Space Smells Like Cat Urine? Someone Has Actually Sniffed It! Wait, Isn’t Space a Vacuum...?

What does space smell like? Some places resemble cat urine, others gunpowder.

Except near celestial bodies, most of space is a vacuum, so there’s no inherent odor. However, gases exist around some planets, and analyzing their composition might reveal their potential smells.

Some scientists are doing exactly that. Marina Barcenilla, an astrobiologist and perfume designer, is dedicated to recreating possible space odors.

For instance, Jupiter is a bit like a stink bomb. As the largest planet in the solar system and a gas giant, Jupiter’s troposphere has a complex cloud structure. The top layer consists of ammonia ice, which Barcenilla compares to cat urine. Deeper layers encounter clouds of ammonium sulfide or ammonium sulfide, known for their rotten egg smell. Saturn’s deeper atmosphere smells like gasoline with a hint of garlic.

Jupiter’s lower atmospheric pressure is 10 times Earth’s, so landing (though there’s no solid surface) would involve immense pressure—but you’d likely want to escape the stench before being crushed. Barcenilla notes: “You might wish for death before the pressure crushes you.”
Of course, these odors are scientists’ inferences based on chemical compositions. We can’t yet verify the actual smells on other planets’ surfaces. However, astronauts who’ve conducted spacewalks have described unexpected scents.

Astronauts often use terms like “fireworks,” “barbecue,” “hot metal,” “burnt meat,” or “metal welding” to describe the smell when they remove their helmets after returning to the station. Former NASA astronaut Tom Jones compared it to ozone. Where does this scent come from?

Though space is nearly a vacuum, it’s not entirely particle-free. One explanation links it to oxygen floating around the station. Ultraviolet rays in space split oxygen molecules (O₂) into single oxygen atoms, which may attach to spacesuits, station airlock walls, or other exposed items, triggering reactions that form ozone—explaining the smell.

Another theory ties it to stellar explosions. When some stars near the end of their lives explode, they produce polycyclic aromatic hydrocarbons—molecules found in grilled food, coal, and oil. However, NASA spacewalk flight controller Miranda Nelson states these explanations lack official research data.
In 2023, Subhajit Sarkar, an astrophysicist at Cardiff University, analyzed gas composition data from an exoplanet using the James Webb Space Telescope, identifying dimethyl sulfide—known as the source of “ocean smell.” In 2025, Sarkar and colleagues re-explored the planet’s atmosphere, detecting chemicals produced only by phytoplankton and marine organisms on Earth. Yet it remains unconfirmed whether non-biological processes could generate these substances on that distant planet.

Thanks to scientists’ imagination and efforts, perhaps one day we can experience space odors without leaving Earth—even if they’re not pleasant.