In space, perhaps no one can hear you scream--but they can still smell some awfully funny things. The neighborhoods of comets and our moon, it turns out, are surprisingly odorous. Matt Davenport, associate editor at one of our partner publications, Chemical & Engineering News, explains why in this short video.
The comet-probing Rosetta mission did not actually smell anything when it got close to its target, but its instruments did detect telltale signatures of certain molecules in the gas cloud around the comet. It found ammonia, and the even more pungent hydrogen sulfide. That compound is what makes rotten eggs smell like, well, rotten eggs.
Moon dust, too, can smell up space. Astronauts who set foot on the moon reported a smell like gunpowder when they returned to the lunar lander. That is because the dust contains particles with lots of dangling, open bonds. Those bonds stay open in the moon's sparse atmosphere. But when Apollo astronauts tracked them back into their oxygen-rich temporary home, oxygen molecules latched onto these bonds, creating a reaction that smelled as if someone had just fired a gun.
If you have a sensitive nose and plan on booking a trip up, up and away, not to worry. These compounds are only in limited areas, such as those close to Earth. There is plenty of deep, open space where you can breathe free. If you can breathe in space, that is.