HRSC: Chaos in Atlantis basin

Mars is peppered with craters. Scientists have deduced that the red planet is struck by around 200 meteoroids every year that dig out new craters. While some small craters are fresh, Mars has a great many that are much larger and more ancient, such as the roughly circular patch of terrain, partially encircled by wrinkled cliffs, shown at the centre of this image. Named Atlantis basin, this crater is so old that its outer rim has eroded and is now barely detectable…. [More at link]