 |archive-date=2008-05-04 |archive-url=https://web.archive.org/web/20080504022016/http://news.nationalgeographic.com/news/2008/03/080319-mars-gullies_2.html |url-status=dead }} Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor will condense on the particles, then fall down to the ground due to the additional weight of the water coating. When Mars is at its greatest tilt or obliquity, up to 2 cm of ice could be removed from the summer ice cap and deposited at midlatitudes. This movement of water could last for several thousand years and create a snow layer of up to around 10 meters thick.{{cite journal | last1=Jakosky | first1=Bruce M. | last2=Carr | first2=Michael H. | title=Possible precipitation of ice at low latitudes of Mars during periods of high obliquity | journal=Nature | volume=315 | pages=559–561 | bibcode = 1985Natur.315..559J | year=1985 | doi = 10.1038/315559a0 | issue=6020| s2cid=4312172 | url=https://zenodo.org/record/1233025 }}{{cite journal | last1= Jakosky | first1= Bruce M. | last2= Henderson | first2= Bradley G. | last3= Mellon | first3= Michael T. | title= Chaotic obliquity and the nature of the Martian climate | journal= Journal of Geophysical Research | volume= 100 | issue= E1 | pages= 1579–1584 | bibcode = 1995JGR...100.1579J | year= 1995 | doi = 10.1029/94JE02801 }} When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulating the remaining ice.{{cite news | author=MLA NASA/Jet Propulsion Laboratory |date = December 18, 2003 | title= Mars May Be Emerging From An Ice Age |work= ScienceDaily |access-date= February 19, 2009 |url= https://www.sciencedaily.com/releases/2003/12/031218075443.htm }} Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow.

Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude.{{cite journal|last1=Hecht |first1=M |title=Metastability of liquid water on Mars |pages=373–386 |year=2002 |volume=156 |issue=2 |doi=10.1006/icar.2001.6794 |journal=Icarus |url=http://www.geo.brown.edu/geocourses/geo292/papers/Hecht2002.pdf |bibcode=2002Icar..156..373H }}{{dead link|date=July 2017 |bot=InternetArchiveBot |fix-attempted=yes }}

The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on Greenland's east coast.{{cite journal |last1=Peulvast | first1=J.P. |year= 1988 |title= Mouvements verticaux et genèse du bourrelet Est-groenlandais. dans la région de Scoresby Sund | journal=Physio Géo |volume= 18 |pages= 87–105 | language=fr }} Since the gullies occur on steep slopes only a small decrease of the shear strength of the soil particles is needed to begin the flow. Small amounts of liquid water from melted ground ice could be enough.{{cite journal | last1=Costard |first1= F. |year=2001 |title= Debris Flows on Mars: Analogy with Terrestrial Periglacial Environment and Climatic Implications | journal= Lunar and Planetary Science | volume= XXXII |pages= 1534 |bibcode = 2001LPI....32.1534C | url= http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1534.pdf |display-authors=etal}}http://www.spaceref.com:16090/news/viewpr.html?pid=7124{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}, Calculations show that a third of a mm of runoff can be produced each day for 50 days of each Martian year, even under current conditions.{{cite journal | last1= Clow | first1= G | title= Generation of liquid water on Mars through the melting of a dusty snowpack | journal= Icarus | volume= 72 | issue= 1 | pages= 93–127 | year= 1987 | bibcode = 1987Icar...72...95C | doi = 10.1016/0019-1035(87)90123-0 }}

Image:ESP_025771variousgullies.jpg|A variety of gullies originating at different levels are visible in this HiRISE image that was taken under the HiWish program.

Image:25771gullybenches.jpg|This enlargement of a small part of the previous image shows terraces along a gully channel. The terraces were created when a new channel cut through the old surface. This means that the gully was not in a single event. Water must have flowed more than once in this location.

Image:ESP_028290_2285gullies.jpg|Gullies in a crater. Some seem to be young, others are well developed. Picture was taken by HiRISE under the HiWish program.

