Object typeNatural satelliteDiameter3,475 kmMass0.0123 Earth massesGravity1.62 m/s²Average temperature-173°C to 127°CDistance from the SunOrbits EarthOrbital period27.3 daysRotation period27.3 daysNumber of moons0AtmosphereVery thin exosphereDiscoveryKnown since prehistory