Article

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

Geosciences Institute/Mineralogy, Goethe University Frankfurt, Altenhoeferallee 1, D-60438 Frankfurt, Germany; Department of Analytical Chemistry, Ghent University, Krijgslaan 281 S12, B-9000 Ghent, Belgium; ESRF, 6 rue Jules Horowitz, BP220, F-38043 Grenoble Cedex, France
Geochimica et Cosmochimica Acta (Impact Factor: 3.88). 01/2009; DOI: 10.1016/j.gca.2009.06.008

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 × 300 nm2; 300 × 1000 nm2) obtained allowed the detailed non-destructive in situ (trapped in aerogel) study of impacted grains at the sub-μm 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).

0 Bookmarks
 · 
44 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this review we highlight the performance of confocal micro X-ray fluorescence (CMXRF) for application in environmental science, citing contributions from recent studies (2008-2010). In CMXRF the use of focusing and collecting optics enables discrimination of the origin of fluorescence photons in three dimensions. It thereby enables simple and direct three dimensional imaging, and also the removal of unwanted signal contribution either from the depth of the sample or from its surface. By limiting the area of origin of fluorescence signal CMXRF can simplify quantitative approaches.
    Analytical and Bioanalytical Chemistry 04/2011; 400(6):1743-50. · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We review methods and recent studies in which macroscopic to (sub)microscopic X-ray beams were used for nondestructive analysis and characterization of pigments, paint microsamples, and/or entire paintings. We discuss the use of portable laboratory- and synchrotron-based instrumentation and describe several variants of X-ray fluorescence (XRF) analysis used for elemental analysis and imaging and combined with X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Macroscopic and microscopic (μ-)XRF variants of this method are suitable for visualizing the elemental distribution of key elements in paint multilayers. Technical innovations such as multielement, large-area XRF detectors have enabled such developments. The use of methods limited to elemental analysis or imaging usually is not sufficient to elucidate the chemical transformations that take place during natural pigment alteration processes. However, synchrotron-based combinations of μ-XRF, μ-XAS, and μ-XRD are suitable for such studies.
    Annual Review of Analytical Chemistry (2008) 06/2013; 6(1):399-425. · 8.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 3D micro X-ray fluorescence analysis (3D Micro-XRF) is a non-destructive method for the investigation of elemental compositions of specimens with which three-dimensionally resolved information can be obtained. This is rendered possible through the formation of a probing volume resulting from the overlap of a condensed X-ray beam and the acceptance of a polycapillary lens in front of an energy-dispersive detector. Various setup schemes have been developed in the last years, which can be divided into synchrotron instrumentation and X-ray tube based spectrometers. Established in 2003/2004 numerous applications have been published up until now. Quantification of data though is still a topic of considerable interest and has been reported only for limited number of publications. This review aims to give an overview of work on quantitative 3D Micro-XRF. As the method can be applied with adapted setups to a variety of analytical problems, quantification also has to be flexible and different schemes have been developed.
    Spectrochimica Acta Part B Atomic Spectroscopy 11/2012; 77:9–18. · 3.14 Impact Factor