An unprecedented series of dark, bead-like, and asymmetrical star-shaped formations have been identified by astronomers leveraging the capabilities of the NASA/ESA James Webb Space Telescope within Saturn’s ionosphere and stratosphere.
Near-infrared emission detections in Saturn’s ionosphere, depicted on the left, reveal an array of dark formations resembling beads interspersed within luminous auroral displays. To the right, at a depth of 500 kilometers in the stratosphere, an asymmetrical stellar pattern extends in the direction of the equator. (Image Attribution: NASA / ESA / CSA / Webb / Stallard et al.)
“This exceptional opportunity to utilize Webb provided the inaugural instance of such granular near-infrared observation of Saturn’s auroral activity and its upper atmospheric layers. The discovered outcomes were entirely unanticipated,” stated Professor Tom Stallard from Northumbria University.
“Our expectation was to observe emissions that manifested as broad bands across various atmospheric altitudes.”
“Instead, we’ve encountered finely structured patterns of both bead-like and star-shaped features. These elements, despite being separated by immense vertical distances, might possess an intrinsic connection—potentially even linking to the well-known hexagonal formation situated deeper within Saturn’s atmospheric cloud decks.”
“These observed phenomena were definitively unforeseen and currently remain entirely without explanation.”
The investigative team concentrated on detecting infrared emanations from a positively charged molecular variant of hydrogen, H3+. This ion plays a pivotal role in chemical reactions within Saturn’s atmosphere, thereby offering crucial insights into the operational chemical and physical processes at play.
The Webb telescope’s Near Infrared Spectrograph enabled the researchers to simultaneously capture data on H3+ ions originating from the ionosphere, situated approximately 1,100 kilometers above Saturn’s standard surface, and on methane molecules present in the underlying stratosphere, at an altitude of 600 kilometers.
Within the electrically charged plasma of the ionosphere, a sequence of dark, bead-like structures was observed, nestled amidst brilliant auroral halos.
These identified formations exhibited a degree of stability over several hours, though they appeared to undergo slow lateral displacement when observed over extended temporal scales.
Approximately 500 kilometers deeper, within Saturn’s stratosphere, the research group identified an asymmetrically configured star-shaped feature.
This peculiar formation was observed to extend outward from Saturn’s north polar region towards the planet’s equator.
Significantly, only four of the star’s six arms were discernible, with the remaining two being conspicuously absent, thereby resulting in a distinctly asymmetrical configuration.
“Past missions and available telescope facilities have consistently encountered substantial challenges in thoroughly investigating Saturn’s upper atmosphere, primarily due to the exceptionally faint emissions emanating from this specific region,” Professor Stallard commented.
“Webb’s unparalleled sensitivity has fundamentally transformed our capacity to examine these atmospheric strata, thereby unveiling structures that are entirely unprecedented in the study of any planet.”
The investigators meticulously mapped the precise spatial coordinates of these features. Their analysis revealed that these formations corresponded to the same geographical areas on Saturn at different altitudes. Notably, the arms of the star-shaped pattern appeared to originate from locations directly overlying the vertices of the planet’s renowned hexagon-shaped storm system in the deeper cloud layers.
This correlation strongly suggests that the underlying mechanisms responsible for generating these observed patterns may exert influence across a vertical column that traverses the entirety of Saturn’s atmosphere.
“Our hypothesis is that the dark bead-like structures may arise from intricate interactions between Saturn’s magnetosphere and its rotational atmospheric dynamics. This could potentially yield novel insights into the energy transfer mechanisms that fuel Saturn’s auroral displays,” Professor Stallard elaborated.
“The observed asymmetrical stellar formation points towards previously unrecognized atmospheric processes operating within Saturn’s stratosphere, possibly interconnected with the hexagonal storm pattern identified at lower atmospheric depths.”
“Intriguingly, the most intensely dark beads observed in the ionosphere seem to align with the most prominent arm of the star pattern in the stratosphere. However, at this juncture, it remains unclear whether a direct causal link exists or if this alignment is purely coincidental.”
While both of these newly detected features hold substantial potential for advancing our comprehension of atmospheric dynamics on gas giant planets, further diligent investigation is imperative to elucidate their fundamental origins.
The research team expresses its hope that additional observation time with the Webb telescope will be allocated in the future for follow-up studies of Saturn, enabling a more thorough exploration of these enigmatic formations.
With the planet currently experiencing its equinox, an event that recurs approximately every 15 Earth years, these structures might undergo significant transformations as Saturn’s orientation relative to the Sun shifts and its northern hemisphere transitions into autumn.
“Given that neither of these atmospheric layers is amenable to observation via ground-based telescopes, the urgency for subsequent Webb observations during this critical period of seasonal transition on Saturn is exceptionally high,” emphasized Professor Stallard, the principal author of a publication featured in the esteemed journal Geophysical Research Letters.
Furthermore, the authors presented their findings earlier this month at the EPSC-DPS2025 Joint Meeting, held in Helsinki, Finland.
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Tom S. Stallard et al. 2025. JWST/NIRSpec Detection of Complex Structures in Saturn’s Sub-Auroral Ionosphere and Stratosphere. Geophysical Research Letters 52 (17): e2025GL116491; doi: 10.1029/2025GL116491
Tom S. Stallard et al. 2025. JWST’s transformational observations of Giant Planet ionospheres. EPSC Abstracts 18: EPSC-DPS2025-817; doi: 10.5194/epsc-dps2025-1438
