The Plains are Not Plain
Jet Propulsion Laboratory https://www.jpl.nasa.gov/ June 1, 2016
This image covers some of the plains south of Capri Chasma in eastern Valles Marineris.
Where the aeolian (wind-blown) sedimentary cover has been stripped away, we see diverse colors indicative of of a variety of altered minerals formed in Mars' wetter past.
The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.