Stability of Amino Acids and Related Compounds in Simulated Submarine Hydrothermal Systems

Abstract

Abstract Submarine hydrothermal systems (SHSs) have been thought of as a suitable environment for the origin of life subsequent to the abiotic synthesis of organic molecules. However, it has been pointed out that bioorganic molecules, such as amino acids, are easily degraded at a high temperature, and thus not likely to survive for the next step of chemical evolution in a SHS environment. On the other hand, it has been suggested that the main compounds generated abiotically at the first stage of chemical evolution are not “free” amino acid monomers but amino acid precursors with high molecular weights, i.e., complex combined amino acids. In this study, we tested the stability of complex combined amino acids, which were abiotically synthesized from a simulated primitive Earth atmosphere with proton irradiation, in a high-temperature and high-pressure environment compared with that of monomeric amino acids. Complex combined amino acids preserved more amino acids (including amino acid precursors that give amino acids after acid hydrolysis) than free amino acids after heating in simulated SHS environments. Our results suggest the possibility that complex organics prebiotically synthesized by cosmic rays could serve as primitive materials of chemical evolution at hydrothermal systems on primitive Earth.