Biosignature Detection at an Arctic Analog to Europa
Biosignature Detection at an Arctic Analog to Europa
复制标题
DOI：
10.1089/ast.2010.0579
复制
发表时间：
2012-02-01
期刊：
影响因子：
4.2
通讯作者：
Templeton, A. S.
中科院分区：
文献类型：
--
作者：
Gleeson, Damhnait F.;Pappalardo, R. T.;Templeton, A. S.
木卫二冰壳下存在海洋的令人信服的证据使其成为天体生物学研究的高度优先事项。未来对这颗卫星冰冷表面的探测任务将询问可能富含硫的物质，以寻找移动的冰或部分融化携带到表面的生命存在的潜在迹象。然而，在寒冷、富含硫的条件下产生和保存生物特征的潜力以前没有被研究过，因为地球上没有合适的环境可供研究。在这里，我们描述了一系列的生物特征的表征内潜在的类似硫矿床从北极冰川的表面在博鲁普峡湾通行证，以评估是否产生和保存在这些存款的微生物活动的证据。光学和电子显微镜显示微生物和细胞外物质。元素硫（S-0），在现场样品中的主要矿物学，是作为菱形和针状矿物颗粒和球形矿物聚集体，通常观察到与胞外聚合物。正交α-硫代表S-0的稳定形式，而单斜（针状）γ-硫形式的蔷薇辉石是亚稳定的，以前与硫化物氧化微生物群落有关。扫描透射电子显微镜显示矿物质沉积在细胞和细胞外材料的亚微米尺寸，针状晶体的形式。X射线衍射测量提供了支持的证据，存在的一个小组成部分的蔷薇辉石。红外光谱揭示了博尔普硫矿床中百万分之一级的有机物和生物分子如蛋白质和脂肪酸的有机官能团诊断。有机组分低于拉曼光谱的检测限，其由硫峰主导。这些综合研究表明，硫矿床可能含有可识别的生物特征，可以在低温条件下稳定和保存。博鲁普峡湾通道是一个有用的测试场，用于测试与木卫二未来天体生物学探索相关的仪器和技术。
The compelling evidence for an ocean beneath the ice shell of Europa makes it a high priority for astrobiological investigations. Future missions to the icy surface of this moon will query the plausibly sulfur-rich materials for potential indications of the presence of life carried to the surface by mobile ice or partial melt. However, the potential for generation and preservation of biosignatures under cold, sulfur-rich conditions has not previously been investigated, as there have not been suitable environments on Earth to study. Here, we describe the characterization of a range of biosignatures within potentially analogous sulfur deposits from the surface of an Arctic glacier at Borup Fiord Pass to evaluate whether evidence for microbial activities is produced and preserved within these deposits. Optical and electron microscopy revealed microorganisms and extracellular materials. Elemental sulfur (S-0), the dominant mineralogy within field samples, is present as rhombic and needle-shaped mineral grains and spherical mineral aggregates, commonly observed in association with extracellular polymeric substances. Orthorhombic alpha-sulfur represents the stable form of S-0, whereas the monoclinic (needle-shaped) gamma-sulfur form rosickyite is metastable and has previously been associated with sulfide-oxidizing microbial communities. Scanning transmission electron microscopy showed mineral deposition on cellular and extracellular materials in the form of submicron-sized, needle-shaped crystals. X-ray diffraction measurements supply supporting evidence for the presence of a minor component of rosickyite. Infrared spectroscopy revealed parts-per-million level organics in the Borup sulfur deposits and organic functional groups diagnostic of biomolecules such as proteins and fatty acids. Organic components are below the detection limit for Raman spectra, which were dominated by sulfur peaks. These combined investigations indicate that sulfur mineral deposits may contain identifiable biosignatures that can be stabilized and preserved under low-temperature conditions. Borup Fiord Pass represents a useful testing ground for instruments and techniques relevant to future astrobiological exploration at Europa.