Laboratory measurements of light polarization on samples targeted for the lunar regolith

We carried out multi-band (B, V, and R bands) polarimetric measurements of several soil samples targeted for the lunar regolith (JSC-1A, Fe2O3, SiC, and JSC-1Mars). Our laboratory experiments are intended to provide some constraints to the theoretical and numerical studies of the light scattering off the particulate surface of airless bodies in the solar system. Among our samples, the lunar soil simulant JSC-1A has the closest αmax to the typically observed value on the lunar surface, ∼100°, where αmax is the phase angle at which the polarization has the maximum value. In the other samples, αmax is higher than 120° or significantly wavelength dependent. The empirical relationship between the grain size, maximum polarization and albedo for the lunar regolith overestimates the actual grain sizes of some of our samples by a factor of up to ∼6. The measured polarization degrees and albedos of the JSC-1A sample are similar to the typical observed values of the lunar maria. We also find that the wavelength dependence of both polarization degree and albedo is larger for smaller-grain samples.