Tenoumer Crater, Mauritania, satellite image. North is at top. The crater, located in a region of the Sahara, is surrounded by desert sands and rocks. It formed following the impact of a meteorite. It is 1.9 kilometres in diameter and is estimated to be 2.5 million years old. The desert conditions in this region of the Sahara have helped to preserve the crater and reduce the rate of erosion. Image data obtained on 21 March 1988.