In a fascinating revelation, astronauts have confirmed that space, despite being known for its emptiness, carries a distinct smell. While most space is devoid of tangible matter, those who have ventured into its depths have reported encountering an unexpected olfactory experience.
Astronaut Bruce McCandless II, mission specialist, participates in a extra-vehicular activity (EVA), a few meters away from the cabin of Space Shuttle Challenger. Photo: NASA
Some astronauts have described space as having a metallic, sweet, and slightly burnt aroma.
Astronaut Thomas Jones said it “carries a distinct odor of ozone, a faint acrid smell…a little like gunpowder, sulfurous.” Tony Antonelli, another spacewalker, said space “definitely has a smell that’s different than anything else.” Three-time veteran astronaut Don Pettit was a bit more verbose on the topic: “Each time, when I repressed the airlock, opened the hatch, and welcomed two tired workers inside, a peculiar odor tickled my olfactory senses,” Pettit recalled. “At first, I couldn’t quite place it. It must have come from the air ducts that re-pressed the compartment. Then I noticed that this smell was on their suit, helmet, gloves, and tools. It was more pronounced on fabrics than on metal or plastic surfaces.” He concluded it is hard to describe this smell; it is definitely not the olfactory equivalent to describing the palette sensations of some new food as “tastes like chicken.” The best description I can come up with is metallic, a rather pleasant, sweet metallic sensation. It reminded me of my college summers when I labored for many hours with an arc welding torch, repairing heavy equipment for a small logging outfit. It reminded me of pleasant sweet-smelling welding fumes. That is the smell of space.”
Obviously, astronauts can’t remove their helmets in space to take a big ole sniff. Rather, their observations have come from instances such as the smell of airlocks before and after venturing from their spacecraft into the void, as well as the smell of their spacesuits after a leisurely spacewalk.
This peculiar phenomenon has prompted scientists to delve into the possible explanations for the smell of space. Two prevailing theories have emerged, each shedding light on the origins of this cosmic fragrance.
The first theory, known as the Oxidation Explanation, revolves around the re-pressurization process that occurs when astronauts return from spacewalks to the International Space Station or their spacecraft. During this transition, oxidation takes place, causing oxygen atoms from space to attach to the astronauts’ suits. These oxygen atoms combine to form atmospheric oxygen, similar to a combustion process without the presence of flame and smoke. This chemical reaction is believed to produce the smoky, charred odor that astronauts have reported.
The second theory, known as the Stellar Explosion Explanation, delves into the remnants of dying stars. Over billions of years, stars have been born and perished throughout the vastness of the universe. When stars die, they release a compound called polycyclic aromatic hydrocarbons (PAHs). These PAHs are present within our solar system and can be found in various materials, including coal, oil, some foods, and even burnt substances like tobacco and wood. The burnt and charcoal aroma that permeates space could be attributed to these PAHs’ presence, resulting from the spectacular demise of stars.
Interestingly, while our solar system carries a distinct burnt scent, different regions of the universe likely possess their own unique smells. For instance, the dust cloud Sagittarius B2 is known for its high concentration of ethyl formate, the organic compound responsible for the distinct aroma of both raspberries and rum.
