Colors Change on Jupiter as Planet’s Weather Does ‘Wild Things’ With PM-Space Shuttle, Bjt
PASADENA, Calif. (AP) _ Jupiter’s Great Red Spot is getting redder following a color change by a 6,200-mile-wide belt of clouds, scientists said as NASA prepares for the Galileo’s six-year mission to the planet.
″This is a dynamical, neat place to look at. It’s changing and doing wild things on a huge scale,″ said Rita Beebe, an astronomer at New Mexico State University.
British astronomer G.M. Hurst on July 16 first noticed that Jupiter’s 6,200-mile-wide Southern Equatorial Belt was changing from brown to white.
Since then, the Great Red Spot - a hurricane almost twice Earth’s size that faded to dim grey in 1976 - has been returning gradually to its brick red color, Beebe said Tuesday by phone from Las Cruces, N.M.
″The Red Spot appears to be darkening. Color seems to be coming back,″ said Stephen O’Meara, an associate editor at Sky & Telescope magazine in Cambridge, Mass. ″Some observe it as orange; some pink. It has a pale luster.″
The National Aeronautics and Space Administration had hoped to launch space shuttle Atlantis on Thursday carrying the Galileo probe into Earth orbit, where it will be deployed on its flight to Jupiter. But the agency late Tuesday delayed the launch at least until at least Monday because of a computer problem aboard the shuttle.
Scientists study weather on Jupiter and other planets to understand Earth’s climate and rules governing weather on planets, said Beebe, who watches Jupiter using a 24-inch telescope at her university’s Tortugas Mountain Observatory near Las Cruces.
Galileo will examine Jupiter’s vast storms and jetstream-like belts when it arrives in 1995 at the solar system’s largest planet, which is 11 times wider than Earth and 318 times heavier.
The Great Red Spot, which is at least 350 years old and measures about 12,400 miles east to west and 6,200 miles north to south, is continuing to get redder and about six months from now ″will settle down as a beautiful oval red spot,″ Beebe said.
The darkening is being caused by the changing color of the Southern Equatorial Belt, which sits just north of the spot, she said.
The belt faded from brown to white in the early 1970s, then turned brown again in 1974, said Glenn Orton, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena.
It appears brown when sunlight hits natural gas, or methane, and ammonia to create yellow-brown photochemical smog, which drifts down in Jupiter’s atmosphere and absorbs light hitting the atmosphere, Beebe said.
She said the belt changes to white when Jupiter’s internal heat pushes enough ammonia ice crystals upward, where winds up to 330 mph spread the crystals out to form a white deck of light-reflecting cirrus clouds.
Beebe said that when the belt is brown, eddies in its winds start feeding ammonia ice crystals into the Great Red Spot, so white ice washes out the red color.
When the belt turns white again, the eddies diminish, reducing the amount of ice entering the spot and allowing it to start turning dark red, she added.
During August and September, Orton studied the belt through the Infrared Telescope Facility, NASA’s heat-measuring telescope on Hawaii’s Mauna Kea volcano. He found the Southern Equatorial Belt had cooled considerably, showing icy clouds were blocking heat from warmer atmospheric gases below.
Beebe said the belt will turn brown again within about 18 months as violent storms mix atmospheric gases.