Tianwen-3: the Chinese mission to return samples to Mars

What is China’s plan?

China has declared its intention to conduct a Mars sample-return mission for years, but it’s only now, after recent successes in its space program, that more solid details about the mission – called Tianwen – 3 – emerge.

Earlier this summer, Sun Zezhou, chief designer of China’s first Mars mission, gave a big update on Tianwen-3, which included unveiling new mission profiles, spacecraft details and their configurations, and some of the technologies involved.

The mission plans a pair of launches in 2028 that would return a sample to Earth in July 2031. If successful, Tianwen-3 would be the first-ever robotic delivery of samples from Mars to Earth. While NASA and the European Space Agency have proposed their own joint Mars sample return mission, it would not return to Earth until two years after Tianwen-3.

Tianwen-3 would use two spacecraft: one for landing and collecting, and another for orbiting and returning samples. The landing segment would consist of a lander landing on Mars to collect rock samples. It would also carry an ascent vehicle to send collected material back into space.

Once in Mars orbit, the ascent vehicle would dock with the orbiter, which would launch separately from the landing segment. The orbiter is tasked with escorting the samples back to Earth and would carry a return capsule designed to deliver Martian material safely through high-speed, high-temperature re-entry into Earth’s atmosphere.

Two different mission profiles are currently being studied. In both configurations, two Long March 5 rockets — the same type of launch vehicle that carried Tianwen-1 and Chang’e-5 — would each launch one of the spacecraft. The orbiter would lift off from Wenchang in the island province of Hainan in November 2028.

The main difference between the two mission profiles is whether the lander launches before or after the orbiter. One profile calls for a December 2028 launch of the lander, which would arrive on Mars in July 2029 and spend about 6 months collecting samples. Alternatively, the lander could launch earlier – outside the traditional low-energy Mars launch window – in May 2028, and land only in August 2030. In both profiles, the orbiter would arrive in front of the lander, in August or September 2029.

A later landing could provide better solar-powered conditions, avoiding winter in the northern hemisphere, but would allow less time – about three months – on the surface before an ascent vehicle lifts off in October 2030. Both mission profiles would see the orbiter depart Mars and return home in October 2030, with a sample landing on Earth scheduled for July 2031.

Previous mission profile presentations suggested the use of a Long March 9, a super-heavy rocket currently under development that could be ready to fly around 2028. Another proposal was to use a Long March 5 and a Long March 3B. The move to a pair of larger Long March 5s suggests there may have been changes to the lander design.

Although China has not discussed its plans for landing sites, the previous Tianwen-1 mission could be instructive since China has already proven the technology needed to land in this region. Zhurong’s 2021 landing took place in the flat, low-lying region of Utopia Planitia in the Northern Hemisphere, meaning the spacecraft had more time in the atmosphere to slow its descent. Landing at higher altitudes on Mars — as some NASA spacecraft have done — would require further improvements in entry, descent, and landing (EDL) technology and increase mission complexity.

China has built secure labs on Earth to handle its lunar samples, but it’s unclear at this stage how it will address the needs and concerns of processing fresh samples from Mars. It is also unclear how much material China intends to bring home with Tianwen-3.

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