FWIW we trade so much material with outer space (super volcanos etc) that if life could colonize space that easily it would have done so billions of years ago.
Could we create a minimially viable living environment for these extremophiles to survive on other planets? For humans, we'd need pretty incredible technology to sustain life on mars, but for tardigrades, they could probably survive with a lot less.
Say, a very hardy algae that could make it in some suitable microbiome - like humid cracks in the rocks, or a fungus that could hang out in underground caverns shielded from UV radiation.
If we are trying to seed a place with life where we can't reliably go ourselves, it seems important that the 'colony' should become self-sustaining immediately-ish.
(Also I find the idea of launching swarms of micro-pods loaded up with hardy, tiny lifeforms endearing - like throwing seed bombs over a tall fence :) )