When astronauts brought back rock samples from the Moon, the minerals present were mostly the same as those found on Earth. Can you think of reasons why this might be so? Would you expect minerals on Mars or Venus to be the same, or at least very similar, to those on Earth?

Question

anonymous · Answer

The similarity suggests that the Moon and Earth were once part of the same planet. Some enormous event led to the splitting off of the Moon which cooled to give the satellite we know today. The other planets are probably different because they arose separately.