Blade-Like Martian Walls Outline Polygons (Stereo)

This stereo 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. It appears three-dimensional when viewed through red-blue glasses with the red lens on the left. The area covered in the image is about 1.9 miles (3 kilometers) wide, in the Gordii Dorsum portion of the Medusae Fossae region of Mars. This stereo view combines two observations from the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter.. North is up. Note the afternoon shadows cast by some of the walls. 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. http://photojournal.jpl.nasa.gov/catalog/PIA21265