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ReportsIsotopic Compositions of Cometary Matter Returned by Stardust
Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single 17O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is 16O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.
1 Department of Earth and Space Sciences, University of California Los Angeles, Los Angeles, CA 90095–1567, USA.
2 Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, Bat 104, 91405 Orsay Campus, France. 3 Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. 4 Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. 5 Department of Astronomy, University of Washington, Seattle, WA 98195, USA. 6 Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015, USA. 7 Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720–7450, USA. 8 Centre de Recherches Petrographiques et Geochimiques, 15 rue Notre Dame des Pauvres, BP 20, 54501 Vandoeuvre lès Nancy, France. 9 McDonnell Center for the Space Sciences, Department of Physics, Washington University, St. Louis, MO 63130, USA. 10 School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK. 11 Museum National d'Histoire Naturelle, Laboratoire d'Etude de la Matiere Extraterrestre, 57 rue Cuvier, 75005 Paris, France. 12 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. 13 Max-Planck-Institute for Chemistry, Particle Chemistry Department, J.-J.-Becherweg 27, D-55128 Mainz, Germany. 14 Robert M. Walker Laboratory for Space Science, Astromaterials Research and Exploration Science Directorate NASA Johnson Space Center, Houston, TX 77058, USA. 15 Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA. 16 Impacts and Astromaterials Research Centre, Department of Mineralogy, Natural History Museum, Cromwell Road, South Kensington, London SW7 5BD, UK. 17 Sciences and Exploration Directorate, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. 18 Jacobs Sverdrup, Houston, TX 77058, USA. 19 Department of Physics and Astronomy, Minnesota State University, 141 Trafton Science Center N, Mankato, MN 56001, USA. 20 School of Physics and Astronomy, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455, USA. 21 Science Division, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA. 22 Code 6360, Naval Research Laboratory, Washington, DC 20375, USA. * To whom correspondence should be addressed. E-mail: mckeegan{at}ess.ucla.edu
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