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January 23, 1996
Web posted at: 5:00 p.m. EST
From Correspondent Greg Lefevre
MOUNTAIN VIEW, California (CNN) -- Data returned by NASA's Galileo probe revealed unexpected findings about Jupiter's atmosphere that may help us understand other solar systems as well as our own, NASA officials said in a press conference Monday afternoon.
Instruments aboard the Galileo probe recorded higher winds, drier-than-anticipated conditions, a different cloud structure and little more than half the amount of helium researchers previously believed to exist in the planet's atmosphere.
The findings reignited speculation within the scientific community as to whether Jupiter is closer in composition to a planet or a tiny star that failed to ignite.
Scientists had conventionally thought that Jupiter evolved from the gas and dust cloud of the primitive solar nebula, but the probe's findings may force them to re-evaluate views of its formation, NASA's Dr. Richard Young said. (94K AIFF sound or 94K WAV sound)
Jupiter is ancient, and scientists believe it looks the way it did when the universe was formed. (357K QuickTime movie) It was the largest known planet until last week, when evidence was found of two larger planets orbiting stars similar to the sun. Changes in the theory of Jupiter's origin will affect scientists' theories about those planets, as well.
The probe released by the unmanned Galileo entered Jupiter's atmosphere December 7, and relayed a 58-minute weather report back to the mother ship before melting and vaporizing. (519K QuickTime movie)
Its scientific instruments recorded temperature, pressure, density, wind speed, chemical composition and radiation, and looked for lightning storms in the clouds. The data was stored on Galileo and fed back on a delayed basis.
In their preliminary assessment of the data, NASA scientists say the probe found that lightning occurs on Jupiter only about a tenth as often on Earth. Scientists said that is because of an absence of water clouds. And, they said, the virtual absence of lightning reduces the chances of finding complex organic molecules in Jupiter's atmosphere. Jupiter's winds were clocked at over 330 mph, twice as hard as previously thought.
Scientists were gratified and surprised at how well Galileo's equipment worked, said probe scientist Marcie Smith. (153K AIFF sound or 153K WAV sound)
Galileo, launched in 1989 aboard space shuttle Atlantis, will orbit Jupiter and eight of its 16 moons for two years. It will pass by Jupiter's moon Ganymede on June 27.
Scientists plan to continue to study the data for the next several years.
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