  Several families of irregular moons orbit the giant planets. These moons are
thought to have been captured into planetocentric orbits after straying into a
region in which the planet's gravitation dominates solar perturbations (the
Hill sphere). This mechanism requires a source of dissipation, such as
gas-drag, in order to make capture permanent. However, capture by gas-drag
requires that particles remain inside the Hill sphere long enough for
dissipation to be effective. Recently we have proposed that in the circular
restricted three-body problem particles may become caught up in `sticky'
chaotic layers which tends to prolong their sojourn within the planet's Hill
sphere thereby assisting capture. Here we show that this mechanism survives
perturbations due to the ellipticity of the planet's orbit. However, Monte
Carlo simulations indicate that the planet's ability to capture moons decreases
with increasing orbital eccentricity. At the actual Jupiter's orbital
eccentricity, this effects in approximately an order of magnitude lower capture
probability than estimated in the circular model. Eccentricities of planetary
orbits in the Solar System are moderate but this is not necessarily the case
for extrasolar planets which typically have rather eccentric orbits. Therefore,
our findings suggest that these extrasolar planets are unlikely to have
substantial populations of irregular moons.