Image:24334moundgullies.jpg|Gullies on a mound, as seen by HiRISE under HiWish program

ESP 044707 2285gullies.jpg|Gullies along mesa wall in North Tempe Terra, as seen by HiRISE under HiWish program

ESP 052737 2305gullies.jpg|Wide view of gullies, as seen by HiRISE under HiWish program

52737 2305gulliespolygons.jpg|Close view of gully alcoves, as seen by HiRISE under HiWish program. Polygons are visible.

{{main|Latitude dependent mantle}}

File:50456 2250mantle2.jpg

Much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. This ice-rich mantle, a few yards thick, makes the surface look very smooth. Because there are few craters on this mantle, the mantle is relatively young.

Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water returns to the ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor condenses on the particles, and then they fall down to the ground due to the additional weight of the water coating. When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice.{{cite news | author=MLA NASA/Jet Propulsion Laboratory |date=December 18, 2003 | title= Mars May Be Emerging From An Ice Age |work= ScienceDaily |access-date=February 19, 2009 |url= https://www.sciencedaily.com/releases/2003/12/031218075443.htm }}

Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past."The Surface of Mars" Series: Cambridge Planetary Science (No. 6) {{ISBN|978-0-511-26688-1}} Michael H. Carr, United States Geological Survey, Menlo Park{{page needed|date=June 2017}} Lobate convex features on the surface known as viscous flow features and lobate debris aprons, which show the characteristics of non-Newtonian flow, are now almost unanimously regarded as true glaciers.{{cite journal | last1 = Milliken | first1 = R. E. | last2 = Mustard | first2 = J. F. | last3 = Goldsby | first3 = D. L. | s2cid = 12628857 | year = 2003 | title = Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images | journal = Journal of Geophysical Research | volume = 108 | issue = E6| page = 5057 | doi=10.1029/2002je002005 | bibcode=2003JGRE..108.5057M}}{{cite journal | last1 = Squyres | first1 = S.W. | last2 = Carr | first2 = M.H. | year = 1986 | title = Geomorphic evidence for the distribution of ground ice on Mars | url = https://zenodo.org/record/1230966| journal = Science | volume = 213 | issue = 4735| pages = 249–253 | doi = 10.1126/science.231.4735.249 | pmid = 17769645 | bibcode = 1986Sci...231..249S | s2cid = 34239136 }}{{cite journal | last1 = Head | first1 = J.W. | last2 = Marchant | first2 = D.R. | last3 = Dickson | first3 = J.L. | last4 = Kress | first4 = A.M. | year = 2010 | title = Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = 3–4 | pages = 306–320 | doi=10.1016/j.epsl.2009.06.041 | bibcode=2010E&PSL.294..306H}}{{cite journal | last1 = Holt | first1 = J.W. |display-authors=et al | year = 2008 | title = Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars | journal = Science | volume = 322 | issue = 5905| pages = 1235–1238 | doi=10.1126/science.1164246 | pmid=19023078| bibcode = 2008Sci...322.1235H | hdl = 11573/67950 | s2cid = 36614186 }}{{cite journal | last1 = Morgan | first1 = G.A. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2009 | title = Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events | journal = Icarus | volume = 202 | issue = 1| pages = 22–38 | doi=10.1016/j.icarus.2009.02.017 | bibcode=2009Icar..202...22M}}{{cite journal | last1 = Plaut | first1 = J.J. | last2 = Safaeinili | first2 = A. | last3 = Holt | first3 = J.W. | last4 = Phillips | first4 = R.J. | last5 = Head | first5 = J.W. | last6 = Sue | first6 = R. | last7 = Putzig | first7 = A. | s2cid = 17530607 | year = 2009 | title = Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars | journal = Geophys. Res. Lett. | volume = 36 | issue = 2| page = L02203 | doi=10.1029/2008gl036379| bibcode = 2009GeoRL..36.2203P | doi-access = free }}{{cite journal | last1 = Baker | first1 = D.M.H. | last2 = Head | first2 = J.W. | last3 = Marchant | first3 = D.R. | year = 2010 | title = Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian | journal = Icarus | volume = 207 | issue = 1| pages = 186–209 | doi=10.1016/j.icarus.2009.11.017 | bibcode=2010Icar..207..186B}}{{cite journal | last1 = Arfstrom | first1 = J. | year = 2005 | title = Terrestrial analogs and interrelationships | journal = Icarus | volume = 174 | issue = 2| pages = 321–335 | doi=10.1016/j.icarus.2004.05.026 | bibcode=2005Icar..174..321A}}

