Cranfield Health, Cranfield University, United Kingdom.
Astrobiology. 2011 Nov;11(9):839-46. doi: 10.1089/ast.2011.0662. Epub 2011 Oct 19.
The proposed ExoMars mission, due to launch in 2018, aims to look for evidence of extant and extinct life in martian rocks and regolith. Previous attempts to detect organic molecules of biological or abiotic origin on Mars have been unsuccessful, which may be attributable to destruction of these molecules by perchlorate salts during pyrolysis sample extraction techniques. Organic molecules can also be extracted and measured with solvent-based systems. The ExoMars payload includes the Life Marker Chip (LMC) instrument, capable of detecting biomarker molecules of extant and extinct Earth-like life in liquid extracts of martian samples with an antibody microarray assay. The aim of the work reported here was to investigate whether the presence of perchlorate salts, at levels similar to those at the NASA Phoenix landing site, would compromise the LMC extraction and detection method. To test this, we implemented an LMC-representative sample extraction process with an LMC-representative antibody assay and used these to extract and analyze a model sample that consisted of a Mars analog sample matrix (JSC Mars-1) spiked with a representative organic molecular target (pyrene, an example of abiotic meteoritic infall targets) in the presence of perchlorate salts. We found no significant change in immunoassay function when using pyrene standards with added perchlorate salts. When model samples spiked with perchlorate salts were subjected to an LMC-representative liquid extraction, immunoassays functioned in a liquid extract and detected extracted pyrene. For the same model sample matrix without perchlorate salts, we observed anomalous assay signals that coincided with yellow coloration of the extracts. This unexpected observation is being studied further. This initial study indicates that the presence of perchlorate salts, at levels similar to those detected at the NASA Phoenix landing site, is unlikely to prevent the LMC from extracting and detecting organic molecules from martian samples.
拟议的 ExoMars 任务将于 2018 年发射，旨在寻找火星岩石和风化层中现存和灭绝生命的证据。之前在火星上探测生物或非生物起源的有机分子的尝试都没有成功，这可能是由于在热解样品提取技术中，这些分子被高氯酸盐盐破坏所致。有机分子也可以用基于溶剂的系统提取和测量。ExoMars 有效载荷包括生命标志物芯片（LMC）仪器，该仪器能够使用抗体微阵列分析检测火星样本液体提取物中现存和灭绝的类地生命的生物标志物分子。这里报告的工作的目的是研究高氯酸盐盐的存在是否会影响 LMC 的提取和检测方法，其水平类似于美国宇航局凤凰着陆点的水平。为了测试这一点，我们用 LMC 代表性的抗体分析进行了 LMC 代表性的样品提取过程，并使用这些方法提取和分析了一个模型样品，该模型样品由火星模拟样本基质（JSC Mars-1）组成，其中掺入了代表有机分子靶标（芘，非生物陨石撞击目标的一个例子），并存在高氯酸盐盐。我们发现，当使用添加高氯酸盐盐的芘标准品时，免疫测定功能没有明显变化。当用高氯酸盐盐掺杂的模型样品进行 LMC 代表性的液体提取时，免疫测定在液体提取物中起作用，并检测到提取的芘。对于没有高氯酸盐盐的相同模型样品基质，我们观察到异常的分析信号，与提取物的黄色颜色一致。这一意外观察结果正在进一步研究中。这项初步研究表明，在类似于美国宇航局凤凰着陆点检测到的水平下，高氯酸盐盐的存在不太可能阻止 LMC 从火星样本中提取和检测有机分子。
