MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Contact: Jane Platt
FOR IMMEDIATE RELEASEOctober 14, 1998
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
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 Earth. 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 at a
temperature of -157 C (-251 F), 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
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 California
Institute of Technology 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
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 extended
mission, 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.
Images and information on the Galileo mission are available
on the Internet at the Galileo website:
http://www.jpl.nasa.gov/galileo . The images are also available
at http://www.jpl.nasa.gov and