A Couple of Uncertain Age

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Science  19 Mar 1999:
Vol. 283, Issue 5409, pp. 1863-1864
DOI: 10.1126/science.283.5409.1863

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The earth and moon formed not long after our solar system formed 4.57 billion years ago, but the exact timing remains a subject of debate. Attempts to date our planet and its companion are based largely on isotopic measurements of lunar and terrestrial samples. Ratios of certain isotopes can provide information on when the material formed, but only if the physical and chemical changes that the material has gone through are known. Podosek concludes that to improve the dating, we need a better understanding of the physical and chemical processes that affect planetary isotope compositions.