There are over 27,000 near-Earth objects in our solar system, most of which came from the inner solar system between Mars and Jupiter. However, researchers say one near-Earth asteroid didn’t come from either planet, but perhaps is a piece of our moon.
The near-Earth asteroid Kamo`oalewa, a name that comes from Hawaiian chants alluding to “an offspring that travels on its own,” is known as a quasi-satellite, meaning it orbits the sun but gets close to Earth.
It was discovered in 2016 in Hawaii, and it can only be observed every few weeks in April. It’s about the size of a Ferris wheel, as astronomers estimate it is 150-190 feet in diameter and gets as close as roughly 9 million miles from Earth. That may seem like a significant size, but it can only be detected using some of the largest telescopes on Earth.
But when studying Kamo`oalewa in southern Arizona, University of Arizona astronomers noticed something unusual about it: how it reflected light and matched lunar rocks taken from NASA’s Apollo missions. Astronomers were led to believe the asteroid may have come from the moon, but they are unsure how something could have broken off of it.
“I looked through every near-Earth asteroid spectrum we had access to, and nothing matched,” Ben Sharkey, a graduate student at the university, said in a statement.
Sharkey and Vishnu Reddy, his advisor and associate professor of lunar and planetary sciences at Arizona, then began to debate if the asteroid did come from the moon and studied it for over three years.
“We doubted ourselves to death,” Reddy said.
After missing the chance to observe it in 2020 due to the COVID-19 pandemic, the team was able to see Kamo`oalewa this year, and the results seemed to fit the bill. Their findings were published in the journal Nature Communications Earth and Environment on Thursday.
“This spring, we got much-needed follow-up observations and went, ‘Wow it is real,'” Sharkey said. “It’s easier to explain with the moon than other ideas.”
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Another clue that gave Sharkey and his team the assumption was that Kamo’oalewa’s orbit around the Sun is similar to Earth’s, but it just has more of a tilt.
Renu Malhotra, study co-author and Arizona planetary sciences professor, said it’s not typical for asteroids to have this orbit, and it had been in this orbit for around 500 years.
As for how the asteroid broke off, astronomers are still trying to determine what may have caused it. Theories the team have tossed around is that Kamo’oalewa is a product of an ancient asteroid impact or that it was captured in its orbit from other near-Earth objects.
Follow Jordan Mendoza on Twitter: @jordan_mendoza5.