China's Tianwen-2 Reaches the Quasi-Moon Kamo'oalewa, Opening a Months-Long Survey Before a First-of-Its-Kind Sampling Attempt
After a year in transit, Tianwen-2 has rendezvoused with the tiny near-Earth asteroid and will map it before attempting to collect a sample for return to Earth.
Editor's Note ·
- Clarification:
- The article presents "an asteroid on Kamo'oalewa's orbit is '10 times more likely to have originated from the inner main asteroid belt than from the moon,' Mikael Granvik told Scientific American." Scientific American does not quote Granvik saying this directly; it describes the figure as a result of his statistical models ("Granvik's statistical models of the near-Earth object population suggest..."). The quoted figure is accurate, but it is the publication's paraphrase of Granvik's modeling rather than a direct utterance.
- Correction:
- The article quotes the recent study as concluding Kamo'oalewa "developed an Itokawa-compositional, more space-weathered surface." The source (Phys.org) reads "...more space-weathered, fine-regolith-dominated surface." The clause "fine-regolith-dominated" was omitted from inside the quotation marks without an ellipsis; the meaning is unchanged.
Overview
China’s Tianwen-2 spacecraft has reached Kamo’oalewa, the small near-Earth asteroid it launched to sample more than a year ago. Over the weekend, the mission “quietly performed a crucial engine burn to rendezvous with a mysterious tiny world in a quasi-Earth orbit,” according to Scientific American. The probe was scheduled to rendezvous with the asteroid around June 7, according to a tracking summary from China in Space, with orbital insertion timed for that date, per Wikipedia’s mission record.
The arrival begins the most consequential phase of the mission, which The Machine Herald previously reported on when a new study reinterpreted the asteroid’s likely origin shortly before the probe closed in.
What We Know
Tianwen-2 lifted off on a Long March 3B rocket from the Xichang Satellite Launch Center on May 28, 2025, according to Wikipedia. Ground stations had “indicated that the spacecraft continues to regularly communicate with Earth and is possibly preparing to perform an arrival burn,” China in Space reported ahead of the rendezvous.
With the burn complete, the spacecraft now enters a survey phase. “Over the next four weeks, the spacecraft will approach the rapidly spinning asteroid to begin studying and mapping its surface, lining up future sampling attempts,” Scientific American reported. A close approach within 20 kilometers is planned for July 4, according to Wikipedia.
The target is a difficult one. Kamo’oalewa is “a space rock between about 40 to 100 meters in size that rotates once every 28 minutes,” Scientific American noted — a fast spin that complicates any contact with the surface. The asteroid was detected on April 27, 2016 by Pan-STARRS at Haleakala Observatory in Hawaii and carries the provisional designation 2016 HO3, according to Wikipedia. It is one of Earth’s quasi-satellites, described as “the second-smallest, closest, and most stable known such quasi-satellite,” the same entry states.
The Sampling Plan
To collect material, Tianwen-2 carries “three available sampling methods — touch and go, hover, and anchor and attach,” Scientific American reported. The mission plans to attempt collection using both anchor-and-attach and touch-and-go methods, marking the first use of anchor-and-attach on an asteroid, as prior missions relied on touch-and-go exclusively, according to Wikipedia. The disclosed target is to return at least 100 grams of regolith, the same record states.
If the sampling succeeds, “Tianwen-2 will complete its sampling and depart from Kamo’oalewa next April, after which it will be bound for a brief reunion with Earth in November 2027,” Scientific American reported. The spacecraft is set to depart the asteroid on April 24, 2027, per Wikipedia. A successful return would bring China its first asteroid samples to Earth.
The mission does not end there. After delivering the sample, “the spacecraft will then use Earth’s gravity to slingshot itself on course to visit Comet 311P, arriving in 2035,” Scientific American reported.
The Origin Question
What the samples might reveal is the subject of an active debate. The asteroid “may have been created when an ancient impact on the moon blasted a fragment into space,” a long-standing hypothesis, Phys.org reported. A recent study instead concluded that “Kamo’oalewa probably originated from the Flora family and developed an Itokawa-compositional, more space-weathered surface,” the same report noted, though its authors “do not completely close the door of lunar composition,” Phys.org added.
The statistical odds favor a more distant source. An asteroid on Kamo’oalewa’s orbit is “10 times more likely to have originated from the inner main asteroid belt than from the moon,” Mikael Granvik told Scientific American.
What We Don’t Know
Much about the asteroid remains unresolved until the spacecraft gets closer. “Every new image of an asteroid has been a surprise. We have everything to learn,” Patrick Michel told Scientific American. Whether the anchor-and-attach technique works as intended on such a small, fast-rotating body, and whether the returned material settles the lunar-versus-main-belt origin question, will not be known until the sample is in laboratories.
Analysis
For China, the arrival is a milestone in a deep-space program that is broadening from Mars and the Moon toward small bodies. The mission’s scientific payoff hinges on two firsts: returning the country’s first asteroid sample, and demonstrating an anchor-and-attach collection method no spacecraft has used at an asteroid. Either result would expand the toolkit available to future sample-return missions, regardless of how the origin debate ultimately resolves.