In an interview in WIRED Magazine, Noreen Noonan, in charge of NASA's Planetary Advisory Committee, mentions that certain extremophiles, by which she means fringe bacteria, microorganisms and viruses, thrive on highly radioactive environments. One would have thought that radiation in high doses would kill off anything, but just like some extremophiles can survive the high temperatures around deep sea thermal vents, others derive energy from radiation.
This is all relevant to Noonan, who is both aware of organisms that might be brought back to earth and survive in hostile environments but also of Earthly organisms that won't be killed by being exposed to the extremes of space travel — and thus would contaminate other worlds.
It seems all life was previously thought to fall into two categories. Bacteria, and everything else. Now there is a third category into which these weird organisms fall.
Archea are cells that don't have a nucleus. Their DNA is somewhat free-floating. The extremophiles fall into this category. (Eukaryotes includes us, plants, algae and bunny rabbits — it's a big category.)
So, organisms that thrive on radiation — wow. We're talking Godzilla here. Or more likely some weird slime that emerges from a nuclear reactor and/or suddenly multiplies like crazy in the wake of atomic tests explosions. This is 50s sci fi stuff, but now it seems awfully close to being realistic.
A good thing might be if this stuff could "eat" nuclear waste. Probably not — more likely it just absorbs the heat and energy and can tolerate the radiation.
