Ask HN: Why aren't humans planting bacteria all over the solar system?
Why aren't we, as human race, not trying to populate the rest of the planets in our solar system with bacteria/micro-organisms that we know will be able to thrive there?
One reason is "ecological", you don't want to destroy the local bacteria population before studding them. [I'm not sure if this is very likely, because the local "bacteria" will be better adapted to the local climate than the terrestrial bacteria.]
The second reason is that if a later mission discovers life there, it's better to be sure it was not a previous contamination by another mission.
Detecting the n=2 case of life in the universe would be huge. What type of molecules are common and what are different? There are some guess about which molecules are unavoidable, and which are only an accidental choices, but a second example of life can bring a lot of light into this discussion.
Also, it would be interesting to know if there was an ancient cross contamination that send life form one planet to the other, or they were independently generated.
In places where we are not 100% no life exists it would endanger that life. In places where we are not 100% there never was life, it would make traces of it harder to find. Bacteria left to grow might hinder us in progress on other planets in the future, e.g. by destroying resources we later need, by evolving in a way that they make us sick when we encounter them, ... Without a good purpose, why do that?
For the same purpose we have kids, to propagate life and our genes. Earth might will be around forever, and in the mean time we may or may not be able to habitate other planets ourselves.
So why not spread life to other planets anyway we can?