Using the James Webb Space Telescope, scientists uncovered bizarre atmospheric structures on Saturn, including drifting “dark beads” in the ionosphere and an asymmetric star pattern in the stratosphere.
Both may connect to Saturn’s iconic hexagonal storm, but their true nature remains a mystery.
Webb Telescope Unveils Saturn’s Atmospheric Mysteries
A new investigation of Saturn’s upper atmosphere, carried out with the James Webb Space Telescope (JWST), has uncovered strikingly unusual features never before observed on any planet in the Solar System. The findings were unveiled last week by Professor Tom Stallard of Northumbria University during the EPSC-DPS2025 Joint Meeting in Helsinki.
“This opportunity to use JWST was the first time we have ever been able to make such detailed near-infrared observations of Saturn’s aurora and upper atmosphere. The results came as a complete surprise,” said Professor Stallard.
This video shows how the structures observed in Saturn’s ionosphere and stratosphere relate to one another. Starting with the aurora at 1100 km, the brightness is increased to reveal the dark bead-like features. The video then fades into the star-arm shapes within the underlying 600 km layer. The darkest beads in the ionosphere appear to line up with the strongest arm underneath it, but it is not clear if this is coincidental, or if it suggests coupling between Saturn’s lowest and highest layers of the atmosphere. Credit: NASA/ESA/CSA/Stallard et al 2025.
Beads, Stars, and the Unexpected Patterns
“We anticipated seeing emissions in broad bands at the various levels. Instead, we’ve seen fine-scaled patterns of beads and stars that, despite being separated by huge distances in altitude, may somehow be interconnected – and may also be linked to the famous hexagon deeper in Saturn’s clouds. These features were completely unexpected and, at present, are completely unexplained.”
The discovery was made by an international collaboration of 23 researchers from the UK, US, and France, who observed Saturn for a continuous 10-hour stretch on November 29, 2024, while the planet rotated under JWST’s gaze.
Hydrogen Ions and Methane Molecules Under the Lens
The team focused on detecting infrared emissions by a positively charged molecular form of hydrogen, H3+, which plays a key role in reactions in Saturn’s atmosphere and so can provide valuable insights into the chemical and physical processes at work. JWST’s Near Infrared Spectrograph allowed the team to simultaneously observe H₃⁺ ions from the ionosphere, 1,100 kilometers above Saturn’s nominal surface, and methane molecules in the underlying stratosphere, at an altitude of 600 kilometers.
In the electrically charged plasma of the ionosphere, the team observed a series of dark, bead-like features embedded in bright auroral halos. These structures remained stable over hours but appeared to drift slowly over longer periods.
This video of Saturn’s stratosphere shows a complex and highly surprising star-shaped structure, revealed for the first time by JWST’s unprecedented sensitivity. Four dark bands extend away from the polar region, appearing to make up four out of six arms that align with Saturn’s famous hexagon within the lower atmosphere. At this point, it is unknown why the dark arms are flowing towards the equator, or why two of the arms are missing, but the causes may be associated with the complex bead structures observed many hundreds of kilometers above in the ionosphere. Credit: NASA/ESA/CSA/Stallard et al 2025.
Lopsided Star Over Saturn’s North Pole
Around 500 kilometers lower, in Saturn’s stratosphere, the team discovered an asymmetric star-shaped feature. This unusual structure extended out from Saturn’s north pole towards the equator. Only four of the star’s six arms were visible, with two mysteriously missing, creating a lopsided pattern.
“Saturn’s upper atmosphere has proven incredibly difficult to study with missions and telescope facilities to date due to the extremely weak emissions from this region,” said Professor Stallard. “JWST’s incredible sensitivity has revolutionized our ability to observe these atmospheric layers, revealing structures that are completely unlike anything we’ve seen before on any planet.”
Connection to Saturn’s Hexagon Storm
The team mapped the exact locations of the features and found that they overlaid the same region of Saturn at different levels, with the star’s arms appearing to emanate from positions directly above the points of the storm-cloud-level hexagon. This suggests that the processes that are driving the patterns may influence a column stretching right through Saturn’s atmosphere.
“We think that the dark beads may result from complex interactions between Saturn’s magnetosphere and its rotating atmosphere, potentially providing new insights into the energy exchange that drives Saturn’s aurora. The asymmetric star pattern suggests previously unknown atmospheric processes operating in Saturn’s stratosphere, possibly linked to the hexagonal storm pattern observed deeper in Saturn’s atmosphere,” said Professor Stallard.
This video of Saturn’s ionosphere highlights the contrast in brightness between JWST’s infrared observations of the aurora and the dim bead features. The aurora itself is relatively weak, almost impossible to image from Earth, needing hours of integration time to observe using ground-based data. However, the auroral features are at least four times brighter than the brightest parts of the dark bead features, so to properly show the hidden features, the aurora are completely saturated. Credit: NASA/ESA/CSA/Stallard et al 2025.
Coincidence or Cosmic Link?
“Tantalizingly, the darkest beads in the ionosphere appear to line up with the strongest star-arm in the stratosphere, but it’s not clear at this point whether they are actually linked or whether it’s just a coincidence.”
While both features could have significant implications for understanding atmospheric dynamics on gas giant planets, more work is needed to provide explanations for the underlying causes.
Seasonal Changes and Urgency for Follow-Up
The team hopes that additional time may be granted in future to carry out follow-up observations of Saturn with JWST to further explore the features. With the planet at its equinox, which occurs approximately every 15 Earth years, the structures may change dramatically as Saturn’s orientation to the Sun shifts and the northern hemisphere moves into autumn.
“Since neither atmospheric layer can be observed using ground-based telescopes, the need for JWST follow-up observations during this key time of seasonal change on Saturn is pressing,” Stallard added.
References:
“JWST’s transformational observations of Giant Planet ionospheres” by Tom Stallard, Henrik Melin, Luke Moore, Emma Thomas, Katie Knowles, Paola Tiranti and James O’Donoghue, 8 July 2025, EPSC Abstracts.
DOI: 10.5194/epsc-dps2025-817
“JWST/NIRSpec Detection of Complex Structures in Saturn’s Sub-Auroral Ionosphere and Stratosphere” by Tom S. Stallard, Luke Moore, Henrik Melin, Omakshi Agiwal, M. Nahid Chowdhury, Rosie E. Johnson, Katie L. Knowles, Emma M. Thomas, Paola I. Tiranti, James O’Donoghue, Khalid Mohamed, Ingo Mueller-Wodarg, Leigh Fletcher, Imke de Pater, Thierry Fouchet and Sarah V. Badman, 28 August 2025, Geophysical Research Letters.
DOI: 10.1029/2025GL116491
The Saturn research was supported by grants from the Science and Technology Facilities Council (STFC), NASA Solar System Workings program, and the European Research Council. The study represents part of JWST’s ongoing revolutionary observations of our solar system’s planets.
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