This is What the Universe Smells Like
What does it smell like on Mars? Or on Venus? And what do aliens smell like? There is a variety of "smells" in our universe. And most of them are pretty rancid.
Our solar system smells
Many planets around us are kind of big stink bombs. In lots of places in our solar system, you can, theoretically, encounter the smell of rotten eggs. On Mars and Venus, for example, and in several layers in Jupiter's atmosphere. On Venus, in addition, it is very hot. That could make for an interesting smell experience, thinks Brad Tucker, an astrophysicist, and cosmologist at the Australian National University. 'Like putting rotten eggs in the oven!' Of the moon's smell, we have witness accounts. According to astronauts who walked on the lunar surface, their spacesuits smelled like gunpowder afterward. In the International Space Station ISS, astronauts say it smells like hot metal or burnt steak.
Scientists determine smell from the comfort of their armchairs
How do we find out what smells are in our universe? We base that mainly on the knowledge we have of the chemical components found in a place. Only with the moon and the space station can we base it on odor reports from astronauts. Scientists can determine from the comfort of their armchairs on Earth what chemical components the atmosphere of another planet possesses. Those components are known to smell to us.
Many molecules in the universe are odorless
The most common molecules in the universe have no odor, such as hydrogen and carbon monoxide. Planets like Saturn and Neptune will have virtually no smell. Those consist mainly of the odorless gases hydrogen and helium. The substance that causes the rotten egg smell on Mars, Venus, and Jupiter is hydrogen sulfide. We encounter this in our solar system much more often. Probably because hydrogen and sulfide (in fact, sulfur) are common elements that react fairly easily with each other.
On Mars, you also find a lot of methane, the gas also released by farts. But contrary to what you might think, methane by itself does not have a distinct odor. That gunpowder-like smell that astronauts reported after walking on the moon can be explained by the presence of elements such as iron and nickel, which are common on the moon, according to Tucker. He would rather explain the smell from the ISS by the rotating machinery on board.