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In situ identification of a CAI candidate in 81P/Wild 2 cometary dust by confocal high resolution synchrotron X-ray fluorescence

Sylvia Schmitz, Frank Brenker, Tom Schoonjans UGent, Bart Vekemans UGent, Geert Silversmit UGent, Laszlo Vincze UGent, Manfred Burghammer and Christian Riekel (2009) Geochimica et Cosmochimica Acta. 17(18). p.5483-5492
abstract
We detected additional CAI-like material in STARDUST mission samples of comet 81P/Wild 2. Two highly refractory cometary dust fragments were identified in the impact track 110 [C2012, 0, 110, 0, 0] by applying high resolution synchrotron induced confocal and conventional XRF analysis (HR SR-XRF). The use of a polycapillary lens in front of the detector for confocal spectroscopy dramatically improves the fidelity of particle measurements by removing contribution from the surrounding aerogel. The high spatial resolution (300 x 300 nm2; 300 x 1000 nm2) obtained allowed the detailed non-destructive in situ (trapped in aerogel) study of impacted grains at the sub-lm level. For the two largest particles of the track, the terminal particle and a second particle along the impact track, Ca concentration is up to 30 times higher than CI and Ti is enriched by a factor of 2 compared to CI. High resolution (HR) SR-XRF mapping also reveals that the highest concentrations of Ca, Ti, Fe (and Ni) measured within each grain belongs to different areas of the respective maps which indicate that the particles are composed of several chemically diverse mineral phases. This is in agreement with the finding of a complex phase assemblage of highly refractory minerals in the first ever detected Stardust mission CAI grain ‘‘Inti” of Track 25. Principle component analysis (PCA) is a powerful tool for extracting the dominant mineral components and was applied to the two grains indicating that regions in the terminal particle and the second particle are consistent with anorthite or grossite and gehlenite, monticellite or Dmitryivanovite (CaAl2O4), respectively. Our new findings demonstrate that the HR SR-XRF with confocal geometry and PCA analysis is capable of identifying CAI-like fragments without the need to extract particles from the aerogel matrix which is a time-consuming, complex and destructive process. Furthermore, the detection of new CAI-like fragments in the coma dust of comet 81P/Wild 2 strengthens the observation that strong mixing effects and, therefore, mass transport before or during comet formation must have occurred at least up to the region where Kuiper Belt comets formed (~30 AU).
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
journal title
Geochimica et Cosmochimica Acta
Geochim. Cosmochim. Acta
volume
17
issue
18
pages
5483 - 5492
Web of Science type
Article
Web of Science id
000269401600018
JCR category
GEOCHEMISTRY & GEOPHYSICS
JCR impact factor
4.385 (2009)
JCR rank
2/74 (2009)
JCR quartile
1 (2009)
ISSN
0016-7037
DOI
10.1016/j.gca.2009.06.008
language
English
UGent publication?
yes
classification
A1
copyright statement
I don't know the status of the copyright for this publication
id
771710
handle
http://hdl.handle.net/1854/LU-771710
date created
2009-11-03 11:04:53
date last changed
2009-11-09 14:00:31
@article{771710,
  abstract     = {We detected additional CAI-like material in STARDUST mission samples of comet 81P/Wild 2. Two highly refractory
cometary dust fragments were identified in the impact track 110 [C2012, 0, 110, 0, 0] by applying high resolution synchrotron
induced confocal and conventional XRF analysis (HR SR-XRF). The use of a polycapillary lens in front of the detector for
confocal spectroscopy dramatically improves the fidelity of particle measurements by removing contribution from the surrounding
aerogel. The high spatial resolution (300 x 300 nm2; 300 x 1000 nm2) obtained allowed the detailed non-destructive
in situ (trapped in aerogel) study of impacted grains at the sub-lm level.
For the two largest particles of the track, the terminal particle and a second particle along the impact track, Ca concentration
is up to 30 times higher than CI and Ti is enriched by a factor of 2 compared to CI. High resolution (HR) SR-XRF
mapping also reveals that the highest concentrations of Ca, Ti, Fe (and Ni) measured within each grain belongs to different
areas of the respective maps which indicate that the particles are composed of several chemically diverse mineral phases. This
is in agreement with the finding of a complex phase assemblage of highly refractory minerals in the first ever detected Stardust
mission CAI grain {\textquoteleft}{\textquoteleft}Inti{\textquotedblright} of Track 25.
Principle component analysis (PCA) is a powerful tool for extracting the dominant mineral components and was applied to
the two grains indicating that regions in the terminal particle and the second particle are consistent with anorthite or grossite
and gehlenite, monticellite or Dmitryivanovite (CaAl2O4), respectively.
Our new findings demonstrate that the HR SR-XRF with confocal geometry and PCA analysis is capable of identifying
CAI-like fragments without the need to extract particles from the aerogel matrix which is a time-consuming, complex and
destructive process.
Furthermore, the detection of new CAI-like fragments in the coma dust of comet 81P/Wild 2 strengthens the observation
that strong mixing effects and, therefore, mass transport before or during comet formation must have occurred at least up to
the region where Kuiper Belt comets formed ({\texttildelow}30 AU).},
  author       = {Schmitz, Sylvia and Brenker, Frank and Schoonjans, Tom and Vekemans, Bart and Silversmit, Geert and Vincze, Laszlo and Burghammer, Manfred and Riekel, Christian},
  issn         = {0016-7037},
  journal      = {Geochimica et Cosmochimica Acta},
  language     = {eng},
  number       = {18},
  pages        = {5483--5492},
  title        = {In situ identification of a CAI candidate in 81P/Wild 2 cometary dust by confocal high resolution synchrotron X-ray fluorescence},
  url          = {http://dx.doi.org/10.1016/j.gca.2009.06.008},
  volume       = {17},
  year         = {2009},
}

Chicago
Schmitz, Sylvia, Frank Brenker, Tom Schoonjans, Bart Vekemans, Geert Silversmit, Laszlo Vincze, Manfred Burghammer, and Christian Riekel. 2009. “In Situ Identification of a CAI Candidate in 81P/Wild 2 Cometary Dust by Confocal High Resolution Synchrotron X-ray Fluorescence.” Geochimica Et Cosmochimica Acta 17 (18): 5483–5492.
APA
Schmitz, S., Brenker, F., Schoonjans, T., Vekemans, B., Silversmit, G., Vincze, L., Burghammer, M., et al. (2009). In situ identification of a CAI candidate in 81P/Wild 2 cometary dust by confocal high resolution synchrotron X-ray fluorescence. Geochimica et Cosmochimica Acta, 17(18), 5483–5492.
Vancouver
1.
Schmitz S, Brenker F, Schoonjans T, Vekemans B, Silversmit G, Vincze L, et al. In situ identification of a CAI candidate in 81P/Wild 2 cometary dust by confocal high resolution synchrotron X-ray fluorescence. Geochimica et Cosmochimica Acta. 2009;17(18):5483–92.
MLA
Schmitz, Sylvia, Frank Brenker, Tom Schoonjans, et al. “In Situ Identification of a CAI Candidate in 81P/Wild 2 Cometary Dust by Confocal High Resolution Synchrotron X-ray Fluorescence.” Geochimica et Cosmochimica Acta 17.18 (2009): 5483–5492. Print.