China's Tianwen 3 robotic probe is expected to become the world's first Mars sample return mission, setting the search for proof of past life on the Red Planet as its top scientific goal, the mission's chief scientist said.
Hou Zengqian, an academician of the Chinese Academy of Sciences, made the remarks on the sidelines of the International Deep Space Exploration Conference 2026, which opened on Thursday in Hefei, Anhui province.
Noting that Mars is one of the terrestrial planets in our solar system similar to Earth, Hou said there is ample evidence that early Mars had liquid water, a denser atmosphere and a global magnetic field — key conditions for forming a habitable environment.
"That is why the mission takes searching for potential signs of past Martian life as its primary objective," he said, adding that through detailed analysis of returned samples, scientists hope to find reliable biosignatures.
According to the China National Space Administration, Tianwen 3 will have five components — a lander, an ascender, a service capsule, an orbiter and a reentry module — and will be launched around 2028 using two Long March 5 heavy-lift carrier rockets from the Wenchang Space Launch Center in Hainan province. If everything goes according to plan, the mission will collect samples from Mars and send them back to Earth around 2031.
Hou, who is also director of the State Key Laboratory of Deep Earth and Mineral Exploration at the Chinese Academy of Geological Sciences, said that to prepare for the return of the samples, China will build the world's first planetary protection laboratory to prevent both forward contamination of Mars by Earth-based microbes and backward contamination of Earth through returned samples, while keeping Martian samples free of terrestrial pollution.
He said that solid evidence of past Martian life, if found, would have profound implications for answering the fundamental question of whether life has ever existed beyond Earth. The mission will also study the Mars' habitability, geological and internal structure, and atmospheric evolution. "These topics are closely linked, as life relies on habitable environments, which are shaped by the Red Planet's long-term geological and climatic changes," he said.
As of now, eight probable landing areas for Tianwen 3 have been short-listed based on Mars' geological age, water activity history, habitability and biosignature preservation potential, in order to maximize the scientific value of collected samples, he said. "The plan is to drill up to 2 meters beneath the surface and collect subsurface samples, reducing damage to potential biosignatures from surface radiation, oxidation and weathering, thereby better preserving the planet's original geological information," Hou said.
As research and facility construction continue to progress, engineers have begun to develop a prototype of the Tianwen 3 spacecraft. Hou said the Tianwen 3 mission carries great significance for China's deep-space exploration and planetary science.
"It represents deeper integration of engineering capabilities, with major scientific questions determining the mission's overall plan and steps. Whether traces of life are discovered or not, the samples will boast irreplaceable scientific value, enabling detailed studies of Martian materials at microscopic, molecular and isotopic scales. It will drive interdisciplinary progress in astrobiology, planetary geology, geochemistry and life sciences. By seizing the first-mover advantage in Mars sample return, China will demonstrate its national strength and contribute to humanity's exploration of Mars and search for extraterrestrial life," he said.
China launched its first Mars mission, Tianwen 1, in July 2020. It was the country's first independent interplanetary exploration endeavor. The landing craft of Tianwen 1 touched down on Mars in May 2021 and then released a rover, called Zhurong, to perform scientific tasks. The rover traveled about 2,000 meters on the Red Planet and transmitted a great deal of data back to Earth.