The first known organisms that live totally independently of the sun have been discovered deep in a South African gold mine, raising hopes of finding similar creatures on other planets.

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.