Resistance of Enzymes to Ionizing Radiation under Model Conditions of the Martian Regolith

Ionizing radiation is one of the main factors that destroy biomolecules in extraterrestrial conditions. The effects of radiation depend on the conditions of the exposure (pressure, temperature, presence of various chemicals). We have studied the stability of enzymes (catalase and dehydrogenases) in the soil under irradiation with accelerated electrons in doses up to 100 kGy at low pressure (0.01 Torr) and low temperature (–130°C). After exposure to a dose of 100 kGy, the catalase activity remained at the control level, while the dehydrogenase activity decreased by a factor of five. The results of the study suggest the possibility of long-term preservation of active enzymes in the Martian regolith until they are inactivated due to the accumulation of radiation damage. Taking into account the intensity of ionizing radiation in the surface layer of the Martian regolith, we believe that a decrease in dehydrogenase activity by a factor of 10, 100, and 1000 from the initial level could occur within 1.9, 3.8, and 5.7 Myr, respectively, while catalase could remain active for even longer periods. The data support the possibility of detecting enzymatic activity by landers in the course of planned space missions.