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8 mysterious images of Mars

blue and white sand dunes

Photo: NASA/JPL/CalTech/University of Arizona

5 of 9

Proctor Crater

This is another snapshot from the HiRISE camera aboard the Mars Reconnaissance Orbiter. Taken on Feb. 9, 2009, this image shows dunes and ripples in the sand. Experts speculate that the dunes are composed of basaltic sand, which comes from volcanic rock, thus making them darker than the surrounding sand ripples.