Heber, Veronika S. and Wieler, Rainer and Baur, Heinrich and Olinger, Chad and Friedmann, Tom A. and Burnett, Donald S. (2009) Noble gas composition of the solar wind as collected by the Genesis mission. Geochimica et Cosmochimica Acta, 73 (24). pp. 7414-7432. ISSN 0016-7037 http://resolver.caltech.edu/CaltechAUTHORS:20100112-110441285
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We present the elemental and isotopic composition of noble gases in the bulk solar wind collected by the NASA Genesis sample return mission. He, Ne, and Ar were analyzed in diamond-like carbon on a silicon substrate (DOS) and ^(84),^(86)Kr and ^(129),^(132)Xe in silicon targets by UV laser ablation noble gas mass spectrometry. Solar wind noble gases are quantitatively retained in DOS and with exception of He also in Si as shown by a stepwise heating experiment on a flown DOS target and analyses on other bulk solar wind collector materials. Solar wind data presented here are absolutely calibrated and the error of the standard gas composition is included in stated uncertainties. The isotopic composition of the light noble gases in the bulk solar wind is as follows: ^3He/^4He: (4.64 ± 0.09) × 10^(−4), ^(20)Ne/^(22)Ne: 13.78 ± 0.03, ^(21)Ne/^(22)Ne: 0.0329 ± 0.0001, ^(36)Ar/^(38)Ar 5.47 ± 0.01. The elemental composition is:^4He/^(20)Ne: 656 ± 5, and ^(20)Ne/^(36)Ar 42.1 ± 0.3. Genesis provided the first Kr and Xe data on the contemporary bulk solar wind. The preliminary isotope and elemental composition is: ^(86)Kr/^(84)Kr: 0.302 ± 0.003, ^(129)Xe/^(132)Xe: 1.05 ± 0.02, ^(36)Ar/^(84)Kr 2390 ± 150, and ^(84)Kr/^(132)Xe 9.5 ± 1.0. The ^3He/^4He and the ^4He/^(20)Ne ratios in the Genesis DOS target are the highest solar wind values measured in exposed natural and artificial targets. The isotopic composition of the other noble gases and the Kr/Xe ratio obtained in this work agree with data from lunar samples containing “young” (~100 Ma) solar wind, indicating that solar wind composition has not changed within at least the last 100 Ma. Genesis could provide in many cases more precise data on solar wind composition than any previous experiment. Because of the controlled exposure conditions, Genesis data are also less prone to unrecognized systematic errors than, e.g., lunar sample analyses. The solar wind is the most authentic sample of the solar composition of noble gases, however, the derivation of solar noble gas abundances and isotopic composition using solar wind data requires a better understanding of fractionation processes acting upon solar wind formation.
|Additional Information:||© 2009 Elsevier Ltd. Received 11 June 2009; accepted in revised form 14 September 2009; available online 23 September 2009. We are thankful for the great support from Judith H. Allton and the entire Genesis curation team at Johnson Space Center, Houston USA, for sample selection and cleaning. We appreciate discussions with Rolf Kipfer and Ansgar Grimberg. We thank Nadia Vogel for discussion and correction of the paper. Detailed reviews by Jamie Gilmour, Roger Wiens and an anonymous reviewer are gratefully acknowledged. We acknowledge support by the Swiss National Science Foundation and the NASA Discovery Mission Office. V.S. Heber thanks Kevin McKeegan and NASA Cosmochemistry to have been able to complete this work.|
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|Deposited By:||Ruth Sustaita|
|Deposited On:||14 Jan 2010 21:43|
|Last Modified:||26 Dec 2012 11:41|
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