Helium and Neon Abundances and Compositions in Cometary Matter
Bernard Marty,1
Russell L. Palma,2,3
Robert O. Pepin,3*
Laurent Zimmermann,1
Dennis J. Schlutter,3
Peter G. Burnard,1
Andrew J. Westphal,4
Christopher J. Snead,4
Sa
a Bajt,5
Richard H. Becker,3
Jacob E. Simones2
Materials trapped and preserved in comets date from the earliest history of the solar system. Particles captured by the Stardust spacecraft from comet 81P/Wild 2 are indisputable cometary matter available for laboratory study. Here we report measurements of noble gases in Stardust material. Neon isotope ratios are within the range observed in "phase Q," a ubiquitous, primitive organic carrier of noble gases in meteorites. Helium displays 3He/4He ratios twice those in phase Q and in Jupiter's atmosphere. Abundances per gram are surprisingly large, suggesting implantation by ion irradiation. The gases are probably carried in high-temperature igneous grains similar to particles found in other Stardust studies. Collectively, the evidence points to gas acquisition in a hot, high ion-flux nebular environment close to the young Sun.
1 Centre de Recherches Pétrographiques et Géochimiques, Nancy Université, BP 20, 54501 Vandoeuvre-lès-Nancy Cedex, France.
2 Department of Physics and Astronomy, Minnesota State University, Mankato, MN 56001, USA.
3 School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA.
4 Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA.
5 Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
* To whom correspondence should be addressed. E-mail: pepin001{at}umn.edu
