Image courtesy of NASA / JPL-Caltec

The Earth's one natural satellite, the Moon, is more than one quarter the size of Earth and orbits the Earth at a distance of about 384.000 km. The Moon is thought to have formed nearly 4.5 billion years ago.

Because of its smaller size, the Moon's gravity is one-sixth of the Earth's gravity. The moon makes a complete orbit around Earth in 27 Earth days and rotates or spins at that same rate. The Moon has many interesting surface features such as craters, mountain ranges, rilles, and lava plains. The moon has a very thin and weak atmosphere, called an exosphere.

The light areas of the moon are known as the highlands. The dark features, called maria (Latin for seas), are impact basins that were filled with lava between 4.2 and 1.2 billion years ago.



Radius: 1.734 km

Density: 3,344 g/cm3

Gravity: 1,624 m/s2

From Sun: 1.00 AU

Lenght of day: 27,322 Earth days

Lenght of year: 27,322 Earth days

Surface temperature: -223 to +123

Core temperature: 1600 - 1700 K

Composition: Silicates and iron