Samples that are likely to contain evidence of past life on Mars must have been deposited when and where environments exhibited habitable conditions. Mars analog sites provide the opportunity to study how life could have exploited such habitable conditions. Acidic iron- and sulfur-rich streams are good geochemical analogues for the late Noachian and early Hesperian, periods of martian history where habitable conditions were widespread. Past life on Mars would have left behind fossilized microbial organic remains. These are often-sought diagnostic evidence, but they must be shielded from the harsh radiation flux at the martian surface and its deleterious effect on organic matter. One mechanism that promotes such preservation is burial, which raises questions about how organic biomarkers are influenced by the postburial effects of diagenesis. We investigated the kinetics of organic degradation in the subsurface of Mars. Natural mixtures of acidic iron- and sulfur-rich stream sediments and their associated microbial populations and remains were subjected to hydrous pyrolysis, which simulated the increased temperatures and pressures of burial alongside any promoted organic/mineral interactions. Calculations were made to extrapolate the observed changes over martian history. Our experiments indicate that low carbon contents, high water-to-rock ratios, and the presence of iron-rich minerals combine to provide unfavorable conditions for the preservation of soluble organic matter over the billions of years necessary to produce present-day organic records of late Noachian and early Hesperian life on Mars. Successful sample selection strategies must therefore consider the pre-, syn-, and postburial histories of sedimentary records on Mars and the balance between the production of biomass and the long-term preservation of organic biomarkers over geological time.

中文翻译：

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火星上早期生命的有机记录：铁，墓葬和动力学对保存的作用。

必须在环境表现出适宜居住条件的地点和地点存放可能包含火星前世证据的样品。火星模拟地点提供了研究生活如何利用这种宜居环境的机会。对于Noachian晚期和Hesperian早期（在火星历史时期，居住条件普遍存在），酸性富含铁和硫的流是很好的地球化学类似物。火星上的前世将遗留下化石微生物有机残留物。这些是经常寻找的诊断证据，但必须将其屏蔽在火星表面的苛刻辐射通量及其对有机物的有害影响。促进这种保存的一种机制是埋葬，这引发了有关成骨作用的后埋效应如何影响有机生物标记物的问题。我们研究了火星地下有机降解的动力学。酸性富含铁和硫的流沉积物的天然混合物及其相关的微生物种群和残留物经过水合热解，模拟了埋藏的温度和压力的增加以及任何促进的有机/矿物相互作用。进行了计算以推断火星历史上观察到的变化。我们的实验表明，低碳含量，高水岩石比和富铁矿物质的存在共同为提供可溶性有机物质的保存提供了不利条件，而这些条件是产生当今有机碳记录所必需的数十亿年。 Noachian和Hesperian早期在火星上的生活。因此，成功的样本选择策略必须考虑前置，同步，