Mysterious 'Spokes' in Saturn's Rings Are Still There

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Saturn's Ring Spokes Persist
Ring spokes can still be observed in Saturn's rings. Image taken on Oct. 19, 2013. (Image credit: NASA/JPL-Caltech/Space Science Institute)

There are many mysteries about the enigmatic ringed gas giant, but the curious mechanism behind Saturn’s ‘spokes’ is one of the more intriguing puzzles. And in new observations from NASA’s Cassini mission, these bright features seem to be persisting in Saturn’s darkened B ring.

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Observed first during the Voyager spacecraft flybys in the early 1980′s, it was realized that these strange features, which flare out like spokes on a bicycle wheel, were not caused by gravitational interactions with the planet, moons or ring material. Further observations were made by Cassini in 2005 when it was confirmed the spokes are likely related to the gas giant’s global magnetic field.

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The leading theory is that charged dust particles suspended above and below the rings are interacting with Saturn’s magnetic field, causing the spokes to rotate with the planet’s interior spin. They are also thought to be seasonal over Saturn’s near-30 year solar orbit — they vanish during Saturn’s midwinter and midwinter, only to reappear around the Saturnian equinox. As Saturn’s northern hemisphere approaches summer solstice, astronomers predict the spokes will disappear.

This observation was taken when Cassini was zooming approximately 1.2 million miles (1.9 million kilometers) above Saturn’s ring plane in October 2013.

Ian O'Neill
Media Relations Specialist, NASA's Jet Propulsion Laboratory

Ian O'Neill is a media relations specialist at NASA's Jet Propulsion Laboratory (JPL) in Southern California. Prior to joining JPL, he served as editor for the Astronomical Society of the Pacific‘s Mercury magazine and Mercury Online and contributed articles to a number of other publications, including Space.com, Space.com, Live Science, HISTORY.com, Scientific American. Ian holds a Ph.D in solar physics and a master's degree in planetary and space physics.