Mars Dunes
NASA/JPL/University of Arizona
The red planet's looking a little blue in the face. This image taken by NASA's Mars Reconnaissance Orbiter at the end of August shows the ripples of wind-blown sediment on the dunes of Noctis Labyrinthus (the "labyrinth of the night") near the Martian equivalent of the Grand Canyon. The pretty blue color comes from the heavy dose of iron in the sand, which has been ground down over the years from volcanic rock.
[NASA]