This image from HiRISE (High Resolution Imaging Science Experiment) camera on board the Mars Reconnaissance Orbiter, shows knobs and bluffs that are being actively eroded in Pasteur Crater by the Martian wind.
Fine, light-toned sedimentary layering is exposed in the bedrock at the base of the cliffs.
Also in this scene are two types of unconsolidated aeolian sediments. The reddish ridges are relatively immobile, and are probably similar to granule ripples on Earth that are protected from the winds by a surface layer of coarse grains.
The dark gray dunes are probably made up of fine (approximately 0.1 mm) basaltic sand.
credit: NASA/JPL/University of Arizona