Ultraviolet Radiation Inside Interstellar Grain Aggregates. Iii. Fluffy Grains

We study the problem of light depolarization within fluffy interstellar dust grains, in which coagulation generates interstitial cavities partly filled with icy condensed gas. A significant amount of elliptical polarized ultraviolet radiation may be generated in situ by geometry-induced depolarization within the cavities. The behavior of the depolarization is studied both by changing the orientation of the aggregates and by changing chemical composition and size of the subunits forming the aggregate. We found that a considerable amount of depolarization occurs within the ice mantles of the subunits, provided their thickness is not too large. We discuss the implications of these results for chiral selection in space.