Application of stochastic wave approach to the problem of backscattering from the surfaces of airless cosmic bodies

A model is introduced to discuss the enhanced backscattering of light from the surfaces of bright, airless cosmic bodies. The surface layer that reflects the radiation is assumed to consist of large-scale, semitransparent, stochastically distributed grains. We argue that in the case of semitransparent grains it does not make any sense to divide the backscattered signal into two different parts produced by two different mechanisms—shadow hiding and coherent backscattering. It is shown that the phase and the amplitude fluctuations acquired by the wave penetrating into such a layer play a crucial role in the process of backscattering providing a broad pedestal and a narrow peak. Our results, in accordance with the experimental data, demonstrate a rather weak angular dependance of the backscattering peak on the size of the grains and the wavelength. The model deals only with media in which the refractive index is close to unity and the samples are optically thin. Therefore, our model does not correspond to physical properties of real regolith and its laboratory simulants. However, even in its present form the model describes qualitatively correctly some of the unexplained experimental results.