For all its serene blue beauty from afar, Uranus hides a detail that would make a visitor recoil: its cloud tops are laced with hydrogen sulfide, the very gas that gives rotten eggs their stench, so Uranus literally reeks
spacedaily.com
The solar system's most boring-looking planet conceals a nauseating secret beneath its serene exterior.

…In April 2018, a team led by Oxford planetary physicist Patrick Irwin reported the first clear detection of hydrogen sulfide gas sitting above Uranus’s main cloud deck…

Hydrogen sulfide is the same colorless, toxic gas that gives rotten eggs their smell, and people can detect it at very low concentrations, according to the Agency for Toxic Substances and Disease Registry…