Circular Sand Dunes

Sand dunes of many shapes and sizes are common on Mars. In this example, the dunes are almost perfectly circular, which is unusual.

They are still slightly asymmetrical, with steep slip faces on the south ends. This indicates that sand generally moves to the south, but the winds may be variable.

This is part of a series of images to monitor how frost disappears in the late winter; this observation appears to be free of frost. A previous image shows when the surface was covered by frost.

The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. (The original image scale is 30.3 centimeters [11.9 inches] per pixel [with 1 x 1 binning]; objects on the order of 91 centimeters [35.8 inches] across are resolved.) North is up.

The University of Arizona, in Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.