The Cassini spacecraft is closing in fast on its first target of
observation in the Saturn system: the small, mysterious moon Phoebe,
only 220 kilometers (137 miles) across.
The three images shown here, the latest of which is twice as good as any
image returned by the Voyager 2 spacecraft in 1981, were captured in the
past week on approach to this outer moon of Saturn. Phoebe's surface is
already showing a great deal of contrast, most likely indicative of
topography, such as tall sunlit peaks and deep shadowy craters, as well
as genuine variation in the reflectivity of its surface materials. Left
to right, the three views were captured at a phase (Sun-Saturn-spacecraft)
angle of 87 degrees between June 4 and June 7, from distances ranging
from 4.1 million kilometers (2.6 million miles) to 2.5 million kilometers
(1.5 million miles). The image scale ranges from 25 to 15 kilometers per
pixel.
Phoebe rotates once every nine hours and 16 minutes; each of these images
shows a different region on Phoebe. Phoebe was the discovered in 1898. It
has a very dark surface.
Cassini's powerful cameras will provide the best-ever look at this moon
on Friday, June 11, when the spacecraft will streak past Phoebe at a
distance of only about 2,000 kilometers (1,240 miles) from the moon's
surface. The current images, and the presence of large craters, promise
a heavily cratered surface which will come into sharp view over the next
few days when image scales should get as small as a few tens of meters.
Phoebe orbits Saturn in a direction opposite to that of the larger
interior Saturnian moons. Because of its small size and retrograde orbit
Phoebe is believed to be a body from the distant outer solar system,
perhaps one of the building blocks of the outer planets that were
captured into orbit around Saturn. If true, the little moon will provide
information about these primitive pieces of material.
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 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 and the Cassini imaging team home page,
http://ciclops.org.