Voyager planet probe, hints at icy fog

Press, 30 December 1985, Page 8

Voyager planet probe, hints at icy fog

NZPA-AP

Pasadena, California A camera aboard the Voyager 2 spacecraft has photographed the first hints of a weather pattern on Uranus, showing what scientists believe could be 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 and Saturn in 1981, and will have its closest encounter with Uranus on January 24 when it flies within about 80,000 km of the solar system’s third-largest planet Yesterday, Voyager 2 was 2.96 billion kilometres from Earth and 33.31 million kilometres from Uranus as it sped towards that planet at 64,360 km/h, said the project manager, Dick Laeser. One of the probe’s two telephoto television cameras phofographhed the apparent weather pattern m the Uranian atmosphere in late November. Since then, Jet Propulsion Laboratory scientists have privately debated whether the pattern exists or is simply a product of extreme computer processing and photo enhancement.

“We are beginning to see, e think, with heavy pro-

cessing, some hints of atmospheric (weather) patterns,” said Mr Laeser. The pattern was observed only when photographs were superimposed on each other and enhanced. “I’m not convinced its real We need to convince ourselves,” Mr Laeser said. Mr Miner said: Were fairly confident that the pattern is real. The interpretation (that it’s caused by haze), however, is highly speculative at this point” 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 was a distinct, grayish circle, which in turn was surrounded by a whitish area, Mr Miner said.

The dark and gray areas may be caused because a haze high in the atmosphere above the south pole reflects less light than the underlying gases in the planet’s atmosphere. The haze would probably be ice particles high in the atmosphere, Mr Miner said. It would be like a fog. In the early 19705, com-Euter-enhanced images of franus made by telescopes on Earth showed very vague hints of a blotch pattern in the planet’s atmosphere, but the pattern was different from that observed by Voyager 2. Recent photographs are

beginning also to detect hints of five more of the nine charcoal-black rings known to encircle Uranus. Mr Miner said the rings could not be distinguished separately, but the delta, gamma, and eta rings appeared on photos as one band, while the alpha and beta rings appeared as another band. Voyager 2 first detected faint hints of the outermost, or epsilon, ring, in October. So far, Voyager had failed to detect any convincing signs of the three innermost rings. ■ ' All of the five known Uranian moons have been photographed by Voyager 2. Messrs Laeser and Miner said they expected that additional moons would be discovered by the probe. Uranus, a gaseous planet 51,500 km in diameter, is 64 times bigger than Earth but only 14.5 times as heavy. In unenhanced photographs taken by Voyager 2, the E’ still looks like a tennis ball without any visible details. Mr Miner said it was believed that the planet’s atmosphere consisted mostly of gaseous compounds of hydrogen, carbon, nitrogen, oxygen, and perhaps helium, which surrounded a relatively small liquid or solid core. After its encounter with Uranus, Voyager 2 will continue towards Neptune until August, 1989.