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June 30, 1995

For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070.

NEW UNDERSTANDING OF EARTH'S LOWER MANTLE

Recent high-pressure, high-temperature experiments on minerals of the Earth's lower mantle have yielded new information on the crystallography of the region that composes the largest fraction of our planet. The experiments--by investigators Charles Meade, Ho-kwang Mao and Jingzhu Hu of the Carnegie Institution of Washington were conducted at the National Science Foundation's Center for High-Pressure Research, funded by the division of earth sciences at NSF. In recent years, scientists have studied Earth's interior by comparing seismological data to the results of high pressure experiments. From this work, it had been proposed that orthorhombic-structured perovskite is the predominant phase of the lower mantle and is, therefore, the most abundant mineral in the Earth. This hypothesis has wide ranging implications for all earth sciences, yet has been untested to date because of inadequate experimental capabilities for characterizing materials under the conditions of simultaneous high pressure and temperature that exist in Earth's lower mantle. The recent results of Meade, Mao and Hu show that the crystallography of the lower mantle may differ significantly from previously proposed models. These are the first experiments to have measured diffraction from minerals at pressure and temperature conditions corresponding to depths as great as 1650 kilometers within the Earth. The potential ramifications for interpreting the nature and behavior of the inner planet -- the circulation patterns of mantle convection and the driving forces of plate tectonics -- are widespread and fundamental, according to the researchers. [Cheryl Dybas]

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COMET SHOEMAKER-LEVY CAUSED OUTBURST IN JUPITER'S MICROWAVE RADIATION

During last July's impacts of Comet Shoemaker-Levy 9 with Jupiter, microwave emissions from electrons in the planet's magnetic field -- as measured by a global network of 11 Earth-based radio telescopes -- showed a dramatic outburst, according to an article in the June 30 issue of Science. The outburst may have been caused by a redistribution of the emitting particles, and sheds light on the configuration of Jupiter's magnetic field. Images from two radio telescopes -- the National Science Foundation-supported Very Large Array and the Australia Telescope -- showed that emissions were enhanced locally near the planet's magnetic equator. The radio telescope network was used to monitor Jupiter's microwave emission during the impacts and to search for changes in radiation from the planet's inner magnetosphere, the region around Jupiter where charged particles are trapped by the planetary magnetic field. Before the impacts, researchers had predicted the opposite: the comet's dust would lead to a reduction in the planet's radio emissions. "The highlight of the radio observations instead was a dramatic increase in the radio flux density during the six days of cometary bombardment," write the authors, 27 collaborators headed by Imke de Pater, University of California-Berkeley. "The comet impact has provided us with a unique experiment to unravel one of the outstanding issues in magnetospheric physics: the energization and radial transport mechanism of the energetic electrons in Jupiter's radiation belts," they write. [Lynn Simarski]

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LANE URGES UNITY, ACTIVISM AMONG SCIENTISTS

NSF Director Neal Lane, in a June 26 speech to AAAS affiliates, echoed Vannevar Bush by reminding attendees that, "Science can be effective in the national welfare only as a member of a team." Lane said the strength of this nation's R&D comes from a "complex interconnection of all components" including mission agencies, research universities, national labs, technology centers, private research foundations, various industry consortia, small businesses, and the science and engineering workforce. Lane stressed that a united scientific enterprise must, in a non-arrogant manner, convey to various audiences including the public and elected representatives -- the value and effectiveness of science and technology in society. He also told attendees that no matter how well they perform these two tasks, federal funding for R&D will not be exempt from cuts because of the extraordinary tight budget times. But he urged that the scientific community can either participate and help guide R&D funding with reasoned advice, or not participate and let less knowledgeable people make critical decisions. [Beth Gaston]

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