Researchers suggest new theory for moon's origin
A series of cosmic collisions may have formed multiple tiny moons that combined to create the bigger moon we see today.
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According to the existing hypothesis, the moon has formed some 4.5 billion years ago after a catastrophe collision between Earth and a Mars-sized planet. The giant impact left a large amount of debris floating in the space that eventually clumped together and created the moon.
In such a scenario, researchers expect that the moon would have made mainly from the remnants of the impacting body, not from the pieces of Earth. However, a previous analysis of lunar rocks suggests that moon's chemical composition is almost similar to Earth and it is likely made up of the same material as Earth’s mantle.
In order to close this theoretical loophole, researchers have provided another explanation about moon’s origin. Rather than one giant impact, a number of smaller collisions may have formed the Earth's moon.
“The multiple impact scenario is a more 'natural' way of explaining the formation of the Moon," said co-author of the study Raluca Rufu from the Weizmann Institute of Science, Israel.
To understand the scenarios, researchers ran nearly a thousand of computer simulations of collisions between Earth and a forming planet. Every collision would have formed a disk of debris which slowly clumped together to create moonlets or mini-moons. These mini-moons eventually gathered themselves to create a single, big moon.
Each of these collisions added more material and mini-moons to the proto-Earth, until it reached its current size. Researchers estimate that about 20 crashes would have been required to build the Moon, contradicting the giant-impact theory that says that moon is the result of a single catastorphe evetn. The theory has been widely accepted for many decades.
“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 co-author Hagai Perets of the Technion, Israel Institute of Technology in Haifa. "It's likely that such moonlets were later ejected, or collided with Earth or with each other to form bigger moons."