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Posted by: jaredGalen Jul 24 2005, 02:13 PM

Thought this article title was a little over the top, the kind of one you would
expect to see followed by lots of exclamation marks.

Interesting article though.

"IF LIFE exists on Titan, Saturn's biggest moon, we could soon know about it - as long as it's the methane-spewing variety. The chemical signature of microbial life could be hidden in readings taken by the European Space Agency's Huygens probe when it landed on Titan in January."

http://www.newscientistspace.com/article.ns?id=dn7716

Posted by: exoplanet Jul 25 2005, 12:58 AM

I have always thought that even though the outer planets and moons are very frigid - if there is an abundance of hydrocarbons, water and ammonia with some "energy" either internal or external - life is possible.

I think that we focus too much on "life as it is on Earth". Thinking outside of the box in the case of Titan may perhaps be prudent. There is abundant hydrocarbon molecules (think octane!! - most of the hydrocarbon molecules found on Titan are discussed at length in in undergraduate organic chemistry!!!), water, ammonia and a possible internal heat source.

I would love to hear more about the organic chemistry going on at the Titan surface and atmosphere. The only way the geologists are going to find out what is going on at the surface is to understand what is going on at a molecular level and then build from there.

Posted by: deglr6328 Jul 25 2005, 03:15 AM

New Sensationalist publishing unverified highly speculative to the point of being ridiculous sotries?! I'm shocked!

Posted by: JRehling Jul 25 2005, 03:32 AM

Frankly, despite the sometime exuberance over various astrobiological possibilities, we don't have anywhere near the ability to predict what is possible. If we didn't have the "reverse engineering" information we have about how "life as we know it" is possible, we would be nowhere NEAR predicting LAWKI starting from first principles. Ergo, we're not going to be able to predict other chemical bases for life in any complete, detailed, or meaningful way if/until a whole new level of complexity becomes within our means to predict. We may never get to that point.



The distance from the molecular level to anything nearing a viable organism is a gulf that we are nowhere near bridging. Consider that some of 2004's top ten scientific discoveries (as rated by AAAI) concerned the chemical properties of WATER. If we don't yet understand H2O inside and out, forget about predicting life given some alternative chemical basis.

To put a spotlight on the problem, consider that a water molecule essentially consists of 15 particles, and so a pair of water molecules involves up to 435 interactions. Create a computer model of those two water molecules, and you have a lot of math to juggle. Fine, that's tractable, but make it 100 water molecules, and forget about it (although, admittedly, you could make simplifying assumptions -- not all of those interactions will amount to much). So simulating a water nanodroplet is a big task. This just goes to say that "brute force" computation cannot be the bridge between molecular chemistry and a hypothetical new kind of biology. And if water still holds secrets, you can see that no more-burly kind of chemical theory is in hand yet.

This area will be observational science, not predictive science, for some time.

Posted by: exoplanet Jul 25 2005, 05:05 AM

I quote JRheling:

"Consider that some of 2004's top ten scientific discoveries (as rated by AAAI) concerned the chemical properties of WATER. If we don't yet understand H2O inside and out, forget about predicting life given some alternative chemical basis.

To put a spotlight on the problem, consider that a water molecule essentially consists of 15 particles, and so a pair of water molecules involves up to 435 interactions. Create a computer model of those two water molecules, and you have a lot of math to juggle. Fine, that's tractable, but make it 100 water molecules, and forget about it (although, admittedly, you could make simplifying assumptions -- not all of those interactions will amount to much). So simulating a water nanodroplet is a big task. This just goes to say that "brute force" computation cannot be the bridge between molecular chemistry and a hypothetical new kind of biology. And if water still holds secrets, you can see that no more-burly kind of chemical theory is in hand yet."

Thank you for your post. It is conceivable that if we do not know all the properties of water . . . how in the heck do we know what the limitations of life is. I am by no means from the astrobiological mindset, however, I do believe that from what has been discovered both from Cassini and Hyugens . . . a more complex probe/rover would be a highly rewarding endeavor for both NASA and ESA.

I would love to begin some very heated discussions about the surface and atmospheric chemistry of Titan and the implications to the possibility of life pro and con. It is already being discussed in some important scientific journals and I would like to begin the discussion here as well (Also, I don't have the $ to subscribe or a nearby university to access most of the recently published articles).

Posted by: dvandorn Jul 25 2005, 07:47 AM

The way you phrased that is interesting, since my argument is about heat.

If life exists on Titan, it would have to be adapted to very, very low temperatures. To the extent that any probe or rover we send to the surface of Titan would be considered "superheated" and would pump a not-insignificant amount of heat into the local area around the probe.

Thus, I think you could expect any terrestrial probe searching for Titanian life would kill any such life before it could get close enough to even look at it. Not only kill it, but possibly force it into such rapid decay that nothing recognizable as ever having been alive would ever be observable.

So -- for the sake of this thread, I offer the hypothesis that we cannot settle the question of Titanian life, because looking for it will destroy it utterly -- and that this raises serious ethical concerns over any such attempt.

-the other Doug

Posted by: alexiton Jul 25 2005, 10:38 AM

Howdy Titanauts,

Isn't life more about organisation and interaction lending ability to recapitulate self with variation irrespective of wot mediates it?

Instead of room temperature chemical,polar/hydrogen bonding mix as the foundation for complex structural organisation typically used by life, why couldn't some heavy duty organisational weirdness via weaker hydrogen/polar,van der waalian interactions at cryonic temps be a tenable alternative biologically on Titan?

Surely the integrity of many interesting and delicate states yet manifested labside or just unobserved out of seeming irrelevance, are much enhanced by low temps to the point of being a viable scaffold for information loops amenable to evolutionary processes.

In fact, wouldn't such cryobiological states from thermodynamic point of view with lower constraints on dissipating entropy be able to more efficiently leverage energy gradients relative to corrosive tumult of water based chemistries?

Sure, biologically Titan is likely a right dud if you facily attempt some anthropocentric appeal on the basis that average covalently bound macromolecule represents some rote uncontestable biological truth. But personally, I would wouldn't be suprised at all if Titan represented some sort of revolution in terms of biological thinking...



Cheerio

Posted by: Myran Jul 25 2005, 03:43 PM

Yes, the Titan life forms would literally run for their lives if a human spacecraft landed there hot as a furnace from their viewpoint. Run?? Yes, at crygenically slow speeds!
Seriously, the kind of measurement mentioned in the New Scientist text are but one that could be utilized, another would be the scooping up of surface material and look for waste products and the molecules that might be from dead organisms themselves and so getting some insight in their makeup. Liquid nitrogen chilled microscopes are just one possibility and any remote sensors would be non leathal to whatever might be there.

As for ethics; Call me a Titanut (Abb: nut of titan-ic proportions) but today I must have smashed a dozen insects against the windshield of my car and possibly commited a genocide on one or several kinds of bacteria by simply breathing - and have no ethic conflict about that!

Edit: No I dont think there are any life on Titan, but a place very much worth of investgating for the precursor-to-life chemistry that many scientists think could be found there.

Posted by: mike Jul 25 2005, 07:07 PM

If there was widespread concern about killing life with a 'super-hot' Earth probe, I'm sure scientists and engineers could devise ways to shield life from too much danger. If nothing else a probe could hover far above everything, so far away as to have no effect, though I'm sure such a technique would result in less detailed results..

Posted by: JRehling Jul 25 2005, 11:01 PM

Rehling, but lots of people like to move the H!



