You Won't BELIEVE What Space Actually SMELLS Like!

While the vacuum of space itself means humans cannot directly sniff the cosmos, astronauts returning from spacewalks often bring a peculiar aroma back with them into the spacecraft. Inside the airlock, once helmets are removed, they describe a distinct scent clinging to their suits and equipment. This cosmic perfume is frequently characterized as metallic, sometimes evoking memories of seared steak, hot metal, or even the sweet fumes of welding. Astronaut Don Pettit, for instance, fondly recalled it as a "pleasant sweet metallic sensation" reminiscent of his college summers working with an arc welding torch.

This intriguing scent is largely attributed to the presence of polycyclic aromatic hydrocarbons (PAHs). These complex molecules are abundant throughout the universe, forming as byproducts of dying stars and incomplete combustion. PAHs float indefinitely in space, found in comets, meteors, and interstellar (Review) dust. On Earth, these same compounds are present in materials like coal and oil, and are also released when substances such as wood or meat are burned, which helps explain the "burnt" notes in astronauts' descriptions.

Another scientific theory suggests that the smell arises from atomic oxygen. In the low Earth orbit environment, highly reactive single atoms of oxygen can adhere to spacesuits. When astronauts re-enter the pressurized airlock, these atomic oxygen particles react with the cabin air, undergoing a process similar to oxidation or combustion without a flame. This chemical reaction is thought to produce the metallic or burnt odor, and can also lead to the formation of ozone, which itself has a sharp, acrid smell. The distinctiveness of this odor is such that NASA has even enlisted fragrance experts to recreate it for astronaut training simulations.