At the edge

A piece of Mars: Old, subdued dunes (in blue) near the south pole on Mars. This shows the edge of a dune field, with white rock-strewn surface beyond the sand. Criss-crossing the sand are the tracks that dust devils have left behind. I wonder if these whirlwinds are the main reason why the dunes are slowly eroding to a flat surface. (HiRISE PSP_005980_1085)