An asteroid on an unusual orbit may once have been part of the Moon
An unusual near-Earth asteroid could once have been part of the Moon, according to a new study.
Kamo‘oalewa is a quasi-Earth satellite, meaning it appears to orbit the Earth but is actually orbiting the Sun. Such orbits are rare and generally only last a few decades, but Kamo‘oalewa will remain stable for millions of years. The unusual orbit led astronomers to take a spectra of the rock, finding its composition was more like that of the Moon than an asteroid.
A team of planetary geologists wondered if the asteroid was a lunar fragment chipped off by a meteor. They created a set of computer simulations that showed it was rare, but possible, for an impact to have enough energy to put an asteroid into a quasi-satellite orbit without ejecting it from the Earth–Moon system entirely.
“We looked at Kamo‘oalewa’s spectrum only because it was in an unusual orbit,” says Renu Malhotra from the University of Arizona, who led the study. “If it had been a typical near-Earth asteroid, no one would have thought to find its spectrum and we wouldn’t have known Kamo‘oalewa could be a lunar fragment.”
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