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    Testable predictions about life on Titan

    From the thread "What do you think is the most likely explanation for the Fermi paradox"

    Quote Originally Posted by Selfsim View Post
    (Perhaps a more interesting topic) but what happens to mold spores in conditions such as Titan's?
    According to Chris McKay, there is extremely low risk of Titan's surface getting contaminated by organisms from Earth, or vice versa. Conditions are too different. He mentions this in the conclusion of his concept paper Titan as the abode of life

    What kind of testable predictions does McKay's methanogen hypothesis make?
    McKay didn't actually originate the methanogen hypothesis. But yes, he has developed testable predictions from it.

    1. Methanogens, if present, will affect levels of H2 in the atmosphere. Where methanogens are active, H2 levels will be lower.
    2. Life chemistry on Titan (as on Earth) will favour the formation of the specific organic molecules it has a use for. Because of this, a graph showing relative abundance of different organics will have spikes in it, rather than being a smooth curve.

    What are his predicted impacts the drone will have on his hypothetical methanogen?
    As I understand it, he doesn't expect any impact on their overall population, if they are there.

    If they can grow and reproduce in liquid methane and/or ethane, they have plenty of available habitat. Which won't be diminished (or extended) by a small scientific drone mission.

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    Quote Originally Posted by Colin Robinson View Post
    According to Chris McKay, there is extremely low risk of Titan's surface getting contaminated by organisms from Earth, or vice versa. Conditions are too different. He mentions this in the conclusion of his concept paper Titan as the abode of life
    As is typical of McKay, his bold assertions about the topic are unsupported in evidence. His exact words in that conclusion are:
    Quote Originally Posted by McKay
    In contrast, possibilities of contamination of Titan with water-based life from Earth are essentially zero ..
    .. so where is his (chemical) evidence about what happens when dormant, say dessicated, mold spores are released into a Titan-like physical environment? I don't think anyone has considered that (or at least, I've never seen anything on that .. Have you?)
    Last I heard, Titan is believed to be composed of half water ice, has subsurface liquid water/ammonia eutectic magma mixtures and trace stratospheric water vapour(?) Why wouldn't reactivation occur under certain conditions if those physical conditions do in fact exist on Titan? Why would his above 'prediction' rule that out (if it wasn't just all his opinion?)

    Quote Originally Posted by Colin Robinson
    McKay didn't actually originate the methanogen hypothesis. But yes, he has developed testable predictions from it.
    He's certainly also responsible for hyping it ..

    Quote Originally Posted by Colin Robinson
    1. Methanogens, if present, will affect levels of H2 in the atmosphere. Where methanogens are active, H2 levels will be lower.
    Depends on the abundance of said hypotheticals ... and 'lower' compared with what exactly?

    If they're of sufficient abundance to affect H2 levels in the atmosphere, shouldn't we also be able to get direct visual evidence of them with say, DragonFly cameras? Why doesn't his hypothesis also 'predict' that?

    Its all just speculative musing .. with virtually nothing but faith in the existence of some McKay concoted hypothetical Titan life-form backing it all up.
    What are his predicted error bars on H2 variations where life might not be inferred?
    I mean .. even the Electric Universe and Creationist folk can come up with better 'predictions' than that!

    Quote Originally Posted by Colin Robinson
    2. Life chemistry on Titan (as on Earth) will favour the formation of the specific organic molecules it has a use for. Because of this, a graph showing relative abundance of different organics will have spikes in it, rather than being a smooth curve.
    What sort of a 'prediction' is that?
    'Spikes'? Are you/he serious? 'Spikes'? Hilarious!
    (Note: I don't mean to be mean to you here if you're just interpreting 'predictions' from his musings .. Are they his predictions or just his musings? .. I'm not entirely clear on this).

    Quote Originally Posted by Colin Robinson
    As I understand it, he doesn't expect any impact on their overall population, if they are there. If they can grow and reproduce in liquid methane and/or ethane, they have plenty of available habitat. Which won't be diminished (or extended) by a small scientific drone mission.
    I was more pondering the impact of stowaway mold spores on the DragonFly's science (organics) measurements in, specifically, a Titan environment .. (ie: false positives of detection of his methanogen increased or decreased as a result?) .. (Admittedly my question wasn't at all clear on that though ...)

