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Improved Discrimination of Volcanic Complexes, Tectonic Features, and Regolith Properties in Mare Serenitatis from Earth-Based Radar MappingRadar images at 70 cm wavelength show 4-5 dB variations in backscatter strength within regions of relatively uniform spectral reflectance properties in central and northern Mare Serenitatis, delineating features suggesting lava flow margins, channels, and superposition relationships. These backscatter differences are much less pronounced at 12.6 cm wavelength, consistent with a large component of the 70 cm echo arising from the rough or blocky transition zone between the mare regolith and the intact bedrock. Such deep probing is possible because the ilmenite content, which modulates microwave losses, of central Mare Serenitatis is generally low (2-3% by weight). Modeling of the radar returns from a buried interface shows that an average regolith thickness of 10m could lead to the observed shifts in 70 cm echo power with a change in TiO2 content from 2% to 3%. This thickness is consistent with estimates of regolith depth (10-15m) based on the smallest diameter for which fresh craters have obvious blocky ejecta. The 70 cm backscatter differences provide a view of mare flow-unit boundaries, channels, and lobes unseen by other remote sensing methods. A localized pyroclastic deposit associated with Rima Calippus is identified based on its low radar echo strength. Radar mapping also improves delineation of units for crater age dating and highlights a 250 km long, east-west trending feature in northern Mare Serenitatis that we suggest is a large graben flooded by late-stage mare flows.
Document ID
20160008402
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Campbell, Bruce A. (Smithsonian Institution Washington, DC, United States)
Hawke, B. Ray (Hawaii Univ. at Manoa Honolulu, HI, United States)
Morgan, Gareth A. (Smithsonian Institution Washington, DC, United States)
Carter, Lynn M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Campbell, Donald B. (Cornell Univ. Ithaca, NY, United States)
Nolan, Michael (Arecibo Ionospheric Observatory Arecibo, Puerto Rico)
Date Acquired
July 1, 2016
Publication Date
February 6, 2014
Publication Information
Publication: Journal of Geophysical Research: Planets
Volume: 119
Issue: 2
Subject Category
Geosciences (General)
Report/Patent Number
GSFC-E-DAA-TN21225
Funding Number(s)
CONTRACT_GRANT: NSF AST-1100968
CONTRACT_GRANT: NNX12AF24G
Distribution Limits
Public
Copyright
Other
Keywords
Radar echoes
Regolith thickness
Radar observations