My research focuses on the geological history and evolution of the Moon and processes of impact and volcanism that have shaped its surface. I study the Moon largely by remote sensing, whereby composition and physical properties are determined through analysis of data returned by orbiting spacecraft and from Earth-based telescopic sensing. I combine this information with data from photographs and lunar samples obtained by the manned Apollo missions to reconstruct the nature, composition, and history of the Moon. Because impact and volcanism are the principal processes that have shaped the Moon and other terrestrial planets, I study impact craters and lava flows on the Earth as guides for interpreting planetary histories. I was Deputy Leader of the Science Team for the Clementine mission to the Moon, which mapped the Moon's topographic shape and surface color in the visible and near-infrared parts of the spectrum (where information on mineral composition can be extracted).
In recent years, I have become interested in the processes and history of the poles of the Moon, which have a unique environment and harbor significant water ice deposits. Combined with near-constant solar illumination, the poles are thus ideal locales for future permanent human presence. I was the Principal Investigator of the Mini-SAR experiment on the Indian Chandrayaan-1 mission to the Moon, which mapped the Moon from 2008-2009. The Mini-SAR imaging radar mapped the permanently dark regions of the poles and found reflections diagnostic of water ice deposits in permanently shadowed craters. I am a team member of a similar experiment, the Mini-RF, currently orbiting the Moon on NASA’s Lunar Reconnaissance Orbiter, from 2009 to present. I am currently working on plans for follow-up robotic missions to the surface of the lunar poles to document the extent and variability of water ice there.