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    Quote Originally Posted by Selfsim View Post
    As is typical of McKay, his bold assertions about the topic are unsupported in evidence. His exact words in that conclusion are:.. so where is his (chemical) evidence about what happens when dormant, say dessicated, mold spores are released into a Titan-like physical environment? I don't think anyone has considered that (or at least, I've never seen anything on that .. Have you?)
    Last I heard, Titan is believed to be composed of half water ice, has subsurface liquid water/ammonia eutectic magma
    "Magma" is right. If Titan has subsurface liquid water, it is not only subsurface but subcrust, like liquid rock on Earth.

    mixtures and trace stratospheric water vapour(?) Why wouldn't reactivation occur under certain conditions if those physical conditions do in fact exist on Titan? Why would his above 'prediction' rule that out (if it wasn't just all his opinion?)
    The paper I linked to is about the surface of Titan as a habitat for life. It is much colder than the surface of Mars, too cold for liquid water, and is not an environment where an organism (such as mould) whose cells contained liquid water could grow and reproduce.

    Could something from Earth grow and reproduce if it found its way to Titan's magma? That's another question.

    'lower' compared with what exactly?
    ... lower compared to other regions of the atmosphere, e.g. high above the surface.

    If they're of sufficient abundance to affect H2 levels in the atmosphere, shouldn't we also be able to get direct visual evidence of them with say, DragonFly cameras? Why doesn't his hypothesis also 'predict' that?
    Consider phytoplankton here on Earth. They're of sufficient abundance to affect levels of O2 and CO2 in the atmosphere, but without a microscope the only direct visual evidence is the green tinge they give to sea water. Which is only visual evidence if you already had reason to think they use a green compound such as chlorophyl as a catalyst. How to predict what sort of colour, if any, Titan organisms would impart to the surface liquids?

    Even using a microscope, it can be difficult to distinguish microbes from mineral particles, especially when you don't know what the local minerals look like under a microscope.

    What sort of a 'prediction' is that?
    'Spikes'? Are you/he serious? 'Spikes'? Hilarious!
    Why do you find that hilarious? Is it because the word "spikes" has only one syllable, and you think multi-syllable words sound more scientific?

    (Note: I don't mean to be mean to you here if you're just interpreting 'predictions' from his musings .. Are they his predictions or just his musings? .. I'm not entirely clear on this).
    They're not just musings, and they're not just his.

    As he mentions, James Lovelock has pointed out that life chemistry is very selective in the molecules it produces and uses, compared to non-living chemistry. Two molecules which are chemically very similar can be produced in very different amounts by a biochemical system.

    He is not making predictions in the everyday sense, though. He is NOT saying that the graph of Titan's chemical compounds WILL be spiky rather than smooth. He is arguing that IF there's life on the surface of Titan THEN we can expect a spiky graph for chemical compounds instead of a smooth curve.

    I was more pondering the impact of stowaway mold spores on the DragonFly's science (organics) measurements in, specifically, a Titan environment .. (ie: false positives of detection of his methanogen increased or decreased as a result?) .. (Admittedly my question wasn't at all clear on that though ...)
    I can't see how stowaway mould spores would affect measurements of atmospheric hydrogen. And considering the amount of carbon compounds on Titan (they are much more abundant there than on Mars), I doubt that a few mould spores would much affect measurements of the relative quantities of different carbon compounds.
    Last edited by Colin Robinson; 2019-Jun-30 at 10:54 AM.

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    Quote Originally Posted by Colin Robinson View Post
    "Magma" is right. If Titan has subsurface liquid water, it is not only subsurface but subcrust, like liquid rock on Earth.
    ...
    The paper I linked to is about the surface of Titan as a habitat for life. It is much colder than the surface of Mars, too cold for liquid water, and is not an environment where an organism (such as mould) whose cells contained liquid water could grow and reproduce.

