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FOR IMMEDIATE RELEASE
October 23, 2000
GIANT STORMS COLLIDE ON JUPITER
For the first time, scientists have been able to watch the
process of two of Jupiter's giant "white oval" storms, each about
half the size of Earth, colliding and merging to form an even
"Usually when we've seen two of them approaching each other,
they bounce back away from each other," said Dr. Glenn Orton,
senior research scientist at NASA's Jet Propulsion Laboratory,
Pasadena, Calif., and member of a team of Spanish, French and
American astronomers that used NASA's Hubble Space Telescope and
ground-based telescopes to study the ovals this year. Dr. Agustin
Sanchez-Lavega, an astronomer at Universidad del Pais Vasco,
Bilbao, Spain, reported the team's observations today at the
meeting of the American Astronomical Society's Division of
Planetary Sciences in Pasadena.
An image of the storms before and after merging is available at
The researchers speculate that a similar merger took place
centuries ago and may have built Jupiter's famous Great Red Spot,
a storm that is twice as wide as the Earth and has persisted in
Jupiter's southern hemisphere for more than 300 years.
Seeing the collision of two storms will help scientists
understand more about the dynamics of Jupiter's atmosphere,
Sanchez-Lavega said. One question has been how deeply the roots
of a storm at Jupiter's cloud tops extend into lower layers. In
this year's merger, the upper layer seemed to move differently
than underlying clouds.
Three white oval storms, in a band of Jupiter's atmosphere
farther south than the Great Red Spot, became active about 60
years ago. In the following decades until 1998, they sometimes
approached each other but never collided. In early 1998, two of
the ovals were approaching each other as Jupiter went out of
sight from Earth, behind the Sun. When the planet came back into
view, the two had become one.
"We weren't able to see how they came together that time,"
Last year, the oval resulting from the 1998 combination
approached the remaining one of the original three ovals. Each
was a swirling high-pressure vortex, upwelling at the center and
spinning winds counterclockwise to about 470 kilometers per hour
(290 miles per hour). One was about 9,000 kilometers (about 5,600
miles) across, the other slightly smaller.
A third, darker oval, swirling clockwise instead of
counterclockwise, formed temporarily between the two white ovals.
That type of interceding system may be what usually keeps white
ovals from colliding, the team proposed. But in this case, the
middle storm appears to have been pushed even farther south and
torn apart as all three passed near the Great Red Spot last
The disappearance of the opposite-swirling storm from
between them cleared the way for the two white ovals to meet.
Their collision dance began in March and lasted about three
weeks. At the cloud tops, the storms circled around each other
counterclockwise, then consolidated into a single oval about one-
third wider than either of the ovals had been beforehand. In
deeper clouds, the interaction did not include the storms
circling each other, but it did produce complex cloud structures
from stretching and contracting of the ovals and went through an
intermediate phase as a single oval with a double nucleus.
The ovals' approach and merger was viewed in various
wavelengths, showing events at different depths, with a planetary
telescope at Pic-du-Midi in France, NASA's Infrared Telescope
Facility in Hawaii, and the orbiting Hubble Space Telescope, a
facility of NASA and the European Space Agency.
JPL is managed for NASA by the California Institute of
The Hubble Space Telescope is a facility of NASA and the European
Space Agency. It is operated by the Space Telescope Science
Institute, Baltimore, Md., which is managed for NASA by the
Association of Universities for Research in Astronomy in