  The irregular satellites of outer planets are thought to have been captured
from heliocentric orbits. The exact nature of the capture process, however,
remains uncertain. We examine the possibility that irregular satellites were
captured from the planetesimal disk during the early Solar System instability
when encounters between the outer planets occurred (Nesvorny, Vokrouhlicky &
Morbidelli 2007, AJ 133; hereafter NVM07). NVM07 already showed that the
irregular satellites of Saturn, Uranus and Neptune were plausibly captured
during planetary encounters. Here we find that the current instability models
present favorable conditions for capture of irregular satellites at Jupiter as
well, mainly because Jupiter undergoes a phase of close encounters with an ice
giant. We show that the orbital distribution of bodies captured during
planetary encounters provides a good match to the observed distribution of
irregular satellites at Jupiter. The capture efficiency for each particle in
the original transplanetary disk is found to be (1.3-3.6)x10^-8. This is
roughly enough to explain the observed population of jovian irregular moons. We
also confirm NVM07's results for the irregular satellites of Saturn, Uranus and
Neptune.
