Theory and application of the polarization-albedo rules

Results are reported of a computer calculation of the scattering of light from porous, particulate surfaces such as those of the Moon, asteroids, and airless planets. The scattered-light intensity and polarization are computed as a function of phase angle, and plots are made corresponding to the observed empirical rules for deducing albedo from the slope, maximum, and minimum of polarization curves. The approximate linearity of these rules on a log-log plot is confirmed for most solar system objects. The linearity is due to the similarity of the real indices of refraction of solar system soils. The theory shows that the albedo vs polarization plots correspond directly to a plot, in two dimensions, of the real vs imaginary index of refraction of these soils, using curved axes. This new information provides a straightforward method of measuring optical and structural properties of the major soil constituents leading to mineral identification. The theory is based upon geometric optics with an estimated error of 5 to 10% which agrees reasonably well with available measurements. A comparison is made with 30 asteroids and some moons. The soils of these bodies appear similar to that of the Earth, with some interesting exceptions.