Searching for biogenic trace gases on Mars using laboratory experiments and the ExoMars NOMAD instrument

使用实验室实验和 ExoMars NOMAD 仪器在火星上寻找生物微量气体

• 批准号: 1947432
• 金额: --
• 依托单位: The Open University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1947432
• 关键词: Searching; biogenic; trace; gases; Mars

Investigate the cocktail of trace gases produced by methanogens as biosignatures for potential life in the martian subsurfaceIdentify the spectral biosignature of these organismsSearch for these biosignatures in observations that will be made by the NOMAD spectrometer on the ExoMars Trace Gas OrbiterThe search for life beyond Earth remains one of the fundamental questions in science. Mars, our closest neighbour, represents a potential habitat for life, either in its ancient history or possibly even present-day, below the surface. Our understanding of possible habitable environments on Mars has increased over the last few years; evidence from evaporite deposits indicates that Mars had a water-rich evaporitic past [1, 2], and the discovery of Recurring Slope Lineae (RSL) suggests the presence of transient near-surface brines on modern-day Mars [3]. Thus the question arises: could life exist (or have existed) within these environments on Mars?Finding evidence of life on Mars requires an understanding of bio-signatures. At present, our best hope of detecting past or present life on Mars is through ultra-high precision measurements of trace gases relating to biological processes/life in the atmosphere.Atmospheres that display a disequilibrium are a potential indication of the action of complex processes including the presence of life. Gases such as volatile organic compounds (VOCs), some of which are unequivocally derived from organisms, could be an indicator of life; these types of gases will be detected by instruments such as the NOMAD instrument on-board the Trace Gas Orbiter (TGO, Patel is co-lead). A primary objective of NOMAD is to measure atmospheric VOCs, such as methane (among many others) [4].One possible explanation for the presence of methane on Mars is that it was (or is) being produced by methane-producing organisms (methanogens). If the source of methane on Mars is biogenic, it is imperative that we understand with great precision exactly what the emitted trace gas mixture of such activity would be in the context of Mars. It is currently known that biogenic processes result in a high ratio of methane to higher hydrocarbons, with abiogenic process resulting in a more balanced mixture of trace gases (e.g. [5]). Determining with high precision the exact ratios of gases produced under simulated martian conditions will be key to interpreting the origin of the gases, such as methane, that are observed on Mars - and crucially, as to whether the origin is biogenic or not.The overall aim of this proposal is to identify trace gas bio-signatures that could be used as evidence of life on Mars. The specific aims are as follows:Characterise the trace gases evolved from methanogenic Archaea under terrestrial conditionsRepeat the above under simulated Mars environmental conditions (atmospheric composition, pressure and temperature and nutrients)Determine a trace gas biosignature for methanogensApply this biosignature to data returned from the ExoMars Trace Gas Orbiter missionAssess whether the methane observed on Mars could be of biogenic origin

研究甲烷菌产生的微量气体混合物，作为火星地下潜在生命的生物特征识别这些生物的光谱特征在将由外火星微量气体轨道器上的NOMAD光谱仪进行的观测中寻找这些生物特征寻找地外生命仍然是科学中的基本问题之一。火星，我们最近的邻居，代表了一个潜在的生命栖息地，无论是在它的古代历史，甚至可能是现在，在地表以下。在过去的几年里，我们对火星上可能的宜居环境的了解有所增加；来自蒸发岩沉积物的证据表明，火星有一个富含水的蒸发过去[1,2]，而循环斜坡线（RSL）的发现表明，在现代火星[3]上存在短暂的近地表盐水。因此，问题出现了：生命可能存在（或曾经存在）在火星的这些环境中吗？在火星上寻找生命的证据需要对生物特征的理解。目前，我们探测火星上过去或现在生命的最大希望是通过超高精度测量与大气中生物过程/生命有关的微量气体。表现出不平衡的大气是复杂过程的潜在迹象，包括生命的存在。像挥发性有机化合物（VOCs）这样的气体，其中一些明确来自生物体，可能是生命的一个指标；这些类型的气体将由诸如微量气体轨道器（TGO，帕特尔联合领导）上的NOMAD仪器等仪器检测。NOMAD的一个主要目标是测量大气中的挥发性有机化合物，如甲烷（以及许多其他物质）。火星上存在甲烷的一种可能解释是，甲烷曾经（或正在）由产生甲烷的生物（产甲烷菌）产生。如果火星上甲烷的来源是生物的，那么我们就必须非常精确地了解在火星上这种活动所释放的微量气体混合物是什么。目前已知，生物成因过程导致甲烷与高级碳氢化合物的比例较高，而非生物成因过程导致微量气体的混合更为平衡（例如[5]）。高精度地确定在模拟火星条件下产生的气体的确切比例，将是解释在火星上观测到的甲烷等气体起源的关键，而且至关重要的是，确定这些气体的起源是否为生物成因。这项提议的总体目标是确定痕量气体的生物特征，这些特征可以作为火星上生命存在的证据。具体目标如下：表征在陆地条件下由产甲烷古菌演化而来的微量气体在模拟火星环境条件下（大气成分、压力、温度和营养物质）重复上述步骤，确定产甲烷菌的微量气体生物特征，将该生物特征应用于ExoMars痕量气体轨道器任务返回的数据，评估在火星上观测到的甲烷是否可能是生物成因的