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Colin Robinson
2015-Jun-04, 11:37 PM
Diatoms are a class of microscopic organisms, abundant in Earth's oceans. Many have geometrical shapes, comparable to crystals. Their bodies contain silicon dioxide, also found in rocks and sand.

What if Titan has exotic organisms comparable to diatoms — crystal-like in shape, and their bodies contain not only slushy organic compounds, but also substances found in Titan's rocks and sand, for instance water ice?

How easy or difficult would it be for us to distinguish such a class of biota from an exotic mineral, an "icy precipitate" ?

Fiery Phoenix
2015-Jun-06, 07:31 PM
It's an interesting idea, but I don't believe we're capable of detecting such life without sending robotics to investigate. At least not with the current technology. So the safer bet is to write them off as minerals.

Colin Robinson
2015-Jun-06, 10:17 PM
It's an interesting idea, but I don't believe we're capable of detecting such life without sending robotics to investigate. At least not with the current technology. So the safer bet is to write them off as minerals.

Agree with your first two sentences. There are a lot of reasons to send further robotic probes to Titan. In an environment where carbon compounds are abundant, with liquid solvents and sources of chemical energy, why should we write things off as minerals before taking a close look at their structure and composition?

Fiery Phoenix
2015-Jun-07, 05:16 AM
Agree with your first two sentences. There are a lot of reasons to send further robotic probes to Titan. In an environment where carbon compounds are abundant, with liquid solvents and sources of chemical energy, why should we write things off as minerals before taking a close look at their structure and composition?
I guess what I was trying to say is there is a tendency for us to approach things with extreme circumspection when it comes to detecting extraterrestrial life; the default supposition for potential discoveries is never 'life'. In this case, because we lack the means of investigating the structure and composition closely without the aid of probes, we are limited to our usual assumptions, which rarely definitively translate to life.

Colin Robinson
2015-Jun-07, 06:25 AM
I guess what I was trying to say is there is a tendency for us to approach things with extreme circumspection when it comes to detecting extraterrestrial life; the default supposition for potential discoveries is never 'life'.

Would you like to say more about what you mean by "the default supposition", in this context?


In this case, because we lack the means of investigating the structure and composition closely without the aid of probes, we are limited to our usual assumptions, which rarely definitively translate to life.

But we (if "we" means "we humans") don't lack the means to send more probes. The Cassini-Huygens mission has shown that we can reach Titan with a robot probe and land on it. It's a question of will. Do we want to know how carbonaceous substances behave on Titan? Are we prepared to make the effort to find out?

Fiery Phoenix
2015-Jun-07, 06:40 AM
Would you like to say more about what you mean by "the default supposition", in this context?
I just meant we never seem to be quick in saying we've discovered life. We always prioritize other possibilities before claiming a potential discovery may signify alien life. Not that this is a bad thing. As Carl Sagan once put it, extraordinary claims require extraordinary evidence.


But we (if "we" means "we humans") don't lack the means to send more probes. The Cassini-Huygens mission has shown that we can reach Titan with a robot probe and land on it. It's a question of will. Do we want to know how carbonaceous substances behave on Titan? Are we prepared to make the effort to find out?
Correct, that's what I meant. We don't lack the means to send probes, but we do lack the means to detect such life without sending probes. I'm also sure the will is there. It's probably more of a question of investment.

Colin Robinson
2015-Jun-07, 09:04 AM
I just meant we never seem to be quick in saying we've discovered life. We always prioritize other possibilities before claiming a potential discovery may signify alien life. Not that this is a bad thing. As Carl Sagan once put it, extraordinary claims require extraordinary evidence.

I'm not sure which would be more extraordinary Titan with exotic life, or Titan with an active system of organic compounds reacting with each other but no life? Either way, it's a far-from-ordinary place...

publiusr
2015-Jun-07, 06:50 PM
Life existing rather like frost--cold, slowly growing. Then too--I thought winds in the ice giants would be slow, so...

Colin Robinson
2015-Jun-08, 02:23 AM
Life existing rather like frost--cold, slowly growing. Then too--I thought winds in the ice giants would be slow, so...

I think you're likely to be right about life on Titan growing slowly. One reason is that the density of chemical energy in the atmosphere is less that on Earth. Chris McKay did the sums, and found that the energy density is equal to what is used by some life-forms here on Earth, such as bacteria/archaea. So something like a layer of single-celled organisms would more likely than something like a sunflower.

Paul Wally
2015-Jun-08, 05:42 PM
Agree with your first two sentences. There are a lot of reasons to send further robotic probes to Titan. In an environment where carbon compounds are abundant, with liquid solvents and sources of chemical energy, why should we write things off as minerals before taking a close look at their structure and composition?

I think what distinguishes life is function rather than structure and composition. For example metabolism, reproduction, evolution are all functional aspects. So it's more a question of "does it behave like life" rather than "does it look like life".

Colin Robinson
2015-Jun-08, 09:48 PM
I think what distinguishes life is function rather than structure and composition. For example metabolism, reproduction, evolution are all functional aspects. So it's more a question of "does it behave like life" rather than "does it look like life".

In principle I agree. But would it be possible to study functions (such as evolution) without looking closely at structures and compositions? If I remember correctly, Darwin's thesis about evolution in finches was based on comparative study of the structures of beaks of different species.

Selfsim
2015-Jun-08, 11:26 PM
The hypothesis of: "exo-life may exist on Titan" is a valid hypothesis only because:

i) the scientitifc process is able to produce test results leading to confidence levels commensurate for determining Earth-life when it is present in a test sample and;
ii) the scientific process is able to produce empirically supportable definitional boundaries for distinguishing between 'Earth-life' and other not-life classes, in Earth sourced test samples only.

There are no tests meeting either of these same general criteria, for diagnosing so-called 'exotic' life, (life as we don't know it).

Therefore the pursuit is not scientifically justifiable.

A false negative result produced on imagined 'exotic Titan lifeforms' is therefore nothing more than a test performed on purely imaginary thoughts and could easily be performed during a dream at night in bed say, (or something similar). That is, where the outcome is just as scientifically meaningless, as the original question was.

Paul Wally
2015-Jun-09, 01:13 PM
In principle I agree. But would it be possible to study functions (such as evolution) without looking closely at structures and compositions? If I remember correctly, Darwin's thesis about evolution in finches was based on comparative study of the structures of beaks of different species.

Of course we have to look at structures, but I'm saying when it comes to distinguishing life from non-life how would we do it by looking at structure. The Mars meteorite is a good example where we get complex structural formations but we can't tell whether it's biological or just due to some
kind of crystallization process.

If we take your example of "bodies containing slushy organic compounds" will we be able to tell whether it is life or not?
I'd say we can't rule out some geological explanation (similar to the explanation for Martian blueberries). But suppose
we send a microscope connected to a video camera and we observe that these bodies replicate themselves like bacteria then that
would be a different matter.

Paul Wally
2015-Jun-09, 01:29 PM
There are no tests meeting either of these same general criteria, for diagnosing so-called 'exotic' life, (life as we don't know it).


I don't think it is so difficult to test for life. Let's take Colin's slushy blobs. If we observed something like that replicating itself, then what would you say about that? Is it life? Could it be life?

Selfsim
2015-Jun-09, 10:46 PM
I don't think it is so difficult to test for life. Let's take Colin's slushy blobs. If we observed something like that replicating itself, then what would you say about that? Is it life? Could it be life?What are your reasons for assuming that metabolism, reproduction and evolution 'functions' could possibly be present in an environment too cold to permit ionic interactions amongst the only molecules known to be at the basis of such functions?

Your starting premise has no empirical or theoretical basis of support. It is an irrational premise.

Colin Robinson
2015-Jun-10, 01:55 AM
What are your reasons for assuming that metabolism, reproduction and evolution 'functions' could possibly be present in an environment too cold to permit ionic interactions amongst the only molecules known to be at the basis of such functions?

Your starting premise has no empirical or theoretical basis of support. It is an irrational premise.

To suggest that growing, reproducing, evolving systems might be based on different chemistries is a conjecture. It is not a matter of "assuming" (in the everyday sense), or putting forward an "irrational premise".

You seem that think that we shouldn't consider such things unless and until we find them. My concern is that we're less likely to find them, even if they are out there, if we haven't first considered what they might be like.

Selfsim
2015-Jun-10, 04:29 AM
To suggest that growing, reproducing, evolving systems might be based on different chemistries is a conjecture. It is not a matter of "assuming" (in the everyday sense), or putting forward an "irrational premise"

You seem that think that we shouldn't consider such things unless and until we find them. What are your reasons for suggesting that such things exist 'out there' even though the environment, (in this case: Titan's surface liquids), is measured as being too cold to permit the fundamental ionic interactions necessary for metabolism, reproduction and evolution, amongst the only molecules known to cause such functions?
My concern is that we're less likely to find them, even if they are out there, if we haven't first considered what they might be like.And how are the chances improved if they are not 'out there'?
It would seem that dreaming them up in advance, is of no significance, if they don't exist there in the first place. (As the evidence in hand implies .. ie: the low temperature environment)?

