NASA’s Curiosity Mars rover has discovered sandstone formations that shows texture and inclined bedding structures characteristic of deposits that formed as sand dunes, then became rock.
This outcrop pictured above is part of a geological layer that Curiosity’s science team calls the Stimson unit. It has a structure called crossbedding on a large scale that the team has interpreted as deposits of sand dunes formed by wind.
Similar-looking petrified sand dunes are common in the Southwest of the United States.
Beneath the Stimson unit is a layer of mudstone that was deposited in a lake environment.
An even higher resolution image can be found at http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19818