Ridges near Nirgal Valles

In this observation from NASA's Mars Reconnaissance Orbiter (MRO), we see a set of straight ridges in ancient bedrock near Nirgal Valles. The patterns indicate fractures from tectonic stresses, but how have they been hardened to now stand in positive relief after billions of years of erosion?

It is possible that groundwater flowed through the fractures, depositing various durable minerals, some of which we see in diverse colors.

The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25.7 centimeters (10.1 inches) per pixel (with 1 x 1 binning); objects on the order of 77 centimeters (30.3 inches) across are resolved.] North is up.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.