The effect of ionizing radiation on hydrated fungal cells: Implications for planetary protection and mars habitability

Liquid water is one of the essential conditions for life as we know it. Its presence has been currently reported beyond Earth. Geological and mineralogical evidence indicates that water once flowed on Mars. The recent discovery of present ice-water on the planet's surface is one of the driving factors for life-detection missions. The highly radiative Martian surface, combined with aqueous thin layers, is prohibitive for the presence of hypothetical forms of terrestrial-like life on the planet. In this context, we examined the survival of hydrated colonies of the Antarctic black fungus Cryomyces antarcticus, which thrives in the extreme environment of McMurdo Dry Valleys in Antarctica, after the exposure to increasing doses of space relevant γ-rays. Results suggest that water significantly reduces the number of survivors at the lowest doses, while at the higher dose (117 kGy) the cumulative damage caused by radiation could no longer be counteracted by dehydration.