Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2024 Jul 20;935:173442. doi: 10.1016/j.scitotenv.2024.173442. Epub 2024 May 22.
Covered by vast eolian landforms, gravel deposits, and playas, the worldwide typical evaporite deposit land, Qaidam Basin, in northwestern China is analogous to early Mars when the aridification process had lasted for millions of years since the end of a wetter climate. This study aims to investigate the chemical and isotopic characteristics of waters in an evaporite-rich environment, as well as the habitable conditions therein, that have undergone a transformation similar to early Mars. In May 2023, a total of 26 water samples were collected across the representative central axis of a longitudinal aridity gradient in the Qaidam Basin, including categories of meteoric water, freshwater, standing water accumulated after precipitation, salty lacustrine water, and hypersaline brines to inspect compounds made up of carbon, nitrogen, phosphorus, sulfur, halogen, and metallic elements. As evaporation intensified, the salt types transformed from HCO-Ca·Na to Cl·SO-Na or ClMg. The dominance of carbonate will gradually be replaced by sulfate and chloride, leaving much more dilute and less detectable contents. The presence of trace ClO, ClO, ClO, and BrO was confirmed in a few of the sampled Qaidam waters, indicating the preservation of oxyhalides in waters within an arid region and possibly the presence of relevant microbial enzymes. The isotopes of water, carbonaceous, and nitrogenous compounds provide valuable references for either abiogenic or biogenic signatures. With undetectable amount, phosphorus was found to be the limiting nutrient in evaporative aquatic environments but not necessarily antibiosignatures. Overall, these results suggest that the paleo-lacustrine environments on Mars are more likely to preserve biosignatures if they feature the dominance of carbonate minerals, bioavailable nitrate, phosphorus, and organic carbon, the presence of thermodynamically unstable oxyhalides, and isotope ratios that point to the involvement of biological activity.
被广泛的风成地貌、砾石沉积物和盐湖覆盖的柴达木盆地是中国西北部的世界典型蒸发岩矿床地，与早期火星类似，在经历了数百万年的干旱化过程后，气候变得更加干燥。本研究旨在调查富含蒸发岩环境中的水的化学和同位素特征，以及其中发生类似于早期火星的转化的宜居条件。2023 年 5 月，在柴达木盆地纵向干旱梯度的代表性中轴线上共采集了 26 个水样，包括大气水、淡水、降水后积累的静水、咸水湖泊水和过咸卤水等类别，以检测由碳、氮、磷、硫、卤素和金属元素组成的化合物。随着蒸发的加剧，盐的类型从 HCO-Ca·Na 转变为 Cl·SO-Na 或 ClMg。碳酸盐的优势将逐渐被硫酸盐和氯化物取代，留下更稀释和更难检测的含量。在一些采自柴达木的水样中，确证了痕量 ClO、ClO、ClO 和 BrO 的存在，这表明在干旱地区的水中保存了含氧卤化物，并且可能存在相关的微生物酶。水、碳质和氮质化合物的同位素为非生物或生物特征提供了有价值的参考。尽管磷的含量难以检测，但在蒸发水生环境中，磷被发现是限制营养物质，但不一定是反生物特征的元素。总的来说，如果火星上的古湖泊环境具有碳酸盐矿物、生物可利用的硝酸盐、磷和有机碳的优势，存在热力学不稳定的含氧卤化物，以及指向生物活动参与的同位素比值，那么它们更有可能保存生物特征。
