August 25th of the year 1989CE, at 09:23UTC, Voyager 2achieved closest approach to Triton. No spacecraft has landed there yet.
Pluto will be visited by the spacecraft New Horizon in 2015
Voyager 2 is the only spacecraft to have currently visited both.
Only one through 2009. The Voyager 2 probe visited Neptune in 1989, having previously passed Jupiter, Saturn, and Uranus. Voyager 2 took the first close-up photos of the Neptunian moon Triton and discovered 5 new inner moons.
All of the eight planets have been visited or orbited by space probes.
The first spacecraft to visit Mercury was Mariner 10 in 1974 -> 1975
Voyager 2 did a fly-by August 25, 1989 .
No spacecraft has visited all the planets.
Pluto will be visited by the spacecraft New Horizon in 2015
no
voyager 2
Voyager 2 is the only spacecraft to have currently visited both.
yes
Yes
none
Apollo 17
Humans, no. Unmanned spacecraft, yes.
Voyager 2 is the only spacecraft to visited Neptune.