Uranus is full of gas that smells like rotten eggs

A colorless gas called hydrogen sulfide is flammable, corrosive, and smells like rotten eggs. The chemical compound may also primarily compose Uranus' upper clouds, according to a newly published study. Researchers found evidence of hydrogen sulfide in the planet's atmosphere, providing a clearer picture on how the celestial body formed.

The information comes from a study recently published in Nature. According to the researchers behind it, no one has definitively determined the composition of Uranus' cloud top; however, it's believed to be primarily made of hydrogen sulfide or ammonia. Based on their work, the researchers point toward hydrogen sulfide as the (likely) correct answer.

The study states:

Here, we present evidence of a clear detection of gaseous H2S above this cloud deck in the wavelength region 1.57–1.59 μm with a mole fraction of 0.4–0.8 ppm at the cloud top ... The detection of gaseous H2S at these pressure levels adds to the weight of evidence that the principal constituent of 1.2–3-bar cloud is likely to be H2S ice.

The Gemini North telescope located on Mauna Kea in Hawaii helped shed light on the composition, according to BBC. Scientists used the telescope's Near-Infrared Integral Field Spectrometer instrument; with it, a "fingerprint" for the clouds' composition became clear. This is a notable deviation from Saturn and Jupiter.

Both of those giant planets feature upper clouds primarily composed of ammonia ice, which some researchers thought may also be the dominant compound on Uranus. The conditions that existed when the planets formed may have shaped which of the two compounds became dominant in the upper clouds.

SOURCE: Nature