Colin Robinson
2015-Jun-10, 01:46 PM
What are your reasons for suggesting that such things exist 'out there' even though the environment, (in this case: Titan's surface liquids), is measured as being too cold to permit the fundamental ionic interactions necessary for metabolism, reproduction and evolution, amongst the only molecules known to cause such functions?

I claim no personal credit for the suggestion that life on Titan is a possibility to be taken seriously.

NASA's Astrobiology Roadmap (2008) says: "The existence of lakes of liquid hydrocarbons on Titan opens up the possibility for solvents and energy sources that are alternatives to those in our biosphere and that might support novel life forms altogether different from those on Earth."

There is quite a lot of scientific literature behind this, and it is based both on theoretical considerations, and also on what empirical research has shown about behaviour of various substances in various conditions.

I'll mention a couple of fragments in the big picture...

* information theory showed years ago that replication of a system is NOT dependent on a specific composition. Self-replicating computer programs can be written and have been written, the programs are NOT made of proteins, lipids and nucleic acids, nor are the computers on which the programs are run. So it's not quite right to speak of a particular set of molecules "cause" functions such as reproduction. The verb "underlie" is more appropriate.

* a study completed this year looked at whether any of the organic compounds which known to exist on Titan could form membranes comparable in terms of a stability and flexibility to membranes formed out of lipids on Earth. They found that, yes, the compound acrylonitrile could form such membranes in Titan conditions. This study is the topic of another recent thread in this forum.


And how are the chances improved if they are not 'out there'?

If there is no life out there on Titan, then we won't find it. Even if we send a robot probe equipped with microscopes, cameras, and mass spectrometers. In that case, we will still find out stuff about how complex organic molecules interact with solvents and energy sources in a planet-sized natural laboratory...

Paul Wally
2015-Jun-10, 05:54 PM
What are your reasons for assuming that metabolism, reproduction and evolution 'functions' could possibly be present in an environment too cold to permit ionic interactions amongst the only molecules known to be at the basis of such functions?

Your starting premise has no empirical or theoretical basis of support. It is an irrational premise.

Just because life is known to have a certain chemistry does not imply that it cannot have a different chemistry.

agingjb
2015-Jun-11, 01:51 AM
Surely the Titan surface doesn't need the hypothesis of life to justify studies of such an interesting environment.

Colin Robinson
2015-Jun-11, 03:23 AM
Surely the Titan surface doesn't need the hypothesis of life to justify studies of such an interesting environment.

Study of Titan isn't only about life. Nor is study of life in the cosmos only about Titan.

But studying Titan without addressing the question of life there, would be like a prospector overlooking what might (or might not) be gold because he originally planned to look for silver...

Selfsim
2015-Jun-11, 04:19 AM
... NASA's Astrobiology Roadmap (2008) says: "The existence of lakes of liquid hydrocarbons on Titan opens up the possibility for solvents and energy sources that are alternatives to those in our biosphere and that might support novel life forms altogether different from those on Earth."'Alternative solvents and energy sources' are also ubiquitously dispersed across non-living organic chemistry processes. The way NASA disinguishes between the non-living and living organic chemistries includes the various established tests for life functions. The presence of alternative solvent and energy sources elsewhere (eg: Titan's lakes) therefore (for the same reason) doesn't necessarily imply the presence of what we diagnose as 'life' there. It also doesn't imply any changes in any already believed 'possibilities about testable life being there (again, for the same reason). Further, the so-called 'exotic, hypothetical 'life' belief can either be held, or not held .. depending on what one chooses to believe (or not believe), regardless of any physical discoveries made about Titan's lakes.

I therefore question the logic underpinning, and any tangible value contributed by, the above NASA Astrobiology Roadmap statement. My view is that it is a very low-value, even detrimental statement as far as real science is concerned.


There is quite a lot of scientific literature behind this, and it is based both on theoretical considerations, and also on what empirical research has shown about behaviour of various substances in various conditions.

I'll mention a couple of fragments in the big picture...

* information theory showed years ago that replication of a system is NOT dependent on a specific composition. Self-replicating computer programs can be written and have been written, the programs are NOT made of proteins, lipids and nucleic acids, nor are the computers on which the programs are run. So it's not quite right to speak of a particular set of molecules "cause" functions such as reproduction. The verb "underlie" is more appropriate.A noteworthy point here is that (from the Benner study (http://phys.org/news/2015-05-ether-compounds-dna-oily-worlds.html)):
... any genetic biopolymer able to support Darwinian evolution operating in water must have an ever-repeating backbone charge," explained Benner. "The repeating charges so dominate the physical behavior of the genetic molecule that any changes in the nucleobases that influence genetic information have essentially no significant impact on the molecule's overall physical properties."Taken as a statement of fact (ie: not hypothetical speculation), this implies that in order to qualify as (biological) 'life', the same basic molecular chemistry, (electrostatic attraction, repulsion, solubility, ionic interaction, etc), is a necessary requirement.
Non biological, computer-based, (eg: self-replicating Cellular Automata (CA) etc), also have very specific, pre-programmed sets of functional capabilities. Biology stands as the model basis for defining most CA capability sets.

Information Theory was derived as a general way of making sense of everyday observable behaviours. Empirical observation is the primary basis of the theory. The information itself, is generally taken as being phenomenological in nature. (Physics, for example, explicity defines it that way). The specific repeating patterns of charge in self replicating molecule are taken as 'information', (in Information Theory). The pre-programmed sets of functional capabilities in Self-Replicating Systems (SRS .. like CA), are also taken as information, (in Information Theory).


* a study completed this year looked at whether any of the organic compounds which known to exist on Titan could form membranes comparable in terms of a stability and flexibility to membranes formed out of lipids on Earth. They found that, yes, the compound acrylonitrile could form such membranes in Titan conditions. This study is the topic of another recent thread in this forum.Yes .. it was a very good detailed analysis with interesting outcomes.
Membranes are functionally very distant from a functioning living cell, (as I'm sure most are aware).


If there is no life out there on Titan, then we won't find it. Even if we send a robot probe equipped with microscopes, cameras, and mass spectrometers. In that case, we will still find out stuff about how complex organic molecules interact with solvents and energy sources in a planet-sized natural laboratory...Sure .. almost goes without saying, no?

Selfsim
2015-Jun-11, 05:12 AM
Just because life is known to have a certain chemistry does not imply that it cannot have a different chemistry.If the specificity of the organic chemical makeup and associated processes peculiar to life at the molecular level and upwards, was not as heavily evidenced as it is here on Earth, I might concur.
Unfortunately, the weight of this evidence is abundant, so I cannot concur.

Note that I do not use this as the basis for eliminating different chemistries .. but it is one of my reasons for not concurring with such a generalised statement.

Selfsim
2015-Jun-11, 05:16 AM
Surely the Titan surface doesn't need the hypothesis of life to justify studies of such an interesting environment.So, why not take that to the next level?:

"Surely the surface of any exo-planet doesn't need the hypothesis of life to justify studies of such an interesting environment?"

Very cool ... :)

Cheers

agingjb
2015-Jun-11, 05:38 AM
Titan is special enough to justify its exploration before any other body in the outer solar system - nothing to do with life. I would have given it precedence over Europa.

Paul Wally
2015-Jun-11, 10:12 AM
If the specificity of the organic chemical makeup and associated processes peculiar to life at the molecular level and upwards, was not as heavily evidenced as it is here on Earth, I might concur.

That's what evolution does. After billions of years of evolution things are going to look specific. It's got nothing to do with 'Earth'.


Note that I do not use this as the basis for eliminating different chemistries ..

Good

Selfsim
2015-Jun-11, 10:35 AM
That's what evolution does. After billions of years of evolution things are going to look specific. It's got nothing to do with 'Earth'. What is your basis for eliminating anything to do with Earth from Evolution?

Colin Robinson
2015-Jun-11, 01:54 PM
'Alternative solvents and energy sources' are also ubiquitously dispersed across non-living organic chemistry processes. The way NASA disinguishes between the non-living and living organic chemistries includes the various established tests for life functions. The presence of alternative solvent and energy sources elsewhere (eg: Titan's lakes) therefore (for the same reason) doesn't necessarily imply the presence of what we diagnose as 'life' there.

The NASA Astrobiology Roadmap doesn't say that the solvents and energy sources on Titan "necessarily imply" life there. The words "necessarily imply" are your words, not the Roadmap's. The words used in the Roadmap are "possibility" and the verb "might". The Roadmap is talking about areas for further research.