A fascinating (and speculative) topic is the issue: Given a planet with appropriate conditions (for life as we know it, or LAWIK), what is the probability that life will actually arise? Internet posts and books can be found postulating (or arguing, or hoping) that the number is very close to 1.0. (Of course, the definition of "appropriate" is a wildcard!) If I had to make a guess this instant, I would say the opposite, something very close to 0.0. But some basic key facts are:

a) We have no unbiased data. We know of one case of biogenesis, but that data point stems from the same basic fact that we are here to make that observation! This is the anthropic principle at work.

We have a merely-kinda biased data point in that life on Earth seems to have arisen very quickly -- it didn't just dawdle around and then suddenly happen at some time in the middle of Earth's history. Or did it? It's not quite a solid fact when life could have arisen. And in any case, if life on Earth could have arisen at any old time, but it happened to arise, say, in the first 1% of the time that it possibly could have, that is merely a suggestive finding -- not proof. There was a 1% chance it would have done so anyway. In fact, more than 1%, because we wouldn't be here to talk about it if biogenesis of bacteria had happened only a million years ago.

c) It doesn't happen VERY fast. You can't throw the right nonbiological compounds in a bucket for an hour and get bacteria to evolve. It doesn't happen in days, or weeks, and probably not in centuries. But with a bigger bucket? A Pacific Ocean sized bucket, and a million years? What about a thimble and a trillion years?

Let's try this model: Given a quantity of soup, and a span of time, how great does the product of those two numbers have to be for life to arise? We might guess that given twice the bucket size, we could expect life in half the time. This model is valid if biogenesis consists of enthalpy's little fingers twirling organic molecules like Rubik's Cube, "trying" to create biology and succeeding when the correct sequence occurs by chance, which is inevitable given enough molecules in enough oceans over enough time.

Is that a correct model? Surely on some level, but tempered by modularity. Life did not arise when the molecules making up a raccoon or a pine tree randomly fell into place. The cell was an intermediary step from which natural selection could proceed, and surely there are subcellular intermediate steps as well. But still, something had to arise that crossed the natural-selection barrier. This process is not well understood.

To work with a simple model, I took the random-compilation model and assumed that biogenesis took place when M molecules were placed together in the right linear sequence. In other words, if biogenesis were the sorting through of M! (M factorial) permutations, until the right one were found. Then, for planet-like values of ocean-bucket volume and geological time, what is the probability of biogenesis as a function of M?

That's surely not literally accurate, but the mathematics were instructive. If M were 2, then biogenesis would take place in a thimble in a fraction of a second. If M were very very large, biogenesis would take place in very vast space and very vast time. The question is, how does the probability of biogenesis (some of the key values of Drake's Equation) vary as a function of M? We don't get to alter M, the laws of biochemistry have determined it, but it is still interesting to see how Drake's Equation might depend upon the inherent laws of the universe.

The answer is, the probability (Pl) of biogenesis on a planet given a few eons is very near 1.0 for low values of M, and then as M grows it very abruptly switches to near 0.0. The switchover happens somewhere around 55 (to cosmological standards of approximation, the exponent you'd use to express the number of molecules in an ocean times the number of molecule-manipulations you'd have in an eon).

This is so based on speculation that no conclusions can be drawn, but it seems quite reasonable to me that biogenesis is a freakishly rare event -- lacking a way to clean up all of my questionable assumptions, we still get a basic truth -- if the number of elements in the minimum requisite biosufficient "thing" is less than about 50, the galaxy will be full of life. If it's more than about 60, we may be totally alone -- not one stinking bacterium in all the galaxies anyplace farther away than Voyager 1!

Posted by: Jeff7 Jul 26 2005, 12:57 AM

Concerning the potential problem of a "superheated" probe roasting Titanian life forms before getting a chance to look for them, how about a sort of long-range microscope? It'd require one damn big main collector lens to get enough light, and the lander/rover would still need to keep that section cooled, but it might allow for getting a high-res look at something, while still keeping enough distance to avoid thermal damage to a subject.

Posted by: exoplanet Jul 26 2005, 02:27 AM

Hello All,

Great posts and thanks for the contribution - JRehling:) Sorry about the spelling btw.

What I find quite fascinating is here we have a rather large moon with a great deal of internal heating going on. The heat is probably the reason Titan has such a thick atmosphere of Nitrogen, Methane and from the slight energy of the sun - a great deal of complex hydrocarbons The New Scientist article is very, very interesting from the aspect of the "surface" of Titan. The possiblity of absent complex hydrocarbons at the surface really would make the case that "something" is removing them other than mechanical means. If methane rains out only infrequently (in some places possibly decades between rains) due to seasonal "monsoons" then Huygens should have found concentrated amounts of heavy hydrocarbons that had not been washed from the surface. Or if the probe landed in a playa type environment - the tholins should have been detected.

Btw . . I had heard that a number of results from the Huygens probe were to be released by May or June at the latest . . . No word yet from the primary researchers so why the delay?

The cold surface and high heat of a probe or lander does not bother me in the least with regard to exploration. Only when a craft first lands (and heated by the it's descent) would the surrounding immediate surface be affected. With good insulation of the internal heating of the craft ~ the effect should be nullified over a short period of time. If the craft is a rover - the effect of landing heat should be negligible over time.

Posted by: AndyG Jul 26 2005, 09:03 AM

Firstly, on the anthropic principle: over recent history, the position of humans has been displaced by science and intelligent thought. For example, we've discovered that we're not at the centre of a finite universe (whose planets move in circles and are pushed by angels), the Sun isn't the only star with planets, our species isn't the be-all-and-end-all of all evolution... Science tends to work against the inate biases of anthropicism, and is (supposedly) designed to take a more objective viewpoint.

Work relating to Earth's pre-biosphere suggests that life started amazingly early...and perhaps even more than once. Consider: 4GA ago solar output was (what? 30%?) lower than it is today, the planet was bathed in UV, the centre of some extraordinary impact events, and yet life started in what, in geological terms, is almost the blink of an eye. I therefore have to take the alternative, much more optimistic view: if the processes that lead to cellular life get a chance, and the resources are available, then it will occur. On Earth or anywhere. Without a doubt in my mind. Sign me up for a low "M". ;-)



I can turn that around. Yes, there is an anthropic principle at work here, since we (as the intelligent species that does science) can study Earth's early history to some level. But there is nothing to particularly argue against the possibility that intelligence (with all its negative evolutionary costs regarding brain size & power, relative weakness in infants, etc.) could have arisen 50 or even 500 million years ago if evolutionary paths were different, and done the same thing. The indisputable fact is, when you look back in time and disregard the details and time taken for the soup-intelligence transition, life started in the few million years that conditions first allowed it to. That 1% chance you see as "luckily coming up" could (I'd even argue "should") be viewed as: life appears to be an inevitable byproduct of basic chemistry in any suitably large environments.

I would be much more pessimistic if the geological record showed (for example) a half billion years of "nothing much" before the soup-stage. But it doesn't.

(This is naturally a factor siezed on by panspermia-lovers. Personally I feel that space might be a good source for plentiful organic molecules, but nothing much more advanced than that. Life needs water. Water requires gravity and pressure.)



Not necessarily. The conclusions you can draw are:

A: M is low and there is inevitability.
B: M is higher and we are a statistical freak.

Our admittedly single-point data suggests inevitability. Which seems as reasonable to me as freakishness does to you! This probably means, in your model, that (for the Earth at least) M is low, or (more likely) comprised of numerous sub-factors whose independent M-lettes are low.

