In 2021, a team of University of Arizona astronomers suggested that a recently discovered near-Earth asteroid, Kamo`oalewa, could be a chunk of the moon. Two years after the striking discovery, another UArizona research group has found that a rare pathway could have enabled this to happen.
So far, only distant asteroids from beyond the orbit of Mars have been considered a source of near-Earth asteroids, said Renu Malhotra, Regents Professor of Planetary Sciences and a senior author on the paper.
“We are now establishing that the moon is a more likely source of Kamo`oalewa,” Malhotra said.
The implication is that many more lunar fragments remain to be discovered among the near-Earth asteroid population. The study was published in the journal Communications Earth & Environment.
UArizona researchers decided to study Kamo`oalewa for two reasons. Kamo`oalewa is uncommon in that it is Earth’s quasi-satellite, a term used for asteroids whose orbits are so Earth-like that they appear to orbit Earth even though they actually orbit the sun.
The other peculiar aspect of Kamo`oalewa is its longevity, said Jose Daniel Castro-Cisneros, the study’s lead author and a graduate student in the Department of Physics. Kamo`oalewa is expected to remain as a companion of the Earth for millions of years, which is its remarkable feature, Castro-Cisneros said, unlike other known objects that stay in these very Earth-like orbits only for a few decades.
Aaron Rosengren, a former assistant professor in the Department of Aerospace and Mechanical Engineering, in the College of Engineering, was part of the study. Rosengren is now at the University of California, San Diego.
The 2021 study found that Kamo`oalewa’s spectrum was unlike that of other near-Earth asteroids but matched most closely that of the moon. Based on this, the team hypothesized that the asteroid could have been ejected from the lunar surface as a result of a meteoroidal impact.
In the new study, Malhotra…