The seventh planet dealt a serious blow to old ideas about the universe. From the beginning, Uranus lived up to its association with innovation and technology. When William Herschel found Uranus in 1781, he used an exciting new technology, the telescope.
Galileo had built an early telescope himself, with which he saw the moons of Jupiter in 1610, but by the 1700s the telescope was in use not only in astronomy but also in the shipping industry and the military.
The Moon and Pluto compared to the Earth. This picture was composed from File:Enceladus Earth Moon Comparison.png, File:Full Moon Luc Viatour.jpg, and File:Pluto impression.png, by Tom Reding (Wikimedia)
Looking at the Martian Manhunter now, what I find myself wondering (apart from why the green skin) is why Mars? Apart from alliteration, I mean.
No doubt its nearness played a part, although these days that works against him, as we know a great deal more about Mars now. The idea of human-like life on Mars has gone by the wayside. and if you asked anyone these days about Martians, they would probably think of Marvin the Martian instead.