A new type of dune, called  “wind-drag ripples,” found last year by the Curiosity rover in Gale Crater. The dune is a part of the  Bagnold Dune Field, on the the northwestern flank of Mount Sharp. The images were taken in early morning, with the camera looking in the direction of the sun. This mosaic combining the images has been processed to brighten it and make the ripples more visible. The sand is very dark, both from the morning shadows and from the intrinsic darkness of the basaltic minerals that dominate its composition. The base of Mount Sharp can be seen beyond the dunes.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/29050464@N06">Peter D. Tillman</a>, my crop and a bit of reprocessing
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/29050464@N06/31685589574/">Namib dune, Gale Crater</a>, which links to the original NASA-JPL source image, and a couple of discussions of the dunes.