Swiss cheese features

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Pits in south polar ice cap, taken in consecutive southern hemisphere summers, the first of which was in 1999, the second in 2001. Mars Global Surveyor, NASA

Swiss cheese features (SCFs) are curious pits in the south polar ice cap of Mars (Mare Australe quadrangle) named from their similarity to the holes in Swiss cheese. They were first seen in 2000 using Mars Orbiter Camera imagery.[1] They are typically 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, indicating that insolation is involved in their formation. 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.[2][3] 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.[4][5]

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References[edit]

  1. ^ 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. 
  2. ^ Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY.
  3. ^ Mangold, N. 2011. Ice sublimation as a geomorphic process: A planetary perspective. Geomorphology. 126:1-17.
  4. ^ Byrne, S.; Ingersoll, A. P.; Ingersoll (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. 
  5. ^ http://hirise.lpl.arizona.edu/PSP_005095_0935