This view shows part of an area on Mars where narrow rock ridges, some as tall as a 16-story building, intersect at angles forming corners of polygons.

The area covered in the image spans about two-thirds of a mile (1.1 kilometers) wide, in the Gordii Dorsum portion of the Medusae Fossae region of Mars. The image is from the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. North is up. Note the shadows cast by some of the walls.

A stereo view showing a larger portion of this network of polygonal ridges is at PIA21265.

These ridges likely formed as lava that hardened underground and later resisted erosion better than the surrounding material. From ground level, they would resemble hardened-lava walls on Earth such as in the image at PIA21266.

This image is a portion of HiRISE observation ESP_017348_1910, made on April 9, 2010, of a site at 10.8 degrees north latitude, 212.2 degrees east longitude.

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. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it.