SATURN'S RINGS SURGE IN BRIGHTNESS [1]
Spaceweather.com - 4/29/13
"The rings are very bright due to the Seeliger Effect," says Go. Also known as the "opposition effect," the Seeliger effect has been observed on the Moon [2], Earth [3] and Mars [4]. It happens when sunlit objects (such as the icy particles that make up Saturn's rings) hide their own shadows [5]. A process called coherent backscattering [6] may also contribute to the extra luminosity.
Link: Spaceweather.com [7]