Panspermia is the theory that life on Earth may have arrived in a nascent form from outer space, carried through the void as bacteria in comets or asteroids. It’s controversial, certainly, but persistent too (as well as being a classic science fiction trope). A Scottish scientist has decided to test the theory for plausibility by sending a chunk of rock into orbit and back on an ESA spacecraft, to determine whether microbes can survive not just the cold and vacuum of space, but also the violent physics of atmospheric reentry.
Update! This just in: Centauri Dreams pours water, or rather radiation, on the plausibility of panspermia.