Saturnʹs south polar vortex compared to other large vortices in the Solar System

Observations made by the Imaging Science Subsystem (ISS), Visible and Infrared Mapping Spectrometer (VIMS) and the long-wavelength Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft reveal that the large, long-lived cyclonic vortex at Saturnʹs south pole has a 4200-km-diameter cloud-free nearly circular region. This region has a 4 K warm core extending from the troposphere into the stratosphere, concentric cloud walls extending 20–70 km above the internal clouds, and numerous external clouds whose anticyclonic vorticity suggests a convective origin. The rotation speeds of the vortex reach 150 ± 20 m s − 1 . The Saturn polar vortex has features in common with terrestrial hurricanes and with the Venus polar vortex. Neptune and other giant planets may also have strong polar vortices.