Earth’s only natural satellite is the Moon. It is thought to be as old as Earth, about
4.6 billion years. The Moon is made of rock with a core, a mantle that is partially
molten, and a crust with craters created by meteorite hits. Basins and cratered
highlands also exist on the surface. A soil called regolith covers the surface of
the Moon, made of fragmented rock and dust. From Earth, highlands appear
bright and craters appear dark. The same side of the Moon is always visible
from Earth, as it rotates and revolves at the same rate. The Moon has no free
water and practically no atmosphere, so there is no weather on the Moon.
It was first visited by a spacecraft in 1959 and has been visited many times
since. It is the only extraterrestrial body that humans have visited.