Abstract The payload of Mars 2020 space mission includes a deep UV resonance Raman and fluorescence spectrometer SHERLOC dedicated to the detection of luminescence and Raman signal of condensed carbon and aromatic organics that could potentially be biosignatures. Among minerals detected on Mars surface, phyllosilicates exhibit a strong affinity to organic molecules, including nucleotides, which adsorption mechanisms onto clay minerals have been well documented, whilst there is a lack of an overview of Raman studies of organics adsorbed onto phyllosilicates. Here, we used a deep UV resonant Raman setup to track down the signature of the nucleotide desoxyguanosine-5′-monophosphate (dGMP) adsorbed onto selected minerals, pyrophyllite, chlorite, nontronite and montmorillonite. Excitation with a 244 nm laser indeed avoids luminescence of natural phyllosilicates and enhances the Raman signal of the organic molecule chosen here as a model biosignature. However, the deep UV energy of the laser focused onto the samples may induce severe photo-damage to the organic compound without adequate precaution. We used the Raman signature of dGMP to characterize deep UV effect after an irradiation of several minutes (8–260 mJ) until a stable spectroscopic signal is detected and could show that it is sensitive to minute amount of dGMP and adsorption mechanism. The effect of widespread oxidants such as perchlorate on the Martian surface is also investigated here because of potential implication in the degradation of nucleotides under UV irradiation. In this study we also discuss the strategy for the detection and preservation of adsorbed biomolecules onto clay surfaces.

中文翻译：

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通过紫外共振拉曼光谱检测吸附在粘土上的核苷酸：迈向在火星上寻找生物特征的一步

摘要 Mars 2020 太空任务的有效载荷包括深紫外共振拉曼和荧光光谱仪 SHERLOC，专门用于检测可能是生物特征的凝聚碳和芳香族有机物的发光和拉曼信号。在火星表面检测到的矿物中，页硅酸盐对有机分子（包括核苷酸）表现出很强的亲和力，其在粘土矿物上的吸附机制已得到充分证明，但缺乏对吸附在页硅酸盐上的有机物的拉曼研究的概述。在这里，我们使用深紫外共振拉曼装置来追踪吸附在选定矿物、叶蜡石、绿泥石、绿脱石和蒙脱石上的核苷酸脱氧鸟苷-5'-单磷酸酯 (dGMP) 的特征。用 244 nm 激光激发确实避免了天然页硅酸盐的发光，并增强了此处选择作为模型生物特征的有机分子的拉曼信号。然而，如果没有足够的预防措施，聚焦到样品上的激光的深紫外能量可能会对有机化合物造成严重的光损伤。我们使用 dGMP 的拉曼特征来表征经过几分钟 (8-260 mJ) 照射后的深紫外效应，直到检测到稳定的光谱信号，并且可以表明它对微量 dGMP 和吸附机制敏感。由于在紫外线照射下核苷酸降解的潜在影响，这里还研究了广泛存在的氧化剂（如高氯酸盐）对火星表面的影响。