While no astronaut has ever been reckless enough to unbuckle and remove their helmet in the vacuum of space (which is very bad for longevity), astronauts have reported an odor upon returning from space. Specifically, many astronauts report different airlock odors after participating in spacewalks.
“The best description I can think of is metallic; quite a nice sweet metallic sensation,” astronaut Don Pettit wrote, according to Space.com. “It reminded me of my college summers, where I worked long hours with an arc welding torch repairing heavy equipment for a small lumber company. It reminded me of nice sweet-smelling welding fumes. That’s the smell of space.” Little participated in various EVA (extravehicular activities or spacewalks) during his career at NASA, accumulating repeated experiences with the smell.
other astronauts have described it in similar but diverse ways: “burnt metal”, “a distinctive smell of ozone, a pungent odor”, “nuts and brake pads”, “gunpowder”, and even “burnt almond cookie”. Just like all wine lovers smell something a little different in the bottle, astronaut reports differ slightly in their “olfactory notes,” but they have one thing in common: a burnt smell.
What could explain why the space smells like burning? There are two possible explanations.