Atmospheric Alteration in Fine-Grained Antarctic Micrometeorites

Details Atmospheric Alteration in Fine-Grained Antarctic Micrometeorites Atmospheric Alteration in Fine-Grained Antarctic Micrometeorites

Mar 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996lpi....27..399g&link_type=abstract

Lunar and Planetary Science, volume 27, page 399

Computer Science

1

Micrometeorites, Micrometeorites: Alteration, Micrometeorites: Compositions, Micrometeorites: Textures

Scientific paper

(AMMs) in the size range 50-100mm were examined by scanning electron microscopy and electron microprobe techniques to differentiate primary 'pre-atmospheric' characteristics from those originating from alteration in the atmosphere. Results indicate that the majority of particles (61) are completely or partially melted during atmospheric deceleration attaining peak temperatures in excess of ~1600 degrees C. A significant number of particles (18) containing relict phyllosilicates have evidently been heated to temperatures less than 600-900 degrees C. The matrix compositions of the examined AMMs broadly support previous theoretical predictions that all particles >50mm have suffered some degree of partial vaporisation or melting during aerobraking, however, they also imply that predicted peak temperatures are severely overestimated. It is infered from particle textures that cosmic dust particles >50mm can support both high thermal gradients (~1000 degrees C) and may develop hydrodynamical bow-shocks: phenomena which are specifically excluded from theoretical treatments. Matrix compositions also testify to volatile enrichments of the elements K, Cl, F, and P presumably as the result of reactions with atmospheric species. A reaction mechanism is suggested for the observed coupled enrichment of K and Cl.

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