Effects of ionizing radiation on the survival of bacterial spores in artificial Martian regolith

Bacterial spores of Bacillus subtilis were used as a model system to study the effects of ionizing 33 radiation on the survivability of spores uncovered and covered with artificial Martian regolith. Spore 34 survival after X-ray exposure was mainly depending on the role of non-homologous end-joining 35 (NHEJ) as the major DNA double-strand break repair pathway during germination, the involvement of 36 major small, acid-soluble spore proteins (SASP) as DNA radioprotectants and the coverage by Martian 37 regolith, whereas spores covered with Martian regolith were significantly more sensitive to X-rays than 38 uncovered spores, which is mainly due to the interaction of X-rays with artificial Martian regolith 39 resulting in the formation of secondary electrons and reactive oxygen species