A noteworthy point here is that (from the Benner study (http://phys.org/news/2015-05-ether-compounds-dna-oily-worlds.html)

Is Benner's statement that "... any genetic biopolymer able to support Darwinian evolution operating in water must have an ever-repeating backbone charge" the same as saying that any genetic biopolymer able to support Darwinian evolution must operate in water? Or is there a subtle difference?


Yes .. it was a very good detailed analysis with interesting outcomes.

I agree. The thing is, this analysis of possible compositions of cell membranes on Titan was carried out because the researchers, like the authors of the NASA Roadmap, thought that prospect of life on Titan is an appropriate topic for detailed study.

It's not likely that anyone any time soon will carry out an equally detailed study of what substances cell walls might be made of on the surface of Mercury. The difference is that Titan is seen as a plausible habitat for exotic life, while Mercury is not.


Sure .. almost goes without saying, no?

In other words, you raised a question with an answer so obvious that I probably shouldn't have bothered!

Paul Wally
2015-Jun-11, 04:26 PM
What is your basis for eliminating anything to do with Earth from Evolution?

Ok let's analyse:

If the specificity of the organic chemical makeup and associated processes peculiar to life at the molecular level and upwards, was not as heavily evidenced as it is here on Earth, I might concur.

Specificity of chemical makeup etc would occur on any planet where evolution has been running for a long time. Specificity is a consequence of evolution, wherever it may occur. So your point that it is "heavily evidenced' on Earth is completely irrelevant. Each planet where evolution occurs will have its own very specific adaptations peculiar to the environment of that particular planet.

Selfsim
2015-Jun-11, 11:27 PM
Is Benner's statement that "... any genetic biopolymer able to support Darwinian evolution operating in water must have an ever-repeating backbone charge" the same as saying that any genetic biopolymer able to support Darwinian evolution must operate in water? Or is there a subtle difference?Dissolution is not limited to just having water available as a solvent. The overall outcome of the process is determined by the thermodynamic energies involved. The dissolution of polymers is dependent on the compatibility of solute and solvent bonds. Evolvability relies on a prevalence of dissolution.

It's not likely that anyone any time soon will carry out an equally detailed study of what substances cell walls might be made of on the surface of Mercury. The difference is that Titan is seen as a plausible habitat for exotic life, while Mercury is not.Does that statement take into consideration the surrounds of the frozen polar regions?
Even so, pondering 'possible' Mercury resident lifeforms won't alter their existence (or not) on Mercury.

In other words, you raised a question with an answer so obvious that I probably shouldn't have bothered!No.
There is no improvement in 'the chances of finding 'life' by pondering non-evidenced hypothetical 'exotic lifeforms', if 'life' is not already present on Titan. The collateral benefit of "finding out stuff about how complex organic molecules interact with solvents and energy sources in a planet-sized natural laboratory" can be achieved independently from chasing imaginary hypothetical lifeforms.

Colin Robinson
2015-Jun-12, 01:05 AM
Dissolution is not limited to just having water available as a solvent. The overall outcome of the process is determined by the thermodynamic energies involved. The dissolution of polymers is dependent on the compatibility of solute and solvent bonds. Evolvability relies on a prevalence of dissolution.
Does that statement take into consideration the surrounds of the frozen polar regions?

Interesting question. Do you think we should start a new thread about Mercury's polar regions?


There is no improvement in 'the chances of finding 'life' by pondering non-evidenced hypothetical 'exotic lifeforms', if 'life' is not already present on Titan.

Of course. That does not contradict my point — if life is already present on Titan, our chances of finding it may be improved by informed conjectures about its possible character.

Selfsim
2015-Jun-12, 05:19 AM
Specificity of chemical makeup etc would occur on any planet where evolution has been running for a long time.
Specificity is a consequence of evolution, wherever it may occur. So your point that it is "heavily evidenced' on Earth is completely irrelevant. Each planet where evolution occurs will have its own very specific adaptations peculiar to the environment of that particular planet. Evolution is not the only explanation for organic chemical specificity over time.

Such specificivity can also occur in non-living organics in environments which can render them incapable of, or inhibit, their Evolution towards the functions of 'life'.

Earth's case history (and the evidence produced) cannot be completely discarded.

Fiery Phoenix
2015-Jun-12, 05:20 AM
Titan is special enough to justify its exploration before any other body in the outer solar system - nothing to do with life. I would have given it precedence over Europa.
Agreed. As far as I'm concerned, Titan is the most interesting body in the solar system. Nothing comes close (though Europa is not too far off).

Selfsim
2015-Jun-12, 05:26 AM
Interesting question. Do you think we should start a new thread about Mercury's polar regions?If you're asking for my opinion then, it is: "No .. not really".


Of course. That does not contradict my point if life is already present on Titan, our chances of finding it may be improved by informed conjectures about its possible character.It will also be more improved by the fortuituous selection of say, a risk-free physical landing site, or the selection of a parachute able to decelerate from supersonic speeds, or a low fuel usage in-flight trajectory ... or a myriad of other tangible, quantifiable and scientifically justifiable reasons.

Paul Wally
2015-Jun-12, 08:09 PM
Evolution is not the only explanation for organic chemical specificity over time.

But we're talking about life, where evolution explains even the evolution of biochemistry itself. What works on Earth in terms of realizing life-functions is probably not going to work on Titan. If there is life on Titan it evolved with a different chemistry from that of Earth-life. This is why I consider the specifics of Earth-biochemistry irrelevant to the question of life on Titan, because if there is life on Titan I reasonably expect it to have a different specific biochemistry.



Such specificivity can also occur in non-living organics in environments which can render them incapable of, or inhibit, their Evolution towards the functions of 'life'.

I think that biological evolution starts with self-replication. So the question is not how 'non-living organics' (or any other non-living chemistry) evolves directly towards the functions of life, but rather how it can result in self-replication, which is a much simpler proposition. I don't think it's about inhibiting or enhancing evolution towards life. If life itself pulls chemical evolution toward its own realization, that would only be in a metaphorical sense. What I
suppose happens is that there is a certain probability of self-replication emerging within a sufficiently complex chemical environment.

Selfsim
2015-Jun-13, 05:04 AM
But we're talking about life, where evolution explains even the evolution of biochemistry itself. What works on Earth in terms of realizing life-functions is probably not going to work on Titan. If there is life on Titan it evolved with a different chemistry from that of Earth-life. This is why I consider the specifics of Earth-biochemistry irrelevant to the question of life on Titan, because if there is life on Titan I reasonably expect it to have a different specific biochemistry. And what is the outcome of this reasoning if there is no life on Titan?

See, the difference between your stance and my own, is that mine is based on known information. Yours is conditionally dependent on what is unknown.
Thus, your dismissal of 'the specifics of Earth-biochemistry' and its intertwined relationships with the environment, (which this particular planet is known to have provided), is a tad premature, no?


I think that biological evolution starts with self-replication. So the question is not how 'non-living organics' (or any other non-living chemistry) evolves directly towards the functions of life, but rather how it can result in self-replication, which is a much simpler proposition. And Dissolution is an even simpler chemical proposition. In organics, it requires a basic molecular-level repeating charge pattern in the solute, compatibility of the same with the solvent, and sufficient external energy to host the process. These are all environment specific .. and some scenarios are known to not support the process.

I don't think it's about inhibiting or enhancing evolution towards life. If life itself pulls chemical evolution toward its own realization, that would only be in a metaphorical sense. What I suppose happens is that there is a certain probability of self-replication emerging within a sufficiently complex chemical environment.And the weight of evidence leads us towards the realisation that certain specific, sufficiently complex, chemical sets and environments can sustain the fundamental physical processes which can then feasibly result in what we recognise today as life functions, whilst others cannot.

Colin Robinson
2015-Jun-13, 05:54 AM
And Dissolution is an even simpler chemical proposition. In organics, it requires a basic molecular-level repeating charge pattern in the solute,

Are you saying that the only organic molecules which will dissolve in anything are those with repeating charge? What is your source for this assertion?

Selfsim
2015-Jun-13, 07:35 AM
Are you saying that the only organic molecules which will dissolve in anything are those with repeating charge?No.

Selfsim
2015-Jun-13, 08:14 AM
In the context of the discussion, a repeating charge pattern molecule is of greater significance than simpler sub-units.

Paul Wally
2015-Jun-13, 06:57 PM
And what is the outcome of this reasoning if there is no life on Titan?

That is what we're trying to determine; whether life on Titan is possible or not. So your question is a bit nonsensical.



