South (Martian crater)

South Crater is an impact crater in the Mare Australe quadrangle of Mars, located at 77.1°S latitude and 338.0°W longitude. It is 107.1  km in diameter and was named after Sir James South, and the name was approved in 1973 by the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN).^[1]

Very close to the crater there is what has been named "Swiss cheese" features. Swiss cheese features (SCFs) are pits so named because they look like the holes in Swiss cheese. They were first seen in 2000 using Mars Orbiter Camera imagery.^[2] They are usually a few hundred meters across and 8 metres deep, with a flat base and steep sides. They tend to have similar bean-like shapes with a cusp pointing towards the south pole. The angle of the sun probably contributes to their roundness. Near the Martian summer solstice, the sun can remain continuously just above the horizon; as a result the walls of a round depression will receive more intense sunlight, and sublimate much more rapidly than the floor. The walls sublimate and recede, while the floor remains the same.^[3][4] As the seasonal frost disappears, the pit walls appear to darken considerably relative to the surrounding terrain. The SCFs have been observed to grow in size, year by year, at an average rate of 1 to 3 meters, suggesting that they are formed in a thin layer (8m) of carbon dioxide ice lying on top of water ice.^[5][6]

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  East side of South crater (Martian crater), as seen by CTX camera (on Mars Reconnaissance Orbiter).

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  Layers in southern part of mound in South crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image of east side of South crater.

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  Layers just outside the rim of South crater in the form of "Swiss cheese," as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of a previous image of east side of South crater.

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  Western side of South crater, as seen by CTX camera (on Mars Reconnaissance Orbiter).

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  Layers in mound in western side of South crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of a previous image of west side of South crater.

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  Layers just outside rim of western side of South crater in the form of "Swiss cheese," as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of a previous image of west side of South crater.

See also

• Climate of Mars
• Geology of Mars
• Impact crater
• List of craters on Mars
• Geyser (Mars)
• Swiss cheese features

References

1. "Gazetteer of Planetary Nomenclature | South". usgs.gov. International Astronomical Union. Retrieved 4 March 2015.
2. Thomas, P. C.; et al. (2000). "North-south geological differences between the residual polar caps on Mars". Nature. 404 (6774): 161–4. doi:10.1038/35004528. PMID 10724162.
3. Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY.
4. Mangold, N. 2011. Ice sublimation as a geomorphic process: A planetary perspective. Geomorphology. 126:1-17.
5. Byrne, S.; Ingersoll, A. P. (2002). "A Sublimation Model for the Formation of the Martian Polar Swiss-cheese Features". American Astronomical Society. American Astronomical Society. 34: 837. Bibcode:2002DPS....34.0301B.
6. http://hirise.lpl.arizona.edu/PSP_005095_0935