Moons of the Solar System
9 of 10
Neptune's main moon is one of the coldest places in our solar system. It's so cold on Triton that even nitrogen freezes and sits as ice on the surface.
Fun Fact: Triton orbits Neptune in the opposite direction of that planet's rotation. This is called a retrograde orbit. Triton is the only large moon in the solar system with a retrograde orbit around its planet, leading scientists to believe that Triton formed elsewhere and was captured by Neptune's gravity long ago. Photo source: NASA
Next: More popular galleries