In DepthGeochemistry

Rare isotopes offer clues to the chemistry of the planet

Science  29 Jan 2016:
Vol. 351, Issue 6272, pp. 431-432
DOI: 10.1126/science.351.6272.431

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For decades, geochemists had to be content to measure one isotope at a time. Now, however, formidable new lab instruments are enabling them to detect some of the rarest isotopic variants in nature, molecules containing two or more rare isotopes. In carbon dioxide, for example, these multiple isotopes are found more often than expected—a phenomenon called clumping—which leads to a powerful tool for measuring the temperatures at which the molecules formed, now and in the ancient past. Work on methane is close to yielding a tool for distinguishing gas made by microbes from "abiotic" methane made from mineral reactions deep in Earth. And work on nitrogen could reveal which of two pathways is most important in removing biologically fixed nitrogen from oceans. Some geochemists even hope that, as techniques improve, there could be applications in diagnosing diseases and measuring the efficacy of drugs on individuals.