Obviously the only way to answer this question (and for the first time in human history we might be on the verge of doing this) is to widen our range of datapoints. Missions to Mars, Europa and the Venusian atmosphere to specifically search for life are (I'd argue) essential. A TPF in orbit in the next couple of decades would be good too!

Andy G

Posted by: JRehling Jul 26 2005, 05:04 PM

[quote=AndyG,Jul 26 2005, 02:03 AM]Firstly, on the anthropic principle: over recent history, the position of humans has been displaced by science and intelligent thought. For example, we've discovered that we're not at the centre of a finite universe (whose planets move in circles and are pushed by angels), the Sun isn't the only star with planets, our species isn't the be-all-and-end-all of all evolution... Science tends to work against the inate biases of anthropicism, and is (supposedly) designed to take a more objective viewpoint.

[/quote]

Two things. One, of course, this sort of trend-analysis is suggestive, but not evidence. The facts that we once thought that the Earth was the center of the universe, and that it turned out not to be the case doesn't mean that it is impossible for the Earth to be unique in some other way.

Two, even so, on this level, the track record is not unidirectional from mankind-is-special to mankind-is-just-another-germ-on-just-another-rock. I can think of two dawning relevations that tilt the other way. One, the quantum mechanical fact that observers (in any case we have to latch onto, humans) can actually alter the outcome of an event by passively observing it -- this is still not understood, and would surely (?!) work just as well if some alien intelligence were the observer, but it still shows that we have a role that is more special than if a lump of dirt were in the lab in place of the scientist. This is still shocking to contemplate, and does work counter to the general trend you describe. In addition, the speculative paradigm regarding extraterrestrial intelligence had cause to wane, not wax, from 1900 to 1976. From the 17th through 20th centuries, sober individuals opined that places like Venus and Mars were appropriate hosts for civilizations and that numerous unknown planets would surely be the same, but the more we have gathered evidence from our solar system, the more we find that "earthlike" is a rare quality out there. Even with the Huygens landing, our discovery of channels coincided with the glum realization that the equatorial dark areas, which betting people might have guessed were seas, are remarkably Venus-looking rock-on-sand plains.

Of course, those two observations do not directly impinge upon the Pl question, but neither do heliocentrism, etc. Trends are just trends, and my only point here is, if nature is "trying" to foreshadow the answer to the Pl question, she is being a good mystery writer; there is foreshadowing on both sides.

[quote=AndyG,Jul 26 2005, 02:03 AM]Work relating to Earth's pre-biosphere suggests that life started amazingly early...and perhaps even more than once. Consider: 4GA ago solar output was (what? 30%?) lower than it is today, the planet was bathed in UV, the centre of some extraordinary impact events, and yet life started in what, in geological terms, is almost the blink of an eye.

[/quote]

That's not quite clear. The problem is, we have a subtraction to perform with two uncertain numbers: When did life arise, and when could it have. The uncertainty surrounding each number is pretty small, as a percentage, but because we're subtracting, the uncertainty surrounding the result is orders of magnitude. See for example:

http://www.livescience.com/forcesofnature/050505_early_earth.html

It is credible that the Earth became habitable 4.2 or 4.3 GYA, with life not forming until 3.8 or 3.9 GYA -- and it is therefore credible (I'm not saying probable) that biogenesis here took 500 million years of random molecular combinations. If so, that's up to 11% of the time-since-creation, which casts doubt upon the notion that life started as soon as it could have. Admittedly, I chose the most extreme values to get that 11%, and the lowest value is arbitrarily close to 0% -- but we don't know. The math I laid out before suggests that either the real number was very close to 0%, or life is a pretty chancy thing, and if it's chancey, that's not far from saying (in terms of M) that it is almost miraculous.

[quote=AndyG,Jul 26 2005, 02:03 AM]I therefore have to take the alternative, much more optimistic view: if the processes that lead to cellular life get a chance, and the resources are available, then it will occur. On Earth or anywhere. Without a doubt in my mind. Sign me up for a low "M". ;-)
I can turn that around. Yes, there is an anthropic principle at work here, since we (as the intelligent species that does science) can study Earth's early history to some level. But there is nothing to particularly argue against the possibility that intelligence (with all its negative evolutionary costs regarding brain size & power, relative weakness in infants, etc.) could have arisen 50 or even 500 million years ago if evolutionary paths were different, and done the same thing.

[/quote]

The rise of intelligence is another matter, of course, and it's an interesting fact that vertebrates seem to have made such faltering progress towards it. The dinosaurs don't seem to have made moon landings despite tens of millions of years of having had nontrivial brains.

[quote=AndyG,Jul 26 2005, 02:03 AM]The indisputable fact is, when you look back in time and disregard the details and time taken for the soup-intelligence transition, life started in the few million years that conditions first allowed it to. That 1% chance you see as "luckily coming up" could (I'd even argue "should") be viewed as: life appears to be an inevitable byproduct of basic chemistry in any suitably large environments.

I would be much more pessimistic if the geological record showed (for example) a half billion years of "nothing much" before the soup-stage. But it doesn't.

[/quote]

Well, it may have been half a billion years. We don't have a clear word on that yet, and whether it was half a billion or half a million, that enormous difference would only impact modestly on what it means for M, and we surely don't have the tools now or later to rule out the half-million-years possibility.

[quote=AndyG,Jul 26 2005, 02:03 AM](This is naturally a factor siezed on by panspermia-lovers. Personally I feel that space might be a good source for plentiful organic molecules, but nothing much more advanced than that. Life needs water. Water requires gravity and pressure.)
Not necessarily. The conclusions you can draw are:

A: M is low and there is inevitability.
B: M is higher and we are a statistical freak.

Our admittedly single-point data suggests inevitability. Which seems as reasonable to me as freakishness does to you! This probably means, in your model, that (for the Earth at least) M is low, or (more likely) comprised of numerous sub-factors whose independent M-lettes are low.

[/quote]

I agree that we face these two possibilities and are currently stymied as to which has the evidence its way. We can demonstrate a lower bound on M by doing the "bucket" experiment, but we're left only saying that M must be more than 30 or something. (Avogadro's Number times a large number of interaction-opportunities.) My high-M guess is only a guess. But you must admit, it's a little dicey to stipulate that M is between 30 and 50 when all we know is that it's greater than 30.

[quote=AndyG,Jul 26 2005, 02:03 AM]Obviously the only way to answer this question (and for the first time in human history we might be on the verge of doing this) is to widen our range of datapoints. Missions to Mars, Europa and the Venusian atmosphere to specifically search for life are (I'd argue) essential. A TPF in orbit in the next couple of decades would be good too!
Andy G

[/quote]

Indeed, it is possible that, eg, a Europa ocean probe could definitively answer the Pl question! Not only in the positive (if life could be found and proven to require a separate biogenesis), but even in the negative (if it could be shown that such an ocean was a suitable habitat, but was nevertheless lifeless). That is, a negative result could give us a value of M that wouldn't quite prove the universe lifeless, but would give M a lower bound close to the value that would mean the universe is lifeless. Possible oceans of giant planet satellites probably give us our only chance to set a lower bound on M, while any test for the existence of a separate biogenesis would answer the question the other way.

It has been noted elsewhere that if we find life on Mars, it may tell us nothing philosophical if it turns out to have shared biogenesis with terrestrial life.

Posted by: mike Jul 26 2005, 05:21 PM

I think life automatically arises on any body with sufficient input energy, sufficiently differing matter, and sufficient time, and guess what, I'm 100% right and everyone knows it!

Posted by: volcanopele Jul 26 2005, 05:42 PM

I take the middle ground really, basically that it is difficult to get life going but easy to keep it around once it has gotten started.

