A backyard astronomer helped uncover a planetary mystery — Jupiter’s famous clouds aren’t ammonia ice but a murky mix of chemicals, sitting lower in the atmosphere than expected.
For years, astronomers believed that Jupiter’s upper clouds — responsible for its iconic pale brown belts — were made of frozen ammonia. However, a new study, combining efforts from both amateur and professional astronomers, has revealed that these clouds sit lower in the atmosphere than previously thought and consist of something entirely different: most likely ammonium hydrosulphide mixed with smog.
Citizen Scientists Join the Search
Citizen scientist Steve Hill had already demonstrated that he could map Jupiter’s atmosphere using only specially colored filters and his backyard telescope. His findings suggested that the clouds were too deep within the planet’s warm atmosphere to be made of ammonia ice.
To investigate further, Hill teamed up with Patrick Irwin from Oxford University, whose research group had previously used the advanced MUSE instrument on ESO’s Very Large Telescope (VLT) to analyze the atmospheres of gas giants.
MUSE is capable of scanning the atmosphere of Jupiter at different wavelengths, mapping out the different molecules that make up the planet’s atmosphere. This animated image, based on real MUSE data, shows how the gas giant looks at different wavelengths.
A Layered Cake of Mystery
The new study shows that this new approach with backyard telescopes or VLT/MUSE can map the abundance of ammonia in Jupiter’s atmosphere with surprising accuracy. As for clouds, the team concluded that Jupiter’s atmosphere is much like a layered cake. Clouds of ammonium hydrosulphide cover the upper layers, but sometimes there may be a decoration of ammonia ice clouds, brought to the top by strong vertical convection. The entire cake’s structure, though, is not yet fully known, and the work of citizen scientists will be key to uncovering it. So next time you are looking at Jupiter or Saturn from your backyard, you may also be unraveling the secrets still lying within our Solar System.
Explore Further: Citizen Scientists Reveal Jupiter’s Clouds Are Not What We Thought
Reference: “Clouds and Ammonia in the Atmospheres of Jupiter and Saturn Determined From a Band-Depth Analysis of VLT/MUSE Observations” by Patrick G. J. Irwin, Steven M. Hill, Leigh N. Fletcher, Charlotte Alexander and John H. Rogers, 1 January 2025, Journal of Geophysical Research: Planets.
DOI: 10.1029/2024JE008622
