Amino acid production by gamma-ray irradiation experiments simulating the process of aqueous alteration inside asteroids

Abstract

Amino acids, which are essential for the birth of life, are thought to have possibly been transported by meteorites originating from asteroids and other bodies. It is possible that the radioactive decay of short-lived radionuclides in asteroids in the early stages of the solar system formation caused aqueous alteration, resulting in the formation of high-molecular-weight organic matter and amino acids. It has been suggested that gamma-ray energy and the decay heat may contribute to the formation of amino acids. In this study, we investigated how composition of the starting materials affect the formation of amino acids by heating or gamma irradiation of aqueous solutions containing formaldehyde, ammonia, glycolaldehyde(GA) and/or hexamethylenetetetramine, which are thought to be present in the asteroid. Amino acid precursors were formed from the simple molecules by heating or gamma irradiation. The amount of amino acid precursors produced increased (ⅰ) when the gamma irradiation dose was increased, (ⅱ) when the ratio of formaldehyde in the starting material was increased, and (ⅲ) when GA was added to the starting material.