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What do Uranus's cloud tops have in common with rotten eggs?

Hydrogen sulfide, the gas that gives rotten eggs their distinctive odor, permeates the upper atmosphere of the planet Uranus -- as has been long debated, but never definitively proven. Based on sensitive spectroscopic observations with the Gemini North telescope, astronomers uncovered the noxious gas swirling high in the giant planet's cloud tops. This result resolves a stubborn, long-standing mystery of one of our neighbors in space. Even after decades of observations, and a visit by the Voyager 2 spacecraft, Uranus held on to one critical secret, the composition of its clouds. Now, one of the key components of the planet's clouds has finally been verified. Global collaborators spectroscopically dissected the infrared light from Uranus captured by the 8-meter Gemini North telescope on Hawaii's Maunakea. The Gemini data, obtained with the Near-Infrared Integral Field Spectrometer, sampled reflected sunlight from a region immediately above the main visible cloud layer in Uranus's atmosphere. Astronomers have long debated the composition of Uranus's clouds and whether hydrogen sulfide or ammonia dominate the cloud deck, but lacked definitive evidence either way.

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