April 3, 1923–November 4, 2000


JOHN REYNOLDS, A MAN of many parts but foremost a geophysicist, died of complications from pneumonia in Berkeley on November 4, 2000. The modern sciences of geochronology and nuclear cosmochronology grew in large part out of the work of Reynolds and his students. He was the first to detect isotopic anomalies, the study of which culminated in over-whelming evidence for preservation in the meteorites of micron-size grains of stellar origin. In 1960 he detected the xenon isotope of mass 129 trapped in meteorites, and from that discovery inferred that the extinct radioactive isotope iodine-129 (half-life 16 million years and probably generated in a presolar supernova) was present when the meteorites formed. This indicated that the meteorites appeared in the early history of the solar system. In later studies he and collaborators showed that other short-lived species were present in the cloud of gas that turned into our solar system 4.6 billion years ago. For decades he kept his laboratory in the forefront of the field of cosmochemistry. He will be remembered as the “father” of extinct radioactivities.

John was born in Cambridge, Massachusetts, on April 4, 1923. His father, Horace Mason Reynolds, was educated at Harvard, taught English in various colleges in the Boston area and at Brown University, and wrote for newspapers

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