Something strange is stirring in Saturn’s skies. Astronomers using the James Webb Space Telescope have spotted something entirely new in Saturn’s atmosphere: a string of dark, bead-like features high above a strange, uneven star-shaped pattern. These unexpected structures haven’t been seen on any other planet and scientists aren’t yet sure what’s causing them.
“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,” said Professor Tom Stallard of Northumbria University, lead author of the new study published in Geophysical Research Letters. “The results came as a complete surprise.”
A Strange Show Over Saturn
For ten continuous hours on November 29, 2024, Webb’s Near Infrared Spectrograph (NIRSpec) fixed its gaze on Saturn. The timing was fortuitous: Saturn was approaching equinox. During Saturn’s equinox, sunlight falls evenly across the planet’s equator, but this seasonal shift occurs just once every 15 Earth years. The planet was also rotating in a way that allowed scientists to scan both the upper ionosphere and the deeper stratosphere. These two atmospheric layers have long been considered elusive.
In the ionosphere, more than a thousand kilometers above Saturn’s cloud tops, the telescope spotted something striking: a necklace of dark beads embedded within glowing auroral halos. They stretched between 55° and 65° north latitude, in the region known as the sub-auroral zone.
“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,” Stallard said in a press release. “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.”
But this wasn’t the only strange thing.
Roughly 500 kilometers below the beads, in the planet’s stratosphere, JWST captured a sprawling, asymmetric, four-armed star shape—dark, jagged extensions of a polar cap reaching toward the equator. It appeared to be a six-pointed star with two arms missing, creating an eerie imbalance.
Mysteries Above the Hexagon
The features raised immediate questions. Firstly, what are they? Secondly, what’s causing them, and are they related to one another?
The team discovered that the beads and the star-shape lie directly above and below each other. They’re layered in the same region of the planet’s atmosphere but separated by hundreds of kilometers. This stacking suggests a possible vertical “column” of activity stretching through Saturn’s skies. This suggests that there could be a connection between the two, but this is far from clear.
“Tantalizingly, the darkest beads in the ionosphere appear to line up with the strongest star-arm in the stratosphere,” Stallard noted, “but it’s not clear at this point whether they are actually linked or whether it’s just a coincidence”.
What is clear is that the features may somehow connect to another famous curiosity: Saturn’s hexagon.
First discovered in 1980 by NASA’s Voyager spacecraft, the hexagon is a six-sided storm hovering over Saturn’s north pole. A high-speed jet stream likely forms it, but scientists still don’t fully understand its dynamics. Researchers now think JWST’s observations tie the lopsided star to this deeper vortex.
“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 Stallard.
Forces Collide in Saturn’s Skies
The beads themselves are equally mysterious.
They don’t match any known atmospheric pattern seen on Saturn, Jupiter, or any other planet. Nor are they likely to be caused by falling material from Saturn’s rings—something that’s known to affect the planet’s ionosphere, particularly around the magnetic footprint of the moon Enceladus. That area, however, showed no corresponding signal in the new data.
Instead, Stallard and colleagues speculate that the beads might be born of violent shearing winds high in the thermosphere. These winds—some sub-rotating, some super-rotating—could be colliding at the boundaries of opposing atmospheric cells, generating instability.
The team considered one possibility: Kelvin-Helmholtz instabilities, which occur when two fluid layers move past one another at different speeds. On Earth, they can create dramatic wave-like clouds. On Saturn, perhaps, they manifest as beads.
“We suggest it is unlikely that they are driven by underlying atmospheric processes, or infalling material from the surrounding space environment,” the authors wrote in their study. Instead, they may result from shears between ionospheric winds.
JWST Has Good “Eyes”
Saturn’s atmosphere has long held secrets that resisted even Cassini, the flagship NASA mission that orbited the planet from 2004 to 2017. The upper atmosphere, in particular, is dim and elusive. JWST, with its powerful infrared sensitivity, is now pulling back the veil.
“These features were completely unexpected and, at present, are completely unexplained,” Stallard said. But he also believes they could help provide new insights into the energy exchange that drives Saturn’s aurora. It could also potentially inform how we understand Earth’s own thermosphere, which shares similar dynamic processes.
Already, the study has reclaimed one lost metric from the Cassini era: the “planetary-period phase,” a measure of how certain currents align with the planet’s rotation. Understanding that could offer a more precise model of Saturn’s magnetosphere.
The research team hopes JWST will return its gaze to Saturn soon, especially during this rare equinox period. The planet’s atmospheric patterns are likely to change dramatically as the Sun shifts southward—revealing more, or perhaps different, patterns.
“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 emphasized.
The paper JWST/NIRSpec detection of complex structures in Saturn’s sub-auroral ionosphere and stratosphere was published in Geophysical Research Letters on 28 August 2025. https://doi.org/10.1029/2025GL116491
