Hi Rallem:

It is very important that you do not confuse my hypothetical views as fact. My views frequently run against accepted science when it comes to this Solar System and its contents. These are just my unproven opinions.

You ask:
?Could you please explain to me why a retro-grade spin would be harmful? Also maybe explain why you think the planet would eventually achieve a normal spin? I can sort of understand the idea of gravity having its effects, but are we sure it will do this??

Consider the Sun as a huge dynamo using fusion to create energy. Left to itself it is static except it is revolving around the Galaxy at possibly 450 miles an hour and it is rotating in about 25 earth days at the equator. The point is that it appears to be completely self sustaining. I think not.

Each of the solar objects provide a different center of gravity between themselves and the Sun. The larger objects, like Jupiter, will have a CofG possibly half way from the Suns center to the suns edge. Earth CofG will be close to the Suns center, etc. It is this ring of objects that provide the sustaining action that keeps the Sun working for us, churning the fusion process.

By this means the entire system is part of a working dynamo causing the planets/objects to have an electrical magnetic relationship with the sun. Venus is working against the system as a result of retrograde rotation so it is hot. There is more to it but that will do for now. The system seeks to be synchronized so to join in Venus will eventually get normal rotation and join the family of planets/objects. JUST MY VIEW, not accepted science.

No doubt Earth had water of its own as did Venus and Mars. We got more from them along the way, a lot more. Comets, in general are ice balls and none are known to be large enough to do what you want. Possibly an asteroid or some interlopper from space; very questionable.
jjw