Radiolysis of water: a look at its origin and occurrence in the nature

The ubiquitous presence of water and ionizing radiation in the nature point out to the occurrence of radiolysis of water on Earth and beyond. Laboratory experiments and computer simulations of radiation-induced processes are reviewed: action of radioactive 40-K rays in early ocean water 3800 Ma ago and of natural nuclear reactor radiations in underground waters of the primitive Earth 3200 Ma ago. Also some findings relevant to the action of cosmic and radioactive rays in water ice of a cometary nucleus are presented.