Further details of Saturn's atmosphere are evident in this photograph, a black-and-white print of a green-filter frame taken Aug. 21 by Voyager 2. At the time, the spacecraft was 4.6 million kilometers (2.8 million miles) from the planet; at this distance, the smallest observable feature was 85 km. (50 mi.) across. The dark oval cloud is about 4,000 km. (2,400 mi.) in diameter. Near its lower left edge, zonal winds blow westward at 20 meters-per-second (45 mph). By comparison, east-flowing winds reach speeds of 150 meters-per-second (330 mph) along the wavy edge of the white ribbon to the north of the dark oval. The observed flow patterns in the clouds reveal the wind shear to which they are subjected. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.