JWST reveals dark beads and lopsided star patterns in Saturn’s atmosphere

A study of Saturn’s atmospheric structure using data from the James Webb Space Telescope (JWST) has revealed complex and mysterious features unseen before on any planet in our solar system.

The results were presented by Prof Tom Stallard of Northumbria University, UK, at the EPSC-DPS2025 Joint Meeting in Helsinki, and published in the journal Geophysical Research Letters.

“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 Stallard.

“We anticipated seeing emissions in broad bands at 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.

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.

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 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.”

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 Stallard.

“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.

The team hopes that additional time may be granted in the 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.