The Moon

Mean distance from Earth: 384,400 km
Diameter: 3,476 km
Mass: 0.0123 Earths
Density: 3.34 grams per cubic centimeter
Surface temperature: 248 F to -274 F
Orbital period (Synodic): 29.53 days
Rotational period: 27.3 days

The Earth and Moon form a double-planet system. The Moon is the closest astronomical body to the Earth and we know more about it than any other object in the heavens. Many surface features are visible to the unaided eye, and a pair of binoculars reveals a great amount of detail. A small telescope shows vast seas of lava, large mountain ranges and hundreds of craters of all sizes. Studies of the 382 kg of lunar rock and soil brought back by the Apollo missions have revealed much about the early history of both the Moon and the Earth.