Scattering Mechanisms Associated with High Circular Polarization Ratios from Young, Large Craters on the Moon

Abstract

The crater floors and walls of youngest impact craters on the Moon are some of the roughest surfaces at radar wavelengths due to the presence of rocky debris and impact melt sheets. In this work, we examine the radar polarization properties of the interior region of three of the youngest craters on the Moon that are Tycho, Jackson, and Giordano Bruno at 25-cm wavelength radar data obtained from the DFSAR instrument onboard Chandrayaan-2, and compare them to the predicted behaviors of theoretical radar scattering models. We suggest that the high radar circular polarization ratio (CPR) values observed from the young crater floors can be explained by a double-bounce dipole (diffuse scattering) model through scattering from and between tens of centimeter scale rock edges and cracks. We also infer that the highest CPR enhancements from the floor of the young impact craters analyzed in this work are caused by dihedral scattering between natural corner reflectors such as rocks many times the size of illuminating wavelength or between rock faces and the regolith.