    Could something from Earth grow and reproduce if it found its way to Titan's magma? That's another question.
    Well its another question .. so for what reason would McKay rule it out in his blanketing, all encompassing, and obviously carelessly made statement, if he is not just full of speculatively motivated premises?
    The cryovolcano mechanism is also thought to bring the mixture to the surface .. and in some models, its a continuous process for replenishing the atmospheric methane.
    McKay appears as leaning towards being a 'woo-cowboy' who jumps ahead of the step-by-step methodical process of categorisation of the overall mission of exploration of new planetary environments.

    Quote Originally Posted by Colin Robinson
    ... lower compared to other regions of the atmosphere, e.g. high above the surface.
    And where's your evidence for supporting that?


    Quote Originally Posted by Colin Robinson
    Consider phytoplankton here on Earth. They're of sufficient abundance to affect levels of O2 and CO2 in the atmosphere, but without a microscope the only direct visual evidence is the green tinge they give to sea water. Which is only visual evidence if you already had reason to think they use a green compound such as chlorophyl as a catalyst. How to predict what sort of colour, if any, Titan organisms would impart to the surface liquids?
    No one would expect colors to be predictable .. but some surface visual evidence would have to be present somewhere where some 'hypothetical' atmosphere-affecting methanogen might be present (where its based on earth-life characteristics) .. and all one would therefore need, is camera capable of noticing it.

    Quote Originally Posted by Colin Robinson
    Even using a microscope, it can be difficult to distinguish microbes from mineral particles, especially when you don't know what the local minerals look like under a microscope.
    So you just blew away the need for a microscope because it doesn't sufficiently support the need for distinguishing McKay's 'might be there', yet testable, speculative microbes from minerals?

    Quote Originally Posted by Colin Robinson
    Why do you find that hilarious? Is it because the word "spikes" has only one syllable, and you think multi-syllable words sound more scientific?
    I'm not the subject here .. McKay's claim is .. was it his word, or did it come from somewhere else? Where's his evidence for such an obviously ludicrous mythical 'graph showing relative abundance of organics' claim?

    Quote Originally Posted by Colin Robinson
    They're not just musings, and they're not just his.
    So his woo has already propagated to others then? Before the basic surface surveys have even started then? And that's what he thinks is 'being scientific'?

    Quote Originally Posted by Colin Robinson
    As he mentions, James Lovelock has pointed out that life chemistry is very selective in the molecules it produces and uses, compared to non-living chemistry. Two molecules which are chemically very similar can be produced in very different amounts by a biochemical system.
    James Lovelock was speaking about Earth-life chemistry .. supported from evidence taken from Earth's biosphere .. Not some speculative 'Titan microbe' which relies solely on hijacking that term, and its definition, by taking it out of its contextual basis of evidence.

    Quote Originally Posted by Colin Robinson
    He is not making predictions in the everyday sense, though. He is NOT saying that the graph of Titan's chemical compounds WILL be spiky rather than smooth. He is arguing that IF there's life on the surface of Titan THEN we can expect a spiky graph for chemical compounds instead of a smooth curve.
    So all he's doing is arguing then(?) .. and not getting on with doing science. He's an arguer then .. and not being a scientist.

    Quote Originally Posted by Colin Robinson
    I can't see how stowaway mould spores would affect measurements of atmospheric hydrogen. And considering the amount of carbon compounds on Titan (they are much more abundant there than on Mars), I doubt that a few mould spores would much affect measurements of the relative quantities of different carbon compounds.
    Well using Curiosity's SAM organics lab's mass spectrometer sensitivity as a guideline, I think you may be mistaken about that. If a mould spore turned up in the sampling chain somehow I don't think it'd have much trouble picking it up by its organic mass difference from the background levels .. We can all imagine the hype that would then ensue ... (Which of course would, hypothetically speaking, then clearly demonstrate McKay etal's non-scientific purpose ...)

