The Cassini spacecraft recently flew through the plane of Saturn’s rings and took this straight-on image of the G ring, showing a bright arc of material seen here as it rounds the ring’s edge, or ansa. The spacecraft also took images of the moons Mimas and Calypso (see below). In the image here, the diffuse glow at left shows the extended nature of this faint ring. The view looks toward the sunlit side of the rings from less than a degree below the ringplane. The ring moved against the background stars during this exposure, creating the star trails seen here. Cassini scientists and engineers are preparing for an upcoming flyby of the moon Enceladus on October 9. This is the second of seven targeted Enceladus fly-bys in the Extended Mission., and the spacecraft will pass through the moon’s geyser-like plumes in an attempt to measure fields and particles.
Cassini spacecraft scientists think the bright arc in the G Ring contains relatively large, icy particles held in place by a gravitational an orbital resonance with the moon Mimas. Micrometeoroids collide with the large particles, releasing smaller, dust-sized particles that brighten the arc. The plasma in the giant planet’s magnetic field sweeps through this arc continually, dragging out the fine particles and creating the G ring. The ring arc orbits Saturn along the inner edge of the G ring. The image was taken with the Cassini spacecraft narrow-angle camera on Aug. 22, 2008, from about 1.2 million kilometers (740,000 miles) from Saturn.
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And one of Calypso, too: