Life on Mars: What Are the Odds?

So… is there life on Mars? I don’t know, but after everything I’ve read and seen and learned about the Red Planet, I feel like making up some numbers.

I’m going to say there’s a 10% chance that life exists on Mars today. Mind you, this is not intelligent life. It’s not even complex, multi-cellular life. No, I’m just saying there’s a 10% chance that some kind of microorganism is there, eking out an existence near the Martian R.S.L.s or in the permafrost near the Martian poles. And maybe we’ve already detected the first signs of these microorganisms’ activity.

But the odds of that are pretty low, in my opinion. I think there’s a much better chance—let’s say a 50% chance—that Mars supported life at some point in the past, and that we’ll find the fossilized remains of ancient Martian organisms preserved in rock. We’re probably still only talking about microorganisms (or rather microfossils), but given that Mars hasn’t been geologically active in a long time, those fossils should be extremely well preserved.

Lastly, I think there’s a 90% chance that, regardless of whether or not Mars supported life in the past or present, it will support life in the future. Human life, to be specific (as well as plant life and maybe some edible bugs). Maybe it’ll be nothing more than a small research station, or maybe it will be a full-fledged colony. But I’m 90% sure we’ll get there. I say this because a lot of very smart people (and a handful of very rich people) seem to be pretty determined to make it happen.

Anyway, these are my best guesses about the odds of finding life on (or bringing life to) Mars. Do you agree with my rough estimates? Do you think I’m way off? Let me know in the comments!

12 thoughts on “Life on Mars: What Are the Odds?

    1. Glad we’re in agreement! I felt like I was being a little too generous with my first estimate, but the methane burps convinced me to go for 10%. Otherwise I would’ve probably said 1%.


  1. Like Steve, I agree with your first two estimates. For the third, for me, 90% only works for research stations or very small token colonies. I think the chances of large scale colonization are low (10% maybe), at least until someone can find a compelling economic incentive. Long term, I could maybe see raising the percentage if we broaden the colonization proposition to include machine life.

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    1. I guess I am kind of hedging my bets with that one. I feel confident that a small research station will happen, or at least that we’ll try our best to make it work. If the research station goes well, I think full fledged colonization will happen eventually, but that’s a really big if in my mind.

      On the other hand if something goes wrong, if there’s something we don’t currently know about that makes humans incompatible with Mars or Mars incompatible with humans, then I think that’s the end of it. Also if it turns out there is life on Mars, we might decide not to endanger it with our presence.

      As for the economic incentives, I’ve read enough from Elon Musk, Robert Zubrin, and others to be convinced the incentives are there. Even selling people the dream of a new life on a new world can be an economic incentive. The real question, as I understand it, is can we make spaceflight cheap enough to turn a profit?

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      1. I’m curious where Musk or Zubrin make the economic case. I have to admit I haven’t read Musk at any length (just tweets and interviews). I have read a couple of Zubrin’s books, but can’t recall what he might have said about the economics, and finding my copies of ‘The Case for Mars’ or ‘Entering Space’ appears to be a lost cause.

        Myself, I think if we want to see the likely Mars scenario, we only need to look at the history of Antarctica. Despite far cheaper transportation, and a (relatively speaking) much more inviting climate, we only have research stations but no colonization, except perhaps for a few semi-permanent residents at the stations.

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      2. There’s actually a whole chapter in “Case for Mars” about the economy of a Mars colony. Zubrin’s basic idea seems to be that Mars is a convenient outpost for economic exploitation of the asteroid belt. Earth supplies Mars with technology and personnel, Mars provides fuel and food for missions into the asteroid belt, and raw materials from the asteroid belt are sent back to Earth. The historical example Zubrin uses is the “trade triangle” that made colonization of North America successful for the British (in his analogy, Britain is Earth, North America is Mars, and the West Indies are the asteroid belt).

        Going through the articles I have saved from Musk, I actually don’t see as much as I thought there was about specific economic incentives for colonizing Mars. I think he’s just saying that if trips to Mars were more affordable, then companies and universities would be willing to invest in their own Mars research projects, and maybe individuals would pay to go too. It would be sort of like what’s happened with cube-sats, where the cost of launching a small research project into low Earth orbit is now affordable for almost anyone.

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      3. Thanks! I totally don’t remember any of that from ‘The Case for Mars’, but I can’t find my copy and maybe it got added in the new edition. After all these years, probably time for me to pick up the Kindle edition and do a refresh anyway.

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      4. I find myself referencing it frequently. Of course Zubrin is trying to make his case in “The Case for Mars,” so the book can be pretty one-sided. But there’s still a lot of really good information in there.

        Liked by 1 person

  2. Where are these odds/probabilities coming from? Either it’s there or it isn’t. The chances are therefore either a hundred percent or zero. What does a 10% chance mean? Logically it means there IS life on Mars but it’s going to try to kill itself with a 90% chance of success before we find it. Seriously, why do people who don’t know anything try to make themselves look clever by plucking numbers out of the air?

    Liked by 1 person

    1. These are probability estimates, nothing more. I wouldn’t take the specific numbers too seriously.

      The point I’m making is that, based only on what we currently know, I believe there is a slim chance that we’ll find life on Mars. There’s a much higher chance that life did exist in the past, and that we’ll find fossils. And lastly, I believe that it’s almost guaranteed that life will exist there in the future, once humans start settling on Mars.

      These sorts of estimates are about setting our expectations. You’re right that life either does or does not exist on Mars. But we don’t know enough to say either way yet, so for now we can only deal in guesses and probabilities.


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