Terra Meridiani (possible True Colors; credits: Dr Paolo C. Fienga - Lnexit Team)

This HiRISE image shows dark sand covering bright Bedrock in the Terra Meridiani (Meridiani Planum) Region of Mars.
The MER Opportunity Rover is currently exploring Meridiani, but is located about 500 Km to the West-South/West from this area.

There are three broad classes of Terrain in this image: the regular spacing of the Dark Ridges, with one side of the Ridges (in this case generally facing North/West) shallower than the other, indicates that the material is windblown sand deposited in the form of Dunes or large Ripples. On the slopes of and in between the Dunes and Ripples are smaller-scale Ripples.

The dark orangish tone of the Sand and the analysis of analogous material by Opportunity indicates that is composition might be Basaltic and this is in contrast to most sand on Earth, which is dominated by Quartz.