China's Tianwen-3 Mars Sample-Return Mission Set for 2028 Launch

China is set to launch its first Mars sample-return mission, Tianwen-3, around 2028, with the ambitious goal of returning at least 500 grams of Martian samples to Earth by 2031. This announcement was made by Hou Zengqian, chief scientist of the Tianwen-3 mission and an academician at the Chinese Academy of Sciences, during a recent press briefing. The mission aims to enhance global understanding of Mars and address fundamental questions about the planet's potential to harbor life.

The Tianwen-3 mission represents a significant milestone in China's planetary exploration efforts. According to the mission's planning documentation, the spacecraft will undergo two launches, taking approximately seven to eight months to reach Mars. Once in Martian orbit, it is expected to operate for about one year before returning to Earth, culminating in a complex three-year mission.

In a detailed article published in *Nature Astronomy*, Hou outlined three primary scientific objectives that the mission aims to achieve: searching for potential signs of life on Mars—including biomarkers, fossils, and archaea; studying the evolution of the planet's habitability, focusing on changes in its water, atmosphere, and oceanic history; and investigating the geological structure and evolutionary history of Mars.

"The mission will be a critical step in China's planetary exploration. We hope to provide the international community with an unprecedented opportunity to understand Mars," said Hou.

To accomplish its objectives, Tianwen-3 will employ three innovative sampling techniques: surface scooping, deep drilling, and drone-assisted collection. Notably, the mission will conduct the first international deep drilling for sample collection on Mars, aiming to reach depths of up to two meters—something previous missions, such as NASA's Perseverance rover, have not achieved.

Planetary protection is a major concern in deep space exploration, and Hou emphasized the importance of contamination control. Strict measures will be implemented to prevent the contamination of Mars by the spacecraft as well as to safeguard Earth's biosphere from potential Martian life forms. Adhering to the planetary protection policies established by the Committee on Space Research, China is committed to ensuring both the authenticity and reliability of the scientific results obtained from the mission.

The selection of the landing site on Mars is pivotal to the mission's success. From an initial pool of over 80 candidate sites, the team has narrowed it down to 19, with three final sites to be selected by the end of 2026. The chosen site must meet both engineering constraints and scientific priorities, particularly the potential to harbor and preserve traces of life. According to Hou, identifying a suitable landing site requires a thorough understanding of the conditions that promote life, akin to mineral exploration on Earth.

Collaboration is a cornerstone of the Tianwen-3 mission. China has opened the research and sample analysis processes to international cooperation, inviting global scientists to participate in discussions and proposals. This approach aims to create a platform for shared scientific endeavors, as Hou stated, "We aim to build a global platform for scientific collaboration through planetary exploration."

Despite the ambitious goals and significant technological challenges associated with the Tianwen-3 mission, experts like Liu Jizhong, chief designer of the mission, remain optimistic. He noted that retrieving samples from Mars represents one of the most technically challenging aspects of space exploration since the Apollo program, involving 13 complex phases that utilize both in-situ and remote-sensing detection technologies.

The upcoming Tianwen-3 mission is set to not only advance China's position in global space exploration but also potentially yield groundbreaking insights into the history of life on Mars and the planet's geological evolution. As the 2028 launch date approaches, the international scientific community eagerly anticipates the findings that may emerge from this historic endeavor.