Constraints from Galileo observations on the origin of Jovian dust streams

THE Ulysses spacecraft detected streams of sub-micrometre-sized dust particles as it approached Jupiter in 1992(1,2), Although interplanetary space was known to contain dust, the presence of discrete streams was completely unexpected, The directions from which the dust grains struck the spacecraft strongly suggested that the source lay somewhere within the Jupiter system, Three origins were proposed, the comet Shoemaker-Levy 9 (ref, 3), Jupiter's gossamer ring(4), and the volcanoes on Io(5), but there was no definitive evidence for or against any of the options. Here we report the detection by the Galileo spacecraft of even more intense dust streams-including three intense dust storms of month-long duration, with impact rates up to 10 times higher than those observed by Ulysses, Our analysis of the data confirms that the dust streams originate near Jupiter; rye are able to rule out a cometary origin, but cannot yet determine conclusively whether the dust comes from Io or the ring.