Catherine Latham
BBC journalist
Scientists are analyzing smells in space – from Earth's closest neighbors to planets hundreds of light-years away – to learn more about the composition of the Universe.
Jupiter, says Marina Barsenilla, is a bit like a "smelly bomb."
The largest planet in the solar system, Jupiter, has several layers of clouds, she explains, and each layer has a different chemical composition.
The fizzy gin might lure you in with the sweet aroma of its "poisonous marzipan clouds," she says.
And then the smell "gets worse as you go deeper".
"You'd probably want to die before you get to the point where the pressure would crush you," she says.
"The upper layer of the clouds, we believe, is made up of frozen ammonia," says Barcenilla, comparing the stench to the smell of cat urine.
"Then, as you go down further, you come across ammonium sulfide. Then you have ammonia and sulfur together – which is a combination from hell."
Sulfur compounds are mainly responsible for the smell of rotten eggs.
If you could probe even deeper, she continues, you would encounter Jupiter's characteristic streaks and swirls.
"Jupiter has thick bands that are colored. We think some of those colors could be from clouds of ammonia and phosphorus fumes."
There are also potentially some organic molecules called tholins, complex organic molecules related to gasoline.
So Jupiter, she says, can also contain a hint of gasoline "oiliness" with a dash of garlicky scent.
Barsenilla is a space scientist, fragrance designer, and PhD student in astrobiology at the University of Westminster, London.
In her early years studying the cosmos, she found herself constantly asking herself, "What would that smell like?"
Then she realized, "I have that molecule in my lab. I could try to make it."
And so, in addition to her academic work – searching for signs of life on Mars – Barsenilla has been busy creating aromas that recreate the scents of deep space for London's Natural History Museum and its latest exhibition, Space: Can life exist outside Earth?
From the stench of rotten eggs to the sweet scent of almonds, space is a surprisingly fragrant place, she says.
Comets, planets, moons, and gas clouds would all have their own unique scent if we could smell them with our noses.
But what can these aromas reveal about the mysteries of the Universe?
- Scientists are racing to discover why the universe exists
- What are solar flares and can they cause power outages on Earth?
- Scientists find 'strongest evidence yet' of life on distant planet
Before we delve into the fragrant delights of the cosmos, it might be worth pausing for a moment and reminding ourselves what scents are in general.
Smell, although often underestimated, is probably the most ancient of all the senses.
Take for example a tiny single-celled organism, a bacterium, as it floated through the Archeozoic seas about 3,5 billion years ago.
When it senses the presence of a chemical, perhaps a tasty nutrient or a danger to avoid, the bacteria's flagellum - a tail-like appendage - would start working like a propeller, allowing the creature to redirect its movement.
For our earliest ancestors, "this most rudimentary sense of smell" meant the difference between life and death.
And our own sense of smell is just a more sophisticated version of this ability to detect chemical substances in our environment.
Our noses contain dense clusters of nerves made up of millions of specialized neurons that are decorated with molecules known as chemoreceptors.
When they attach to a chemical substance, they send a signal to our brain which is then interpreted as a recognizable smell.
This sense of smell means that we have the ability to detect chemical substances around us.
For humans, smell not only helps them recognize food or warn of environmental dangers, it also activates memories and plays a key role in social communication.
After millions of years of evolution, the ability to smell is intrinsically linked to our emotional well-being.
During the long, isolated months in orbit, it can also be an important connection to home for astronauts.
But the space station can also be an unusual place when it comes to smells.
"Alexey Leonov [the first person to complete a spacewalk] was in charge of all the foreign astronauts," says Helen Sharman, the first British astronaut.
It was 1991 and Sharman was preparing to spend eight days on Mir, the Soviet space station.
Just before lunch, Leonov "handed me a sprig of wormwood to take upstairs."
During her stay on Mir, Sharman would occasionally crush wormwood leaves to release their characteristic sage-like scent – because, she says, “it’s nice to be able to smell something.”
