The surface of the Moon

The Moon is a rocky body, 3474 km in diameter, orbiting the Earth every 27.3 days at an average distance of 384 400 kilometres. Due to tidal locking, the Moon’s rotation period is also 27.3 days, so it always keeps the same face towards the Earth. The far side of the Moon had never been seen before the dawn of the Space Age. The Moon has no water, no air, and very little (if any) geological activity. As a result, surface markings like impact craters and Apollo astronaut boot prints remain unchanged for thousands of years. Twelve men have walked on the Moon, between 1969 and 1972.