The circular
feature is 2.5 miles (4 kilometers) across and lies near the south pole of Mars – a mystery
when first seen in Mariner 9 and Viking Orbiter images during the 1970s. Now
the Mars Reconnaissance Orbiter has taken new high resolution images that may
help scientists interpret this Martian feature.
Bright
areas are covered by carbon dioxide frost, with a "swiss cheese"
pattern common at the south polar residual cap. The circular evenness of the
depression suggests an impact crater, but there is no evidence of a crater rim
or debris unless it lies beneath the frost. While the depression may have
formed by collapse, the image is missing the typical ground fractures that form
around a collapse pit. Further analysis of the data may eventually uncover more
clues.
--NASA/JPL/University of Arizona and SPACE.com Staff
Credit: NASA/JPL/University of Arizona
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