Scientists have long suspected that small moons hiding among Saturn's ring
strands might be producing some of the unusual structure observed in the F
ring. While the shepherd moon Prometheus is the main culprit behind the
strange behavior of Saturn's F ring, it cannot explain all observed
features. The current dilemma facing scientists is that Cassini is
detecting extended objects like those pictured here -- that may be either
solid moons or just loose clumps of particles within the ring.
This montage of four enhanced Cassini narrow-angle camera images shows
bright clump-like features at different locations within the F ring.
Two objects in particular, provisionally named S/2004 S3 and S/2004 S6,
have been repeatedly observed by Cassini over the past 13.5 months and
8.5 months, respectively. The orbits for these two objects have not yet
been precisely determined, in part because perturbations from other nearby
moons make the orbits of objects in this region complicated. Thus,
scientists cannot be completely confident at the present time if they in
fact have observed new sightings of S3 and S6, or additional transient
clumps.
The upper two images show features that may be S6. From previous
observations, S6 appears to have an orbit that crosses that of the main F
ring. This unexpected behavior currently is a subject of great interest to
ring scientists.
The upper left image was taken on June 21, 2005, and shows an object in
the outer ringlets of the F ring. The radial (or lengthwise) extent of the
feature is approximately 2,000 kilometers (1,200 miles). The radial
resolution on the ring is about 13 kilometers (8 miles) per pixel.
The image at the upper right was taken on June 29, 2005, and shows a
bright feature within the F ring's inner ringlets. The radial extent of
the feature seen here is about 2,000 kilometers (1,200 miles); the radial
resolution is 36 kilometers (22 miles).
The image at the lower left was taken on August 2, 2005, and shows a
feature that may be S3. S3 has been found to have an orbital path that is
tightly aligned with that of the main F ring. The radial resolution in the
image is 3.5 kilometers (2.2 miles) per pixel.
The lower right image was taken on April 13, 2005, and has a radial
resolution of 7 kilometers (4 miles) per pixel. This object does not
appear to be either S3 or S6.
Structures like knots and clumps within the F ring often are transient,
appearing and then disappearing within months. Repeated observation of the
objects seen in this region hopefully will give scientists firm evidence
about whether these features are actual moons that disturb the material
around them or perhaps the short-lived products of interactions between
the F ring and larger moons such as Prometheus.
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.
