Abstract
We model cometary dust by taking into account its formation and evolution. Light scattering, absorption, and emission properties of the dust expected from our model are compared with observations. We assume that cometary dust is primordial interstellar dust or agglomeration of the dust. We model unprocessed cometary dust using fractal aggregates of submicron grains having an amorphous silicate core and an organic refractory mantle. We show that the wavelength and phase-angle dependences of intensity and linear polarization as well as the low albedo of cometary dust are correctly reproduced by our model. Infrared spectra of cometary dust are consistent with our assumption that long-period comets consist mainly of D=2 dust while short-period comets contain D=3 dust. We also consider the possibility that explosive reactions of radicals in the organic refractory mantle crystallize amorphous silicates after ejection from cometary nuclei. In this case, we can identify infrared silicate features with forsterite, inclusive of a supposedly enstatite feature.