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    Quote Originally Posted by Selfsim View Post
    So all he's doing is arguing then(?) .. and not getting on with doing science. He's an arguer then .. and not being a scientist.
    Do you think that developing a logical argument isn't part of science?

    Is science (in your view) just a matter of making general observations, never considering the implications of what your observe, never developing and testing a hypothesis about it?

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    Examples

    Quote Originally Posted by Colin Robinson View Post
    Do you think that developing a logical argument isn't part of science?

    Is science (in your view) just a matter of making general observations, never considering the implications of what your observe, never developing and testing a hypothesis about it?
    How many observations of life on Titan do you have?
    I'm not a hardnosed mainstreamer; I just like the observations, theories, predictions, and results to match.

    "Mainstream isn’t a faith system. It is a verified body of work that must be taken into account if you wish to add to that body of work, or if you want to change the conclusions of that body of work." - korjik

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    Speaking of how words are used, you asked earlier in this thread about Chris McKay's use of "spike"...

    Quote Originally Posted by Selfsim View Post
    ... was it his word, or did it come from somewhere else?
    One of the definitions of "spike" in The Free Dictionary:

    "7.a. A sharp rise followed by a sharp decline in a graph or in the tracing of a scientific instrument."

    This is the sense in which McKay used the term in his concept paper about Titan as an abode for life.

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    Quote Originally Posted by Colin Robinson View Post
    Speaking of how words are used, you asked earlier in this thread about Chris McKay's use of "spike"...
    You're bogged down in semantics here.

    The laughable point is about McKay's supposedly humungously earth-shattering 'prediction'.

    See the attachment which shows real-life GCMS (SAM) plots of the martian Cumberland mudstone sample and then try and argue that predicting 'spikes' in a relative abundance graph of organics in some sample as being 'evidence of life', is anything other than just pure linguistic rubbish!
    Attached Images Attached Images

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    No life on Titan expert here (either?), but if life is on Titan, as say, some kind of a facsimile of extreme sub-zero microbes, then life is most likely probable on all the other top contenders such as Mars, Europa, Enceladus, others such as Pluto & Ceres.

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    Quote Originally Posted by Spacedude View Post
    No life on Titan expert here (either?), but if life is on Titan, as say, some kind of a facsimile of extreme sub-zero microbes, then life is most likely probable on all the other top contenders such as Mars, Europa, Enceladus, others such as Pluto & Ceres.
    Yes .. that's an argument consistent with McKay's.
    So why isn't there visible evidence of it on Mars? Which is of course a rhetorical question .. (just staying consistent with McKay's own logical line of argument here) .. because its pretty clear that even IF its not found underground by sub-surface drilling .. they'll be more ​excuses reasoning for why it wasn't .. and so the existence of the speculative/hypothetical martian life-form meme continues forever ..

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    Quote Originally Posted by Spacedude View Post
    No life on Titan expert here (either?), but if life is on Titan, as say, some kind of a facsimile of extreme sub-zero microbes, then life is most likely probable on all the other top contenders such as Mars, Europa, Enceladus, others such as Pluto & Ceres.
    Because all these places seem to have subsurface liquid water?

    The thing is, Titan not only has subsurface water, it also has a much thicker atmosphere than any of the places you've mentioned. The upper atmosphere is chemically very active, and generates an energy-rich mixture of hydrogen and organic compounds. Plus, Titan has stable bodies of liquid (rivers, lakes, seas) on its surface, which are composed of liquid methane and ethane. And liquid precipitation in its atmosphere (rain, fog, etc) which feeds the rivers and lakes.

    These features make it a natural chemical laboratory unique in the solar system, whether there is life there on not.

    If it has living things in its subsurface liquid water, they might be chemically somewhat like the low-temperature Earth microbes you mentioned.

    But there's also the possibility of living things at the surface, which would need to be chemically quite different.

    Although all living things on Earth depend on liquid water to do their internal chemistry, scientists have long been interested in the idea of a different liquid (or combination of liquids) having a comparable function somewhere else. Titan's surface is a test case for this idea.

