Planum Australe
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Planum Australe (Latin: "the southern plain") is the southern polar plain on Mars. It extends southward of roughly 75°S. 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.
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[edit] Ice cap
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 metre thick.<ref>Phillips, Tony. Mars is Melting. Science @ NASA. Retrieved on 2006-10-20.</ref> It is possible that the area of this ice cap may be shrinking due to localised climate change.<ref>Sigurdsson, Steinn. Global warming on Mars?. RealClimate.org. Retrieved on 2006-10-20.</ref>
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.<ref>Water at Martian south pole. European Space Agency. Retrieved on 2006-10-22.</ref>
The centre of the permanent ice cap is not located at 90°S but rather approximately 150 kilometres north and west from 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 blacker snow that forms in the eastern part of the polar region, which receives little snow.<ref>Mars' South Pole mystery. Spaceflight Now. Retrieved on 2006-10-26.</ref>
[edit] Martian spiders
A unique phenomenon associated with the southern ice cap of Mars is the appearance of geological formations which look like spider webs as the carbon dioxide ice thaws in the Martian spring. These are referred to as Martian spiders. The formation of these structures is not fully understood, with many theories being put forward by astrogeologists.
[edit] 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.<ref> Kolb, Eric J., Kenneth L. Tanaka (2006). "Accumulation and erosion of south polar layered deposits in the Promethei Lingula region, Planum Australe, Mars". The Mars Journal 2: 1-9. DOI:10.1555/mars.2006.0001.</ref> The largest crater in Planum Australe is McMurdo Crater.
[edit] References
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[edit] See also
- Planum Boreum, the northern polar plain
