Where did Earth ’s oddball ‘quasi-moon’ come from? Scientists pinpoint famed lunar crater

Astronomers suspect an unusual near-Earth rocky object is not a typical escapee from the Solar System’s asteroid belt, but is instead a chunk of the Moon blasted into space eons ago by a spectacular impact. Now, a team of researchers has modeled what sort of lunar impact could have ejected such a gobbet of Moon and deposit it in a stable, nearby orbit. Surprisingly, only one strong candidate emerged: the asteroid strike that created the famous Giordano Bruno crater, the youngest large crater on the Moon, the group reports today in Nature Astronomy . “The authors’ modeling techniques are solid and well established,” says geophysicist Ronald Ballouz of Johns Hopkins University. “They are able to show that ejecta from a crater the size of the Giordano Bruno … could survive for a long enough timescale in a co-orbital zone around Earth.” The odd asteroid, known as 469219 Kamo‘oalewa, was discovered in 2016 by Pan-STARRS, a telescope system in Hawaii designed to identify potentially threatening space rocks. Kamo‘oalewa measures between 40 and 100 meters across and rotates particularly fast—once every 28 minutes. It follows an elliptical orbit around the Sun that moves in sync with Earth, giving the impression that the asteroid orbits Earth, even though it is outside the planet’s gravitational influence. The asteroid’s curious orbit and small size led to it being chosen as the first target for China’s sample return mission Ti...
Source: ScienceNOW - Category: Science Source Type: news