Possibility of Liquid Water Formation in Icy Bodies Due to the Process of Rapid Recombination of Accumulated Radicals

Active energy-release processes with uncertain energy sources have been observed on various icy bodies in the Solar System. In this paper, we consider a spontaneous recombination of radicals accumulated in water ice as a potential energy source, which could lead to liquid water formation beneath an icy body’s surface. We simulated the propagation of the recombination process through a small, 1-km-radius icy body with an initial temperature of 10 K consisting of amorphous ice, dust, and volatile gases trapped in the amorphous ice. Our results show that the recombination front rapidly propagates throughout the body, outrunning all other processes, including gas diffusion. If a sufficient concentration of radicals accumulates, the temperature and the pressure behind the recombination front could be sufficient to the formation of liquid water inside the icy body. The time during which these conditions can be maintained inside the body is determined by the diffusion of the gases released from the amorphous ice. For a 1-km body with a porosity of 0.65 and a dust-to-ice mass ratio of 1, this time is approximately 50 years. The recombination process weakly depends on the initial temperature of the icy body and can occur at very large heliocentric distances, including comets in the Oort cloud.