{{Short description|Terra on Mars}} [[File:Wikimolaargyre.jpg|thumb|MOLA map showing boundaries for Margaritifer Terra and other regions. Color indicates elevation.]] '''Margaritifer Terra''' ({{IPAc-en|ˌ|m|ɑːr|ɡ|ə|ˈ|r|ɪ|t|ə|f|ər|_|ˈ|t|ɛr|ə}}) is an ancient, heavily cratered region of [[Mars]]. It is centered just south of the Martian equator at {{Coord|4.9|S|25|W|globe:mars_type:landmark|display=inline,title}} and covers 2600&nbsp;km at its widest extent.<ref>{{gpn|63870}}</ref> The area reveals "[[chaos terrain]]", [[outflow channels]], and [[Alluvium|alluvial]] plains that are indicative of massive flooding. [[Aeolian processes|Wind erosion]] patterns are also in evidence. A region within the terra shows some of the highest valley network densities on the planet. [[Ares Vallis]] is another notable feature, where the flood and flow patterns are in evidence; it was the landing site of the Soviet ''[[Mars 6]]'' lander<ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1973-052A|title=Mars 6|publisher=US National Space Science Data Centre|access-date=12 April 2013|archive-date=27 February 2017|archive-url=https://web.archive.org/web/20170227064416/http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1973-052A|url-status=dead}}</ref> and [[NASA]]'s ''[[Mars Pathfinder]]''.<ref>{{cite web | url=http://mpfwww.jpl.nasa.gov/MPF/science/geology.html | title=Mars Pathfinder Science Results | work=NASA | access-date=2008-06-09 | archive-url=https://web.archive.org/web/20080920093840/http://mpfwww.jpl.nasa.gov/MPF/science/geology.html | archive-date=2008-09-20 | url-status=dead }}</ref> It was also one of several proposed landing sites for the [[Mars 2020 Rover]].<ref>{{cite news |url=https://asunews.asu.edu/20140516-mars-2020 |title=Choosing a place to land NASA's next Mars rover |work=Arizona State University News |date=16 May 2014 |access-date=2014-05-17 }}</ref>

[[Holden (Martian crater)|Holden]] and [[Eberswalde (crater)|Eberswalde]], craters in Margaritifer Terra, are thought to have formerly held lakes because they contain deltas and iron/magnesium smectite minerals which need water to form.<ref>Murchie, S. et al. 2009. A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter. Journal of Geophysical Research: 114.</ref> The [[Uzboi-Landon-Morava (ULM)]] system of paths for water flow is found in Margaritifer Terra. Researchers think that great flood channels in this region were carved quickly in just weeks or months by catastrophic outflows of groundwater.<ref>{{cite web | url=https://www.uahirise.org/ESP_054753_1825 | title=HiRISE &#124; Uplifted Blocks of Light-Toned Layered Deposits (ESP_054753_1825) }}</ref> Because forming hematite requires liquid water, which could not long exist without a thick atmosphere, Mars must have had a much thicker atmosphere at some time in the past.<ref>{{cite web |url=http://themis.asu.edu/discoveries-aramchaos |title=Mars Odyssey Mission THEMIS: Discoveries |website=themis.asu.edu |url-status=dead |archive-url=https://web.archive.org/web/20060101053043/http://themis.asu.edu/discoveries-aramchaos |archive-date=2006-01-01}} </ref>

Margaritifer Terra was named in 1979, after the [[Pearl Fishery Coast|Pearl Coast]], south [[India]]. Part of it is found in the [[Margaritifer Sinus quadrangle]] and part in the [[Oxia Palus quadrangle]].

==Layers== {{Main|Groundwater on Mars#Layered terrain}} Some of the images from this region display 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.<ref>{{cite web|url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE &#124; High Resolution Imaging Science Experiment |publisher=University of Arizona |access-date=2012-08-04}}</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.

<gallery class="center" widths="190px" heights="180px"> Image:26996layeredwhitebuttes.jpg|Butte in Arsinoes Chaos with some light-toned layers, as seen by HiRISE under [[HiWish program]] Wikiarsinoesfanswide.jpg|Light-toned deposit in Arsinoes Chaos, as seen by CTX camera (on Mars Reconnaissance Orbiter). WikiESP 039352 1730lighttoneddeposit.jpg|Light-toned deposit in Arsinoes Chaos, as seen by HiRISE under HiWish program. Note: this field can be found in the previous wide image of Arsinoes Chaos, as seen by CTX camera (on Mars Reconnaissance Orbiter). File:ESP 028618 1760layers.jpg|Layered butte, as seen by HiRISE under HiWish program.

Image:ESP_024807whitebutte.jpg|Light toned butte on floor of crater, as seen by HiRISE under HiWish program. Arrows show outcrops of light toned material. Light toned material is probably sulfate-rich and similar to material examined by Spirit Rover, and it once probably covered the whole floor. Other images below show enlargements of the butte.

