If you've opened a fortune cookie, you've probably read an aphorism, like this one, 'The world may be your oyster, but that doesn't mean you'll get its pearl.' In just a few words this quote tells the reader a lesson about life, that you have nearly limitless possibilities, but not all of them lead to a great reward.
The exploration of Neptune has only begun with one spacecraft, Voyager 2 in 1989. Currently there are no approved future missions to visit the Neptunian system. NASA, ESA and also independent academic groups have proposed future scientific missions to visit Neptune.
a. Neptune formed out of the solar nebula in much the same manner as the other Jovian planets. b. Pluto was probably a moon of Neptune that escaped. c. Triton and Nereid are both captured objects from the inner solar system, probably the asteroid belt.