The Amino Acid Distribution in Laboratory Analogs of Extraterrestrial Organic Matter: A Comparison to CM Chondrites

Laboratory experiments that simulate the photo- and thermo-chemistry of extraterrestrial ices always lead to the formation of semi-refractory organic residues. These residues can be considered as laboratory analogs for the primitive organic matter incorporated into comets and asteroids. Many specific organic molecules have been detected in them. Here we focus on amino acids because of their possible relevance to further prebiotic chemistry on Earth as well as in other solar system bodies. We compare the amino acid content and distribution measured in organic residues produced in our photochemical experiments to those observed in various CM chondrites presenting an increasing degree of aqueous alteration, a process that is thought to impact amino acid chemistry. We find that the amino acid profile of our residues shows similarities with that of the least aqueously altered CM chondrites. In particular, the beta-alanine to glycine ratio is comparable to the one measured in the Paris meteorite, a minimally altered CM chondrite, and matches the trend followed by other CM chondrites with different degrees of aqueous alteration. Additionally, the relative abundances of alpha-, beta-, and gamma-amino acids in one of our residues are similar to those of the least altered CM chondrites. These results support the idea of a general formation process for amino acids from photo- and thermo-processing of icy grains as an important source for the inventory of amino acids in the early solar system.