See, the difference between your stance and my own, is that mine is based on known information. Yours is conditionally dependent on what is unknown.
Thus, your dismissal of 'the specifics of Earth-biochemistry' and its intertwined relationships with the environment, (which this particular planet is known to have provided), is a tad premature, no?

No, what I've said is based on reason. It's validity depends on sound reasoning and doesn't require any further 'information' than already known concepts.



And Dissolution is an even simpler chemical proposition. In organics, it requires a basic molecular-level repeating charge pattern in the solute, compatibility of the same with the solvent, and sufficient external energy to host the process. These are all environment specific .. and some scenarios are known to not support the process.

How do you know that self-replication cannot be achieved in a solvent different from water with properties different from that of water?
Again, when it comes to Titan we have to look at what is there. If there's no liquid water on Titan then what is the relevance of water?



And the weight of evidence leads us towards the realisation that certain specific, sufficiently complex, chemical sets and environments can sustain the fundamental physical processes which can then feasibly result in what we recognise today as life functions, whilst others cannot.

What weight of evidence? You're looking at one planet in the entire universe and you call it having a "weight of evidence"??

Selfsim
2015-Jun-14, 11:12 PM
And Dissolution is an even simpler chemical proposition. In organics, it requires a basic molecular-level repeating charge pattern in the solute, compatibility of the same with the solvent, and sufficient external energy to host the process. These are all environment specific .. and some scenarios are known to not support the process.How do you know that self-replication cannot be achieved in a solvent different from water with properties different from that of water?
Again, when it comes to Titan we have to look at what is there. If there's no liquid water on Titan then what is the relevance of water?i) Why do you and Colin keep bringing up the case of water?
ii) I'd like to know how self-replication can occur if dissolution of say organic polymers, is not chemically possible in a given environment. Can you please explain how you see that it is?


What weight of evidence? You're looking at one planet in the entire universe and you call it having a "weight of evidence"??It serves to remind that this particular planet provides the sole empirical basis for distinguishing all life from non-life, life's bio-chemistry, and the known constraining diagnostic tests for life. The hunt for it demands knowledge of it derived directly from Earth.

There are no such tests, nor definitions for, the so-called 'exotic life'.

I'd say that results in a pretty weighty amount of empirical evidence being sourced from this planet about life, no?

Colin Robinson: If you're still reading this thread, IMO, a more interesting discussion would be the Neish et al March 2014 study on the low temperature hydrolysis of tholins. (Or was there already a thread about this during my absence?)

Colin Robinson
2015-Jun-15, 01:11 AM
i) Why do you and Colin keep bringing up the case of water?

You brought up the issue of water, Selfsim, earlier in this thread, when you quoted from Steve Benner et al, as follows (underlining by me).



A noteworthy point here is that (from the Benner study (http://phys.org/news/2015-05-ether-compounds-dna-oily-worlds.html)):

... any genetic biopolymer able to support Darwinian evolution operating in water must have an ever-repeating backbone charge," explained Benner. "The repeating charges so dominate the physical behavior of the genetic molecule that any changes in the nucleobases that influence genetic information have essentially no significant impact on the molecule's overall physical properties."


ii) I'd like to know how self-replication can occur if dissolution of say organic polymers, is not chemically possible in a given environment. Can you please explain how you see that it is?

I don't think we know that "dissolution of say organic polymers, is not chemically possible" in Titan's surface environment. Research is ongoing about what organic compounds can and can't dissolve in liquid hydrocarbons in Titan conditions.

Steve Benner's recent study is only one instance of what is being done. He looked specifically at the class of organics known as polyethers; and he concluded that they are not sufficiently soluble in liquid hydrocarbons at Titan temperatures to function like DNA in those conditions.

Another instance of a solubility study is a laboratory experiment by Chris McKay and others, whose results were published last year. (See the report in Chemistry World, March 2014. http://www.rsc.org/chemistryworld/2014/03/saturn-moon-titan-prebiotic-soup) This team looked at the solubility of tholins (a diverse class of organics known to be present in Titan's atmosphere) in liquid ethane at Titan temperatures. They found that these compounds are more soluble that previously thought...

I think a lot more needs to be done to find out what molecules can and can't dissolve in Titan conditions, and how the molecules can or can't interact or self-organise.


Colin Robinson: If you're still reading this thread, IMO, a more interesting discussion would be the Neish et al March 2014 study on the low temperature hydrolysis of tholins. (Or was there already a thread about this during my absence?)

"Hydrolysis" is a chemical reaction involving H20. If you don't want the rest of us to bring up the topic of water, why do you keep mentioning it yourself? :)

I agree, though, that low-temperature hydrolysis of tholins is an another interesting areas of research. It is relevant to what may be happening, not in Titan's methane-ethane surface lakes, but in its likely subsurface water ocean, as well as in possible water flows in surface areas heated by vulcanism or meteor strikes (which would be comparable to lava flows here on Earth).

Selfsim
2015-Jun-15, 02:21 AM
I think this entire conversation needs to restart with a focus on the Neish etal study. Water is, and isn't relevant, depending on the scope of the considered environmental setting. (Eg: in Titan's lakes, the temperatures are just too low for liquid water. And thus far, I don't believe anyone has yet come up with a solute/solvent combination to 'fit the bill' for what may be possible inside the depths of the lakes).

Benner's research turned towards a focus on the generalised Dissolution process as far as organic chemistry goes. Whilst I can now see that the statement I quoted could be taken as being about the water solvent context, his overall research goes beyond this, (albeit at the abandonment of empirical factualities about life's overall distinguishing functions and bio-chemistry).

(McKay wasn't formally acknowledged on the actual Neish etal report, by the way. As usual, it looks like he was 'summonsed up' in his usual role of a spin-doctor, when the impications of the real science done, didn't look so good as far as the story goes .. Astrobiology's annointed 'Shane Warne', he now appears to be :p:) ).

Colin Robinson
2015-Jun-15, 03:31 AM
I think this entire conversation needs to restart with a focus on the Neish etal study.

If you want to restart the entire conversation, why not start another thread? That's what threads are for, Selfsim.


(McKay wasn't formally acknowledged on the actual Neish etal report, by the way. As usual, it looks like he was 'summonsed up' in his usual role of a spin-doctor...

In my last message I mentioned a number of separate studies, including

* one by McKay and others about tholin solubility in ethane, and
* another by Neish and others about tholin hydrolysis.

You seem to be confusing the two.

Paul Wally
2015-Jun-15, 04:43 PM
i) Why do you and Colin keep bringing up the case of water?

Because your argument is based on the premise that dissolution is not possible on the surface of Titan.
The only way I can make sense of that is to assume that you mean that it is because there is no liquid water.



ii) I'd like to know how self-replication can occur if dissolution of say organic polymers, is not chemically possible in a given environment. Can you please explain how you see that it is?

I don't know what the minimum requirements are for self-replication to occur. We probably need a solvent or just something that functions like a solvent.
Of course to investigate this question one has to look at what the function of a solvent is in making self-replication possible, then we have to look for something (on Titan) that could possibly perform the function of a solvent.



It serves to remind that this particular planet provides the sole empirical basis for distinguishing all life from non-life, life's bio-chemistry, and the known constraining diagnostic tests for life. The hunt for it demands knowledge of it derived directly from Earth.

There are no such tests, nor definitions for, the so-called 'exotic life'.

What is that 'empirical basis'? When micro-organisms were observed through a microscope for the first time, what was the 'empirical basis' for
recognizing that as life, since nothing like it was known prior to the invention of the microscope? Throughout history we had no problem recognizing all sorts of new and exotic life-forms as life, why would this suddenly become a problem when the location is a different planet?



I'd say that results in a pretty weighty amount of empirical evidence being sourced from this planet about life, no?


Perhaps you would agree that one planet is not representative of the universe. Perhaps you would only agree
to that when it suits your argument.

Selfsim
2015-Jun-16, 07:55 AM
Because your argument is based on the premise that dissolution is not possible on the surface of Titan.
The only way I can make sense of that is to assume that you mean that it is because there is no liquid water.Interesting that you should reach such a conclusion :confused:
Lack of liquid water (in the lakes) leads towards the question of what evolvable pre-biotic solutes can remain dissolved in them, given such low temperatures. The McKay cooled tholins study is about as close as anyone's come so far, and there are several signficant doubts about the model assumptions and whether or not the results provide a plausible forward progression path.

I don't know what the minimum requirements are for self-replication to occur. We probably need a solvent or just something that functions like a solvent.There's no 'probably' about it! If what we're looking for is bio-chemistry, then sustained dissolution is a fundamental necessity.

