Quote:
Originally Posted by scc
I'm pretty sure that there was a rock found from Mars that showed signs of carrying bacteria, that turned out to have come from Earth to begin with (The rock went from Earth, to Mars and then back again) so it's possible
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Do you have a cite for that? I just finished a graduate level class in meteorites, and ALH84001 has unequivocal Martian isotope ratios, not terrestrial. The 'fossils' are controversial, not the origin.
Panspermia would most likely work on the scale of bacteria and other single-celled organisms, not more complex life. The result would be ecosystems descended from the same progenitors, but not necessarily more closely related than, say, humans and the tube worms that live in black smokers on mid-ocean ridges.