What is "planetshine"

Planetshine is the illumination, by reflected sunlight from a planet, of part of the otherwise dark side of one of its moons. The best known example of planetshine is earthshine, which can be seen from Earth when the Moon is new, or nearly so. Typically, this results in the side of the Moon opposite the Sun being bathed in a soft, faint light. Planetshine has been observed elsewhere in the solar system: in particular, it has recently been used by the Cassini space probe to image portions of the moons of Saturn even when they are not directly lit by the Sun.