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Swift
2013-Apr-04, 08:45 PM
Laboratory Equipment magazine (http://www.laboratoryequipment.com/news/2013/04/titan%E2%80%99s-chemistry-prime-form-building-blocks-life?et_cid=3177024&et_rid=54636800&linkid=http%3a%2f%2fwww.laboratoryequipment.com%2f news%2f2013%2f04%2ftitan%25E2%2580%2599s-chemistry-prime-form-building-blocks-life)

A laboratory experiment at NASA's Jet Propulsion Laboratory, simulating the atmosphere of Saturn's moon Titan, suggests complex organic chemistry that could eventually lead to the building blocks of life extends lower in the atmosphere than previously thought. The results now point out another region on the moon that could brew up prebiotic materials. The paper was published in Nature Communications this week.

"Scientists previously thought that as we got closer to the surface of Titan, the moon's atmospheric chemistry was basically inert and dull," says Murthy Gudipati, the paper's lead author at JPL. "Our experiment shows that's not true. The same kind of light that drives biological chemistry on Earth's surface could also drive chemistry on Titan, even though Titan receives far less light from the sun and is much colder. Titan is not a sleeping giant in the lower atmosphere, but at least half awake in its chemical activity."


The team examined an ice form of dicyanoacetylene – a molecule detected on Titan that is related to a compound that turned brown after being exposed to ambient light in Allen’s lab 40 years ago.

In this latest experiment, dicyanoacetylene was exposed to laser light at wavelengths as long as 355 nanometers. Light of that wavelength can filter down to Titan's lower atmosphere at a modest intensity, somewhat like the amount of light that comes through protective glasses when Earthlings view a solar eclipse, Gudipati says. The result was the formation of a brownish haze between the two panes of glass containing the experiment, confirming that organic-ice photochemistry at conditions like Titan's lower atmosphere could produce tholins.

The complex organics could coat the "rocks" of water ice at Titan's surface and they could possibly seep through the crust, to a liquid water layer under Titan's surface. In previous laboratory experiments, tholins like these were exposed to liquid water over time and developed into biologically significant molecules, such as amino acids and the nucleotide bases that form RNA.

Colin Robinson
2013-Apr-07, 04:54 AM
Laboratory Equipment magazine (http://www.laboratoryequipment.com/news/2013/04/titan%E2%80%99s-chemistry-prime-form-building-blocks-life?et_cid=3177024&et_rid=54636800&linkid=http%3a%2f%2fwww.laboratoryequipment.com%2f news%2f2013%2f04%2ftitan%25E2%2580%2599s-chemistry-prime-form-building-blocks-life)

Thanks for this.

The more scientists learn about Titan, thru both direct observation and simulations, the more it confirms the relevance of Titan to study of life's origins. And given that the origin of life is the biggest unknown factor regarding distribution of life in the universe, that makes Titan an extremely important place.

fertilizerspike
2013-Apr-07, 07:47 AM
One big problem, though, there is no water ice on Titan.

cjameshuff
2013-Apr-07, 11:45 PM
One big problem, though, there is no water ice on Titan.

About half of Titan's mass is water ice.

Colin Robinson
2013-Apr-08, 10:11 PM
About half of Titan's mass is water ice.

Yes, the mainstream view of Titan's composition is that it's largely made of H2O in solid form.

A frequent argument against life on Titan is that its surface temperature is too low for liquid water. On the surface of Titan, H2O is thought to behave like rock, while methane and ethane behave more like water here on Earth.

cjameshuff
2013-Apr-08, 10:38 PM
A frequent argument against life on Titan is that its surface temperature is too low for liquid water. On the surface of Titan, H2O is thought to behave like rock, while methane and ethane behave more like water here on Earth.

Yeah, on the surface of Titan, water is a rocky mineral like silica. Huygens evidently landed on a sandy beach, with the sand probably being composed of water ice. There's evidence of volcanism, likely with slushy ammonia-water "lava". The tidal flexing of the surface seems to indicate a relatively thin (as little as 100 km) icy shell over a subsurface ocean. Returned Titanian geological samples would probably require deep refrigeration to prevent them from turning to mud or dirty water.

