Amino acid precursors from possible interstellar media by heavy ion bombardment

A wide variety of organic compounds have been found in extraterrestrial bodies such as comets and meteorites. It was suggested that these organic compounds were originally formed in molecular clouds by cosmic rays and UV. We examined possible formation of amino acid-related compounds in such environments. A mixture of methanol, ammonia and water was irradiated with heavy ions (C, He, Ne, Ar) from HIMAC, or with gamma-rays from 60Co source. Hydrolysate of each product gave glycine as predominant amino acids. Energy yield (G-value) of glycine with heavy ions were higher than that with gamma-rays. A frozen mixture of methanol, ammonia and water (77 K) gave also amino acids after hydrolysis, whose energy yield was of the same order of magnitude. The present results suggest that amino acid precursors can be formed in molecular clouds from interstellar media even if they are frozen. (author)