Oral histories in meteoritics and planetary science: IV. James R. Arnold

— James Arnold, a nuclear chemist, reports in this interview, taped during the Meteoritical Society meeting in Chicago in 2000, that he became interested in meteorites when one of his graduate students chose to search for the cosmogenic isotope, 53 Mn, in an iron meteorite. This project led to analyses of what became the standard four cosmogenic isotopes ( 53 Mn, 36 C1, 26 A1, and 10 Be) in meteorites and to the first determinations of their terrestrial ages. These in turn paved the way for analyses of a broad set of short‐ and long‐lived isotopes in lunar samples returned by the Apollo astronauts, providing insight into lunar surface processes and the history of cosmic radiation. Arnold also mounted gamma‐ray spectrometers on the command modules of the Apollo 15 and 16 missions and obtained chemical maps of the surface materials in mare and highlands regions. In 1958 Arnold began his research and teaching at the University of California at San Diego where from 1983 to his retirement in 1993 he served as the Harold C. Urey Professor of Chemistry. In 1976, the Meteoritical Society honored James Arnold with its Leonard Medal.