A Chinese spacecraft is roughly six weeks from rendezvous with one of the strangest rocks in Earth’s neighborhood. Tianwen-2 launched from Xichang on May 28, 2025, on a Long March 3B, and has been cruising toward 469219 Kamoʻoalewa ever since. Mission planners now expect arrival in July 2026, with sample collection beginning shortly after a survey phase. The return capsule is scheduled to deliver material to Earth in November 2027. If it works, it will be the third successful asteroid sample return ever flown, after Japan’s two Hayabusa missions and NASA’s OSIRIS-REx.
The target is weird
Kamoʻoalewa is one of five known quasi-satellites of Earth. It orbits the Sun, not our planet, but its orbit is tuned so closely to Earth’s that from our point of view it appears to loop nearby for decades at a time. The name, given by astronomers at the University of Hawaii in 2019, is Hawaiian for “an oscillating celestial object.” It is small, somewhere between 40 and 100 meters across, and dim. It was only discovered in 2016 by the Pan-STARRS survey on Haleakalā.
Two things make it interesting beyond its orbital tricks. First, its reflectance spectrum matches lunar rock better than it matches typical asteroid material. A 2021 study in Communications Earth and Environment, led by Ben Sharkey at the University of Arizona, compared Kamoʻoalewa’s color and brightness across infrared wavelengths to silicate samples returned by the Apollo missions. The best fit was weathered lunar silicate. The leading hypothesis is that Kamoʻoalewa is a chunk of the Moon, blasted off by an impact in the last few million years, and now drifting in a near-Earth orbit it has not yet escaped from. Direct evidence has been missing. A sample would settle it.
Second, quasi-satellites are short-lived. Models suggest Kamoʻoalewa has been in its current orbital configuration for roughly 100 years and will remain there for another 300 or so before perturbations from the Sun and Earth nudge it onto a different path. Catching it now, while it is close, is several orders of magnitude cheaper in delta-v than chasing a typical main-belt asteroid.
The sampling problem
Touching a 50-meter rock with no measurable gravity is harder than landing on the Moon. There is nothing holding the spacecraft down. Anchor points are uncertain. The surface might be dust, rubble, or solid stone, and Kamoʻoalewa is too small for ground-based radar to tell you which.
Chinese engineers have built Tianwen-2 to attempt two methods in sequence. The first is touch-and-go, the same approach NASA’s OSIRIS-REx used at Bennu in 2020: descend slowly, kiss the surface with a sampling head, fire a burst of nitrogen gas to lift loose material into a collection chamber, then climb away. The second, only attempted if conditions look right, is anchor-and-attach. The spacecraft would deploy four small robotic arms that grip the surface with drills, then sample the rock directly. No mission has ever flown anchor-and-attach on a body this small.
Total sample target is 200 to 1,000 grams. By comparison, OSIRIS-REx delivered 121.6 grams of Bennu and Hayabusa2 returned 5.4 grams of Ryugu. If Tianwen-2 hits the high end of its range, it will be the largest extraterrestrial sample return in history outside the Apollo program.
After the asteroid
The mission does not end when the samples leave. After releasing the return capsule on a trajectory toward Earth in late 2027, the main spacecraft will swing back into deep space and head for 311P/PANSTARRS, a main-belt object that is part comet and part asteroid. It sheds dust like a comet but orbits like an asteroid, and astronomers still argue about what it actually is. Arrival is planned for 2035. Tianwen-2 will study it from orbit but not attempt to land.
That second leg makes Tianwen-2 unusual. It is two missions sharing a spacecraft. The asteroid sample piece is on a tight clock because the return capsule must hit a narrow re-entry window over Inner Mongolia. The comet piece runs on a much longer leash, a decade-long bonus once the primary objective is in the bag.
Why this matters
If the spectra are right and Kamoʻoalewa is lunar, sampling it gives planetary scientists something they have wanted for a long time: a piece of Moon ejecta, fresh enough to date, that traveled to a new orbit on a known recent timeline. Apollo and Chang’e samples come from carefully chosen sites on the lunar surface. None of them tell you what an impact-blown fragment looks like after it has spent a few million years in interplanetary space.
If the spectra are wrong, and the rock turns out to be ordinary chondritic material, that is also useful. It would say Earth’s quasi-satellite is just another captured asteroid, and the population of nearby debris is more boring than the lunar-fragment hypothesis suggested. Either result is a real answer.
Mission status checks come through the China National Space Administration and amateur radio tracking of the deep-space telemetry beacon. The cruise has been quiet, which is what you want. The interesting part starts in July.
Sources: Sharkey et al., Communications Earth and Environment, 2021; NASA JPL: Kamoʻoalewa overview; Tianwen-2 mission profile, Wikipedia; SpaceNews launch coverage; 311P/PANSTARRS background.