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The origin of crystalline residues in Stardust Al foils: Surviving cometary dust or crystallized impact melts?

Wozniakiewicz, Penelope J., Kearsley, Anton T., Ishii, Hope A., Burchell, Mark J., Bradley, John P., Teslick, Nick, Cole, Mike J., Price, Mark C. (2012) The origin of crystalline residues in Stardust Al foils: Surviving cometary dust or crystallized impact melts? Meteoritics & Planetary Science, 47 (4). pp. 660-670. ISSN 1086-9379. (doi:10.1111/j.1945-5100.2011.01328.x) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:36165)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
http://dx.doi.org/10.1111/j.1945-5100.2011.01328.x

Abstract

Samples returned by the Stardust mission from comet 81P/Wild 2 provide an unequaled opportunity to investigate cometary formation and evolution. Crystalline silicates have been identified in impact craters in Stardust Al foil, yet their origin is ambiguous. They may be original cometary components, or they may have grown from melt generated by impact. We have now studied experimental impacts of the calcium silicate mineral wollastonite, using scanning and transmission electron microscopy to document the relationship between impact feature shape and crystal lattice orientation in impact residue. Wollastonite can have a characteristic acicular habit, forming crater shapes that indicate crystal orientation upon impact. From extracted impact residue, we determined the lattice orientation of crystalline material for comparison with the whole particle orientation. We assume that crystallization from melt, without surviving seed nuclei, should result in randomly oriented crystallite growth, with no preferred direction for individual crystals. However, we find that the majority of crystalline material in the residue retains b-axis orientation parallel to the long axis of the crater form. This, together with impact parameter calculations and lack of Al incorporation by the residue (suggesting melting did not occur), indicates that these crystals and, by analogy, the majority of Al-free crystalline silicates in Stardust foil, are surviving remnants of the impactor. Furthermore, amorphous wollastonite residue probably did not form via melting and subsequent quenching, but instead by high-pressure amorphization or degradation of unquenchable phases. Finally, one crystal studied appears to be a new high-pressure/temperature polymorph of CaSiO3, indicating that such polymorphs may be observed in Stardust residues in craters.

Item Type: Article
DOI/Identification number: 10.1111/j.1945-5100.2011.01328.x
Subjects: Q Science > QB Astronomy
Q Science > QE Geology > QE515 Geochemistry
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Mark Burchell
Date Deposited: 11 Nov 2013 15:15 UTC
Last Modified: 01 Aug 2019 10:36 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/36165 (The current URI for this page, for reference purposes)
Burchell, Mark J.: https://orcid.org/0000-0002-2680-8943
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