large martian craters (greater than 60 kilometers in diameter) are named after famous scientists and science fiction authors; smaller ones (less than 60 km in diameter) get their names from towns on earth. craters cannot be named for living people, and small crater names are not intended to be commemorative – that is, a small crater isn't actually named after a specific town on earth, but rather its name comes at random from a pool of terrestrial place names, with some exceptions made for craters near landing sites. latitude and longitude are given as planetographic coordinates with west longitude.