On the Mir space station, Sharman explains, there was very little smell.
In microgravity, warm air doesn't rise, so "the smells of hot food don't leave your plate."
The only way to smell it would be to "stick your nose in the food," she says.
But there was one distinctive smell on the space station that many astronauts reported smelling after a spacewalk.
"It reminded me of the smell when I was a kid and walked past a car repair shop," Sharman says.
"I could smell something being cooked there – I could smell that metallic smell in the air."
During the mission, Sharman experimented with potential materials for use during spacecraft assembly.
"I had a bunch of thin layers, mostly ceramic, that I had to frame and then expose to the environment around the space station."
When she brought the samples back from the airlock, she would smell a rush of scent, the metallic aroma of space.
"It was my favorite experiment – because it had a smell."
Other astronauts described a sensation similar to burnt flesh, gunpowder, or burning electrical wires.
But what causes this smell still remains a mystery.
One possible explanation, says Sharman, is that it is caused by oxidation.
"The atmosphere, the environment, immediately around the space station, is pretty much like a vacuum, but not completely at that altitude," she says.
"What we have in the remnants of the atmosphere is atomic oxygen."
Atomic oxygen – or individual oxygen atoms – can stick to an astronaut's spacesuit or tools.
When they re-enter the space station, the individual oxygen atoms combine with the oxygen present in the cabin to create ozone (O3).
"As soon as the reaction occurs, you get the smell of ozone," Sharman says.
And we humans down here on Earth can also smell hints of ozone.
Have you ever noticed the metallic smell of static electricity right after a storm?
That's ozone.
Another possibility is that Sharman inhaled atoms from a dying star.
When a star dies, it releases a huge amount of energy.
During this process, the star produces polycyclic aromatic hydrocarbons (PAHs) – “wire-web-shaped molecules,” says Sharman – which float around the Universe and contribute to the creation of new comets, planets and stars.
On Earth, PAHs are present in fossil fuels, such as coal, crude oil, and gasoline, and are often formed during the incomplete combustion of organic materials.
"If your food burns," says Barcenilla, "that's the kind of molecule you're creating. When stars die, the combustion creates the same kind of molecules. They then float around in space forever."
Many of these compounds have a smell similar to paint thinner or mothballs, while others are more reminiscent of burning plastic or bitumen.
Data from space comes in all forms.
The first scientific information from space arrived in 1958 from NASA's Explorer 1, as sound.
Fast forward to 2022, and NASA's James Webb Space Telescope (JVST) has captured the first-ever whiff of carbon dioxide (CO2) in the atmosphere of an exoplanet – a planet outside our solar system – the gas giant VASP-39 b.
JVST didn't actually smell carbon dioxide in the sense of inhaling it, but rather detected its presence by monitoring how the planet's atmosphere changes starlight when it passes in front of its sun.
By analyzing subtle changes in light, JVST can identify various chemical substances on alien worlds.
And the universe is "huge," says Barsenilla.
It is full of worlds with scents that are numerous and diverse.
Chemical analysis of the atmosphere on Titan, Saturn's largest moon, suggests it smells like sweet almonds, gasoline, and rotten fish.
Meanwhile, the "smell" of rotten eggs might deter you from visiting the planet HD 189733 b, a boiling gas giant about 64 light-years from Earth.
- Did our Sun ever have a twin?
- Earth's inner core may have changed shape, scientists claim
- New space research: Is there life on the moons of Uranus
JVST didn't actually smell carbon dioxide in the sense of inhaling it, but rather detected its presence by monitoring how the planet's atmosphere changes starlight when it passes in front of its sun.
By analyzing subtle changes in light, JVST can identify various chemical substances on alien worlds.
And the universe is "huge," says Barsenilla.
It is full of worlds with scents that are numerous and diverse.
Chemical analysis of the atmosphere on Titan, Saturn's largest moon, suggests it smells like sweet almonds, gasoline, and rotten fish.
