Obscuring Janus (GIF-Movie; credits: NASA/JPL/Space Science Institute)

Caption NASA:"Sunlight passing through the Cassini Division between Saturn's "A" and "B" Rings sweeps across and illuminates the surface of the moon Janus in this movie captured shortly after Saturn's August 2009 Equinox.

The novel illumination geometry that accompanied Equinox lowered the Sun's Angle to the Ring-Plane, significantly darkened the Rings, caused out-of-plane structures to look anomalously bright and threw shadows across the Rings. As this movie shows, the Equinox period also allowed the Rings to cast shadows on the moons. These scenes were possible only during the few months before and after Saturn's Equinox, which occurs only once in about 15 Earth years. Before and after Equinox, cameras on NASA's Cassini Spacecraft spotted not only the predictable shadows of some of Saturn's moons, but also the shadows of newly revealed Vertical Structures in the Rings themselves (see PIA11665).

This view looks toward the Trailing Hemisphere of Janus (approx. 179 Km, or about 111 miles across). North on Janus is up and rotated 8° to the right.

The movie is a concatenation of 12 still images. The images were obtained in Visible Light with Cassini's narrow-angle camera on Aug. 27, 2009. The view was acquired at a distance of approx. 268.000 Km (about 67.000 miles) from Janus and at a Sun-Janus-Spacecraft, or Phase, Angle of 25°.
Image scale is roughly 2 Km (5271 feet) per pixel".