This map of Saturn's F ring illustrates how the ghostly strands flanking
the core of this contorted ring, when examined in detail, actually form a
spiral structure wound like a spring around the planet.
Two identical maps of the F ring have been joined, side-by-side, to show
the nature of the spiral more clearly. The F ring has been mapped as if it
were a circular feature, so that its eccentricity is not apparent here.
The spiral strand's path across the image begins about 350 kilometers
(217 miles) inward of the F ring core at about 200 degrees longitude
(bottom axis) on the right map, and moves closer to the ring core toward
the left, wrapping over onto the map on the left. The strand appears to
cross the ring core around 100 degrees longitude, after which the distance
between the strand and the ring core increases to the left and can be
followed, moving even farther outward, wrapping around to the rightmost
boundary of the right-hand map and continuing to the left.
Other spiraling structures seen in the main rings of Saturn, the density
and bending waves, are initiated by the gravitational influence of an
orbiting moon. Density and bending waves move across the rings because of
the way that relatively massive ring particles exert a gravitational
influence on each other and can all move together.
In contrast, the F ring spiral structure contains very little mass and
appears to originate from material somehow episodically ejected from the
core of the F ring and then sheared out due to the different orbital
speeds followed by the constituent particles.
Scientists have speculated that the spiral may be a consequence of moons
crossing the F ring and spreading its particles around.
The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory,
a division of the California Institute of Technology in Pasadena, manages
the mission for NASA's Science Mission Directorate, Washington, D.C. The
Cassini orbiter was designed, developed and assembled at JPL.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov.
For additional images visit the Cassini imaging team homepage http://ciclops.org.