It's still conceivable that there might be some hydrocarbon-based life or something odder based on surface-chemistry, but it pretty much eliminates surface life as we know it. However, it's an active environment that might be suitable for life as we don't know it, which might be more interesting...

Grant Hatch
2013-Apr-09, 06:49 AM
While life "as we know it" is much easier to think about in terms that we are familiar with,.... I believe that life "will find a way" in ANY environment sufficiently energetic and within the chemically reactive temperature ranges of water analogs such as the methane possibility on Titan .....

ravens_cry
2013-Apr-09, 08:44 AM
I love how a world so alien can be so familiar as well. Those pictures taken during the descent look almost unnervingly Earth-esque.

Swift
2013-Apr-09, 01:00 PM
Yes, the mainstream view of Titan's composition is that it's largely made of H2O in solid form.

A frequent argument against life on Titan is that its surface temperature is too low for liquid water. On the surface of Titan, H2O is thought to behave like rock, while methane and ethane behave more like water here on Earth.
I think you answered this yourself.

The more scientists learn about Titan, thru both direct observation and simulations, the more it confirms the relevance of Titan to study of life's origins. And given that the origin of life is the biggest unknown factor regarding distribution of life in the universe, that makes Titan an extremely important place.
Though it would be very neat (to say the least), it almost doesn't matter if Titan itself has life. Maybe Titan is too cold for life to form. But we can see the types of pre-biotic chemistry and processes going on in various environments in the Universe.

Colin Robinson
2013-Apr-10, 02:48 AM
I think you answered this yourself.

Though it would be very neat (to say the least), it almost doesn't matter if Titan itself has life. Maybe Titan is too cold for life to form. But we can see the types of pre-biotic chemistry and processes going on in various environments in the Universe.

Yes. Finding even the simplest of life-forms on Titan would be a real breakthrough. However, the scientific importance of Titan does not depend on the presence of life.

One way of looking at life on Earth, is that it's something done by complex organic molecules. The complex organic molecules on Titan may perhaps be doing something rather different — it may not be life, or it may be a different sort of life, or we may need to find a new word other than "life" to describe it — but any of these results will tell us something about the cosmic context of the life we know.

Romanus
2013-Apr-10, 04:35 PM
I like to think of Titan as the great Urey-Miller experiment in the sky. :)

TheBrett
2013-Apr-12, 06:57 AM
Finding some form of life on Titan would be huge. It would vastly increase the possible situations in which we could imagine life arising.

potoole
2013-May-06, 04:05 AM
Why are we looking for 'life' on Titan? The temperatures on that satellite are extremely "cold". Life depends on a series of chemical reactions that should happen in quick sequences. One very important factor in the quickness of chemical reactions is heat (surrounding temperatures). Since temps on Titan are very, very cold, it seems to me that chemical reactions, on that world, would also be very, very slow. Too slow to resemble any kind of lifelike activity.

Colin Robinson
2013-May-06, 04:17 AM
Why are we looking for 'life' on Titan? The temperatures on that satellite are extremely "cold". Life depends on a series of chemical reactions that should happen in quick sequences. One very important factor in the quickness of chemical reactions is heat (surrounding temperatures). Since temps on Titan are very, very cold, it seems to me that chemical reactions, on that world, would also be very, very slow. Too slow to resemble any kind of lifelike activity.

How slow is too slow?

Slower chemical reactions might mean that growth and repair happen more slowly. By the same token, wouldn't they mean that decay happens more slowly too, so living things would have no need to repair their cells as fast?

potoole
2013-May-06, 04:28 AM
Too slow for life to begin in the first place.
PO'T


How slow is too slow?

Slower chemical reactions might mean that growth and repair happen more slowly. By the same token, wouldn't they mean that decay happens more slowly too, so living things would have no need to repair their cells as fast?

