Earth is very much powered by the sun. Beams of photons shoot down at us, dumping their energy into green plants. Then we eat the plants, or we eat the animals that eat the plants (or so on, up the food chain), and we too indirectly absorb that sweet solar energy.

For rogue planets that don't have a star to orbit, wandering alone through dark interstellar space, cosmic rays may provide a similar function to sunlight here on Earth. The idea, proposed in a new paper in the Journal of the Royal Society Interface, is that these beams of high-energy radiation could power underground ecosystems on worlds without much sunlight or atmosphere.

The hypothesis is a spin-off of a phenomenon that happens on Earth. Deep underground, the bacteria Desulforudis audaxviator survives by eating the byproducts of radioactive uranium, thorium, and potassium. Just as plants on the surface use the sun's energy to split water into a building block for carbohydrates (food), this bacteria takes advantage of the particles that zip off of radioactive rocks. Those particles split water into pieces that can combine with other molecules to form the bacteria's food.