JWST/NIRSpec Detection of Complex Structures in Saturn's Sub‐Auroral Ionosphere and Stratosphere

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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.
Funding Information
  • Science and Technology Facilities Council (ST/W00089X/1)
  • Science and Technology Facilities Council (ST/X003426/1)
  • Science and Technology Facilities Council (ST/W001527/2)
  • Science and Technology Facilities Council (ST/X508548/2)
  • National Aeronautics and Space Administration (80NSSC20K1045)
  • National Aeronautics and Space Administration (80NSSC21K0157)
  • HORIZON EUROPE European Research Council (723890)
  • Northumbria University

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