Dark Patches Formed by Craters

In the ancient past, this area of Mars was bombarded by impactors, forming craters of various sizes in the light-toned material. Some time after that, a darker material blanketed and covered the field, filling in the craters. Eventually, that blanketed material itself became rock. Long after that, erosive forces (likely wind) acted in this area removing both dark and light-toned material, like an archeologist using a brush to reveal buried structures.

What we see today are a variety of dark circular features that are the remains of the layer that has been eroded back from the walls of the craters that formed them. In some cases, the crater rim is eroded and just a circular dark patch stands on a brighter exposure of rock.

Studying the thickness and characteristics of the dark layer might help scientists learn more about the processes that deposited the material, as well as those that eroded it.

The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. (The original image scale is 52.6 centimeters [20.7 inches] per pixel [with 2 x 2 binning]; objects on the order of 158 centimeters [62.2 inches] across are resolved.) North is up.

This is a stereo pair with ESP_071806_1570.

The University of Arizona, in Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., in 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.