Moon

Moon A Earth's only satellite and nearest neighbour in space, lying on average some 384,000 km (239,000 miles) away. With a diameter of only 3476 km (2160 miles) and a relative density of 3-3, it has a mass 1/81 that of the Earth. Its surface gravity is only one sixth that of the Earth. It is an airless and waterless world, which suffers extremes of temperature and where no life can exist.

The Moon had a captive rotation, which means that it keeps the same side facing towards us as it revolves around the Earth. Two main surface features are visible from the Earth-Dark plains called maria (seas) and rugged highland, which appear bright. The highland regions a heavily cratered. Between 1969 and 1972, 12 American Apollo astronauts explored the Moon on foot and returned with 385 kg of soil rocks and core samples that are still being analysed.

The Moon rocks are of two main types similar to basalts and breccias on Earth. They contain the same elements such as chromium, titanium and zirconium.