Full Moon. Computer artwork of the full Moon on a starfield background rising above a blue and white limb of the Earth. The Moon is the only natural satellite of the Earth. It has a diameter of 3476km and lies at a mean distance of 384,000km from the Earth. Its rotation period around the Earth is equal to its period of revolution of 27.3 days. For this reason the Moon keeps the same face turned towards the Earth. The visible side has large dark areas called the lunar maria and craters caused by the impacts of falling meteoroids. The lunar maria are relatively empty of craters suggesting that these basins were filled recently by volcanic material.