This grant supports the acquisition of a frequency quintupled (193 nm wavelength) deep ultraviolet (DUV) laser to be interfaced with inductively coupled plasma mass spectrometers (both a quadrupole and a multicollector) in the Department of Earth and Planetary Sciences (EAPS) at Harvard University. The laser ablation system will allow continued studies requiring in situ and spatially resolved isotopic analysis of geological and extraterrestrial materials. The laser system will support research by several faculty members at Harvard including Stein Jacobsen (crust-mantle geochemistry and cosmochemistry), Dan Schrag (marine chemistry and paleoceanography), Paul Hoffman (Neoproterozoic tectonics and climate) and Heinrich Holland (evolution of Earth's early atmosphere) as well as their graduate students and postdocs. ***