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GALILEO PROBE SUGGESTS PLANETARY SCIENCE REAPPRAISAL
Preliminary analysis of early data returned by NASA's historic Galileo probe mission into Jupiter's atmosphere has provided a series of startling discoveries for project scientists.
Information on the extent of water and clouds and on the chemical composition of the Jovian atmosphere is particularly revealing. Instruments on the descent probe found the entry region of Jupiter to be drier than anticipated, and they did not detect the three-tiered cloud structure that most researchers had postulated. The amount of helium measured was about one-half of what was expected.
These initial findings are encouraging scientists to rethink their theories of Jupiter's formation and the nature of planetary evolution processes, according to probe project scientist Dr. Richard Young of NASA's Ames Research Center.
"The quality of the Galileo probe data exceeds all of our most optimistic predictions," said Dr. Wesley Huntress, NASA associate administrator for space science. "It will allow the scientific community to develop valuable new insights into the formation and evolution of our solar system, and the origins of life within it."
The descent probe made the most difficult planetary atmospheric entry ever attempted, according to probe manager Marcie Smith of the Ames center. Entering Jupiter's atmosphere on Dec. 7, 1995, it survived entry speeds of over 106,000 mph, temperatures twice those on the surface of the Sun and deceleration forces up to 230 times the strength of gravity on Earth. It relayed data obtained during its 57-minute descent mission back to the main Galileo spacecraft more than 130,000 miles overhead for storage and transmission to Earth. The Galileo orbiter is now embarking on a two-year mission to study Jupiter and its moons.
"The probe detected extremely strong winds and very intense turbulence during its descent through Jupiter's thick atmosphere. This provides evidence that the energy source driving much of Jupiter's distinctive circulation phenomena is probably heat escaping from the deep interior of the planet," Young said. "The probe also discovered an intense new radiation belt approximately 31,000 miles above Jupiter's cloud tops, and a veritable absence of lightning," he noted.
The composition of Jupiter's atmosphere offered some surprises, according to project scientists. It contains significantly lower than expected levels of helium, neon, and certain heavy elements, such as carbon, oxygen and sulfur.
The issue of the colors of Jupiter's atmosphere has been much-debated, but no consensus has developed from probe data to date. The probe encountered no solid objects or surfaces during it's entire 600-kilometer journey. This was as expected for a gas-giant planet such as Jupiter.
What are the implications of these findings? Mo