Jupiter's volcano-pocked moon Io has been found by NASA's Galileo spacecraft to have a giant iron core that takes up half its diameter, scientists report in today's issue of Science magazine. The spacecraft also has detected a large "hole" in Jupiter's magnetic field near Io, leading to speculation about whether Io possesses its own magnetic field. ... Galileo scientists also are trying to determine the cause of the hole they found in Jupiter's magnetic field when the spacecraft was closest to Io. ...

... Voyager Spacecraft Introduction (This Page) . ... The twin Voyager spacecraft, over the course of a dozen years, drew back the curtain on nearly half of the solar system . From launch in 1977 through the spectacular parting shots in 1989 of Neptune at the outer reaches of the solar system, this pair of gangly, instrument-laden spacecraft explored four planets -- Jupiter , Saturn , Uranus and Neptune -- as well as tens of moons, and the rings and magnetic environments of those planetary systems. ...

... A dynamo is created in a magnetic field by an electric circuit, part of which is moving relative to the rest (additional conditions must also be met). ... Furthermore, the plasma between them conducts electricity very well along its magnetic field lines, which act as if they were wires connecting Io and the planet (drawing). ... The drawing is not to scale. ... The Hubble Space Telescope , using its Wide Field and Planetary Camera 2, has been photographing auroras of the planet Jupiter. ...

Cosmic Research, Vol. 42, No. 5, 2004, pp. 435­488. Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 5, 2004, pp. 453­508. Original Russian Text Copyright © 2004 by Veselovsky, Panasyuk, Avdyushin, Bazilevskaya, Belov, Bogachev, Bogod, Bogomolov, Bothmer, Boyarchuk, Vashenyuk, Vlasov, Gnezdilov, Gorgutsa, Grechnev, Denisov, Dmitriev, Dryer, Yermolaev, Eroshenko, Zherebtsov, Zhitnik, Zhukov, Zastenker, Zelenyi, Zeldovich, Ivanov-Kholodnyi, Ignat'ev, Ishkov, Kolomiytsev, Krasheninnikov, Kudela,