China's Tianwen-2 Probe Enters Asteroid Orbit on June 7
After about 13 months of flight, China's Tianwen-2 probe reaches the quasi-moon Kamooalewa and enters its orbit on June 7. Sampling begins in July.
- After about 13 months of flight, China's Tianwen-2 probe reaches the quasi-moon Kamooalewa and enters its orbit on June 7.
- Sampling begins in July, with a target of at least 100 grams of regolith from a body roughly forty metres across.
- The mission combines a touch-and-go sampling method with a new anchor-and-attach technique using four robotic arms for the first time.
- The sample capsule returns to Earth in late November 2027, after which the probe continues toward comet 311P/PANSTARRS.
The Tianwen-2 probe, launched by the Chinese space agency on May 28, 2025, aboard a Long March 3B rocket from the Xichang centre, reaches its destination after about 13 months of travel. The target is asteroid Kamooalewa (formal designation 469219 Kamooalewa), a small body roughly forty metres across that follows Earth along its path around the Sun. Orbit insertion is scheduled for June 7, 2026, marking the start of the mission’s main phase.
Kamooalewa is no ordinary asteroid. It is a quasi-moon, a body not gravitationally bound to Earth that nonetheless travels near it for decades because of their similar orbits. Spectral measurements taken earlier by telescopes showed that the light Kamooalewa reflects matches minerals found on the lunar surface, leading some researchers to suggest the body could be a fragment thrown off the Moon during an ancient impact. A soil sample could confirm or rule out that idea.
How will the probe collect a sample from such a small body?
The weak gravity of an asteroid only about forty metres wide makes a landing nearly impossible in the conventional sense. For that reason the Tianwen-2 team planned two approaches, with the rendezvous with the surface expected around July 4. The goal is to gather at least 100 grams of material.
- The touch-and-go method, similar to the one the American OSIRIS-REx probe used at asteroid Bennu, where the craft briefly descends and lifts off again amid a cloud of collected dust.
- The anchor-and-attach technique, used in practice for the first time, where the probe latches onto the surface with four robotic arms and stays fixed during sampling.
The second method is the most technically interesting part of the mission because it has never been tried on any space rock before. If it works, it gives engineers an alternative for bodies where the touch-and-go method fails to gather enough material.
What comes after the sampling
According to the mission plan, the sample capsule should return to Earth on November 29, 2027. Only then do laboratories receive material for analysis, so confirming or refuting the lunar-origin hypothesis will have to wait.
The mission’s goal is to collect samples from the quasi-moon Kamooalewa and return them to Earth for laboratory analysis of the body’s composition and origin.
Tianwen-2 does not end there. After delivering the capsule, the probe continues toward comet 311P/PANSTARRS, a body with traits of both an asteroid and a comet, where it is meant to carry out further observations. This is a dual mission, first a sample collection, then an extended scientific phase.
It is worth keeping in mind what this still does not prove. The spectral similarity to the Moon is an indication, not proof of origin, and a firm conclusion depends on the isotopic composition of the sample, which arrives only in a year and a half. Until then the question of what the measurements will show stays open.
Do you think the sample from Kamooalewa will confirm that it is a fragment broken off the Moon?
