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This colorful view from NASA's Cassini mission is
the highest-resolution view of the unique six-sided jet stream at Saturn's north
pole known as "the hexagon."
Image Credit: NASA/JPL-Caltech/SSI/Hampton
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This infrared movie from NASA's Cassini mission
shows the churning of the curious six-sided jet stream at Saturn's north pole
known as "the hexagon."
Image Credit: NASA/JPL-Caltech/University of
Arizona
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This black-and-white movie from NASA's Cassini
mission shows a polar projection of the curious six-sided jet stream at Saturn's
north pole known as "the hexagon" in the infrared.
Image Credit: NASA/JPL-Caltech/University of
Arizona
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NASA's Cassini spacecraft has obtained the highest-resolution movie yet of a
unique six-sided jet stream, known as the hexagon, around Saturn's north
pole.
This is the first hexagon movie of its kind, using color filters, and the
first to show a complete view of the top of Saturn down to about 70 degrees
latitude. Spanning about 20,000 miles (30,000 kilometers) across, the hexagon is
a wavy jet stream of 200-mile-per-hour winds (about 322 kilometers per hour)
with a massive, rotating storm at the center. There is no weather feature
exactly, consistently like this anywhere else in the solar system.
"The hexagon is just a current of air, and weather features out there that
share similarities to this are notoriously turbulent and unstable," said Andrew
Ingersoll, a Cassini imaging team member at the California Institute of
Technology in Pasadena. "A hurricane on Earth typically lasts a week, but this
has been here for decades -- and who knows -- maybe centuries."
Weather patterns on Earth are interrupted when they encounter friction from
landforms or ice caps. Scientists suspect the stability of the hexagon has
something to do with the lack of solid landforms on Saturn, which is essentially
a giant ball of gas.
Better views of the hexagon are available now because the sun began to
illuminate its interior in late 2012. Cassini captured images of the hexagon
over a 10-hour time span with high-resolution cameras, giving scientists a good
look at the motion of cloud structures within.
They saw the storm around the pole, as well as small vortices rotating in the
opposite direction of the hexagon. Some of the vortices are swept along with the
jet stream as if on a racetrack. The largest of these vortices spans about 2,200
miles (3,500 kilometers), or about twice the size of the largest hurricane
recorded on Earth.
Scientists analyzed these images in false color, a rendering method that
makes it easier to distinguish differences among the types of particles
suspended in the atmosphere -- relatively small particles that make up haze --
inside and outside the hexagon.
"Inside the hexagon, there are fewer large haze particles and a concentration
of small haze particles, while outside the hexagon, the opposite is true," said
Kunio Sayanagi, a Cassini imaging team associate at Hampton University in
Virginia. "The hexagonal jet stream is acting like a barrier, which results in
something like Earth's Antarctic ozone hole."
The Antarctic ozone hole forms within a region enclosed by a jet stream with
similarities to the hexagon. Wintertime conditions enable ozone-destroying
chemical processes to occur, and the jet stream prevents a resupply of ozone
from the outside. At Saturn, large aerosols cannot cross into the hexagonal jet
stream from outside, and large aerosol particles are created when sunlight
shines on the atmosphere. Only recently, with the start of Saturn's northern
spring in August 2009, did sunlight begin bathing the planet's northern
hemisphere.
"As we approach Saturn's summer solstice in 2017, lighting conditions over
its north pole will improve, and we are excited to track the changes that occur
both inside and outside the hexagon boundary," said Scott Edgington, Cassini
deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena,
Calif.
A black-and-white version of the imaging camera movie and movies obtained by
Cassini's visual and infrared mapping spectrometer are also tools Cassini
scientists can use to look at wind speeds and the mini-storms inside the jet
stream.
Cassini launched in 1997 and arrived at Saturn on July 1, 2004. Its mission
is scheduled to end in September 2017. The Cassini-Huygens mission is a
cooperative project of NASA, the European Space Agency and the Italian Space
Agency. JPL manages the mission for NASA's Science Mission Directorate in
Washington. JPL designed, developed and assembled the Cassini orbiter and its
two onboard cameras. The imaging team is based at the Space Science Institute,
Boulder, Colo.
A Google+ Hangout to discuss these results and other Cassini images will take
place today at 12:30 p.m. PST (3:30 p.m. EST):
The event will be broadcast live on NASA Television and streamed on the
agency’s website. For information on NASA TV, visit:
The event will also be streamed live on Ustream with a moderated chat
available at:
Questions can be asked on the Google Hangout event page, in the chat box on
the Ustream site and via Twitter using the hashtag #askCassini.
More information about Cassini is available at:
and
NASA
Guillermo Gonzalo Sánchez Achutegui
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