Of course to investigate this question one has to look at what the function of a solvent is in making self-replication possible, then we have to look for something (on Titan) that could possibly perform the function of a solvent.I can see little/no need for investigating such a question. (ie: unless you are calling into doubt the fundamental bases of all known bio-chemistry?)
Invoking the existence of something imaginary 'exotic life', and then adjusting that in imagination so it fits already known and established fundamental chemical relationships, (defined under physical law), and then using that as justification for initiating a scavenger hunt on Titan to discover it .. ie: 'it might be there because we imagined it might be there', in spite of there being no tests to isolate it from its environment .. all crafted to apparently confirm what is only a belief in the first place, is not following the scientific investigation process, which is initiated to explain some initial physical observation .. (which is completely absent in this case).

What is that 'empirical basis'?The total numbers of known living species (https://en.wikipedia.org/wiki/Global_biodiversity#Known_species) all producing predictable, consistent outcomes to a plethora of specific tests, affirming the idea that there exists a common (minimal) set of bio-molecules, comprised of a minimal set of organic monomers which in turn, are comprised of a minimal set of dissolving simple molecules, in a given set of environmental conditions, over known range of geological time.
When micro-organisms were observed through a microscope for the first time, what was the 'empirical basis' for recognizing that as life, since nothing like it was known prior to the invention of the microscope?

Isolation of the test sample in a highly controlled environment, was found to be of fundamental importance for producing repeatably consistent empirical results.


Throughout history we had no problem recognizing all sorts of new and exotic life-forms as life, why would this suddenly become a problem when the location is a different planet?... and detection and isolation of a sample of interest, residing on a remote planet having a completely different chemical environment, is not a fundamental 'problem' eh?


Perhaps you would agree that one planet is not representative of the universe. Perhaps you would only agree to that when it suits your argument.Well this planet is certainly not representative of Titan, in many pertinent ways, no?

Paul Wally
2015-Jun-16, 06:34 PM
Lack of liquid water (in the lakes) leads towards the question of what evolvable pre-biotic solutes can remain dissolved in them, given such low temperatures. The McKay cooled tholins study is about as close as anyone's come so far, and there are several signficant doubts about the model assumptions and whether or not the results provide a plausible forward progression path.


... and so what? Having some doubts about an hypothesis is hardly sufficient to dismiss it outright. More investigation into this and other hypotheses are
needed of course. We can't know beforehand how it's going to play out.



There's no 'probably' about it! If what we're looking for is bio-chemistry, then sustained dissolution is a fundamental necessity.I can see little/no need for investigating such a question. (ie: unless you are calling into doubt the fundamental bases of all known bio-chemistry?)

Your understanding of the term 'biochemistry' is different from mine. I think that the biochemistry that we know is one of possibly many biochemistries.
So I'm not questioning the bases of 'known biochemistry', but just trying to place it in a larger context.



Invoking the existence of something imaginary 'exotic life', and then adjusting that in imagination so it fits already known and established fundamental chemical relationships, (defined under physical law), and then using that as justification for initiating a scavenger hunt on Titan to discover it .. ie: 'it might be there because we imagined it might be there', in spite of there being no tests to isolate it from its environment .. all crafted to apparently confirm what is only a belief in the first place, is not following the scientific investigation process, which is initiated to explain some initial physical observation .. (which is completely absent in this case).

This kind of rhetoric is probably just a kneejerk reaction, because it doesn't make logical sense. So what
if we imagine that something might be there? That is not to say that it is there. I also think that it is
impossible to 'confirm' something that isn't there ... so why worry?



The total numbers of known living species (https://en.wikipedia.org/wiki/Global_biodiversity#Known_species) all producing predictable, consistent outcomes to a plethora of specific tests, affirming the idea that there exists a common (minimal) set of bio-molecules, comprised of a minimal set of organic monomers which in turn, are comprised of a minimal set of dissolving simple molecules, in a given set of environmental conditions, over known range of geological time.

All pertaining to one planet??





... and detection and isolation of a sample of interest, residing on a remote planet having a completely different chemical environment, is not a fundamental 'problem' eh?

No it's not a fundamental problem, it's a practical problem. Whatever we can do on Earth we can do anywhere else, it's just a matter of getting around the practicalities.


Well this planet is certainly not representative of Titan, in many pertinent ways, no?
Um ... No it's not representative of Titan. Isn't this what I've been saying from the beginning??

Selfsim
2015-Jun-17, 03:04 AM
... I think that the biochemistry that we know is one of possibly many biochemistries.And therein lies the source of the problems encountered in this thread.

You have adopted this belief as being 'true' and thereby moved beyond what is objectively demonstrable.

You have mixed metaphysics with science, such that what is 'true', is what follows from whatever postulates you have chosen to believe in. (Eg:Under this same postulate, it would be true that Earth-life's metabolic tests might return meaningful results when applied to 'the possible biochemical' samples, sourced from Titan's lakes').

I have no issues with folk holding their beliefs, but I do have an issue when it is not disclosed as such, and then mixed in with scientific definitions, principles and processes.

I'd recommend using some other more nebulous term like, 'xenochemistry', until it can be demonstrated to have anything in common at all with the specific functions of Earth's 'biochemistry'.

Colin Robinson
2015-Jun-17, 05:46 AM
...I think that the biochemistry that we know is one of possibly many biochemistries.

And therein lies the source of the problems encountered in this thread.

You have adopted this belief as being 'true' and thereby moved beyond what is objectively demonstrable.

The idea that other life chemistries are possible is not a new idea. Back in 1954, the noted geneticist and biochemist J.B.S.Haldane published "The Origins of Life" in the journal New Biology, in which he argued that life elsewhere could be based on liquid ammonia rather than liquid water.

Work like this is not "belief". It is thought experiment grounded in what has been observed about the chemical properties of different liquids such water, ammonia and the hydocarbons.

Paul Wally
2015-Jun-17, 04:13 PM
And therein lies the source of the problems encountered in this thread.

You have adopted this belief as being 'true' and thereby moved beyond what is objectively demonstrable.

You have mixed metaphysics with science, such that what is 'true', is what follows from whatever postulates you have chosen to believe in. (Eg:Under this same postulate, it would be true that Earth-life's metabolic tests might return meaningful results when applied to 'the possible biochemical' samples, sourced from Titan's lakes').

I have no issues with folk holding their beliefs, but I do have an issue when it is not disclosed as such, and then mixed in with scientific definitions, principles and processes.

I'd recommend using some other more nebulous term like, 'xenochemistry', until it can be demonstrated to have anything in common at all with the specific functions of Earth's 'biochemistry'.

Relax. I said that known biochemistry is one of possibly many biochemistries. Earth-biochemistry may be the only possible one,
but since we don't know that, we have to keep our options open. We will also never know whether Earth biochemistry is the only one if we don't investigate other possibilities. That's all there is to it.

Paul Wally
2015-Jun-19, 04:29 PM
How easy or difficult would it be for us to distinguish such a class of biota from an exotic mineral, an "icy precipitate" ?

I'm just wondering something now. Suppose the behaviour of a 'mineral' depends on the environment wherein it is placed.
If the conditions are right it behaves like an organism but change it's environment and it is indistinguishable from a complex mineral structure.

Colin Robinson
2015-Jun-19, 07:39 PM
I'm just wondering something now. Suppose the behaviour of a 'mineral' depends on the environment wherein it is placed.
If the conditions are right it behaves like an organism but change it's environment and it is indistinguishable from a complex mineral structure.

That would be rather like the behaviour of microbial spores here on Earth. In dry conditions, they perform none of the functions characteristic of living things — they neither feed nor excrete, neither grow nor reproduce.

Paul Wally
2015-Jun-21, 05:10 PM
That would be rather like the behaviour of microbial spores here on Earth. In dry conditions, they perform none of the functions characteristic of living things — they neither feed nor excrete, neither grow nor reproduce.

Yes, something like that ... but suppose we didn't know what the required conditions are, how would we know that they are 'microbial spores'?

Selfsim
2015-Jun-21, 11:10 PM
Yes, something like that ... but suppose we didn't know what the required conditions are, how would we know that they are 'microbial spores'?You wouldn't. 'Microbial spores' are distinguished as being 'microbial spores' specifically because they possess attributes which differ from other elements in the ecosystem they form part of (ie: Terrestrial). Take away that ecosystem backdrop, and 'microbial spores' cannot be distinguished as being such.

In other words, 'microbial spores' cannot be said to belong to some absolute 'universal ecosystem', (in spite of some 'thought experiment' which aims to adjust the controls, in order to arrive at the desired result). Ie: the distintion of exo-'microbial spores' cannot be made in any meaningful way, in advance of first finding some intriguing aspects of some exo-sample 'of interest', which then prompts the design of some test which controls certain variables thence leading onto the production of sets of consistent observations.

Colin Robinson
2015-Jun-22, 01:26 PM
Yes, something like that ... but suppose we didn't know what the required conditions are, how would we know that they are 'microbial spores'?

