Ask the Astronaut: What does space smell like?

inside airlock.jpg
Inside the space station’s Quest airlock.

Q: What does space smell like?

Of course, outside in the vacuum of space, there are no molecules or atoms to smell, and my nose was inside a space helmet where I could not sniff the aroma of space anyway, But whenever I got out of my spacesuit in the airlock after an EVA (spacewalk), I smelled a trace of this peculiar, almost acrid odor. Astronauts call it “the smell of space.” I could still detect it as I was stowing my gear or tools in the airlock. To me, the odor was like ozone, hot electrical insulation, or  gunpowder. I think the odor is probably ozone-related. Outside, atomic oxygen (single atoms) stick to the fabric’s exterior surface, and perhaps to airlock walls and tools. This atomic oxygen is created from atmospheric O2 when struck by solar ultraviolet radiation. When you repressurize, the single atoms of oxygen combine with O2 in the cabin atmosphere to make ozone, O3. That’s what I think I was smelling.

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