Their analysis seems convincing, says Andrew Rivkin, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory who studies the composition of asteroids and who was not involved in the paper. “Unless you go looking for a piece, like NASA just did it with Bennu, this is probably as close to a conclusion as we can get,” he says. Rivkin points out that Kamo’oalewa is an unusual object: of some 80,000 meteorites collected on Earth, only a few percent are from the Moon, and of the 1,382 meteorite falls observed and documented by humans, none were lunar .
Researchers find that Kamo’oalewa has likely existed for millions of years, not decades like other objects in such orbits. But its orbit is not stable, thanks to the classic three-body problemin which the chaotic gravitational influence of three bodies – the Earth, the sun and Kamo’oalewa – will eventually push it so that it is expelled and flies away.
Their astronomical research continues, including examining lunar craters that have remained virtually untouched for eons. Small changes in the models’ initial conditions, such as the size of the impacting asteroid, where it struck the moon, and the angle at which it struck, have dramatic effects on the trajectory of an ejected lunar rock. They deduce that a kilometer-sized asteroid caused this critical accident, and they can also make inferences about the impact. “Based on the likely conditions to produce this type of orbit, coming from the Moon, it would require a crater that is millions of years old and tens of kilometers in size,” says Castro-Cisneros. It probably crashed into the back side of the Moon, he says, and they are now trying to identify the precise crater from which Kamo’oalewa was launched.
Kamo’oalewa’s lunar provenance also has implications for potentially dangerous Earth-bound asteroids that NASA And other organizations search the heavens. This means people should also consider orbits originating from the moon, not just rocks thrown out of the asteroid belt. NASA searches for asteroids 140 meters in diameter and larger, similar in size to that of DART spacecraft collided to test deflection techniques. Near-Earth objects from ancient lunar impacts would likely measure 100 meters or less, Malhotra says, but they are nonetheless known as “city killers“, dangerous enough to cause widespread destruction if they were to strike Earth.
This probably won’t be Kamo’oalewa’s fate, but Malhotra and Castro-Cisneros’ research shows there are likely others like it out there.