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Three enormous Jovian storms collided and merged
By Andrew Bridges
Pasadena Bureau Chief
posted: 11:27 am ET
24 October 2000
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jupiter_spots_001024 PASADENA, Calif. If you dont like the weather on Jupiter, wait 60 years.Thats how long it took the last of three enormous Jovian storms, each half the size of Earth, to collide and merge. The storms, called white ovals, formed in the gas giants atmosphere in 1939-40."After 60-year lifetimes, the three white ovals have all merged into one," said Agustin Sanchez-Lavega, an astronomer at the Universidad del Pais Vasco in Bilbao, Spain. 
Astronomers caught this view of two giant storms, each half the size of Earth, merging on Jupiter last year. Astronomers were lucky to catch the last two of the bunch in the act of merging this past March during a three-week collision that produced a single storm 7,400 miles (12,000 kilometers) across. Another similarly rare collision took place in 1998, but at a time when Jupiter was hidden behind the Sun from the view of astronomers. "We werent able to see how they came together that time," said Glenn Orton, a senior research scientist at NASAs Jet Propulsion Laboratory. This time, the oval resulting from the 1998 collision swirled toward the lone remaining storm of the original trio. Each storm was a swirling, high-pressure vortex, with winds spinning in a counterclockwise fashion at speeds of 290 miles (470 kilometers) per hour. As they approached, a third, darker oval temporarily formed between the two storms. As the three storms passed just southeast of Jupiters Great Red Spot in December 1999, the middle storm was torn apart, perhaps clearing the way for the merger between the white ovals later that spring."Usually, when weve seen two of them approaching each other, they bounce back away from each other," Orton said. Astronomers used telescopes at both Frances Pic-du-Midi and NASAs Infrared Telescope Facility in Hawaii, as well as the orbiting Hubble Space Telescope, to observe the merger.The Spanish, French and American team speculate that similar mergers in the past have contributed to the formation of Jupiters Great Red Spot. That storm twice as wide as Earth has persisted in Jupiters atmosphere for more than 300 years, or as long as astronomers have trained telescopes on the planet.Astronomers unveiled new images of Great Red Spot on Monday. The images, snapped by the Cassini spacecraft on October 8, show the planet from a distance of 48 million miles (78 million kilometers). The new images, seen here at left, include a panel showing Jupiter in three different wavelengths, including the ultraviolet and near infrared.The $3 billion Cassini spacecraft will pass within 6 million miles (10 million kilometers) of Jupiter on December 30 while en route to its 2004 encounter with Saturn.The new images, including of the merged white ovals, were presented on Monday at the 32nd annual meeting of the American Astronomical Societys Division of Planetary Sciences, held in Pasadena, California. The meeting, which lasts through Friday, is among the worlds largest gathering of planetary scientists, with nearly 600 talks and posters being presented.
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