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    Quote Originally Posted by Spacedude View Post
    No life on Titan expert here (either?), but if life is on Titan, as say, some kind of a facsimile of extreme sub-zero microbes, then life is most likely probable on all the other top contenders such as Mars, Europa, Enceladus, others such as Pluto & Ceres.
    Titan is lousy with hydocarbons - the basis for life as we know it. That's what makes it a good candidate.

    Some of those you list also have huge amounts of hydrocarbons, but not all.

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    Now we can't be entirely sure ... but I think the dude in glasses in this link might be McKay(?)



    .. Oh well .. at least that's testable without having ta go ta Titan, I suppose(?)

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    Quote Originally Posted by Colin Robinson
    2. Life chemistry on Titan (as on Earth) will favour the formation of the specific organic molecules it has a use for. Because of this, a graph showing relative abundance of different organics will have spikes in it, rather than being a smooth curve.
    ...
    Quote Originally Posted by Colin Robinson
    McKay's point is not simply about "a relative abundance graph of organics". It is about relative abundance of chemically related organics. Related, in the sense that e.g. two different amino acids with similar numbers of carbon atoms are related.

    The spikes in your attachment would be relevant IF you could show that the low points between them correspond to abundance of molecules that are related (as closely as two amino acids) to molecules whose abundance is indicated by the spikes.

    McKay's prediction may or may not be earth-shattering, but at least it is testable...
    This is such a dumb ‘prediction’, its hard to know where to start.

    A sample taken from Titan’s surface tholins is already expected to contain, (for eg), amino acids. Determining the presence of such molecules firstly requires classifying by molecular weight (using a mass spectrometer), but this is by no means sufficient for determining whether or not such molecules are actually biomolecules. Tholins are already known to contain many different structural isomers for a given mass molecule, so determining the isomers is vital before concluding biologically relevant content (biomolecules).

    So, any measure of McKay’s ‘relative abundance of different organics’ in a Titan sample, is already expected to include a wide variety of non biomolecular isomers which will produce ‘spikes’ in the detection spectrum window of ‘organics’, due to the isomer diversity alone .. and this has absolutely nothing to do with ‘life chemistry’.

    McKay’s ‘prediction’ is completely moot .. its not even worthy of being stated .. let alone the paper its written on!
    Last edited by Selfsim; 2019-Jul-07 at 08:58 AM. Reason: Corrected attribution

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    Quote Originally Posted by Selfsim View Post
    Originally Posted by Colin Robinson (on behalf of McKay)
    The first nine words of your message already contain a quite serious misrepresentation.

    My postings here are on no-one's “behalf” except my own.

    Do you understand that, Selfsim?
    Last edited by Colin Robinson; 2019-Jul-07 at 08:39 AM.

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    Quote Originally Posted by Colin Robinson View Post
    The first nine words of your message already contain a quite serious misrepresentation.

    My postings here are on no-one's “behalf” except my own.

    Do you understand that, Selfsim?
    Ok then .. I was merely trying to give the benefit of the doubt .. I asked previously whether or not the wording in these 'predictions' was yours or McKays .. You left that ambiguous .. so I was unsure .. If you like, I shall correct it.

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    Quote Originally Posted by Selfsim View Post
    Ok then .. I was merely trying to give the benefit of the doubt .. I asked previously whether or not the wording in these 'predictions' was yours or McKays .. You left that ambiguous .. so I was unsure .. If you like, I shall correct it.
    Thank you for correcting the "on behalf" bit. You can check exactly how McKay worded his predictions by following the link I provided in the opening post, that goes to his paper.
    Quote Originally Posted by Selfsim View Post
    ...

    This is such a dumb ‘prediction’, its hard to know where to start.

    A sample taken from Titan’s surface tholins is already expected to contain, (for eg), amino acids. Determining the presence of such molecules firstly requires classifying by molecular weight (using a mass spectrometer), but this is by no means sufficient for determining whether or not such molecules are actually biomolecules. Tholins are already known to contain many different structural isomers for a given mass molecule, so determining the isomers is vital before concluding biologically relevant content (biomolecules).

