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Volumn 300, Issue 5616, 2003, Pages 105-108

Samples of stars beyond the solar system: Silicate grains in interplanetary dust

Author keywords

[No Author keywords available]

Indexed keywords

AMORPHOUS MATERIALS; ISOTOPES; OXYGEN; SILICATES; SPACE RESEARCH;

EID: 0242416950     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1080576     Document Type: Article
Times cited : (327)

References (45)
  • 6
    • 0242598024 scopus 로고    scopus 로고
    • note
    • These grains are identified as "circumstellar" or equivalently "stardust," because their O isotopic compositions establish their origins as stellar ejecta. These grains must also have traversed the interstellar medium before their incorporation into the nascent solar nebula, and could also be considered "interstellar dust."
  • 11
    • 0242513288 scopus 로고    scopus 로고
    • note
    • GEMS grains are a major component of cometary/anhydrous IDPs, occasionally exceeding 50 weight % of the IDP mass. They are typically 01 to 0.5 μm in size, have approximately chondritic elemental abundances (with the exception of C), and have optical properties consistent with those observed for interstellar amorphous silicates (13). GEMS have also been observed within isotopically anomalous (H and N) organic matter thought to be of presolar origin (12).
  • 13
    • 0033543633 scopus 로고    scopus 로고
    • J. P. Bradley et al., Science 285, 1716 (1999).
    • (1999) Science , vol.285 , pp. 1716
    • Bradley, J.P.1
  • 14
    • 0242429891 scopus 로고
    • thesis, University of Heidelberg, Germany
    • F. J. Stadermann, thesis, University of Heidelberg, Germany (1991).
    • (1991)
    • Stadermann, F.J.1
  • 15
    • 0242598023 scopus 로고
    • thesis, Washington University, St, Louis, MO
    • K. D. McKeegan, thesis, Washington University, St, Louis, MO (1987).
    • (1987)
    • McKeegan, K.D.1
  • 17
    • 0344681789 scopus 로고    scopus 로고
    • B. A. S. Gustafson, M. S. Hanner, Eds. (Astronomical Society of the Pacific, Provo, UT)
    • J. Bradley, T. Ireland, in Physics, Chemistry and Dynamics of Interplanetary Dust, B. A. S. Gustafson, M. S. Hanner, Eds. (Astronomical Society of the Pacific, Provo, UT, 1996), pp. 275-282.
    • (1996) Physics, Chemistry and Dynamics of Interplanetary Dust , pp. 275-282
    • Bradley, J.1    Ireland, T.2
  • 19
    • 0242429892 scopus 로고    scopus 로고
    • note
    • - peak was less than 1%o, with a mass-resolving power of at least 9000 (Cameca definition), or ∼6000 in the conventional definition. Image acquisition times ranged from 3 to 10 hours, consuming 30 to 100 nm of surface material. The magnetic field was controlled with a nuclear magnetic resonance probe, which kept peak positions stable to ΔM/M < 5 ppm. Thin sections were coated with 50 Å of Au or C to avoid sample charging.
  • 20
    • 0242681840 scopus 로고    scopus 로고
    • note
    • The IDP L2036 C4 was extracted from the ion probe mount by carving a section of the Au substrate measuring 200 x 200 μm by hand with a scalpel. The extracted section was glued to a flattened epoxy bullet with a cyanoacrylate adhesive. The Au was trimmed with a glass knife on an ultramicrotome, leaving a 30-μm plateau containing the IDP. The IDP was then embedded in resin, and after curing several days was sliced with a diamond knife into 50-nm sections. The sections were transferred to a 1-mm-aperture grid coated with Formvar. After TEM analysis, the entire mount (Formvar with seven sections) was transferred to a preformed Au plateau, where the sections were subsequently imaged in the NanoSIMS.
  • 21
    • 0242429888 scopus 로고    scopus 로고
    • note
    • The data were analyzed with custom software written in the Interactive Data Language. In most cases, a range of image layers (5 to 10) was selected, discarding the first low-intensity images and the final images, which for the TEM sections were often compromised by rapid erosion of the epoxy or carbon substrate. Candidate grains were manually defined and semiautomatically redefined in subsequent layers, with the particle positions and outlines being checked in each image layer.
  • 23
    • 0242513285 scopus 로고    scopus 로고
    • note
    • 18O = 498.7). The standard deviations of the isotopic compositions of these "standard subgrains" were taken into account in the determination of the final measurement uncertainty. Final isotopic ratios and uncertainties were determined according to standard procedures. Grains that have O isotopic compositions that deviate from solar compositions by at least 3σ are identified as stardust.
  • 27
    • 0242681839 scopus 로고    scopus 로고
    • note
    • We used a JEOL 2000FX TEM equipped with an Oxford instruments energy-dispersive x-ray (EDX) spectrometer to analyze ultramicrotome thin sections of the IDPs. The mineralogy and composition of grains >200 nm in diameter were determined with a combination of electron diffraction and quantitative EDX analysis and dark-field imaging.
  • 28
    • 0242513287 scopus 로고    scopus 로고
    • note
    • standard - 1) × 1000.
  • 29
    • 0242681838 scopus 로고    scopus 로고
    • note
    • 18O < 20%o), 49 have solar O isotopic ratios within 2σ, and one is a circumstellar grain. We achieved the highest precision isotopic measurements on ultramicrotome thin sections deposited onto Au substrates. This mounting technique offers very flat conducting samples. Images acquired from TEM grid sections were limited by the sputtering lifetime of the epoxy and were compromised by stretching and tearing of holes in the epoxy and C substrate during the measurements.
  • 31
    • 0003347213 scopus 로고    scopus 로고
    • Disks, and Regoliths, M. L. Sitko, A. L. Sprague, D. V. Lynch, Eds. (Astronomical Society of the Pacific, San Francisco, CA)
    • L. B. F. M. Waters et al., in Thermal Emission Spectroscopy and Analysis of Dust, Disks, and Regoliths, M. L. Sitko, A. L. Sprague, D. V. Lynch, Eds. (Astronomical Society of the Pacific, San Francisco, CA, 2000), pp. 3-14.
    • (2000) Thermal Emission Spectroscopy and Analysis of Dust , pp. 3-14
    • Waters, L.B.F.M.1
  • 37
    • 0242681836 scopus 로고    scopus 로고
    • note
    • Although the nanodiamonds are abundant in meteorites (up to 1000 ppm), it is possible that only a small fraction are presolar in origin, because the bulk C isotopic composition is solar and the anomalous Xe and N have low abundances.
  • 44
    • 0242429885 scopus 로고    scopus 로고
    • in preparation
    • É. Zinner et al., in preparation.
    • Zinner, É.1
  • 45
    • 0242598020 scopus 로고    scopus 로고
    • note
    • Supported by NASA grants NAGS-9801 and RTOP 344-31-40-07. This work was enabled by the revolutionary NanoSIMS ion microprobe, which was designed by G. Slodzian at the University of Orsay, Paris.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.