{{main|Glaciers on Mars}}

ESP 050483 2240glacier.jpg|Glacier, as seen by HiRISE under HiWish program

Image:Wide view of Debris Apron.jpg|View of lobate debris apron along a slope. Lobate debris aprons are considered to be glaciers covered with a layer of debris. Image located in Arcadia quadrangle.

Image:23503esker.jpg|Esker, as seen by HiRISE under the HiWish program Eskers form when a stream runs under a glacier.

File:ESP 054900 2305lda.jpg|Lobate debris apron (LDA) around a mound, as seen by HiRISE under the HiWish program

Many places on Mars show channels of different sizes. Many of these channels probably carried water for a time. The climate of Mars may have been such in the past that water ran on its surface. It has been known for some time that Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as the Moon stabilizes Earth; at times the tilt of Mars has even been greater than 80 degrees{{cite journal | last1 = name | last2 = Touma | first2 = J. | last3 = Wisdom | first3 = J. | year = 1993 | title = The Chaotic Obliquity of Mars | journal = Science | volume = 259 | issue = 5099| pages = 1294–1297 | doi=10.1126/science.259.5099.1294| bibcode = 1993Sci...259.1294T | pmid=17732249| s2cid = 42933021 }}{{cite journal | last1 = Laskar | first1 = J. | last2 = Correia | first2 = A. | last3 = Gastineau | first3 = M. | last4 = Joutel | first4 = F. | last5 = Levrard | first5 = B. | last6 = Robutel | first6 = P. | year = 2004 | title = Long term evolution and chaotic diffusion of the insolation quantities of Mars | journal = Icarus | volume = 170 | issue = 2| pages = 343–364 | doi=10.1016/j.icarus.2004.04.005 | bibcode=2004Icar..170..343L| citeseerx = 10.1.1.635.2720 | s2cid = 33657806 }}

Wikiperepelkin.jpg|Perepelkin, as seen by CTX camera (on Mars Reconnaissance Orbiter)

Wikiperepelkinmantle.jpg|Channels and mantle, as seen by CTX camera (on Mars Reconnaissance Orbiter). Channels are exposed where the mantle has disappeared. Mantle falls from the sky during certain climates. Note: this is an enlargement of the previous image of Perepelkin Crater.

Image:ESP_025336channels.jpg|Channels, as seen by HiRISE under HiWish program. Stream appears to have eroded through a hill.

ESP 045868 2245channel.jpg|Channel, as seen by HiRISE under HiWish program. Arrow points to a crater that was probably eroded by flowing water.

ESP 045895 2225channelstroughs.jpg|Channel that went across trough, as seen by HiRISE under HiWish program

File:ESP 055508 2245channels.jpg|Channels, as seen by HiRISE under HiWish program

File:ESP 055297 2260channels.jpg|Channels, as seen by HiRISE under HiWish program The channel in places seems to disappear and then reappear. Water was probably flowing underground.

File:C hannels 64528 2255.jpg|Group of large and small channels

Tilted layers along slopes, especially along crater walls are believed to be the remains of a once wide spread material that has mostly been eroded away. Today, all that we see is in protected spots like against slopes or in craters. They are smooth due to the action of the wind whioh may have been blowing for millions of years.{{cite journal | last1 = Carr | first1 = M | year = 2001 | title = Mars Global Surveyor observations of martian fretted terrain | journal = J. Geophys. Res. | volume = 106 | issue = E10 | pages = 23571–23593 | doi=10.1029/2000je001316 | bibcode=2001JGR...10623571C}}

{{main|Upper Plains Unit}}

ESP 046329 2280pyramids.jpg|Wide view of slopes that contain tilted layered features, as seen by HiRISE under HiWish program

46329 2280pyramids.jpg|Close view of slopes that contain tilted layered features, as seen by HiRISE under HiWish program. Note: this is an enlargement from the previous image.

