The Moon

The Moon (also known as Luna), is the Earth's only natural sattelite. The Moon doesn't have an atmosphere, due to it's small mass, although trace amounts of hydrogen, helium, argon and neon have been detected. The Moon's mass is approximately 3.34e22 kg (0.12 that of Earth).

The Moon's diameter is 3476 kilometers across and revlolves around the Earth at a distance of 406,676 kilometers.

A manned spacecraft first sucessfully landed on the moon in 1969. Since then many other spacecraft have landed on the moon (the Apollo spacecraft). Only 12 people have ever set foot on the moon.

In 1999 a probe called the Lunar Prospector discovered that on the Moon's south pole, there is evidence of water ice in some deep craters which are permenantly shaded. There is apparently water ice in the north pole as well.

The Moon's crust averages 68km thick and varies from 0 to 107km. Below the crust is a mantle and probably a small core.