PASADENA, Calif. — A movie taken by NASA's Cassini spacecraft reveals persistent storms near the poles of Jupiter, deepening the mystery of why the giant planet's weather systems are so stable, scientists said Monday.
The bands of storm clouds circling the region closer to Jupiter's equator, including the planet's ancient Great Red Spot, are one of Jupiter's most recognizable and enduring features.
Jupiter's polar regions, however, are mottled, suggesting a atmospheric swirl at the planet's higher latitudes reminiscent of the more chaotic weather familiar on Earth.
But the 1,200 images taken by Cassini over a period of 70 days late last year show that even Jupiter's polar storms — the spots that give the region its speckled appearance — turn out to be surprisingly long-lived and organized, scientists at California Institute of Technology said.
"The movie shows that the (storms) last a long time and move in organized patterns," Caltech scientist Ashwin Vasavada said. "You'd expect chaotic motions to go with the chaotic appearance, but that's not what we see."
Scientists said the movie shows thousands of Jovian storms the size of the biggest storms on Earth. The storms lasted throughout the more than two months they were being photographed and may rage for years to come, they said.
The images of thunderstorms swirling across the solar system's largest planet suggest that the massive storms, which can run for centuries, draw their energy from absorbing smaller systems.
Jupiter's famous Great Red Spot, visible with a telescope, is thought to be a 300-year-old thunderstorm packing 300-mph winds across an area three times as wide as Earth.
The images captured by Cassini, which packs a camera with filters that allow it to peer deep into Jupiter's cloud cover, show what appear to be smaller, white storms being created, absorbed by larger systems around the Red Spot and then torn apart as they stray into a shear zone created by pressure differentials.
Previous observations from the NASA's Galileo spacecraft, orbiting Jupiter since 1995, have suggested that smaller thunderstorms draw their power from below the cloudy surface of the hot, gassy planet.
Cassini, which passed within 6 million miles of Jupiter last December, has also collected evidence of a huge nebula of volcanic material surrounding the planet, scientists said. This has been spewed out by Io, one of its four largest moons, they said.
Launched in 1997, Cassini is now bound for Saturn, where it is scheduled to swing into orbit inside the outermost ring and dispatch a European-built, parachute-equipped probe to the planet's largest moon, Titan.
Haze-shrouded Titan is thought to have an atmosphere much like Earth's, but with clouds, rain and weather patterns produced by methane gas.
The main purpose of Cassini's approach to Jupiter was to give the 12,593-pound spacecraft a final gravitational push toward Saturn's orbit, where it is expected to arrive on July 1, 2004.