Zusammenfassung
We have reevaluated the impact rates for the planets from ecliptic
comets using the integrations in H. Levison and M. Duncan (1997,
Icarus 127, 13-32; LD97), We fmd that the current impact rates on
the giant planets are actually about four times smaller than LD97's
values due to differences in methods of calculating the relevant
timescales. The newly calculated impact rates are listed in Table
I. However, if the objects leaving the Kuiper belt were primarily
on high inclination orbits, then the impact rates on the giant planets
are larger than those in Table I by a factor less than or similar
to 2. We discuss the dynamics of objects hitting the giant planets
in detail, including measurements of the impact velocities. We find
that 21% of the objects that hit Jupiter in our simulations were
bound to the planet before the impact. The fraction of bound impactors
for Saturn is much lower, Jupiter, Saturn, and Uranus have a significant
apex-antapex asymmetry for the unbound impactors. (C) 2000 Academic
Press.
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