These radiation belts are analogous to the Van Allen belts above Earth's atmosphere. The probe discovered new radiation belts of helium and heavier ions that extend to within 0.4 jovian radius of the cloud tops. Although all the Galileo probe data have been returned to Earth, it will take some time, perhaps years, before we understand what they imply about Jupiter and the solar system. In many instances new questions have been raised. This, of course, is how planetary exploration works.
New information changes old ways of thinking and raises new questions to explore.
In this way our overall understanding of the solar system increases. The Galileo orbiter will return information about Jupiter, its four large moons, and Jupiter's magnetic field until December 1997. The first close encounter with Ganymede, the largest moon in the solar system, occurred on June 27, 1996. Richard E. Young is a research scientist in the Space Science Division at NASA Ames Research Center. He has served as the Galileo probe project scientist since 1988.