Constraints on Neon and Argon Isotopic Fractionation in Solar Wind

Abstract

To evaluate the isotopic composition of the solar nebula from which the planets formed, the relation between isotopes measured in the solar wind and on the Sun's surface needs to be known. The Genesis Discovery mission returned independent samples of three types of solar wind produced by different solar processes that provide a check on possible isotopic variations, or fractionation, between the solar-wind and solar-surface material. At a high level of precision, we observed no significant inter-regime differences in ^(20)Ne/^(22)Ne or ^(36)Ar/^(38)Ar values. For ^(20)Ne/^(22)Ne, the difference between low- and high-speed wind components is 0.24 ± 0.37%; for ^(36)Ar/^(38)Ar, it is 0.11 ± 0.26%. Our measured ^(36)Ar/^(38)Ar ratio in the solar wind of 5.501 ± 0.005 is 3.42 ± 0.09% higher than that of the terrestrial atmosphere, which may reflect atmospheric losses early in Earth's history.

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