Covered by seasonal carbon dioxide frost, the dune field here in Richardson Crater has only partially defrosted, although the image was acquired late in Mars’ southern spring.

Large patches of carbon dioxide frost are observed, linked in some places by channels possibly carved into the ground by the erosion of carbon dioxide gas, as blocks dry ice slide down slope and sublimate (evaporate directly from solid to gas). Numerous dust devil tracks have left their mark.
Written by: Candy Hansen   (22 December 2010)

More info and image formats at http://hirise.lpl.arizona.edu/PSP_004230_1080

Image: NASA/JPL/University of Arizona