The origin and evolution of organic matter in the solar system: the amino acid content ofinterstellar ices and the primitive carbonaceous chondrite ParisZ. Martins1, P. Modica2,3, C. Meinert4, B. Zanda5, L.L.S. d’Hendecourt2,61ESE, Imperial College London, SW7 2AZ, UK; 2CNRS, Université Paris XI, Institut d’Astrophysique Spatiale, ‘‘Astrochimieet Origines’’, 91405 Orsay Cedex, France; 3Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E),
CNRS/Université d’Orléans, 45071 Orléans, France; 4Université Côte d’Azur, Institut de Chimie de Nice, UMR 7272 CNRS,06108 Nice, France ; 5Muséum d’Histoire Naturelle, CNRS, 75005, Paris, France; 6Equipe ASTRO, Laboratoire de Physiquedes Interactions Ioniques et Moléculaires, UMR CNRS 7345, Centre de Saint Jérôme - case 252, Université d'Aix-Marseille,
13397 Marseille, France.
The organic matter present in carbonaceous chondrites reflects the physical and chemical reactions that occurred in theinterstellar medium, solar nebula, and/or on their parent bodies [1, 2]. It is possible that organic matter synthetized in the initialmolecular cloud survived the protosolar disk phase, was incorporated into planetesimals that would later form comets andasteroids, and finally experienced (aqueous or thermal) alteration on the parent body of carbonaceous meteorites [3]. Therefore,
laboratory produced interstellar ice analogues, as well as primitive carbonaceous meteorites are precious samples that allow
studying key steps into the origin and evolution of organic matter in the solar system. Amino acids, as well as many othercomplex organic molecules may be formed from ultraviolet irradiation and thermo-processing of interstellar icy grains,accreted into the parent bodies of meteorites [4-6], and finally witness aqueous alteration, which seems to influence theirdistribution and relative abundance [7-11].
In this study, we have analysed the amino acid content of laboratory organic residues produced by simulated photo- andthermo-processing of icy mixtures [12]. These have been considered as analogues for the organic material synthetized ininterstellar or circumstellar icy grains [13-17]. We have also analysed the amino acid content of one of the most primitive CM
chondrites, the Paris meteorite [6]. This meteorite is one of the least aqueously altered CM chondrites analysed to date [18-23].
Our results show that Paris has the lowest relative abundance of β-alanine/glycine (0.15 ± 0.02), which is the smallest βalanine/glycine ratio observed in CM chondrites [6]. The relative abundance of β-alanine/glycine increases with increasing
aqueous alteration, from the CM2.7/2.8 Paris to the CM2.0 MET01070. The isovaline detected in the Paris meteorite isracemic (corrected D/L = 1.03). This is a good indication that aqueous alteration may be responsible for extending an initial Lenantiomeric excess (Lee) of isovaline [6], but not responsible for creating an isovaline asymmetry [24-31]. Furthermore, ourdata shows that the laboratory organic residues have relative distributions of 4-carbon amino acids in agreement with that of
the Paris meteorite, and that the relative β-alanine/glycine ratio is similar to that of Paris [12]. The analysis of the solubleorganic content of carbonaceous meteorites and laboratory organic residues analogue to interstellar ices helps to increase ourknowledge on the origin and evolution of organic matter in the solar system. It also shows that interstellar ice evolution may be
an important source for organic matter in the solar system. This helps to build links between the different contributions for theformation of complex molecules, i.e. interstellar precursors, solar nebula, the incorporation in asteroids, and finally meteorite
parent body alteration.
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