Carnegie Institution planetary-formation theorist and 1997 National Medal of Science recipient George Wetherill died from heart failure on July 19, 2006, at his Washington, D.C. home. Wetherill revolutionized our understanding of how our planets and solar system formed through his theoretical models.

Born in Philadelphia on August 12, 1925, Wetherill served in the US Navy during World War II, teaching radar at the Naval Research Laboratory in the District. He graduated from the University of Chicago in 1953 after a succession of degrees, Ph.B., S.B., S.M., and Ph.D. After receiving his doctorate, he joined Carnegie’s Department of Terrestrial Magnetism as a member of the scientific staff. Between 1960 and 1975 he was a professor and department chairman at the University of California, Los Angeles. He came back to Carnegie in 1975 as director of the department, a position he held until 1991. After he stepped down, he continued his research as director emeritus.

In the 1950s, Wetherill was among a group of scientists who developed geochemical methods involving natural radioactive decay to date the Earth's rocks. Later, his interests in age-dating techniques expanded to include extraterrestrial materials, including meteorites and rock samples from the moon. In the 1970s, he began theoretical explorations into the origins of meteorites and the terrestrial planets, developing a technique to calculate the orbital evolution and accumulation of swarms of small bodies as they coalesce into planets.

Wetherill’s computations have also revealed how important Jupiter may be in protecting the Earth and other inner planets from bombardment via its enormous gravitational field. He showed that the field provides a shield from orbiting asteroids and comets, scattering most of them out of the Solar System. The discoveries of planets orbiting other stars provided him with further theoretical challenges in his final years of research.

In 1997 George Wetherill received the highest scientific award in the nation—the National Medal of Science. He was elected to the American Academy of Arts and Sciences in 1971 and to the National Academy of Sciences in 1974. He received the 1981 F. C. Leonard Medal of the Meteoritical Society, the 1984 G. K. Gilbert Award of the Geological Society of America, the 1986 G. P. Kuiper Prize of the Division of Planetary Sciences of the American Astronomical Society, and the 1991 Harry H. Hess Medal of the American Geophysical Union. In 2003 Wetherill was awarded the Henry Norris Russell Lectureship, the highest honor bestowed by the American Astronomical Society.

Survivors include his wife, Mary Bailey, of the District, and his daughters, Rachel Wetherill, of Round Hill, Virginia, and Sarah Wetherill Okumura, of Morgan Hill, California. He was preceded in death by his son, George W. Wetherill III, in 1974, and by his first wife, Phyllis Steiss Wetherill, in 1995.