All About Space: 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. Image Credit: NASA Thin, blade-like walls, some as tall as a 16-story building, dominate a previously undocumented network of intersecting ridges on Mars, found in images from NASA’s Mars Reconnaissance Orbiter. The simplest explanation for these impressive ridges is that lava flowed into pre-existing fractures in the ground and later resisted erosion better than material around them. A new survey of polygon-forming ridges on Mars examines this network in the Medusae Fossae region straddling the planet’s equator and similar-looking networks in other regions of the Red Planet. “Finding these ridges in the Medusae Fossae region set me on a quest to find all the types of polygonal ridges on Mars,” says Laura Kerber of NASA’s Jet Propulsion Laboratory, Pasadena, California. The pattern is sometimes called boxwork ridges. Raised lines intersect as the outlines of multiple adjoining rectangles, pentagons, triangles or other polygons. Despite the similarity in shape, these networks differ in origin and vary in scale from inches to miles. Mars rover missions have found small versions they have been able to inspect ...