South is an
impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...
in the
Mare Australe quadrangle
The Mare Australe quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Mare Australe quadrangle is also referred to as MC-30 (Mars Chart-30). The quadr ...
of
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
, located at 76.9°S latitude and 21.9°E longitude. It measures in diameter, and was named after British astronomer
Sir James South (1785–1867). The name was approved by the International Astronomical Union (IAU)
Working Group for Planetary System Nomenclature
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...
in 1973.
Description
Very close to the crater there are what have 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
The Mars Orbiter Camera and Mars Observer Camera (MOC) were scientific instruments on board the Mars Observer and Mars Global Surveyor spacecraft. The camera was built by Malin Space Science Systems (MSSS) for NASA and the cost of the whole MOC s ...
imagery. They are usually a few hundred meters across and 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.
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 , suggesting that they are formed in a thin layer () of
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
ice lying on top of water ice.
Gallery
South crater 383B08.jpg, Viking Orbiter 2 image
Wikisoutheast.jpg, East side of South crater, as seen by CTX camera (on MRO).
Wikisoutheastlayers.jpg, Layers in southern part of mound in South crater, as seen by CTX camera. Note: this is an enlargement of the previous image of east side of South crater.
Wikisoutheastswiss.jpg, Layers just outside the rim of South crater in the form of "Swiss cheese," as seen by CTX camera. Note: this is an enlargement of a previous image of east side of South crater.
Wikisouthwest.jpg, Western side of South crater, as seen by CTX camera.
Wikisouthwestlayers.jpg, Layers in mound in western side of South crater, as seen by CTX camera. Note: this is an enlargement of a previous image of west side of South crater.
Wikisouthwestswiss.jpg, Layers just outside rim of western side of South crater in the form of "Swiss cheese," as seen by CTX camera. Note: this is an enlargement of a previous image of west side of South crater.
See also
*
List of craters on Mars
References
{{Geography of Mars
Mare Australe quadrangle
Impact craters on Mars