Feb 27 2002
From The Space Library
Administrator Sean O’Keefe testified before the U.S. House Committee on Science and Technology concerning NASA’s FY 2003 budget. Administrator O’Keefe also reported a recent independent audit of NASA’s finances, which NASA planned to release to the public the next day. According to newspaper reports, the lawmakers questioned O’Keefe in a tone that was frequently skeptical and even critical. At the time of O’Keefe ’s testimony, NASA was already under public scrutiny regarding its budget overruns and financial accounting procedures, and critics had proposed reductions in its budget for human space travel. (Karen Masterson, “Skeptical Lawmakers Quiz NASA Chief About Budget,” Houston Chronicle, 28 February 2002.)
For the first time, scientists made combined internal and external observations of Jupiter’s magnetosphere, the biggest object with distinct boundaries within the solar system. In the first conjunction of two spacecraft at an outer planet, the Galileo spacecraft conducted observations from inside Jupiter’s magnetosphere, a comet-shaped region of space filled by the planet’s magnetic field. Meanwhile, on the outside of the magnetosphere, the Cassini-Huygens spacecraft monitored the effects of solar wind particles that flow from the Sun through the solar system. Scientists augmented the data gathered during these observations with data from near-simultaneous observations collected from radio telescopes on Earth and from spacecraft orbiting Earth, namely the HST and the Chandra X-ray Observatory. Researchers found that, although Jupiter’s magnetosphere deflects solar winds, shock waves carried by solar winds compress the magnetosphere, stimulate radio emissions from within it, and brighten auroras at the planet’s poles. The observations helped bolster researchers’ confidence in their understanding of Earth’s own protective magnetosphere. (NASA JPL, “Solar Wind Buffets Vast Jupiter Region, Team Approach Reveals,” news release, 27 February 2002; Thomas W. Hill, “Magnetic Moments at Jupiter,” Nature 415, no. 6875 (28 February 2002): 965–966.)
Researchers using data from NASA’s Chandra X-ray Observatory found a substantial, pulsating source of x-rays in Jupiter’s atmosphere near the planet’s north magnetic pole. Existing theories could not explain either the pulsations or the location of the x-ray source. Scientists had posited that energetic oxygen and sulfur ions steadily precipitate from Jupiter’s inner magnetosphere, entering the planet’s polar regions and producing a northern aurora of x-rays. However, images from Chandra revealed that most of Jupiter’s northern auroral x-rays originate at latitudes that only ions precipitating from Jupiter’s outer magnetosphere could reach. In addition, researchers found that the hot-spot source of the x-rays was pulsating at 45-minute intervals, contradicting scientists’ theory that the x-ray emissions originate from a steady precipitation of ions in the inner magnetosphere. Although this discovery invalidated previous theories, scientists were not yet able to explain the process they had observed. Specifically, according to Chandra’s measurements, the researchers found insufficient energetic oxygen and sulfur ions within the required distance of the ion source~at least 30 times Jupiter’s radius~to account for the observed x-ray emissions. (NASA, “Jupiter Hot Spot Makes Trouble for Theory,” news release 02-34, 28 February 2002; G. R. Gladstone et al., “A Pulsating Auroral X-ray Hot Spot on Jupiter,” Nature 415, no. 6875 (28 February 2002): 1000–1003.)
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