Life on Titan?

[whiterafter]

I was wondering what the community's position on life on titan would be.

I have a hard time believing that life couldn't have evolved on a moon with such a diverse range of places, lakes, etc, and a mostly non-toxic atmosphere, even if it's just microbes deep in a lake warmer than the surface..

What's your thoughts about this?

[Bill Phil]

It's probably microbes if at all. Possibly similar to earth's earliest life forms. Prokaryotes, and not much else.

[xenomorph555]

But where would then exist, not the surface for sure.

[SmartS=true]

There might be methane-based life in the lakes, but we have no idea.

[Bill Phil]

Methane-based would be carbon-based.

Maybe the Methane in the atmosphere is the waste of an organism?

[Kryten]

It's highly doubtful life could evolve in a non-polar solvent like methane; polar solvents support micelles which allow for increased concentration of potentially biogenic chemicals, whereas non-polar solvents don't. If there is life on Titan, the most likely place would be the purported subsurface water-ammonia ocean.

[Newt]

Well, we must admit that defining the parameters needed for the formation of life are highly uncertain. It seems unlikely that life could evolve in a puddle of methane, perhaps, but we really do not seem to know enough about it to say exactly what is needed for the formation. Sometimes when we see complex and powerful systems, we can attribute their success to any number of the myriad unique qualities of the environment of their formations. Sometimes these peculiarities are relevant, and sometimes not. It is difficult to state life's needs, when we only have really one example to analyze.

I highly doubt that the methane is the result of an organism, at least in significant quantities. At the least, it seems quite probable that it could have originated by other means, and pending a greater explanation or the discovery of life that could likely output the material in such quantities, it is most logical to suggest that really it has resulted by less exotic means.

As for how and where, again, there are a lot of things that have to go right in order to get life started. What has to go right is, however, an open question, so we cannot say whether anywhere on Titan is suitable, or define what we need to know to decide that question.We have not seen bunnies bounding across the surface, or anything else that screams out that life is there on Titan, so it is apparent that, in its form, if life exists on Titan, it is hidden or otherwise difficult to recognize, with the instruments we have used to investigate the area. There is still much that we do not know, and alas, it is extremely difficult to prove, beyond doubt, that life does not exist on an object the size of Titan.

[SpaceLaunchSystem]

Maybe not titan, but there might be very primitive life on Europa.

[KerikBalm]

I have a hard time believing that life couldn't have evolved on a moon with such a diverse range of places, lakes, etc, and a mostly non-toxic atmosphere, even if it's just microbes deep in a lake warmer than the surface..

Diverse geography doesn't really have anything to do with the probability of life. When studying biology, one needs to understand the implications of positive feedback loops, and the result is often "all or nothing". Positive feedback loops were certainly involved in abiogenesis, and if the conditions aren't sufficiently conducive, then the feedback threshold would never be crossed, and life wouldn't start.

I can't say what those conditions are, but I can easily believe that a place that is capable of *supporting* life may not be *capable of *starting* life.

As Titan's environment is not hospitable to Earth life, local panspermia wouldn't seed it with life. Thus, I have an easy time believing that life may not have evolved on Titan. I'm not saying it didn't, I'm just saying I wouldn't have a hard time believing that.

Heck, I'm even leaning towards Mars having never had life, despite its apparent habitability ~4 billion years ago.

It's highly doubtful life could evolve in a non-polar solvent like methane; polar solvents support micelles which allow for increased concentration of potentially biogenic chemicals, whereas non-polar solvents don't. If there is life on Titan, the most likely place would be the purported subsurface water-ammonia ocean.

Thats not really true.

In biological membranes on Earth, there is a polar/hydrophilic "head" and hydrophobic "tails". This results in the heads facing the water, and the tails facing each other, forming a double membrane.

In a non-polar solvent, this simply inverts - the non polar tails would face outward, and the polar heads would face inward.

At first glance, it seems feasible if the lipids are just inverted.

[K^2]

It's highly doubtful life could evolve in a non-polar solvent like methane; polar solvents support micelles which allow for increased concentration of potentially biogenic chemicals, whereas non-polar solvents don't. If there is life on Titan, the most likely place would be the purported subsurface water-ammonia ocean.

There are plenty of non-polar options. One of the reasons we need polar bonds for our life is "high" temperatures which we live in. You need strong, polar bonds to have molecules stay together at typical Earth temperatures, and that means strong, polar solvent to break them apart and rearrange them. At Titan's temperatures, methane is actually the perfect solvent. Granted, the metabolism rate at these temperatures won't be great, but that's why we don't exepct anything but the simplest bacteria there, if anything at all.

