Molecular distribution, 13C‐isotope, and enantiomeric compositions of carbonaceous chondrite monocarboxylic acids

Jose C. APONTE1,2*, Hannah K. WOODWARD2,3, Neyda M. ABREU4, Jamie E. ELSILA1, and Jason P. DWORKIN1
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13216 ]
1Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
2Department of Chemistry, Catholic University of America, Washington, DC 20064, USA
3Department of Chemistry, University of Reading, Reading RG6 6UA, UK
4Earth Science Program, Pennsylvania State University—Du Bois Campus, Du Bois, Pennsylvania 15801, USA
Published by arrangement with John Wiley & Sons

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 δ13C, and enantiomeric compositions of aliphatic monocarboxylic acids (MCA) extracted from the hot‐water extracts of 16 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 δ13C isotopic values of MCAs ranged from −52 to +27‰, and aside from an inverse relationship between δ13C value and carbon straight‐chain length for C3–C6 MCAs in Murchison, the 13C‐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.

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