Clark is a planetary scientist whose research specializes in studies of asteroids and cratering of planetary surfaces using telescopes, spacecraft, and computers. He is former Chair of the Division for Planetary Sciences (DPS) of the American Astronomical Society and was the first editor of the Journal of Geophysical Research: Planets. He is a winner of the DPS’s Carl Sagan Award for Excellence in Public Communication in Planetary Sciences. Clark was on the science teams of the Galileo, Near-Earth Asteroid Rendezvous (NEAR-Shoemaker), and MESSENGER missions.

Clark has a bachelor’s degree in astronomy (Harvard), a master’s in meteorology (MIT), and a PhD in planetary science (MIT). For many years he was at the Planetary Science Institute (SAIC) in Tucson, and he has recently retired from Southwest Research Institute (SwRI) in Boulder, where he worked since 1996.