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Bistatic radar analysis of buried basaltic maria on the Moon

Presentation #207.04 in the session Moon & Earth II (Oral Presentation)

Published onOct 23, 2023
Bistatic radar analysis of buried basaltic maria on the Moon

Understanding lunar volcanism is important for constraining the thermal and geologic history and evolution of the Moon. Maria are the remnants of effusive, basaltic lava flows predominantly observable across the nearside of the Moon. Cryptomaria is the term for maria that were buried by basin and crater ejecta after their initial eruption.

Radar, with wavelengths varying from centimeters to decameters, offers the ability to probe the subsurface and detect geologic units not otherwise apparent at the surface. At radar wavelengths, ilmenite is generally attenuating, leading to mare that exhibits characteristically low backscatter. Using this property, Bramson et al. (2023) produced a map of proposed cryptomaria versus burial depth across the Schiller-Schickard region. This map was based on ground-based P-band (70-cm wavelength) radar data collected by Arecibo Observatory and Green Bank Observatory. Here, we follow up on that study by using Lunar Reconnaissance Orbiter Mini-RF radar data at S and X bands (12.6-cm and 4.2-cm wavelengths), collected in bistatic mode (Earth-based transmission and Mini-RF receiving), to characterize mare and cryptomare units. Analysis of these datasets provides additional wavelength coverage, as well as the ability to inspect for unique phase-angle-dependent signatures, of maria/cryptomaria.

We have four Mini-RF bistatic data collects across the Schiller-Schickard region: three in S band and one in X band. At S band (12.6 cm), we again observe the low backscatter in regions of maria relative to the surrounding terrain. Cryptomaria exhibit intermediate backscatter values, which is expected if the radar is indeed detecting some basaltic materials within/underneath the highlands/ejecta coating. However, at X band, the maria exhibit a higher mean SC backscatter compared to the surroundings. Cryptomaria show same sense (SC) backscatter similar to surroundings. These results suggest that the Schiller-Schickard maria have abundant wavelength-scale (4.2 cm) scatterers and roughness which dominates the signal compared to composition, but areas of the shallowest cryptomaria may still be detectable, also highlighting the value in inter-wavelength comparative studies.

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