Modeling Radar Albedos of Laboratory‐Characterized Particles: Application to the Lunar Surface

Abstract

Abstract We analyze lunar images obtained by the Mini Radio Frequency instrument onboard the Lunar Reconnaissance Orbiter to interpret the anomalous radar scattering observed in some lunar craters. We compare the radar signatures of the crater floors to those of the regions external to the crater rim and show that there is a systematic difference between the radar albedo trends of the two regions. Using numerical simulations to compute radar scattering properties of rock and ice particles, we demonstrate that the difference is caused partly by the near‐surface bulk volume density or the underlying fine‐grained regolith and partly by the shape and size distributions of centimeter‐to‐decimeter‐scale rubble. We show that while the size distribution of wavelength‐scale particles plays the major role in the observed radar albedos, if the size distribution is fixed, the particle shapes can play a greater role than the composition; therefore, the icy material is indistinguishable from silicate‐rich material unless the abundance of ice in the particles plays a major role in the shape of the particles.