Carboxylate anion generation in aqueous solution from carbonate radiolysis, a potential route for abiotic organic acid synthesis on Earth and beyond

Low molecular weight carboxylate anions such as formate (HCOO?), acetate (CH3COO?) and oxalate (C2O42?) have been shown to play an important role in supporting deep subsurface microbial ecosystems. Their origin whether biological or abiotic is currently highly debated, but surprisingly radiolytic production has rarely considered, it the case for H2. Here, we address this question through dedicated irradiation experiments. Aqueous solutions containing carbonate, formate, irradiated using both 60.7 MeV ?-beam of ARRONAX cyclotron (Nantes, France) 661.7 keV ?-Ray order reveal mechanism chemical yield radiation-induced dissolved carbonate degradation. The yields (G-values) production/degradation low-concentration solution (0.01 1 mmol L?1) are measured. Carbonate degradation occurs three consecutive steps (Carbonate ?I Formate ?II Acetate ?III Oxalate) involving radical (CO2?•), dihydrogen (H2), carbon dioxide (CO2) generation. Dissolved radiolysis provides a consistent pathway enhancing two-fold H2 compared pure water generating carboxylic species, chiefly oxalate, readily available microbes. Radiation-induced may produce substantial amount (millimolar concentration) ancient groundwaters from crystalline bedrocks. Subsurface lithoautotrophic ecosystems not only be supported by also species radiolysis. can endogenous source on Mars other planetary bodies.