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Along-track compositional and textural variation in extensively melted grains returned from comet 81P/Wild 2 by the Stardust mission: Implications for capture-melting process
- Source :
- Meteoritics & Planetary Science. 44:1519-1540
- Publication Year :
- 2010
- Publisher :
- Wiley, 2010.
-
Abstract
- Five amorphous (extensively melted) grains from Stardust aerogel capture Track 35 were examined by transmission electron microscopy (TEM); two from the bulb, two from near the bulbstylus transition, and one from near the terminal particle. Melted grains consist largely of a texturally and compositionally heterogeneous emulsion of immiscible metal/sulfide beads nanometers to tens of nanometers in diameter in a silica-rich vesicular glass. Most metal/sulfide beads are spherical, but textures of non-spherical beads indicate that some solidified as large drops during stretching and breaking while in translational and rotational motion, and others solidified from lenses of immiscible liquid at the silicate-melt/vesicle (vapor) interface. Melted grains appear to become richer in Fe relative to Mg, and depleted in S relative to Fe and Ni with increasing penetration distance along the aerogel capture track. Fe/S ratios are near unity in grains from the bulb of Track 35, consistent with the dominance of Fe-monosulfide minerals inferred by previous research on Stardust materials. Near stoichiometric Fe/S in melted grains from the bulb suggests that Fe-sulfides in the bulb were dispersed and melted during formation of the bulb but did not lose S. Along-track increases in Fe/S in melted grains from the bulb through the bulb-stylus transition and continuing into the stylus indicate that S initially present as iron monosulfide may have been progressively partially volatilized and lost from the melted grains with greater penetration of the grains deeper into the aerogel during capture-melting of comet dust. Extensively melted grains from the bulbs of aerogel capture tracks may preserve better primary compositional information with less capture-related modification than grains from farther along the same capture tracks.
- Subjects :
- chemistry.chemical_classification
Materials science
Sulfide
Comet dust
Mineralogy
Aerogel
Iron sulfide
Amorphous solid
Metal
chemistry.chemical_compound
Geophysics
chemistry
Space and Planetary Science
Transmission electron microscopy
visual_art
visual_art.visual_art_medium
Composite material
Stoichiometry
Subjects
Details
- ISSN :
- 10869379
- Volume :
- 44
- Database :
- OpenAIRE
- Journal :
- Meteoritics & Planetary Science
- Accession number :
- edsair.doi...........35e0d24a6459d0b8cbecc3b3019e2e2f