Heavy noble gases in solar wind delivered by Genesis mission

Abstract

One of the major goals of the Genesis Mission was to refine our knowledge of the isotopic composition of the heavy noble gases in solar wind and, by inference, the Sun, which represents the initial composition of the solar system. This has now been achieved with permil precision: 36Ar/38Ar=5.5005±0.0040, 86Kr/84Kr=.3012±.0004, 83Kr/84Kr=.2034±.0002, 82Kr/84Kr=.2054 ± .0002, 80Kr/84Kr = .0412±.0002, 78Kr/84Kr=.00642±.00005, 136Xe/132Xe=.3001±.0006, 134Xe/132Xe=.3691±.0007, 131Xe/132Xe=.8256±.0012, 130Xe/132Xe=.1650±.0004, 129Xe/132Xe=1.0405±.0010, 128Xe/132Xe=.0842±.0003, 126Xe/132Xe=.00416±.00009, and 124Xe/132Xe=.00491±.00007 (error-weighted averages of all published data). The Kr and Xe ratios measured in the Genesis solar wind collectors generally agree with the less precise values obtained from lunar soils and breccias, which have accumulated solar wind over hundreds of millions of years, suggesting little if any temporal variability of the isotopic composition of solar wind krypton and xenon. The higher precision for the initial composition of the heavy noble gases in the solar system allows (1) to confirm that, exept 136Xe and 134Xe, the mathematically derived U–Xe is equivalent to Solar Wind Xe and (2) to provide an opportunity for better understanding the relationship between the starting composition and Xe-Q (and Q-Kr), the dominant current “planetary” component, and its host, the mysterious phase-Q.