Methylenimine and cyanomethanimine synthesis from ion irradiation of N2-CH4 ice: Implication on the formation of prebiotic molecules in outer solar system bodies

Abstract

The synthesis of methylenimine and cyanomethanimine from ion irradiation of N2-CH4 ice was studied, in an attempt to simulate the role of medium mass cosmic rays and energetic solar particles in the processing of nitrogen-rich ices on cold astrophysical environments, such as those in the outer region of the solar system (e.g. Pluto, Charon, Triton, Makemake and Titan). The N2-CH4 (90:10) ice mixture was irradiated at 9 K by 38.4 MeV 40Ca9+ (0.96 MeV/u) at the GANIL facility (Caen/Fance). The evolution of the samples was monitored using in-situ Fourier transform infrared spectroscopy (FTIR). The results indicate the formation of CH2NH and CH2NCN, which are considered species of interest in prebiotic chemistry. Other species produced by radiolysis were HCN, HNC, hydrocarbons and nitriles. Direct comparison of the laboratory spectrum from the mixture of reaction products provides an efficient way to focus on the identification of chemical synthesis routes for the production of molecules important in the development of life that are consistent with the chemical inventory and physical conditions on frozen moons and cold objects in the outer solar system.