Half an hour after Prometheus tore into this region of Saturn's F ring,
the Cassini spacecraft snapped this image just as the moon was creating a
new streamer in the ring.The dark pattern shaped like an upside down check
mark in the lower left of the image is Prometheus and its shadow. The
potato shaped moon can just be seen coming back out of the ring.
The moon's handiwork also is apparent in two previous streamer-channel
formations on the right of the image. The darkest streamer-channel
stretching from the top right to the center of the image shows Prometheus'
previous apoapse passage about 15 hours earlier. A fainter, even earlier
channel extends to the edge of the image.
Prometheus (86 kilometers, or 53 miles across) dips into the inner edge of
the F ring when it reaches apoapse, the moon's farthest orbital point from
Saturn. At apoapse, the moon's gravity pulls particles of the ring outward
into a streamer.
As Prometheus moves onward toward periapse—its orbit's closest point
to the planet—the streamer gets longer. Then, as Prometheus moves
back toward apoapse, the streamer breaks apart which results in a dark
This streamer-channel cycle repeats once every orbit with the
streamer-channel features being streamers during Prometheus periapse and
channels during Prometheus apoapse.
The F ring is overexposed in this image which has been brightened to
reveal the moon.
This view looks toward the unilluminated side of the rings from about 18
degrees above the ringplane. The image was taken in visible light with the
Cassini spacecraft narrow-angle camera on Jan. 14, 2009. The view was
obtained at a distance of approximately 555,000 kilometers (345,000 miles)
from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 145
degrees. Image scale is 3 kilometers (2 miles) per pixel.
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 operations center is based at the Space
Science Institute in Boulder, Colo.
For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov/. The Cassini imaging team
homepage is at http://ciclops.org.