Craters trap wind-blown sand very effectively. In the Southern hemisphere we see fields of sand dunes on the floors of many craters.
Longitudinal dunes cross a portion of the floor of this un-named Southern hemisphere crater. Dust devil tracks that criss-cross the dunes remove a light layer of dust but do not disturb the ripples on the dunes. In the subimage large boulders appear partially buried by the drifting sand.
Written by: Candy Hansen (23 March 2011)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_021641_1205
Image: NASA/JPL/University of Arizona