24807whitebuttei.jpg|Enlargement of white butte, as seen by HiRISE under HiWish program Box shows size of a football field.

24807 1755whitebuttezoomed.jpg|Closer view towards top of white butte, as seen by HiRISE under HiWish program Box shows size of a football field.

24807 1755whitebuttetop.jpg|Top of white butte, as seen by HiRISE under HiWish program Box shows size of a football field.

Image:Aureum Chaos wide context.JPG|THEMIS image of wide view of following HiRISE images. Black box shows approximate location of HiRISE images. This image is just a part of the vast area known as [[Aureum Chaos]]. Click on image to see more details. Image:Aureum Chaos wide view.JPG|Aureum Chaos, as seen by HiRISE, under the [[HiWish program]]. Image:Aureum Chaos HiWish.JPG|Close up view of previous image, as seen by HiRISE under HiWish program. Small round dots are boulders.

Image:Canyons and Mesas of Aureum Chaos in Oxia Palus.JPG|Huge canyons in [[Aureum Chaos]]. Gullies are rare at this latitude. Picture taken by THEMIS. Image:Aureum Chaos from Themis.JPG|Aureum Chaos, as seen from THEMIS.

</gallery>

On April 1, 2010, NASA released the first images under the HiWish program, with the public suggesting places for HiRISE to photograph. One of the eight locations was Aureum Chaos.<ref>{{Cite web |url=http://www.uahirise.org/releases/hiwish-captions.php |title=Captioned Images Inspired by HiWish Suggestions (HiRISE) |access-date=2015-02-25 |archive-date=2016-12-24 |archive-url=https://web.archive.org/web/20161224141735/http://www.uahirise.org/releases/hiwish-captions.php |url-status=dead }}</ref> The first image below gives a wide view of the area. The next two images are from the HiRISE image.<ref>{{cite web |last1=Okubo |first1=Chris |title=Mesas in Aureum Chaos |url=https://hirise.lpl.arizona.edu/ESP_016869_1775 |website=HiRise |publisher=University of Arizona |access-date=11 June 2019 |date=31 March 2010}}</ref>

<gallery class="center" widths="230px" heights="220px"> Image:Aureum Chaos wide context.JPG|THEMIS image of wide view of following HiRISE images. Black box shows approximate location of HiRISE images. This image is just a part of the vast area known as Aureum Chaos. Click on image to see more details. Image:Aureum Chaos wide view.JPG|Aureum Chaos, as seen by HiRISE, under the [[HiWish program]]. Image:Aureum Chaos HiWish.JPG|Close up view of previous image, as seen by HiRISE under HiWish program. Small round dots are boulders. 042055 1580layersclose.jpg|Close up of layers in Lotto Crater, as seen by HiRISE under HiWish program </gallery>

==Yardangs== <gallery class="center" widths="230px" heights="220px"> WikiESP 039563 1730yardangs.jpg|[[Yardangs]] formed in light-toned material and surrounded by dark, volcanic basalt sand, as seen by HiRISE under HiWish program. WikiESP 039563 1730yardangsclose.jpg|Close-up image of yardangs, as seen by HiRISE under HiWish program. Arrows point to transverse aeolian ridges, TAR's, a type of dune. Note this is an enlargement of the previous image from HiRISE. 48582 1845layersyardangs.jpg|Yardangs and layers, as seen by HiRISE under HiWish program Arrows point to some yardangs. </gallery>

==Other images of Margaritifer Terra== <gallery class="center" widths="190px" heights="180px"> ESP 045800 1540channel.jpg|Channel, as seen by HiRISE, under HiWish program

ESP 048582 1845hangingvalleys.jpg|Hanging valleys in [[Aram Chaos]], as seen by HiRISE under HiWish program </gallery>

==See also== *[[Areas of chaos terrain on Mars]] *[[Geography of Mars]] *[[Groundwater on Mars]] *[[Lakes on Mars]] *[[Uzboi-Landon-Morava (ULM)]]

==References== {{Reflist}}

==External links== * [https://www.youtube.com/watch?v=DGBbke1wJRk Lakes on Mars - Nathalie Cabrol] (SETI Talks) * [https://web.archive.org/web/20120206161335/http://www.dartmouth.edu/~humbio01/interactive/MargaritiferTerra.html Dartmouth] * [https://web.archive.org/web/20070927025900/http://www.astrobio.net/cgi-bin/h2p.cgi?sid=573&ext=.pdf Astrobio.net] * [https://web.archive.org/web/20060827182041/http://www.nasm.si.edu/ceps/research/grant/grant_marg2.pdf J.A. Grant, 'Valley Evolution in Margaritifer Sinus, Mars'] * [https://purl.fdlp.gov/GPO/gpo45480 Geologic Map of MTM -15027, -20027, -25027, and -25032 Quadrangles, Margaritifer Terra Region of Mars] [[United States Geological Survey]]

[[Category:Terrae on Mars]] [[Category:Margaritifer Sinus quadrangle]] [[Category:Oxia Palus quadrangle]]