Carbon isotope evidence for the substrates and mechanisms of prebiotic synthesis in the early solar system

Meteorites contain prebiotic, bio-relevant organic compounds including amino acids. Their syntheses could result from diverse sources and mechanisms and provide a window on the conditions and materials present in the early solar system. Here we constrain alanine's synthetic history in the Murchison meteorite using site-specific C-13/C-12 measurements, reported relative to the VPDB standard. The delta(CVPDB)-C-13 values of -29 +/- 10 parts per thousand, 142 +/- 20 parts per thousand, and-36 +/- 20 parts per thousand for the carboxyl, amine-bound, and methyl carbons, respectively, are consistent with Strecker synthesis of interstellar-medium-derived aldehydes, ammonia, and low-delta C-13 nebular or interstellar-medium-derived CN. We report experimentally measured isotope effects associated with Strecker synthesis, and use them to constrain the delta C-13 values of the alanine precursors, which we then use to construct a mod-el that predicts the molecular-average delta C-13 values of 19 other organic compounds of prebiotic significance found in Murchison if they were made by our proposed synthetic network. Most of these predictions agree with previous measurements, suggesting that interstellar-medium-derived aldehydes and nebular and/or pre-solar CN could have served as substrates for synthesis of a wide range of prebiotic compounds in the early solar system. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Meteorites contain bio-relevant organic compounds, with alanine's synthetic history influenced by interstellar and interstellar-medium sources. Predictive models suggest a specific synthetic network may have produced a variety of prebiotic compounds in the early solar system.