Accumulation and Recombination of Radicals as an Energy Source for Active Processes in Icy Bodies of the Solar System

Observations indicate that active energy-release processes occur within many icy bodies in the Solar System at large heliocentric distances. The energy source supporting such an activity remains uncertain. We propose the spontaneous recombination of accumulated radicals as the energy source. In our model, these radicals accumulate in water ice at low temperatures due to radioactive decay of long-lived radionuclides. We modeled the propagation of this recombination process for icy bodies of varying composition and radius, considering different initial concentrations of radicals and initial temperatures ranging from 5 to 50 K. Our results identify conditions under which this process can raise the temperature up to 273 K and demonstrate that such a temperature can be maintained within a body with a radius of 250 km for over 100 million years. We also show that the process is weakly temperature-dependent and can occur at very large heliocentric distances, including comets in the Oort Cloud.