Uranus smells like rotten eggs

If you could take a deep breath on Uranus, your lungs would fill with the stench of millions of flatulent cows. The planet’s upper atmosphere is saturated with hydrogen sulfide, the same molecule that gives rotten eggs their signature odor.

Spectroscopic data from the Gemini North telescope confirmed that the cloud tops are composed of this gas. Unlike Jupiter or Saturn, which have ammonia clouds, Uranus’s cold environment allows hydrogen sulfide to dominate the hazy layers.

This chemical composition suggests the gas giants formed at different temperatures and locations in the early solar system. The presence of so much sulfur means Uranus was far enough from the sun to lock those foul-smelling molecules into its structure.

You would never actually smell it, though. Before a single scent molecule hit your nose, the minus 200-degree Celsius temperature and the crushing pressure would ensure you weren't breathing at all.

Curiously, deep within the planet, the pressure is so intense that carbon atoms may crush together to form literal diamonds that rain through the mantle.