bacteria that feast on radiation's fruits

The search parameters for life on other planets just widened:

Uranium and other radioactive elements in the rock emit radiation that shatters water molecules, producing high-energy hydrogen gas that is able to cleave chemical bonds.

The bacteria exploit this hydrogen gas to turn sulphate (SO4) molecules from the rock into hydrogen sulphide (HS). It is the energy-trapping equivalent of photosynthesis. The energy of radiation, which makes hydrogen gas energetic enough to form these bonds, replaces the energy of the Sun.

The bacteria are probably descended from light-dependent strains, which means that certain initial conditions still apply. However, this means that planets that appear cold and dead, a billion light-years distant, may in fact teem with life.