We combine experimentally verified constraints on brine thermodynamics along with a global circulation model to develop a new extensive framework of brine stability on the surface and subsurface of Mars. Our work considers all major phase changes (i.e., evaporation, freezing, and boiling) and is consistent, regardless of brine composition, so it is applicable to any brine relevant to Mars. We find that equatorial regions typically have temperatures too high for stable brines, while high latitudes are susceptible to permanent freezing. In the subsurface, this trend is reversed, and equatorial regions are more favorable to brine stability, but only for the lowest water activities (and lowest eutectic temperatures). At locations where brines may be stable, we find that their lifetimes can be characterized by two regimes. Above a water activity of ∼0.6, brine duration is dominated by evaporation, lasting at most a few minutes per sol. Below a water activity of 0.6, brine duration is bound by freezing or boiling; such brines are potentially stable for up to several consecutive hours per sol. Our work suggests that brines should not be expected near or on the Martian surface, except for low eutectic water activity salts such as calcium or magnesium perchlorate or chlorate, and their (meta)stability on the surface would require contact with atmospheric water vapor or local ice deposits.

我们将经过实验验证的盐水热力学约束与全球环流模型相结合，开发了一个新的火星表面和地下盐水稳定性的广泛框架。我们的工作考虑了所有主要的相变（即蒸发、冷冻和沸腾），并且无论盐水成分如何，都是一致的，因此它适用于与火星相关的任何盐水。我们发现，赤道地区的温度通常对于稳定的盐水来说过高，而高纬度地区则容易遭受永久冻结。在地下，这种趋势相反，赤道地区更有利于盐水稳定性，但仅限于最低的水活动（和最低的共晶温度）。在盐水可能稳定的地方，我们发现它们的寿命可以由两种状态来表征。水分活度高于 ∼0.6 时，盐水的持续时间主要是蒸发，每个溶胶最多持续几分钟。水分活度低于 0.6 时，盐水的持续时间受到冷冻或沸腾的限制；这种盐水每个溶胶可能连续几个小时保持稳定。我们的工作表明，除了低共晶水活度盐（例如高氯酸钙或镁或高氯酸盐或氯酸盐）之外，不应期望在火星表面附近或表面存在盐水，并且它们在表面的（亚）稳定性需要与大气水蒸气或当地的水蒸气接触。冰沉积物。