May 13, 2018 - A carbon dioxide ice cap covering the South Pole region of Mars. As the sun returns in the spring, spider-like radiating mounds called araneiform terrain begin to emerge from the landscape. These mounds form when carbon dioxide ice below the surface heats up and releases. The carbon dioxide ice on Mars sublimates as it warms (changes from solid to gas) and the gas becomes trapped below the surface. Over time the trapped carbon dioxide gas builds in pressure and is eventually strong enough to break through the ice as a jet that erupts dust. The gas is released into the atmosphere and darker dust may be deposited around the vent or transported by winds to produce streaks. The loss of the sublimated carbon dioxide leaves behind these spider-like features etched into the surface.
