The far left image shows the bright-dark boundary region on Saturn's moon
Iapetus at far-ultraviolet wavelengths, viewed by Cassini's ultraviolet
imaging spectrograph on Sept. 10, 2007.
These wavelengths represent reflected solar light and indicate where the
surface is brightest and highest in water ice abundance. (Red indicates
the brightest regions, purple the darkest.) The bright "Voyager
Mountains," part of the equatorial ridge, are seen as bright spots against
a dark background. The dark material that covers one hemisphere of Iapetus
is indicated in purple and is seen on the right side of this image.
The middle image is a color composite: blue-green (longer ultraviolet
wavelengths) indicates where the surface is bright and probably richest in
water ice. Red (short ultraviolet wavelengths) indicates where the surface
is low in water ice and relatively high in dirty material. The sky
background is also bright at these wavelengths, making the limb, or edge,
of Iapetus where the surface is dark indistinguishable from the sky
background.
The image on the right, taken by the imaging science subsystem, is for
reference, with the regions observed by Cassini's ultraviolet imaging
spectrometer outlined in red.
The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. NASA's 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 was designed, developed and assembled
at JPL. The ultraviolet imaging spectrograph was designed and built at,
and the team is based at the University of Colorado, Boulder. 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 ultraviolet imaging spectrograph
team home page is at http://lasp.colorado.edu/cassini. The Cassini imaging
team homepage is at http://ciclops.org.
