HELSINKI — China is making progress towards a 2030 launch for its Tianwen-3 Mars sample return mission and has narrowed down potential landing areas.
Work on China’s Tianwen-3 Mars sample return mission is progressing “relatively smoothly” and will launch around 2030, Sun Zezhou, a senior engineer at the China Academy of Space Technology (CAST), told China Central Television (CCTV) March 6. Sun was the chief designer of China’s successful Tianwen-1 Mars orbiter and rover mission.
The update, while short and vague, comes as NASA is reassessing its Mars Sample Return (MSR) mission due to major budget and schedule concerns. A final fiscal year 2024 spending bill deferred a decision on spending for MSR.
China’s Tianwen-3 Mars sample return architecture is a simpler approach than NASA’s, yet is still a very complex mission. Two Long March 5 launches will carry a lander and ascent vehicle and an orbiter and return module respectively. Entry, descent and landing will build on technology used for the Tianwen-1 rover landing.
On the surface, the lander will use a robotic arm to collect surface samples and a drill to collect material from up to two meters below the surface. Either a six-legged crawling robot or an Ingenuity-like helicopter could fly on the mission to add the capacity to collect a more diverse set of samples. The mission targets delivering around 500 grams of Martian samples to Earth.
Sun outlined the main challenges as obtaining rock samples and then taking off from the surface of Mars, followed by a rendezvous and docking in orbit and the transfer of the samples to a reentry module. These require a high degree of autonomy in terms of system design.
The technical foundation is already in place, Sun said. China has Mars entry, descent and landing experience from Tianwen-1. It has also conducted sampling and launch from another planetary body with the Chang’e-5 lunar sample return mission. Sun added that the samples could help provide answers as to whether there were ever traces of life on Mars.
Sun was speaking on the sidelines of China’s ongoing annual parliamentary sessions in Beijing. His comments provide limited insights into progress of the mission. Chinese officials earlier stated a launch date of 2028, with samples to be returned in 2031. The 2030 statement indicates the mission will miss that Mars launch window. This means a slip of 26 months to the next such opportunity.
Tianwen-3 landing site selection
A recent research article in the journal JGR Planets additionally reveals three preselected landing zones for Tianwen-3. These are Amazonis Planitia, Utopia Planitia—the area within which the Zhurong Tianwen-1 rover landed—and Chryse Planitia.
The paper assesses Martian atmospheric eddies, or movements of air, dust, or water in a circle. It advises that regions with frequent atmospheric eddy occurrences should be avoided for the safety of the Tianwen-3 landing and ascent stages. The paper finds Chryse Planitia to be the optimal landing area for Tianwen-3.
Chryse Planitia, a lowland plain, was an alternative landing area for the Zhurong rover. The circular plain is situated at the eastern end of the vast outflow channel system known as Valles Marineris. It harbors potential evidence of past flowing water on Mars and is thus of astrobiological interest. The Viking 1 lander also set down within Chryse Planitia.
The three areas are between 17 and 30 degrees north latitude, due to energy and lighting requirements. Other constraints include being at least 2,000 meters or preferably 3,000 meters below the average global Martian elevation. This provides the lander with more atmosphere to move through to slow its descent onto the Martian surface. The new paper will likely provide input into the final site selection, but not determine it.
Potential landing ellipses of 50 by 20 kilometers have been identified within these areas, according to presentations at an International Conference of Deep Space Sciences in Hefei, China, in April 2023.
Site selection will also be balanced by science objectives, according to the presentations. The chosen site will need to be considered of astrobiological relevance, with Martian terrain older than 3.5 billion years being prioritized.
Further key priorities are environments suitable for the emergence of life and its preservation such as sedimentary or hydrothermal systems, evidence of past aqueous activity and geological diversity.
Planetary Science Decadal Surveys have recommended returning samples from Mars as a top priority. The report found MSR to be of fundamental strategic importance to NASA, U.S. leadership in planetary science, and international cooperation.
A successful mission would be a major engineering feat and bring profound science results. Samples could provide unique insights into the planet’s geological processes and history and enhance comparative planetology. Most significantly it could, potentially, deliver biosignatures or chemical traces of past or even extant life. The uncertainty surrounding the MSR means China could be the first to attempt to secure Martian samples and perform groundbreaking analysis.
