A closer look at the Martian crater polygons shows cracks on both large and small size scales. The larger cracks are more than 100 metres long and up to 10 metres wide. Some of the craters may have hosted lakes billions of years ago when the Martian climate allowed liquid water to exist on the surface for extended periods. In other, much more recent craters, heat from the asteroid or comet impact that created the craters may have melted ice to create temporary lakes. (Image credit: NASA/ JPL)
Giant cracks that crisscross to form polygons have been imaged on the floors of hundreds of Martian impact craters by NASA’s Mars Reconnaissance Orbiter. Scientists have been aware of them for years, but assumed they resulted from the expansion and contraction of the craters’ floors due to temperature fluctuations.