Comment Re:Longer for live to evolve in the first place (Score 3, Interesting) 27
Life started on Earth very soon after there was liquid water, yet it took billions of years before eukaryotes arose. Being a eukaryote is a big deal: having mitochondria lest us have huge genomes compared to a bacterium's, and that opens the door for complexity and sophistication. Every living creature with interesting structure is a eukaryote, and the innovation that let us attain this complexity (a successful endosymbiosis) happened exactly once in the whole history of life on Earth.
Imagine trying to eat rabbits but getting indigestion, and having the rabbits start breeding inside of you but lose almost all their rabbit-like traits, and in the process you gain superpowers of being able to metabolize grass and grow a hyper-brain that lets you out-compete every other sapient being on the planet. That's not much more wild a story as what actually happened with the first successful endosymbiosis.
The ratio of (time-to-first-life given temperate water on Earth) / (time-to-eukaryotes given first life on Earth) is tiny; maybe 1:100 or so. That's evidence that complex life might be much more rare than simple life. In fact, I would guess that successful endosymbiosis might be one of the strongest of the great filters; it might be that complex life is nearly vanishingly rare and it's only the anthropic principle that gives us a reason for finding it on Earth.
If that's true then we'd anticipate finding simple life on other rocks, but rarely anything morphologically complex. Increasing the length of time Mars had water probably increases the chances they got bacteria-like life, but I would be surprised if Martian life ever had anything like membrane-bound organelles.