The Moon over Earth – extremes of planetary evolution
The Moon over Earth – extremes of planetary evolution
The Moon has been orbiting Earth for almost four-and-a-half billion years. The two bodies represent two extremes of planetary evolution. The Moon was formed 4.425 billion years ago from material ejected from Earth during a massive collision with a protoplanet. It subsequently developed a magma ocean more than 1000 kilometres deep on which a crust formed. Beneath the crust, the mantle rock solidified over the course of 200 million years. Earth also had a magma ocean, but did not form a floating crust. Once the Moon had solidified, magma formed in its interior and rose to the surface. However, volcanic activity came to a halt three billion years ago and the face of the Moon has hardly changed since then.
