Cassini opened the shutter of its ISS camera for 100 seconds on January 19, 2006 on the thin crescent of Rhea. With the Sun coming nearly from behind Rhea, Cassini scientists hoped to see evidence for faint rings. However, no rings are visible in these images.
The rings are either too tenuous to scatter enough light to Cassini's cameras, or the material that they are made of does not scatter light as effectively as Saturn's dusty rings. Faint horizontal streaks in the background are stars, which appear streaked due to the long exposure. The background of the image is slightly brightened; this probably represents E ring material scattering light to the cameras. A diagonal line running across the sunlit limb is a diffraction pattern from within the optics of ISS, caused by the saturation of the sunlit limb during the extremely long exposure.