Uranus and Neptune
Uranus and Neptune owe their blue color to a higher concentration
of methane gas, as compared to Jupiter and Saturn. They hold some
mysteries for us to unravel. For example, Uranus lies on its side as
it orbits the sun. Both planets have magnetic fields that are
oriented at large angles from their axes of rotation, and do not
appear to be centered in the innermost regions of the planets.
These gas giants also have large numbers of moons. Perhaps the most
intriguing of these moons is Neptune's moon, Triton, with its mountains of water ice.