COSMIC RADIATION SOURCE. “In the light of these findings, it is reasonable to propose that instead of or in addition to in situ energy sources, the radiation (potentially supporting radiolysis-based life) can be of cosmic origin. Galactic cosmic rays (GCRs) are charged particles, mostly protons, originating beyond the Solar System. They have relatively lower flux but possess much higher energy than other radiation sources on Earth, and have noteworthy biological effects on terrestrial life and possibly on extrasolar planets.”
https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459