Planning a probing voyage to Jupiter: The adroit Galileo spacecraft, crammed with advanced instrumentation, should answer some age-old questions about the mysterious planet

What makes Jupiter's Great Red Spot red? How were planets formed? One of the most complex unmanned explorations of a planet ever undertaken, scheduled to begin next May when a two-in-one spacecraft " one part an orbiter, the other an atmospheric probe " sets out on a four-year mission to explore Jupiter and its four largest satellites, may furnish some answers. The craft Galileo, designed and built by the United States with significant international participation, will be launched from the space shuttle. Its mission will be to return to the Jovian system observed distantly in the 1970s by the Pioneer and Voyager vehicles and to penetrate Jupiter's atmosphere to take samples for the first time.