Stability and transformation of interstellar amino acid precursors under simulated meteorite parent body conditions

Abstract Carbonaceous chondrites contain various organic compounds, including amino acids (AAs), which may have contributed to the emergence of life on Earth. However, their origin remains debated. Previous studies have shown that amino acid precursors (AAPs) can form in ice mantles of interstellar dust particles within molecular clouds. These AAs and AAPs could have been incorporated into small celestial bodies during the formation of the solar system. It has been suggested that interstellar AAs and AAPs underwent aqueous alteration due to heat and radiation from the decay of radioactive nuclides such as 26 Al. To test this hypothesis, we combined experiments simulating interstellar chemical reactions with those mimicking conditions inside meteorite parent bodies. We subjected AAs and interstellar AAP analogs to gamma irradiation in mixtures of formaldehyde (HCHO), methanol (CH 3 OH), ammonia (NH 3 ) and water (H 2 O). The resulting products were analyzed by cation-exchange high-performance liquid chromatography (HPLC) and gas chromatography-quadrupole mass spectrometry (GC/MS). Our results demonstrated that interstellar AAP analogs were more resistant to gamma irradiation than free AAs. Among the free AAs, glycine exhibited the highest stability, while AAs lacking α-hydrogens were more stable than their isomeric counterparts with α-hydrogens. Additionally, gamma irradiation not only degraded AAs but also generated new ones. The yield and diversity of newly formed AAs depended on the specific AAPs or AAs present in the system. Notably, systems containing interstellar AAP analogs produced a greater variety and higher quantity of AAs than those containing free AAs or none at all. These findings suggest that interstellar organic matter, including AAPs, delivered to asteroids could have contributed to the formation of the diverse organic compounds observed in asteroids and meteorites.