High-velocity streams of dust originating from Saturn

Abstract

High-velocity submicrometre-sized dust particles expelled from the jovian system have been identified by dust detectors on board several spacecraft^1,2. On the basis of periodicities in the dust impact rate, Jupiter's moon Io was found to be the dominant source of the streams³. The grains become positively charged within the plasma environment of Jupiter's magnetosphere, and gain energy from its co-rotational electric field⁴. Outside the magnetosphere, the dynamics of the grains are governed by the interaction with the interplanetary magnetic field that eventually forms the streams⁵. A similar process was suggested for Saturn⁶. Here we report the discovery by the Cassini spacecraft of bursts of high-velocity dust particles (≥ 100 km s^-1) within ∼70 million kilometres of Saturn. Most of the particles detected at large distances appear to originate from the outskirts of Saturn's outermost main ring. All bursts of dust impacts detected within 150 Saturn radii are characterized by impact directions markedly different from those measured between the bursts, and they clearly coincide with the spacecraft's traversals through streams of compressed solar wind.