研究人员提出了一个混合模型，涉及由冻—融循环驱动的自下而上和自上而下的过程。冻结导致地表降水中酸性流体的低温浓缩，沉淀的酸性流体的低温浓度，促进了低温下的快速化学风化。冰冻作用导致渗流水甚至含有溶解离子的地下水向上迁移，导致离子在近地表环境中积累。
蒸发会使得盐沉淀，但在解冻期间，沥滤会使得氯化物与硫酸盐分离。因此，冻—融循环可以使地表的硫酸盐富集。虽然冻—融通常被理解为物理风化的一种机制，但研究人员认为它是火星化学风化的一个基本方面。
据了解，机遇号探测器在Meridiani平原14年的地表探测任务中，探索到富含硫酸盐的沉积岩，为通过遥感探测到火星上大量的硫酸盐沉积物提供了宝贵的窗口。现有的解释火星硫酸盐形成的模式，通常可以被描述为自下而上的地下水驱动的playa环境或自上而下的冰冷化学风化环境。
附：英文原文
Title: Freeze-thaw cycles drove chemical weathering and enriched sulfates in the Burns formation at Meridiani, Mars
Author: Jiacheng Liu, Joseph R. Michalski, Wenyuan Gao, Christian Schrder, Yi-Liang Li
Issue&Volume: 2024-01-19
Abstract: Sulfate-rich sedimentary rocks explored by the Opportunity rover during its 14-year surface mission at Meridiani Planum provide an invaluable window into the thousands of sulfate deposits detected on Mars via remote sensing. Existing models explaining the formation of martian sulfates can be generally described as either bottom-up, groundwater-driven playa settings or top-down icy chemical weathering environments. Here, we propose a hybrid model involving both bottom-up and top-down processes driven by freeze-thaw cycles. Freezing leads to cryo-concentration of acidic fluids from precipitations at the surface, facilitating rapid chemical weathering despite low temperatures. Cryosuction causes the upward migration of vadose water and even groundwater with dissolved ions, resulting in the accumulation of ions in near-surface environments. Evaporation precipitates salts, but leaching separates chlorides from sulfates during the thawing period. Freeze-thaw cycles, therefore, can enrich sulfates at the surface. While freeze-thaw is more commonly understood as a mechanism of physical weathering, we suggest that it is a fundamental aspect of chemical weathering on Mars.
DOI: adi1805
Source: https://www.science.org/doi/10.1126/sciadv.adi1805