Colin Robinson
2013-May-06, 07:31 AM
Too slow for life to begin in the first place.
PO'T

Although the temperature in the upper atmosphere is much higher than the surface (just as Earth's ionosphere is hotter than Earth's surface), and lots of organic chemistry is happening there. The opening post of this thread mentions a laboratory simulation which implies that the lower atmosphere is chemically active too, despite being cooler. What sort of systems have emerged from all this chemical activity? If not life, what?

cjameshuff
2013-May-06, 03:46 PM
Too slow for life to begin in the first place.

You have no way to know this...the whole reason these experiments are being done in the first place is that there's little understanding of organic chemistry under the conditions found on Titan. And indications are that there is actually a great deal of complex and interesting chemistry going on.

JustAFriend
2013-May-06, 05:13 PM
Why are we looking for 'life' on Titan?

Because finding any kind of life anywhere in the solar system would be a game changer,
and we don't have any other Earth-like planets here. We have to go with what we can find.

potoole
2013-May-06, 08:59 PM
You have no way to know this...the whole reason these experiments are being done in the first place is that there's little understanding of organic chemistry under the conditions found on Titan. And indications are that there is actually a great deal of complex and interesting chemistry going on.

I should have said perhaps too slow for life to begin.

PO'T

Glom
2013-May-06, 10:42 PM
You have no way to know this...the whole reason these experiments are being done in the first place is that there's little understanding of organic chemistry under the conditions found on Titan. And indications are that there is actually a great deal of complex and interesting chemistry going on.

And what point does that become life? What marks the line between organic chemistry and life?

Seriously, I don't know. What is it?

Selfsim
2013-May-06, 11:10 PM
Although the temperature in the upper atmosphere is much higher than the surface (just as Earth's ionosphere is hotter than Earth's surface), and lots of organic chemistry is happening there. .. Somewhat misleading as the types of reactions we normally think about in discussing the formation of organics comprising bio-molecules, require molecular interactions (resulting also in heat transference and possible exothermic reactions all promoting increases in ambient temperatures). This typically happens lower in the atmosphere, (or at ground level), where the gas pressures and densities are greater. The types of molecules found at the lower altitudes are higher in mass from those at the higher altitudes, and form more complex organics on their path to the surface. If the 355 nanometer wavelength light permeates the upper atmosphere layers, and reaches the lower layers at reasonable intensity, so much the better. (Who knows .. it might also account for the circulation of Titan's atmospheric gases?)

I wonder what the rate of formation (of the tholins) was, (with varying light intensities and exposure times)? Ie: can the modelled pathways also account for methane formation? Does the reaction account for the 'glow' measured in the lower atmosphere? What impact does this have on the hypothetical model where surface life is consuming acetylene? (Ie: it seems like the emphasis has shifted towards formation of possible precursors for life, which differs somewhat from life consuming acetylene).

Selfsim
2013-May-06, 11:11 PM
And what point does that become life? What marks the line between organic chemistry and life?

Seriously, I don't know. What is it?Life.

Colin Robinson
2013-May-07, 04:53 AM
And what point does that become life? What marks the line between organic chemistry and life?

Seriously, I don't know. What is it?

One definition of life is "a chemical system capable of darwinian evolution".

How to apply that definition to Titan?

I suppose first we'd have to look at what sorts of chemical systems are present. Then (unless there is something about them that convincingly rules out evolution) we'd have to look at whether and how they change over time.

Colin Robinson
2013-May-07, 05:39 AM
I should have said perhaps too slow for life to begin.

PO'T

I'd agree that we can't rule that out.

It may also turn out that life anywhere does require liquid water, in which case any life would be in Titan, rather than on it.

We just won't know until we have a better look.


.. Somewhat misleading as the types of reactions we normally think about in discussing the formation of organics comprising bio-molecules, require molecular interactions (resulting also in heat transference and possible exothermic reactions all promoting increases in ambient temperatures). This typically happens lower in the atmosphere, (or at ground level), where the gas pressures and densities are greater. The types of molecules found at the lower altitudes are higher in mass from those at the higher altitudes, and form more complex organics on their path to the surface. If the 355 nanometer wavelength light permeates the upper atmosphere layers, and reaches the lower layers at reasonable intensity, so much the better. (Who knows .. it might also account for the circulation of Titan's atmospheric gases?)

