A lot of people comment on the amount of time it has taken us to get back to manned moon missions but in truth humanity (USA, ESA, JAXA, China, Russia) has been back to the moon many many times, we are finding out more about it all the time and may even have a private company go there soon. On the other hand, the greatest probe of all time Voyager 2 travelled to Uranus and Neptune once on a flyby and remains the only probe to have done so, thus far. How long will it be before the news reports report the "first encounter with either Uranus or Neptune since the twentieth century probe Voyager 2 visited it".

I think we could be talking of seventy year gap, ie 2058.