Scientists using the huge telescope on Hawaii's Mauna Kea volcano have discovered the world's most obvious space joke. "Uranus smells like farts" is an actual, and correct, headline making the rounds, as here and here. But as the BBC explains, it's no joke. It seems the seventh planet from the sun does indeed smell like rotten eggs. Scientists figured this out using the spectrometer on the Gemini North telescope—they found that the planet's clouds are made up mostly of the smelly gas hydrogen sulfide. The discovery, reported in Nature Astronomy, should help astronomers better understand the formation not only of Uranus but of the other outer planets. For one thing, Uranus differs from gas giants Jupiter and Saturn, whose clouds are made up mostly of ammonia ice (and are thus less smelly).
"If an unfortunate human were to ever descend through Uranus' clouds, they would be met with very unpleasant and odiferous conditions," says study co-author Patrick Irwin of the University of Oxford in a news release. Not that they'd live long enough to sniff it: "Suffocation and exposure in the (minus 328 degrees Fahrenheit) atmosphere made of mostly hydrogen, helium and methane would take its toll long before the smell." It's likely that Neptune's clouds are similar to Uranus' clouds in makeup, given that those two planets formed farther from the sun than Jupiter and Saturn, notes Space.com. For the record, astronomers generally prefer pronouncing the planet with the accent on the first syllable (YER-in-us), per Universe Today. (Scientists examining 30-year-old images from Uranus found a surprise.)