Discovery about Jupiter's clouds leaves astronomers "astonished"

Jupiter has always fascinated stargazers with its colorful bands of clouds and iconic weather patterns like the Great Red Spot. Now, new research from a team of citizen scientists challenges the old idea that its visible clouds are formed of ammonia ice.

These findings add clarity to how Jupiter’s cloud layers and atmospheric dynamics work. They have also been published in the Journal of Geophysical Research – Planets.

Astronomy enthusiasts have followed Jupiter for many years, mapping its shifting features from backyards and observatories.

Reports of dramatic storms, swirling vortexes, and bands of different hues have long intrigued experts and hobbyists alike. Yet the real composition of the planet’s most visible cloud layers remained unsettled.

Fresh eyes on Jupiter’s clouds

A fresh approach emerged when amateur astronomer Dr Steven Hill, based in Colorado, studied Jupiter’s atmosphere with commercially available telescopes and colored filters.

By capturing images at specific wavelengths, he measured the abundance of ammonia and the height of cloud tops. His observations suggested that the clouds on Jupiter sit at depths too warm for ammonia ice to form.

Soon after, Professor Patrick Irwin from the University of Oxford’s Department of Physics applied Dr Hill’s analytical approach to observations from the Multi Unit Spectroscopic Explorer at the European Southern Observatory’s Very Large Telescope in Chile.

Professor Irwin and his team simulated how light interacts with gases and clouds in a computer model. Their results confirmed that the main cloud layers are deeper than expected and unlikely to be ammonia ice clouds.

Keeping it simple

“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!” Professor Irwin enthused.

“These results show that an innovative amateur using a modern camera and special filters can open a new window on Jupiter’s atmosphere and contribute to understanding the nature of Jupiter’s long-mysterious clouds and how the atmosphere circulates.”

Dr Hill’s straightforward techniques uncovered a more detailed picture of Jupiter’s weather. By examining small differences in brightness through narrow color filters, he produced ammonia maps that cost much less to calculate than complex modeling.

“I always like to push my observations to see what physical measurements I can make with modest, commercial equipment,” Dr. Hill explained, with great enthusiasm.

“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!”

Jupiter’s clouds and citizen science

The ammonia maps derived from these simpler methods make it easier for citizen scientists and hobbyists to watch changes in Jupiter’s atmosphere.

Researchers note that visible shifts, such as the appearance of small storms or fluctuations around Jupiter’s famous bands, can be tracked alongside these measurements of ammonia. The same goes for notable features like the Great Red Spot.

“A special advantage of this technique is that it could be used frequently by amateurs to link visible weather changes on Jupiter to ammonia variations, which could be important ingredients in the weather,” explained John Rogers of the British Astronomical Association, who contributed to the study.

Occasional ammonia ice clouds

In certain spots, strong updrafts can still create puffy ammonia ice clouds. Spacecraft such as NASA’s Galileo and Juno have documented small white clouds, complete with shadows, floating above a darker deck.

Researchers suggest that, in those places, the rapid uplift allows the ammonia to condense before it is broken apart or mixed with photochemical haze.

This idea explains why occasional bright patches of ammonia ice appear in the midst of Jupiter’s typically darker cloud deck.

Photochemistry is thought to play a key role in producing smog-like material. When ammonia-rich air is driven upward, exposure to sunlight triggers reactions that either destroy ammonia or blend it with other products.

The result is a cloud deck that tends to contain ammonium hydrosulphide and tinted substances, giving Jupiter its reddish-brown tones.

Similar phenomena observed on Saturn

Inspired by these Jupiter results, Professor Irwin’s team extended the same filter-based analysis to data from Saturn.

Their models mirrored the findings of other researchers, including those using the James Webb Space Telescope.

Saturn’s clouds also seem to lie deeper than the ammonia condensation level. This indicates that smog production and dynamic weather processes could be at play there as well.

Such similarities offer fresh avenues for connecting the gas giants. Both planets show layered atmospheres shaped by rising and sinking air parcels, along with chemical reactions triggered by sunlight.

Whether these parallels arise from identical processes or represent shared ingredients in different conditions remains an active topic of study.

Why Jupiter’s clouds matter

These results open up opportunities for more frequent measurements of Jupiter’s atmosphere. The less complex technique gives amateur and professional astronomers a handy tool for examining weather patterns and gas distributions on short notice.

That can support large-scale efforts to piece together how storms, jets, and other atmospheric elements evolve over days, weeks, and even years.

With deeper insights into both Jupiter and Saturn, researchers plan to continue mapping cloud levels and chemical makeup. They hope to see if these discoveries match what spacecraft detect from orbit.

The combination of space-based instruments and Earth-based telescopes, now supported by citizen science efforts, may yield an even fuller understanding of these swirling worlds.

The full study was published in the Journal of Geophysical Research: Planets.

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