Click on the image for movie
Part of the shadow of Saturn's moon Mimas appears as if it has been woven
through the planet's rings in this unusual series of images from Cassini.
Together, the sequence of frames comprise an unusual demonstration of the
varying particle density across the rings.
In these images, which were combined to create both a mosaic and a movie,
the Cassini spacecraft looks toward the unilluminated side of the rings
from about 61 degrees above the ringplane. Mimas' shadow, seen in multiple
locations simultaneously in the mosaic, lies across the inner B ring, C
ring and even the very faint D ring. The inner B ring is in the top left,
and the C ring is in the middle of the image. The transparent D ring is
faintly visible in the dark area in the lower right. Mimas is not shown.
The densest parts of the B and C rings, seen as bright stripes across
Mimas' shadow, do not let much sunlight pass through to the spacecraft's
camera. Consequently, one might expect these dense areas to appear dark
because they are on the dark side of the rings. But these areas,
particularly the inner B ring in the upper left of the image, appear
brightly lit, even where Mimas' shadow crosses them. It is likely that
illumination from Saturn itself and the subsequent reflection to the
cameras keeps them relatively bright. As a result, the moon's shadow
appears cut off and diminished in these areas.
Nineteen images, each taken about 2 minutes and 24 seconds apart, were
combined to create this mosaic and movie. Contiguous images were stitched
together to create a mosaic showing the whole swath of the rings across
which the moon's shadow passed. One image is missing from the sequence,
creating a gap in the movie.
The novel illumination geometry created as the Saturnian system approaches
equinox allows moons orbiting in or near the plane of Saturn's equatorial
rings to cast shadows onto the rings. These scenes are possible only
during the few months before and after Saturn's equinox which occurs only
once in about 15 Earth years. To see a similar image showing a different
moon's shadow on the unlit side of the rings, see PIA11498. To see movie
and mosaic of Mimas' shadow moving across the sunlit side of the rings,
see PIA11658.
These images have been processed, and the faint D ring was brightened
relative to the other rings. Background stars have been removed.
The image was taken in visible light with the Cassini spacecraft
narrow-angle camera on April 30, 2009. The view was obtained at a distance
of approximately 1.4 million kilometers (870,000 miles) from Saturn and at
a Sun-Saturn-spacecraft, or phase, angle of 73 degrees. Image scale is 8
kilometers (5 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.