Posted by: JRehling Jul 26 2005, 08:13 PM

That's definitely right! Now, what is "sufficient"?

Posted by: Bob Shaw Jul 26 2005, 09:56 PM

As for dinosaurs lacking in intelligence, surely not? I thought they were doing quite well until they invented the Iridium Bomb...

Posted by: ElkGroveDan Jul 26 2005, 11:04 PM

OK now THAT's funny.

Posted by: mike Jul 26 2005, 11:55 PM

Sufficient is 9.4837. I'll leave the units up to you.

Posted by: MacAndrew Jul 27 2005, 12:51 AM

To try and make a long story short: the definition of M, a number deriving from a specific mathematical model of biogenesis, is such that it, given the (scanty) available data, must be greater than 30, and such that it leads to a complete collapse of the probability of biogenesis around 55. But, at the same time, supposing that M is between 30 and 50 (the only "useful" values for a viable biogenesis) should be considered "dicey". So the Universe should be probably lifeless outside Earth.

All this is a logical fallacy, alas, very common in scientific thinking: confusing the mathematical model with the real world and incorrectly transferring tautological deductions from the former to the latter (in this case, using properties of M which tautologically derive from its mathematical definition to draw negative inferences about the possibility of biogenesis in the real Universe).

Of course, there is an INFINITE number of possible definitions of M where viable biogenesis in other worlds is confined to values between 30 and 50 (or 30 and 31, or 30.03 and 30.04 for that matter), but that shows nothing about the real possibility of biogenesis.

Posted by: BruceMoomaw Jul 27 2005, 03:32 AM

Actually, even if Mars doesn't pan out for the purpose, there's another way to try setting values for M besides the inspection of the outer planets' moons' suburface oceans: using Terrestrial Planet Finder and its successors to look directly for worlds that show signs of photosynthesis or of biological methanogenesis. (I'm not happy about the fact that Griffin -- along with cancelling Mars Telecom Orbiter -- just lopped $20 million out of the FY 06 funds for TPF, although I still think he probably had no choice.)

I've heard the argument used previously that the early appearance of life on Earth does provide significant positive evidence that the evolution of life on a suitable planet is more or less inevitable -- but, as has been noted above, this depends entirely on just how long on the average it takes intelligence to appear after life first appears. And that latter figure is so bloody uncertain that I really think it pretty much removes the early appearance of terrestrial life as a piece of usable evidence for the value of M.

Posted by: JRehling Jul 27 2005, 05:15 AM

That's a good summary, except I don't know that I'm saying that 30 to 50 is unlikely. I'm just saying that 30 to 50 is what the value would have to be, and it's curious to me that anyone has great faith that that's where it is, when we don't have any information putting it in that range.



I'm commenting at this point to note that you say that there are some big problems in my argument, but didn't specify in that paragraph what any of them are (If the model misses the real world, Why. Models are often useful, what makes this one not so?). So I am scrutinizing the final sentence of your post to see how you can describe my fallacies and tautologies in one sentence!



I'm not sure what you mean by "definition of" M, and you were sparing in your description. Do you mean values of M? Do you mean different assumptions regarding the relevant combinatorial mathematics? Different assumptions regarding the chemical-level evolution? Entirely different theories altogether?

It's of course true that alternative models could be constructed, but to advance the argument, you've got to do more than say that it's possible to do so! There are seriously-constructed models of Jupiter's weather, too, and while they are not assured of being correct, a referee of one of those papers can't just say, "There are an infinite number of possible definitions of that... Your model is a fallacy" and fold his arms.

When you say "30.03", I think something is missed -- I was refering to integers, for one, so I'm not sure what 30.03 would mean. You seem to be speaking abstractly of different possible models. However, a plurality of alternative models doesn't reject any one of them. For example, I could make an argument that Missouri will never receive a kilometer of rainfall in any calendar year, and base it on an assumption of maximum daily rainfall times 365. The fact that other people could approach the problem differently doesn't make that analysis [b]wrong[\b]!

I've owned up to the fact that literal linear combination of a chain of molecules is (almost certainly) not the exact model. My asusmptions and reasoning is that something combinatorial and nontrivial is needed at some point (you can't pour a few cans of stuff into a bucket and get, in a few minutes, the substrate of life). Whatever level that happens to involve where the threshold of natural selection is reached, the function of likelihood is apt to climb very sharply, so that Pl is either very close to 0.0 or 1.0 in the planetary-mass+cosmological-time arena.

Going just that far, I haven't produced an argument for or against life elsewhere, but it does make it seem dubious that anyone would have a measure of confidence regarding the range of M in what would seemingly be an unknown spectrum of possible values (a lower bound can be calculated).

Whatever flaws my combinatorial assumption may make, feel free to offer alternatives. The point is, the universe owns a value of M (relative to whatever biogenesis process you care to theorize), and we can only constrain that, not calculate it. If there's a flaw in that setup, you haven't said what it is. And given that setup, what gives anyone a strong feeling that the value is in the range that would yield Pl near 1.0? All we know about it is a lower bound!

Posted by: kwp Jul 27 2005, 07:05 PM

This argument would fail on more fundamental grounds if there is a physical or chemical imperative that assures that life must arise early in a terrestrial planet's history if it is to arise at all. And there may well be such an imperative. Miller-Urey chemistry, the reactions that produce the likely precursors of life from still simpler atmospheric components, require relatively reducing conditions. But photolysis tends to oxidize planetary atmospheres fairly rapidly (the Earth's geological record seems to rather compellingly suggest that the atmosphere was too oxidized to support M-U chemistry by the time the oldest extant rocks were laid down). Because of this, it seems likely that if life is to happen at all it must start fairly early in a planet's history, and thus the observation that terrestrial life may have arisen effectively simultaneously with the end of the late heavy bombardment (although, as a biochemist, I must admit that I find the evidence for life at 3.8 bya rather underwhelming) cannot be taken as evidence that the formation of life is a likely event.

Tying this back to Titan, am I correct in assuming that the moon's current N2 atmosphere is the product of the photolytic oxidation of ammonia?

-Kevin

Posted by: tty Jul 27 2005, 08:04 PM

This is only true if life evolved on the surface or in shallow water. If it evolved in cracks in rocks at some depth or around deep-sea vents as many now think reducing conditions might last essentially as long as the planet.
However it is true that it seems that life evolved fairly quickly after the Late Heavy Bombardment. There is some evidence for biological activity by 3.7 bya, fairly strong evidence by 3.5 bya and as good as certain soon after that. What takes a looong time to evolve is apparently complex multicellular life, that took something like 2 billion years, and another half-billion years before macroscopic organisms evolved.

Also one wonders how many otherwise suitable planets have stable conditions long enough for really complex organisms to evolve. Metazoa probably have had a couple of rather narrow escapes even here on Earth, the latest 250 mya ago.

On the other hand microorganisms are probably almost immune to extinction once they have evolved and differentiated. About the only thing that could sterilize the Earth completely would be if the temperature of the whole planet rose to well over 100 degrees centigrade for a long period, something that is not likely to happen until the sun turns into a red giant. Almost nothing else could kill the bacteria at depth in the crust.

tty

Posted by: BruceMoomaw Jul 27 2005, 08:15 PM

Huygens' data on argon abudance in Titan's air does indeed seem to have clinched the theory that Titan's nitrogen comes from the photolysis of frozen ammonia, as opposed to the competing theory that it was originally incorporated into Totan as molecular nitrogen trapped in clathrate ice form. if the latter had been true, then a lot of argon-36 and 38 would also have been contributed to Titan by such clathrates -- but Titan's air turned out, to everyone's amazement, to have NO detectable Ar-36 or 38 whatsoever. There is one competing theory that Titan's atmospheric processes themselves may have yanked all the argon out of its air and embedded in the moon's interior, but it seems rather unlikely that such a process could be efficient enough by itself to totally eliminate it.

