The moon spent a few million years as a volcanic wasteland, covered with ongoing eruptions that spewed from mountains and even from the ground itself. New research suggests that the moon's orbit could have turned it into a molten monster for a few tens of millions of years. The result may have been comparable to Jupiter's moon Io, the most volcanic body in the solar system.
Early in the history of the solar system, a massive protoplanet plowed into a young Earth. The colliding material intermixed, then reformed into two separate bodies that would become Earth and the moon. The two orbited almost on top of one another, but over time, the moon slowly drifted away, solidifying as it went.
