JWST/NIRSpec Detection of Complex Structures in Saturn's Sub‐Auroral Ionosphere and Stratosphere
Abstract Past observations of Saturn's sub‐auroral ionosphere have provided no detailed longitudinal information, and variations in underlying stratospheric emission from methane fluorescence have never been resolved spatially. Here, we present the first near‐infrared observations of Saturn using JWST's NIRSpec‐IFU, revealing the 2.8–5.2 micron wavelength region in unprecedented detail. We observe the rotating auroral enhancement associated with planetary‐period currents, the phase of which is re‐discovered for the first time since Cassini. We discover a series of ionospheric dark beads located between 55 and 65N, that appear to be formed by local thermospheric dynamics. In the fluorescing methane, we reveal strange dark arms extending equatorward from a dark polar cap at 60N; four arms from a six‐pointed star, each extend below 45N with the final two arms missing. Neither set of features has any known analog at other planets.
Authors
- Omakshi Agiwal (ORCID: https://orcid.org/0000-0003-3999-9926)
- James O’Donoghue (ORCID: https://orcid.org/0000-0002-4218-1191)
- Emma Thomas (ORCID: https://orcid.org/0000-0002-5773-6110)
- M. N. Chowdhury (ORCID: https://orcid.org/0000-0003-3577-9395)
- Luke Moore (ORCID: https://orcid.org/0000-0003-4481-9862)
- Thierry Fouchet (ORCID: https://orcid.org/0000-0001-9040-8285)
- Leigh N. Fletcher (ORCID: https://orcid.org/0000-0001-5834-9588)
- S. V. Badman (ORCID: https://orcid.org/0000-0002-2041-1507)
- Katie Knowles (ORCID: https://orcid.org/0000-0001-5055-8115)
- Tom Stallard (ORCID: https://orcid.org/0000-0003-3990-670X)
- R. E. Johnson (ORCID: https://orcid.org/0000-0003-4696-2160)
- Imke de Pater (ORCID: https://orcid.org/0000-0002-4278-3168)
- Ingo Mueller‐Wodarg (ORCID: https://orcid.org/0000-0001-6308-7826)
- Henrik Melin (ORCID: https://orcid.org/0000-0001-5971-2633)
- Paola Tiranti (ORCID: https://orcid.org/0000-0001-7339-9495)
- Khalid Mohamed
Institutions
- Boston University (US)
- Centre National de la Recherche Scientifique (FR)
- University of Leicester (GB)
- Aberystwyth University (GB)
- Université Paris Cité (FR)
- Observatoire de Paris (FR)
- Northumbria University (GB)
- Sorbonne Université (FR)
- Sorbonne Paris Cité (FR)
- Imperial College London (GB)
- Lancaster University (GB)
- University of Reading (GB)
- University of California, Berkeley (US)
Publication Details
- Journal
- Geophysical Research Letters
- Published
- 2025-08-28
- DOI
- https://doi.org/10.1029/2025gl116491
- Citations
- 2
- Primary Topic
- Astro and Planetary Science
- Type
- article
- Field-Weighted Citation Impact
- 2.31
Funders
- National Aeronautics and Space Administration
- Northumbria University
- Nuclear Safety and Security Commission
- Science and Technology Facilities Council
- HORIZON EUROPE European Research Council