Tianwen-2 reaches asteroid Kamoʻoalewa
China's Tianwen-2 began closing in on Kamoʻoalewa, a small asteroid that travels alongside Earth, with a rendezvous burn on 7 June 2026, and by early July held an observing position about 20 km away. It is to study and sample the asteroid until April 2027 and bring the sample to Earth late that year.
The story
Tianwen-2, a mission of the China National Space Administration (CNSA), lifted off on a Long March 3B rocket from the Xichang launch centre on 28 May 2025 (UTC; 29 May in China). Its task is to collect rock and dust from the asteroid Kamoʻoalewa and bring them back to Earth. After a little over a year in flight, it performed its rendezvous burn on 7 June 2026, about 30,000 km from the asteroid, to begin closing in.
Arriving at such a small body is a slow process. Kamoʻoalewa's gravity is extremely weak, so a spacecraft moving even slightly too fast would drift away or risk a collision. Tianwen-2 closed the distance gradually and in early July reached an observing position about 20 km from the asteroid. CNSA announced the milestone around 6 July.
Ground-based estimates put Kamoʻoalewa at 40 to 100 m across, but Tianwen-2's July images suggest it is only about 20 m, and it spins once every 28 minutes or so. It is known as a quasi-satellite of Earth. It actually orbits the Sun, not Earth, but its year is almost exactly as long as ours, so from Earth's point of view it appears to circle near the planet for long stretches of time.
What makes this little object special is a hypothesis about where it came from. A 2021 study of the colours of its reflected light found features resembling lunar rock, and a 2024 study suggested it could be debris thrown out by the impact that formed Giordano Bruno crater on the Moon's far side. The idea has not been proven. Tianwen-2 showed the asteroid to be smaller than expected, and for so small an object to look as bright as it does, its surface must reflect more light than typical lunar rock; some researchers see that as a point against the idea. Samples brought back by Tianwen-2 could settle the question directly.
Mission goals
If Kamoʻoalewa really is a piece of the Moon, its samples would be lunar rock that broke away from one particular place and then spent a long time drifting through space. Comparing them with samples taken directly from the Moon would show how exposure to space alters rock surfaces, and how debris from an impact can travel all the way into an orbit near Earth. If the hypothesis turns out to be wrong, the samples would still reveal where at least one of Earth's small companions came from.
The mission is also a demanding technical test. An object only about 20 m wide that turns every 28 minutes offers little room to choose a site and little to hold on to. Tianwen-2 plans to try several approaches: collecting while hovering above the surface, a brief touch-and-go contact, and an anchor-and-attach method that fixes the spacecraft to the ground. The goal is at least 100 g of material.
The mission is also the next step in China's planetary exploration. With Tianwen-1, China sent an orbiter and the Zhurong rover to Mars, and through the Chang'e programme it returned samples from the Moon. Tianwen-2 applies that experience to an asteroid for the first time. The skills it builds in approaching, sampling and returning are meant to carry forward to Tianwen-3, which aims to bring soil and rock back from Mars.
Mission chronology and background
China already has experience bringing material home from space: Chang'e 5 returned samples from the Moon's near side in 2020, and Chang'e 6 from its far side in 2024. Asteroid samples have been returned before by Japan's Hayabusa from Itokawa in 2010, Hayabusa2 from Ryugu in 2020 and NASA's OSIRIS-REx from Bennu in 2023. Tianwen-2 is China's first asteroid sample-return mission.
The spacecraft's work does not end when the capsule is released. After passing Earth, the main spacecraft is planned to continue to comet 311P/PANSTARRS, arriving in January 2035. The mission thus links a tiny near-Earth asteroid with a comet in a single long voyage.
Kamoʻoalewa was discovered in 2016 by the Pan-STARRS survey telescope on Haleakalā in Hawaii. Its name comes from a Hawaiian creation chant and refers to an oscillating fragment of the sky, a fitting description of an object that seems to swing back and forth near Earth. Because its orbit is so similar to Earth's, it is also a relatively convenient target for a spacecraft to reach.
Other milestones of this mission
- Tianwen-3 — Mars sample return bid(planned)
- Tianwen-3 samples return(planned)
Where to see it — sky and simulator
Neither Kamoʻoalewa nor Tianwen-2 can be seen in the sky without help. The asteroid is so small that even large telescopes show only a very faint point, and the spacecraft is far smaller still. Tianwen-2's path is not included in this simulator. The most reliable way to follow the mission is through the images and updates released by CNSA.
The mission is now in its mapping and sampling phase, which runs until April 2027; the exact dates of sample collection have not been announced. The next milestones to watch for are departure from the asteroid, planned for 24 April 2027, and the landing of the sample capsule on Earth, planned for around 09:15 UTC on 29 November 2027.
FAQ
Is a quasi-satellite a second moon?
No. Kamoʻoalewa orbits the Sun, not Earth. Because its orbital period is almost the same as Earth's, it only appears to circle near our planet when seen from here, which is why it is called a quasi-satellite rather than a moon.
Is it certain that Kamoʻoalewa came from the Moon?
No. It is a hypothesis supported by a 2021 study of its reflected light and a 2024 study linking it to a lunar crater. Laboratory analysis of the samples Tianwen-2 brings back would be a direct test.
When will the samples reach Earth?
Under the current plan the spacecraft leaves the asteroid on 24 April 2027 and the capsule lands on Earth around 29 November 2027. The schedule could change depending on how sampling and navigation go.
How much material will it collect?
The target is at least 100 g. Tianwen-2 plans to try hovering collection, a brief touch-and-go contact and an anchor-and-attach method that fixes it to the surface.
Related
- Hayabusa2 flies past Torifune
- The Moon
- Tianwen-3 launch
- Hera arrives at Dimorphos
- OSIRIS-APEX at Apophis
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.