Final published version
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - JWST/NIRSpec Detection of Complex Structures in Saturn's Sub‐Auroral Ionosphere and Stratosphere
AU - Stallard, Tom S.
AU - Moore, Luke
AU - Melin, Henrik
AU - Agiwal, Omakshi
AU - Chowdhury, M. Nahid
AU - Johnson, Rosie E.
AU - Knowles, Katie L.
AU - Thomas, Emma M.
AU - Tiranti, Paola I.
AU - O’Donoghue, James
AU - Mohamed, Khalid
AU - Mueller‐Wodarg, Ingo
AU - Fletcher, Leigh
AU - de Pater, Imke
AU - Fouchet, Thierry
AU - Badman, Sarah V.
PY - 2025/8/28
Y1 - 2025/8/28
N2 - Plain Language Summary: Saturn's upper atmosphere is very poorly understood. Despite decades of ground‐based observations and a decade of measurements from Cassini, the incredibly weak emission from both ions and neutrals in the top of Saturn's atmosphere have proven highly illusive. Here, we describe revolutionary observations made by the JWST telescope. The incredible sensitivity of JWST/NIRSpec allows us to measure both the ionosphere and stratosphere enhanced by orders of magnitude compared to past observations. We have discovered a series of ionospheric dark ’beads', forming across a range of longitudes, away from the region with brightest aurora. We suggest it is unlikely that they are driven by underlying atmospheric processes, or infalling material from the surrounding space environment, and speculate they are forming as a result of shears between ionospheric winds. Underlying this, the upper stratosphere appears to have an atmospheric formation unlike anything previously known. A dark polar cap appears to be extending arms down into the sub‐equatorial region, with spokes reaching out as a six‐pointed star. However, two of these six arms are missing, resulting in a strangely asymmetric structure. We cannot explain how this structure has formed, but it may be associated with changes seen in the underlying atmosphere.
AB - Plain Language Summary: Saturn's upper atmosphere is very poorly understood. Despite decades of ground‐based observations and a decade of measurements from Cassini, the incredibly weak emission from both ions and neutrals in the top of Saturn's atmosphere have proven highly illusive. Here, we describe revolutionary observations made by the JWST telescope. The incredible sensitivity of JWST/NIRSpec allows us to measure both the ionosphere and stratosphere enhanced by orders of magnitude compared to past observations. We have discovered a series of ionospheric dark ’beads', forming across a range of longitudes, away from the region with brightest aurora. We suggest it is unlikely that they are driven by underlying atmospheric processes, or infalling material from the surrounding space environment, and speculate they are forming as a result of shears between ionospheric winds. Underlying this, the upper stratosphere appears to have an atmospheric formation unlike anything previously known. A dark polar cap appears to be extending arms down into the sub‐equatorial region, with spokes reaching out as a six‐pointed star. However, two of these six arms are missing, resulting in a strangely asymmetric structure. We cannot explain how this structure has formed, but it may be associated with changes seen in the underlying atmosphere.
KW - rotation period
KW - aurora
KW - stratosphere
KW - Saturn
KW - JWST
KW - ionosphere
U2 - 10.1029/2025gl116491
DO - 10.1029/2025gl116491
M3 - Journal article
VL - 52
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 17
M1 - e2025GL116491
ER -