Synthesis of Amino Acid Precursors from Simulated Interstellar Media by High-Energy Particles or Photons

Abstract

Extraterrestrial organic compounds have been considered as important sources for the origin of life on the Earth. In order to study the formation of organic compounds found in extraterrestrial bodies, simulated interstellar media were irradiated with high energy particles or photons. Particles used were protons from a van de Graaff accelerator, protons and helium ions from a cyclotron, electrons from a synchrotron, and heavy ions from “HIMAC heavy ion accelerator. Photons used were UV light and soft X-rays from a synchrotron. Gamma-rays irradiation was performed by using a 60Co source. Amino acid precursors were formed from a mixture of carbon monoxide (or methanol), ammonia (or nitrogen) and water by high-energy particles, gamma-rays, or X-rays. If nitrogen molecule was used as N-source, amino acid precursors could be formed by high energy particles, X-rays and gamma-rays, but not by UV light. In the case that ammonia was used, amino acid precursors were detected in all the cases, but energy yields (G-values) of amino acid precursors by high energy particles were much higher than those by UV or X-ray photons. Possible formation of amino acid precursors in interstellar environments was discussed from the point of view of chemical evolution toward origins of life.