Lunar Origin

The recent revival of interest in lunar origin is remarkable since it does not arise from an infusion of new data but mainly from an enthusiasm for some relatively new ideas that are still largely untested. Catastrophism is now in fashion: the origin theory currently favored by many involves a giant impact on Earth by a body of about the mass of Mars or more, with the moon forming from the resulting splash of molten and vaporized rock. The whole process may have taken only a hundred years and would have been fun to watch in real time.