James R. Arnold, founding chairman of UC San Diego’s chemistry department and first director of the California Space Institute whose contributions to science spanned the study of cosmic rays to the future of manned space flight, died Friday, Jan. 6. He was 88. A longtime consultant to NASA, Arnold helped to set science priorities for missions, including the Apollo flights to the moon. He first served on a NASA committee in 1959, just three months after the space agency was established.
“I have known Jim Arnold for over 60 years. He was a dedicated and imaginative scientist,” said Gerald Wasserburg, emeritus professor of geology and geophysics at Caltech. “He was a lover of the Pogo comic strip and of Buck Rogers who ignited his passion for shooting people into space and colonizing it.”
Arnold and Wasserburg, along with Paul Gast and Bob Walker, whom their colleagues called the “Four Horsemen,” helped to establish the national lunar sample research program and fostered its remarkable contributions to planetary science over the decades since Apollo 11.
Arnold was in Houston for the arrival of the first lunar samples and carried some of them back to his laboratory at UC San Diego where his group studied them, sometimes while watching astronauts on subsequent missions on television as they collected the rocks Arnold’s group would study next.
“The excitement of it - to hold something that’s from the moon,” said Candace Kohl, a graduate student who pulverized the rock surfaces with a dental drill as part of her study. “You would have to collect the moon dust off your fingers.”
Over more than two decades, Arnold traced the history of moon rocks’ bombardment by cosmic rays and extended our record of the energy output of the Sun by millions of years.
In 1970, NASA recognized Arnold’s work with an “Exceptional Scientific Achievement” medal. Arnold also received the Department of Energy’s E.O. Lawrence Award in chemistry and metallurgy. Cosmic rays leave traces in meteorites as well, a record of “how long they have been a rock in space,” Arnold told a reporter for the Los Angeles Times. For his work on the ages and origins of meteorites, Arnold received the Meteoritical Society’s Leonard Medal in 1976.
Arnold’s scientific work began with the study of the nuclei of chemical elements. He earned three degrees in chemistry from Princeton University, culminating in a Ph.D. awarded in 1946 for his work on the Manhattan Project.
He had deep concerns over the threat of nuclear fallout and was a thoughtful contributor to the Bulletin of Atomic Scientists from its foundation.
After completing his degrees, Arnold joined Willard Libby’s group at the University of Chicago’s Institute for Nuclear Studies, where he helped to develop a method still used by archaeologists and paleontologists for dating once-living things using radioactive carbon.
When he returned to Princeton as a faculty member in 1955, Arnold expanded that research to look at the effects of cosmic rays on meteorites using isotopes that decay far more slowly, over millions of years, recording the age of much older rocks.