Crater

Craters are large holes on the surface of astral bodies, caused by collisions with other astral bodies, due to the effects of gravity. The vast majority of craters are round because of the speed of these impacts, which are usually so fast that everything melts for a few moments when it hits. A small number of craters, less than 1 in 10, are elongated, because of a very low angle of impact. We know this because many people have done experiments about this and have created big machines to make scale models and computer models of impacts.