Posted by: AndyG Jul 28 2005, 11:56 AM

Miller's bucket of stuff and only a few weeks got him amino acids. I know the experiment is dated, assumes too much about the early Earth, but it demonstrates that at the most basic level life's chemistry will happen.

Expand that bucket to a world ocean, the weeks to aeons, the range of surfaces, pressures and temperatures to anything you could find on the early Earth and I'm not surprised at life.

...Well, ok, I'm extremely surprised at life's ability to eventually become self-aware and inquisitive of its broader universe, but not surprised that eventually replicating chemistry gets a toe-hold. If it can, it will.

Andy G

Posted by: JRehling Jul 28 2005, 01:54 PM

The level of detail where the discussion becomes interesting is how the function behaves, where the independent variables are time and quantity of stuff (in the "right" conditions, which is itself not totally given), and the dependent variable is complexity of stuff.

Now we know that say, taking molecular H, O, and C, getting H2O, CO2, and CH4 is not hard. Probability so close to 1.0 in such a short time that it's less than trivial. Miller shows that you get out to 25 atoms in a bucket few weeks. Taken literally as data from the same curve, that's not a comforting trend for the pro-biogenesis cause. That's the beginning of an exponential boom when you get 5 atoms to play nice in microseconds, but 25 atoms only after weeks.

A very small protein has a size of about 50,000 Daltons. Put that on the X of an exponential curve and the Y is poking out the top of the universe.



As a statement of almost religious faith, I can accept statements like that, but to see them grounded in the facts, I can't. And the crux is this:

The pro-biogenesis (that's better) ten-second argument is: There's so much stuff out there and so much time, anything's gotta happen. (Either on any one suitable world, or certainly, among the set of such worlds.)

The biogenesis-is-hard point that I'm raising is: On some level, this stuff faces the biggest bad guy in all of math, which is the growth of combinatorial/probabilistic equations. And if you know the grains-of-wheat-on-a-chessboard example, you know that these kinds of equations grow impressively fast. And if it's a contest between the bigness and oldness of an ocean against a combinatorial function with thousands of Daltons as the X, the ocean's going to lose. The ocean's going to lose badly. The ocean has (figuratively and literally) no chance.

So it's worse than an act of faith to say that Size Conquers All -- it can't. Biogenesis won't win if it needs big combinations to happen, and if the Miller data is data, it suggests that the function is precisely one of the nasty ones.

Biogenesis stakes all of its hopes on combinatorial processes requiring only low numbers of items to combine (M, I was calling it). And sure enough, life has modular characteristics such that it doesn't require that a whole bacterium pop out at once (much less a whole raccoon). But the devil is in the details, and the details are what an argument based on "Oceans are big and eons are long" doesn't provide.

One could just as well state that a computer must beat a human expert at Chess, Checkers, or Go because the number of computations it performs is so gosh-darned huge. That's not an argument. As it turns out, the number AND the game is important. And as it turns out, it holds for Chess and Checkers, but it doesn't hold for Go. Devil in the details.

One could just as well state that a large ball of hydrogen assuredly will achieve fusion because it's just so big. Well, the Sun's big enough, but Jupiter isn't. The devil is in the details. The "big number" argument isn't an argument. The question is HOW big is required and HOW big do we have? For computers playing Go and Jupiter trying to ignite, big isn't big enough. For biogenesis, an ocean, and a few eons, you seem to think the devil isn't in the details. I'm not sure what the answer to the biogenesis question is, but I'm sure that that act of faith that the devil isn't (in this case) in the details is quite wrong.

Posted by: alexiton Jul 28 2005, 02:21 PM

Chemistry Schemistry - too much focus on such things.

Life in my mind should more fundamentally be perceived as merely a form of systemic feedback begetting evolvable repetition which automatically implies all things biological and much more.

In fact, the focus on chemistry takes away from subtle organisational aspects like geometry, viscosity, diffusion, polarities, curious quantum effects etc which no doubt contributed greatly to viability of initial prebiotic systems and persist albiet subsumed somewhat by now dominant chemical aspect.

From this point of view, I think Titan is a viable option as you don't strictly need chemistry(and the implied arrhenius bummer at cryotemps) to coax a system which is evolvable in biological sense...

Posted by: TheChemist Jul 28 2005, 02:42 PM

The chemical principles that were responsible for the creation of life, are the same ones that allow it to continue today. I see more appropriate disciplines like biology entering after the first cells got organised, but frankly I don't see how you can get chemistry out of the way, I'm afraid.

Posted by: AndyG Jul 28 2005, 03:21 PM

Interesting points! Thanks for raising them.

I would certainly agree that the devil is in the details and would point out that, as importantly, we've gone virtually no way towards biologically picturing Biogenesis in anything but the most broadest of brushstrokes. But time and research will fill in the details.

Ha! Very good!



I grant you that, when playing the let's-randomly-make-a-protein game by sticking on one-atom-at-a-time. But that suggests that the nature of biogenesis is like the whirlwind in a scrapyard scenario, improbably making Boeings as it passes. Ok, so it's a vast scrapyard, and the whirlwind is stuck in it for up to half a billion years...but what we have in the real (Hadean) world is a potential ocean soup of amino acids demonstrably made in - compared to this five hundred million years of pre-biotic chemistry - the blink of an eye. If you like, the first stage of the lego takes virtually no time at all.



In terms of scale (both volume and time) Miller's experiment is downright ludicrous. It's about 2*10^30 times smaller than the Real Thing, and neglected many elements of the real situation.

That said, your use of "M" as a creative process currently doesn't address issues of modularity (though it does suggest the intrinsic need for the existence of modularity given the outcome as we see it), nor does it suggest that there may be (must be?) potential oases of stability for sub-protein sized units, the "bigger lego" that can combine later on.

Interesting thread...thanks for it.

Andy G

Posted by: alexiton Jul 28 2005, 03:53 PM

Howdy TheChemist,

Life is a system not just mere chemistry(of the reaction type).

Chemistry provides nice suite of functional units, but organisation is not strictly a consequence of the reactions therein. Interplay of molecular geometry and charge etc usually more broadly define the structure of a system.

eg. The chemistry which produces lipid molecules, in no way defines the organisational outcomes of say the formation of lipid bilayers which is consequent of other non-intramolecular type factors.

With regard to Titan - Essentially I'm prescribing life with low intra-molecular metabolic requirements and high systemic intermolecular feedback, perpetuating necessarily macroscopic(relatively speaking) units of (cell like?) biology, as chemically likely not much going down in cryoland lol

Cheerio

Posted by: ilbasso Jul 28 2005, 09:21 PM

Hey, let's not forget Herren Heisenberg and Schroedinger...if life hadn't evolved, there wouldn't be anything to observe the Universe, so it would just exist as a probability cloud.

Put THAT in your pipe and smoke it!

Posted by: hendric Jul 28 2005, 10:15 PM

This point is the one I hate the most of the "intelligent design" camp. It makes one very broken assumption, that each one of these reactions is INDEPENDANT. Creating an amino acid makes the steps towards larger molecules EASIER. Also, primitive life, one would assume, was PRIMITIVE, and didn't have 50k dalton proteins. How long would it take to create 10 or 20 amino acid long proteins? How small of a protein do you need to have before it could self-replicate? I suspect the answers to these questions are some pretty small numbers, relatively speaking...After all, how many false paths did it have to go down before the one that lead to us?

