Dr. Mustard joined the planetary group as the W. M. Keck Foundation Assistant Professor for research in 1991 and became a member of the faculty in the area of Global Enviornmental Remote Sensing after a national search in 1996. The central themes that run through his research activities are the processes that modify solid surfaces, and the spatial and temporal scales that control environmental processes on the Earth. Surfaces lie at the interface between processes that operate in the interior of a planet and external processes. The interplay between interior and exterior processes modifies the surface in many ways, depending on the specific processes involved and the time scale over which they operate. These modifications are reflected in the material properties of the surface (composition, texture, physical state) and thus surfaces integrate and record the nature and evolution of processes that have acted upon them. The fundamental tool that Mustard uses to investigate these science topics is remote sensing, with a focus towards leading technologices such as hyperspectral systems and new analytical methods. Through the use of models and analytical techniques, remotely sensed data can be reduced to provide useful information about the material properties of surfaces. However, the real challenge is to then use that information effectively and address important scientific questions. Mustard is actively involved in the application of these approaches to both planetary and environmental research topics.