Chief scientist of China's Tianwen-3 mission says search for signs of life on Mars is top goal

HEFEI, Sept. 4 (Xinhua) -- China's Tianwen-3 mission is seeking evidence of whether life has ever existed on Mars, aiming to collect high-value Martian samples and conduct detailed analyses after bringing them to Earth, the mission's chief scientist Hou Zengqian told Xinhua in an interview Thursday.

Searching for potential signs of life on Mars is the top scientific goal of the Tianwen-3 mission, Hou said on the sidelines of the 2026 International Deep Space Exploration Conference, which opened on Thursday in Hefei, capital of east China's Anhui Province.

As a key step in China's planetary exploration program, Tianwen-3, planned for launch around 2028, is expected to become the first Mars sample-return mission in human history. Previously, NASA's Perseverance rover collected shallow surface samples, and will rely on a follow-up mission to return them to Earth. In contrast, Tianwen-3 aims to accomplish both sampling and return in a single mission.

Hou, also an academician of the Chinese Academy of Sciences, said China expects to finalize the landing site for the mission by the end of 2026, while Chinese scientists are advancing work on a new-generation geological map of the entire Mars.

Mars is one of the terrestrial planets in the solar system most similar to Earth and is widely considered a celestial body that may have once harbored life beyond Earth. Although Mars has evolved into a cold and arid planet with a thin atmosphere and no global magnetic field, its past habitability and the possibility that life once existed there remain among the most important frontier questions in planetary science.

Over the past half-century, 47 Mars exploration missions have been conducted worldwide. However, more challenging endeavors, including sample-return and crewed missions to Mars, have yet to achieve a decisive breakthrough.

"The Tianwen-3 mission will look for microbial traces potentially similar to early forms of life on Earth, while also taking into consideration the possibility of unknown forms of life that may have emerged through Mars' unique evolutionary history, providing crucial evidence to answer this major scientific question," Hou said.

The mission could also deepen scientific understanding of the planet's climate evolution and geological processes and advance research in comparative planetology and the origins of life, the scientist said.

According to Hou, Mars sample return is an extremely complex project, with landing-site selection, planetary protection and contamination control, and the identification of potential signs of life among its key challenges.

Chinese scientists are selecting candidate landing sites for the mission based on factors that include geological age, history of water activity, habitability and the potential for preserving biosignatures.

China will also build the world's first planetary protection laboratory to prevent terrestrial microorganisms from contaminating Mars while ensuring the safe isolation of returned samples, according to Hou.

To address the challenge of detecting potentially tiny amounts of life-related materials in Martian samples, Chinese scientists are conducting dedicated research to establish a high-fidelity methodology covering the entire process for identifying biosignatures in returned samples.

"Regardless of whether signs of life are found, the returned Martian samples will have irreplaceable scientific value," Hou said.

He said analyses of the samples at microscopic, molecular and isotopic scales could deepen understanding of Mars' geology, environment, evolution of habitability and the conditions under which life may originate.

The mission has now entered the stage of developing engineering prototypes, Hou said.

He added that the Mars sample-return mission will not only provide a comprehensive test of China's engineering capabilities, but also serve as a major driver of planetary science.

Chinese scientists are advancing work on a new-generation geological map of the entire Mars by making full use of data from the Tianwen-1 mission and multiple international sources. The project integrates information from imagery, spectroscopy, radar and gravity measurements, and applies artificial intelligence to geological interpretation. Version 1.0 of the 1:5 million scale geological map of the entire Mars is scheduled for completion by the end of 2028.

Tianwen-3 will uphold the principle of open cooperation and work with scientists around the world to explore the mysteries of Mars, contributing China's expertise and solutions to expanding humanity's scientific frontier and advancing planetary science, Hou added.