Re: Tasty Morsel
Well.... anything brought from Earth that's still viable and able to jump-and-thrive into something that hostile to most of life here, especially after surviving cleanroom treatment, launch, a rather lengthy bit of space travel and irradiation, atmospheric entry and a lengthy stay on the martian surface....
It would pretty much deserve living there on Mars and inherit the planet before we figure out how to live there, if ever.
Unlikely as it is already, as pointed out above it then has to compete with the highly specialised life that may possibly exist in that environment already, with precious little chance of beating those specialists at their own game.
The scenario is conceivable, but it's so far down the probability curve it's cuddling up to the event horizon of "ludicrous".