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Is subsurface life possible on Titan (Saturn's moon) ?

Temperatures on the surface are way too low to sustain any life (<-150 degrees Celcius) but since there is some tectonic activity, I was wondering if there could be some oasis of life deep under the surface.

Is it realistic to imagine that it could reach complex multicellular stage, possibly sentient?

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  • $\begingroup$ Your question is contradictory: “methane based” would be colder than “water based” so if such exists then it is not too cold for life to exist. $\endgroup$ – JDługosz Nov 28 '16 at 7:02
  • $\begingroup$ Good point, I ll update my question $\endgroup$ – Fred Nov 28 '16 at 8:30
  • $\begingroup$ I will turn the question around on you: can you prove that life — any kind of life — on Titan is absolutely impossible? Since this is a binary problem, either it is possible or it is impossible, then if you eliminate one option the other one remains. And since you cannot prove that it is impossible, then it is possible. $\endgroup$ – MichaelK Nov 28 '16 at 10:12
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    $\begingroup$ @Michael that's not that simple. If you can't prove it's impossible, it's either possible or you are bad at proving. $\endgroup$ – Mołot Nov 28 '16 at 12:19
  • $\begingroup$ @Mołot Well all he needs to do then is find someone who can prove it is impossible. Do you think he can find such a person? ;) $\endgroup$ – MichaelK Nov 28 '16 at 12:27
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Yes life is possible

Life doesn't have to be limited to the forms that we know on earth. It also doesn't have to be limited to the temperatures that we know of on earth. My best argument is the presence of weather generated terrain feature on Titan. Titan has a methane-ethane cycle, similar to the water cycle on earth. There are hydrological features like lakes and river; vast dune seas of ice crystal sand grains coated with methane snow; monsoon storms that travel north and south across Titan's surface as the seasons change.

No one really anticipated that kind of weather would exist in a world that is too cold for liquid water, because water is the dominant liquid on our world. So in that light, who is to say that another form of life cannot form with methane as its primary solvent instead of water? We don't know if there is life on Titan, but we can easily imagine that there could be.

If you want any more info on possible methane based life you can search this site or google.

Sentient life as we know it has some problems

While we can assume that life is possible (if not probable), there are some problems with assuming sentience as we understand it. Life on earth is energetic, and it is energetic because the earth is relatively warm. Titan is relatively cold. Chemical reactions, the basic reactions that provide energy to living beings, will happen much more slowly on Titan. No matter what metabolic processes you choose, it is inevitable that the rate of energy consumption is much lower for any creature on Titan.

A rule of thumb for chemistry is that at room temperature, 10 C doubles the reaction rate ($k$). If we apply that to Titan which is about 150 C colder than earth, the reaction rate goes down by a factor of about 32,000. Obviously, this is not rigorous, but it does show the challenges that life on Titan would face, and makes the equivalent of a human brain very hard to imagine on Titan. If chemical reactions go 10,000 times slower, we could assume that a creature would need a metabolism 10,000 bigger than a humans to sustain a brain. That is a 10 blue-whale sized organism.

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  • $\begingroup$ Or think 10 thousand times slower. $\endgroup$ – Tim B Nov 29 '16 at 16:36
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Yes, it is possible that life could form on Titan, but the question is on which level.

  • Is life possible on Titan at all? Yes, most likely.
  • Is advanced, multicellular life possible on Titan? Potentially, but probably not.
  • Is sentient life possible on Titan? Who knows. Not the way we know it, but we don't really understand what it really means to be sentient either. Is an ant colony a somewhat sentient hive-cluster? Are our pets sentient? Are humans really sentient? We're still researching it.
Can life actually start on Titan?

The current understand we have of life is that of our own, which requires some sort of "source code" (DNA, RNA) to be kept in discreet packages (viruses, cells) and that those packages can transfer their source code in order to reproduce. We initially believed that only very limited conditions would allow such system to start, but have later come to realize that it might be so that "life" can start in very extreme conditions. There are ideas of panspermia, which states that life on earth might have developed elsewhere and then been transferred here to earth through meteorites (or even aliens...). Whether this is true or not is up for debate, but we have seen that there is a lot of organic molecules forming in interstellar dust and it is, therefore, highly possible that the first nucleotides were formed in space and then "rained" down on Earth and, thus, on other celestial bodies. Another point is that we currently only know that nucleotides works as building blocks for the "source code" for life, but there might be other molecules that can do the same thing which we yet have discovered. That is, even if Titan does not allow the initial conditions for life as we know it, it might have formed outside of Titan, rained down and then managed to undergo abiogenesis, or other molecules have developed which does the same thing.

