|Mercury in enhanced color from MESSENGER.|
|Diameter|| 4,880 km|
|Size||Ranked 8th in the Solar System|
The Romans named the planet after the swift-footed Roman messenger god, Mercury (Latin Mercurius), which they equated with the Greek Hermes, because it moves across the sky faster than any other planet.
The orbit of Mercury is the most eccentric of the planets in our Solar System. The planet has an orbital period of 87.969 Earth days.
The surface of Mercury is marred by an impressive number of craters. The cratering is deeper than on most terrestrial planets because of its lack of an atmosphere. A thicker atmosphere would have slowed impacting bodies, making the craters more shallow.
Two spacecraft have visited Mercury: Mariner 10 flew by in 1974 and 1975; and MESSENGER, launched in 2004, orbited Mercury over 4,000 times in four years, before exhausting its fuel and crashing into the planet's surface on April 30, 2015.