Smaller moons came together to form Earth’s moon
The leading theory for the moon’s origin argues that an astronomical body the size of Mars collided with Earth, and the ensuing debris caught in its gravitational field eventually merged into our moon
The Earth’s moon was not created in one colossal impact, as commonly believed, but instead is a fusion of several “moonlets” created in smaller collisions, researchers argued recently in the Nature Geoscience journal.
The leading theory for the moon’s origin argues that an astronomical body the size of Mars collided with Earth, and the ensuing debris caught in its gravitational field eventually merged into our moon.
However, because chemical analyses of the moon’s surface lack evidence of such an astronomical body, and highly specific conditions are needed for that theory to work, the scientists considered other scenarios.
The study at the Weizmann Institute of Science in Rehovot, south of Tel Aviv, instead suggests that a series of smaller collisions created “moonlets” that were drawn into the same orbit and merged together over millions of years.
They theorised that smaller astronomical bodies would have been more common in the Solar System at the time, and therefore more likely to collide with early Earth, sending clouds of debris into its orbit that eventually would cool into the moonlets. The researchers came to their conclusion after running some 800 impact simulations.
Unlike the single-impact theory, the multiple-impact theory does not require fine-tuned conditions and fits better with compositional analyses of the moon, the researchers said in a statement.
“We are now running further simulations to try to understand how the smaller moonlets produced in these simulations might have coalesced to form our moon,” said Oded Aharonson, a professor at the institute. — dpa