In a landmark study, an asteroid has been linked to an impact crater on the Moon which is believed to have created it.
The new analysis found that asteroid Kamo‘oalewa, a ‘quasi-moon’ that moves in and out of orbit around Earth, was probably hurled into space from the Giordano Bruno crater.
Kamo’oalewa has existed for several million years and is one of Earth’s co-orbital asteroids, which means it orbits the Sun on a similar path as Earth.
It measures between 150 and 190 feet in diameter and is due to be studied very soon, having been selected as the target of China’s Tianwen-2 mission.
Kamo‘oalewa lunar origins
Kamo‘oalewa is similar in appearance to lunar rock, which, along with its orbit, suggests it could have originated from the Moon.
To test this theory, the study simulated the impact needed to launch a space rock like Kamo‘oalewa into orbit and found the resulting lunar crater would be 10–20km wide and 10 million or so years old.
The four-million-year-old 22km-wide (14-mile) Giordano Bruno is the only lunar crater to fit those criteria.
“For 50 years, we have been studying rocks collected by astronauts on the surface of the Moon, as well as hundreds of small lunar meteorites that were ejected randomly by asteroid impacts from all over the Moon and ended up on Earth,” says Erik Asphaug from Arizona University, who worked on the study.
“Kamo‘oalewa is kind of a missing link that connects the two.”
Kamo‘oalewa and panspermia
What’s more, the event could have implications for what we know about the possibility for life to spread across the Galaxy.
Asphaug says the model shows how massive rocks might be thrown from the surface of a planetary body and survive intact
This links into the theory of panspermia, which demonstrates how life – or its ingredients – could be delivered to worlds from other regions across space.
:While Kamo’oalewa comes from a lifeless planet, it demonstrates how rocks ejected from Mars could carry life – at least in principle,” he says.
“The Giordano Bruno impact probably produced tens of hundreds of 10-meter-size ejecta fragments into space,” says lead study author Yifei Jiao, a visting scholar at the University of Arizona Lunar and Planetary Laboratory who is a doctoral student at Tsinghua University in Beijing.
“While most of that debris would have impacted the Earth as lunar meteorites over the course of less than a million years,” he said, “a few lucky objects can survive in heliocentric orbits as near-Earth asteroids, yet to be discovered or identified.”