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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.
Special Issue: Evolution of molecules in space: From interstellar clouds to protoplanetary nebulae

Molecular and isotopic compositions of nitrogen-containing organic molecules formed during UV-irradiation of simulated interstellar ice

Haruna Sugahara, Yoshinori Takano, Shogo Tachibana, Iyo Sugawara, Yoshito Chikaraishi, Nanako O. Ogawa, Naohiko Ohkouchi, Akira Kouchi, Hisayoshi Yurimoto
Geochemical Journal, Vol. 53, No. , P. 5-20, 2019

ABSTRACT

Interstellar ice is a reaction site for molecular evolution. Gaseous molecules are frozen at low temperature (~10 K) to form ice mantles and the energy supplied by UV photons and other energy sources can lead to the synthesis of complex organics. Nitrogen-containing organic molecules are of special interest because of their biomolecular importance and their anomalous stable nitrogen isotopic composition (15N/14N) in the interstellar dust environment. Thus, N-containing organic molecules are the keys to understanding the evolution of organic molecules and the solar system. We focused on amino acids and amines in refractory organic residues formed from ultraviolet (UV) irradiated interstellar ice analogues. We developed analytical techniques that enable the identification of the small quantities of molecules formed from the simulated interstellar ice analogues. Organic residue analysis of the UV-irradiated H2O-CH3OH-NH3 ice showed the formation of three amines (methylamine, ethylamine and propylamine) and 11 amino acids (e.g., glycine, α-alanine, β-alanine, sarcosine, α-aminobutyric acid and β-aminoisobutyric acid). Furthermore, the compound-specific isotope analysis of nitrogen within the amino acids and the bulk organic film revealed that little isotopic fractionation occurred during formation in the simulated environment.

KEYWORDS

amines and amino acids, bulk and compound-specific nitrogen isotope analysis, ice mantle, simulated interstellar ice formation, UV-irradiation

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