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UC Berkeley physicist John Reynolds, known for his work on isotope dating of rocks and meteorites, has died at 77
09 Nov 2000

By Robert Sanders, Media Relations

A print quality photo of Reynolds is available for download


John Reynolds

John H. Reynolds, professor emeritus of physics. Saxon Donnelly photo.

Berkeley - John H. Reynolds, professor emeritus of physics at the University of California, Berkeley, and a pioneer in the isotopic dating of rocks and meteorites, died at his home in Berkeley on Saturday, Nov. 4, at the age of 77. He was recovering from pneumonia when he suffered a pulmonary embolism.

Reynolds had been a member of the College of Letters & Science faculty at UC Berkeley since 1950, served as chair of the physics department from 1984 to 1986, and retired in 1993.

He is best remembered for his research on isotopic and elemental measurements of the noble gases - helium, argon and xenon - which made it possible to determine the age of both terrestrial rocks and meteorites. He discovered that an excess of xenon gas trapped in stony meteorites was a decay product of an extinct isotope of iodine. Using sensitive mass spectrometry to measure isotopes of iodine and xenon, he was able to estimate the time between creation of the isotopes inside a star and when the meteorites - and the planetary bodies they were derived from - formed.

These accurate measurements provided a reliable chronology for the early solar system. Among the surprises was that the Earth had formed a relatively short time - between 120 and 290 million years - after its gas and dust were produced in a nearby supernova explosion.

His research group discovered and developed another technique, argon-argon dating, for determining the age of young rocks. The technique had much to do with the proof of the theory of continental drift and sea floor spreading. It also helped scientists interpret the origin, history, age and composition of the moon from lunar soil samples.

"Argon-argon dating, the most important and most versatile dating method today, was discovered and pioneered in 1966 by two young scientists (Grenville Turner and Craig Merrihue) working in his laboratory," said Paul Renne, former director of the Berkeley Geochronology Center and an adjunct professor of earth and planetary science at UC Berkeley. "John was a real luminary in the field of geochronology, and his death is a tremendous loss."

With the assistance of National Science Foundation and Fulbright-Hayes Research Awards, Reynolds established noble gas isotope laboratories at the Universidade de Coimbra, Portugal, the University of Western Australia, and the Universidade de Sao Paulo, Brazil. The latter became a center for isotopic dating used by geoscientists throughout Brazil and much of South America.

Following retirement, Reynolds remained active at the Lawrence Berkeley National Laboratory's Center for Isotopic Geochemistry and was a valuable resource to astrophysics graduate students. He was also an avid sailor.

Born April 3, 1923, in Cambridge, Mass., he attended Harvard College as an undergraduate, and received a PhD in physics from the University of Chicago in 1950. He served with the U.S. Navy in the South Pacific during World War II.

Reynolds received numerous distinctions in his career, including the J. Lawrence Smith Medal of the National Academy of Sciences; the NASA Exceptional Scientific Achievement Medal; the Leonard Medal from the Meteoritical Society; Doctor, Honoris Causa from University of Coimbra, Portugal; the National Science Foundation Cooperative Research Award and the Berkeley Citation.

He was a Fellow of the California Academy of Sciences. He was also elected to the National Academy of Sciences in 1968 and the American Academy of Arts and Sciences in 1986.

He is survived by his wife, Ann Reynolds, and children Petra of San Jose, Karen Stein, Brian and Horace of Berkeley, and Amy of San Francisco. A memorial service will be held at UC Berkeley's Faculty Club on Nov. 16 at 4 p.m. Contributions may be sent to the Department of Physics, LeConte Hall, University of California, Berkeley, CA 94720-7300 and to The Visiting Nurses Association.


A print quality photo of Reynolds is available for download