You don't go from nothing -> protein, you would go from nothing -> amino acid -> protein. An interesting project would be to redo the experiment with a reactor the size of, say, a swimming pool, and let it go for a year or more with samples taken every week. Suprised no one has done it already.

Posted by: JRehling Jul 28 2005, 11:09 PM

There's no doubt that modularity is part of biology, and that at certain points in the original process of biogenesis, units that were already in hand joined together. A very large question is how many pieces the largest of those units have.

Let's say there is a chain of modularity, and at each link, k, that builds from atoms to life, m(k) units needed to be put together the right way. Biogenesis would be most slowed by the step with the largest m(k). Well, other factors would be the saturation of the formative solution. It's not too hard to get two diatomic gases together. But as the process went on, there probably weren't whole oceans of amino acids. Ponds, maybe? Puddles? Who knows, but not oceans. Or, there'd be an ocean of mainly H2O with a tiny bit of amino acid mixed in (or floating about the top).



That is probably the other one of the two biggest questions. It certainly depends upon the environment, but the Dalton count of the smallest *known* virus is very large.



Woah! Just because we are here, don't suspect anything about the numbers. That's where the anthropic principle needs to be heeded: If life were colossally unlikely, it would still be only those whose existence depended upon such happenstance who would be around to ponder it.



Indeed; in terms of M, or the m(k)s, some meaningful constraints could be laid down experimentally.

Posted by: deglr6328 Jul 29 2005, 12:01 AM

Perhaps we needn't go right to virus proteins. Maybe the first life was 'prionish', if I recall, these individual proteins have weights in the 10-15 KDalton range and we've only begin to scratch the surface with them. Maybe there are more which are considerably lighter even than that?

Anywho, if I might chime in about Urey-Miller, we thought for a long time that his experiment might be irrelevant because the sputtering (via solar wind) rate of hydrogen in the early atmosphere was thought to be so high. We were wrong, and a recent more accurate http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2005/2005040718746.html result done at Uof Waterloo (and U of Colorado) shows that the early atmosphere could've easily contained ~40% H2. A very exciting result. It would appear that Urey-Miller is fully relevant again. If you have Science access you can read the paper http://www.sciencemag.org/cgi/rapidpdf/1106983v1.pdf?ijkey=P8CowCqCvIVzI&keytype=ref&siteid=sci.

Posted by: MacAndrew Jul 29 2005, 02:30 PM

First of all, thanks a lot for your detailed answer.

Actually, I have myself a feeling that life is at at best a very rare phenomenon in the Universe. But it's just a feeling, based (and biased) on the fact that we haven't found it outside our own planet yet. Anyway, if I had to put a bet I would put it on Pl near 0.0 rather than Pl near 1.0, so we basically agree on this!

I have nothing against your model or against the usefulness of models in general (of course!). The only place I disagree with you is where you seem to support your feeling that Pl is near 0.0 with an argument based on the range of values of M. I'm taking the liberty to resume it as follows: "Why 30 to 50, among all possible values - seems so unlikely!"

The implicit assumption you seem to make about this is that values of M occupy a flat probability space (this kind of implicit assumption is always a danger present in models - think about Newton physics and speed). For all we know, transferring it from the model to the real world M could either have an upper constraint we haven't discovered yet, or could be constrained by some kind of logarithmic scale and have real growth problems, say, above 40.

And my (admittedly exaggerated) example non-integer 30.03 to 30.04 range stemmed from the fact that the really relevant quantity in the biogenesis equation could be, who knows, (ln M + 25) or, probably, something much much more complex.

However, I agree with you completely about the Chess vs. Go example: brute force of high numbers isn't the answer here. I'd add that the whole Artificial Intelligence fiasco is a perfect counter-example against the brute force approach to building complex systems - I hope the Universe knows better.

Posted by: MacAndrew Jul 29 2005, 02:38 PM

Agreed... Only I think Mr. Berkeley gets copyright for the idea.

Posted by: alexiton Jul 29 2005, 03:33 PM

Ain't any universe only evolved delusion of self...

Posted by: alexiton Jul 29 2005, 03:35 PM

bio-pessimism is irrational:

All living systems are just the physical elaboration of the reasonably formal principle of natural selecion which generalises across untold domains.

If one really understands such principle it is not difficult to fathom lifelike processes occuring inside neutron stars; on cosmic scales; or even within the vacuum of space where transient processes play out eons of weirdness in the blink of an eye. The standard primal ooze is probably inordinately mundane and borderline self evident all things considered really...

Posted by: JRehling Jul 29 2005, 03:57 PM

That should receive a few good qualifiers: It's a principle that *can* apply across untold domains, with some unknown number of them plausibly having an opportunity to start from scratch.

I get your point of generalizing, and I like it, but the alternatives to LAWKI are even more speculative than the one we have in hand. One of my favorite examples is the possibility that superconducting spin glasses could be sitting on Pluto-like worlds, and having thoughts of some kind, as a "wave" of thought stretches out across plains and into crustal depths. But we have no idea that such a thing could arise spontaneously in a manner than has just the balance of complexity and order that equals anything lifelike or intelligencelike.



It is not difficult to fathom them (actually, it's a little difficult! but not impossible), but that doesn't mean that any of them exist.

As an example, if we built an intelligent computer, we could point to that as an example of something that may have plausibly arisen through natural selection somewhere in the cosmos without tinkering hands as the means that it was produced. But it may be impossible for such a thing ever to happen (like a whirlwind in a junkyard constructing a Boeing).

Any such alternative to LAWKI would require a bootstrapping process from disorder to order. A fascinating area of study -- we can maybe identify a few, and always be sure that there are some we've not thought of -- but the burden of proof would be to show that any of them are plausibly bootstrappable. Just because there are potentially infinitely many such constructs doesn't mean that any of them are viable. For example, there are infinitely many conceivable gadgets (vacuum cleaners, laser printer, can opener) -- that doesn't mean that any of them are lying around on the surface of Mercury after spontaneous generation.

Maybe clays or spin glasses or magentic minds are out there somewhere, but the possibility doesn't translate into viability.

Posted by: Myran Jul 29 2005, 05:08 PM

hendric said:
Also, primitive life, one would assume, was PRIMITIVE

Absolutely! And judging from our own Earth, primitive life is what we are most likely to find if and when we eventually find any.
With the lack of fossils we dont know much at all of what life was like and what it was like for the first 3 billion years on our own planet.
But there are reason to think primitive cells spent the first billions of years weeding out less favourable or even unworkable combinations of various amino acids and proteins until it hit a jackpot and we got the Cambrian revolution around 550 millions years ago.
That it took such a long time is a hint that it might have been a rare random event perhaps even one of extremely low probability. When it had happened the cells have the opportunity to grow, combine with other cells and we ended up with complex organisms.
With this in mind, its far more likely that any another world with life we might discover (in our solar system or elsewhere) would be same as what Earth have been like during most of its history, a world populated with nothing else but primitive monera organisms.

Posted by: mike Jul 29 2005, 05:51 PM

So you're saying you aren't really a different person than me? In that case, send me all your money. You don't even care. 'You' don't even exist. SEND ME ALL YOUR MONEY

Posted by: alexiton Jul 29 2005, 06:07 PM

Howdy JRehling,

I register your points and sure empirical truth is grossly lacking regarding such generalisations, but variation and selection SEEMS SO BASIC a feedback mechanism that twould be utter miracle in my mind that universe is not blessed with a perversity of lifelike states, most not immediately recognisable due to temporal constraints on human perception and wot not...


