Negative polarization of light at backscattering from a numerical analog of planetary regoliths

We model negative polarization, which is observed for planetary regoliths at backscattering, solving a full wave problem of light scattering with a numerically exact Discontinuous Galerkin Time Domain (DGTD) method. Pieces of layers with the bulk packing density of particles close to 0.5 are used. The model particles are highly absorbing and have irregular shapes and sizes larger than the wavelength of light. This represents a realistic analog of low-albedo planetary regoliths. Our simulations confirm coherent backscattering mechanism of the origin of negative polarization. We show that angular profiles of polarization are stabilized if the number of particles in a layer piece becomes larger than ten. This allows application of our approach to the negative polarization modeling for planetary regoliths. •A full wave solution of the problem of light scattering from a realistic model of low-albedo planetary regolith is presented.•Polarization near backscattering is formed by single and double scattering in the very upper layer of a particulate surface.•Negative polarization is produced by coherent double scattering.•Radiative transfer approach is not applicable to regoliths with absorbing particles larger than the wavelength.