Pathways to Meteoritic Glycine and Methylamine
Pathways to Meteoritic Glycine and Methylamine
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DOI：
10.1021/acsearthspacechem.6b00014
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发表时间：
2017-03-01
影响因子：
3.4
通讯作者：
Dworkin, Jason P.
中科院分区：
文献类型：
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作者：
Aponte, Jose C.;Elsila, Jamie E.;Dworkin, Jason P.
甘氨酸和甲胺是陨石水溶性有机化合物，可以深入了解太阳系形成之前、期间和之后发生的过程。甘氨酸和甲胺以及它们的许多潜在的合成前体已经通过观测、实验室实验和建模在天体物理环境中进行了研究。尽管有这些研究，但导致它们在陨石中出现的合成机制仍然知之甚少。典型的C-13同位素值（VC）的陨石甘氨酸和甲胺是C-13富集相对于他们的地面对应物，因此，分析其稳定的碳同位素组成（C-13/C-12）不仅可以用来评估地球的陨石污染，但也提供信息，其合成路线内的母体。在这里，我们研究潜在的合成路线的甘氨酸和甲胺从一组常见的前体存在于碳质球粒陨石，从实验室分析的数据，充分研究CM 2默奇森陨石。在碳质方解石中发现的甘氨酸和甲胺的起源可能有几种合成机制，这些机制的普遍性在很大程度上取决于（a）前体分子的分子丰度和（B）母体内发生的加工水平（水和热）。在这项工作中，我们的目标也是上下文的气相反应和辐照冰粒化学合成这些物种通过母体过程的现有知识。我们的陨石甘氨酸和甲胺从简单的物种起源的各种机制的评估表明，仍然需要做什么工作来评估的丰度和同位素组成的简单的前体分子从碳质方解石，以及母体过程对这些丰度和同位素组成的影响。这里提出的分析与所示的测量相结合，将有助于更好地解释定量分析的反应速率，分子稳定性和分布的有机产品从实验室模拟的星际冰，天文观测和理论建模。
Glycine and methylamine are meteoritic water-soluble organic compounds that provide insights into the processes that occurred before, during, and after the formation of the Solar System. Both glycine and methylamine and many of their potential synthetic precursors have been studied in astrophysical environments via observations, laboratory experiments, and modeling. Despite these studies, the synthetic mechanisms for their formation leading to their occurrence in meteorites remain poorly understood. Typical C-13-isotopic values (VC) of meteoritic glycine and methylamine are C-13-enriched relative to their terrestrial counterparts; thus, analyses of their stable carbon isotopic compositions (C-13/C-12) may be used not only to assess terrestrial contamination in meteorites but also to provide information about their synthetic routes inside the parent body. Here, we examine potential synthetic routes of glycine and methylamine from a common set of precursors present in carbonaceous chondrite meteorites, using data from laboratory analyses of the well-studied CM2 Murchison meteorite. Several synthetic mechanisms for the origins of glycine and methylamine found in carbonaceous chondrites may be possible, and the prevalence of these mechanisms will largely depend on (a) the molecular abundance of the precursor molecules and (b) the levels of processing (aqueous and thermal) that occurred inside the parent body. In this work, we also aim to contextualize the current knowledge about gas-phase reactions and irradiated ice grain chemistry for the synthesis of these species through parent body processes. Our evaluation of various mechanisms for the origins of meteoritic glycine and methylamine from simple species shows what work is still needed to evaluate both the abundances and isotopic compositions of simpler precursor molecules from carbonaceous chondrites as well as the effects of parent body processes on those abundances and isotopic compositions. The analyses presented here combined with the indicated measurements will aid a better interpretation of quantitative analysis of reaction rates, molecular stability, and distribution of organic products from laboratory simulations of interstellar ices, astronomical observations, and theoretical modeling.