Common yeast can survive Martian conditions

We should be dropping bags of extremophile organisms into the Martian atmosphere to get a start on terraforming it.

Yeah, and you want to explain to future generations why we could have had a happy relationship with Mars but no, we gave it a really bad yeast infection and now it never wants us anywhere near it? Hmmm? :-)

I heard an interesting speculative talk about why we should be putting hard microbes on every planet and moon in our solar system because we'll probably cause an extinction event and perhaps the other celestial body could get a head start on evolving a better form of intelligence.

Potentially a much greater filter is going from unicellular to multicellular life, no? If it likely took billions of years to get from unicellular to multicellular life on Earth, and only (hundreds of) millions of years to get to life that can conduct spaceflight, then perhaps microbes wouldn’t be the best way to attack this problem (I’m assuming you’re talking primarily about unicellular microbes, of course).

Well in the talk the presenter was talking things like tardigrades which are multicellular. The challenge with tardigrades (and any multicellular life) is that you want it to be reproducing (and hence evolving) so it has to be able to do so under conditions on the body you drop it on too. Again, since the talk was speculative there were various speculative ideas such as ice penetrators to put them into the liquid under the ice of moons like Enceladus.

Evolvable being the key of course. Many, if not most, folks I've met in the scientific community are intensely opposed to this sort of open ended experimentation. NASA has a whole team that insures things we send to other bodies are not carrying any organisms (single cell or otherwise) for this very reason.