[landryraccoon]

I don't think it's at all likely that life on Earth originated on Mars, but if it did then there could have been cross pollination of microorganisms over billions of years due to meteor impacts on both worlds throwing bits of crust into space. In fact if we do find life on Mars at some point it wouldn't be shocking if they are quite similar to bacteria found on Earth, since they might just be descendants of earth bacteria carried over from the impact that killed the dinosaurs.

[pdonis]

> if it did then there could have been cross pollination of microorganisms over billions of years

I don't think this is consistent with DNA evidence, since such cross pollination would be expected to show up as two sets of genetic lines of descent with very different characteristics, since the environment of Mars is very different from that of Earth; and we don't observer anything like that. In fact, if life was evolving separately on Earth and Mars, it might not take very long before the two lines of descent were not even compatible genetically, meaning that genetic exchange would be impossible even if the organisms were brought back together.

[isostatic]

Or ok the flip side perhaps life originated on mars or europa or even interstellar, with single cells organisms coming from there