Tucson Standard

Scientists have, for the first time, traced an asteroid back to its exact origin—a specific crater on the moon. The asteroid, known as 2016 HO3 or Kamo'oalewa, is believed to have been ejected from the Giordano Bruno crater on the moon's far side. This discovery was published in the journal Nature Astronomy.

Kamo'oalewa is one of Earth's co-orbital asteroids, meaning it travels around the sun in a similar orbit as Earth. It measures between 150 and 190 feet in diameter, about half the size of the London Eye Ferris wheel.

Yifei Jiao, a visiting scholar at the University of Arizona Lunar and Planetary Laboratory and a doctoral student at Tsinghua University in Beijing, stated that this is "the first account of a potentially hazardous near-Earth asteroid that has been linked to a specific crater on the moon."

Previous research suggested Kamo'oalewa's lunar origin due to its reflectance spectrum and low orbital velocity relative to Earth. However, pinpointing its exact source remained elusive until now.

The research team used impact and dynamical modeling to trace Kamo'oalewa's origin. They concluded that an impactor of at least 1 kilometer in diameter would be required to launch such a fragment beyond the moon's gravitational pull. The resulting impact crater would need to be larger than 10 kilometers in diameter and younger than typical near-Earth objects' lifetimes.

The Giordano Bruno crater fits these criteria with its 14-mile diameter and estimated age of 4 million years. Erik Asphaug, co-author and professor at UArizona's Lunar and Planetary Laboratory, noted that many were skeptical about Kamo'oalewa originating from the moon but stated it serves as "a missing link" connecting lunar rocks collected by astronauts with small lunar meteorites found on Earth.

Renu Malhotra, co-author and UArizona planetary sciences professor, emphasized that these findings reveal new sources of near-Earth asteroids not previously studied. "Testing the new model of Kamo'oalewa's origin...paves the way for obtaining ground-truth knowledge," she said.

Asphaug explained that understanding how massive rocks can be ejected from planets intact could inform theories like panspermia—the idea that life might have spread across space via organic materials hitching rides on such rocks.

Jiao mentioned that while most debris from Giordano Bruno likely impacted Earth as lunar meteorites within a million years, some fragments survived as near-Earth asteroids yet to be discovered.

China’s Tianwen-2 mission aims to return samples from Kamo'oalewa to confirm its lunar origin further. NASA's NEO Surveyor mission is expected to identify more members of this lunar-derived population.

Asphaug highlighted sample return missions' importance: "They open up unsolved cases surrounding meteorite origins." He expressed optimism about Tianwen-2 bringing back samples different from any existing specimens: "It will be different in important ways...help you solve the puzzle."