A montage of maps of Saturn's moon Phoebe shows surface temperatures at
various times of day as determined by the composite infrared spectrometer
onboard Cassini during the June 11, 2004, Phoebe flyby. The asterisk on
each map shows the location of the subsolar point, where the Sun is
directly overhead. This point moves across the surface as Phoebe rotates.
It is morning in regions to the left of the subsolar point, and afternoon
in regions to the right. Like a newspaper weather map, different colors
indicate different temperatures, though Phoebe's temperatures are
distinctly cooler than even the coldest January day on Earth. Equatorial
temperatures peak in the early afternoon near 112 Kelvin (-257
Fahrenheit), plunging to 78 Kelvin (-319 Fahrenheit) before dawn, and
are even colder at higher latitudes. The large day/night temperature
contrasts imply that Phoebe's surface is covered in loose dust or ice
particles that store little heat and thus cool off rapidly at night.
Regions of Phoebe's surface that were not observed are shown in black.
Most of the maps show the effect on surface temperatures of the large
crater-like depression seen in Cassini's visible-wavelength images of
Phoebe, which is located just left of center in these maps. Crater walls
that are shadowed and cold in the early morning in the first map are
sunlit and warm in the late afternoon in the final map.
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 composite infrared spectrometer team is based at
NASA's Goddard Space Flight Center, Greenbelt, Md.
For more information, about the Cassini-Huygens mission visit,
http://saturn.jpl.nasa.gov and the Cassini imaging team home page,
http//cirs.gsfc.nasa.gov/.
