Radiation effects on amino acids and implications for life detection on Mars

In this work, we systematically investigate the radiation stability of amino acids in different physical states under 60Co γ-rays irradiation. The results demonstrate that the radiation stability of amino acids is strongly dependent on their physical state. After exposure equivalent to ~31.2 Ma of Martian surface irradiation, the single crystal glycine remains largely intact, whereas solid powder glycine transforms from the monoclinic α-phase to the hexagonal γ-phase.

In contrast, glycine in aqueous solution shows significant modification, involving both decomposition and complex recombination or polymerization. These findings provide new insights into the radiation-driven evolution of organic molecules on Mars and offer critical constraints for interpreting ambiguous spectroscopic signatures obtained from Martian surface analyses.