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.
We have observed in detail less than half of Mercury's surface.
Mercury is the closest planet to the Sun.
Mercury rotates the Sun in only 88 days.
Mercury rotates very slowly on its axis with one day taking 58 Earth days.
Mean distance from Sun is 57,910,000 km/35,980,000 mi.
Mercury barely has any atmosphere, but does have glaciers.
Mercury is named after the Roman messenger of the gods.
On average, Mercury is 36 million miles from the Sun.
During the day, the average temperature on Mercury is 800 degrees Fahrenheit.
During the night, the average temperature is – 300 degrees.
Mercury is 38 percent of the diameter of the Earth.
Mercury has no moons.
Small in diameter, Mercury is the second largest planet when measured by mass.
Mercury is primarily comprised of iron, which accounts for its heavy mass.
Mercury has the largest known impact crater of any planet, named Beethoven and 643 kilometers in size.
Mercury has an eccentric orbit around the Sun, meaning it is closer and farther from the Sun at different points in time.
At its closest orbit, Mercury is “only” 46 million kilometers from the sun.
At its farthest orbit, Mercury is 70 million miles from the Sun.
In 2011, the spacecraft Messenger will arrive at Mercury to study it.
Messenger was launched in 2004.
Mercury can be seen with binoculars at sunset.
Like Earth, Mercury has a magnetic field.
The magnetic field of Mercury is only one percent as strong as ours.