Does the word seems to refer to a theoretical territory, rather than to a theory (once you've removed the terra)? The set of all places so infected and from one source.

That bacteria could survive only a couple of years on a meteor in space suggests that life could not have come from beyond our solar system.

Is the theory based on much evidence or on conjecture, and if conjecture, what reason is there to favor it over one of a terrestrial origin of life?