For decades, scientists have posited Uranus' upper atmosphere contains hydrogen sulfide, the gas that gives rotten eggs their foul smell, but the idea was not proven until an worldwide team of researchers took a close look at the planet, in a way like never before.
With the help of Near-Infrared Integral Field Spectrometer (NIFS), an optical instrument that combines imaging capabilities and spectrographic at the Gemini North telescope in Hawaii, the researchers analyzed the cloud cover of the planet composed from the hydrogen sulfide gas that gives noxious, rotten eggs scent.
For a long time, scientists were puzzled by Uranus's continuum microwave adsorption spectrum - it was missing a component that atmospheric models couldn't account for. It filters the sunlight received above the Uranus clouds.
"The implications of this are that during the formation of the solar system, Uranus (and probably Neptune) formed at a greater distance from the sun where it was cold enough that both ammonia and hydrogen sulfide were in condensed icy form and thus easily incorporated into the growing planetary embryos that would eventually become Uranus (and Neptune)", Irwin said.
"While the lines we were trying to detect were just barely there, we were able to detect them unambiguously thanks to the sensitivity of NIFS on Gemini, combined with the exquisite conditions on Maunakea".
'Although we knew these lines would be at the edge of detection, I made a decision to have a crack at looking for them in the Gemini data we had acquired'.
This image of a crescent Uranus, taken by Voyager 2 on January 24, 1986, reveals its icy blue atmosphere.
When the magnetosphere is open, it allows solar wind to flow in.
The researchers suspect solar wind reconnection takes place upstream of Uranus's magnetosphere at different latitudes, causing magnetic flux to close in various parts.
The study of the hydrogen sulfide and other gases swirling over other planets could be the key to better understand how the solar system's planets formed, with some being rocky bodies, while others are gas and ice giants. Ammonia is made of nitrogen bonded with hydrogen, while hydrogen sulfide is hydrogen bonded with sulfur.
And, while it's lower than previously expected, they say the unsavoury smell wouldn't be the worst of it.
"If an unfortunate human were ever to descend through Uranus' clouds, they would be met with very unpleasant and odiferous conditions", said Patrick Irwin, first author of the study and a physics professor at the University of Oxford. Scientists have previously inferred that the planet's atmosphere contained ammonia and hydrogen sulfide based on the lack of certain light wavelength, but it wasn't directly observed.