Neptune’s other moons were normal until Triton crashed the party

By Leah Crane

It came in like a wrecking ball. Neptune has one of the weirdest collections of moons in our solar system, and it’s Triton’s fault. The planet’s largest moon probably smashed into the calm moon system that was there before it arrived, knocking everything out of sync.

Planetary scientists have long suspected that the huge moon Triton is an interloper from outside the Neptune system. Now they have calculated what the other moons may have looked like before the intrusion.

All of the other gas giants in our solar system – Jupiter, Saturn and Uranus – have fairly similar systems of moons. In each of these systems, the mass of the planet is about 10,000 times bigger than the total mass of all the moons together. For the most part, these planets have several small moons, all orbiting in the same direction as the planet spins.

But Neptune is different. It has several tiny moons either very close in or far away from the planet – most of which orbit in the direction of the planet’s spin – and one huge one, Triton, orbiting in the opposite direction.

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