    So, any measure of McKay’s ‘relative abundance of different organics’ in a Titan sample, is already expected to include a wide variety of non biomolecular isomers which will produce ‘spikes’ in the detection spectrum window of ‘organics’, due to the isomer diversity alone .. and this has absolutely nothing to do with ‘life chemistry’.

    McKay’s ‘prediction’ is completely moot .. its not even worthy of being stated .. let alone the paper its written on!
    I don't think you understand McKay's point. Perhaps because my summary was too brief and sketchy...

    He says: " a biological distribution of molecules would be a series of relatively sharp spikes while an abiotic distribution would be smooth." Note that he doesn't just say "spikes", he says "relatively sharp spikes". By "relatively" he means: in comparison to an abiotic distribution.

    You mention the diversity of molecules produced on Titan by abiotic processes. That diversity would indeed mean lots of little spikes, but the broad outline would still be smooth. If McKay's hypothesis is correct, a series of relatively sharp spikes, corresponding to molecules favoured by Titan biology, would be present if there are biological processes happening, even if there were abiotic processes happening as well.

    The molecules showing up as relatively sharp spikes would not necessarily be those which are biologically significant on Earth, such as amino acids and lipids. They would be molecules which in Titan conditions have biologically useful properties such as functioning as catalysts (as amino acid polymers do in Earth conditions) or forming membranes (as lipids do in Earth conditions).
    Last edited by Colin Robinson; 2019-Jul-07 at 01:02 PM.

  19. 2019-Jul-07, 11:02 AM

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    Quote Originally Posted by Colin Robinson
    He says: " a biological distribution of molecules would be a series of relatively sharp spikes while an abiotic distribution would be smooth." Note that he doesn't just say "spikes", he says "relatively sharp spikes". By "relatively" he means: in comparison to an abiotic distribution.
    Its still double-talk.
    ‘Biotic’ and ‘abiotic’ molecules aren’t defined by their relative abundances (ie: ’spikes’ or no ‘spikes’, ‘smooth’ or not ‘smooth’). We’re talking about organic chemistry here.
    He’s trying to impose his fantasies onto the outcome of yet another fantasised hypothetical measurement, whilst ignoring already known chemistry.

    Quote Originally Posted by Colin Robinson
    You mention the diversity of molecules produced on Titan by abiotic processes.
    No .. the diversity of amino acids and their isomers is an outcome of organic chemistry in a natural environment.

    At the stage this becomes relevant during the detection/sample treatment process, ‘abiotic’ and ‘biotic’ is unknown.

    Quote Originally Posted by Colin Robinson
    That diversity would indeed mean lots of little spikes, but the broad outline would still be smooth. If McKay's hypothesis is correct, a series of relatively sharp spikes, corresponding to molecules favoured by Titan biology, would be present if there are biological processes happening, even if there were abiotic processes happening as well.
    Pure codswallop.

    Isomers have the same molecular weight as biomolecules.
    A subset of amino acids are classified as biomolecules.
    The distributions of amino acids and their isomers will look the same as a biomolecule distribution in a tholin dominated landscape.

    Quote Originally Posted by Colin Robinson
    The molecules showing up as relatively sharp spikes would not necessarily be those which are biologically significant on Earth, such as amino acids and lipids. They would be molecules which in Titan conditions have biologically useful properties such as functioning as catalysts (as amino acid polymers do in Earth conditions) or forming membranes (as lipids do in Earth conditions).
    They’re still organic chemicals behaving as per known physical chemistries (which can be simulated).

    The question is not how biology can use physical properties of compounds.
    The question is: Is there biology in the first place?

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    Quote Originally Posted by Selfsim View Post
    Its still double-talk.
    ‘Biotic’ and ‘abiotic’ molecules aren’t defined by their relative abundances (ie: ’spikes’ or no ‘spikes’, ‘smooth’ or not ‘smooth’).
    Biomolecules are defined by the criterion that they are produced and used by biota, i.e. living things.

    Therefore, in any environment with enough biota to affect the overall chemistry, these particular molecules will be more abundant than they would otherwise be.

