ARC-1989-A89-7000

Photo by Voyager 2 (jpl) These images show changes in the clouds around Neptune's Great Dark Spot (GDS) over a four and one-half-day period. From top to bottom the images show successive rotations of the planet -- an interval of about 18 hours. The GDS is at a mean latitude of 20 degrees south, and covers about 30 degrees of longitude. The violet filter of the Voyager narrow angle camera was used to produce these images at distances ranging from 17 million kilometers (10.5 million miles) at the top, to 10 million kiloeters (6.2 million miles) at the bottom. The images have been mapped on to a rectangular latitude-longitude grid to remove the effects of changing viewing geometry and the changing distance to Neptune. The sequence shows a large change in the western end (left side) of the GDS, where dark extension apparent in the earlier images converges into an extended string of small dark spots over the next five rotations. This 'string of beads' extends from the GDS a surprisingly large angle relative to horizontal lines of constant latitude. The large bright cloud at the southen (bottom) boarder of the GDS is a more or less permanent companion of the GDS -- reminiscent of flow around the Great Red Spot in Jupiter's atmosphere. This activity of the GDS is surprising because the total energy flux from the sun and from Neptune's interior is only 5 percent as large as the total energy flux on Jupiter. (JPL Ref: P-34610 Voyager 2-N23)