This project will result in the upgrading of the rare gas mass spectrometry laboratory in the Department of Marine Geology and Geophysics at the University of Miami. The upgrade will allow the measurement of xenon and krypton isotopes to be made with sufficient precision to carry out research projects aimed at investigating the abundances of these isotopes in rocks with a mantle signature. The abundances of these isotopes in mantle- derived samples (e.g., in mid-ocean ridge basalts) holds important clues about the timing of the degassing of the Earth, the resultant formation of the atmosphere, and the present structure and evolution of the mantle.