What Does Space Smell Like?
What Does Space Smell Like?
We often think of space as empty, devoid of dust, planets, or even air. However, astronauts who have spent time in space report that it has a distinct smell. Space indeed has a smell, and our corner of the universe has its own unique odour, which might surprise you if you're curious about what it is and why it's there.
While no astronaut has been reckless enough to remove their helmet in the vacuum of space (which would be very detrimental to their health), many astronauts have reported a smell upon returning from spacewalks. They describe it in various ways, such as "metallic," "sweet metallic," "burning metal," "ozone," "walnuts and brake pads," "gunpowder," and even "burnt almond cookie." Despite the different descriptions, they all have one thing in common: a burnt smell.
So Why Does Space Smell Burnt?
Oxidation
One theory links the smell of space to the process that occurs when astronauts return from space to the International Space Station or their spacecraft in orbit around Earth. During re-pressurization, there's a chemical reaction called oxidation. Oxygen atoms in space attach to the astronaut's suit and enter the spacecraft when the airlock is open, combining to form atmospheric oxygen (O2). This process is similar to combustion, minus the flame and smoke, and it has a similar smell, which could explain the smoky, charred odor reported by astronauts.
Stellar Explosions
The second hypothesis relates the smell of space to stellar explosions, specifically the deaths of stars. While we've been studying the night sky for only a few centuries, the universe is approximately 13.7 billion years old, and our solar system is estimated to be around 4.5 billion years old. This means that for billions of years before our solar system even formed, stars were being born and dying across the universe.
When stars meet their end, it's typically a dramatic event that produces a compound called polycyclic aromatic hydrocarbons (PAHs). These PAHs are found throughout our solar system, including on Earth. They can also be present in foods, coal, oil, and various other materials. PAHs are created when substances like coal, tobacco, wood, and meat are burned. It's possible that the distinct burnt and charcoal-like smell of space is due to the presence of these smelly PAHs, somewhat like to the smell of a barbecue on a summer evening.
