In the winter a portion of Mars’ carbon dioxide atmosphere condenses onto the surface forming seasonal polar caps. In the spring as the sun gets higher in the sky this ice sublimates (goes directly from solid to gas).

We see many seasonal phenomena associated with the sublimation of the carbon dioxide ice (dry ice). In this observation, we are looking at barchan dunes, made of dark basaltic sand (like in Hawaii) mostly still covered with ice.

Where there are cracks in the ice the dark sand can be seen escaping. Some cracks are at the crests of the dunes, and the sand is freed to slide down the slipface of the dunes. The cracks in the ice develop as a result of gas from sublimation being trapped under the ice - when the pressure gets high enough it cracks the ice.

Written by: Candy Hansen  (31 January 2012)