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{{short description|Planum on Mars}}

factoids

|type = Partially glaciated plains}}Planum Australe (Latin: "the southern plain") is the southern polar plain on Mars. It extends southward of roughly 75°S and is centered at {{Coord|-83.9|160.0|globe:Mars}}. The geology of this region was to be explored by the failed NASA mission Mars Polar Lander, which lost contact on entry into the Martian atmosphere.In July 2018, scientists reported the discovery, based on MARSIS radar studies, of a subglacial lake on Mars, {{convert|1.5|km|mi|abbr=on}} below the southern polar ice cap, and extending sideways about {{convert|20|km|mi|abbr=on}}, the first known stable body of water on the planet.JOURNAL, Orosei, R., etal, Radar evidence of subglacial liquid water on Mars, 25 July 2018, Science (journal), Science, 361, 6401, 490–493, 10.1126/science.aar7268, 2004.04587, 30045881, 11573/1148029, free, 2018Sci...361..490O, NEWS, Chang, Kenneth, Overbye, Dennis, Dennis Overbye, A Watery Lake Is Detected on Mars, Raising the Potential for Alien Life – The discovery suggests that watery conditions beneath the icy southern polar cap may have provided one of the critical building blocks for life on the red planet.,weblink 25 July 2018, The New York Times, 25 July 2018, WEB, Huge reservoir of liquid water detected under the surface of Mars,weblink EurekAlert, 25 July 2018, 25 July 2018, WEB, Liquid water 'lake' revealed on Mars,weblink BBC News, 25 July 2018, 25 July 2018,

Ice cap

File:Mars-SubglacialWater-SouthPoleRegion-20180725.jpg|thumb|right|150px|Site of south polar subglacial water body (reported July 2018)]] Planum Australe is partially covered by a permanent polar ice cap composed of frozen water and carbon dioxide about 3 km thick. A seasonal ice cap forms on top of the permanent one during the Martian winter, extending from 60°S southwards. It is, at the height of winter, approximately 1 meter thick.WEB, Mars is Melting, 2021-04-22,weblink Tony, Phillips, It is possible that the area of this ice cap may be shrinking due to localized climate change.WEB,weblink 2006-10-20, Global warming on Mars?, Steinn, Sigurdsson, RealClimate.org, Claims of more planetwide global warming based on imagery, however, ignore temperature data and global datasets. Spacecraft and microwave data indicate global average temperature is, at most, stable,JOURNAL, Wilson, R., Richardson, M., 2000, The Martian Atmosphere During the Viking I Mission, I: Infrared Measurements of Atmospheric Temperatures Revisited, Icarus, 145, 2, 555–579, 10.1006/icar.2000.6378, 2000Icar..145..555W, 10.1.1.352.9114, and possibly cooling.In 1966, Leighton and Murray proposed that the Martian polar caps provided a store of CO2 much larger than the atmospheric reservoir. However it is now thought that both polar caps are made mostly of water ice. Both poles have a thin seasonal covering of CO2, while in addition the southern pole has a permanent residual CO2 cap, about 8 to 10 metres thick, that lies on top of the water ice. Perhaps the key argument that the bulk of the ice is water is that CO2 ice isn't mechanically strong enough to make a 3 km thick ice cap stable over long periods of time.JOURNAL File:Geysers on Mars.jpg|thumb|right|150px|Depiction of erupting south polar sand-laden jets (Ron Miller)]]Data from ESA's Mars Express indicates that there are three main parts to the ice cap. The most reflective part of the ice cap is approximately 85% dry ice and 15% water ice. The second part, where the ice cap forms steep slopes at the boundary with the surrounding plain, is almost exclusively water ice. Finally, the ice cap is surrounded by permafrost fields that extend for tens of kilometres north away from the scarps.WEB,weblink Water at Martian south pole, 2006-10-22, European Space Agency, The centre of the permanent ice cap is not located at 90°S but rather approximately 150 kilometres north of the geographical south pole. The presence of two massive impact basins in the western hemisphere – Hellas Planitia and Argyre Planitia – creates an immobile area of low pressure over the permanent ice cap. The resulting weather patterns produce fluffy white snow which has a high albedo. This is in contrast to the black ice that forms in the eastern part of the polar region, which receives little snow.WEB,weblink Mars' South Pole mystery, 2006-10-26, Spaceflight Now,

