The clouds on Uranus smell like rotten eggs.

For a long time, scientists were not sure what made up the clouds on Uranus. Some thought they were made of ammonia, like the clouds on Jupiter. In 2018, researcher Patrick Irwin and his team used a telescope in Hawaii to study the light coming from the planet. They found the specific signature of hydrogen sulfide gas.Hydrogen sulfide is a gas that smells very strong even in tiny amounts. On Uranus, the temperature is about -224 degrees Celsius. This extreme cold causes the gas to freeze into tiny ice crystals that float in the air. These crystals form the thick cloud layers that surround the planet.This discovery helps scientists understand how the solar system began. It shows that Uranus and Neptune formed differently than Jupiter and Saturn. Because they are further from the sun, they captured more sulfur during their birth. While the smell is interesting, a human could never breathe it. The planet has no oxygen and the pressure would crush a person instantly.