The fusion crust of the Winchcombe meteorite: a preserved record of atmospheric entry processes

Genge, M. J. et al. (2023) The fusion crust of the Winchcombe meteorite: a preserved record of atmospheric entry processes. Meteoritics and Planetary Science, (doi: 10.1111/maps.13937) (Early Online Publication)

Abstract

Fusion crusts form during the atmospheric entry heating of meteorites and preserve a record of the conditions that occurred during deceleration in the atmosphere. The fusion crust of the Winchcombe meteorite closely resembles that of other stony meteorites, and in particular CM2 chondrites, since it is dominated by olivine phenocrysts set in a glassy mesostasis with magnetite, and is highly vesicular. Dehydration cracks are unusually abundant in Winchcombe. Failure of this weak layer is an additional ablation mechanism to produce large numbers of particles during deceleration, consistent with the observation of pulses of plasma in videos of the Winchcombe fireball. Calving events might provide an observable phenomenon related to meteorites that are particularly susceptible to dehydration. Oscillatory zoning is observed within olivine phenocrysts in the fusion crust, in contrast to other meteorites, perhaps owing to temperature fluctuations resulting from calving events. Magnetite monolayers are found in the crust, and have also not been previously reported, and form discontinuous strata. These features grade into magnetite rims formed on the external surface of the crust and suggest the trapping of surface magnetite by collapse of melt. Magnetite monolayers may be a feature of meteorites that undergo significant degassing. Silicate warts with dendritic textures were observed and are suggested to be droplets ablated from another stone in the shower. They, therefore, represent the first evidence for intershower transfer of ablation materials and are consistent with the other evidence in the Winchcombe meteorite for unusually intense gas loss and ablation, despite its low entry velocity.

• Item Type: Articles
• Additional Information: STFC are acknowledged for supporting the “Curation and Preliminary Examination of the Winchcombe Carbonaceous Chondrite Fall” project (ST/V000799/1).
• Status: Early Online Publication
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Daly, Dr Luke and Jenkins, Miss Laura
• Authors: Genge, M. J., Alesbrook, L., Almeida, N. V., Bates, H. C., Bland, P. A., Boyd, M. R., Burchell, M. J., Collins, G. S., Cornwell, L. T., Daly, L., Devillepoix, H. A.R., van Ginneken, M., Greshake, A., Hallatt, D., Hamann, C., Hecht, L., Jenkins, L. E., Johnson, D., Jones, R., King, A. J., Mansour, H., McMullan, S., Mitchell, J. T., Rollinson, G., Russell, S. S., Schröder, C., Stephen, N. R., Suttle, M. D., Tandy, J. D., Trimby, P., Sansom, E. K., Spathis, B., Willcocks, F. M., and Wozniakiewicz, P. J.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Meteoritics and Planetary Science
• Publisher: Wiley
• ISSN: 1086-9379
• ISSN (Online): 1945-5100
• Published Online: 02 January 2023
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Meteoritics and Planetary Science 2023
• Publisher Policy: Reproduced under a Creative Commons License