Multi-band Polarimetry of the Lunar Surface. II. Grain Size Evolutionary Pathway

Abstract To understand grain size evolution on the lunar surface in detail, we analyze the distribution of the average grain size for the lunar near side obtained by Jeong et al. Furthermore, we analyze the polarimetric properties of the regolith simulants SiC and JSC-1A in a laboratory. We find two characteristics of grain size evolution on the Moon. First, the lunar regolith has evolved on a specific evolutionary pathway in space. Here, Φ is defined as the ratio of the perpendicular ( ) and parallel ( ) components of the reflectance. Second, we also find that the evolutionary pathway depends on the FeO abundance and selenographic latitude of the surface. The dependence on the FeO content seems to result from the different resistance to comminution of regolith materials, and the dependence on the latitude seems to result from differences in the resurfacing environment. We present the probable causes of these characteristics of grain size evolution on the lunar surface.