    They’re still organic chemicals behaving as per known physical chemistries (which can be simulated).
    Of course they are organic compounds... The point is that living things contain selective catalysts which produce certain very specific organic molecules and not other (very chemically similar) ones. That is what enables biota to grow and reproduce while keeping the same chemical composition.

    The question is not how biology can use physical properties of compounds.
    The question is: Is there biology in the first place?
    The question McKay is addressing is: how can we detect biology if it is there in the first place?
    Last edited by Colin Robinson; 2019-Jul-08 at 10:04 AM.

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    Quote Originally Posted by Colin Robinson
    Quote Originally Posted by SelfSim
    The question is not how biology can use physical properties of compounds.
    The question is: Is there biology in the first place?
    The question McKay is addressing is: how can we detect biology if it is there in the first place?
    .. And that seems to be a good place to leave this discussion ..


    In summary, (and including my position on McKay’s pure speculations):
    Quote Originally Posted by SelfSim
    Quote Originally Posted by Colin Robinson
    1. Methanogens, if present, will affect levels of H2 in the atmosphere. Where methanogens are active, H2 levels will be lower.
    The cryovolcano mechanism is also thought to bring the mixture to the surface .. and in some models, its a continuous process for replenishing the atmospheric methane.
    McKay’s ‘prediction’ in this area is already accounted for by other variable geo-mechanisms such as winds interacting with surface materials and past cryovolcanic eruptions which bring mantle materials to the surface.


    Quote Originally Posted by SelfSim
    Quote Originally Posted by Colin Robinson
    2. Life chemistry on Titan (as on Earth) will favour the formation of the specific organic molecules it has a use for. Because of this, a graph showing relative abundance of different organics will have spikes in it, rather than being a smooth curve.
    Isomers have the same molecular weight as biomolecules.
    A subset of amino acids are classified as biomolecules.
    The distributions of amino acids and their isomers will look the same as a biomolecule distribution in a tholin dominated landscape.
    McKay’s ‘prediction’ in this area is purely dependent on his speculative premise that there are actually sizeable populations of ’living methanogens’ on the surface of Titan. Without them, his ‘prediction’ is completely useless and also flies in the face of already lab-demonstrated, understood (and expected) organic geo-chemical behaviours.

    Both of his predictions are completely moot and will only serve as an ‘I told you so’ following some other more worthy scientific investigation.

    DragonFly’s primary mission is to assess prebiotic chemistry for microbial habitability within its flight range. Its payload will include a mass spectrometer. Its visibility of such environments is thus constrained to its mass spectrometer results*, which is why my response to his ‘prediction 2’ above, is of key significance to the primary mission (whereas McKay's 'prediction 2' is not).


    * .. and its atmosphere-limited visual imaging.

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    Quote Originally Posted by Selfsim View Post
    Quote Originally Posted by Colin Robinson View Post
    The question McKay is addressing is: how can we detect biology if it is there in the first place?
    .. And that seems to be a good place to leave this discussion ..
    It would be a good place to start a discussion, if you were prepared to take that question seriously...

    In summary, (and including my position on McKay’s pure speculations):
    McKay’s ‘prediction’ in this area is already accounted for by other variable geo-mechanisms such as winds interacting with surface materials and past cryovolcanic eruptions which bring mantle materials to the surface.
    The prediction you're referring to here is about levels of hydrogen (H2) in different regions of the atmosphere. You've made a response which doesn't even mention H2....

    I've noticed that you said something like this earlier in the thread, when we were talking about the related question of ethane levels. Yes, it's conceivable that geological mechanisms might produce an unknown mineral catalyst affecting levels of ethane and hydrogen. But we don't yet know whether or not that is what's happening.

    McKay’s ‘prediction’ in this area is purely dependent on his speculative premise that there are actually sizeable populations of ’living methanogens’ on the surface of Titan.
    His predictions are ways of testing that model, to see whether it is actually right or not.
    Last edited by Colin Robinson; 2019-Jul-09 at 04:24 AM.

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