With a top note of unwashed astronauts and base note of rancid eggs, space can be a smelly place.

In space no one can hear you scream, partially because they’d be distracted by the stench.

There are a lot of molecules in space, expelling a variety of smells—from the char of barbequed meats to the unappetising pong of rotten eggs.

But do astronauts even have a sense of smell in space to detect these odours? Space is mostly a vacuum, meaning there is no air to breathe or smell. However, when astronauts go to the International Space Station, it is pressurised with air so they can breathe, which means they can also smell.

Burnt steak and body odour is not what you imagine when you think of going into space, but that’s the consistent description astronauts have of the space station. Welding fumes or burning metal are also common scents. The source of these unpleasant fragrances is not fully understood. 

It is likely the re-pressurisation of spacecraft, with the oxygen being pumped in and pressurised is creating ozone. There are also a lot of mechanical operating parts which contribute to the smell. While it is not the smell of space, these introduced factors combine to create a mighty whiff up there.

There is also likely an aroma of body odour. Since there is little gravity, you cannot have a shower in space. Astronauts do wash themselves with wet wipe-like material. However, clothes washing can’t be done. The most common solution is to wear clothes for as long as one can stand the smell, then put them in bags that are sometimes disposed of in re-entering space capsules. As the capsule re-enters, it often burns the contents up in the atmosphere.

Astronauts have also been to the Moon. While it has no atmosphere, when they hopped back into their landers, which were pressurised with oxygen, the moon dust gave off a distinct gunpowder smell. Sadly, it did not smell like cheese.

The Sapas Mons volcano on the surface of Venus. Photo: NASA/JPL

With the new goal of sending astronauts to Mars, what would they smell on the red planet? The atmosphere on Mars is mostly carbon dioxide. However, the dirt is primarily iron oxide, which gives its ochre tint, much like central Australia. The atmosphere also has sulfur and acids. This means Mars would most likely have a desert-like acid smell, with some interesting overtones. It would definitely be an experience. Though not nearly as malodourous as Venus.

Imagine putting rotten eggs in an oven—that’s Venus for you. Venus has lots of carbon dioxide as well as sulfur dioxide, which is the smell of rotten eggs. It is also the hottest planet at 462 degrees Celsius every single day.

There are places in space where we have detected molecules that are found in compounds on Earth with smells we are familiar with. There’s lots of Hydrogen and Helium in space, which are odorless.

There’s also heaps of dust—small bits that end up being the building blocks of stars and planets, which contain lots of Carbon. This Carbon comes mostly in two compounds—one that resembles naphthalene, the main ingredient in moth balls, and another that is similar to propane or butane. Australian astronomers have even found molecules that match alcohol.

While space and interplanetary travel are romanticised in many ways, for now, ‘eau de Earth’ is a far more pleasant perfume.

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