Time-Variability of the Interplanetary Complex
by
Mark E. Bailey
Armagh Observatory, College Hill, Armagh, BT61 9DG, Northern Ireland, UK

A significant number of distant cometary nuclei have diameters in excess

of 100 km and dynamical lifetimes for transfer from source orbits extending

to the Edgeworth-Kuiper belt or Oort cloud on the order of 1 million years.

These "giant" comets are injected into the inner solar system with a frequency

comparable to that between the civilization destroying impacts of kilmetre-sized

near-Earth asteroids. Once inserted onto short-period inner solar system orbits,

giant comets survive dynamically for roughly ten thousand years, suggesting that

giant-comet debris could have been present in the inner solar system within the

past 10 to 100 thousand years. The talk will review review the astronomical

evidence for giant comets and their expected frequency of injection into the

inner solar system.

Date received: March 7, 2002