The UA HiRISE camera has captured numerous images showing sand dunes actively moving across the surface of Mars. The images below are from a new paper in Geology showing one of many shifting dunes that were identified. [Below, NASA caption: A dune in the northern polar region of Mars shows significant changes between two images taken on June 25, 2008 and May 21, 2010 by NASA's Mars Reconnaissance Orbiter. Image credit: NASA/JPL-Caltech/Univ. of Ariz./JHUAPL]. The high-resolution photos show details of ripples moving.