Linear ridge networks are found in various places on Mars in and around craters.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. These features have also been called "polygonal ridge networks", "boxwork ridges", and "reticulate ridges".Moore, J., D. Wilhelms. 2001. Hellas as a possible site of ancient ice-covered lakes on Mars. Icarus: 154, 258-276. 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. It is thought that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids cemented the structures. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind.Kerber, L., et al. 2017. Polygonal ridge networks on Mars: Diversity of morphologies and the special case of the Eastern Medusae Fossae Formation. Icarus. Volume 281. Pages 200-219

ESP 047054 2160ridges.jpg|Wide view of ridge network, as seen by HiRISE under HiWish program

47054 2160largeridgeschanging.jpg|Close view of small and large ridges, as seen by HiRISE under HiWish program

File:Ridges ESP 074906 2160.jpg|Ridges

File:Ridges in ESP 074906 2160.jpg|Ridges

File:74906 2160wideridgescratercropped.jpg|Ridges. A channel that has transverse aeolian ridges on the foor is also visible.

File:ESP 074906 2160-2ridgesclose.jpg|Close view of ridges

Transverse Aeolian Ridges (TAR's) are common on Mars in low areas. As such they can mark where channels are. They are sort of like sand dunes, but are light toned. Sand dunes on Mars are very dark. We are not quite sure how they form.

File:ESP 083016 2160ridges 01.jpg|Wide view of Transverse Aeolian Ridges (TAR's) and ridges, as seen by HiRISE through HiWish program. The black strip is due to an equipment malfunction.

File:ESP 083016 2160ridges 02.jpg|Transverse Aeolian Ridges (TAR's) as seen by HiRISE through HiWish program. TAR's are visible in the low areas.

File:ESP 083016 2160ridges 03.jpg|Close view of Transverse Aeolian Ridges (TAR's) as seen by HiRISE through HiWish program

File:ESP 083016 2160ridges 04.jpg|Close view of Transverse Aeolian Ridges (TAR's) as seen by HiRISE through HiWish program

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. On the Earth, many sedmentary rocks are formed when sediments like clay settle to the bottom of a lake and then become compacted and cemented. So, layers can be associated with water in the past; hence, possible remains of life may be found in that location.Namowitz, S. and D. Stone. 1975. earth science The World We Live In. American Book Company. {{cite web|url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |access-date=2012-08-04}}

A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.

43824 2160layers.jpg|Layers, as seen by HiRISE under HiWish program. Location is Tempe Terra. Note: this is an enlargement of the previous image.

File:ESP 054847 2110crater.jpg|Wide view of crater with layers near the top, as seen by HiRISE under HiWish program

File:54847 2110craterlayers.jpg|Close, color view of layers near top of crater, as seen by HiRISE under HiWish program

File:ESP 055652 2245layers.jpg|Wide view of layers in a trough, as seen by HiRISE under HiWish program

File:55652 2245layersboulders.jpg|Close view of layers and boulders in the wall of a trough, as seen by HiRISE under HiWish program

File:55652 2245layersclose.jpg|Close, color view of layers in a trough, as seen by HiRISE under HiWish program

Impact craters develop when a fast-moving object collides with the surface of a planet, moon, or asteroid.

Rocks and dirt are blasted out and then deposited around the crater as ejecta. Some of the material comes from deep underground; therefore, samples gathered from that place can tell us about minerals under the surface. At first, a bowl-shaped cavity is made with a rim along the outside. As time passes, the ejecta gets covered with dust and the cavity gets less deep.

