Dunes on floor of Samara Valles

This shot, taken from the HiRise camera, shows one of Mars' longest systems of valleys, called the Samara Valles. The valley system covers more than 621 miles of the Martian surface.

The false-color images taken by HiRise use three color filters--red, infrared, and blue-green--so they do not appear as the human eye would see them, but are able to more clearly display surfaces details.