When Pioneer 11 swept by the giant planet Jupiter last December, the little unmanned spacecraft took a dozen closeup pictures. Last week, after painstakingly clarifying the images by photographic and computer techniques, NASA released part of its planetary portfolio. The stunning photographs included the most detailed view yet of Jupiter's great red spot.
First observed through primitive telescopes three centuries ago, the puzzling, larger-than-earth-size blemish has been attributed to everything from an island of solid hydrogen in the planet's thick atmosphere to an anomaly in the strong Jovian magnetic field. Pioneer's closeup seems to confirm that the spot is in fact an area of hurricane-like turbulence trapped between atmospheric bands flowing in opposite directions. The flows, from right to left above and from left to right below the spot, give it a pronounced counterclockwise rotation. The atmospheric movement also creates smaller vortices nearby.
Next Target. As Pioneer headed toward its next target, Saturn, which it will reach in 1979, it shot the first close-ups of Jupiter's north polar region. They showed that at higher latitudes, Jupiter's banded atmospheric structure breaks down into swirling, scalloped forms spotted here and there with storms also similar to hurricanes. The turmoil occurs at the boundaries of opposite-flowing jet streams where winds reach to 300 m.p.h.