HELSINKI — China launched its second planetary exploration mission Wednesday, sending Tianwen-2 to sample a near Earth asteroid and later survey a main belt comet.
Tianwen-2 lifted off on a Long March 3B rocket at 1:31 p.m. Eastern (1731 UTC) from Xichang Satellite Launch Center, southwest China, climbing into the night sky above the spaceport.
The China Aerospace Science and Technology Corporation (CASC) announced the successful launch of Tianwen-2 just over an hour after liftoff.
Tianwen-2 is now in a transfer orbit, headed for the 40 to 100-meter-diameter near-Earth asteroid 469219 Kamoʻoalewa (2016 HO3). It is expected to rendezvous with the small, rocky body around July 2026, spending seven months studying the near Earth object and collecting samples. The samples are expected to be returned to Earth in late 2027.
Analysis of the samples aims to reveal the nature and origin of the asteroid—which is possibly a piece of the moon blasted into space following an impact event—analyze its mineral content and provide valuable comparisons with other asteroids.
Tianwen-2 will release a reentry module containing the samples on return to the Earth, but this will not be the end of the mission. The main spacecraft will use the Earth for gravitational swingby, setting it on course for a six-year-voyage to comet 311P/PANSTARRS.
Small body complexity, science potential
The asteroid and comet mission will provide China with a range of experience and expertise in mission design and operations, such as advancing spacecraft autonomy, navigation, planning orbits and sampling technologies in extremely challenging environments, Franco Perez-Lissi, Ramses mission systems engineer at the European Space Agency (ESA), told SpaceNews.
While China has conducted two lunar sample return missions, including the moon’s far side, approaching and “orbiting” these small objects will bring new challenges, in terms of rendezvous, approach and sampling.
“These bodies have extremely weak and irregular gravity fields,” Perez-Lissi said, referring to asteroids and comets. “So we cannot rely on traditional orbiting like we do around the planet.”
Tianwen-2 will need to fly in carefully planned trajectories to maneuver around and study the asteroid, as well as match its speed and rotation for sampling.
“It’s like trying to dock a boat with a mountain floating in space and tumbling really unpredictably and with almost no gravity. So landing, or even just flying close, requires extreme precision, greater autonomy and careful planning,” Perez-Lissi said.
The science and data return will also be of great value, with Perez-Lissi noting that past missions such as Rosetta, Hayabusa2 and OSIRIS-REx showed that in-situ measurements or returned samples can contain organic molecules, amino acids, and nucleobases—potential ingredients for life.
Tianwen-2 joins a number of international efforts which contribute to shared scientific and planetary defense knowledge, notably ESA missions Ramses and Hera, NASA’s DART and OSIRIS-REx/Apex missions, and JAXA’s Hayabusa series and Destiny+.
“It’s always very positive that more and more people are venturing into asteroid missions. It may well be helpful for the future, since we are engaging in planetary defense, but also it’s extremely interesting for science and to understand our origins.”
Tianwen series and long-term exploration
The mission follows the successful Tianwen-1 Mars orbiter and rover mission launched in 2020, and will be followed by ambitious Mars sample return (Tianwen-3) and Jupiter system (Tianwen-4) missions later in the decade.
Tianwen-2 aims to advance China’s planetary exploration capabilities and deepen our understanding of small planetary bodies and their evolution. It could also contribute to planetary defense and shed light on the origins of life.
The missions are also part of a wider planetary exploration roadmap focused on astrobiology and habitability, and a long-term plan for space science, including a Venus sample return mission, the International Lunar Research Station (ILRS) and searching for habitable exoplanets.
Asteroid ambitions
The spacecraft will attempt up to three methods of sampling: hover sampling, collecting samples with a robotic arm while matching the asteroid’s rotation; touch-and-go (TAG), using a rotating brush head; and anchored sampling, in which landing legs would use drills at the end of landing legs to press into the asteroid, if the surface composition and terrain allow. The TAG approach was used by both NASA’s OSIRIS-REx and JAXA’s Hayabusa2.
China has released few official detailed plans for the mission. Early proposals for the mission, then named Zheng He for the Chinese admiral and explorer born in the 14th Century, indicated the mission would aim to collect between 200 and 1,000 grams of samples.
Chinese scientists have called for a strategic focus on asteroid missions, which could both contribute to overall understanding of the cosmos and also lay the groundwork for future space resource utilization and planetary defense.
Comet rendezvous, wider context
The comet phase of the mission will also be a test in terms of longevity of the spacecraft, with arrival at 311P/PANSTARRS expected around 2035, a decade after liftoff. The target comet is seen as an ideal target for studying transitional objects between asteroids and comets, orbiting between 1.94 and 2.44 astronomical units from the Sun.
Tianwen-2 carries 11 science payloads for studying both Kamoʻoalew and 311P/PANSTARRS. These include multispectral and infrared spectrometers to study surface composition, while high-resolution cameras will map geological features. A radar sounder will probe subsurface structures, and a magnetometer will search for residual magnetic fields. Dust and gas analyzers will examine comet activity, and charged particle detectors will investigate solar wind interactions.
The mission to sample Kamoʻoalewa and later survey a main belt comet sees China join a growing global context of missions tackling the complex environment of small-body exploration, demonstrating its expanding ambitions in space.
It will also allow China’s engineers and scientists to test themselves against some of the toughest problems in terms of planetary science and defense, and potentially resource utilization.
