Evidence from the visual and infrared mapping spectrometer on the Cassini
spacecraft indicates that the grain sizes in Saturn's rings grade from
smaller to larger, related to distance from Saturn. Those data (right)
are shown next to a corresponding picture of the rings taken by Cassini's
narrow angle camera.
Saturn's rings are thought to be made up of boulder-size snowballs. By
looking at the rings with the visual and infrared mapping spectrometer,
the size of the ice crystals, or grains, on the surfaces of those boulders
can be determined.
This visual and infrared mapping spectrometer has a spatial resolution
similar to that of the human eye, so it provides a view analogous to
standing on the spacecraft. Only instead of looking at the rings in
visible wavelengths, the instrument sees wavelengths beyond what human
eyes can see, ranging from the ultraviolet to the infrared.
The latest observations show that grain sizes range from very small, like
powdery snow on Earth, to larger grains, like more granular snow.
The visual and infrared mapping spectrometer can also see the fingerprint
signatures of chemical bonds, and, in this case, it spotted the bonds of
frozen water molecules. Saturn's rings are made mostly of water in the
form of ice. While this has been known for many years, the Cassini data
are showing that the ring ice is more pure than previously thought, with
the most pure ices generally being observed at increasing distances from
Saturn.
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 Cassini-Huygens mission for NASA's Office of Space
Science, Washington, D.C. The Cassini orbiter was designed, developed and
assembled at JPL. The visual and infrared mapping spectrometer team is
based at the University of Arizona, Tucson, Ariz.
For more information, about the Cassini-Huygens mission visit,
http://saturn.jpl.nasa.gov. For more information
about the visual and infrared mapping spectrometer visit
http://wwwvims.lpl.arizona.edu/.