Hot Cyclones Churn at Both Ends of Saturn
- From: baalke@xxxxxxxxxxxxx
- Date: Thu, 3 Jan 2008 17:50:16 -0800 (PST)
http://www.jpl.nasa.gov/news/news.cfm?release=2008-001
Hot Cyclones Churn at Both Ends of Saturn
Jet Propulsion Laboratory
January 03, 2008
Despite more than a decade of winter darkness, Saturn's north pole is
home to an unexpected hot spot remarkably similar to one at the
planet's
sunny south pole. The source of its heat is a mystery. Now, the first
detailed views of the gas giant's high latitudes from the Cassini
spacecraft reveal a matched set of hot cyclonic vortices, one at each
pole.
While scientists already knew about the hot spot at Saturn's south
pole
from previous observations by the W. M. Keck Observatory in Hawaii,
the
north pole vortex was a surprise. The researchers report their
findings
in the Jan. 4 issue of Science.
"We had speculated that the south pole hot spot was connected to the
southern, sunlit conditions," said Glenn Orton, a senior research
scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and
co-investigator on Cassini's composite infrared spectrometer. "Since
the
north pole has been deprived of sunlight since the arrival of winter
in
1995, we didn't expect to find a similar feature there."
The infrared data show that the shadowed north pole vortex shares much
the same structure and temperature as the one at the sunny south pole.
The cores of both show a depletion of phospine gas, an imbalance
probably caused by air moving downward into the lowest part of
Saturn's
atmosphere, the troposphere. Both polar vortices appear to be
long-lasting and intrinsic parts of Saturn and are not related to the
amount of sunlight received by one pole or the other.
"The hot spots are the result of air moving polewards, being
compressed
and heated up as it descends over the poles into the depths of
Saturn,"
said Leigh Fletcher, a planetary scientist from the University of
Oxford, England, and the lead author of the Science paper. "The
driving
forces behind the motion, and indeed the global motion of Saturn's
atmosphere, still need to be understood."
Though similar, the two polar regions differ in one striking way. At
the north pole, the newly discovered vortex is framed by the
distinctive, long-lived and still unexplained polar hexagon. This
mysterious feature encompassing the entire north pole was first
spotted
in the 1980s by NASA's Voyager 1 and 2 spacecraft. Cassini's infrared
cameras also detected the hexagon in deep atmospheric clouds early in
2007.
In their paper, Fletcher and his colleagues report that the bright,
warm
hexagon is much higher than previous studies had shown. "It extends
right to the top of the troposphere," says Fletcher. "It is associated
with downward motion in the troposphere, though the cause of the
hexagonal structure requires further study."
Winter lasts about 15 years on Saturn. Researchers anticipate that
when
the seasons change in the coming years and Saturn's north pole is once
again in sunlight, they will be able to see a swirling vortex with
high
eye walls and dark central clouds like the one now visible at the
south
pole. "But Saturn may surprise us again," says Fletcher.
"The fact that Neptune shows a similar south polar hot spot whets our
appetite for the strange dynamics of the poles of the other gas
giants,"
Fletcher says.
More information about Jupiter's poles will come from NASA's Juno
mission, currently scheduled for launch in 2011 and arrival in 2016.
Fletcher's research was funded by the United Kingdom's Science and
Technology Facilities Council.
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. JPL, 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 science team for Cassini's composite infrared spectrometer
team
is based at NASA's Goddard Space Flight Center, Greenbelt, Md.
------------------------------------------------------------------------
Media contacts: Rosemary Sullivant/Carolina Martinez 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
2008-001
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