Interesting question... We discovered microbial spores here on Earth some time after we discovered active microbes. If we do find life on Titan, I'd expect a similar sequence of events we'll identify active life first, dormant life later.

Paul Wally
2015-Jun-22, 08:49 PM
Take away that ecosystem backdrop, and 'microbial spores' cannot be distinguished as being such.

I agree (for the most part). But perhaps an 'ecosystem' (inclusion of other organisms) is not necessarily required. What matters is how the organism interacts with its environment, whether that be biotic or abiotic.



In other words, 'microbial spores' cannot be said to belong to some absolute 'universal ecosystem'

No one here is saying that there is a 'universal ecosystem'. That would require inter-planetary interaction between lifeforms in a kind of panspermic universe.


... (in spite of some 'thought experiment' which aims to adjust the controls, in order to arrive at the desired result). Ie: the distintion of exo-'microbial spores' cannot be made in any meaningful way, in advance of first finding some intriguing aspects of some exo-sample 'of interest', which then prompts the design of some test which controls certain variables thence leading onto the production of sets of consistent observations.

As I said, don't worry about it. We're not going to discover an 'exo-sample' until we discover it, so there's no possibility of achieving the 'desired result'
without actually achieving the 'desired result'. Of course there are no guarantees because it depends on whether observation agrees with theory or not.

Selfsim
2015-Jun-22, 11:52 PM
I agree (for the most part). But perhaps an 'ecosystem' (inclusion of other organisms) is not necessarily required. What matters is how the organism interacts with its environment, whether that be biotic or abiotic. It is not 'an organism' until some test can eliminate other considerations. Therefore, 'its environment' and 'it' are one in the same.

As I said, don't worry about it. We're not going to discover an 'exo-sample' until we discover it, so there's no possibility of achieving the 'desired result' without actually achieving the 'desired result'. Are you saying 'thought experiments' cannot achieve the possbility of a 'desired result'?

Colin Robinson
2015-Jun-23, 02:01 AM
It is not 'an organism' until some test can eliminate other considerations. Therefore, 'its environment' and 'it' are one in the same.
Are you saying 'thought experiments' cannot achieve the possbility of a 'desired result'?

Are you saying "thought experiments" are a bad idea? Would you like to explain your understanding of this term "thought experiment", and why it doesn't fit in with your philosophy of science?

Selfsim
2015-Jun-23, 10:27 AM
Are you saying "thought experiments" are a bad idea? Would you like to explain your understanding of this term "thought experiment", and why it doesn't fit in with your philosophy of science?First things first here, Colin.
My question of Paul is an attempt to understand his interpretation of the scope of this much-bandied about term: 'thought experiment'.

With all due respect, I am yet to see one capable of returning consistent results, in this thread, (including the OP) .. if that's what you're asking(?)

Colin Robinson
2015-Jun-23, 12:37 PM
First things first here, Colin.
My question of Paul is an attempt to understand his interpretation of the scope of this much-bandied about term: 'thought experiment'.

As far as I can see, Paul has never used the expression "thought experiment" in this thread, Selfsim. I think I was the first to mention this "much-bandied about term", in message #49. Since then, it has been mentioned (or "bandied"?) in 3 other messages (#54, #57, and #59), all written by you...

The Wikipedia page about this term (https://en.wikipedia.org/wiki/Thought_experiment) gives quite a good overview of its history and meaning. Basically "thought experiment" is careful reasoning about the consequences of a state of affairs which may or may not exist. It's something done by mathematicians, physicists, and moral philosophers, as well as biologists such as J.B.S.Haldane whose conjecture about ammonia-based life I mentioned.

Isaac Newton performed a classic thought experiment when he considered whether it would be possible in theory to fire a cannon ball in such a way that it circled the Earth at a constant height instead of falling. He reasoned that this could indeed be done, if the cannon ball were fired horizontally, at a sufficient speed, from such a high mountain that air resistance wouldn't be an issue... His reasoning couldn't be tested, because there was no cannon powerful enough, and no mountain high enough... But this thought experiment helped him to develop his theory of universal gravitation, which explains in a single set of equations the trajectories of real cannon balls and the path of the Moon through the sky.


With all due respect, I am yet to see one capable of returning consistent results, in this thread, (including the OP)

Not sure what you mean here...

Paul Wally
2015-Jun-23, 01:44 PM
It is not 'an organism' until some test can eliminate other considerations. Therefore, 'its environment' and 'it' are one in the same.

True :surprised:... but somewhat pedantic though. Whether or not 'it' is an organism depends on how 'it' interacts with 'its' environment.


Are you saying 'thought experiments' cannot achieve the possbility of a 'desired result'?
Well, since the whole purpose of an experiment is to see what the result will be, there's no guarantee that the desired result will be achieved.
I must say though that there is some ambiguity in your term 'desired result'. Usually in the case of a thought experiment the desired result is to
answer some question. In the case of this thread I think the 'desired result' is to answer the question of how life on Titan could be possible.

Selfsim
2015-Jun-24, 02:15 AM
... Whether or not 'it' is an organism depends on how 'it' interacts with 'its' environment.'Organism' is a controversial enough definition, even here on Earth. There is much ambiguity associated with the term.
I agree that classification of some 'exo-thing', based on its interaction with its environment, seems a reasonable place to start.
However, assuming that interaction to be the same (or similar) as Earth based organisms' interaction, (ie: the 'how'), going into the enquiry about whether or not that exo-'thing' could be classified under 'organism' prior to actually applying those tests, is not following scientific (empirical) thinking ... there are broader classes of interactions between things and their environment(s) that we already know of, which might end up fitting the bill .. who knows? Such classes require elimination by testing shown to be capable of excluding them, in a given environment, on a specimen of a given type of base chemistry.
Well, since the whole purpose of an experiment is to see what the result will be, there's no guarantee that the desired result will be achieved. I must say though that there is some ambiguity in your term 'desired result'. Usually in the case of a thought experiment the desired result is toanswer some question. In the case of this thread I think the 'desired result' is to answer the question of how life on Titan could be possible.Answering some philosophical question is not a goal of science. A well designed investigative experiment typically leads to other questions .. and further experiments aimed at returning objective knowledge. Positive, non, and null results, and their respective follow-up actions, are all part of the empirical science process. The actions cannot be prescribed until the results of each step have been obtained.

In the case of discovery of a truly, scientifically unknown 'thing', performing such operations, in a thought experiment, is an oxymoron.

Colin Robinson
2015-Jun-24, 11:23 PM
'Organism' is a controversial enough definition, even here on Earth. There is much ambiguity associated with the term.
I agree that classification of some 'exo-thing', based on its interaction with its environment, seems a reasonable place to start.
However, assuming that interaction to be the same (or similar) as Earth based organisms' interaction, (ie: the 'how'), going into the enquiry about whether or not that exo-'thing' could be classified under 'organism' prior to actually applying those tests, is not following scientific (empirical) thinking ... there are broader classes of interactions between things and their environment(s) that we already know of, which might end up fitting the bill

What are these broader classes of interactions that we already know of? Which bill might they fit?

Selfsim
2015-Jun-25, 05:55 AM
... there are broader classes of interactions between things and their environment(s) that we already know of, which might end up fitting the bill .. who knows? Such classes require elimination by testing shown to be capable of excluding them, in a given environment, on a specimen of a given type of base chemistry ...What are these broader classes of interactions that we already know of?Interactions involving energy, material and information, over time. (There may be others ...)
Which bill might they fit?A 'bill of best fit' constructed by minds following scientific thinking, in order to make sense of observations of the 'exo-thing' in, (and not in), its environment.

Paul Wally
2015-Jun-25, 12:09 PM
'Organism' is a controversial enough definition, even here on Earth. There is much ambiguity associated with the term.

I don't think it's controversial, for the same reason that I don't think the question of whether Pluto is a planet is controversial. It's all about naming things and it doesn't change reality.



However, assuming that interaction to be the same (or similar) as Earth based organisms' interaction ...

Everything is similar in some respects, so your statement is meaningless.


, (ie: the 'how'), going into the enquiry about whether or not that exo-'thing' could be classified under 'organism' prior to actually applying those tests, is not following scientific (empirical) thinking ... there are broader classes of interactions between things and their environment(s) that we already know of, which might end up fitting the bill .. who knows? Such classes require elimination by testing shown to be capable of excluding them, in a given environment, on a specimen of a given type of base chemistry.Answering some philosophical question is not a goal of science. A well designed investigative experiment typically leads to other questions .. and further experiments aimed at returning objective knowledge. Positive, non, and null results, and their respective follow-up actions, are all part of the empirical science process. The actions cannot be prescribed until the results of each step have been obtained.

You want to make this awfully complicated. IF the 'exo-thing' has the characteristics we associate with organism then I think we should call it an organism.