Most impact craters are roughly circular due to the explosion of energy outwards from the impact point. https://askanearthspacescientist.asu.edu/top-question/how-craters-form#:~:text=For%20example%2C%20rocks%20collected%20from,energy%20to%20the%20surrounding%20rock

Many Martian craters once contained lakes. Many show channels leading into the crater. Others, show channels that have inlets and outlets for water. Those are called open lakes. Some liquid water may come from the heat of the impact melting ground ice. Water may last for some time in such a lake as ice will form at the top and lower the loss of water. Also, a layer of dust may settle on the ice to further insulate it.Cabrol, N. and E. Grin. 2001. The Evolution of Lacustrine Environments on Mars: Is Mars Only Hydrologically Dormant? Icarus: 149, 291-328.Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Implications of valley network lakes for the nature of Noachian hydrology. Primitive organisms may have developed in some lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet.Newsom H., Hagerty J., Thorsos I. 2001. Location and sampling of aqueous and hydrothermal deposits in martian impact craters. Astrobiology: 1, 71-88.

There are many different types of craters on Mars. A Ring mold crater looks like the ring molds used in baking. Many researchers believe they are created by an impact into ice. The ice is covered by a layer of debris, but many impacts are strong enough to penetrate far enough to go into the ice layer. The impact compresses the ice and then rebounds. They are found in parts of Mars that have buried ice. Laboratory experiments show that impacts into ice result in a "ring mold shape." They are also bigger than other craters in which an asteroid impacted solid rock. Impacts into ice warm the ice and cause it to flow into the ring mold shape. These craters are common in lobate debris aprons and lineated valley fill.Kress, A., J. Head. 2008. Ring-mold craters in lineated valley fill and lobate debris aprons on Mars: Evidence for subsurface glacial ice. Geophys.Res. Lett: 35. L23206-8Baker, D. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209Kress., A. and J. Head. 2009. Ring-mold craters on lineated valley fill, lobate debris aprons, and concentric crater fill on Mars: Implications for near-surface structure, composition, and age. Lunar Planet. Sci: 40. abstract 1379 They may be an easy way for future colonists of Mars to find water ice.

After a number of years a modification of the formation of ring mold craters being formed by impact into an ice layer was presented at a Planetary Science conference in Texas in 2018. This new hypothesis involves mantle layers.Baker, D., L. Carter. 2018. Formation of Impact Crater Landforms within Glacial Deposits on Mars. 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083). 1589.pdf

Image:Arcadia Map.JPG|Map of Arcadia quadrangle with major features labeled. Several large cracks called Fossae are in this area.

Wikibarabashovmap.jpg|Map showing location of Barabashov Crater and other nearby craters

Wikibarbashovmola.jpg|MOLA and CTX image of Barabashov Crater

ESP 052686 2120layersridges.jpg|Crater with channels and ridges, as seen by HiRISE under HiWish program Note the channel on the rim. This crater probably once held a lake.

52689 2120ridges.jpg|Ridges on crater floor, as seen by HiRISE under HiWish program

52689 2120ridgesclose.jpg|Close view of ridges on crater floor, as seen by HiRISE under HiWish program. Ridges are seen to be breaking up into boulders.

File:Ring mold crater ESP 076674 2160.jpg|Ring mold crater. Ring mold craters are caused by a rebound of an ice layer after being struck by an impacting body.

File:ESP 055389 2280doublecrater.jpg|Double crater, as seen by HiRISE under HiWish program Here the impacting body broke into two right before it struck the ground.

File:ESP 028672 2235hollows.jpg|Hollows formed by erosion on floor of crater, as seen by HiRISE under HiWish program

File:56628 2150hollows.jpg|Close view of hollows, as seen by HiRISE under HiWish program

File:ESP 056628 2150hollows.jpg|Wide view of craters, layers, streaks, hollows. Picture taken with HiRISE under HiWish program

File:ESP 055600 2240lavaflow.jpg|Lava flows, as seen by HiRISE under HiWish program

{{div col|colwidth=30em}}

• Dark slope streak
• Dust Devil Tracks
• Fossa (geology)
• Fretted terrain
• Glaciers on Mars
• HiRISE
• HiWish program
• Impact crater
• Linear ridge networks
• Lobate debris apron
• Martian Gullies
• Perepelkin (Martian crater)

{{div col end}}

{{reflist|colwidth=30em}}

{{commons category|Arcadia quadrangle}}

{{Mars quadrangle layout}}

{{Mars}}

{{Portal bar|Solar System}}

Category:Mars