The cold, cratered landscape of Saturn's moon Tethys shines in stark
relief in this crescent view.
Aside from its obvious aesthetic beauty, this particular Cassini mosaic
was obtained mainly to understand important details about how the surface
of Tethys (1,071 kilometers, or 665 miles across) reflects light at high
phase angles (the sun-Tethys-spacecraft viewing angle). The beautiful
interplay of light with surface topographic features is an important
factor in this regard. The surface is heavily cratered, and at this
oblique angle the craters give the surface a highly scalloped appearance.
Unlike some high-resolution crescent views of Saturn's moons, this image
truly gives Tethys the appearance of being composed of ice and frost.
There appear to be numerous sun glints sparkling across the surface. Some
of these might be specular (or mirror-like) reflections off of exposed
walls of solid ice inside craters, or they might be uniformly large,
frosty or icy-particle covered facets of topography that are so oriented
as to give exceptionally bright but diffuse reflections.
The shadows cast by most craters in the scene are not dark, but rather,
they are illuminated by light bouncing off of their sunlit walls and those
of other craters. This light, which has been scattered multiple times,
makes visible some details along the shadowed walls and floors of craters
that would not otherwise be visible in this viewing geometry.
This mosaic was assembled from four clear filter, narrow-angle camera
images, with low resolution, wide-angle camera data filling a small gap in
coverage. The view is an orthographic projection and has a resolution of
211 meters (692 feet) per pixel. An orthographic view is most like the
view seen by a distant observer looking through a telescope. North is up.
The view was obtained by the Cassini spacecraft on June 29, 2007, from a
distance of approximately 38,000 kilometers (24,000 miles) and at a
Sun-Tethys-spacecraft, or phase, angle of 152 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.
