We readdress the idea that Hyperion may act as an effective source of dust
in the outer Saturnian system. Hypervelocity impacts of dust particles comi
ng from the outer irregular moons (Phoebe and several others recently disco
vered) and., to less degree, bombardment by interplanetary micrometeoroids
should eject surface material of Hyperion to planetocentric space. Unlike H
yperion, whose motion is stabilized by a strong 4: 3 mean motion resonance
with the neighbouring Titan, so that encounters with this satellite are pro
hibited, a significant fraction of the Hyperion debris should be fast enoug
h to be out of resonance. For slower ejecta, resonant locking may be destro
yed later by the plasma drag and solar radiation pressure forces. The orbit
s liberated from the resonance become unstable and experience multiple clos
e approaches to Titan. Using numerical integrations, we performed a statist
ical study of the grain trajectories to construct a spatial distribution of
dust in the Hyperion-Titan system and to find out the eventual fate of the
debris. Particles locked in resonance form an are-like structure along the
Hyperion orbit centred on Hyperion's position, this "Hyperion swarm" is po
pulated by grains of tens of micrometres in size and might be dense enough
to be detected by the Cassini spacecraft during its flyby of Hyperion. The
whole dust cloud in the Hyperion-Titan system is tilted off the equatorial
plane of Saturn and has a structure that depends on the particle radii. No
particular dust concentration in the vicinity of Titan was found. Most of t
he grains larger than similar to 5 mum in size finally collide with Titan,
whereas smaller particles are either lost in the inner part of the Saturnia
n system or hit Saturn. Our estimates of the dust influx to Titan show that
the incoming rate of Hyperion particles may exceed the direct influx of in
terplanetary dust particles. The influx of icy (H2O) particles from Hyperio
n might help to explain the observed abundance of CO and CO, molecules in T
itan's atmosphere. (C) 2001 Elsevier Science Ltd. All rights reserved.