The Mars Sample Return mission intends to retrieve a sealed collection of rocks, regolith, and atmosphere sampled from Jezero Crater, Mars, by the NASA Perseverance rover mission. For all life-related research, it is necessary to evaluate water availability in the samples and on Mars. Within the first Martian year, Perseverance has acquired an estimated total mass of 355 g of rocks and regolith, and 38 μmoles of Martian atmospheric gas. Using in-situ observations acquired by the Perseverance rover, we show that the present-day environmental conditions at Jezero allow for the hydration of sulfates, chlorides, and perchlorates and the occasional formation of frost as well as a diurnal atmospheric-surface water exchange of 0.5–10 g water per m² (assuming a well-mixed atmosphere). At night, when the temperature drops below 190 K, the surface water activity can exceed 0.5, the lowest limit for cell reproduction. During the day, when the temperature is above the cell replication limit of 245 K, water activity is less than 0.02. The environmental conditions at the surface of Jezero Crater, where these samples were acquired, are incompatible with the cell replication limits currently known on Earth.

火星样本返回任务旨在取回美国宇航局毅力号火星车任务从火星杰泽罗陨石坑采集的密封岩石、风化层和大气样本。对于所有与生命相关的研究，有必要评估样本和火星上的水可用性。在第一个火星年内，毅力号获得了估计总质量为 355 克的岩石和风化层，以及 38 微摩尔的火星大气气体。利用毅力号火星车获得的现场观测结果，我们表明 Jezero 目前的环境条件允许硫酸盐、氯化物和高氯酸盐发生水合，偶尔会形成霜，以及日间大气-地表水交换每 m ² 0.5–10 g 水（假设气氛混合良好）。夜间，当温度降至190 K以下时，表面水分活度可超过0.5，这是细胞繁殖的最低限度。白天，当温度高于细胞复制极限 245 K 时，水分活度小于 0.02。采集这些样本的 Jezero 陨石坑表面的环境条件与地球上目前已知的细胞复制限制不相容。