The craters on the Moon are due to impacts rather than to say, volcanism despite the fact that the craters are, for the most part, circular in shape. A compelling argument against volcansim is that the craters are all below ground . That is, crater formation is more like a bomb exploding rather than something simply diggin out a trench or a hole.
Comments Note, however, that rays can show the direction from which the objects appraoched.
The centers of some craters show raised mounds in their centers.