Embajada de los Estados Unidos en Uruguay from Montevideo, Uruguay · Public domain

A planetary scientist who led the New Horizons mission to Pluto as principal investigator, directing the spacecraft that gave humanity its first close-up images of the dwarf planet after a nine-year journey. Across a career spanning 24 space missions, he has built scientific instruments flown on the Space Shuttle and Hubble, focused his research on the Kuiper Belt and Oort Cloud at the solar system's edge, and served briefly as NASA's Associate Administrator for Science before returning to research.