Hydrogen and organic molecules generation from water radiolysis: from grave to cradle

Water radiolysis is a key process for hydrogen (H2) and abiotic organic molecules generation in the Earth’s crust. The aim of this presentation is to provide some insight into this process from a radiochemist viewpoint. We will transpose the knowledge we gain from water radiolysis in the context of radioactive waste disposal to natural geological settings and draw important conclusions for deep microbial ecosystems development and abiotic organic synthesis. Some examples will be given about: (i) the relationship between H2 production ant the nature of the emitted particle (α/β/γ) considered for water radiolysis, (ii) the boosted production of H2 observed when aqueous solutions are in contact with some mineral surfaces such as rutile (TiO2) and calcite (CaCO3), (iii) the scavenging role of carbonate anions onto hydroxyl radical and the amplified yield of H2, (iv) the switch from an inorganic world to an organic one through the carboxylate anions production from carbonate radiolysis. Radiation chemistry is often overlooked by geologists who consider the process as anecdotic (apart for the thermal budget of Earth) in term of mass balance. However, water radiolysis is a large-scale ubiquist process in the crust and it does not need specific conditions to occur. We will show that at geological time scale, water radiolysis leads to a very diverse, reactive, and fun chemistry able to sustain life and even to create the condition for its emergence.