NASA/Johns Hopkins APL/Carnegie Institution of Washington
Terrestrial planet
Mercury
Smallest planet.
Object typeTerrestrial planetDiameter4,879 kmMass0.055 Earth massesGravity3.7 m/s²Average temperature-180°C to 430°CDistance from the Sun57.9 million kmOrbital period88 Earth daysRotation period58.6 Earth daysNumber of moons0AtmosphereExtremely thin exosphereDiscoveryKnown since antiquity
