Help pupils to see how probes might work by bringing back the bunsen! Dim the room and burn a few salts. (chlorides of sodium [orange], potassium[lilac] barium [green] etc) Pupils view them through hand-held spectroscopes, prisms or diffraction gratings. They see a "fingerprint" spectrum characteristic of the substance. Being a chemical detectives might help find the fingerprints of human organic life somewhere out there.