The Earth's one natural satellite, the Moon, is more than one quarter the size of Earth itself (3,474 km diameter), making the Earth-Moon system virtually a double-planet. Because of its smaller size, the Moon's gravity is one-sixth of the Earth's gravity (ie. A person who weighs 60 kg on the earth would weigh just 10 kg on the moon).
While there are only two basic types of regions on the Moon's surface, there are many interesting surface features such as craters, mountain ranges, rilles, and lava plains. The structure of the Moon's interior is more difficult to study. The Moon's crust,the top layer, is a rocky solid. Below the crust is the mantle which consists of a denser rock. Together, the crust and mantle form the Moon's lithosphere, which is very thick (perhaps 800 km) compared to the Earth's lithosphere. Beneath the lithosphere is a partially molten zone.
Photograph of Moon's Surface
The footprints left by Apollo astronauts will last for centuries because there is no wind on the Moon. The Moon does not possess any atmosphere, so there is no weather as we are used to on Earth.
A footprint on the moon made by Apollo 11 commander Neil Armstrong on July 20, 1969.
Because there is no atmosphere to trap heat, the temperatures on the Moon vary drastically over the course of a day, from 100 C at noon to -173 C at night.