image of the moon Epimetheus

Photojournal: PIA06226

April 27, 2005

With this false-color view, Cassini presents the closest look yet at Saturn's small moon
Epimetheus (epp-ee-MEE-thee-uss).

The color of Epimetheus in this view appears to vary in a non-uniform way across the different
facets of the moon's irregular surface. Usually, color differences among planetary terrains
identify regional variations in the chemical composition of surface materials. However, surface
color variations can also be caused by wavelength-dependent differences in the way a particular
material reflects light at different lighting angles. The color variation in this false-color view
suggests such "photometric effects" because the surface appears to have a more bluish cast in
areas where sunlight strikes the surface at greater angles.

This false color view combines images obtained using filters sensitive to ultraviolet, polarized
green and infrared light. The images were taken at a Sun-Epimetheus-spacecraft, or phase, angle
of 115 degrees, thus part of the moon is in shadow to the right. This view shows an area seen
only very obliquely by NASA's Voyager spacecraft. The scene has been rotated so that north on
Epimetheus is up.

The slightly reddish feature in the lower left is a crater named Pollux. The large crater just below
center is Hilairea, which has a diameter of about 33 kilometers (21 miles).
At 116 kilometers (72 miles) across, Epimetheus is slightly smaller than its companion moon,
Janus (181 kilometers, or 113 miles across), which orbits at essentially the same distance from
Saturn.

The images for this color composite were obtained with the Cassini spacecraft narrow-angle
camera on March 30, 2005, at a distance of approximately 74,600 kilometers (46,350 miles)
from Epimetheus. Resolution in the original images was about 450 meters (1,480 feet) per pixel.
This view has been magnified by a factor of two to aid visibility.

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 .

Credit: NASA/JPL/Space Science Institute

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