  We examine the surface brightnesses of Saturn's smaller satellites using a
photometric model that explicitly accounts for their elongated shapes and thus
facilitates comparisons among different moons. Analyses of Cassini imaging data
with this model reveals that the moons Aegaeon, Methone and Pallene are darker
than one would expect given trends previously observed among the nearby
mid-sized satellites. On the other hand, the trojan moons Calypso and Helene
have substantially brighter surfaces than their co-orbital companions Tethys
and Dione. These observations are inconsistent with the moons' surface
brightnesses being entirely controlled by the local flux of E-ring particles,
and therefore strongly imply that other phenomena are affecting their surface
properties. The darkness of Aegaeon, Methone and Pallene is correlated with the
fluxes of high-energy protons, implying that high-energy radiation is
responsible for darkening these small moons. Meanwhile, Prometheus and Pandora
appear to be brightened by their interactions with nearby dusty F ring,
implying that enhanced dust fluxes are most likely responsible for Calypso's
and Helene's excess brightness. However, there are no obvious structures in the
E ring that would preferentially brighten these two moons, so there must either
be something subtle in the E-ring particles' orbital properties that leads to
asymmetries in the relevant fluxes, or something happened recently to
temporarily increase these moons' brightnesses.
