FACTS:
Satellites: 0 moons
- Mercury has been known since at least the time of the Sumerians (3rd millennium BC).
- Mercury was given two names by the Greeks: Apollo at sunrise and Hermes at sunset.
- Mercury has been visited by two spacecraft, Mariner 10 in 1974/1975 and the MESSENGER spacecraft in 2008. Together they have only mapped about 75% of Mercury's surface.
- Mercury is in many ways similar to the Moon: its surface is heavily cratered and very old; it has no plate tectonics. On the other hand, Mercury is much denser than the Moon.
MERCURY
INFORMATION:
- MASS: ≈ 3.3022×1023 kg (About 1/3 the size of Earth!)
- DIAMETER: ≈ 3,031 miles
- TEMPERATURE: ≈ 800° F (surface)