New Study Challenges the Lunar-Origin Theory of Kamo'oalewa as China's Tianwen-2 Probe Nears the Quasi-Moon Asteroid
A Nature Communications study argues Kamo'oalewa likely came from the Flora asteroid family, not the Moon, weeks before Tianwen-2 reaches its target.
Overview
A new study published in Nature Communications challenges the leading theory about the origin of Kamo’oalewa, the small asteroid that China’s Tianwen-2 spacecraft is on its way to sample. According to Phys.org, the research argues that the object is more likely a fragment of a main-belt asteroid than a piece of the Moon, a reinterpretation that arrives as the probe closes in on its target.
Kamo’oalewa is a small quasi-satellite that orbits the Sun on a path keeping it close to Earth, as Phys.org describes it. Space.com notes it is one of Earth’s seven known “quasi moons,” circling the Sun on a path that keeps it near our planet.
What We Know
The study, led by Yang Li, a planetary scientist at the Chinese Academy of Sciences, was published in Nature Communications, according to Phys.org. To test the asteroid’s composition, the researchers took an LL chondrite meteorite that had fallen to Earth, ground it into a powder, and blasted it with lasers to simulate millions of years of space weathering from micrometeoroid impacts and solar wind, Phys.org reports. They found a characteristic dip in the light spectrum more commonly associated with an LL chondrite than with lunar rock, the same report notes.
The preprint of the work, titled “Tianwen-2 target asteroid (469219) Kamo’oalewa probably develops an Itokawa-compositional but ultra-highly space-weathered surface,” reports an absorption band center at 1.001 micrometers, consistent with LL chondrites. The authors also state that highly space-weathered LL chondrite powder, but not slab, successfully reproduced the reflectance spectrum of Kamo’oalewa, per the arXiv preprint. Tracing the asteroid’s dynamical history, the authors found that it probably originated from the v6 secular resonance, and more specifically, the Flora family.
Summarizing the conclusion, the team wrote that “Kamo’oalewa probably originated from the Flora family and developed an Itokawa-compositional, more space-weathered, fine-regolith-dominated surface,” as quoted by Phys.org.
The earlier hypothesis held that the asteroid may have been created when an ancient impact on the Moon blasted a fragment into space, Phys.org notes. Space.com similarly described it as possibly a chunk of the Moon blasted out by a giant impact.
The Mission
Tianwen-2 lifted off atop a Long March 3B rocket from the Xichang Satellite Launch Center in southwestern China on May 28, according to Space.com. The spacecraft left Earth in May 2025 and should return in late 2027 with samples, Phys.org reports. The probe is expected to reach Kamo’oalewa in July of 2026.
Once there, the spacecraft will study the asteroid using cameras, spectrometers, a magnetometer, and a dust analyzer before selecting a sampling site, Space.com reports. It then aims to collect about 100 grams of material using two different methods, “touch and go” and “anchor and attach,” the same report states. The anchor-and-attach approach, which requires one or more drills, has never been tried before, while touch and go is well established, according to Space.com.
Tianwen-2 is set to depart Kamo’oalewa in April 2027, with a capsule carrying the samples landing on Earth about seven months later, Space.com reports. After delivering the samples, the spacecraft will use Earth’s gravity for a slingshot maneuver to set a course for the main-belt comet 311P/PANSTARRS around 2035.
The Target
Kamo’oalewa, also known as 2016 HO3, is a near-Earth asteroid discovered in 2016 that is between 40 and 100 meters wide, Space.com reports. The fast-spinning object completes a rotation roughly every 28 minutes, according to Phys.org. The mission aims to provide data on the nature and composition of such bodies, as well as insights into questions such as the evolution of the solar system and the origin of water on Earth, Space.com notes.
What We Don’t Know
The new analysis does not settle the question definitively. The researchers do not completely close the door on a lunar composition, Phys.org reports. A returned sample would offer the most direct test of the competing origin scenarios, which is why the spectral debate matters now: Tianwen-2’s planned collection would put physical material from Kamo’oalewa into laboratories for the first time, potentially resolving whether the asteroid is lunar debris or a far-traveled fragment of the Flora family.
Analysis
The timing underscores how much remains uncertain about even the best-studied near-Earth objects. Kamo’oalewa has been a leading candidate for lunar origin for years, a hypothesis that made it an especially intriguing sample-return target. If the Flora-family interpretation holds, the mission’s scientific payoff shifts from confirming a lunar fragment to characterizing a heavily space-weathered main-belt refugee, a distinction that bears on how scientists read the surfaces of small bodies across the solar system.