I wonder what the rate of formation (of the tholins) was, (with varying light intensities and exposure times)? Ie: can the modelled pathways also account for methane formation? Does the reaction account for the 'glow' measured in the lower atmosphere?

The glow at least suggests that chemical reactions in the lower atmosphere take place fast enough to release measurable amounts of energy. Does that mean it is fast enough for life?


What impact does this have on the hypothetical model where surface life is consuming acetylene?

If life on the surface is considered a possibility, why should life in the lower atmosphere be ruled out?

I mean, surface life would mean organisms that thrive in an environment with moisture of liquid hydrocarbon. And which might also require the sorts of minerals present on Titan's surface.

Well, the lower atmosphere contains hydrocarbon moisture in the form of methane clouds.

What about minerals in the atmosphere? Well, winds are known to blow on Titan (the Huygens probe made a recording of what they sound like). Winds on Earth and on Mars often convey loose surface material (dust) into the atmosphere – if this also happens on Titan, then any organisms which require the minerals present on the surface could find the similar minerals in the lower atmosphere too.

And regarding that "glow"... Here on Earth, isn't the most common form of chemo-luminescence in fact bio-luminescence?

Someone did a calculation based on Titan surface gravity and atmospheric pressure, and found that a human who went there could fly about in the lower atmosphere using strap-on wings.

Maybe microscopic inhabitants are doing their own bit of flying right now...

Selfsim
2013-May-07, 09:16 AM
I'd agree that we can't rule that out.

It may also turn out that life anywhere does require liquid water, in which case any life would be in Titan, rather than on it.

We just won't know until we have a better look.Water 'inside Titan', is still only a 'consistent' hypothesised model with respect to the orbital planetary scale measurements at hand. It is not yet 'a given'.


The glow at least suggests that chemical reactions in the lower atmosphere take place fast enough to release measurable amounts of energy. Does that mean it is fast enough for life? Who knows - ie: unknown.

If life on the surface is considered a possibility, why should life in the lower atmosphere be ruled out?Because neither may be needed to explain measured acetylene 'depletion'.
(And the so-called 'depletion', is relative to one particular planetary model - which has now been shown to result in tholin type 'smog').

I mean, surface life would mean organisms that thrive in an environment with moisture of liquid hydrocarbon. And which might also require the sorts of minerals present on Titan's surface.None of which might be necessary to explain the data at hand, given the lab results at hand.


Well, the lower atmosphere contains hydrocarbon moisture in the form of methane clouds.

What about minerals in the atmosphere? Well, winds are known to blow on Titan (the Huygens probe made a recording of what they sound like). Winds on Earth and on Mars often convey loose surface material (dust) into the atmosphere – if this also happens on Titan, then any organisms which require the minerals present on the surface could find the similar minerals in the lower atmosphere too.And big trees, buildings and aeroplanes to get around in(?)


And regarding that "glow"... Here on Earth, isn't the most common form of chemo-luminescence in fact bio-luminescence?
From the Nov 2012 announcement on 'the glow': (http://phys.org/news/2012-11-cassini-halloween-titan-dark.html)

Scientists' best guess is that the glow is being caused by deeper-penetrating cosmic rays or by light emitted due to some kind of chemical reaction deep in the atmosphere.It would seem that they've now demonstrated that the 355 nanometer light mechanism, (UV), can explain the 'smog' and 'the glow' (ie: UV induced airglow).
Seemingly no need for anything else ..

Colin Robinson
2013-May-07, 09:54 AM
From the Nov 2012 announcement on 'the glow': (http://phys.org/news/2012-11-cassini-halloween-titan-dark.html)

Scientists' best guess is that the glow is being caused by deeper-penetrating cosmic rays or by light emitted due to some kind of chemical reaction deep in the atmosphere.
It would seem that they've now demonstrated that the 355 nanometer light mechanism, (UV), can explain the 'smog' and 'the glow' (ie: UV induced airglow).
Seemingly no need for anything else ..

I've underlined the words "light emitted due to some kind of chemical reaction deep in the atmosphere". A living metabolism that gives rise to bio-luminescence is also "light emitted due to some kind of chemical reaction".