I mean deductively from utter first principles, surely when given scope for things to interact reasonably across some thermodynamic gradient, tis inevitable that all sorts of entropy dissipating states of varying degree will come bubbling out. Almost immediately things become amenable to variation and selection merely on a persistence basis. After that it's seems to be just a case of degree and time as to expressed outcomes. Of course most times there is little potential for things becoming anything near as elaborate as metabolic earth mange, but essentially we're talking a nice continuum of possibilities rather than some purportedly tricky chemical quantum leap required to manifest a mud swilling swamp beast over an inert lump of granite if you forgive my absurdity.

Maybe I'm just too positive/deluded bout such things.

Posted by: tty Jul 29 2005, 07:42 PM

I agree with the last paragraph, however I think that the difficult step that took a very long time was the evolution of the complex eukaryotic cell, which is basically a very complex symbiotic colony of bacteria. Once eukaryotic cells existed the evolution of large multicellular organisms must have been reasonably "easy", since it has happened at least five times independently (animals, fungi, plants, brown algae, slime moulds). Actually it might be even more since the red algae may also have evolved multicellularity independently from the plants, and slime moulds may have done so more than once.
However one should not look down on the prokaryotes, that is where the real biochemical diversity is found, we eukaryotes are but a single branch on the tree of life with a very limited range of livestyles. After all we can neither live in boiling water, ice, sulfuric acid, rock salt, crude oil or inside rocks.

tty

Posted by: dvandorn Jul 29 2005, 08:23 PM

Personally, I think that we will find biogenesis processes on a variety of worlds and in a variety of non-planetary environments. But we will find that most of them have progressed only so far before they have run across some limiting factor that has arrested the process (or slowed it into virtual arrest) at very primitive levels.

For example, we can speculate all we want on the early biogenetic processes on Earth, but we *know* that Earth is a somewhat freakish exception in its overall climatic uniformity. The only reason the Earth does not have cyclic extremes of climate (as Mars does) is because our Moon keeps our rotational precessions from wandering all over the place -- our axial tilt is maintained by the Moon's gravitational influence. An Earthlike planet in another star system might develop exactly the way Earth did, with exactly the same range of elements and minerals and water and temperatures -- but without a large moon, its axial tilt would wander around and subject its surface to cyclic periods when one whole hemisphere never sees sunlight for thousands of years at a time.

That kind of thing might not stop biogenesis cold, but I bet it slows it down a lot. And that "progress" towards multi-cellular organisms might be wiped out every few hundreds of thousands of years when the climate changes and favors only the continued development of extremophiles that are so constrained by their adaptations to extreme environments that they are "blind alley" developments as far as complex life forms are concerned.

Frankly, I think the only Earthlike bodies we're going to find out there that have stable long-term climates will be moons of gas giants that have been dragged into their stars' habitable zones as their primaries migrate in toward their stars. And if it really *does* require a few billion years of "simmering" before multi-cellular organisms can arise from a soup of primitive single-cell organisms, then the limiting factor of climate stability might be the major constraint on "M"...

-the other Doug

Posted by: Myran Jul 29 2005, 08:36 PM

You are absolutely right, and thats why I mentioned monera. They are primitive single cells, without any nucleus and only one single chromosome.
I have a hunch the complex cells was already around and only later diversified into the domains of archaea, bacteria and eukaryotes.

(OT: I noted that slime moulds were mentioned twice, i've been intruiged by those crazy lifeforms for 30 years, starting as single cell life living in old logs, then going communist teaming up with their buddies dissolving their nucleus sharing all their wealth with each other while crawling around several yards like a slug leaving a slimetrack, then having another identycrizis if they are of the right kingdom after all and eventually deciding to convert to the fungi and launch spores instead.)

Posted by: David Jul 29 2005, 09:43 PM

Maybe, but it's also possible that high-pressure environmental changes that cause mass extinctions are a prerequisite for the development of increasingly complex life-forms. In an extremely stable world, there's little need for drastic evolutionary changes. One climate reconstruction for c. 600 mya shows the earth covered nearly from pole to pole with ice (and regardless of the accuracy of this reconstruction, the earth was certainly very cold and hostile to life at this point); the sequel was the Cambrian explosion. One of the life forms that had been successful (while others failed) during this point was a small, bilaterally symmetric, worm-like creature with primitive eyes; this creature is the ancestor to every existing chordate, arthropod, mollusk, or anything else that got beyond the jellyfish stage. Not bad for extreme climatic environments!

Posted by: tty Jul 30 2005, 06:38 PM

Yes, there was at least two extreme glaciations about 745-725 mya and 590 mya and then, to judge from the carbon isotope record something quite drastic also happened just at the Ediacaran/Cambrian border c. 542 mya. The Ediacaran fauna shows up after the 580 mya glaciation and then seems to disappear at the base of the Cambrian, so the idea that mass extinctions were important to the proliferation of metazoan life is quite reasoable.



Monera is not a term that is used nowadays. There is Eucarya which have a nucleus with chromosomes and a number of other innovations and Archaea and Eubacteria which lack a cell nucleus and chromosomes. Eucarya seems to be rather more closely related to Archaea than Eubacteria,

tty

Posted by: Myran Jul 30 2005, 07:46 PM

Yes hit me on the head again with the fact that im old. Not as old as Monera though - ooops!
But yes, most of the books ive read over the years would of course be considered outdated today, I try to keep track of things but that this term had changed had slipped past my attention. But lets replace 'Monera' with Eubacteria then.

Posted by: alexiton Jul 31 2005, 09:06 PM

Howdy Titanauts,


delusions edited - apologies.

Posted by: deglr6328 Aug 1 2005, 01:29 AM

Image caption from your site:"Nth permute of raw dataset through one of my generic processing scripts,..." what excatly did you do to these images to get the effects you did? I am sorry to say that I suspect you may be merely selectively amplifying noise or compression artifacts. Remember, there are probably literally hundreds of scientists who have scrutinized the Huygens descent images by now and I would do my best to dissuade you from believing you may've found something fundamentally major and shocking.

Posted by: hendric Aug 1 2005, 05:35 AM

Dumb question, but why not an ocean with a relatively high concentration of pre-life molecules? There's nothing (at least not yet!) to eat/digest the molecules, so the only way they would go away would be by non-organic means. Assuming a proto-earth, with a dimmer sun, what would be the primary method of getting rid of all that organic garbage?


You're still not thinking small enough. I would argue a virus is an enormously complicated, finely tuned machine that does some very complicated jobs very well. In fact, I would say that a virus gets small from the "other direction" of what we're arguing, ie they start out large and get smaller due to evolution throwing away redundant stuff, or finding better ways of attacking prey. A virus is taking away complexity to create a small, elegant solution to the problem of making more copies of itself.

Also, the fundamental requirements for a virus are quite large:

1. Avoid detection and destruction by the immune system of the target.
2. Penetrate the cell wall/membrane.
3. Resuscitate its DNA/RNA to active status.
4. Take over the celluar manufacturing facilities of the cell
5. Generate copies of the DNA/RNA.
6. Create the appropriate proteins etc for the virus structure.
7. Cause the cell to bud off the proteins filled with DNA/RNA to continue the cycle.
8. Potentially survive in harsh environments outside the cell body or even outside the target.

