This nighttime view of Saturn's north pole by the visual and infrared
mapping spectrometer onboard NASA's Cassini orbiter clearly shows a
bizarre six-sided hexagon feature encircling the entire north pole. This
is one of the first clear images taken of the north polar region ever
acquired from a unique polar perspective.
In this image, the red color indicates the amount of 5-micron wavelength
radiation, or heat, generated in the warm interior of Saturn that escapes
the planet. Clouds near 3-bar (about 100 kilometers or 62 miles deeper
than seen in visible wavelengths) block the light, revealing them in
silhouette against the background thermal glow of Saturn. The bluish color
shows sunlight striking the far limb (edge) of the planet, showing that
the entire north pole is under the nighttime conditions characteristic of
polar winter, as on Earth.
This image is the first to capture the entire feature and north polar
region in one shot, and is also the first polar view using Saturn's
thermal glow at 5 microns (seven times the wavelength visible to the human
eye) as the light source. This allows the pole to be revealed during the
persistent nighttime conditions under way during winter. The hexagon
feature was originally discovered by NASA's Voyager spacecraft in 1980,
but those historic 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.
In the new infrared 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 some 75 kilometers (47 miles)
underneath the typical upper hazes and clouds seen in the daytime imagery
by Voyager. Thick clouds border both sides of the narrow feature, as
indicated by the adjacent dark lanes paralleling the bright hexagon. This
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 with the Cassini visual and infrared mapping
spectrometer on Oct. 30, 2006, from an average distance of 1.3 million
kilometers (807,782 miles).
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.