Saturn's hexagon

Saturn's hexagon is a persistent six-sided jet stream encircling the planet’s north polar region, with a storm at its center. Its straight sides and stable shape make it a striking example of a planetary atmospheric wave.

Rossby wave: A large-scale atmospheric wave produced by the variation of planetary rotation with latitude. Rossby waves can organize flow along the jet into the hexagon’s repeating bends.
Voyager 1: A NASA spacecraft launched in 1977 that conducted a flyby of Saturn in 1980. Its images provided the first clear view of the north-polar hexagon.
Saturn's north polar vortex: A large rotating storm system centered over Saturn’s north pole. This central vortex occupies the interior of the hexagonal jet.
Saturn's atmospheric dynamics: The motions and physical processes that shape Saturn’s atmosphere. The hexagon’s origin depends on how Saturn’s deep, rapidly rotating atmosphere drives its polar jet.
Barotropic instability: An instability that develops when horizontal shear in a fluid flow releases kinetic energy into disturbances. It is one proposed route by which a zonal jet can develop persistent meanders.
Voyager 2: A NASA spacecraft launched in 1977 that flew past Saturn in 1981. Its Saturn observations helped confirm the hexagon was a persistent atmospheric feature.
Saturn's south polar vortex: A persistent cyclone located over Saturn’s south pole. It offers a polar comparison, but lacks the north’s prominent six-sided boundary.
Saturn's differential rotation: The variation of Saturn’s atmospheric rotation speed with latitude and depth. Measurements of the polar jet’s speed constrain models of the hexagon’s formation.
Jet stream: A narrow band of strong winds flowing through a planetary atmosphere. The hexagon is a distinctive shape formed by Saturn’s north-polar jet stream.
Cassini–Huygens: A NASA–ESA mission that explored Saturn and its system from 2004 to 2017. Cassini tracked the hexagon across seasons and observed its cloud structure in detail.

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Extraterrestrial vortexBroader topic: Its central polar vortex sits within an unusual polygonal atmospheric circulation.