Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London , UK .
Astrobiology. 2018 May;18(5):556-570. doi: 10.1089/ast.2017.1744. Epub 2018 Feb 14.
Success of a future Mars Sample Return mission will depend on the correct choice of samples. Pyrolysis-FTIR can be employed as a triage instrument for Mars Sample Return. The technique can thermally dissociate minerals and organic matter for detection. Identification of certain mineral types can determine the habitability of the depositional environment, past or present, while detection of organic matter may suggest past or present habitation. In Mars' history, the Theiikian era represents an attractive target for life search missions and the acquisition of samples. The acidic and increasingly dry Theiikian may have been habitable and followed a lengthy neutral and wet period in Mars' history during which life could have originated and proliferated to achieve relatively abundant levels of biomass with a wide distribution. Moreover, the sulfate minerals produced in the Theiikian are also known to be good preservers of organic matter. We have used pyrolysis-FTIR and samples from a Mars analog ferrous acid stream with a thriving ecosystem to test the triage concept. Pyrolysis-FTIR identified those samples with the greatest probability of habitability and habitation. A three-tier scoring system was developed based on the detection of (i) organic signals, (ii) carbon dioxide and water, and (iii) sulfur dioxide. The presence of each component was given a score of A, B, or C depending on whether the substance had been detected, tentatively detected, or not detected, respectively. Single-step (for greatest possible sensitivity) or multistep (for more diagnostic data) pyrolysis-FTIR methods informed the assignments. The system allowed the highest-priority samples to be categorized as AAA (or A*AA if the organic signal was complex), while the lowest-priority samples could be categorized as CCC. Our methods provide a mechanism with which to rank samples and identify those that should take the highest priority for return to Earth during a Mars Sample Return mission. Key Words: Mars-Astrobiology-Search for Mars' organics-Infrared spectroscopy-Planetary habitability and biosignatures. Astrobiology 18, 556-570.
未来火星样本返回任务的成功将取决于正确选择样本。热裂解傅里叶变换红外光谱（Pyrolysis-FTIR）可用作火星样本返回的分类仪器。该技术可以对矿物质和有机物进行热解，以便进行检测。某些矿物类型的识别可以确定沉积环境的宜居性，无论是过去还是现在，而有机物的检测则可能表明过去或现在的居住情况。在火星的历史上，Theiikian 时代是生命探测任务和样本采集的一个有吸引力的目标。酸性且日益干燥的 Theiikian 可能曾经是宜居的，并且紧随火星历史上一段漫长的中性和湿润时期，生命可能起源于此，并在此大量繁殖，从而形成广泛分布的相对丰富的生物量。此外，Theiikian 中产生的硫酸盐矿物也被认为是有机物的良好保存者。我们使用热裂解傅里叶变换红外光谱和来自一个具有繁荣生态系统的火星类似亚铁酸流的样本，来测试分类概念。热裂解傅里叶变换红外光谱确定了那些最有可能具有宜居性和居住性的样本。根据检测到的（i）有机信号、（ii）二氧化碳和水以及（iii）二氧化硫，开发了一个三级评分系统。根据物质是否被检测到、初步检测到或未检测到，每种物质的存在分别被赋予 A、B 或 C 的分数。单步（为了尽可能提高灵敏度）或多步（为了获得更具诊断性的数据）热裂解傅里叶变换红外光谱方法为分配提供了信息。该系统允许将优先级最高的样本归类为 AAA（如果有机信号复杂，则为 A*AA），而优先级最低的样本可归类为 CCC。我们的方法提供了一种对样本进行排序的机制，并确定了在火星样本返回任务中应该优先返回地球的样本。关键词：火星-天体生物学-火星有机物搜索-红外光谱-行星宜居性和生物特征。天体生物学 18, 556-570。
