Amino acids formed from the UV/EUV irradiation of inorganic ices of astrophysical interest

Abstract

An experiment where a H 2O:CO 2:NH 3 = 1:1:1 ice mixture was irradiated using the ultraviolet/extreme ultraviolet (UV/EUV) light provided by a synchrotron beam in the broad 4–20 eV (62–310 nm) range at 16 K is presented here. The main originalities of the present work are the composition of the starting ice mixture, since it did not contain any organic compound, in particular no methanol (CH 3OH) nor methane (CH 4) as for previous similar experiments, and the photon energy range. Several amino acids were produced: nine were identified of which seven could be quantified, and some others tentatively identified using high-performance liquid chromatography (HPLC). This result shows that it is possible to form complex organics such as amino acids from the irradiation of ice mixtures containing C-, H-, O- and N-atom bearing compounds, whatever the organic/inorganic nature of these compounds. Only the distribution of the formed amino acids is different from previous experiments. This discrepancy may be due to the starting mixture composition and/or the different energy range used for the irradiation. These two parameters are discussed in regard of their implications for the formation of amino acids in the laboratory and in astrophysical environments.