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These two images of Neptune were taken by Voyager 2's narrow angle camera when the spacecraft was about 12 million km (7.5 million miles) from Neptune. Resolution is about 110 km (68 miles) per pixel.
During the 17.6 hours between the left and right images, the Great Dark Spot, at 22 degrees south latitude (left of center), has completed a little less than one rotation of Neptune. The smaller dark spot, at 54 south, completed a little more than one rotation, as can be seen by comparing its relative positions in the two pictures.
The Great Dark Spot and the smaller spot have a relative velocity of 100 meters per second (220 miles an hour). The light and dark bands circling Neptune indicate predominantly zonal (east/west) motion. The diffuse white feature north of the Great Dark Spot is near Neptune's equator, and rotates with about the same period as the Great Dark Spot. The streak of bright clouds at the south edge, and just east of the Great Dark Spot, are its constant companions, and change the details of their appearance, often within a few hours. Changing brightness of the cloud streaks could be a result of vertical motions.
The Voyager Project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.