Dark-colored sand dunes mark the terrain on Chasma Boreale, a trough that cuts into the north polar ice fields of Mars. These are known as barchan dunes…like their counterparts on Earth, they have steep edges with “horns” that point in the direction of the wind.

The dune material could either be dark sand or volcanic ash.

This photo, taken September 26, 2008, was taken by the HiRISE camera on the MRO. Click image for a high-resolution version.

Image credit: NASA/JPL/University of Arizona