The seasons change on Mars.

With three years of data in hand the researchers report on the sequence and variety of changes that take place over the spring, including outbursts of gas carrying sand, polygonal cracking of the ice on the dunes, sandfalls down the slipface of the dunes, and dark fans of sand propelled out onto the ice. Gas escaping from under the seasonal layer of dry ice erodes channels in the dunes, reminiscent of the erosion that carves more permanent “spider” channels in the southern hemisphere polar region.