Richard Greenberg is Professor of Planetary Sciences at the University of Arizona. As a celestial mechanician, his research interests span all aspects of planetary motions, especially those that involve nongravitational effects like collisions and tides, including formation of planets, extra-solar planetary systems, evolution of asteroids and meteorites, and the orbits of satellites. As a member of the imaging team for the Galileo mission to Jupiter, he became especially engaged in interpretation of the processes that have shaped the satellite Europa. His new book “Unmasking Europa” has been very well received, including favorable reviews in Sky and Telescope, Nature, and NASA’s Astrobiology magazine.