What Space Smells Like According To Astronauts

One idea blames it on dying stars. When a star dies, it releases a host of malodorous compounds called polycyclic aromatic hydrocarbons (PAH). Louis Allamandola, founder and director of the Astrophysics and Astrochemistry Lab at NASA Ames Research Center, says these PAHs float around forever and are found throughout the universe, including in the food right here on Earth. 

A far simpler — albeit less cool — explanation is a chemical reaction called oxidization. Many of these smelly accounts occur immediately after an astronaut returns from their space jaunt, closes the outer hatch, re-pressurizes the airlock, and opens the inner hatch. The Australian Academy of Science says during an astronaut’s time in space, single atoms of atomic oxygen accumulate on everything from the actual fabric of the suit to the tools and equipment the astronauts had with them at the time. It might just be that while pressurizing the airlock, those single atoms of atomic oxygen combine with O₂ to make ozone, and that’s what astronauts are getting a whiff of.

NASA takes this whole smelly situation so seriously they hired chemist Steven Pearce to recreate the odor so astronauts training for future space missions won’t be startled by the olfactory surprise. He said that metallic scent may actually be coming from the ions as they vibrate.