Meanwhile, the "smell" of rotten eggs might deter you from visiting the planet HD 189733 b, a boiling gas giant about 64 light-years from Earth.
And sniffing out cosmic chemicals could not only give us vital details about the composition of the Universe, but also give us details about where to look for life, says Barcenilla.
"If you could take a boat ride on planet K2-18b – if it had an ocean and you could take off your spacesuit – then it might smell like rotten cabbage," says Subhajit Sarkar, an astrophysicist at Cardiff University.
In 2023, Sarkar was part of a team that, with the help of the JVST, smelled what could be the scent of life on K2-18b, an exoplanet approximately 120 light-years from Earth.
The telescope detected "the tiniest hint," Sarkar says, of dimethyl sulfide (DMS), which is sometimes considered one of the main components that produce the "smell of the sea."
"K2-18b is interesting for a number of reasons," says Sarkar.
"It is part of a larger group of exoplanets called sub-Neptunes."
Larger than Earth but smaller than Neptune, sub-Neptunes are the most common type of planet in the galaxy and, despite their abundance, much about them remains a mystery.
"There are some big questions about sub-Neptunes," says Sarkar.
"Why don't they exist in our solar system? And what are they made of?"
One way to try to understand them better, according to Sarkar, is to study their atmosphere.
"K2-18b was known to be a good target for that."
K2-18b is, in theory, a "hycean" world, a habitable exoplanet covered in an ocean.
In 2025, Sarkar and his colleagues reanalyzed K2-18b's atmosphere—and found even stronger traces of atmospheric chemicals that, as far as we know, are produced only by life—specifically phytoplankton and other marine organisms.
According to the researchers, the atmosphere of K2-18b may contain DMS and/or dimethyl disulfide (DMDS).
"At this point, we don't know of any non-biological processes that can produce these chemicals in large quantities. Certainly on Earth, it's very, very clear that DMS and DMDS are produced by biology. They're very specific bio-fingerprints from that perspective," says Sarkar.
And with concentrations 10.000 times higher than those found in Earth's atmosphere, the findings suggest that K2-18b could have an ocean "twitching with life," Sarkar says.
But, he warns, it is possible that the chemicals come from abiotic sources and more research is needed.
However, he adds, if K2-18b is indeed a habitable ocean world, "then it fits into that picture, because then we have marine life potentially producing this molecule that, on Earth, binds to marine life."
So, perhaps it's not necessary to travel to space to experience what it actually smells like.
Many of the smells of space are familiar to us and can be found right here on Earth – and several people have attempted to recreate the smell of space, including Barsenil.
When I stick my own nose into her Mars scent cocoon at the Natural History Museum – I smell rust, dust, and a hint of damp.
The smell brings back memories: the back corner of the garage, with piles of cardboard boxes filled with once-beloved books and pieces of wood from generations-old furniture.
The homely smell of childhood.
But perhaps the greatest fragrant treasure of all is not to be found in distant space, but here on Earth.
There is nothing like the smell of our own planet, claims Sharman.
She describes returning home in 1991, still very much alive in her mind.
"It was late May, so even in Central Asia, the ground wasn't completely dry by the time we returned to Earth."
As it landed, the spacecraft bounced "quite a bit," crushing plants on the ground below.
"We landed on a vegetation of wormwood bushes in Kazakhstan," Sharman recalls.
"The rush of fresh air when we opened the lid was fantastic. It smelled wonderful, absolutely wonderful."
BBC is in Serbian from now on and on YouTube, follow us HERE.
Follow us on Facebook, Twitter, Instagram, YouTube i Viber. If you have a topic suggestion for us, please contact bbcnasrpskom@bbc.co.uk
- Eleven spacewalks that made history
- A cave discovered that could host people on the moon
- Mysterious pairs of planets that we still cannot explain
- The "Christmas Light" galaxy reveals how the Universe was created
Bonus video:
