Modeling the scattering phase matrix of red clays

This Letter focuses on modeling the optical properties of red clay. Specifically, the measured phase matrix element P₂₂ of red clay shows a scattering-angle dependence that is quite different from those of other dust types, and has not been modeled successfully. The spheroidal particles cannot yield accurate agreement on all independent phase matrix elements of red clay simultaneously (failed for P₂₂). The P₂₂ element can be modeled well with the spheroidal model only by sacrificing the agreement on the other elements. However, the Koch-fractal model clearly outperforms the spheroidal model in reproducing all six phase matrix elements concurrently with a reasonable refractive index.