Giant polar cap dominates Uranus; dark tempest is raging on Neptune. The two major planets beyond Saturn have only been visited once by a spacecraft, albeit briefly. NASA's Voyager 2 spacecraft swung by Uranus in 1986, and Neptune in 1989. Our robotic deep-space tourist snapped the only close-up, detailed images of these monstrous worlds. For Neptune, the images revealed a planet with a dynamic atmosphere with two mysterious dark vortices. Uranus, however, appeared featureless. But these views were only brief snapshots. They couldn't capture how the planets' atmospheres change over time, any more than a single snapshot of Earth...