This nighttime view of Saturn's north pole by the visual and infrared
mapping spectrometer on NASA's Cassini orbiter reveals a dynamic, active
planet at least 75 kilometers (47 miles) below the normal cloud tops seen
in visible light. Clearly revealed is the bizarre six-sided hexagon
feature present at the north pole.
This image is one of the first clear images of the north polar region ever
acquired from a unique polar perspective. In this image, the blue color
shows high-altitude emissions from atmospheric molecules excited by
charged particles smashing into the atmosphere along Saturn's powerful
magnetic field lines, producing the aurora at very high altitudes in
Saturn's atmosphere. The red color indicates the amount of 5-micron
wavelength radiation, or heat, generated in the depths of the warm
interior of Saturn that escapes the planet. Clouds blocking this light are
revealed as silhouettes against the background thermal glow of the planet.
This image is among the first to capture the entire hexagonal feature and
north polar region in one shot. It is also one of the first polar views
using Saturn's thermal glow at 5 microns (seven times the wavelength
visible to the human eye) as the light source. This allows polar cloud
features to be revealed during the persistent nighttime conditions under
way during north polar winter.
The hexagonal feature was originally discovered by NASA's Voyager
spacecraft in 1980, but those images and subsequent ground-based telescope
images suffered from poor viewing perspectives, which placed the feature
and the north pole at the extreme northern limb (edge) in those images.
The strong brightness of the hexagon feature indicates that it is
primarily a clearing in the clouds, which extends deep into the
atmosphere, at least down to the 3-bar (3-Earth atmospheres pressure)
level, about 75 kilometers (47 miles) below the clouds and hazes seen in
visible wavelengths. Thick clouds border both sides of the narrow feature,
as indicated by the adjacent dark lanes paralleling the bright hexagon.
This image and other images acquired over a 12-day period between Oct. 30
and Nov. 11, 2006, show that the feature is nearly stationary, and likely
is an unusually strong pole-encircling planetary wave that extends deep
into the atmosphere.
This image was acquired by the Cassini visual and infrared mapping
spectrometer on Oct. 29, 2006, from an average distance of 905,000
kilometers (562,340 miles) above the clouds.
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 was designed, developed and assembled at JPL. The Visual
and Infrared Mapping Spectrometer team is based at the University of
Arizona, where this image was produced.
For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov/home/index.cfm. The visual and infrared mapping
spectrometer team homepage is at http://wwwvims.lpl.arizona.edu.