This temperature map of Saturn's moon Iapetus is constructed from
observations of Iapetus's infrared heat radiation taken with the Cassini
composite infrared spectrometer instrument during the Dec. 31, 2004 flyby.
The orange asterisk marks the point on Iapetus where the Sun is directly
overhead.
Temperatures reach nearly 130 Kelvin (-226 Fahrenheit) at noon on the
equator on the dark material that covers most of this side of Iapetus,
making high noon on Iapetus's dark side probably the warmest places in
the Saturn system. This is much warmer than temperatures on the moon
Phoebe measured by the composite infrared spectrometer in June 2004,
which peaked near 112 Kelvin (-258 Fahrenheit). That's because, although
Phoebe is almost as dark as Iapetus's dark material and absorbs nearly as
much sunlight, Phoebe rotates much more quickly (once every 9 hours,
compared to 79 days for Iapetus). That means the surface has less time to
heat up during the day. Temperatures on Iapetus' bright material are much
colder, peaking near 100 Kelvin (-280 Fahrenheit), both because the bright
material absorbs less sunlight and because it is further from the equator
on this side of Iapetus.
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 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 instrument team's home page,
http://cirs.gsfc.nasa.gov/..