Features

There are two distinct subregions in Planum Australe – Australe Lingula and Promethei Lingula. It is dissected by canyons Promethei Chasma, Ultimum Chasma, Chasma Australe and Australe Sulci. It is theorised that these canyons were created by katabatic wind.JOURNAL, Eric J., Kolb, Kenneth L., Tanaka, Accumulation and erosion of south polar layered deposits in the Promethei Lingula region, Planum Australe, Mars, The Mars Journal, 2, 1–9, 2006, 10.1555/mars.2006.0001, 2006IJMSE...2....1K, 53400765, The largest crater in Planum Australe is McMurdo Crater.

Geysers on Mars

The seasonal frosting and defrosting of the southern ice cap results in the formation of spider-like radial channels carved on 1 meter thick ice by sunlight.JOURNAL, Mangold, N, 2011, Ice sublimation as a geomorphic process: A planetary perspective, Geomorphology, 126, 1–2, 1–17, 10.1016/j.geomorph.2010.11.009, Then, sublimed CO2 (and probably water) increase pressure in their interior, producing geyser-like eruptions of cold fluids often mixed with dark basaltic sand or mud.NEWS, NASA Findings Suggest Jets Bursting From Martian Ice Cap, August 16, 2006, NASA,weblink Jet Propulsion Laboratory, 2009-08-11, 2009-10-10,weblink" title="web.archive.org/web/20091010164741weblink">weblink dead, CONFERENCE, H. H., Kieffer, ANNUAL PUNCTUATED CO2 SLAB-ICE AND JETS ON MARS, Mars Polar Science 2000, 2000,weblink 2009-09-06, CONFERENCE, SIMULATIONS OF GEYSER-TYPE ERUPTIONS IN CRYPTIC REGION OF MARTIAN SOUTH, Fourth Mars Polar Science Conference, G., Portyankina, 2006,weblink 2009-08-11, JOURNAL, CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap, Nature, 30 May 2006, Hugh H., Kieffer, Philip R., Christensen, Timothy N., Titus, 442, 7104, 793–796, 10.1038/nature04945, 16915284, 2006Natur.442..793K, 4418194, This process is rapid, observed happening in the space of a few days, weeks or months, a growth rate rather unusual in geology – especially for Mars. The Mars Geyser Hopper lander is a concept mission that would investigate the geysers of Mars.WEB,weblink Design Study for a Mars Geyser Hopper, 2012-07-01, Landis, Geoffrey A., Oleson, Steven J., McGuire, Melissa, 9 January 2012, NASA, CONFERENCE, Landis, Geoffrey A., Oleson, Steven J., McGuire, Melissa, Design Study for a Mars Geyser Hopper, 50th AIAA Aerospace Sciences Conference, Glenn Research Center, NASA, 9 January 2012, AIAA-2012-0631,weblink 2012-07-01,

Saltwater lakes

In September 2020, scientists confirmed the existence of several large saltwater lakes under the ice in the south polar region of the planet Mars. According to one of the researchers, “We identified the same body of water [as suggested earlier in a preliminary initial detection], but we also found three other bodies of water around the main one ... It’s a complex system.”JOURNAL, Lauro, Sebastian Emanuel, et al., Multiple subglacial water bodies below the south pole of Mars unveiled by new MARSIS data,weblink 28 September 2020, Nature Astronomy, 5, 63–70, 10.1038/s41550-020-1200-6, 29 September 2020, 2010.00870, 222125007, JOURNAL, O'Callaghan, Jonathan, Water on Mars: discovery of three buried lakes intrigues scientists – Researchers have detected a group of lakes hidden under the red planet's icy surface.,weblink 28 September 2020, Nature (journal), Nature, 10.1038/d41586-020-02751-1, 32989309, 222155190, 29 September 2020,

See also

• Climate of Mars
• List of plains on Mars
• Martian polar ice caps
• Planum Boreum, the northern polar plain

References

External links

{{Wikinews|Massive ice deposits found on Mars}}

• Accumulation and erosion of south polar layered deposits in the Promethei Lingula region, Planum Australe, Mars
• Planum Australe on Google Mars.
• Stratigraphy and Topography of McMurdo Crater area, Planum Australe, Mars
• Topographic maps of the Martian South Pole
• USGS map of Planum Australe

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