Fig 25.11.

Images of Uranus's atmosphere. (a) Towards one rotation pole.The left image is true color, and the right image is enhanced to show structure in the clouds (Voyager 2 image). (b) A large cloud (Voyager 2 image). [NASA]

as more data become available, should provide a good test of our ability to model planetary atmospheres with enough detail to predict or explain the differences.

Voyager 2 provided a good view of Uranus from a distance of five planetary radii. There is very little structure in the atmosphere. However, there is a polar haze, probably composed of methane and acetylene. There is also an extended hydrogen (atomic and molecular) corona. Ultraviolet emission from this corona had previously been detected from Earth-orbiting satellites. The rotation period of the atmosphere appears to be just under 17 hr.

Fig 25.12.

Images of Neptune's atmosphere. (a) True color image of clouds (Voyager 2 image). (b) Changes in great dark spot (Voyager 2 image). [NASA]

The wind speeds seem to be in the range of tens of kilometers per hour.

Voyager 2 also revealed an interesting temperature distribution. The equator is cooler than either of the poles. In addition, the pole facing the Sun is cooler than the shadowed pole. This is obviously an interesting problem in energy transport.

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