Uranus smells like rotten eggs

TAKE A WHIFF  Uranus is a lovely robin’s egg blue in this image taken by the Voyager 2 spacecraft when it flew past in 1986. New measurements of the planet’s chemistry suggests it may smell like eggs, too — that is, really rotten eggs. 

Uranus’ upper clouds are made of hydrogen sulfide — the same molecule that gives rotten eggs their noxious odor.

Using a spectrograph on the Gemini North telescope in Hawaii, planetary scientist Leigh Fletcher and his colleagues detected the chemical fingerprint of hydrogen sulfide at the top of the planet’s clouds. This isn't a complete surprise: Observations from the 1990s showed hints of hydrogen sulfide lurking deeper in Uranus’ atmosphere. But the gas hadn’t been conclusively detected before.

The clouds aren’t just smelly — they can help nail down details of the early solar system. Uranus’ hydrogen sulfide clouds set it apart from the gas giant planets, Jupiter and Saturn, whose cloud tops are mostly ammonia.

Hydrogen sulfide freezes at colder temperatures than ammonia. So it’s more likely that frozen hydrogen sulfide ice crystals would have been abundant in the further reaches of the early solar system, where the crystals could have glommed onto newly forming planets. That suggests that ice giants Uranus and Neptune were born farther from the sun than Jupiter and Saturn.

Fletcher is far from repelled by the malodorous clouds. He and other planetary scientists want to send a spacecraft to the ice giants — the first since the Voyager spacecraft visited in the 1980s — to find out more.

Source - ScienceNews

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Citations - P. Irwin et al. Detection of hydrogen sulfide above the clouds in Uranus’s atmosphere. Nature Astronomy. Published online April 23, 2018. doi: 10.1038/s41550-018-0432-1.