So far, everything I've seen on Titan indicates that the ethylene levels in Titan's lakes are much lower than we'd expect at equilibrium. Either something's metabolizing it, or there are some geological processes going on that we have no idea about. Either way, studying Titan should be very high on our list of priorities. I'd also label it as most likely place we know of to have life that has evolved separately from our own. While Mars is a more likely place to (have) harbor(ed) life, we'd be hard pressed to exclude cross-contamination with Earth, since life here and there would have to be pretty similar. With Titan, if we find life there, we'd know that life evolved on two separate planets in one Solar system. Having life on Earth tells us nothing. Finding life on Mars would be awesome, and we'd learn a lot from it. Finding life on Titan, though? That would be the holly grail of cosmology. We'd instantly learn not just that there is life elsewhere in the Universe. We'd learn that universe is absolutely teeming with it.

I'm not saying odds of finding life on Titan are great, but they are definitely not terrible. And given that finding life there would be by far the single greatest discovery we have ever made, I think it's worth checking. We can afford to send a few serious probes there, similar to what we've sent to Mars. And we'd be fools not to.

[lajoswinkler]

If anything alive exists there, it's not on the surface. The surface is at cryogenic temperatures and has nonpolar solvent which doesn't possess a fragment of versatility polar solvents as water have. Available chemical energy is the one in the compounds seeping down at extremely slow rates from the photolytic upper smog layer, and that's a tiny amount indeed. There aren't even hypothetical biochemical systems in such conditions. Just wild ideas from SF which aren't based in reality.

Any icy body of sufficient mass will have liquid icy layer beneath its surface. Aqueous solution of ammonia and other compounds will exist in liquid state in a relatively broad spectrum of temperatures and pressures. If there are microbes on Titan, they are way below the surface, enjoying the primordial heat remnants and swimming in aqueous solution. For example, psychrophiles, which optimal temperatures are close to 0 °C.

[KerikBalm]

If anything alive exists there, it's not on the surface. The surface is at cryogenic temperatures and has nonpolar solvent which doesn't possess a fragment of versatility polar solvents as water have.

As usual, you overstate the certainty of a statement, turning predictions into conclusions.

It may or may not be on the surface. Its cold, but there are still liquid solvents.

what is a "fragment of versatility"? Sure, water may be a more versatile solvent, but liquid hydrocarbons have their uses as solvents too. It remains unknown if a possible biochemistyr could work with them.

Available chemical energy is the one in the compounds seeping down at extremely slow rates from the photolytic upper smog layer, and that's a tiny amount indeed.

You don't need much, especially with any biological activity being at a slow rate as well due to the low temperature.

There aren't even hypothetical biochemical systems in such conditions. Just wild ideas from SF which aren't based in reality.

I don't know where you draw the line between "hypothetical" and "wild idea"

http://www.sciencedirect.com/science/article/pii/S0019103505002009

http://www.scopus.com/record/display.url?eid=2-s2.0-0036766102&origin=inward&txGid=AD2F5213BE80131BE76402B3D3642041.53bsOu7mi7A1NSY7fPJf1g%3a2

"Due to Titan's reducing atmosphere and lack of an ozone shield, ionizing radiation penetrates the atmosphere creating ions, radicals and electrons that are highly reactive producing versatile chemical species on Titan's surface. We propose that the catalytic hydrogenation of photochemically produced acetylene may be used as simple metabolic pathway by organisms at or near Titan's surface. While the acetylene may undergo this reaction, it can also undertake several other multi-step synthetic schemes that eventually lead to the production of amino acids or other biologically important molecules. Four model synthetic schemes will be described, and their relevance in relation to prebiotic evolution on Earth is discussed."

Any icy body of sufficient mass will have liquid icy layer beneath its surface.

Where did you get this wonderful idea? An icy body that formed long long ago, when the metalicity of the universe was low, will not have significant radioactive elements, and without a source of internal heat, even a body the size of the Earth would go cold on the order of tens of millions of years.

Sure you could take very high mass mass, and argue that it will retain primordial heat if it formed recently, or take a ridiculous mass and argue it will have a liquid core if it formed less recently... but this is more a matter of when it formed, rather than its mass.

To stay liquid for any significant length of time, it needs either tidal heating, or radioactive heating - neither of which will be there simply because of "sufficient mass"

[-Velocity-]

It doesn't matter how many lakes or rivers or oceans or rain clouds it has if all that liquid is not conducive to supporting the extremely complex chemistry that life requires. Our best guess is that liquid hydrocarbons do not. Not only do they not support the range of chemistry that water does, they exist at much colder temperatures so any chemistry would proceed slowly.

