Cassini's celestial sleuthing has paid off with this time-lapse series of
images which confirmed earlier suspicions that a small moon was orbiting
within the narrow Keeler gap of Saturn's rings.
The movie sequence, which consists of 12 images taken over 16 minutes
while Cassini gazed down upon the sunlit side of the A ring, shows a tiny
moon orbiting in the center of the Keeler gap, churning up waves in the
gap edges as it goes. The pattern of waves travels with the moon in
its orbit.
The Keeler gap is located about 250 kilometers (155 miles) inside the
outer edge of the A ring, which is also the outer edge of the bright main
rings. The new object is about 7 kilometers across (4 miles) and reflects
about 50 percent of the sunlight that falls upon it -- a brightness that
is typical of particles in the nearby rings.
The new body has been provisionally named S/2005 S1.
Imaging scientists predicted the moon's presence and its orbital distance
from Saturn after July 2004, when they saw a set of peculiar spiky and
wispy features in the Keeler gap's outer edge. The similarities of the
Keeler gap features to those noted in Saturn's F ring and the Encke gap
led the scientists to conclude that a small body, a few kilometers across,
was lurking in the center of the Keeler gap, awaiting discovery.
Also included here is a view of the same scene created by combining six
individual, unmagnified frames used in the movie sequence. This digital
composite view improves the overall resolution of the scene compared to
that available in any of the single images.
The images in this movie sequence were obtained with the Cassini
spacecraft narrow-angle camera on May 1, 2005, at a distance of
approximately 1.1 million kilometers (708,000 miles) from Saturn.
Resolution in the original image was 8 kilometers (5 miles) per pixel.
The images in the movie sequence have been magnified in (the vertical
direction only) by a factor of two to aid visibility of features caused
within the gap by the moonlet.
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 and its two onboard cameras were designed, developed and
assembled at JPL. The imaging team is based at the Space Science
Institute, Boulder, Colo.
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.