In the case of discovery of a truly, scientifically unknown 'thing', performing such operations, in a thought experiment, is an oxymoron.

No it's not an oxymoron, but more like algebra. We can think about unknowns in a scientific way, we just call it x.

Selfsim
2015-Jun-25, 10:35 PM
I don't think it's controversial, for the same reason that I don't think the question of whether Pluto is a planet is controversial. It's all about naming things and it doesn't change reality.Nonetheless, it is controversial (https://en.wikipedia.org/wiki/Organism#Etymology)1. .. particularly when discussing non-cellular life (https://en.wikipedia.org/wiki/Organism#Non-cellular_life)2., like viruses.
Oh and yes .. it most certainly does change what science means by reality. I suspect what you mean by reality is completely different and untestable.

Everything is similar in some respects, so your statement is meaningless.Well then with this logic, looking for similarities with 'organisms', a priori, is therefore a meaningless undertaking. Glad you agree.

You want to make this awfully complicated. IF the 'exo-thing' has the characteristics we associate with organism then I think we should call it an organism.And I wasn't the one who scoped the so called 'thought experiment' we are discussing! The OP chose the scale of complexity and now you seem to have imagined it otherwise rescoped the nature of the test subject to fit your definition of 'organism'.


No it's not an oxymoron, but more like algebra. We can think about unknowns in a scientific way, we just call it x.You are not using scientific thinking. Ie:
It's all about naming things and it doesn't change reality.

Reference Quotes from Wiki:
1. "There has been controversy about the best way to define the organism and indeed about whether or not such a definition is necessary. Several contributions are responses to the suggestion that the category of "organism" may well not be adequate in biology".
2. "Viruses are not typically considered to be organisms because they are incapable of autonomous reproduction, growth or metabolism. This controversy is problematic because some cellular organisms are also incapable of independent survival ..".

Colin Robinson
2015-Jun-26, 12:27 AM
And I wasn't the one who scoped the so called 'thought experiment' we are discussing! The OP chose the scale of complexity and now you seem to have imagined it otherwise rescoped the nature of the test subject to fit your definition of 'organism'.

Were you looking at the opening post of this thread when you wrote: "The OP chose the scale of complexity" ??

The opening post asked how easy or difficult it would be to distinguish a Titan organism from a mineral, if the Titan organism (like a diatom on Earth) had a crystal-like outline and contained non-organic solid substances as well as organics.

Colin Robinson
2015-Jun-26, 02:02 AM
In the case of this thread I think the 'desired result' is to answer the question of how life on Titan could be possible.

And also the question of how easy or difficult it would be for us to distinguish between a living thing and a non-living thing there...

Some years ago, there was a thread on the topic of Titan where a contributor mentioned looking through the microscope at a solution in which mineral crystals seemed to be growing and reproducing like organisms. It was a valid warning against false positives. Minerals can look like organisms. On the other hand, organisms (such as diatoms on Earth) can look like minerals.

If life on Titan would be difficult to identify, then, logically, if Titan lacks life, this too will be difficult to ascertain.

Maybe this means that the whole question of life on Titan should be relegated to the too-hard basket. My own view is otherwise I think the question of life on Titan should be actively addressed. Answering it, one way or the other, will require not only effective technology to go there and look, but also serious thought about what the biochemistries and morphologies of Titan organisms might be like.

Selfsim
2015-Jun-26, 02:47 AM
... The opening post asked how easy or difficult it would be to distinguish a Titan organism from a mineral, if the Titan organism (like a diatom on Earth) had a crystal-like outline and contained non-organic solid substances as well as organics.Yes its certainly a problematic opening post, all right ... for the simple reason that if the 'Titan-thing' has already been classified as an 'organism' (ie: 'Titan organism' in the opening phrase above), then it has already been distinguished from a mineral ... and the ease of doing so, is automatically rendered as irrelevant.

Colin Robinson
2015-Jun-26, 07:13 AM
Yes its certainly a problematic opening post, all right ... for the simple reason that if the 'Titan-thing' has already been classified as an 'organism' (ie: 'Titan organism' in the opening phrase above), then it has already been distinguished from a mineral ... and the ease of doing so, is automatically rendered as irrelevant.

The question in the OP is essentially this: If it were life, how would we know?

Expressed in that form, do you still find the question "problematic"?

Selfsim
2015-Jun-26, 08:10 AM
The question in the OP is essentially this: If it were life, how would we know?Oh .. ok ...
So a conclusion of 'life' could be formed following a series of exhaustive tests specifically designed to eliminate other possibilities known to be consistent with each of those result sets.


Expressed in that form, do you still find the question "problematic"?Alas, the above described process for reaching a conclusion, is not conditionally dependent on the pre-condition: "If it were life". So, yes the articulation of the 'thought experiment' is still problematic .. but its getting less complex.

Paul Wally
2015-Jun-26, 01:01 PM
Nonetheless, it is controversial (https://en.wikipedia.org/wiki/Organism#Etymology)1. .. particularly when discussing non-cellular life (https://en.wikipedia.org/wiki/Organism#Non-cellular_life)2., like viruses.
Oh and yes .. it most certainly does change what science means by reality. I suspect what you mean by reality is completely different and untestable.

If you want to call viruses life, you can do that but then you will have to change your definition of 'life' to accommodate viruses. The 'controversy' is about human language convention not physical reality. I couldn't care less about such nominal 'controversies'. It doesn't matter what we 'mean' by reality, since reality is what it is.


Well then with this logic, looking for similarities with 'organisms', a priori, is therefore a meaningless undertaking. Glad you agree.
Agree to what? Your statement is meaningless because you said something about assuming similarity, well, we don't have to assume similarity, since things are always similar in some respect. Looking for organisms on Titan is a perfectly meaningful undertaking, provided we are clear on what we mean by 'organism'. We can look for Mickey Mouse on Titan provided we have clearly defined what we mean by 'Mickey Mouse'.

Paul Wally
2015-Jun-27, 03:57 PM
And also the question of how easy or difficult it would be for us to distinguish between a living thing and a non-living thing there...

Yes, although, I believe we can have this difficulty for different reasons, and not necessarily sound reasons. One reason could be that we don't
have sufficient information to determine whether the 'exo-thing' is living or non-living, and another possible reason is that we do have sufficient information but we don't know how we should classify it. The former is a real scientific problem whereas the latter is a matter of language convention.



Some years ago, there was a thread on the topic of Titan where a contributor mentioned looking through the microscope at a solution in which mineral crystals seemed to be growing and reproducing like organisms. It was a valid warning against false positives. Minerals can look like organisms. On the other hand, organisms (such as diatoms on Earth) can look like minerals.

I think that would be a case of having insufficient information, e.g. not knowing whether these crystals also perform other life functions. If however, we knew everything there is to know about these crystals and we still can't decide what it is then it's a question of 'what we should call it', i.e. language convention.



If life on Titan would be difficult to identify, then, logically, if Titan lacks life, this too will be difficult to ascertain.

I think that we should be more concerned about false negatives than false positives. Science by its very nature deals very effectively with false
positives, i.e. any positive claims are easily challenged or 'debunked' by other scientists. With a false negative we tend to 'stop looking', thus making it even harder to overturn the false negative.



Maybe this means that the whole question of life on Titan should be relegated to the too-hard basket. My own view is otherwise — I think the question of life on Titan should be actively addressed. Answering it, one way or the other, will require not only effective technology to go there and look, but also serious thought about what the biochemistries and morphologies of Titan organisms might be like.

Even if there is no life on Titan, we may still learn something that's relevant to life. For me it's more a question of how life could be possible on Titan or any other planet for that matter. It's not just a question of 'is there life' or 'isn't there life', as I wouldn't be satisfied with a straight yes/no answer either way. How can I put it ... if we discovered life on Titan, I would still want to know why, and if we can't find any, I would still want to know why not.

Colin Robinson
2015-Jun-28, 04:25 AM
Yes, although, I believe we can have this difficulty for different reasons, and not necessarily sound reasons. One reason could be that we don't
have sufficient information to determine whether the 'exo-thing' is living or non-living, and another possible reason is that we do have sufficient information but we don't know how we should classify it. The former is a real scientific problem whereas the latter is a matter of language convention.

I think that would be a case of having insufficient information, e.g. not knowing whether these crystals also perform other life functions.

Yes...



I think that we should be more concerned about false negatives than false positives. Science by its very nature deals very effectively with false
positives, i.e. any positive claims are easily challenged or 'debunked' by other scientists. With a false negative we tend to 'stop looking', thus making it even harder to overturn the false negative.

Yes, I think that's an important point. Jumping to negative conclusions can indeed prompt us to stop looking. As happened to the search for life on Mars for many years after the Viking program.


