The history of Neptune and its system of rings and satellites was likely profoundly affected by the capture of of Triton. It is thought that Neptune had an earlier system of satellites and perhaps rings, but the capture of Triton disrupted Neptune's original system causing possible ejection of some satellites, reformation of others (i.e., the inner satellites) and an orbital change for Nereid. Triton's origin was somewhere in the outer solar system, where it persisted until some time after "heavy bombardment" end (about four billion years ago) when it was captured by Neptune. At that time there may have been catastrophic interaction with pre-existing Neptunian satellites.
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