Storms Converging on Jupiter

June 12, 2006 — Residents already on alert for the 2006 Atlantic hurricane season can feel grateful about one thing: They are not living on Jupiter, where the two largest storms in the solar system are about to converge.

The Great Red Spot, a massive storm twice as wide as Earth, and a second storm half as big are racing toward each other under full view of professional and amateur astronomers on Earth.

Both storms have winds estimated at about 350 mph -- more than twice as powerful as Category Five hurricanes on Earth.

"Any one of these at any time would be way worse than Katrina," said Glenn Orton, with NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Scientists do not know what will happen when the storms' outer bands pass close by each other. Their closest approach will occur on July 4.

Researchers are curious to see if the smaller storm, which once appeared white, will lose its reddish hue. Earlier this year, astronomers noticed that a red vortex had formed inside the storm, a possible sign that the storm had strengthened.

"Is it going to lose spin? Is it going to drop below the threshold of whatever was happening to make particles change color?" Orton said.

Scientists are not sure why Jupiter's great storm is red in the first place. Some suspect the storm sucks material from deep inside the planet's atmosphere and tosses it above the highest clouds where ultraviolet radiation from the sun strikes the particles and turns them red.

The Great Red Spot has been churning for hundreds of years.

"We really don't know what causes colors on Jupiter's clouds," said Orton, who has been using the Hubble Space Telescope to watch the storms approach each other. "We'd like to know why things are so different on Jupiter and what implications that has for understanding Earth."

Orton and his colleague, Amy Simon-Miller at the Goddard Space Flight Center in Greenbelt, Md., expect the smaller storm, known as Oval BA, to weaken once it bumps up against its big sister.

"We believe the Great Red Spot will push Oval BA toward a southern jet stream, which is blowing against the oval's counterclockwise rotation," said Simon-Miller.

The encounter could slow Oval BA's spin and possibly reverse the process that made it turn red.

Amateur astronomers first noticed the gap closing between the two storms and notified NASA, said Orton. Jupiter is clearly visible in the evening sky. It can be founded about halfway up in the southeastern sky at sunset.