Hexagonal cloud pattern around north pole of Saturn
Saturn's hexagon is a persistent approximately hexagonal cloud pattern around the north pole of the planet Saturn, located at about 78°N.[1][2][3]
The sides of the hexagon are about 14,500 km (9,000 mi) long,[4][5][6][7] which is about 2,000 km (1,200 mi) longer than the diameter of Earth.[8] The hexagon may be a bit more than 29,000 km (18,000 mi) wide,[9] may be 300 km (190 mi) high, and may be a jet stream made of atmospheric gases moving at 320 km/h (200 mph).[4][5][10] It rotates with a period of 10h 39m 24s, the same period as Saturn's radio emissions from its interior.[11] The hexagon does not shift in longitude like other clouds in the visible atmosphere.[12]
Saturn's hexagon was discovered during the Voyager mission in 1981, and was later revisited by Cassini-Huygens in 2006. During the Cassini mission, the hexagon changed from a mostly blue color to more of a golden color. Saturn's south pole does not have a hexagon, as verified by Hubble observations. It does, however, have a vortex, and there is also a vortex inside the northern hexagon.[13] Multiple hypotheses for the hexagonal cloud pattern have been developed.
^NOTE: A planar hexagon width (diameter) is twice the side (radius); but since the planet Saturn approximates an oblate spheroid, the radius of such an hexagon may be a bit greater than its side length (ie, 14,500 km), making the width (diameter) a bit greater than 29,000 km.
^Baines, Kevin H.; Momary, Thomas W.; Fletcher, Leigh N.; Showman, Adam P.; Roos-Serote, Maarten; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D. (2009). "Saturn's north polar cyclone and hexagon at depth revealed by Cassini/VIMS". Planetary and Space Science. 57 (14–15): 1671–1681. Bibcode:2009P&SS...57.1671B. doi:10.1016/j.pss.2009.06.026.