Southern Polar Cap Mars has a seasonal southern polar cap
composed of carbon dioxide (CO2, commonly known as dry ice),
that overlies a permanent polar cap which is a mixture of CO2
ice, water ice and dust. As the CO2 evaporates in the spring the
escaping gas carves channels in the permanent cap below. Often
these channels radiate outward (or converge inward), giving them
a spider-like appearance. In this false color image the seasonal
frost is whitish-lavendar. The tan areas starting to show
through are where the frost has already evaporated (sublimated
is actually the correct term, when ice changes directly to a
gas). Tan-colored dust blows around and accummulates in the
bottom of some of the channels. This is truly other-worldly
terrain, with exotic landforms with no earthly analogs.