Giant Cyclones at Saturn's Poles Create a Swirl of Mystery

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
Carolina.Martinez@jpl.nasa.gov

IMAGE ADVISORY: 2008-192 Oct. 13, 2008

Giant Cyclones at Saturn's Poles Create a Swirl of Mystery

New images from NASA's Cassini spacecraft reveal a giant cyclone at Saturn's north pole, and
show that a similarly monstrous cyclone churning at Saturn's south pole is powered by Earth-like
storm patterns.

The new-found cyclone at Saturn's north pole is only visible in the near-infrared wavelengths
because the north pole is in winter, thus in darkness to visible-light cameras. At these
wavelengths, about seven times greater than light seen by the human eye, the clouds deep inside
Saturn's atmosphere are seen in silhouette against the background glow of Saturn's internal heat.

The entire north pole of Saturn is now mapped in detail in infrared, with features as small as 120
kilometers (75 miles) visible in the images. Time-lapse movies of the clouds circling the north
pole show the whirlpool-like cyclone there is rotating at 530 kilometers per hour (325 miles per
hour), more than twice as fast as the highest winds measured in cyclonic features on Earth. This
cyclone is surrounded by an odd, honeycombed-shaped hexagon, which itself does not seem to
move while the clouds within it whip around at high speeds, also greater than 500 kilometers per
hour (300 miles per hour). Oddly, neither the fast-moving clouds inside the hexagon nor this
new cyclone seem to disrupt the six-sided hexagon.

New Cassini imagery of Saturn's south pole shows complementary aspects of the region through
the eyes of two different instruments. Near-infrared images from the visual and infrared
mapping spectrometer instrument show the whole region is pockmarked with storms, while the
imaging cameras show close-up details.

The new views are available online at: http://www.nasa.gov/cassini and
http://saturn.jpl.nasa.gov.

Unlike Earth-bound hurricanes, powered by the ocean's heat and water, Saturn's cyclones have
no body of water at their bases, yet the eye-walls of Saturn's and Earth's storms look strikingly
similar. Saturn's hurricanes are locked to the planet's poles, whereas terrestrial hurricanes drift
across the ocean.

"These are truly massive cyclones, hundreds of times stronger than the most giant hurricanes on
Earth," said Kevin Baines, Cassini scientist on the visual and infrared mapping spectrometer at
NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Dozens of puffy, convectively formed
cumulus clouds swirl around both poles, betraying the presence of giant thunderstorms lurking
beneath. Thunderstorms are the likely engine for these giant weather systems," said Baines.

Just as condensing water in clouds on Earth powers hurricane vortices, the heat released from the
condensing water in Saturnian thunderstorms deep down in the atmosphere may be the primary
power source energizing the vortex.

In the south, the new infrared images of the pole, under the daylight conditions of southern
summer, show the entire region is marked by hundreds of dark cloud spots. The clouds, like
those at the north pole, are likely a manifestation of convective, thunderstorm-like processes
extending some 100 kilometers (62 miles) below the clouds. They are likely composed of
ammonium hydrosulfide with possibly a mixture of materials dredged up from the depths. By
contrast, most of the hazes and clouds seen on Saturn are thought to be composed of ammonia,
which condenses at high, visible altitudes.

Complementary images of the south pole from Cassini's imaging cameras, obtained in mid-July,
are 10 times more detailed than any seen before. "What looked like puffy clouds in lower
resolution images are turning out to be deep convective structures seen through the atmospheric
haze," said Cassini imaging team member Tony DelGenio of NASA's Goddard Institute for
Space Studies in New York. "One of them has punched through to a higher altitude and created
its own little vortex."

The "eye" of the vortex is surrounded by an outer ring of high clouds. The new images also hint
at an inner ring of clouds about half the diameter of the main ring, and so the actual clear "eye"
region is smaller than it appears in earlier low-resolution images.

"It's like seeing into the eye of a hurricane," said Andrew Ingersoll, a member of Cassini's
imaging team at the California Institute of Technology, Pasadena. "It's surprising. Convection is
an important part of the planet's energy budget because the warm upwelling air carries heat from
the interior. In a terrestrial hurricane, the convection occurs in the eyewall; the eye is a region of
downwelling. Here convection seems to occur in the eye as well."

Further observations are planned to see how the features at both poles evolve as the seasons
change from southern summer to fall in August 2009.

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.
The imaging team is based at the Space Science Institute, Boulder, Colo.

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