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, January 6 2012. 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. 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. 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. Roger Revelle recruited Arnold to be among the first faculty to join the fledgling UC San Diego campus in 1958. In 1960 Arnold became the founding chairman of the chemistry department and was a popular teacher in those early days of the campus. Arnold was a member of the National Academy of Sciences and the American Academy of Arts and Sciences. Arnold held the Harold Urey Chair in Chemistry, named in honor of the father of planetary science, from 1983 until he retired in 1993. Arnold is survived by his wife Louise Arnold, whom he met at a World Federalist conference in 1950 and married in 1952, and their sons Bob, Ted and Ken, and their families.