  Streams of high speed dust particles originate from Jupiter's innermost
Galilean moon Io. After release from Io, the particles collect electric charges
in the Io plasma torus, gain energy from the co-rotating electric field of
Jupiter's magnetosphere, and leave the Jovian system into interplanetary space
with escape speeds over $\rm 200 km s^{-1}$. Galileo, which was the first
orbiter spacecraft of Jupiter, has continuously monitored the dust streams
during 34 revolutions about the planet between 1996 and 2002. The observed dust
fluxes exhibit large orbit-to-orbit variability due to systematic and
stochastic changes. After removal of the systematic variations, the total dust
emission rate of Io has been calculated. It varies between $10^{-3}$ and
$\mathrm{10} \rm kg s^{-1}$, and is typically in the range of 0.1 to $\rm 1 kg
s^{-1}$. We compare the dust emission rate with other markers of volcanic
activity on Io like large-area surface changes caused by volcanic deposits and
sightings of volcanic plumes.
