What might cell membranes look like on Titan?

[Jimster41]

I keep hearing how Titan, is somehow more analogous to a "tropical" climate - though in a wholly different temperature domain, as well as, at least to my understanding, a very different domain in terms of elemental distribution. I have been interpreting that sort of literally, like maybe it's a veritable "jungle" of emergent complex systems. This has left me wondering if there could be periodically distributed physical-chemical pathways of differing resistance to emergence as a function of those two scales (temperature, elemental distribution). So that some combinations of elemental distributions and energy flows have very low resistance to emergence, while others have very high resistance. Or on the pessimistic side, that there are bands of obstructions to emergence that span that space, like a very small set of functional solvents for any and all possible combinations.

Someone mentioned superconductivity above, which seems really interesting. Maybe the "cell membranes" on Titan are boundaries of pure electrical conductivity, in a hydrocarbon ice substrate... or something. Like, Live-Ice-Nine.

Edit: I did read on wiki that researches have at least seen amino acid production without water, when energy was applied to gases like those in Titan's atmosphere. There are some pretty interesting/amazing quotes from Astrobiologists on the wiki, w/respect to the expected effect on atmospheric composition if methanogenic "life" were or weren't present.

 

[Arsenic&Lace]

The membranes might appear to be promising, but I'm still skeptical about whether this could allow life to exist in non-aqueous environments or not. For one thing, I can't imagine the secondary and tertiary organization of polypeptides with hydrophilic R groups in the amino acid residues. All globular protein (i.e. all enzymes) will essentially be forced to turn "inside out". Permanent dipole interactions between non-polar molecules will be virtually non-existent, and this means that most metabolic reactions simply cannot occur ( most probably because organized dipole forces help in reducing the activation energy of these reactions). Yes, life might exist in the presence of some other polar compound, but I feel there is little hope with hydocarbons.This is of course what I suspect, and my conjectures might be prone to errors since I don't really hold a graduate degree in microbiology.

Why would a protein analogue need to be built from traditional amino acids? I'm no biochemist, this is a genuine question.

 

[rootone]

Why would a protein analogue need to be built from traditional amino acids? I'm no biochemist, this is a genuine question.

You do need to have something capable of forming very long chains and the ability of traditional proteins to fold into complex geometries is often essential to their function as well.
Thus doesn't rule out other possibilities altogether but amino acids are ideal components for the job, and they are known to form naturally in certain conditions that are not particularly rare or unlikely.

 

[Arsenic&Lace]

Nothing other amino acids is known to do this? I know I can't think of man-made polymers which are quite like proteins. I know that synthetic amino acids have been produced however.

 

[rootone]

Yes one can imagine other candidates, but amino acids occurring naturally - that they are extant in the universe anyway without requiring very special conditions - this does increase the likelihood of life processes taking advantage of their properties.

Nylon type polymers could be in theory good stuff for making a cell membrane, but it's hard to imagine a realistic situation that could lead to this.

 

[Arsenic&Lace]

Intriguing. I wouldn't be surprised if water turns out to be the de facto solvent of life. Why is it so difficult to probe alternative chemistries? I can see where the forcefield parameters for abnormal chemistries may be poor, and we can't even fold most terrestrial proteins much less a protein composed of an entirely new chemistry, but that's all computationally. Empirically I would think things might be different.

 

[Jimster41]

This is clearly all speculation, but it's fun speculation, and for me at least as well as others probably, a part of the learning process - particularly because it keeps the excitement of imagination in there to lubricate the real (hard, dry, and unforgiving) science... which is of course, work that must get done.

Although it allows the outcome of whatever thermodynamics might build from alternative "cells" to drift farther from anything humanoid, it seems to me like the question should start with things like - What are the minimum functional requirements of a humanoid "eukaryotic?"cell? How tied are those to the physical chemistry they evolved in? What alternative construction paradigms, if any, given different chemical contexts (like Titan), could achieve comparably outstanding entropy production? Is rate of entropy production, or something similar a good metric for assessing the "complexity carrying capacity" of various physical chemical dynamics. Is complexity, or some sort of energy flux density a good general description of what we are looking for when we look at the stars and mutter "life?"

At the end of the day ours could be the only, best one, but it seems a strange set of constraints with which to start.

Also I think the question mentioned above about how computational exploration may be harder or easier than actual exploration of the configuration space of the periodic table over time and energy integrals, is a great one.

 

[Arsenic&Lace]

Well the reason I want to do science is because it's fun, even if it involves lots of grueling debugging, disappointing failure, and grant writing. So speculate away.

I wonder if potential entropy production can be deduced in some way from the chemical composition and thermodynamic conditions of a system. Jeremy England has papers for generic physical systems on similar topics IIRC.

I think if good progress could be made on critical dynamics and rationally parameterizing forcefields computational exploration would be viable, but at present both problems seem stubbornly out of reach.

 

[rootone]

Yes, but you would want to be clear about what is computationally possible, and actual repeatable measurements.
I guess that's why there are theoretical scientists and experimental ones though, nobody gets it all their own way.
I certainly will not rule out the possibility of life forms defined by nylon shell.
In fact I saw a few walking through my local town yesterday.

 

[Jimster41]

I'm reading this paper by England now, forwarded to me by @techmologist.

http://www.englandlab.com/uploads/7/8/0/3/7803054/2013jcpsrep.pdf

his derivation of non-eq 2nd Law reminds me of the language of evolutionary dynamics. I think it's correct to say he is defining the entropy of the "heat bath" containing an organism with potential microstates, to be the conserved quantity from which the fitness function (probability of propagation, or durability) of those microstates is derived. This seems pretty elegant... and sort of simple.

[Edit] It looks like that is more attributable to G.E. Crooks

https://www.amazon.com/dp/0674023382/?tag=pfamazon01-20