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Improved discrimination of volcanic complexes, tectonic features, and regolith properties in Mare Serenitatis from Earth‐based radar mapping
Author(s) -
Campbell Bruce A.,
Ray Hawke B.,
Morgan Gareth A.,
Carter Lynn M.,
Campbell Donald B.,
Nolan Michael
Publication year - 2014
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2013je004486
Subject(s) - volcano , regolith , geology , tectonics , earth (classical element) , radar , remote sensing , astrobiology , earth science , seismology , aerospace engineering , engineering , physics , mathematical physics
Radar 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 10 m could lead to the observed shifts in 70 cm echo power with a change in TiO 2 content from 2% to 3%. This thickness is consistent with estimates of regolith depth (10–15 m) 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.