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Dark, radial spokes in the rings of Saturn have puzzled planetary astronomers ever since they were discovered by the Voyager spacecraft in the early 1980's.

Today, at the Royal Astronomical Society National Astronomy Meeting here, scientists described how the enigmatic features could be caused by thunderstorms and lightning. …

No single theory has been able to explain all the observed characteristics of the spokes, such as their locations, shapes, clustering behaviour, and - most notably - their puzzling absence between October 1998 and September 2005.

Enter the thunderstorm model, proposed by Dr Geraint Jones [¹û¶³Ó°Ôº Mullard Space Science Laboratory], and colleagues, and presented at the meeting by team member Christopher Arridge. According to this idea, energetic beams of electrons produced above these storms are transported to the rings by Saturn's magnetic field, where they charge the dust and lift it out of the ring plane. …

Their absence between 1998 and 2005 - about one quarter of a Saturnian year - may be just a seasonal effect in the occurrence of thunderstorms at this particular latitude, the astronomers speculate. …

Confirmation could come from NASA's Cassini probe, which is orbiting Saturn. …

Govert Schilling, 'Science'