Mean distance from Sun: 0.3871 AU
(57,910,000 km/35,980,000 mi) Diameter:
4,878 km (3,031 mi)
Length of year:
Rotation period: 58.65 days Mean orbital velocity:
48 km/s (30 mi/s)
Inclination of axis:
2° Average temperature: 800° F (427° C) day
-300° F (-183° C) night Number of observed satellites:
Comparisons with Earth Mean distance from Sun: 0.387 x Earth's Diameter: 0.38 x Earth's Mass: 0.055 x Earth's Density: Slightly less than Earth's
Mercury is one of the five planets known to the ancients. They called these planets "wandering stars."
Mercury may be seen as an evening "star" near where the sun has set, or as a morning "star" near where the sun will rise.
The ancient Greeks called the evening star Hermes and the morning star Apollo, believing them to be different objects.
The planet is named for Mercury, the Roman messenger of the gods.
To the Teutonic peoples, the planet was named for their god Woden. Wednesday (wodnesdaeg in anglo-saxon) is named for him.
Mercury's atmosphere is so thin that it is barely detectable.