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Stardust in STARDUST - the C, N, and O Isotopic Compositions of Wild 2 Cometary Matter in Al Foil ImpactsIn January 2006, the Stardust mission successfully returned dust samples from the tail of comet 81P/Wild 2 in two principal collection media, low density silica aerogel and Al foil. While hypervelocity impacts at the Stardust encounter velocity of 6.1 kilometers per second into Al foils are generally highly disruptive for natural, silicate-dominated impactors, previous studies have shown that many craters retain sufficient residue to allow a determination of the elemental and isotopic compositions of the original projectile. We have used two NanoSIMS ion microprobes to perform C, N, and O isotope imaging measurements on four large (59-295 micrometer diameter) and on 47 small (0.32-1.9 micrometer diameter) Al foil impact craters as part of the Stardust Preliminary Examination. Most analyzed residues in and around these craters are isotopically normal (solar) in their C, N, and O isotopic compositions. However, the debris in one large crater shows an average N-15 enrichment of approx. 450%o, which is similar to the bulk composition of some isotopically primitive interplanetary dust particles and to components of some primitive meteorites. A 250 nm grain in another large crater has an O-17 enrichment with approx. 2.65 times the solar O-17/O-16 ratio. Such an O isotopic composition is typical for circumstellar oxide or silicate grains from red giant or asymptotic giant branch stars. The discovery of this circumstellar grain clearly establishes that there is authentic stardust in the cometary samples returned by the Stardust mission. However, the low apparent abundance of circumstellar grains in Wild 2 samples and the preponderance of isotopically normal material indicates that the cometary matter is a diverse assemblage of presolar and solar system materials.
Document ID
20070031609
Acquisition Source
Johnson Space Center
Document Type
Reprint (Version printed in journal)
Authors
Stadermann, Frank J. (Washington Univ. Saint Louis, MO, United States)
Hoppe, Peter (Max-Planck-Inst. fuer Chemie Mainz, Germany)
Floss, Christine (Washington Univ. Saint Louis, MO, United States)
Heck, Philipp R. (Max-Planck-Inst. fuer Chemie Mainz, Germany)
Hoerz, Friedrich (NASA Johnson Space Center Houston, TX, United States)
Huth, Joachim (Max-Planck-Inst. fuer Chemie Mainz, Germany)
Kearsley, Anton T. (Museum of Natural History London, United Kingdom)
Leitner, Jan (Westfaelische Wilhelms Univ. Muenster, Germany)
Marhas, Kuljeet K. (Washington Univ. Saint Louis, MO, United States)
McKeegan, Kevin D. (California Univ. Los Angeles, CA, United States)
Sstephan, Thomas (Westfaelische Wilhelms Univ. Muenster, Germany)
Date Acquired
August 23, 2013
Publication Date
January 1, 2007
Subject Category
Lunar And Planetary Science And Exploration
Funding Number(s)
CONTRACT_GRANT: STE 576/17-1
CONTRACT_GRANT: NNG05GJ26G
Distribution Limits
Public
Copyright
Public Use Permitted.

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