Comment Re:why is it always comets and asteroids? (Score 3, Interesting) 46
I don't know. Hydrothermal vents ETC are far more likely, the deep water would provide shielding from cosmic radiation. The first bacteria we know of, from ~3.8Ga or so were completely anoxic since the atmosphere had little to no free oxygen... and therefore no ozone to filter out the radiation that was bombarding the surface.
If life had started by surface impact you would more likely than not see adaptations passed down the generations to be resistant to radiation damage, yet we don't see any indication of that even in ancient strains that survive to modern times.
That's not to say the research isn't interesting, since it is. It just doesn't seem likely due to several factors that may or may not be solved for in the future, only time will tell.