Sean Rossman

USA TODAY

The formation of the moon wasn't the result of one massive cataclysmic clash of planets — rather, researchers say our moon formed when small "moonlets" came together.

That means the moon was formed over millions of years, not in an instant, said the scientific journal Nature Geoscience, which published a study on the revelation Monday. The prevailing belief has been that the moon was a piece of material that broke off when Earth slammed into something the size of Mars many moons - err, moonlets - ago.

But the research trio of Raluca Rufu, Oded Aharonson and Hagai B. Perets thought they'd follow-up on the big collision theory. They said the fact the moon's makeup is similar to Earth meant if a big clash did happen, the moon would have been formed either mostly from Earth or whatever collided with it. Both are possible, the journal said, but unlikely.

So the group ran a number of simulations of large, but not giant, bodies hitting Earth. They found the impacts produced small discs, which formed small moons or "moonlets." Those moonlets migrated outward and formed together to create what we know as the moon. The researchers said it would take "about 20" collisions to form the moon.

Gareth Collins, of Imperial College in London, said the study brought back "the hitherto largely discarded scenario that a series of smaller and more common impacts, rather than a single giant punch, formed the moon."

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