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- What are Jupiter\u2019s clouds made of?<\/strong> Until now, scientists thought they were composed of ammonia ice crystals.<\/li>\n
- But new observations from citizen scientists<\/strong>, working with professional astronomers, suggest the clouds are deeper in Jupiter\u2019s atmosphere, where it\u2019s too warm for ammonia.<\/li>\n
- So ammonium hydrosulfide and smog<\/strong> might instead be the primary ingredients of Jupiter\u2019s clouds. These ingredients could also produce the distinct reddish and brownish colors in the clouds.<\/li>\n<\/ul>\n
Even in a small telescope, you can see that Jupiter is wrapped in colorful bands of clouds. Scientists have long believed these clouds were composed of ammonia ice crystals. But a new study from citizen scientists and professional astronomers suggests the clouds are deeper in Jupiter\u2019s atmosphere than previously realized, at a depth too warm for ammonia ice crystals. The University of Oxford in the U.K. led the new study, and the researchers said on January 6, 2025, that \u2013 instead of ammonia \u2013 Jupiter\u2019s clouds are made of ammonium hydrosulfide and smog. These ingredients could produce the distinct reddish and brownish colors in the clouds.<\/p>\n
The researchers published their peer-reviewed findings in the Journal of Geophysical Research \u2013 Planets<\/em> (JGR Planets<\/em>) on January 1, 2025.<\/p>\n
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Mapping Jupiter\u2019s clouds<\/h3>\n
Work by amateur astronomer and citizen scientist Steven Hill in Colorado inspired the new study. He devised a new way of mapping Jupiter\u2019s clouds, using commercially-available telescopes and special color filters. His work revealed that even amateur astronomers could map the amount of ammonia in the clouds.<\/p>\n
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? Amateur astronomer Steven Hill used commercial telescopes and innovative coloured filters to map Jupiter\u2019s atmosphere, revealing groundbreaking insights.<\/p>\n
The planet’s primary clouds are deeper than expected, suggesting ammonium hydrosulphide \u2013 not ammonia ice #CitizenScience<\/a> pic.twitter.com\/Kk9Z9vZfsu<\/a><\/p>\n
\u2014 MPLSOxford (@mplsoxford) January 8, 2025<\/a><\/p>\n<\/blockquote>\n
MUSE observations of Jupiter\u2019s clouds<\/h3>\n
In the new follow-up study from the University of Oxford, Patrick Irwin used Hill\u2019s method for his own observations of Jupiter. The research team used the Multi-Unit Spectroscopic Explorer (MUSE) instrument at the European Southern Observatory\u2019s Very Large Telescope (VLT) in Chile. The paper stated:<\/p>\n
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In a recent paper, it has been shown that it is possible for backyard astronomers to make observations of Jupiter with three to four spectral filters that can be processed to map the abundance of ammonia in Jupiter\u2019s atmosphere. Here we test the reliability of this filter-imaging technique by applying it to VLT\/MUSE observations of Jupiter and show that the method yields surprisingly reliable results that agree closely with more sophisticated analyses of these observations, and which are also consistent with observations made at microwave wavelengths by Juno and the Very Large Array.<\/p>\n<\/blockquote>\n
Spectroscopic analysis<\/h3>\n
MUSE uses spectroscopy \u2013 the study of the absorption and emission of light and other radiation by matter \u2013 to analyze its targets. On Jupiter, different gases show up at different wavelengths. The results indicated the clouds were, in fact, made of ammonium hydrosulfide and smog.<\/p>\n
So, why aren\u2019t the clouds made of ammonia? As noted, the temperature at the altitude of the clouds is too warm for ammonia to condense into ice crystal clouds. Likewise, when moist, ammonia-rich air rises upward, the ammonia is either destroyed or mixes with other photochemical products (created by the effects of light), ie. smog. This happens before ammonia ice particles can form and become clouds. The smoggy photochemicals also give the clouds their distinctive reddish and brownish colors.<\/p>\n
There may still be smaller regions where the updrafts of ammonia are faster, allowing the ammonia ice particles to form. This includes smaller white clouds that spacecraft have seen floating above the main cloud deck below.<\/p>\n
![\"Long](\"https:\/\/earthsky.org\/upl\/2025\/01\/Jupiter-clouds-Juno-Kevin-Gill-November-29-2021.jpg\")
View larger. | Juno obtained this closeup view of storm clouds on Jupiter on November 29, 2021. Scientists still think that some smaller white higher-altitude clouds, like those above the oval at the bottom of the image, are composed of ammonia ice crystals. Image via NASA\/ JPL-Caltech\/ SwRI\/ MSSS\/ Kevin M. Gill (CC BY 3.0).<\/figcaption><\/figure>\n Previous hints<\/h3>\n
Astronomers saw hints of the ammonium hydrosulfide and smog before with MUSE, but they had not corroborated those results yet. The methods were too complex and only a few groups of astronomers in the world had access to the data.<\/p>\n
But now, the new results matched those from Hill and his team. The new method is also simpler, faster and less expensive. Irwin said:<\/p>\n
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I am astonished that such a simple method is able to probe so deep in the atmosphere and demonstrate so clearly that the main clouds cannot be pure ammonia ice! These results show that an innovative amateur using a modern camera and special filters can open a new window on Jupiter\u2019s atmosphere and contribute to understanding the nature of Jupiter\u2019s long-mysterious clouds and how the atmosphere circulates.<\/p>\n<\/blockquote>\n
Hill added:<\/p>\n
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I always like to push my observations to see what physical measurements I can make with modest, commercial equipment. The hope is that I can find new ways for amateurs to make useful contributions to professional work. But I certainly did not expect an outcome as productive as this project has been!\u2019<\/p>\n<\/blockquote>\n
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#Jupiter<\/a>‘s clouds, once thought to be #Ammonia<\/a> ice, are now identified as ammonium hydrosulfide mixed with smog. This insight, aided by citizen science, reshapes our understanding of the gas giant’s #Atmosphere<\/a>. @UniofOxford<\/a> <\/p>\n
- But new observations from citizen scientists<\/strong>, working with professional astronomers, suggest the clouds are deeper in Jupiter\u2019s atmosphere, where it\u2019s too warm for ammonia.<\/li>\n