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Keywords:

  • Saturn;
  • atmosphere;
  • dynamics

[1] Here we report the discovery at the upper cloud level of an extremely narrow and strong prograde jet, centered in the middle of the broad equatorial jet. Measurements from images obtained by the Cassini Imaging Science Subsystem (ISS) show that the jet reaches 430 ms−1 ± 16 m s−1 with a peak speed difference of 180 ms−1 relative to nearby latitudes at 60 mbar and 390 ms−1 ± 23 m s−1 at depths > 500 mbar spanning ∼6° about the equator . Contrarily to what is observed in other latitudes, its velocity increases with altitude. This jet is the first of its kind to be discovered on any of the giant planets, and adds to our three-dimensional understanding of Saturn's stratospheric wind field.