Cassini Images Bizarre Hexagon on Saturn
March 27, 2007, Source:
NASA Jet Propulsion Laboratory News
Pasadena, Calif. -- An odd, six-sided, honeycomb-shaped
feature circling the entire north pole of Saturn has
captured the interest of scientists with NASA's Cassini
mission.
NASA's Voyager 1 and 2 spacecraft imaged the feature
over two decades ago. The fact that it has appeared in
Cassini images indicates that it is a long-lived
feature. A second hexagon, significantly darker than the
brighter historical feature, is also visible in the
Cassini pictures. The spacecraft's visual and infrared
mapping spectrometer is the first instrument to capture
the entire hexagon feature in one image.
"This is a very strange feature, lying in a precise
geometric fashion with six nearly equally straight
sides," said Kevin Baines, atmospheric expert and member
of Cassini's visual and infrared mapping spectrometer
team at NASA's Jet Propulsion Laboratory, Pasadena,
Calif. "We've never seen anything like this on any other
planet. Indeed, Saturn's thick atmosphere where
circularly-shaped waves and convective cells dominate is
perhaps the last place you'd expect to see such a
six-sided geometric figure, yet there it is."
The hexagon is similar to Earth's polar vortex, which
has winds blowing in a circular pattern around the polar
region. On Saturn, the vortex has a hexagonal
rather than circular shape. The hexagon is nearly 25,000
kilometers (15,000 miles) across. Nearly four Earths
could fit inside it.
The new images taken in thermal-infrared light show the
hexagon extends much deeper down into the atmosphere
than previously expected, some 100 kilometers (60 miles)
below the cloud tops. A system of clouds lies within the
hexagon. The clouds appear to be whipping around the
hexagon like cars on a racetrack.
"It's amazing to see such striking differences on
opposite ends of Saturn's poles," said Bob Brown, team
leader of the Cassini visual and infrared mapping
spectrometer, University of Arizona, Tucson. "At the
south pole we have what appears to be a hurricane with a
giant eye, and at the north pole of Saturn we have this
geometric feature, which is completely different."
The Saturn north pole hexagon has not been visible to
Cassini's visual cameras, because it's winter in that
area, so the hexagon is under the cover of the long
polar night, which lasts about 15 years. The infrared
mapping spectrometer can image Saturn in both daytime
and nighttime conditions and see deep inside. It imaged
the feature with thermal wavelengths near 5 microns
(seven times the wavelength visible to the human eye)
during a 12-day period beginning on Oct. 30, 2006. As
winter wanes over the next two years, the feature may
become visible to the visual cameras.
Based on the new images and more information on the
depth of the feature, scientists think it is not linked
to Saturn's radio emissions or to auroral activity, as
once contemplated, even though Saturn's northern aurora
lies nearly overhead.
The hexagon appears to have remained fixed with Saturn's
rotation rate and axis since first glimpsed by Voyager
26 years ago. The actual rotation rate of Saturn is
still uncertain.
"Once we understand its dynamical nature, this
long-lived, deep-seated polar hexagon may give us a clue
to the true rotation rate of the deep atmosphere and
perhaps the interior," added Baines.
The hexagon images and movie, including the north polar
auroras are available at:
http://www.nasa.gov/cassini and
http://saturn.jpl.nasa.gov and
http://wwwvims.lpl.arizona.edu .
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 Science Mission
Directorate, Washington. The Cassini orbiter was
designed, developed and assembled at JPL. The Visual and
Infrared Mapping Spectrometer team is based at the
University of Arizona.
The Persistent Hexagon
August 25, 2008, Source:
NASA Cassini-Huygens Mission to Saturn
Saturn's north polar hexagon appears to be a
long-lived feature of the atmosphere, having been
spotted in images of Saturn in the early 1980s, again in
the 1990s, and then by the Cassini spacecraft in the
past several years.
The persistent nature of the hexagon in imaging
observations implies that it is present throughout
Saturn's 29-year seasonal cycle. Two sides of the
hexagon are seen here.
This view was obtained from about 67 degrees above the
equator. The image was taken with the Cassini spacecraft
wide-angle camera on Aug. 25, 2008 using a spectral
filter sensitive to wavelengths of infrared light
centered at 752 nanometers. The view was acquired at a
distance of approximately 566,000 kilometers (352,000
miles) from Saturn. Image scale is 31 kilometers (19
miles) per pixel.
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 imaging operations center is based at the Space
Science Institute in Boulder, Colo.
For more information about the Cassini-Huygens mission
visit
http://saturn.jpl.nasa.gov . The Cassini imaging
team homepage is at
http://ciclops.org .
Credit: NASA/JPL/Space Science Institute
Unveiling the Hexagon
February 20, 2009, Source:
NASA Cassini-Huygens Mission to Saturn
Saturn's north pole hexagon, seen here in an image from
the Cassini spacecraft, has been around for awhile. It
was seen in Voyager images in the early 1980s, in
ground-based telescopic images in the 1990s, and now
with Cassini.
More and more of this unusually shaped feature will be
revealed to Cassini's high resolution cameras as spring
slowly comes to the northern hemisphere in the planet's
29-year orbit.
The entire hexagon was imaged in thermal infrared by
Cassini in Oct. 2006 (see
above).
The image was taken with the Cassini spacecraft
wide-angle camera on Jan. 21, 2009 using a spectral
filter sensitive to wavelengths of near-infrared light
centered at 752 nanometers. The view was acquired at a
distance of approximately 930,000 kilometers (578,000
miles) from Saturn and at a Sun-Saturn-spacecraft, or
phase, angle of 54 degrees. Image scale is 52 kilometers
(32 miles) per pixel.
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 imaging operations center is based at the Space
Science Institute in Boulder, Colo.
For more information about the Cassini-Huygens mission
visit
http://saturn.jpl.nasa.gov . The Cassini imaging
team homepage is at
http://ciclops.org .
Credit: NASA/JPL/Space Science Institute
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