Dark material has coated the low-elevation terrain and the interiors of
craters in the southern portions of the quadrant on Iapetus that faces
away from Saturn. This is part of the boundary region separating the dark
leading and bright trailing hemispheres. The dark coating is thought to be
no more than a few tens of centimeters thick (10 centimeters equals 4
inches) and, as seen here, predominately appears on the northern-facing
walls of craters in the south.
Farther south, the dark splotches are less numerous and appear almost
absent at the highest latitudes (near the bottom of the frame). This is a
strong indicator that thermal effects play a role in the darkening process
of parts of Iapetus' surface: the colder the surface, the less common is
the dark terrain. As on Earth, the higher latitudes on Iapetus receive
less heating by sunlight.
At left, below center, the eastern rim of a great and ancient impact basin
can be seen. With a diameter of almost 500 kilometers (310 miles), it is
one of the largest impact structures on Iapetus, 1,468 kilometers (912
miles) across, and in the entire Saturn system.
This monochrome view shows terrain also seen in PIA08384 but at higher resolution.
The mosaic consists of three narrow-angle camera footprints across the
surface of Iapetus. This view is centered on terrain near 35.1 degrees
south latitude, 218.5 degrees west longitude. Image scale is approximately
231 meters (758 feet) per pixel.
The clear spectral filter images in this mosaic were obtained with the
Cassini spacecraft on Sept. 10, 2007, at a distance of approximately
40,000 kilometers (25,000 miles) from Iapetus and at a
sun-Iapetus-spacecraft, or phase, angle of 31 degrees.
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/home/index.cfm. The Cassini imaging
team homepage is at http://ciclops.org.
