The perception of Neptune as much darker and bluer than Uranus was "cemented" when pictures were sent back by the Voyager 2 probe after it flew by the two planets in 1986 and 1989, said The Times.

Uranus has not had a whole lot of love from NASA and has been explored by a probe only once. Voyager 2 sent back spectacular pictures of the ice giant, resembling a perfect blue ball in space.

The resulting pictures revealed a smattering of different ... "It helps build on the story that some of these moons at Uranus may be really interesting — that there may be several ocean worlds ...