When the Rosetta probe’s little brother, Philae, landed on Comet 67P, a instrument called SESAME-CASSE recorded the sound vibrations of the landing. (Yes, yes, I know–this is space and there’s no sound. But you can still record vibrations which can be converted into sound.)
The recording lasts only two seconds but will reveal a vast amount of information about the composition of the comet.
Some conspiracy theorist believe this audio will reveal that Philae landed on the roof of an alien spacecraft or a giant Von Neumann machine.