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Published January 1, 2010 | public
Journal Article

Nitrogen isotopes in the recent solar wind from the analysis of Genesis targets: Evidence for large scale isotope heterogeneity in the early solar system

Abstract

We have analyzed nitrogen, neon and argon abundances and isotopic ratios in target material exposed in space for 27 months to solar wind (SW) irradiation during the Genesis mission. SW ions were extracted by sequential UV (193 nm) laser ablation of gold-plated material, purified separately in a dedicated line, and analyzed by gas source static mass spectrometry. We analyzed gold-covered stainless steel pieces from the Concentrator, a device that concentrated SW ions by a factor of up to 50. Despite extensive terrestrial N contamination, we could identify a non-terrestrial, ^(15)N-depleted nitrogen end-member that points to a 40% depletion of ^(15)N in solar-wind N relative to inner planets and meteorites, and define a composition for the present-day Sun (^(15)N/^(14)N = [2.26 ± 0.67] × 10^(−3), 2σ), which is indistinguishable from that of Jupiter's atmosphere. These results indicate that the isotopic composition of nitrogen in the outer convective zone of the Sun has not changed through time, and is representative of the protosolar nebula. Large ^(15)N enrichments due to e.g., irradiation, low temperature isotopic exchange, or contributions from ^(15)N-rich presolar components, are therefore required to account for inner planet values.

Additional Information

© 2009 Elsevier. Received 17 June 2009; accepted 11 September 2009. Associate editor: Gregory F. Herzog. Available online 15 September 2009. We are grateful to J.H. Allton, A.J.G. Jurewicz and the Genesis Curation team at Johnson Space Center, NASA, Houston (USA) for excellent sample selection and preparation. We are also thankful to the Concentrator instrument team at Los Alamos National Laboratory for providing blanks and information on the gold cross. F. Gaboriau, LCPME, Vandoeuvre le`s Nancy (France) helped for atomic force microscopy analysis of test samples. S. Sestak and I.A. Franchi did ozone cleaning of the samples at the Open University, Milton Keynes (UK). J.I. Matsuda kindly provided the 3He/4He gas sample used in this study. We thank the members of the Genesis Science Team for constructive interactions during the last 6 years. The manuscript benefitted from stimulating reviews by A. Verchovsky, F. Robert and an anonymous reviewer, and from careful editing by G. Herzog. This study was funded by Centre National d'Etudes Spatiales, Centre National de la Recherche Scientifique — Institut National des Sciences de l'Univers, Région Lorraine, The Swiss National Science Foundation, and NASA through the Genesis mission.

Additional details

Created:
August 22, 2023
Modified:
October 19, 2023