Even if there is no life on Titan, we may still learn something that's relevant to life. For me it's more a question of how life could be possible on Titan or any other planet for that matter. It's not just a question of 'is there life' or 'isn't there life', as I wouldn't be satisfied with a straight yes/no answer either way. How can I put it ... if we discovered life on Titan, I would still want to know why, and if we can't find any, I would still want to know why not.

Yes, I agree.

Selfsim
2015-Jun-28, 10:24 AM
You both appear to be be beating around the bush and missing the vital point.

The point I was leading towards in my previous responses, was that the hypothesis: "Exo-life ('life' as-we-don't-know-it) .. ie: non-carbon based, may exist on Titan", (or anywhere else other than Earth), might easily be argued to fall into the 'pink-fairy' category. The imagined nature of what 'might be' from this category, on Titan, only serves to unjustifiably further compromise the design of experiments, thereby undermining any future experiments.

The hypothesis: "Exo-life as-we-do-know-it .. ie:'exotic', carbon-based, micro-scale 'organisms' etc, may exist on Titan", (or anywhere else other than Earth), whilst easily argued as, perhaps, falling into the 'needle-in-a-haystack' category, due to the extremely low temperatures/energies on Titan, (or the vastness of the observable universe), is at least testable. However, putting aside the categorisation argument for the moment, how the experiment for this is designed and executed, (ie: resulting in the isolation of a 'needle' from amongst a 'haystack'), plays a far greater role in the success or failure of the hypothesis than the nature of the hypothesis itself .. ie: whether that hypothesis involves 'crystalline things', 'organisms', 'diatoms', or whatever ... makes little difference. One can try pulling apart the haystack straw by straw, or alternatively, burn down the entire haystack and use a magnet on the remains. The point here, (of the analogy), is that its the experimental design, which generates the 'information', which in turn, facilitates the exclusion of other options, doubts, and uncertainties about the results being attributable to a non-living geochemical environment.

So exactly how does one design and execute an experiment to go about doing this? (See Posts #64 and #71, for the starting steps). The Viking life experiments assumed metabolism, respiration and bio-chemistry as a basis for isolation. They did not succeed in doing this. Note that these bases were derived directly from the hypothesis that: "Metabolism, respiration and bio-chemistry might exist in martian soil" .. and not strictly on the principle of rigorous design and execution of the experiment itself (the lack of GC-MS sensitivity and the lack of a common sensitivity specification across all LR, PR and GC-MS experiments, serve as the smoking gun here). The Curiosity rover SAM GC-MS is thus far, also unable to isolate the specific organic reactant species from the background soil/rock drillings. The leaking MTBSTFA organic solvent and pyrolitic heating step has seriously complicated the isolation process extensively ... once again, highlighting the criticality of the experimental design and execution, above and beyond any particular favoured and believed, hypothesis. Do these same general (not specific) trends exist for: the Huygens probe, the Philae probe, the Stardust probe (to name a few)? I say unequivocally, "Yes".

"Don't keep the faith", about the hypotheses .. They are a total distraction, and only serve to undermine real science's abilities' to reliably return objective data, which is ulitmately the key factor which funds further remote exploration missions.

Adios folks ..

Selfsim
2015-Jun-28, 10:46 AM
PS:

"Don't keep the faith", about the hypotheses .. They are a total distraction, and only serve to undermine real science's abilities' to reliably return objective data, which is ulitmately the key factor which funds further remote exploration missions.... The same applies, (of course), for so-called 'thought experiments' .. which are unable to demonstrate even the minimal consistencies necessary for making anyway headway, whatsoever about such topics. (Even as far as the most basic semantical definitional issues are concerned).

Paul Wally
2015-Jun-28, 01:59 PM
The point I was leading towards in my previous responses, was that the hypothesis: "Exo-life ('life' as-we-don't-know-it) .. ie: non-carbon based, may exist on Titan", (or anywhere else other than Earth), might easily be argued to fall into the 'pink-fairy' category. The imagined nature of what 'might be' from this category, on Titan, only serves to unjustifiably further compromise the design of experiments, thereby undermining any future experiments.

Non-carbon based? Perhaps you meant non-water based life. On Titan, life would probably make use of the complex carbon chemistry there, but would use a different solvent from water.



The hypothesis: "Exo-life as-we-do-know-it .. ie:'exotic', carbon-based, micro-scale 'organisms' etc, may exist on Titan", (or anywhere else other than Earth), whilst easily argued as, perhaps, falling into the 'needle-in-a-haystack' category, due to the extremely low temperatures/energies on Titan, (or the vastness of the observable universe), is at least testable. However, putting aside the categorisation argument for the moment, how the experiment for this is designed and executed, (ie: resulting in the isolation of a 'needle' from amongst a 'haystack'), plays a far greater role in the success or failure of the hypothesis than the nature of the hypothesis itself .. ie: whether that hypothesis involves 'crystalline things', 'organisms', 'diatoms', or whatever ... makes little difference. One can try pulling apart the haystack straw by straw, or alternatively, burn down the entire haystack and use a magnet on the remains. The point here, (of the analogy), is that its the experimental design, which generates the 'information', which in turn, facilitates the exclusion of other options, doubts, and uncertainties about the results being attributable to a non-living geochemical environment.

But we're not looking for "Life as we know it" on Titan. This argument demonstrates your bias; you're placing a reasonable hypothesis in the "pink fairy" category and a completely silly hypothesis in the more respectable "needle-in-a-haystack" category.



So exactly how does one design and execute an experiment to go about doing this? (See Posts #64 and #71, for the starting steps). The Viking life experiments assumed metabolism, respiration and bio-chemistry as a basis for isolation. They did not succeed in doing this. Note that these bases were derived directly from the hypothesis that: "Metabolism, respiration and bio-chemistry might exist in martian soil" .. and not strictly on the principle of rigorous design and execution of the experiment itself (the lack of GC-MS sensitivity and the lack of a common sensitivity specification across all LR, PR and GC-MS experiments, serve as the smoking gun here).

It's easy to judge, with the luxury of hindsight. When you 'design' your experiment, it's always good to consider that you don't have that luxury.



The Curiosity rover SAM GC-MS is thus far, also unable to isolate the specific organic reactant species from the background soil/rock drillings. The leaking MTBSTFA organic solvent and pyrolitic heating step has seriously complicated the isolation process extensively ... once again, highlighting the criticality of the experimental design and execution, above and beyond any particular favoured and believed, hypothesis. Do these same general (not specific) trends exist for: the Huygens probe, the Philae probe, the Stardust probe (to name a few)? I say unequivocally, "Yes".

Really! You're now gonna play 'I-told-you-so' on technical glitches??



"Don't keep the faith", about the hypotheses .. They are a total distraction, and only serve to undermine real science's abilities' to reliably return objective data, which is ulitmately the key factor which funds further remote exploration missions.

It's not about keeping the faith, it's about understanding. As I said:


It's not just a question of 'is there life' or 'isn't there life', as I wouldn't be satisfied with a straight yes/no answer either way.
... meaning that if it were just about keeping the faith, a mere 'yes' answer would suffice to 'confirm the belief'.


Adios folks ..
:confused:

Colin Robinson
2015-Jun-28, 11:26 PM
However, putting aside the categorisation argument for the moment, how the experiment for this is designed and executed, (ie: resulting in the isolation of a 'needle' from amongst a 'haystack'), plays a far greater role in the success or failure of the hypothesis than the nature of the hypothesis itself .. ie: whether that hypothesis involves 'crystalline things', 'organisms', 'diatoms', or whatever ... makes little difference. One can try pulling apart the haystack straw by straw, or alternatively, burn down the entire haystack and use a magnet on the remains. The point here, (of the analogy), is that its the experimental design, which generates the 'information', which in turn, facilitates the exclusion of other options, doubts, and uncertainties about the results being attributable to a non-living geochemical environment...

"Don't keep the faith", about the hypotheses .. They are a total distraction, and only serve to undermine real science's abilities' to reliably return objective data, which is ulitmately the key factor which funds further remote exploration missions.

Without having a hypothesis (like "maybe there is a needle in that haystack") the question of experimental design (how to look for a needle) would not arise in the first place.

Paul Wally
2015-Jun-29, 01:57 PM
Without having a hypothesis (like "maybe there is a needle in that haystack") the question of experimental design (how to look for a needle) would not arise in the first place.

I suspect that the only kind of 'experimental design' Selfsim recognizes is of the statistical kind. Basically you "comb" the haystack to see what falls out, but you have to apply a kind of self-censorship where you have to avoid thinking about a needle whilst doing the combing. Since you're not allowed to think, you then have to wait for the data that you collected to 'speak' to you, i.e. to provide you with a hypothesis.