Uranus stinks, and there's scientific proof.
Researchers confirmed Monday the seventh planet from the sun has an upper atmosphere full of one of the smelliest chemicals known to humans, hydrogen sulfide, according to study published by Nature Astronomy.
The odorous gas is what gives rotten eggs – and human flatulence – their distinctive and unpleasant smell. According to the Environmental Protection Agency, people can smell the gas when it makes up as little as three out of every billion molecules in the air, so imagine what being surrounded by clouds of the stuff would smell like.
"If an unfortunate human were ever to descend through Uranus's clouds, they would be met with very unpleasant and odoriferous conditions," Patrick Irwin a physicist at the University of Oxford, who led the study, said in a statement.
Scientists discovered evidence of "the noxious gas swirling high in the giant planet's cloud tops" after observing how sunlight bounced off Uranus' atmosphere, according to a news release from the Gemini Observatory, a high-power telescope located on top of Hawaii's Mauna Kea volcano.
The new findings come after decades of observations and even a visit by the Voyager 2 spacecraft to the blue-green ice giant, the release said. Before making the discovery, scientists had long inferred hydrogen sulfide existed in the planet's atmosphere, but never "conclusively detected" the gas before, according to Science News.
Using a 26-foot Gemini North telescope, the team of scientists studied the reflected sunlight in infrared and determined what types of molecules made up the planet's atmosphere, the release said. While evidence of the molecular compounds was "barely there," Irwin said scientists were still "able to detect them unambiguously" given the sensitivity of their instruments and the "exquisite conditions" on Mauna Kea.
The Uranus' atmospheric composition was so difficult to nail down because when a cloud deck forms by condensation, it hides the gas responsible for forming the clouds beneath levels that can be usually seen with telescopes, Leigh Fletcher, a member of the research team, said in the release.
"Only a tiny amount remains above the clouds as a saturated vapour," said Fletcher, who is a planetary scientist at the University of Leicester in the United Kingdom. "The superior capabilities of Gemini finally gave us that lucky break."
Aside from lending credence to Uranus jokes, the hydrogen sulfide discovery sheds light (or maybe smell) on how planets and the solar system formed, the release said.
Being able to confirm the composition information is "invaluable in understanding Uranus' birthplace, evolution and refining models of planetary migrations," the release said.
Understanding what makes up distant planets, such as Uranus, could help scientists determine where in the solar system the planets first formed and how far they moved from the sun over time, Business Insider reported.
Glenn Orton, a co-author of the new study and a planetary scientist at NASA's Jet Propulsion Laboratory, told Business Insider the new research points to "evidence of a big shakeup early on in the solar system's formation."
"There was definitely a migration taking place," Orton said.
While the planet's smell may be more than enough to repel most from wanting to visit, Orton said researchers are working on a proposal for a new Uranus spacecraft, which they hope will help them learn more about where the outer planets actually formed and how the solar system came to be.
Hopefully, the proposed spacecraft will be unmanned like its predecessor, Voyager 2, because Orton said the probe will be expected to plunge through Uranus' pungent clouds.