Roles of Cosmic Rays and Ultraviolet Light in Chemical Evolution in Interstellar Environments

Abstract

It is suggested that organic compounds found in meteorites and comets had important roles in origins of life. In the Greenberg model, these organic compounds were originally formed in ice mantles of interstellar dusts in molecular clouds. There have been many works to evaluate this model. A frozen mixture of methanol, ammonia and water was irradiated with heavy ions to simulate the action of cosmic rays in molecular clouds. Amino acid precursors with large molecular weighs and complex structures were formed. Such organic compounds were altered with UV light in diffuse cloud, and with cosmic rays in small bodies in the solar system. Experiments to simulate such alteration processes of organic compounds are in progress to draw chemical evolution scenario to the generation of life on the Earth.