Experimental Investigation of Potential Pathways for Abiotic Organic Synthesis on the Early Earth

几十年来，科学家们一直在探索地球上最古老的岩石，以寻找早期生命的痕迹。关于这些古老岩石含有生命证据的说法在很大程度上依赖于对岩石中发现的碳化合物的同位素组成、化学结构和形态的解释。然而，最近，一些最古老的岩石中碳的生物来源受到了质疑，并提出了化合物的另一种非生物来源。解决这些化合物的来源对于确定生命起源的时间，以及了解地球上最早的生命形式的分布和特征具有重要意义。为了弄清古岩中碳的来源，拟议的研究是一项实验室实验调查，将更清楚地确定地质系统中非生物过程形成的有机碳化合物的特征。区分古岩中生物来源的碳化合物和可能具有非生物来源的碳化合物，需要更清楚地定义允许发生非生物有机合成的条件，并更好地表征在这些条件下产生的化合物的分子和同位素组成。因此，拟议的研究将通过一系列的实验室实验来探索非生物有机合成的反应途径。实验将集中在非生物合成的两条反应途径(甲烷聚合和菱铁矿分解)上，这两条反应途径已被用作在古代岩石中形成还原碳化合物的途径，但尚未得到很好的实验表征。此外，还将进行实验，以探索在地质系统中经常用于非生物合成的费托合成反应的产物在变质加热过程中是否可以转化为在古代岩石(例如干酪根、石墨)中发现的还原碳化合物类型。预计这项研究将有助于确定早期地球上非生物有机质来源的潜在贡献，并有助于解释地球上最古老的岩石中还原碳的来源。

For many decades, scientists have been exploring the Earth's oldest rocks for traces of early life. Claims that these ancient rocks contain evidence for life have largely relied on interpretations of the isotopic composition, chemical structure, and morphology of carbon compounds found in the rocks. Recently, however, the biological origin of carbon in several of the oldest rocks has been called into question, and an alternative non-biological (abiotic) origin of the compounds proposed. Resolving the source of these compounds has significant implications for determining the timing of the origin of life, and for understanding the distribution and characteristics of the earliest lifeforms on our planet. In order to clarify the source of carbon in ancient rocks, the proposed research is a laboratory experimental investigation that will more clearly define the characteristics of organic carbon compounds formed by abiotic processes in geologic systems.Distinguishing biologically derived carbon compounds in ancient rocks from those that may have a non-biological origin requires clearer definition of conditions that allow abiotic organic synthesis to occur and better characterization of the molecular and isotopic composition of compounds that are produced under those conditions. Accordingly, the proposed research will investigate reaction pathways for abiotic organic synthesis through a series of laboratory experiments. Experiments will focus on two reaction pathways for abiotic synthesis (polymerization of methane and siderite decomposition) that have been invoked as pathways for formation of reduced carbon compounds in ancient rocks, but that have not been well characterized experimentally. In addition, experiments will be conducted to explore whether products of Fischer-Tropsch synthesis, a reaction often invoked for abiotic synthesis in geologic systems, can be converted to the type of reduced carbon compounds found in ancient rocks (e.g., kerogen, graphite) during metamorphic heating. It is anticipated that the research will help to define the potential contribution of abiotic sources of organic matter on the early Earth and aid in the interpretation of the origin of reduced carbon in the Earth's oldest rocks.