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.