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Solar system materials are heterogeneous in their oxygen isotopic compositions. Oxygen is the third abundant element in the solar system, and the most in rocky objects such as earth-like planets, moon and asteroids. Oxygen has three stable isotopes with mass number 16, 17 and 18. Oxygen-isotopic com...

Solar system materials are heterogeneous in their oxygen isotopic compositions. Oxygen is the third abundant element in the solar system, and the most in rocky objects such as earth-like planets, moon and asteroids. Oxygen has three stable isotopes with mass number 16, 17 and 18. Oxygen-isotopic compositions of minerals and rocks can be measured by fluorination methods using BrF₅ or F₂, or by secondary ion mass spectrometry. The former has better analytical precision but requires larger sample sizes, while the later is good in spacial resolution but has larger analytical uncertainty. Oxygen-isotopic compositions of solar-system materials mainly obtained from meteorites have about 7% variations in both ¹⁷O/¹⁶O and ¹⁸O/¹⁶O ratios and not fall along the trend predicted by mass-dependent fractionation from a homogeneous reservoir. Such heterogeneity could not be produced by common physico-chemical processes that occurred during the formation of meteorites. It suggests, therefore, that the solar nebula was heterogeneous in terms of oxygen isotopes during the formation of meteoritic components. However, it conflicts with observation from isotopic homogeneity of most of other elements, which requires well-mixed solar nebula. In this paper, general characteristics of oxygen isotopes and analytical methods to measure them are briefly reviewed. Oxygen-isotopic compositions of solar system materials and possible explanations for the heterogeneity are then discussed.

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