Richardson, J.E., Veverka, J. and Thomas, P.C. (2006). "Large Impact Features on Phoebe and Hyperion: Early Analysis Results." American Astronomical Society, DPS meeting #38, #69.


Abstract
The Cassini Imaging Science Subsystem (ISS) has obtained data on both Phoebe (mean radius 106 km) and Hyperion (mean radius 135 km) during close flybys. These two satellites are drastically different in appearance, but both contain large impact features, on the order of the host satellite's mean radius in diameter. In particular, the largest impact feature on Hyperion, of mean diameter 230 km, displays evidence of extensive crater collapse, including a region which resembles a central peak, despite Hyperion's small size (and presumed inability to produce complex craters). We use topographic models and crater density data to investigate the mechanisms and effects of large crater formation on these small objects. Differences in the morphology of large craters, and in modification processes (such as landslides) may be attributed to the considerably different densities, gravities, and compositions of the two satellites.