Hedman, M. M., Burns, J. A., Tiscareno, M. S., Nicholson, P. D., Showalter, M. R., Cuzzi, J. N., Porco, C. C., et al. (2005). "Cassini's discoveries in the D and G rings." American Astronomical Society, DPS meeting #37, #66.02.

Recent Cassini observations of the D ring reveal that this faint, innermost component of Saturn's rings is much more complex and dynamic than previously realized. The structure of this region has changed significantly since it was last observed 25 years ago in a handful of Voyager images. For example, the relative brightnesses of the three numbered ringlets in this region have changed by an order of magnitude. High-resolution images from the ISS system taken at different times from multiple phase angles have also disclosed a variety of previously unknown structures, including periodic, wave-like patterns. Furthermore, these data demonstrate that different parts of the D ring have significantly different phase curves, which indicates the presence of more than one population of particles in this region. The VIMS instrument on Cassini has also detected the D ring, providing further constraints on the sizes and compositions of these ring particles.
Cassini's observations of the G ring yielded another surprise: this faint outer ring contains an arc of material which is both brighter and less radially extended than the rest of the G ring.