One feature that is conspicuous by its absence is the storm system known as the Great Dark Spot. The second smaller dark spot, DS2, that was seen during the Voyager-2 encounter was also missing. The absence of these dark spots was one of the biggest surprises of this program. These dramatic changes in the large-scale storm systems and planet-encircling clouds bands on Neptune are not yet completely understood, but they emphasize the dynamic nature of this planet's atmosphere, and the need for further monitoring.