SPACE GEOSCIENCE ARTICLE
Bizarre hexagonal structure found on Saturn
entered by MIKE BALDWIN
media release by Carolina Martinez/Jane Platt; NASA Jet
Propulsion Laboratory
03.27.2007: Pasadena, CA: 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.
REFERENCE: Cassini Images Bizarre Hexagon on Saturn. Carolina
Martinez/Jane Platt. Media Relations Office, Jet Propulsion
Laboratory, California Institute of Technology, NASA,
Pasadena, California. March 27, 2007. Image courtesy of NASA.
This information is presented for educational purposes under
the provisions of the Fair Use Act of 1976.
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