Tianwen-2: China’s Upcoming Missions to Two Rocky Bodies in the Solar System

China is making final preparations to launch a spacecraft aimed at exploring asteroids and comets, seeking to gain insights into these celestial bodies in our solar system.

The Tianwen-2 mission, orchestrated by the China National Space Agency (CNSA), plans to collect 100 grams of samples from the asteroid Chuan West and return them to Earth. Following the sample retrieval, the probe will utilize Earth’s gravity to propel itself towards the comet 311P/Panstarrs, which will be observed remotely.

The mission is set for launch from the Xichang Satellite Launch Center in Sichuan Province on May 29th. While NASA’s Osiris-Rex and JAXA’s Hayabusa missions have previously returned asteroid samples, this marks China’s inaugural asteroid mission, including the return of rock samples, and potentially the first mission aimed at a unique type of celestial body known as quasi-satellites.

Quasi-satellites, like Kamo`oalewa, do not orbit the Earth in a traditional manner; instead, they follow orbits around the Sun that are similar to Earth’s, creating an oval path relative to our planet. This intriguing scenario has led scientists to theorize that this may be a remnant lunar mass ejected by an asteroid impact millions of years ago.

In contrast, 311P/Panstarrs has an asteroid-like orbit, encircling the Sun within the asteroid belt between Mars and Jupiter, yet possesses a tail that gives it a comet-like appearance. This is believed to be composed of dust and debris shed from its nucleus.

The CNSA has previously indicated that 311P/Panstarrs is a “living fossil,” crucial for studying the early material composition, formation processes, and evolutionary history of the solar system. Tianwen-2 aims to enhance our understanding of both Kamo`oalewa and 311P/Panstarrs. However, the findings will not be available immediately, as the spacecraft is expected to reach 311P/Panstarrs by 2034, and the Kamo`oalewa samples are anticipated to return to Earth in the latter half of 2027.

It remains uncertain what extent the CNSA will share these findings. Leah-Nani Alconcel from the University of Birmingham, UK, mentions that the mission outline is known but lacks detailed information. One of the objectives may involve examining the differences between asteroids and comets to gain better insights into the diverse bodies of our solar system; however, specific details remain elusive.

In her previous experience with CNSA’s Double Star Satellite, Alconcel expressed concerns about the institution’s ability to provide substantial scientific data. She states, “It was incredibly challenging to negotiate with [the CNSA]. There is no public repository for this data.”

She describes the mission as ambitious, noting that Kamo`oalewa is in a rotating behavior. Navigation algorithms may require powerful computing resources to process images and sensor data sent back to Earth for calculations. “If we always opt for favorable and stable objects, we won’t gain much knowledge,” she warns. “There are numerous potential challenges ahead.”

The CNSA has not responded to requests for comment from New Scientist.