4. Neptune
Neptune Great Dark Spot in High Resolution
Neptune Clouds Showing Vertical Relief
Neptune in Primary Colors - PIA01284.
Neptune's Stormy Disposition - PIA01542.
4. Neptune

4. Neptune



Diameter: 49,244 km
Orbit Radius: 29.97 AU
Orbital Period : 164.79 years
Rotational Period: 16.1 hours
Average Temperature: -214°C
Max/Min Temperature: Unknown
Composition: Icy
Number of Moons: 13
Rings: Yes
Atmosphere: 80% H2; 19% He; 1.5% CH4
Atmoshperic Pressure: Unknown
Gravity (Earth=1): 1.14
Mass (Earth=1): 17.15
Magnetic Field: Yes

Neptune's blue-green atmosphere is shown in greater detail than ever before by the Voyager 2 spacecraft as it rapidly approached its encounter with the giant planet. This color image, produced from a distance of about 16 million km, shows several complex and puzzling atmospheric features. The Great Dark Spot (GDS) seen at the center is about 13,000 km by 6,600 km in size — as large along its longer dimension as the Earth. The bright, wispy "cirrus-type" clouds seen hovering in the vicinity of the GDS are higher in altitude than the dark material of unknown origin which defines its boundaries. A thin veil often fills part of the GDS interior, as seen on the image. The bright cloud at the southern (lower) edge of the GDS measures about 1,000 km in its north-south extent. The small, bright cloud below the GDS, dubbed the "scooter," rotates faster than the GDS, gaining about 30 degrees eastward (toward the right) in longitude every rotation. Bright streaks of cloud at the latitude of the GDS, the small clouds overlying it, and a dimly visible dark protrusion at its western end are examples of dynamic weather patterns on Neptune, which can change significantly on time scales of one rotation (about 18 hours). These clouds were seen to persist for as long as Voyager's cameras could resolve them.

This picture of Neptune was produced from the last whole planet images taken through the green and orange filters on the Voyager 2 narrow angle camera. The images were taken at a range of 4.4 million miles from the planet, 4 days and 20 hours before closest approach.