A camera aboard the Voyager 2 spacecraft has photographed the first hints of a weather pattern on Uranus, and scientists say they might be seeing an icy fog over the planet's south pole.
"It is the first time we have seen any detail in the atmosphere from our Voyager (television camera) images," said Ellis Miner, deputy project scientist at the National Aeronautics and Space Administration's Jet Propulsion Laboratory.
Voyager 2 was launched in 1977, explored Jupiter in 1979, Saturn in 1981 and will have its closest encounter with Uranus on Jan. 24, when it flies within about 50,000 miles of the solar system's third-largest planet.
Rapidly Closing In
As of today, Voyager 2 will be 1.84 billion miles from Earth and 20.7 million miles from Uranus as it speeds toward that planet at 40,000 m.p.h., project manager Dick Laeser said.
One of the probe's two telephoto television cameras photographed the apparent weather pattern in the Uranian atmosphere in late November. Since then, JPL scientists have debated whether the pattern really exists or is a product of extreme computer processing and photo enhancement.
"We are beginning to see, we think, with heavy processing, some hints of atmospheric patterns," Laeser said Friday.
He said the pattern was observed only when 13 to 30 photographs were superimposed on each other and enhanced. "I'm not convinced it's real," Laeser said.
But Miner said, "We're fairly confident that the pattern is real. The interpretation (that it's caused by haze), however, is highly speculative at this point."
Pattern at the Pole
The pattern appears as a dark area around the planet's south pole, which is facing the sun since, unlike Earth and most other planets, Uranus lies on its side. Encircling the dark polar area is a distinct, grayish circle, which in turn is surrounded by a whitish area, Miner said.
Miner said the dark and gray areas may be caused because "a haze high in the atmosphere" above the south pole reflects much less light than the underlying gases in the planet's atmosphere.
"The haze would probably be ice particles high in the atmosphere," he said. "It would be like a fog."
Recent photographs also are beginning to detect hints of five more of the nine, charcoal-black rings known to encircle Uranus.
Uranus, a gaseous planet 32,000 miles in diameter, is 64 times bigger than Earth but only 14 1/2 times as heavy. In unenhanced photographs taken by Voyager 2, the planet still looks like a bluish tennis ball without any visible details.
After its encounter with Uranus, Voyager 2 will continue toward an encounter with Neptune in August, 1989. Its twin, Voyager 1, also explored Jupiter and Saturn, but is soaring into unexplored space above the plane of the planets.