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Lobate impact melt flows within the extended ejecta blanket of Pierazzo crater

Bray, Veronica J.; Atwood-Stone, Corwin; Neish, Catherine D.; Artemieva, Natalia A.; McEwen, Alfred S.; McElwaine, Jim N.

Lobate impact melt flows within the extended ejecta blanket of Pierazzo crater Thumbnail


Authors

Veronica J. Bray

Corwin Atwood-Stone

Catherine D. Neish

Natalia A. Artemieva

Alfred S. McEwen



Abstract

Impact melt flows are observed within the continuous and discontinuous ejecta blanket of the 9 km lunar crater Pierazzo, from the crater rim to more than 40 km away from the center of the crater. Our mapping, fractal analysis, and thermal modeling suggest that melt can be emplaced ballistically and, upon landing, can become separated from solid ejecta to form the observed flow features. Our analysis is based on the identification of established melt morphology for these in-ejecta flows and supported by fractal analysis and thermal modeling. We computed the fractal dimension for the flow boundaries and found values of D = 1.05–1.17. These are consistent with terrestrial basaltic lava flows (D = 1.06–1.2) and established lunar impact melt flows (D = 1.06–1.18), but inconsistent with lunar dry granular flows (D = 1.31–1.34). Melt flows within discontinuous ejecta deposits are noted within just 1.5% of the mapping area, suggesting that the surface expression of impact melt in the extended ejecta around craters of this size is rare, most likely due to the efficient mixing of melts with solid ejecta and local target rocks. However, if the ejected fragments (both, molten and solid) are large enough, segregation of melt and its consequent flow is possible. As most of the flows mapped in this work occur on crater-facing slopes, the development of defined melt flows within ejecta deposits might be facilitated by high crater-facing topography restricting the flow of ejecta soon after it makes ground contact, limiting the quenching of molten ejecta through turbulent mixing with solid debris. Our study confirms the idea that impact melt can travel far beyond the continuous ejecta blanket, adding to the lunar regolith over an extensive area.

Citation

Bray, V. J., Atwood-Stone, C., Neish, C. D., Artemieva, N. A., McEwen, A. S., & McElwaine, J. N. (2017). Lobate impact melt flows within the extended ejecta blanket of Pierazzo crater. Icarus, 301, 26-36. https://doi.org/10.1016/j.icarus.2017.10.002

Journal Article Type Article
Acceptance Date Oct 2, 2017
Online Publication Date Oct 13, 2017
Publication Date Oct 13, 2017
Deposit Date Dec 14, 2017
Publicly Available Date Mar 29, 2024
Journal Icarus
Print ISSN 0019-1035
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 301
Pages 26-36
DOI https://doi.org/10.1016/j.icarus.2017.10.002

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