China Launches Tianwen-2 Asteroid Sample-Return Mission

China launched the robotic Tianwen-2 spacecraft today to return samples from a Near Earth Asteroid that is in an orbit around the Sun similar to Earth’s. China has brought back samples from the Moon twice already, but this will be the first time from an asteroid. If successful, it will join Japan and the United States in achieving that feat and, like those spacecraft, Tianwen-2 will continue on to a secondary mission — studying a comet in the main asteroid belt between Mars and Jupiter.

China has accomplished quite a bit in robotic lunar exploration with the Chang’e series of spacecraft that have landed on the near-side and the far-side and returned samples from both, but its ventures deeper into space are limited. Tianwen-1 is China’s only other dedicated deep-space probe, putting an orbiter around and a lander on Mars in 2021.

Tianwen-2 lifted off from China’s Xichang Satellite Launch Center at 1:31 pm ET today (1:31 am May 29 Beijing Time) on a Long March-3B rocket.

Tianwen-2 is headed to asteroid 469219 Kamoʻoalewa (2016 HO3). The asteroid was discovered by the Pan-STARRS 1 telescope operated by the University of Hawaii’s Institute of Astronomy. Kamoʻoalewa means oscillating celestial fragment in Hawaiian. Considered a “quasi-satellite” of Earth, some scientists think it originated on our Moon and was ejected into space by an impact that created the Giordano Bruno crater on the lunar far side.

The samples should help verify that hypothesis. The small asteroid, 130-330 feet (40-100 meters) in diameter, is not very far away. Tianwen-2 will get there in July 2026 and go into orbit to study the surface.

Collecting samples from a body with near-zero gravity is no easy task and 2016 HO3 also rotates rapidly. Chen Chunliang, an expert from the China Aerospace Science and Technology Corporation, told China’s state news agency Xinhua that the “asteroid’s shape, rotational behavior and surface characteristics all remain unclear, which significantly complicated the design of both the spacecraft and its sampling methods.”

The spacecraft is designed with two options: the “touch and go” method used by Japan and the United States, and a novel “anchor and attach” method using drills. The goal is to obtain 20-100 grams of material (0.7-3.5 ounces).

Tianwen-2 will depart the asteroid in April 2027 and head back towards Earth, arriving in November 2027.  As with Japan’s Hayabusa in 2010 and Hayabusa2 in 2020, and the U.S. OSIRIS-REx in 2023, the sample return canister will detach from the main spacecraft and land on Earth while the main spacecraft continues on in space to explore other objects. NASA’s OSIRIS-REx, for example, has been renamed OSIRIS-APEX and will study the asteroid Apophis after it makes a close pass by Earth in 2029.

Tianwen-2’s secondary mission is to study comet 311P/PANSTARRS, a rare main-belt comet. After arriving there in 2035, Tianwen-2 will observe the unusual object for a year. With characteristics of an asteroid, observations by the Hubble Space Telescope show it also has comet-like tails.  Scientists want to know why.

China has more deep-space ambitions: Tianwen-3 is a Mars sample return mission expected to launch in 2028, and Tianwen-4 in 2029 will orbit Jupiter and its moon Callisto.

Tianwen means “Questions to Heaven.”