Abstract

The Moon is an archive of impact cratering in the Solar System throughout the past 4.5 billion years. The lunar impact record itself is controversial with several different models proposed to explain past impact flux. All of the Moon’s large impact basins were formed between 4.5 Ga and _{3.8 Ga. However, the duration and magnitude of basin-formation is not well known. It may be that there was a sudden spike in bombardment between} 3.9 to 3.8 Ga when many basins formed (this is known as the lunar cataclysm hypothesis), or it could be that there was a period of late heavy bombardment lasting from ~4.2 to 3.8 Ga. Lunar meteorite samples provide a key record of impact cratering processes from regions outside of those sampled by the Apollo missions. We are currently studying the makeup and Ar-isotope age record of impact melts in several lunar meteorites to test global models of impact bombardment and investigate compositional heterogeneity of the lunar crust. In addition to further constraining the Moon’s impact history, we have also investigated the record of asteroid and cometary material found on the Moon.