Earth and Moon. Artwork of the Moon rising above a limb of the Earth, on a starfield. The Moon is the Earths only natural satellite. Its rotation period around the Earth is equal to its period of revolution (27. 3 days). For this reason the Moon always keeps the same face turned towards the Earth. The visible side of the Moon is marked with dark areas called the lunar maria (or seas) and craters caused by meteorite impacts.
