A quartet of Saturn's moons is seen here with the planet's F and A rings,
but something special is happening to the moon in the middle of this
Cassini image.
As Saturn approaches its August 2009 equinox, the planet's moons have been
casting shadows onto the rings (see PIA11651). Now the rings take a turn
casting a shadow on a moon. Tethys is the moon second from the left. The
northern part of this moon is darkened by a shadow cast by Saturn's A ring.
From left to right, the moons shown are Mimas (396 kilometers, or 246
miles across), Tethys (1062 kilometers, or 660 miles across), Rhea (1528
kilometers, or 949 miles across), and Pandora (81 kilometers, or 50 miles
across). Pandora is a tiny speck inside the rings.
This view looks toward the unilluminated side of the rings from about 1
degree above the ringplane. The rings and Pandora have been brightened
relative to the other moons to enhance visibility. The image was taken in
green light with the Cassini spacecraft wide-angle camera on April 11,
2009. The view was acquired at a distance of approximately 1.4 million
kilometers (870,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or
phase, angle of 21 degrees. Image scale on Tethys is about 82 kilometers
pixels 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.