Oxygen has three stable isotopes: oxygen-16, oxygen-17, and oxygen-18. In most studies on terrestrial samples, only the 18O/16O ratio is usually measured and discussed, where the mass-dependent fractionation law, expressed by δ17O ≈ 0.52 × δ18O, can be safely assumed (see Delta, Isotopic, for the δ notation). The δ17O values among extraterrestrial samples significantly deviate from the above shown relationship. This deviation bears prime importance in cosmochemistry and, naturally, in astrobiology.
KeywordsIsotope anomaly Fractionation mass independent Organic matter Photochemistry Self-shielding Solar composition Water
References and Further Reading
- Clayton RN (2005) Oxygen isotopes in meteorites. In: Davis AM (ed) Meteorites, comets and planets. Treatise on geochemistry, vol 1. Elsevier-Pergamon, Oxford, pp 129–142Google Scholar
- Ireland Isotopic enhancements of 17O and 18O from solar wind particles in the lunar regolith. Nature 440:776–778Google Scholar