The orbit of Triton is inclined about 23° to the equatorial plane of Neptune. By contrast, all of the other large moons in the solar system are in nearly equatorial orbits around their planets. What can you surmise about Triton from this?
A)Triton's orbital inclination has existed since the beginning of the solar system.
B)A large orbital inclination is a relatively recent development for Triton-perhaps only a few hundred million years old.
C)Neptune's own axial tilt toward its equatorial plane must have been 23° more when it was formed than it is now.
D)Triton was probably formed in an equatorial orbit, but it is now in the process of transitioning to a polar orbit.

Question

Quizplus · Accepted Answer

The fact that all other large moons in the solar system are in nearly equatorial orbits suggests that Triton's large orbital inclination is not a common occurrence. Since the other moons are in equatorial orbits, it is unlikely that Neptune's axial tilt was 23° greater when it was formed. Additionally, there is no evidence to suggest that Triton was ever in an equatorial orbit or that it is transitioning to a polar orbit. Therefore, the most likely explanation is that Triton's current large orbital inclination is a relatively recent development, perhaps only a few hundred million years old.

The Orbit of Triton Is Inclined About 23° to the Equatorial