Long Shadows

Description
Every fifteen and one-quarter earth years, during the few months to a year bracketing the saturnian equinoxes, the moons in and near the rings cast shadows across the rings. Because of differences in orbital inclination and diameter, different moons cast shadows on the rings over different spans of time. The spans mostly bracket the equinox, but start and end times are usually nested (the one that starts first ends last, etc.). The time a particular satellite casts a shadow is named for it (Atlas Long Shadows, Mimas Long Shadows, etc.).

Traditionally, the first shadow sighted is named "First Shadow," and starts Long Shadows, and the last one to disappear ends it. Most observers, however, officially reckon the start and end times to the nearest day/year. Shadow Types


 * Spindles—Cast by high-inclination moons outside the ring radius such as Epimetheus, these shadows are entirely contained within the rings, and have a fat, blunt-ended shape.
 * Needles—Cast by low-inclination moons inside the rings such as Atlas, these shadows taper more gradually.

Cultural Significance
This is a significant time for the saturnites. For both the Enceladus and Titan polar dwellers, it marks when the days start getting longer than the nights and vice versa, leading to a year or so of dark or light. Because of its extensive cloud cover and greater distance from Saturn, this is not as significant on Titan.

Although this time has been observed since soon after Arrival, it has become significant only relatively recently (in the last generation or two) when scoop miners began harvesting ring dust; up until then no one was in a position to see the shadows directly, and the time was an abstraction. None of the habs or tether stations co-orbital with Enceladus were inclined enough to Enceladus to make the rings' surface visible.

Links

 * Moon Shadow in Motion, taken by Cassini on March 23, 2009.
 * Atlas ring shadow, taken by Cassini on 5th August 2009.
 * Multiple exposures of a ring shadow cast by Mimas, taken by Cassini on August 5, 2009.