Looking Below the Moon’s Surface With Radar
A nearly complete map of the lunar nearside at 70-centimeter wavelength has been collected using the radar transmitter on the U.S. National Science Foundation’s Arecibo telescope in Puerto Rico and receivers on the NSF’s Robert C. Byrd Greenbank Telescope in West Virginia. These data have been submitted to the Planetary Data System in a format that makes them useful for a variety of lunar science applications.
By B. A. Campbell et al.
For those without access, here's the concluding paragraph:
QUOTEThe new lunar maps show the complementary nature of long-wavelength radar observations and other remote sensing measurements. For the Moon, the thickness of the impact-gardened layer means that most applications focus on the properties of the mixed rock and dust. On Mars, however, there are many areas where important geologic features are obscured by centimeters to meters of fine sediment. A long wavelength orbital radar sensor could look beneath these mantling materials to reveal ancient terrain sculpted by impacts, volcanism, wind, water, and ice.
Too bad that proposal (i.e., a Mars orbital SAR mission) never made it through the Mars Scout sieve. I've been in favor of one for a long time