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. This motion includes landslides and sand advancing at the dune front (upper left); changes in the position of the rest of the dune boundary relative to the fixed, underlying terrain; and changes in the position of ripples on the dune surface. Credit: NASA/JPL-Caltech/Univ. of Ariz./JHUAPL