The smallest particles in Saturn's A and C Rings

The A Ring signal shows a similar level of scattered flux, but modeling is complicated by the presence of self-gravity wakes, which violate the assumption of a homogeneous ring, and higher optical depths, which require multiple-order scattering. If q < 3, our A Ring model requires a minimum particle size below one millimeter (<0.34 mm for an assumed q = 2.75, or 0.56-0.16+0.35 mm for a steeper q = 2.9) to be consistent with VIMS observations. These results might seem to contradict previous optical (Dones, L., Cuzzi, J.N., Showalter, M.R. [1993]. Icarus 105, 184-215) and infrared (French, R.G., Nicholson, P.D. [2000]. Icarus 145, 502-523) work, which implied that there were few particles in the A Ring smaller than 1 cm. But, because of the shallow power law, relatively little optical depth (between 0.03 and 0.16 in extinction, or 0.015-0.08 in absorption) is provided by these particles.