Any type of life on Titan?

There are several examples of extremophile microbial life on earth, which ranges from the interior of nuclear reactors, next to hydrothermal vents at the ocean bottom, possibly down in the Mariana Trench, in subterranean lakes half a mile under the Antarctic ice, inside rocks, etc. The conclusion from earth is that as long as life can start, then it will find a way to survive even the most bizzare conditions, and Titan might be bizzare but (probably) not too extreme. There are suggestions that Titan, if there are "warm" enough regions (>-97°C), contain liquid water thanks to the presence of ammonia. This would simplify life conditions as we know life can develop in extreme water conditions if it has started.

Multicellular life on Titan?

Potentially. Some of the extremophile life on earth are multicellular, such as the pompeii worm and the Antarctic krill. Sure, those live at far warmer conditions than what Titan allows, but they show that relatively advanced life can form in extreme conditions.

Sentient life on Titan?

I understand your question as "can something big, self-aware, and potentially human like develop on Titan", I personally believe that the answer is "no", but I might be wrong; especially since we do not really know which creatures that truly are self-aware, nor even if we humans are fully sentient. Without going into the debate about what it is to be self aware or sentient - there are research which indicates that humans are essentially just moist robots whom believe they are sentient (Wikipedia lists a bunch of interesting reading in the article "Neuroscience of free will"), then there are those philosophers whom states that believing to be sentient is the same thing as being sentient (René Descartes). Of course the research is debated and highly criticized, my point is simply that we do not have a good definition of what it really means to be sentient. As I mentioned at the start, an ant colony might be a somewhat sentient and self-aware life form even though each individual ant might not be. And, to make it even more weird, it turns out that plants might be talking to each other. Who knows, if there is a sea of krill like creatures under the ice on Titan, then they each might be acting as individual neurons in a giant brain which covers the entire moon.

Completely alternative way of life on Titan

James P. Hogan wrote the book "Code of the Lifemaker", in which life developed on Titan thanks to an automated mining ship from an alien race which crashed on Titan. The automated ship was damaged and started to produce robots which deviated from the original plans, which later led to that a form of evolution developed as some robots started to eat other robots. This evolution led, in turn, to the production of sentient robots. While this is extremely unlikely scenario, it was still an interesting book to read.

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  • $\begingroup$ Thanks, I ll try to read "Code of the Lifemaker", it looks like a very interesting book! $\endgroup$ – Fred Nov 29 '16 at 0:16
  • $\begingroup$ Antarctic krill aren't considered extremophiles. $\endgroup$ – kingledion Nov 29 '16 at 0:35
  • $\begingroup$ @kingledion The wikipedia article about Antarctic krill does not explicitly state that the species is an extremophile, however, they are mentioned on the wikipedia page about extremophiles and the book "Extremophiles, Volume II" (Gerday and Glansdorff) list them since their digestive enzymes work remarkably well in cold temperatures. I guess their status as true extremophiles can be debated since the definition of an extremophile is somewhat vague. They thrive in an environment with a P range between 1-300 atm and T fluctuations between -1.3 to +4 °C, which is not something all organisms can. $\endgroup$ – Mrkvička Nov 29 '16 at 15:55
  • $\begingroup$ An excellent answer :) $\endgroup$ – Tim B Nov 29 '16 at 16:39
  • $\begingroup$ @Fred James P Hogan has written some really interesting and thought provoking books - some of them showing remarkably accurate predictions for technological progress.... some of them not so much :) I recommend the Giant's Trilogy, Voyage from Yesteryear, The Two Faces of Tomorrow and The Genesis Machine in particular. $\endgroup$ – Tim B Nov 29 '16 at 16:41

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