There are various theories about how the moon was created, but recent evidence indicates it formed when a huge collision tore a chunk of Earth away.
The leading explanation for how the moon formed was that a giant impact knocked off the raw ingredients for the moon off the primitive molten Earth and into orbit. Scientists have suggested the impactor was roughly 10 percent the mass of Earth, about the size of Mars. Because Earth and the moon are so similar in composition, researchers have concluded that the impact must have occurred about 95 million years after the formation of the solar system, give or take 32 million years. (The solar system is roughly 4.6 billion years old.)
Although the large impact theory dominates the scientific community’s discussion, another theory suggests that two young moons couldhave collided to form a single large one. Earth may even have stolen the moon from Venus, according to a recent theory.