Light scattering by droplets containing small chiral particles

We calculate the light-scattering properties of methane and water droplets containing spiral particles, which may simulate the presence of biological or prebiotic components. Such aerosols are present in the atmosphere of Earth and Titan. We focus our studies on the circular-polarization Mueller-matrix element М₁₄ that has been considered a tool for remote sensing biological materials. Unlike the non-zero elements of spheres (M₁₁, M₁₂, M₂₁, M₂₂, M₃₃, M₃₄, M₄₃, and M₄₄), the signals of the remaining off-diagonal elements (M₁₃, M₁₄, M₂₃, M₂₄, M₃₁, M₃₂, M₄₁, and M₄₂) do not show any regions of preferential positive or negative polarization. While our simulations show the М₁₄ element reaching 70% polarization, when orientation averaging is performed on this signal, it is reduced by over an order of magnitude. Such a reduction in signal does not occur for the non-zero elements of spheres, which have a stronger dependence on the spherical interface. Our simulations suggest that the circular-polarization opposition effect appears to be present in such particles, but it is difficult to discern because of the oscillations of the circular intensity differential scattering parameter (CIDS) signal.