User:E. Schenk/Drafts

Exploration
Voyager 2 has been the only spacecraft to visit Neptune whose closest approach to the planet occurred on August 25, 1989 at a distance of about 4,950 km over Neptune's north pole. This was Voyager 2&#39;s closest approach to any planet after leaving Earth. Because this was the last planet the spacecraft would be able to visit, a relatively close flyby by Triton was conducted regardless of the consequences to the trajectory, similar to what was done for Voyager 1&#39;s encounter with Saturn and its moon Titan.

The closest approach of Voyager 2 to Neptune occurred on August 25, 1989. Since this was the last major planet the spacecraft could visit, it was decided to make a close flyby of the moon Triton, regardless of the consequences to the trajectory, similarly to what was done for Voyager 1's encounter with Saturn and its moon Titan.

The probe also discovered the Great Dark Spot, which has since disappeared, according to Hubble Space Telescope observations. Originally thought to be a large cloud itself, it was later postulated to be a hole in the visible cloud deck.

Neptune turned out to have the strongest winds of all the solar system's gas giants. In the outer regions of the solar system, where the Sun shines over 1000 times fainter than on Earth (still very bright with a magnitude of -21), the last of the four giants defied all expectations of the scientists.

One might expect that the farther one gets from the Sun, the less energy there would be to drive the winds around. The winds on Jupiter were already hundreds of kilometres per hour. Rather than seeing slower winds, the scientists found faster winds (over 1600 km/h) on more distant Neptune.

One suggested cause for this apparent anomaly is that if enough energy is produced, turbulence is created, which slows the winds down (like those of Jupiter). At Neptune however, there is so little solar energy that once winds are started they meet very little resistance, and are able to maintain extremely high velocities. Nonetheless, Neptune radiates more energy than it receives from the Sun, and the internal energy source of these winds remains undetermined.

The images relayed back to Earth from Voyager 2 in 1989 became the basis of a PBS all-night program called Neptune All Night.

Refs
http://www.nineplanets.org/neptune.html http://solarsystem.nasa.gov/planets/profile.cfm?Object=Neptune&Display=OverviewLong http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1977-076A