¹Sanchez, Juan A.,²Reddy, Vishnu,³Thirouin, Audrey,⁴Bottke, William F.,³Kareta, Theodore,⁵De Florio, Mario,⁶Sharkey, Benjamin N. L.,²Battle, Adam,²Cantillo, David C.,¹Pearson, Neil
The Planetary Science Journal 5, 131 Open Access Link to Article [DOI 10.3847/PSJ/ad445f]
¹Planetary Science Institute, 1700 East Fort Lowell Road, Tucson, 85719, AZ, United States
²Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, 85721-0092, AZ, United States
³Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, 86004, AZ, United States
⁴Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, 80302, CO, United States
⁵Division of Applied Mathematics, Brown University, 170 Hope Street, Providence, 02906, RI, United States
⁶Department of Astronomy, University of Maryl, 4296 Stadium Drive PSC (Building 415), Room 1113, College Park, 20742-2421, MD, United States

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Y.Y. He et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.09.035]
¹Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Muséum
Copyright Elsevier

Carbonaceous chondrites contain amino acids, with variable abundances and isotope compositions between and within carbonaceous chondrites. The parent body processes, and the presence of clay minerals may explain those differences. Here, we experimentally investigate the evolution of 6 amino acids (glycine, β-alanine, α-alanine, 2-aminoisobutyric acid, γ-aminobutyric acid, and isovaline) exposed to hydrothermal conditions in the presence or absence of silicates. We determined the chemical nature and isotopic composition of the organic compounds of the soluble and solid fractions of the residues using X-ray diffraction, spectroscopy, and mass-spectrometry methods. Glycine and α-alanine exhibit a rather high stability, which is consistent with the measured abundances of α-alanine and glycine in chondrites having experienced various degrees of aqueous alteration. In the meantime, the evolution of β-alanine under hydrothermal conditions leads to the formation of a new compound, which likely results from the decarboxylation and deamination of β-alanine followed by recombination. More than 95 % of γ-ABA was transformed into 2-pyrrolidione though self-cyclization during the aqueous alteration. The solid residues of the experiments conducted in the presence of clay minerals contain organic material, with abundances varying depending on the amino acid used for the experiments (TOC isovaline > 2-aminoisobutyric acid > γ-aminobutyric acid > glycine > α-alanine > β-alanine). Clay minerals thus preferentially trap branched amino acids over chained amino acids, likely within their interlayer spaces as suggested by XRD data. The δ¹³C values of amino acids have not changed significantly during the experiments, even with the presence of silicates. Thus, the δ¹³C values of amino acids reported in CR and CM chondrites likely relate to synthetic conditions or the origin of their precursors (i.e. inherited from the pre-accretion processes).