Uranus’ Atmosphere Smells Like Rotten Egg Due To Hydrogen Sulfide

  • Scientists confirmed that the gas swirling at the upper atmosphere of Uranus contains hydrogen sulfide. 
  • The is the same gas that gives rotten eggs their odor. 
  • The study also indicates that the giant icy planets like Neptune and Uranus were formed farther from the Sun than Saturn and Jupiter.

Uranus is one of the least researched planets in our solar system. It has only been visited once, by Voyager 2 space probe, and that was just a flyby. No spacecraft has ever landed or orbited the planet. So the data we see are either gathered by ground-based telescopes or Earth satellite.

Astronomers have been observing Uranus for decades, but it has held on to several mysteries. One of those mysteries is its clouds’ composition. Now researchers at the University of Leicester have detected something interesting using data of Gemini North telescope.

They have confirmed that the noxious gas swirling at the upper atmosphere of Uranus contains hydrogen sulfide – the same compound that gives rotten eggs their odor. However, the discovery doesn’t come with any surprises. Some observations made in 1990s already gave clues of the presence of hydrogen sulfide in the Uranus’ atmosphere, but there was no solid evidence at that time.

How Did They Confirm This?

Uranus' Atmosphere Uranus planet | Credit: NASA

The data provided by NIFS (Near Infrared Integral Field Spectrometer) of Gemini observatory were used to sample reflected sunlight from a portion just above the visible layer of cloud of Uranus’ atmosphere. The researchers were trying to detect the line that was hardly there. However, NIFS sensitivity allowed them to detect it clearly.

We are talking about the enhanced spectroscopic absorption line — where a small amount of infrared light of reflected sunlight is absorbed by hydrogen sulfide — that are dull and difficult to detect.

Based on this detection, researchers concluded that hydrogen sulfide ice probably creates a significant component of the Uranus’ clouds at 1.2 – 3 bar. The imaginary refractive index spectrum of hydrogen sulfide ice hasn’t been computed, and therefore they can’t confirm whether this spectrum is consistent with ice.

Reference: Nature Astronomy | doi:10.1038/s41550-018-0432-1 | University of Leicester

However, very large imaginary refractive indices are not present in the complex refractive index spectra of methane, water and ammonia ices. This indicates that the particles of icy hydrogen sulfide in Uranus clouds may not be pure condensates, but may be heavily mixed or coated with photochemical compounds drizzling down from the stratosphere.

The work is exceptionally remarkable, considering the researchers have used an equipment originally developed to study black holes, for solving a decades-old mystery of our solar system.

While hydrogen sulfide is present in less amount, it’s quite interesting to theorize what would happen to you if you ever reach Uranus. Well, unpleasant smell would be your last concern; 73 Kelvin temperature and extremely suffocating atmosphere of hydrogen, methane and helium would kill you even before you smell anything.

Significance of Study

The research has a potential to uncover early solar system facts. The presence of hydrogen sulfide sets the Uranus apart from other massive planets like Saturn and Jupiter that mostly consist of ammonia.

Since hydrogen sulfide freezes at lower temperatures (191 K) as compared to ammonia (195 K), it is possible that ice crystal of hydrogen sulfide would have been present in larger amount in the early solar system, where they could have seized into newly formed planets. This indicates that the giant icy planets like Neptune and Uranus were formed farther from the Sun than Saturn and Jupiter.

Read: Jupiter’s Great Red Spot Is 100 Times Deeper Than Earth’s Oceans

Overall, the study shows that although the atmosphere of Uranus might be dreadful for humans, it’s a fertile environment for probing the early evolution of the solar system, and perhaps understanding the features of other planets beyond our solar system.

Written by
Varun Kumar

Varun Kumar is a professional science and technology journalist and a big fan of AI, machines, and space exploration. He received a Master's degree in computer science from Indraprastha University. To find out about his latest projects, feel free to directly email him at [email protected] 

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