AGU member since 1989. Director of Sciences and Exploration, NASA Goddard Space Flight Center. Scientific interests include the volatile inventories and geochemical evolution of Mars and Earth; early solar system processes as recorded by primitive meteorites; prebiotic chemistry and water-rock interaction on asteroids; light element isotopic analysis using the ion microprobe; robotic and human exploration of the Moon, Mars, and beyond. Ph.D. in geochemistry from California Institute of Technology, 1994; University of California Presidential Postdoc, Rubey Faculty Fellow at University of California, Los Angeles, 1994–1998; Dee and John Whiteman Dean's Distinguished Professor and director of the Center for Meteorite Studies, Arizona State University, 1998–2005, NASA Goddard Space Flight Center, 2005 to present. Member of AGU, Meteoritical Society. Authored 38 peer-reviewed publications, three in AGU journals. Received NASA Distinguished Public Service Medal (2004), Meteoritical Society's Nier Prize (1996), and asteroid named 4922 Leshin (2001). Served on the President's Commission on Implementation of U.S. Space Exploration Policy, Solar System Exploration Subcommittee, Jet Propulsion Laboratory Director's Council, the Curation and Analysis Planning Team for Extraterrestrial Materials (CAPTEM), and several mission science definition teams. AGU service as Planetary Sciences secretary (1998–2000), Fall Meeting chair for Planetary Science, 1998, 1999.