Martian Sand Dunes
This image was taken by NASA's Mars Reconnaissance Orbiter and shows sand dunes on the surface of Mars. The linear dunes in this image are unusually uniform, and are thought to have been formed by shifting wind directions. The lighter red color bands on the edge of each dun indicates the wind direction. These dunes are located in the floor of a crater in an area known as Noachis Terra, west of the giant Hellas impact basin.
NASA / JPL-Caltech / University of Arizona