to be caused by the presence of thousands of small parent bodies (1.0 to 0.1 km in size) that collide and produce dense strands of micrometre- to centimetre-sized particles that re-accrete over a few months onto the parent bodies in a steady-state regime." Outer rings Janus/Epimetheus Ring A faint dust ring is present around the region occupied by the orbits of Janus and Epimetheus, as revealed by images taken in forward-scattered light by the Cassini spacecraft in 2006. The ring has a radial extent of about 5,000 km (3000 miles). Its source is particles blasted off the moons' surfaces by meteoroid impacts, which then form a diffuse ring around their orbital paths. G Ring The G Ring (see last image in gallery) is a very thin, faint ring about halfway between the F Ring and the beginning of the E Ring, with its inner edge about 15,000 km (10,000 miles) inside the orbit of Mimas. It contains a single distinctly brighter arc near its inner edge (similar to the arcs in the rings of Neptune) that extends about one-sixth of its circumference, centered on the half-km (500 yard) diameter moonlet Aegaeon, which is held in place by a 7:6 orbital resonance with Mimas. The arc is believed to be composed of icy particles up to a few m in diameter, with the rest of the G Ring consisting of dust released from within the arc. The radial width of the arc is about 250 km (150 miles), compared to a width of 9,000 km (6000 miles) for the G Ring as a whole. The arc is thought to contain matter equivalent to a small icy moonlet about a hundred m in diameter. Dust released from Aegaeon and other source bodies within the arc by micrometeoroid impacts drifts outward from the arc because of interaction with Saturn's magnetosphere (whose plasma corotates with Saturn's magnetic field, which rotates much more rapidly than the orbital motion of the G Ring). These tiny particles are steadily eroded away by further impacts and dispersed by plasma drag. Over the course of thousands of years the ring gradually loses mass, which is replenished by further impacts on Aegaeon. Methone Ring Arc A faint ring arc, first detected in September 2006, covering a longitudinal extent of about 10 degrees is associated with the moon Methone. The material in the arc is believed to represent dust ejected from