Clair C. Patterson (1922-1995), discoverer of the age of the Earth.

geochemistry. In his famous paper entitled “Age of meteorites and the Earth” (Geochimica et Cosmochimica Acta, 1956, vol. 10, pp. 230–237), he provided the first reliable ages of the Earth and meteorites: about 4,550 million years. He reached this conclusion by utilizing elegant microchemical and precise mass spectrometric techniques for the analysis of the isotopic compositions and concentrations of lead in terrestrial materials and meteorites. This age of 4.55 billion years, observed in different materials of the solar system and confirmed subsequently by others using other techniques and isotopic systems, has been a benchmark for researches by geochemists, geologists, planetary scientists, astronomers and cosmologists. It ranks among the greatest achievements in science, with important implications not only for geochemistry and planetary science, but also clearly for astronomy, cosmology, biology and, even religion. He also established the fundamental basis for modeling the isotopic evolution of terrestrial lead, through thoughtful selection and analysis of critical rocks, sediments and waters of the planet. This created a powerful tool for identifying, tracing and evaluating the nature of the major geochemical reservoirs in the crust, mantle, and oceans. As another proof that good basic science is the engine of progress, he also provided the first and still most rigorous analysis of both the natural background and the anthropogenic buildup of lead in the environment. He did this by further extending analytical capabilities for cleanly extracting and analyzing nanogram quantities of lead, and by the design of clever, exhaustive sampling experiments in remote regions of the Earth, in various sea water environments, and in ancient archeological material. We owe to those experiments most of our present understanding of the natural lead levels and distributions, and of the magnitude and origins of anthropogenic lead pollution. His work established that the body burdens of lead in contemporary humans were elevated 1000 fold above those in prehistoric people. Such levels of lead have been shown to be within 3 to 6 fold of poisoning and that significant dysfunctions (some perhaps unrecognized) may result from even present levels. He investigated the concentrations of lead relative to other trace toxic and benign metals in natural food chains. This work yielded important insights into the mechanisms of biopurification of toxic elements in various natural biological processes. Patterson’s work has had a profound effect on all technological utilization of lead (and other metals) and on 231