COSMIC RAY ENERGY SOURCE. “The discovery of Ca. D. audaxviator thriving 2.8 km below the Earth’s surface powered by radiolysis opens up new possibilities of biological interaction with (ionizing) particle radiation. Galactic cosmic rays produce secondary particles that deposit energy in the subsurface environment. Conceivable mechanisms have been proposed through which the energy of Galactic cosmic rays-induced particles can be used to produce biologically useful products such as organics and utilize energy for radiolysis to power a potential subsurface ecosystem.”
https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459