[Illustration: At different latitudes, the strong prevailing zonal winds produce different apparent rotation rates. Plotted here are the horizontal velocities measured from a pair of Voyager images taken one rotation (about ten hours) apart. Also shown for comparison are older ground-based measurements obtained from careful timings of the apparent rotation rate at different latitudes. The excellent agreement of the two plots indicates the stability of the zonal winds. Also, the wind pattern shows much greater symmetry between northern and southern hemispheres than do the more superficial cloud patterns.] “At first, Voyager seemed to do nothing but emphasize the chaos, not the order in Jupiter’s atmosphere,” Andy Ingersoll stated. “There are turbulent regions in which individual little spots seem to change every Jovian rotation. And the whole texture in certain turbulent regions is unrecognizable in one earth day.” With the Voyager spacecraft, more detail could be seen than ever before; in addition, changes could be observed on a small timescale, as they happened. “It became much more of a mystery how large-scale order could exist in the face of all this small-scale chaos. But I think we are beginning to see the order underneath. What we are looking at when we observe Jupiter are minute cloud particles representing only a small fraction of the mass of the atmosphere.” The large-scale order the scientists had found was a regular alternation of eastward and westward jets. “If we take all the measurements from Earth-based observations over the last 75 years, we find that every current that has ever been seen from the Earth over 75 years is visible in one ten-hour rotation. They’re all there—they were just invisible.” The ever-changing appearance was dancing above a regular, almost stationary pattern of alternating flows, which may come from deep within Jupiter’s atmosphere. Why this alternating pattern persists remains a mystery. Even if the underlying pattern can be thought of as a sort of Jovian climate, it still does not explain the mechanics of “the minor sideshow”—the changing weather patterns. Analysis of the Voyager pictures is sure to keep planetary meteorologists busy for many years to come. Lights in the Night Sky