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Lunar Crater Ejecta: Physical Properties Revealed by Radar and Thermal Infrared ObservationsWe investigate the physical properties, and changes through time, of lunar impact ejecta using radar and thermal infrared data. We use data from two instruments on the Lunar Reconnaissance Orbiter (LRO) - the Diviner thermal radiometer and the Miniature Radio Frequency (Mini-RF) radar instrument - together with Earth-based radar observations. We use this multiwavelength intercomparison to constrain block sizes and to distinguish surface from buried rocks in proximal ejecta deposits. We find that radar-detectable rocks buried within the upper meter of regolith can remain undisturbed by surface processes such as micrometeorite bombardment for greater than 3 Gyr. We also investigate the thermophysical properties of radar-dark haloes, comprised of fine-grained, rock-poor ejecta distal to the blocky proximal ejecta. Using Diviner data, we confirm that the halo material is depleted in surface rocks, but show that it is otherwise thermophysically indistinct from background regolith. We also find that radar-dark haloes, like the blocky ejecta, remain visible in radar observations for craters with ages greater than 3 Ga, indicating that regolith overturn processes cannot replenish their block populations on that timescale.
Document ID
20170003186
Document Type
Reprint (Version printed in journal)
Authors
Ghent, R. R. (Toronto Univ. Ontario, Canada)
Carter, L. M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Bandfield, J. L. (Space Science Inst. Boulder, CO, United States)
Udovicic, C. J. Tai (Toronto Univ. Ontario, Canada)
Campbell, B. A. (Smithsonian Institution Washington, DC, United States)
Date Acquired
April 7, 2017
Publication Date
December 24, 2015
Publication Information
Publication: Icarus
Volume: 273
ISSN: 0019-1035
Subject Category
Lunar and Planetary Science and Exploration
Geosciences (General)
Report/Patent Number
GSFC-E-DAA-TN40589
Distribution Limits
Public
Copyright
Other