On the possibility of Galactic Cosmic Ray-induced radiolysis-powered life in subsurface environments in the Universe

摘要

Photosynthesis is a mechanism developed by terrestrial life to utilize theenergy from photons of solar origin for biological use. Subsurface regions areisolated from the photosphere, and consequently are incapable of utilizing thisenergy. This opens up the opportunity for life to evolve alternate mechanismsfor harvesting available energy. Bacterium Candidatus Desulforudis audaxviator,found 2.8 km deep in a South African mine, harvests energy from radiolysis,induced by particles emitted from radioactive U, Th and K present insurrounding rock. Another radiation source in the subsurface environments issecondary particles generated by Galactic Cosmic Rays (GCRs). Using Monte Carlosimulations, it is shown that it is a steady source of energy comparable tothat produced by radioactive substances, and the possibility of a slowmetabolizing life flourishing on it cannot be ruled out. Two mechanisms areproposed through which GCR-induced secondary particles can be utilized forbiological use in subsurface environments: (1) GCRs injecting energy in theenvironment through particle-induced radiolysis, and (2) organic synthesis fromGCR secondaries interacting with the medium. Laboratory experiments to testthese hypotheses are also proposed. Implications of these mechanisms on findinglife in the Solar System and elsewhere in the Universe are discussed.