The Moon is an astronomical body orbiting Earth and is the planet's only natural satellite. It is the fifth-largest satellite in the Solar System, and by far the largest among planetary satellites relative to the size of the planet that it orbits. Surface gravity : 1.622 m/s² (0.165 4 g) Surface pressure : 2.25 × 10-12 torr Surface area : 3.793 × 107 km² (0.074 Earths) Satellite of: Earth