Some of Jupiter's smaller outer moons have retrograde orbits, indicating capture occurred.

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Quizplus · Accepted Answer

Retrograde orbits, meaning the moons are orbiting in the opposite direction of Jupiter's rotation, are usually indicative of capture by the planet's gravitational pull rather than forming in the protoplanetary disk around the planet. Retrograde orbits are highly unlikely to occur naturally and are typically the result of the moon being captured by the planet's gravity. Therefore, the retrograde orbit of some of Jupiter's smaller outer moons suggests that they were captured moons rather than formed in place.

Some of Jupiter's Smaller Outer Moons Have Retrograde Orbits, Indicating