Still, it's true the idea that it's any sort of chemical reaction is only one of two hypotheses mentioned in your quote. If it is a chemical reaction, though, it is likely to be organic chemistry (carbon chemistry), because of the very composition of Titan's atmosphere.

Selfsim
2013-May-07, 10:24 AM
I've underlined the words "light emitted due to some kind of chemical reaction deep in the atmosphere". A living metabolism that gives rise to bio-luminescence is also "light emitted due to some kind of chemical reaction".

Still, it's true the idea that it's any sort of chemical reaction is only one of two hypotheses mentioned in your quote. If it is a chemical reaction, though, it is likely to be organic chemistry (carbon chemistry), because of the very composition of Titan's atmosphere.But the point is that an atmospheric photochemical mechanism has been shown in the lab, which explains both the acetylene depletion, the smog and the airglow phenomena.

Nothing has shown a need to invoke living metabolisms/bioluminescence.

Swift
2013-May-07, 01:09 PM
Why are we looking for 'life' on Titan? The temperatures on that satellite are extremely "cold". Life depends on a series of chemical reactions that should happen in quick sequences. One very important factor in the quickness of chemical reactions is heat (surrounding temperatures). Since temps on Titan are very, very cold, it seems to me that chemical reactions, on that world, would also be very, very slow. Too slow to resemble any kind of lifelike activity.
These experiments are not about looking for life on Titan. They are about understanding the chemistry on Titan and getting insight into the type of chemistry that may have gone on in the early solar system that lead to life. A point discussed in posts 9 to 11 in this thread.

Colin Robinson
2013-May-07, 10:05 PM
But the point is that an atmospheric photochemical mechanism has been shown in the lab, which explains both the acetylene depletion, the smog and the airglow phenomena.

Nothing has shown a need to invoke living metabolisms/bioluminescence.

The quote you gave in your earlier posting about the glow referred to "some kind of chemical reaction deep in the atmosphere", which rather less specific that what you are saying now. Maybe more specific literature exists on this. I don't know.

As for explanation of acetylene depletion, that's an interesting point, but what about hydrogen depletion?

People like Chris McKay, who have looked at the question of life on Titan, focus more on hydrogen than on acetylene, because it has been understood for years that there are there are a range of feasible acetylene sinks, i.e. processes that could remove acetylene from the environment; but hydrogen depletion is more difficult to explain. Among the few possible explanations are exotic chemical reactions involving an unknown catalyst effective at those very low Titan surface temperatures, or an exotic life form.

I think it is a mistake to respond to every sign of chemical activity, or possible chemical activity, by thinking that all that chemistry means less "need to invoke living metabolisms". Metabolism is chemical activity of a peculiar sort. Surely we are more likely to find it in a chemically active environment than in a chemically inert one?

Colin Robinson
2013-May-07, 10:13 PM
These experiments are not about looking for life on Titan. They are about understanding the chemistry on Titan and getting insight into the type of chemistry that may have gone on in the early solar system that lead to life. A point discussed in posts 9 to 11 in this thread.

The way I would say this, is that study of Titan is not only about looking for life. The fact that Titan undoubtedly has a complex carbon chemistry is scientifically interesting in itself, life or no life. It also raises the tantalizing prospect that an exotic form of life might exist there.

Colin Robinson
2013-May-08, 07:45 AM
A thought experiment.

Suppose someone or something was observing Earth, studying the composition of its atmosphere. They'd detect oxygen and complex carbon compounds, also water vapor and a little carbon dioxide — much less CO2 than is found in the atmosphere of Earth's neighbor, Venus. What hypothesis might they come up with to account for these findings?

One hypothesis might be that there are chemical processes going on at or near the surface, where H2O molecules are broken down, in a endothermic reaction made possible by solar radiation and some sort of catalyst. Decomposition of water would release oxygen molecules, and enable hydrogen from the water to combine with CO2 forming comparative large molecules made up predominantly of C, H, and O.

