On the Prospects for Estimating the Properties of Particles in an Active Asteroid Exosphere by Features in the UV and Visible Reflectance Spectra

The reflectance spectra of active asteroids (AAs) measured in the visible and near-UV ranges exhibit unusual features, which are apparently caused by the light scattering in an exosphere formed under active processes on an asteroid. To estimate the prospects for a quantitative interpretation of these features, we numerically simulated reflectance spectra of an AA enveloped by an exosphere composed of aggregate submicron particles of various composition and morphology, as well as homogeneous submicron particles. We assumed that the sizes of aggregates’ constituents correspond to those of grains in agglomerates of cometary and interplanetary dust. It has been shown that the scattering on aggregates of submicron grains produces interference features at wavelengths shorter than 0.6 μm, and the positions of these features are determined by both the sizes of these grains (rather than the aggregates themselves) and the real part of their refractive index. The structure of an aggregate and variations (up to ±20