There has been speculation on these boards about a past relationship between Pluto and Triton, Neptune's largest moon. Triton is an oddball; it's very big compared to the other Neptunian satellites, and most notably, it orbits retrograde (backwards), an unstable orbit which puts the moon under enormous stress, so much so that it is one of the handful of places with active volcanism. (In Triton's case, this amounts to geysers of liquid nitrogen. Triton may be active, but it is still very cold.)<br /><br />In general, most scientists shy from reaching the conclusion that they're related, as there isn't enough data to support it. It is possible, but there's no way to know at present. However, most scientists do suspect that Triton was a captured Kuiper Belt Object similar to Pluto, and that Pluto's orbit was also disturbed by Neptune at some point. Today, Pluto orbits in a resonance with Neptune, making it in some respects similar to the minor planet Cruithne, which has a vaguely similar relationship with Earth. This sort of thing may be more common than we realize. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>