Ancient veins of calcium sulfate minerals (anhydrite, bassanite, and gypsum) deposited by subsurface aqueous fluids crosscut fluviolacustrine sedimentary rocks at multiple localities on Mars. Although these veins have been considered an attractive target for astrobiological investigation, their potential to preserve biosignatures is poorly understood. Here, we report the presence of biogenic authigenic pyrite in a fibrous gypsum vein of probable Cenozoic emplacement age from Permian lacustrine rocks in Northwest England. Pyrite occurs at the vein margins and displays a complex interfingering boundary with the surrounding gypsum suggestive of replacive authigenic growth. Gypsum-entombed carbonaceous material of probable organic origin was also identified by Raman spectroscopic microscopy in close proximity to the pyrite. Spatially resolved ion microprobe (SIMS) measurements reveal that the pyrite sulfur isotope composition is consistently very light (δ³⁴S_VCDT = -30.7‰). Comparison with the sulfate in the vein gypsum (δ³⁴S_VCDT = +8.5‰) indicates a fractionation too large to be explained by nonbiological (thermochemical) sulfate reduction. We infer that the pyrite was precipitated by microorganisms coupling the reduction of vein-derived sulfate with the oxidation of wall-derived organic matter. This is the first evidence that such veins can incorporate biosignatures that remain stable over geological time, which could be detected in samples returned from Mars.

中文翻译：

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火星模拟硫酸钙静脉记录古代地下生命的证据

由地下含水流体沉积的硫酸钙矿物（硬石膏、贝桑石和石膏）的古老矿脉横切了火星上多个地点的河湖沉积岩。尽管这些静脉被认为是天体生物学研究的一个有吸引力的目标，但它们保存生物特征的潜力却知之甚少。在这里，我们报告了英格兰西北部二叠纪湖相岩石可能的新生代侵位时代的纤维状石膏脉中存在生物自生黄铁矿。黄铁矿出现在矿脉边缘，并与周围的石膏显示出复杂的干涉边界，暗示着替代自生生长。还通过拉曼光谱显微镜在靠近黄铁矿的地方鉴定了可能是有机来源的石膏埋藏的碳质材料。³⁴ S _VCDT  = -30.7‰）。与静脉石膏中的硫酸盐 (δ ³⁴ S _VCDT  = +8.5‰) 的比较表明分馏太大，无法用非生物（热化学）硫酸盐还原来解释。我们推断黄铁矿是由微生物将脉源硫酸盐的还原与壁源有机物的氧化相结合而沉淀的。这是第一个证据表明，这种静脉可以包含在地质时期内保持稳定的生物特征，这可以在从火星返回的样本中检测到。