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James R. Arnold: from the Manhattan Project to the Moon and Beyond

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James R. Arnold: from the Manhattan Project to the Moon and Beyond RETROSPECTIVE James R. Arnold: From the Manhattan Project to the moon and beyond Mark H. Thiemens1 Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093-0356 n January 6, 2012, the field of Perhaps one of the most important cosmochemistry (more specifi- phases of Jim’s career was his work on Ocally, meteoritics and lunar lunar samples and the moon in general. and planetary sciences) lost one The paper Jim most frequently mentioned of its founding scientists. Jim Arnold’s was his early measurements of the first scientific endeavors ranged widely, ranging returned moon rocks (5). The article, from work on the Manhattan Project to referred to forever as SHRELLDALFF, the origin and use of cosmogenic nuclides an acronym composed of the first letters of in meteorites and lunar samples and to the authors of the paper, examined ra- sampling cosmic dust with balloons. dionuclide production in rock 10017 Jim was born in Metuchen, N.J., on May and in lunar soil. This work began his 5, 1923. He often credited his imagination major scientific efforts on the moon and and curiosity to his early childhood in exploration of its history. He also de- his family’s home. His father, a lawyer and veloped lunar orbital gamma-ray instru- archaeologist, had a large and easily ac- Jim Arnold. ments aboard the Ranger space crafts that cessible library—a major boon for Jim, were widely used to examine the elemental who found inspiration from such writers as composition of the moon. Jules Verne and H. G. Wells. In 1955, Jim returned to Princeton Jim was a member of a group known as At 16 years of age, Jim entered Princeton University as an assistant professor, “the Four Horsemen,” which included where he opened up a number of new University, where he pursued his love of 14 Wasserburg, Robert Walker, and Paul chemistry and earned his three degrees. investigations and expanded the use of C Gast. The group led the development Jim was engaged in his doctoral work to broader topics. It was during his time of the national lunar sample research at Princeton University that he began when he was brought into the Manhattan 7 program, formulated priorities for the Project. Although one would normally his measurements of radioactivity of Be scientific study of moon rocks and soil produced by cosmic rays (3) and, sub- comment here on the subject of his dis- 10 returned by the Apollo missions, and sertation research, Jim’s thesis research sequently, Be. His work on cosmogeni- facilitated the remarkably rich advances in has been classified and one can only cally produced radionuclides marked fundamental planetary sciences over the speculate. the beginning of his research in extrater- ensuing decades. After the war, Jim went to the University restrial materials, for which he was most On many occasions, Jim recounted his of Chicago for a year, spent a year at well-known. experience of returning the first lunar Harvard University, and then returned to At Princeton University, Jim began samples to the University of California at Chicago, where a rather incredible as- collaborations with Masatake (Masa) San Diego and the drama of making the semblage of the world’s premier scientists Honda that were to last the rest of his life. first measurements, which were embargoed had gathered. Harold Urey, Willard Libby, With Honda and student Julian Shedlov- until the first Lunar and Planetary Science 53 and Enrico Fermi were there along with sky, Jim isolated Mn from iron and other Conference at the National Aeronautics their students and postdoctoral fellows, meteorites. Later, Jim, Honda, and and Space Administration (NASA) including Jerry Wasserburg, Harmon Devendra Lal isolated cosmic ray-pro- Manned Space Flight Center in Houston. 36 26 10 Craig, Cesare Emiliani, and Sam Epstein. duced Cl, Al, and Be, a feat Jim later A former graduate student, Candace Kohl, Jim worked on early applications of 14C recalled was made nearly insurmountably recalls the excitement of working with with Willard Libby, including the devel- difficult by the formidable nature of something from the moon. “You would opment of the scintillation counter and the chemical extraction and the need to have to collect the moon dust off your a worldwide assay of natural radiocarbon develop new counting techniques (4). fingers,” she said. (1, 2). Jim’s wide-ranging interest in While visiting La Jolla in the summer of Jim was also taken with Urey’s idea how scientific measurements of naturally 1957, Roger Revelle approached Jim that craters on the moon with perpet- produced (cosmic ray) radioactivity may Arnold with an offer to help build the San ually cold surfaces could lead to the pres- be used to delve into understanding nature Diego campus of the University of Cal- ence and maintenance of water on the in the very broadest way began with his ifornia. His wife, Louise, remembers that moon. He proposed a special mission to work with Libby at Chicago. It was also in Jim thought about this for a couple of search for water at the lunar poles. This Chicago, during his time as an assistant weeks until he read in a news story that resulted in NASA’s LUnar CRater Ob- professor at the University of Chicago, his former colleague at Chicago, Urey, was servation and Sensing Satellite (LCROSS) that he met his wife Louise. They married accepting a position at the University of mission, which blasted a rocket into a cra- in October of 1952. California at San Diego, and Jim joined ter near the moon’s South Pole, revealing Jim’s work on radioactivity and its uses up in short order. The Arnolds moved to the presence of water, much to Jim’s de- also addressed a spectrum of problems La Jolla in 1958. light. He was obsessed with the idea of in fundamental physics and radiochemis- Honda and Lal joined Jim in La Jolla try, including determination of the energy as well, where their development of levels in 176Lu and 176Hf, decay schemes in wide-ranging new applications in the Author contributions: M.H.T. wrote the retrospective. lutetium, and development of ways to use of naturally produced cosmogenic The author declares no conflict of interest. detect them. radionuclides flourished over decades. 1Email: [email protected]. www.pnas.org/cgi/doi/10.1073/pnas.1201983109 PNAS Early Edition | 1of2 Downloaded by guest on October 2, 2021 colonizing the moon, for which the pres- Governor Jerry Brown, pulling him out of mentored generations of students who ence of water would be vital. Jerry a meeting and asking him if he would be often recount that he was the best pro- Wasserburg has noted “he was a lover interested in forming a California Space fessor they had. of the Pogo comic strip and of Buck Institute, that started the process. Jim left one more lasting impression Rogers,” which, along with a love of the Jim was also the University of California that warrants commentary. He had science fiction of Jules Verne, fueled at San Diego’s first department chair a seemingly endless supply of bright Jim’s fascination with manned exploration (chemistry). Jim’s imprint on the founding Hawaiian shirts, specially modified by of space. of the University of California at San replacing the original pockets with fabric Jim’s broad interest in space led him Diego was everywhere. In addition to of a completely different bright and to found the California Space Institute, serving as the first chair of the chemistry complex pattern, although totally non- a multicampus institution created by the department, he was a leader in the re- Hawaiian, lending them a remarkable State of California and dedicated to cruitment of faculty and the development character. studies of how to develop the future of of the university’s curricula. One of the He is missed deeply and is survived by his mankind in space. It was a call to Jim from most popular lecturers on campus, Jim wife Louise and their three sons. 1. Libby WF, Anderson EC, Arnold JR (1949) Age De- 3. Arnold JR (1956) Beryllium-10 Produced by Cosmic Rays. 5. Shedlovsky JP, et al. (1970) Pattern of bombardment- termination by Radiocarbon Content: World-Wide As- Science 124:584–585. produced radionuclides in rock 10017 and in lunar soil. say of Natural Radiocarbon. Science 109:227–228. 4. Arnold JR, Honda M, Lal D (1961) Record of cosmic Science 167:574–576. 2. Arnold JR, Libby WF (1949) Radiocarbon dates. Science ray intensity in the meteorites. J Geophys Res 66: 113:111–121. 3519–3531. 2of2 | www.pnas.org/cgi/doi/10.1073/pnas.1201983109 Thiemens Downloaded by guest on October 2, 2021.
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