All of which would be a completely valid scientific model — a reasonable explanation of the observable composition of Earth atmosphere. In term of what we (as Earthlings) happen to know, the above hypothesis not only reasonable, but completely true, except that it leaves something out. What it leaves out is that the catalytic chemistry (which we call photosynthesis) is associated with growing, evolving systems, known as plants.

What does this thought experiment imply in terms of Titan? Studies and modeling of atmospheric composition and chemical reactions are unlikely to enable us to distinguish between living and non-living chemistries. To identify or exclude exotic life, we'll need to do other things as well, like examining samples under a microscope.

Selfsim
2013-May-08, 09:25 AM
A thought experiment.
...
What does this thought experiment imply in terms of Titan? Studies and modeling of atmospheric composition and chemical reactions are unlikely to enable us to distinguish between living and non-living chemistries. To identify or exclude exotic life, we'll need to do other things as well, like examining samples under a microscope. ... or laser-fry the approaching multi-toothed, drooling, foul-breathed beast about to devour Colin, while he fiddles around with his microscope! :)
(... As Arnie would say .. 'Just to see if we can kill it' ... purely scientific research reasons here, of course. :) )

The point being .. it depends on the nature of the find as to what equipment, or tests, need to be applied. That decision needs to be made based on some 'finding of interest'. The model which anticipates what might be encountered, (and where), requires the gradual buildup of environmental and geological data. This then forms the basis of isolating things which don't naturally fit into the landscape. Finding a 'sample' worthy of examination, is surely becoming the name of the game in local planetary exploration(??) Such a sample could be of great scientific interest even if it isn't classifiable as 'life'. Going armed to the teeth looking for life, could quite easily result in a tragically lost opportunity to discover something completely unknown, and unexpected.

Colin Robinson
2013-May-08, 11:17 AM
... or laser-fry the approaching multi-toothed, drooling, foul-breathed beast about to devour Colin, while he fiddles around with his microscope! :)
(... As Arnie would say .. 'Just to see if we can kill it' ... purely scientific research reasons here, of course. :) )

The point being .. it depends on the nature of the find as to what equipment, or tests, need to be applied. That decision needs to be made based on some 'finding of interest'. The model which anticipates what might be encountered, (and where), requires the gradual buildup of environmental and geological data. This then forms the basis of isolating things which don't naturally fit into the landscape.

Except that living things generally do fit into the landscape which is their natural habitat.

In fact living things may constitute the landscape. Many Earth landscapes are green because of all the chlorophyl-bearing life-forms.


Finding a 'sample' worthy of examination, is surely becoming the name of the game in local planetary exploration(??) Such a sample could be of great scientific interest even if it isn't classifiable as 'life'. Going armed to the teeth looking for life, could quite easily result in a tragically lost opportunity to discover something completely unknown, and unexpected.

I agree that scientists studying a world such as Titan need to be open to the possibility of unexpected phenomena. Does that mean they shouldn't speculate or hypothesize, but should keep their minds blank? Or does it mean they should be prepared to form hypotheses and test them?

Selfsim
2013-May-08, 10:19 PM
Except that living things generally do fit into the landscape which is their natural habitat. .. Which is the reason for spending time to become attuned and familiar with what's 'natural' for the given landscape. The deviations from what seems 'natural', become the 'samples of interest'.

If one doesn't become familiar with the landscape in the first place, one will never notice the deviations from it.

This should be the primary focus in exploration of the completely unknown .. and who knows, it might result in completely different technologies form the ol' familiar ones like microscopes.
(Eg: number plate scanning technologies arise from trying to distinguish the needed information from megapixels of otherwise disinteresting background information).


In fact living things may constitute the landscape. Many Earth landscapes are green because of all the chlorophyl-bearing life-forms.See this is exactly where I'm coming from. Everywhere I can think of (on Earth), microbial life also results in some (macro) visible bio-signs (or effects). Even the Atacama desert or Antarctican extremophiles leave their mark on a soil sample .. that's how they were detected in the first place! The Marianas Trench extremophiles were simply hidden because of their relative inaccessibility in the first place.