What is more exciting to me is the possibility that life could exist in the Titan's "lava" and "magma", which would be largely liquid water.

Any icy body of sufficient mass will have liquid icy layer beneath its surface. Aqueous solution of ammonia and other compounds will exist in liquid state in a relatively broad spectrum of temperatures and pressures. If there are microbes on Titan, they are way below the surface, enjoying the primordial heat remnants and swimming in aqueous solution. For example, psychrophiles, which optimal temperatures are close to 0 °C.

For pure water, it doesn't look like this is the case if there is no internal heat. I pulled the phase diagram for H2O from Wikipedia to illustrate-

In Titan's case, I believe we already have confirmed that the mantle contains huge amounts of liquid water. Titan has a big mountain, "Mount Doom", that is believed to be a large cryovolcano that erupts liquid water based "lava".

Edited January 13, 2015 by |Velocity|

[K^2]

The surface is at cryogenic temperatures and has nonpolar solvent which doesn't possess a fragment of versatility polar solvents as water have.

The only reason we need polar solvent are the hydrogen bonds in our proteins and DNA. The only reason we need these is because we live at 300K, and weaker bonds fall apart. At 90K, you need about 30 times less energy in the bond. Hydrogen bonds are too strong at these temperatures even with a polar solvent. At these temperatures you actually want non-polar bonds and a non-polar solvent to go along with them. This is Kinetics 101, seriously.

Methane is an ideal organic solvent for Titan's 90K environment.

[miracmert]

I agree with what K^2 says, we are pretty sure that a life form as we studied and observed on Earth would have possibly no chance to evolve on the surface of Titan, but we only have seen life on Earth. We have no idea if evolving&reproducing intelligence can form on a different environment, based on different principles/elements other than that which we have witnessed until now. Heck, we can't even give an absolute definition of life in our planet, I believe it would be arrogant to be sure of an only-closely-observed-for-30min moon to be inable to harbor a certain lifekind .

Edited January 14, 2015 by miracmert
sentences made much more sense now. What was I thinking about when I wrote this?

[Bill Phil]

Life can be defined as a type of machinery, taking an input, extracting energy, and then getting rid of wastes. That and reproducing. Even if their metabolism is slower, there would be a lot of Titan life by now.

[Technical Ben]

Saying there might be life at the bottom of Titan, is similar to saying there might be gold under there. We know how to find both, and we know the probability of both based on current observations (mass/gravity/surface/composition etc).

[miracmert]

Life can be defined as a type of machinery, taking an input, extracting energy, and then getting rid of wastes. That and reproducing. Even if their metabolism is slower, there would be a lot of Titan life by now.

You could define life like that, but viruses are not considered as living organisms even though they have a RNA and they reproduce and they are basically machines with intelligence. We cannot define life in an exact definition because we haven't seen such different examples of it.

**

I don't understand why there was only one mission to Titan which lasted 30 min on the surface with so little information been sent because of programming error on the probe. I understand it takes long to go there and it's considerably expensive mission but it is an interesting celestial body, only one with liquid lakes on the surface other than Earth, has a very similar atmospheric characteristic (not composition but physicalcharacteristics) to that of early Earth's, and would make so much difference in science to find anything close to life. Even if there's not life on the surface, still the moon itself is promising because of its interesting environment and water-lava.

Oh and also think about it, it would be so cool to live on Titan -as a natural local of Titan-. Seeing Saturn on the sky? Dayum!

[Kryten]

You could define life like that, but viruses are not considered as living organisms even though they have a RNA and they reproduce and they are basically machines with intelligence.

Virus' can't reproduce independently, they're dependent on host cellular machinery. If that's enough to qualify as 'alive' then chromosomes are living organisms.

[KerikBalm]

Humans can't reproduce "independently" either, we depend on microbes and food. We need more than just a carbon source, trace elements, and an energy source.

We can't synthesize everything we need (vitamins, essential amino acids, certain fats)

Its not a really clear distinction... especially with megaviruses and intracellular bacteria.

