We all know the universe is a vacuum. So why do astronauts think the universe has a smell? In fact, the universe has a smell, and our solar system has a very special smell. This could be the result of a number of factors, but it’s all clear: Our Universe is pretty stinky. If you’re curious to find out what the universe smells like and why it smells the way it does, the explanation might surprise you.

The smell of the universe

Of course, none of the astronauts took off their helmets in space, they reported a strange smell in the capsule after returning from space.

Astronaut Don Pettit said: “The best description I can think of is metallic, a rather pleasant metallic smell. It reminds me of college summers, where I worked for many years. hours with an electric arc welder to fix heavy equipment for a small logging outfit. It reminds me of welding fumes. It’s the smell of space.”

Other astronauts have described it in similar but different ways: burning metal, the characteristic odor of ozone, acrid smell, walnuts, gunpowder, and even burnt almond cookies. Astronaut reports differ slightly, but have one thing in common: a burning smell.

So where does the burning smell of the universe come from? There are two explanations.


This is related to the process that occurs in the plane lock when the astronauts return from space. During re-pressurization (adjusting to proper pressure), oxidation has occurred, the space oxygen atoms cling to the astronaut’s suit and fly in during the depressurization period when the gas is locked. open and combine to form atmospheric oxygen (O2).

This process  produces an odor similar to burning, which may explain the astronauts’ reports of a smoky, burning smell.

Explosions from the stars

The second hypothesis could explain the space smell that astronauts report in relation to stellar explosions – i.e. dying stars.

Although we have only studied the night sky for a few centuries, the universe is about 13.7 billion years old, and our solar system is estimated to be about 4.5 billion years old. This means that in the billions of years before our solar system formed, stars were born and died across the universe.

Mùi của vũ trụ có thể từ các ngôi sao chết. Ảnh: Discovery Magazine.

When stars die, that tends to be a dramatic event, and this chaotic process produces compounds known as polycyclic aromatic hydrocarbons (PAHs). PAHs are present throughout the solar system including here on Earth. They can be found in a number of foods, coal, petroleum, and other materials. Perhaps part of the reason space smells of burning and coal is because it emits strong-smelling PAHs.

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