Magazine article Science News

Windy Doings on the Ringed Planet. (Slowdown on Saturn?)

Magazine article Science News

Windy Doings on the Ringed Planet. (Slowdown on Saturn?)

Article excerpt

The winds in Saturn's upper atmosphere are some of the swiftest in the solar system, but recent findings suggest there's been a dramatic slowdown. Observations with the Hubble Space Telescope indicate that the band of wind circling Saturn's equator is now traveling 270 meters per second, a 40 percent drop from the supersonic speed it had just 22 years ago.

If confirmed, the data offer the first evidence "that wind speeds in the atmospheres of the giant planets can suffer strong changes, says Agustin Sanchez-Lavega of the Universidad del Pais Vaseo in Bilbao, Spain. He and his colleagues describe their findings in the June 5 Nature.

The researchers cite several explanations for a possible slowdown. Because Saturn, like Earth, is tilted on its axis, different parts of the ringed planet receive different amounts of sunlight during its 29-year orbit around the sun. If this variation accounts for changes in equatorial wind speed, that speed should change noticeably in about 7 years, the next time Saturn's equator is tipped toward the sun, comments John T. Clarke of Boston University.

The shadow cast by the planet's giant ice rings also might affect wind speed by blocking varying amounts of sunlight at the equator. Another possibility, notes Sanchez-Lavega, is that a huge equatorial storm system, dubbed the Great White Spot (SN: 11/24/90, p. 325), has disturbed the band of wind.

However, Sanchez-Lavega's team acknowledges that what appears to be a slowdown in wind speed might simply be an artifact of the data. Hubble examined Saturn from 1996 to 2002, and the Voyager spacecraft did so in 1980 and 1981. …

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