Ancient Endorheic Lake Basins: Promising Sampling Sites for the Tianwen-3 Mars Sample Return Mission

The China National Space Administration has announced its Mars Sample Return mission Tianwen-3 to search for life on Mars. Tianwen-3 will be launched in 2028 and return ∼500 g of samples in 2031. Since the Tianwen-3′s stationary lander will use a built-in 2 m drill to retrieve samples from depth and a robotic arm to scoop surface deposits, the strategy for selecting the landing site should differ from that of missions with rovers. Based on discoveries by the Curiosity and Perseverance rovers, we suggest that Tianwen-3 should land in an ancient endorheic lake basin where aqueous sediments and rich authigenic minerals are preserved due to the past presence of a stable body of water and high likelihood of a sustained period of vertical cycling of deep fluids. Our recent observations of brines and iron oxides precipitated by iron bacterial metabolism in a hyperarid, highly evaporative Mars analog basin further support the hypothesis that low-lying, closed crater basins on Mars are of high astrobiological value for upcoming sample return missions.