Researchers from the Technion-Weizmann Institute of Technology have proposed a theory suggesting that our current Moon may be the latest in a long line of moons that orbited Earth in the past, each created by an impact from giant asteroids.
“Our model suggests that the ancient Earth once hosted a series of moons, each one formed from a different collision with the proto-Earth,” said researcher Hagai Perets. “It’s likely that such moonlets were later ejected, or collided with Earth or each other to form bigger moons. We believe Earth had many previous moons. A previously formed moon could therefore already exist when another moon-forming giant impact occurs.”
The team ran almost 1,000 computer simulations of different scenarios of objects striking Earth, and found it would take around 20 collisions to get the job done. According to this model, the Earth experienced many giant impacts with other bodies during the last stages of its growth, with each contributing more material to the proto-moon until it reached its current size.
“It’s likely that small moons formed through the process could cross orbits, collide and merge,” said researcher Raluca Rufo. “A long series of such moon-moon collisions could gradually build up a bigger moon – the Moon we see today.”