Unlike the rolling volcanic plains of the north, the southern
half of Mars is dominated by older, heavily cratered highlands. The distinctly
lunar-like terrain of Terra Sirenum belies the fact that, unlike the Earth's Moon, Mars has an
active
atmosphere.
In this rendering the perspective is from an
altitude of about 30 miles and about 30°from Mars' south pole. The large
crater with a central peak at the 2 o'clock position near the horizon is Liu Hsin, with a diameter of 80 miles. Just beyond Liu Hsin
is the
southern rim of a much larger crater named Copernicus, with a diameter of 180
miles. To the west, high-flying cirrus clouds of water ice crystals form complex patterns
in the tenuous carbon dioxide atmosphere.