The moon provides the most clear and complete history of impact events in the inner solar system since its formation ~4.5 billion years (GY) ago. Since the moon and earth are close together in…

The moon provides the most clear and complete history of impact events in the inner solar system since its formation ~4.5 billion years (GY) ago. Since the moon and earth are close together in space, if properly interpreted, the moon's impact record can be used to gain insights into how the earth has been influenced by impacting events over billions of years. The timing of impacts on the moon, however, is not well understood. In fact, the national academy reported that interpreting this impact flux should be one of the top science priorities for NASA's return to the moon (NRC, 2007). This study focuses on obtaining geochemical and chronological data on lunar impact glasses, which are pieces of melted regolith (lunar soil) created by energetic impacting events on the moon. These impact glasses possess the composition of the target material and can be dated by the 40AR/39AR (argon) method in order to determine their age of formation. Understanding the ages of impact glasses, along with their compositions, allows for a full interpretation of the impact history of the moon, and from them, we can begin to piece together information about the rate of impact events and their effects on earth. Over 500 lunar impact glasses from three apollo landing sites (apollo 14, 16, and 17) have been analyzed geochemically by the PI, and 70 of them have been dated by the 40AR/39AR method (also by the PI). However, only a handful of impact glasses have been studied in detail sufficient for publication in a professional journal (delano ET AL. 2007, zellner ET AL. 2009A, zellner ET AL. 2009B). IT is my intent to study additional glasses in the detail required for scientific publication. Several glasses show age relationships that may coincide with significant species extinction episodes on earth, and others show a global lunar bombardment that is not recorded in terrestrial sediments. Whether or not additional glass ages can be reconciled with impact or extinction events, the data are important to understanding lunar impact processes in general. The ages of all analyzed glasses will thus add significantly to the current data set of lunar sample ages. Finally, the results of this study will help to constrain models for the time-dependent flux of impactors in the inner solar system.