Aponte José C, Woodward Hannah K, Abreu Neyda M, Elsila Jamie E, Dworkin Jason P
Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
Department of Chemistry, Catholic University of America, Washington, DC 20064, USA.
Meteorit Planet Sci. 2019 Feb;54(2):415-430. doi: 10.1111/maps.13216. Epub 2018 Nov 12.
The water-soluble organic compounds in carbonaceous chondrite meteorites constitute a record of the synthetic reactions occurring at the birth of the solar system and those taking place during parent body alteration and may have been important for the later origins and development of life on Earth. In this present work, we have developed a novel methodology for the simultaneous analysis of the molecular distribution, compound-specific δC and enantiomeric compositions of aliphatic monocarboxylic acids (MCA) extracted from the hot-water extracts of sixteen carbonaceous chondrites from CM, CR, CO, CV and CK groups. We observed high concentrations of meteoritic MCAs, with total carbon weight percentages which in some cases approached those of carbonates and insoluble organic matter. Moreover, we found that the concentration of MCAs in CR chondrites is higher than in the other meteorite groups, with acetic acid exhibiting the highest concentration in all samples. The abundance of MCAs decreased with increasing molecular weight and with increasing aqueous and/or thermal alteration experienced by the meteorite sample. The δC isotopic values of MCAs ranged from -52 to +27‰, and aside from an inverse relationship between δC value and carbon straight-chain length for C-C MCAs in Murchison, the C-isotopic values did not correlate with the number of carbon atoms per molecule. We also observed racemic compositions of 2-methylbutanoic acid in CM and CR chondrites. We used this novel analytical protocol and collective data to shed new light on the prebiotic origins of chondritic MCAs.
碳质球粒陨石中的水溶性有机化合物记录了太阳系诞生时发生的合成反应以及母体改变过程中发生的反应，可能对地球上生命的起源和发展具有重要意义。在本研究中，我们开发了一种新方法，用于同时分析从CM、CR、CO、CV和CK组的16颗碳质球粒陨石热水提取物中提取的脂肪族单羧酸（MCA）的分子分布、化合物特异性δC和对映体组成。我们观察到陨石MCA的浓度很高，其总碳重量百分比在某些情况下接近碳酸盐和不溶性有机物的百分比。此外，我们发现CR球粒陨石中MCA的浓度高于其他陨石组，所有样品中乙酸的浓度最高。MCA的丰度随着分子量的增加以及陨石样品经历的水相和/或热蚀变增加而降低。MCA的δC同位素值范围为-52至+27‰，除了默奇森陨石中C-C MCA的δC值与碳直链长度呈反比关系外，C同位素值与每分子的碳原子数无关。我们还在CM和CR球粒陨石中观察到2-甲基丁酸的外消旋组成。我们使用这种新的分析方法和收集的数据，为球粒陨石MCA的益生元起源提供了新的线索。
