Philip R. Christensen is a Regents Professor and the Ed and Helen Korrick Professor in the Department of Geological Science at Arizona State University. He completed his Ph.D. in Geophysics and Space Physics at UCLA in 1981. His research interests focus on the composition, physical properties and processes, and morphology of planetary surfaces, with an emphasis on Mars and the Earth. A major element of his research has been the design and development of spacecraft infrared remote sensing instruments. Christensen is the Principal Investigator for the 2001 Mars Odyssey Thermal Emission Imaging System (THEMIS) instrument, and the Thermal Emission System (TES) instrument on Mars Global Surveyor. He is also a Co-Investigator on the Mars Exploration Rover missions, responsible for building and operating the Mini-TES instruments. His research uses infrared spectroscopy, radiometry, laboratory spectroscopic measurements, field observations, and numerical modeling, and has taken him to field sites in the western U.S., Hawaii, Mexico, and South America. Since the mid-1990's he has pursued the use of spacecraft observations to study environmental and urban development problems on Earth. Christensen was awarded NASA's Exceptional Scientific Achievement Medal in 2003 for his pioneering scientific observations of Mars in the infrared, and was elected as a Fellow of the American Geophysical Union in 2004.