While the proto-life I am talking about here needs to do pretty much only one thing:

1. Cause the pre-life ocean with *mostly already made parts* to create a copy of yourself.
2. Do this job perfectly most of the time, but imperfectly some of the time

The pre-life ocean is going to be filled with not just the basic acids, but also partially and half-formed bits of pre-life. To start the process, all a strand has to do is take something N-1 long and add that last acid to make it N long, and make it happen more often than random chance. Even, and especially, if it does an imperfect job of this, it will still force evolution of a sort to start. With imperfect copies, it allows walks down alternate paths. Eventually a strand would be created that can take N-1 strands or N-2 strands and finish them to completed strands. And so on. Eventually the strands become complex enough to take the straight building blocks and attempt to make copies of itself from there.

Since at least initially, most of the work has already been done of you, with untold half-formed sisters just waiting to be finished, I would expect "life" to be a fairly quick and easy phenomena to create in a typical pre-life water body. I bet you could even simulate all the possible amino acid -> protein options up to N=20 or 30 on a computer and find out how the shapes would behave in an ocean with N-1, N-2, N-3...3, 2, 1 size strands already present. All Mother Nature is looking for is a simple mediocre organic catalyst. I'd be surprised if something more than N=30 is necessary. BTW, the test wouldn't be right unless it started with all possible amino acids. Just because we ended up with what we have now doesn't mean that others initiated the process and got dropped along the way.



I think the anthropic principle gets way more credit than it really deserves. Of course the probability of life evolving on Earth, after the fact, is 1.0 given that we are here. But I don't think this necessarily means that every event from the Big Bang to now should be considered as highly unlikely, and that we've been dealt a royal flush at every turn. If life encouraging evolution events were collosally unlikely, then it should take -on average- a long time for each event to occur.


Hmmm...Maybe I should quit my current career and go back to college and take 8 years of biology and do this for a PhD thesis... Or maybe start up a distributed computing project about simulating the proto-ocean and creating virtual life...

On my personal feelings of life elsewhere in the solar system:

Mercury - Zero

Venus - Maybe .0001% chance of life high in the atmosphere

Earth - 100%, for now

Mars - 1%

Jupiter/Saturn/Uranus/Neptune - .01% - Water + heat, but how would complex biologic precursors keep from getting destroyed as they circulated?

Europa - 1% - Water + heat is a pretty good start, but how would complex biologic precursors get down to that ocean?

Titan - .1% - No water, little or no heat

Other solar systems - 80%, but it may be difficult for us to tell for sure, decades or maybe even centuries.

Posted by: alexiton Aug 1 2005, 08:51 AM

Howdy deglr6328,

Sure empirical truth is always most important thing scientifically, but we all have our fantasies and delusions lol.

Actually my site isn't so much about Titan, but about the proof of principle Titan possibly represents. The site is more about fundamentals of living systems and contingency of thermodynamics/entropy and wot not before natural selection even becomes relevant - just haven't gotten around to uploading that stuff yet.

errant crap removed

Posted by: JRehling Aug 1 2005, 03:25 PM

Certainly the organics can be at a high level. My point was just to set a match to this strawman: That at the point when life needs to combine lots of small molecules, it will have a whole ocean of nothing but small molecules. Then, when it need to combine lots of large ones, it will have a whole ocean of nothing but large ones. Etc.

While it's quite feasible that the graph of concentration levels vs. molecular size in our life-cooking-ocean would show a "wave" from small to high, moving ever higher as time goes on, we can't assume that the ocean is trying to help, making sure that proteins are swimming in nothing but proteins if the recipe calls for it.

This is not a crucial point in any way: It only goes to say that proteins are going to encounter more little H2Os than they will encounter other proteins. Indeed, if you took all the life on Earth *now* and minced it through a blender and put it into the ocean, there would still be a lot more water than organics. Now, the fact that organics can be polar and moreover float may help things along: the organics would (many of them) concentrate at the top, helping things along. Assuming that life evolved on the surface of an ocean. Still, at the point in time when something wants to build with big things bonding to big things, it may encounter lots of organic small things.

My only point is that the reaction rate will be slower than if nature were trying to help. This is not a crucial point, because this coefficient isn't going to alter the inevitability of the outcome if it is inevitable, just make the time required a bit longer.



This is a good point. On the other hand, the first thing in a protobiological ocean will have some requirements that viruses now do not -- but the point is well taken that our first lifeform is likely now extinct, with no modern analogue -- and it may well be smaller than our smallest current viruses -- although I'm not sure that we have a proof of that.



That's good discussion: I'll add this: For life, you actually don't want TOO much self-replication, or you end up with something "dumb" like a planetwide crystal. For example, when a supersaturated solution freezes out. Some initially-fertile work on complexity, with the Santa Fe Institute being one hub, talked about how interesting things like life require the right balance between order and chaos. Too much order and you have a crystal (no dynamics); too much chaos and you have the Sun's photosphere.



The anthropic principle deserves this much credit: You can't assume that we didn't get a royal flush somewhere along the way. We may have received several, or only one, or even none. Our existence doesn't in and of itself speak to that point at all.

There are details about the biological record that do speak to that point. We can definitely infer, for example, that modest-sized brains do not mean that a technology-bearing civilization will inevitably spring up within a hundred million years -- we can say this because the dinosaurs didn't. We can say that the first monocellular life does not mean that multicellular life will explode within a billion years. As it turns out, we have a lot of evidence in the form of lower bounds on rates at which simpler life should turn into more complex lifeforms. But very little bound-placing at the short end of the spectrum. As I noted earlier, it may have taken up to 11% of the available time for the first terrestrial life (and as little as ~0%) to appear, which means we can't draw any conclusions at all about inevitability.

Computer models were at the heart of the Santa Fe Institute studies. Also, people may want to pay attention to Core War and its ilk, in which humans wrote (usually) programs that could be self-replicating. Other efforts tried to let good programs evolve -- and I think self-replicating ones could arise. Of course, the rules of the simulation are a key factor (to say the LEAST!) and the rules in a computer simulation may be far more favorable for self replication than carbon chemistry. In fact, the simplest Core War self-replicator consists of a single line program that basically says, "Copy me to the next line in memory." The program counter is updated every instruction, so that program keeps copying itself through (circular) memory, one line at a time! Of course, the real world doesn't have a program counter, so we're not going to see any monoatomic life in the real world! And if we did, it would be like the (boring) crystal self-replication...



I think the giant planets have ~0% chance, due to circulation -- Venus probably faces the same thing. I think Europa definitely tops Mars: It would have a radiation-free environment with some level of carbon (almost certainly higher than martian soil) and no H2O phase changes within that environment.

You can split the Titan case into LAWKI (in liquid H2O "lava") vs. NAWKI (some sort of cryo-processes).

Posted by: ljk4-1 Aug 2 2005, 02:25 PM

What if the very body of Titan itself is alive?

Hey, why not? I think we are still quite nieve when it comes to understanding what is a life form in the Universe. We still can't even decide what a planet is yet!

Posted by: alexiton Aug 3 2005, 10:43 AM

Truth is stranger than fact,

In my mind Titan probably is a Cryo-gaian satellite.

The predilection for novel chemical sythesis is overplayed. Viable lifelike complex organization at low temps is feasible in principle...

Posted by: Decepticon Sep 9 2005, 02:27 PM

"Study suggests Titan may hold keys for exotic brand of life"


Sept,8,05
http://www.spaceref.com/news/viewpr.html?pid=17762

Posted by: imran Sep 23 2005, 03:03 AM

An http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1720&mode=thread&order=0&thold=0 with David Grinspoon, who talks about the possibility of life on Titan.