This closeup of High Dune was taken by MAHLI, the camera on the end of Curiosity's arm, on sol 1184 (December 6, 2015). Unlike previously investigated sand ripples, this active dune lacks fine sand and dust; the field of view is filled with sand grains of nearly uniform size of roughly 0.5 millimeters. However, the grains have a wide variety of color.
This image is in the public domain.
Original image data dated on or about December 6, 2015