Why all of a sudden, if we're following an 'Earth-life' model on another world, do we ignore these tell-tale signs and automatically go looking at the microscopic level expecting to find something? Why don't the speculated exo-microsopic organisms exhibit the similar macro scale signs? I know we can dream up probably hundreds of 'excuses' for this .. but each 'excuse' becomes an exception to the model .. and there just doesn't seem to be any data (evidenced) based reasons justifying those theoretical exceptions. Gee , even viruses exhibit macro level biosignatures!

The call for microscopic tools would logically follow the signs (or data) that something microscopic might be at cause in exhibiting the initial macro-level indicators.


I agree that scientists studying a world such as Titan need to be open to the possibility of unexpected phenomena. Does that mean they shouldn't speculate or hypothesize, but should keep their minds blank? Or does it mean they should be prepared to form hypotheses and test them?The value of the speculation is what I'm questioning. Speculation about where to find life on Earth is easy .. and quite a reliable method for life detection. That's because we've had billions of years to become familiarised with the nuances and sameness of various landscapes. That repository of built up knowledge is all but empty when it comes to exo-landscapes.
Is it that we've become so familiar with what we already know about our own environments, that we've forgotten where and how it came about?

Colin Robinson
2013-May-09, 12:49 AM
.. Which is the reason for spending time to become attuned and familiar with what's 'natural' for the given landscape. The deviations from what seems 'natural', become the 'samples of interest'.

If one doesn't become familiar with the landscape in the first place, one will never notice the deviations from it.

This should be the primary focus in exploration of the completely unknown .. and who knows, it might result in completely different technologies form the ol' familiar ones like microscopes.
(Eg: number plate scanning technologies arise from trying to distinguish the needed information from megapixels of otherwise disinteresting background information).

See this is exactly where I'm coming from. Everywhere I can think of (on Earth), microbial life also results in some (macro) visible bio-signs (or effects). Even the Atacama desert or Antarctican extremophiles leave their mark on a soil sample .. that's how they were detected in the first place! The Marianas Trench extremophiles were simply hidden because of their relative inaccessibility in the first place.

Why all of a sudden, if we're following an 'Earth-life' model on another world, do we ignore these tell-tale signs and automatically go looking at the microscopic level expecting to find something? Why don't the speculated exo-microsopic organisms exhibit the similar macro scale signs?

Organisms on Titan may well have tell-tale macro-scale signs, if only we knew how to read the signs. If we knew for certain how a Titan-like world would look and behave without any organisms.

For instance, the Huygens probe landed with what ESA called a "splat" (rather than a "splash" or a "thud"), which tells us something about the consistency of the sand or soil, and may relate to the amount of hydro-carbon moisture it contains. Now, we know that on Earth, soil that is rich in living or recently dead organisms has quite a different character to soils or sands that are lower in organisms.

What we don't know is what the consistency of Titan sand or soil would be like either with or without Titan organisms. To know this, we need models of the processes of erosion etc that have shaped Titan sands/soils over the centuries. Such models will inevitably contain an element of speculation.


I know we can dream up probably hundreds of 'excuses' for this .. but each 'excuse' becomes an exception to the model .. and there just doesn't seem to be any data (evidenced) based reasons justifying those theoretical exceptions. Gee , even viruses exhibit macro level biosignatures!

It's not a question of excuses. Please just consider: When bacteria are growing in a petri dish, or in a neglected corner behind the fridge, what sort of signatures do they make? The most obvious answer (I suggest) is that they give their environment a messy, turbid appearance.

So have a look at macro-level photos of Titan. Isn't it messy enough to have thriving colonies of microbes? On the other hand, can we explain the messiness in turns of big carbonaceous molecules interacting chemically? Well yes probably we can, but after all, isn't that what bio-chemistry is?


The call for microscopic tools would logically follow the signs (or data) that something microscopic might be at cause in exhibiting the initial macro-level indicators.

I'd suggest that macro-level messiness, especially in an environment with liquid solvents, carbonaceous materials, and energy flows, is a reason for looking more closely at what's happening on the micro level.


