  Ionizing radiation is known to have a destructive impact on biology by
causing damage to the DNA, cells, and production of Reactive Oxygen Species
(ROS) among other things. While direct exposure to high radiation dose is
indeed not favorable for biological activity, ionizing radiation can, and in
some cases is known to produce a number of biologically useful products. One
such mechanism is the production of biologically useful products via charged
particle-induced radiolysis. Energetic charged particles interact with surfaces
of planetary objects such as Mars, Europa and Enceladus without much shielding
from their rarefied atmospheres. Depending on the energy of said particles,
they can penetrate several meters deep below the surface and initiate a number
of chemical reactions along the way. Some of the byproducts are impossible to
produce with lower-energy radiation (such as sunlight), opening up new avenues
for life to utilize them. For each of these cases, we calculate the energy
deposition rate as a function of depth, and estimate the energy availability
for potential metabolic activity. We discuss various mechanisms through which
life could support itself utilizing the byproducts of these ionizing
radiation-induced reactions, such as chemoautotrophs using solvated electrons,
extracellular electron transfer, and indirect electrophy to facilitate
processes like carbon fixation, nitrogen fixation and sulfate reduction, and
possibly for ATP production.
