D/H as a Measure of Chemical Imhomogeneity in our Galaxy

Accurate measurements of interstellar deuterium abundances along lines of sight extending out to several hundred parsecs by FUSE and other instruments is making D/H a useful tool for understanding Galactic chemical evolution. We find that the gas inside of the Local Bubble is chemically homogeneous, but that large variations in D/H beyond the Local Bubble are real and challenge present concepts of chemical evolution. A new set of models is needed that will include spatially dependent infall of relatively unprocessed material, depletion of D onto grains, and appropriate mixing timescales. $