Craters

The Moon is covered with craters. Other bodies in the Solar System are also covered with craters. If you look at an unlabeled photograph of Mercury, it is likely that you would simply assume it was the Moon because the cratering is so similar. Such craters have only been discovered since the advent of spacecraft to view the planets close up, so it was not until 1965, when the Mariner 4 craft flew by Mars, that craters other than on Earth or Moon were seen. Image: Far Side of the Moon, Public Domain (NASA).