But he also used another term that has a tough definition... "intelligence" I would argue viruses are not intelligent. Intelligence and life are not the same thing (and viruses by most definitions are not life)

[miracmert]

But he also used another term that has a tough definition... "intelligence" I would argue viruses are not intelligent. Intelligence and life are not the same thing (and viruses by most definitions are not life)

That's exactly what I mean. Viruses are intelligent compared to a rock, sand or sea. But hey, there are also car which drive on the road itself, drones which will fly itself.. They are intelligent too, but they are not alive as far as we know. Intelligence is not the same with life, viruses have intelligence which enable them to hold on a host organism and insert their RNA/DNA into the nucleus but as Kryten mentioned they cannot reproduce independently, they must have a host cell to do so.

Virus' can't reproduce independently, they're dependent on host cellular machinery. If that's enough to qualify as 'alive' then chromosomes are living organisms.

Very good point, and it is another problem about defining "life". Would we consider sexual reproduction as dependent or independent reproduction? If one would think the reproducing bodies are the same of their kind therefore it would be considered independent, but another would say one body must need another in order to reproduce (well of course I'm not talking about bees or similar organism) which makes it another kind of dependent reproducement.

And as you said managing molecules -I do not know if this is the correct English phrase but I couldn't find a translation- are not considered to be alive since they don't have energy transformation, waste production, growth and so.

Edited January 14, 2015 by miracmert

[KerikBalm]

I don't think any of those examples qualify as intelligence.

As to sexual reproduction... the person may not be able to reproduce... but their cells can. We have cell lines from cancers of people that "died" long ago, yet part of their body continues to live and reproduce. Among caninines and tasmanian devils, we have examples of transmissible cancers -> basically a multicellular organism that evolved into a pseudo-unicellular pathogen.

Anyway, I think its a bit fun to think of the Y chromosome as a virus, and males as things infected by the virus

But its not that simple (in birds, the its the females who have two different types, and in many species, there are no ... chromosomes)

Another way of looking at a virus, is not to look at the virus particle, but the infected cell.

The infected cell is doing all kinds of metabolism, surely its alive... but the "genome in command" is the viral genome.

The infected cell is to the virus, as a man is to his (probably going to get autocensored) semen

*edit*... so S E X gets autocensored, even when not used to refer to *ahem* conjugal acts *ahem*, but semen is fine.... whatever...

[miracmert]

I don't think any of those examples qualify as intelligence.

As to sexual reproduction... the person may not be able to reproduce... but their cells can. We have cell lines from cancers of people that "died" long ago, yet part of their body continues to live and reproduce. Among caninines and tasmanian devils, we have examples of transmissible cancers -> basically a multicellular organism that evolved into a pseudo-unicellular pathogen.

Anyway, I think its a bit fun to think of the Y chromosome as a virus, and males as things infected by the virus

But its not that simple (in birds, the its the females who have two different types, and in many species, there are no ... chromosomes)

Another way of looking at a virus, is not to look at the virus particle, but the infected cell.

The infected cell is doing all kinds of metabolism, surely its alive... but the "genome in command" is the viral genome.

The infected cell is to the virus, as a man is to his (probably going to get autocensored) semen

*edit*... so S E X gets autocensored, even when not used to refer to *ahem* conjugal acts *ahem*, but semen is fine.... whatever...

Then what is intelligence I don't mean a virus or a car can solve a differential problem, but they do have intelligence, because an ordinary salt molecule cannot reproduce even dependently but a virus can. Computers do have intelligence, not naturally -and yes! That's why we call that artificial intelligence- and that's the reason why we are not using our table to play KSP instead of our couple hundred of bucks worth computer. When you examine DNA or RNA itself, it seems pretty stable and pretty unalive and also if you, let's say, observe a bacterium that does not have its managing molecules then it seems pretty unalive too. But when you combine them, boom! There is energy transformation/transition, growth, reproducement, waste production, substance consumption and all. So what I'm trying to say is that we know what life does, but we don't know what causes life to exist. A virus has a managing molecule, an isolated body but yet it can do anything with them rather then robotically transforming its genomes to an organism and making more of itself pointlessly.

Edited January 14, 2015 by miracmert
corrected sentences that didn't make sense grammatically

[Mr Shifty]

Perhaps life, like intelligence, is something that is best understood as a gradient.

While Mars is a more likely place to (have) harbor(ed) life, we'd be hard pressed to exclude cross-contamination with Earth, since life here and there would have to be pretty similar. With Titan, if we find life there, we'd know that life evolved on two separate planets in one Solar system.

I sometimes wonder if the Huygens probe was rash. We were so careful with Galileo to drop it into Jupiter's atmosphere to avoid any possible contamination of the Jovian moons. With Huygens, we blithely dropped a probe right down onto the surface of the most hospitable moon in the solar system.

Edited January 14, 2015 by Mr Shifty