Astronauts reveal what space smells like

With space being such a vast, empty void, you might not expect it to have its own smell. But according to astronauts who have been there, space does in fact have a distinct scent.

While it’s not exactly a cosmic spectrum of aromas, the smell of space is pretty bizarre, according to the accounts of those returning from spacewalks.

When coming back into their spacecraft, they've described a variety of smells lingering in the airlock. Imagine the aroma of burnt metal and almond cookies floating around – a bit like a space bakery.

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NASA astronaut Don Pettit described it best when he told Space.com. "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’," he said.

"The best description I can come up with is metallic; a rather pleasant sweet metallic sensation."

He also compared it to the sweet smell of welding fumes.

“It reminded me of my college summers where I labored for many hours with an arc welding torch repairing heavy equipment for a small logging outfit,” he added.

Other astronauts have reportedly likened it to the smell of burning metal, walnuts and brake pads, gunpowder, and even, weirdly, burnt almond cookie. While the descriptions vary, they all circle back to one common theme - a burnt smell.

And the interior of the International Space Station? That’s a little more mundane, Pettit said.

"[The ISS] smells like half machine-shop-engine-room-laboratory, and then when you're cooking dinner and you rip open a pouch of stew or something, you can smell a little roast beef," he told Space.com.

Yum.

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So, what in the universe could cause space to smell like a cosmic bonfire? There are a couple of theories that might just explain it.

First up is oxidation. When astronauts come back to their spaceship and the airlock re-pressurizes, a chemical reaction occurs, according to How Stuff Works. Oxygen atoms in space hitch a ride on their suits and mix with the ship's atmosphere, creating a smell akin to combustion, without the flames and smoke. This could be why astronauts are greeted with a smoky, charred odor after their spacewalks.

Then, there's a theory which revolves around the countless explosions of stars over the billions of years the universe has existed.

Our universe has witnessed the birth and death of countless stars. When stars go out, they do so with a bang, creating compounds called polycyclic aromatic hydrocarbons (PAHs). These PAHs are not just something you find in space - they exist on Earth too, in things like coal, tobacco and even the food we eat. It’s thought that the distinct burnt aroma of space is due to these PAHs, which exist as remnants of celestial explosions.

So, the next time you gaze up at the night sky, remember that space isn't just an empty black canvas. It's a place with its own unique - if somewhat burnt - aroma, perhaps reminiscent of its ancient past.