The Moon is too small to hold onto any air. Without any winds, the sunny side is hotter than boiling water, but the night side is colder than anywhere on Earth (minus 180 degrees Celsius).
Much of what we know about the Moon came from robotic orbiters and landers during the 1960s and 1970s. Some scientists thought that a spacecraft landing on the Moon would sink into its dusty surface. This was shown to be wrong by American and Russian landers. They cleared the way for humans to visit the Moon.
Twelve men walked on the near side of the Moon between 1969 and 1972. They left scientific experiments on the surface. They also came back with nearly 400 kg of rocks and soil. On the later missions, the astronauts drove around the Moon in a battery-powered rover.
In recent years, many countries have decided to go back to the Moon. Orbiting spacecraft have explored the entire surface in great detail. One major discovery was the presence of water ice at the bottom of craters near the lunar poles. Shaded from the Sun's rays, the ice may have been there for millions of years. This could be used by future explorers to make oxygen and to drink.
Europe's first lunar spacecraft was SMART-1, which orbited the Moon between November 2004 and September 2006. SMART-1 took detailed images of the surface and studied what the rocks are made of. The mission ended with a deliberate crash into the lunar surface.
Last modified 17 November 2010