How long to become a habitable planet

I am creating a world for Sci Fi story in which I am trying to have two non-tidally locked earth sized planets in a binary orbit around Alpha Centauri A. The only way I can think of this happening is by a double event in which the original planet, let's say around 3 Earth masses, was struck by a 1 Earth mass body and split to create two roughly Earth sized world's orbiting eachother.

Within a number of millions of years, they would become tidally locked. So I need another event to allow one, or both of them to have their own spin and be habitable. The best suggestion I received to do that is to have an impact event to resurface the planet(s) and add a soon to them. Then potentially they will have a more difficult time to become tidally locked again because of this and the fact that they would probably have different spins at different angles.

The question I have, is how long after this event would the planets become habitable for humans? Intelligent life, or even animal life, does not need to exist/have been formed on the planets. By habitable I mean that they should have a breathable atmosphere with sustainable temperatures. The humans traveling there will have a decent ability to terraform the planet from that point.

Yes, I know this is extremely unlikely to ever actually happen, but the pen is mightier than the astrophysics textbook. If there are any suggestions for another means to achieve my end result then please feel free to share.

Thanks

posted almost 5 years ago

user72655‭

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