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Mineralogical Changes in IDPS Resulting From Atmospheric Entry Heating

Published online by Cambridge University Press:  27 February 2018

Lindsay P Keller ,
Kathie L. Thomas  and
David S. McKay
Lindsay P Keller
Affiliation:
MVA, Inc., 5500 Oakbrook Parkway, Suite 200, Norcross, GA 30093
Kathie L. Thomas
Affiliation:
Code C23, Lockheed-Martin NASA/JSC, Houston, TX 77058
David S. McKay
Affiliation:
Code SN, NASA-Johnson Space Center, Houston, TX 77058

Abstract

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All extraterrestrial particles are heated during their passage through the Earth's atmosphere. The mineral assemblages that form during entry heating can be used to constrain the maximum temperature attained which, in turn, places limits on their entry velocity Entry velocity can be used to discriminate typical cometary IDPs from asteroidal particles.

A common feature of heated IDPs is the presence of magnetite (Mt) rims on the particle surface. These rims range from thin, discontinuous Mt layers on lobes or on small constituent grains within lightly heated IDPs, to thick, continuous, polycrystalline rims that completely surround many strongly heated particles. Petrographic evidence indicates that Mt rims form directly from individual phases in IDPs via oxidation of Fe from the host phases. Our data indicate that the temperature of magnetite formation can range from a minimum of ~600°C (by decarbonation of Fe-bearing carbonates and the breakdown of phyllosilicates) to T > 850°C (decomposition of laihunite). In extreme cases, μm-sized Mt plates armor the surface of partly melted chondritic IDPs. Magnetite rims are more well-developed on hydrated IDPs than on anhydrous particles. The development of magnetite rims correlates with other independent indicators of heating including loss of volatile trace elements and sulfur depletions.

Type
VIII. Chemistry of the Interplanetary Dust
Information
International Astronomical Union Colloquium , Volume 150: Physics, Chemistry and Dynamics of Interplanetary Dust , 1996 , pp. 295 - 298
Copyright
Copyright © Astronomical Society of the Pacific 1996

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