Unlike all other large planetary moons in the Solar System, Triton has a retrograde orbit, indicating that it was captured rather than forming in place; it was probably once a dwarf planet in the Kuiper belt.
A diferenza doutras grandes lúas planetarias do Sistema Solar, Tritón ten unha órbita retrógrada, indicando que foi capturado en vez de formarse alí; probablemente algunha vez foi un planeta anano no cinto de Kuiper.