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PD0RDD > NASA 15.10.98 16:59l 117 Lines 5598 Bytes #-10039 (0) @ WW
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From: PD0RDD@PI8WNO.#UTR.NLD.EU
To : NASA@WW
Onderwerp: JUPITER'S "WHITE OVALS" TAKE SCIENTISTS BY STORM
Douglas Isbell
Headquarters, Washington, DC October 14, 1998
(Phone: 202/358-1753)
Jane Platt
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-5011)
RELEASE: 98-188
JUPITER'S "WHITE OVALS" TAKE SCIENTISTS BY STORM
As powerful hurricanes pummel coastal areas on Earth, NASA
space scientists are studying similar giant, swirling storms on
distant Jupiter that have combined to spawn a storm as large as
Earth itself.
Three separate cold storms, called "white ovals" because of
their color and egg shapes, have been observed in one band around
Jupiter's mid-section for half a century. Two of the storms
recently merged to form a larger white oval, according to
scientists studying data from NASA's Galileo spacecraft, the
Hubble Space Telescope, and the Agency's Infrared Telescope
Facility atop Mauna Kea, HI.
"The newly merged white oval is the strongest storm in our
Solar System, with the exception of Jupiter's 200-year-old 'Great
Red Spot' storm," according to Dr. Glenn Orton, senior research
scientist at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA.
"This may be the first time humans have ever observed such a large
interaction between two storm systems."
Each of the white ovals that merged were about two-thirds the
diameter of the Earth before the merger, when they combined to
form a feature as large as the Earth's disc. Although scientists
have observed the end result of the merger of the two white ovals,
the actual "collision" took place under cover of darkness while
Jupiter was turned away from view.
This new, powerful white oval has a mysterious trait,
according to Orton. "We can see it, along with the other white
ovals, at visible light and some infrared wavelengths, but we
cannot see the new white oval at certain infrared wavelengths that
peer underneath the storm's upper cloud layers," Orton said.
This might mean the storm is in a transition stage, undergoing a
rebirth after the merging of the two storms.
"With mature white ovals, we can see the upwelling of winds
in the center, which in turn leads to downwelling around it,"
Orton said. The new white oval has a very cold center (about -251
Fahrenheit or -157 Celsius) that is about one degree colder than
its surroundings. "Because of this, the oval may have generated a
thick cloud system which obscures the downwelling," Orton said,
which could explain the new oval's "disappearing act" at some
wavelengths.
Adding to the mystery is the fact that a nearby storm
rotating in the opposite direction to the new white oval used to
be warmer than its surrounding. "This probably means that the
feature contained mostly downwelling winds," said Orton. However,
Galileo's photopolarimeter radiometer instrument showed this
feature had cooled down to temperatures that were about the same
as its surroundings.
Orton suspects that this storm somehow lost power and is no
longer spinning as fast or downwelling as strongly as a year ago.
This storm was once positioned between the two smaller white ovals
that merged, and Orton theorized that when this storm system lost
power, it removed the buffering mechanism that kept the two
original white ovals apart.
Orton and his colleague, Dr. Brendan Fisher, a Caltech
postdoctoral fellow at JPL, based their conclusions about the
temperatures using data gathered by Galileo on July 20, 1998,
during the spacecraft's 17th orbit of Jupiter and its moons.
Although much data from the flyby of Europa in that time period
was lost because of a problem with the spacecraft's gyroscope,
Galileo's photopolarimeter radiometer gathered the new data on the
white ovals before the anomaly occurred.
The photopolarimeter radiometer measures temperature profiles
and energy balance of Jupiter's atmosphere, helping scientists
study the huge planet's cloud characteristics and composition.
Scientists believe that the bright, visible clouds of the white
ovals are composed of ammonia.
Galileo has been in orbit around Jupiter and its moons for 2
1/2 years, and is currently in the midst of a two-year mission
extension, known as the Galileo Europa Mission. JPL manages the
Galileo mission for NASA's Office of Space Science, Washington,
DC. JPL is a division of Caltech, Pasadena, CA.
Related images and information on the Galileo mission are
available on the Internet at the Galileo website:
http://www.jpl.nasa.gov/galileo
-end-
.
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