The value of the speculation is what I'm questioning. Speculation about where to find life on Earth is easy .. and quite a reliable method for life detection. That's because we've had billions of years to become familiarised with the nuances and sameness of various landscapes. That repository of built up knowledge is all but empty when it comes to exo-landscapes. Is it that we've become so familiar with what we already know about our own environments, that we've forgotten where and how it came about?

That is exactly why it is premature to ask why we can't see "obvious" signs of life on Titan.

swampyankee
2013-May-10, 08:49 AM
Titan, and its atmosphere, are interesting independent of the possibility of life. For one thing, there's a climate system which involves two organic compounds which are both involved in condensation/evaporation cycles and light-driven chemical reactions.

Hlafordlaes
2013-May-11, 12:27 AM
Titan, and its atmosphere, are interesting independent of the possibility of life. For one thing, there's a climate system which involves two organic compounds which are both involved in condensation/evaporation cycles and light-driven chemical reactions.

From the pictures and info sent back, it seems like a vast non-organic ecosystem, sort of eerie with no one there. But yes, definitely interesting, life or not.

In a quick aside, the pyromaniac in me has designs on Titan. Need seem oxygen, though.

marsbug
2013-May-28, 08:19 PM
While life "as we know it" is much easier to think about in terms that we are familiar with,.... I believe that life "will find a way" in ANY environment sufficiently energetic and within the chemically reactive temperature ranges of water analogs such as the methane possibility on Titan .....

Hmmmmmm... I apologise if I don't express this thought very well. Life is just (By far) the most complex type of self organising pattern (in behaviour and form) in a universe full of self organising patterns. Perhaps Titan, an active complex but utterly alien environment, is the place to look for new kinds of self organising pattern that may approach life's complexity but be different enough to be un-ambiguously not life?

Colin Robinson
2013-May-28, 08:41 PM
Hmmmmmm... I apologise if I don't express this thought very well. Life is just (By far) the most complex type of self organising pattern (in behaviour and form) in a universe full of self organising patterns. Perhaps Titan, an active complex but utterly alien environment, is the place to look for new kinds of self organising pattern that may approach life's complexity but be different enough to be un-ambiguously not life?

I agree that what happens on Titan could differ in all sorts of unexpected ways from what happens on Earth...

Could a self-organizing pattern approach life's complexity without evolving, or at least approaching evolution? An evolving system would be a living system, according to some definitions, even if very different from Earth life.

ASTRO BOY
2013-May-28, 09:13 PM
I agree that what happens on Titan could differ in all sorts of unexpected ways from what happens on Earth...

Could a self-organizing pattern approach life's complexity without evolving, or at least approaching evolution? An evolving system would be a living system, according to some definitions, even if very different from Earth life.



I remember someone saying [It may have been Carl Sagan] that one of the biggest catastrophes that could face man as he explores space, was to come across Alien life and not recognise it.

Swift
2013-May-28, 09:40 PM
One of the take-aways I got from the recent, long Feedback thread is that maybe what LiS needs is some tighter policing of our current rules. So you guys are the first lucky recipients of that.

Please, let's drop the metaphysics discussion (post 40) and the so-broad-it-could-cover-everything discussion (post 38 and 39) and focus tightly on Titan chemistry. If you wish to discuss these other topics, please start your own threads on them.

Thanks,

marsbug
2013-May-29, 02:35 PM
Fair enough. Wellll.... as the first post pointed out, there are sources of energy to drive chemical cycles present all the way to the surface. The presence of a liquid phase of water helps chemical reactions and cycles proceed, do we know if the same applies for liquid ethane and methane?

Swift
2013-May-29, 03:33 PM
Fair enough. Wellll.... as the first post pointed out, there are sources of energy to drive chemical cycles present all the way to the surface. The presence of a liquid phase of water helps chemical reactions and cycles proceed, do we know if the same applies for liquid ethane and methane?
You will note that the quoted reference in the OP references liquid water, such as might be found below the surface of Titan (too cold at the surface).

I can't tell you specifically what the reactions would be, but liquid ethane and methane would be a very different solvent/media than liquid water. They would be very non-polar solvents (as opposed to water, which is a polar solvent) and the solvation of ions in them would be very different.