The James Webb Space Telescope (JWST) has revealed some amazing things about the Universe. From the earliest galaxies and planet-forming disks to characterizing exoplanet atmospheres, there is virtually no corner of the cosmos that Webb has not observed in extremely high resolution. This includes the Solar System, where Webb has used its sophisticated infrared instruments and spectrometers to provide the most detailed images ever taken of Jupiter, Saturn, the ice giants, and smaller objects like Dimorphos and the latest cosmic interloper detected, 3I/ATLAS.
In a recent study, an international team of researchers presented data from Webb’s Near Infrared Spectrograph (NIRSpec), which was obtained during its first observations of Saturn’s atmosphere in 2024. These observations revealed complex and mysterious things that have never been seen on any planet in the Solar System, including a series of dark, bead-like structures and an asymmetric star-shaped feature around Saturn’s polar region.
The team was led by Professor Tom Stallard of the Department of Maths, Physics, and Electrical Engineering at Northumbria University, Newcastle. It consisted of 23 scientists from institutions across the UK, the US, and France. The results were presented at the 2025 Europlanet Science Congress Joint Meeting (EPSC-DPS2025) that took place from September 7th to 12th in Helsinki. Their findings were also detailed in a paper published on August 28th in the Geophysical Journal Letters.
Hubble image in ultraviolet light showing the most comprehensive picture of Saturn’s northern aurora. Credit: NASA/ESA
As indicated in both, astronomers have spent the past three decades studying thermalized emissions in Saturn’s atmosphere caused by the positively charged molecule hydrogen-3 (H3+). These observations, conducted by ground-based and space-based telescopes, have used this molecule to explore the ionospheres of Saturn and the other gas and ice giants of the outer Solar System. However, these observations have reached a ceiling in recent decades due to atmospheric interference and the limits of existing instruments.
This changed with the deployment of the JWST, which has fundamentally revolutionized astronomers’ understanding of the outer planets in the past three years.
As Professor Stallard said in a University of Northumbria press release:
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. 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 international team of researchers, comprising 23 scientists from institutions across the UK, US, and France, made the discoveries during a continuous 10-hour observation period on 29 November 2024, as Saturn rotated beneath JWST’s view. “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 Stallard. “JWST’s incredible sensitivity has revolutionised our ability to observe these atmospheric layers, revealing structures that are completely unlike anything we’ve seen before on any planet.”
JWST’s NIRSpec instrument allowed the team to simultaneously observe H₃⁺ ions from the ionosphere 1,100 km (683.5 mi) above Saturn’s “surface,” and methane molecules in the stratosphere beneath. In the ionosphere, they observed dark, bead-like features embedded in Saturn’s polar aurorae that remained stable over hours but drifted over longer periods. Beneath that, at an altitude of 500 km (310 mi), they spotted an asymmetric star-shaped feature (with four arms instead of six) extending from the north pole towards the equator. These patterns overlaid each other at different levels, with the beads lying on top of the lopsided star pattern.
This suggests that the processes driving these processes may extend through Saturn’s atmosphere and deep into its interior. Both features could have significant implications for understanding atmospheric dynamics on gas giant planets. Said Professor Stallard:
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. 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 these features hint at mysterious processes at work, more work is needed to explain the underlying causes. In the near future, the team hopes that additional time will be granted with the JWST for follow-up observations. The structures observed may change dramatically since Saturn is currently at its equinox and the northern hemisphere is about to shift 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.
Further Reading: Northumbria University, Geophysical Research Letters