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Orbital radar evidence for lunar subsurface layering in Maria Serenitatis and Crisium

1978; American Geophysical Union; Volume: 83; Issue: B7 Linguagem: Inglês

10.1029/jb083ib07p03459

2156-2202

W. J. Peeples, W.R. Sill, Thomas W. May, S. H. Ward, R. J. Phillips, R. Jordan, Elsa Abbott, Terry J. Killpack,

Space Science and Extraterrestrial Life

Data from the lunar‐orbiting Apollo 17 radar sounding experiment (60‐m wavelength) have been examined in both digital and holographic formats. Surface backscatter (clutter) which masks possible radar returns originating from subsurface changes in lunar electrical properties was reduced by simultaneously comparing radar data from two orbits. Radar returns that correlate from orbit to orbit form two distinct alignments in Mare Serenitatis and one in Mare Crisium. It is proposed that these alignments represent subsurface reflecting horizons. The hypothesis is tested by showing that (1) most of the radar returns fall outside the ambiguity region of the correlation technique, (2) the results are consistent between optically and digitally processed data, (3) the signal levels of the proposed subsurface features are well above the noise floor, (4) the inferred loss tangents appear to be consistent with returned sample measurements, and (5) the discontinuous nature of the reflections most likely arises from interference effects. It is concluded that there are two subsurface radar reflectors with mean apparent depths of 0.9 km and 1.6 km below the surface in Mare Serenitatis and one reflector at a mean depth of 1.4 km below the surface in Mare Crisium. These reflectors represent basin‐wide subsurface interfaces.