TOPIC:  "Exploring the Mysteries of the Early Bombardment
of the Moon"

Bill Bottke 	Southwest Research Institute 

Abstract:

The Moon is a facinating place that, if properly interpreted, can be
used as a Rosetta Stone for understanding the last stages of planet
formation throughout the Solar System.  This record is preserved in
the Moon's bombardment history.  Nearly 40 years after the historic
Apollo 11 landing, however, there are still enormous debates in the
scientific community about what the Moon is really telling us.  The
age of the oldest and largest known basin, South Pole-Aitken, is
unknown. The youngest basins, Imbrium and Orientale, formed 3.9 Ga,
~600 My after the Moon-forming event and far too long to have been
planetesimals leftover from terrestrial planet formation.  Examining a
range of data from across the inner solar system, I will discuss the
primary models of lunar bombardment, a plausible dynamical mechanism
capable of creating a spike of comets/asteroid impactors 3.9 Ga (Nice
model), and some of the new work we still have to do to place the Moon
into a solar system context.