Isotope in meteorites

Many scientists thought that Earth must have formed as long as 3.3 billion years ago, but their evidence was confusing and inconsistent. They knew that some of the lead on Earth was primordial, i.e., it dated from the time the planet formed. But they also understood that some lead had formed later from the radioactive decay of uranium and thorium. Different isotopes of uranium decay at different rates into two distinctive forms or isotopes of lead lead-206 and lead-207. In addition, radioactive thorium decays into lead-208. Thus, far from being static, the isotopic composition of lead on Earth was dynamic and constantly changing, and the various proportions of lead isotopes over hundreds of millions of years in different regions of the planet were keys to dating Earth s past. A comparison of the ratio of various lead isotopes in Earth s crust today with the ratio of lead isotopes in meteorites formed at the same time as the solar system would establish Earth s age. Early twentieth century physicists had worked out the equation for the planet s age, but they could not solve it because they did not know the isotopic composition of Earth s primordial lead. Once that number was measured, it could be inserted into the equation and blip, as Patterson put it, out would come the age of the Earth. ... 

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Clayton, R. N. (2004) Oxygen isotopes in meteorites. In Treatise on Geochemistry, Volume 1 Meteorites, Comets, and Planets, ed. Davis, A. M. Oxford Elsevier, pp. 129-142. 

People especially interested in the light element stable isotopes in meteorites should see the recent review article by Pillinger 64). 

Clayton R. N. (1963) Carbon isotopes in meteoritic carbonates. Science 140, 192-193. 

Pillinger C. T. (1984) Light element stable isotopes in meteorites from grams to picograms. Geochim. Cosmochim. Acta 48, 2739-2766. 

Here, we discuss the evidence for the prior existence of now-extinct isotopes in meteoritic... 

Farquhar J., Savarino J., Jackson T. L., and Thiemens M. H. (2000) Evidence of atmospheric sulphur in the martian regolith from sulphur isotopes in meteorites. Nature 404, 50-52. 

Studies of lead isotopes in meteorites have been very fundamental to all of earth science the first reliable age of meteorites was a lead isochron age (Patterson, 1955), and the accepted age of the earth stems from meteorite studies (Patterson, 1953 Patterson et al., 1955). 

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