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Blackhole
2012-Feb-13, 03:50 AM
Of all the water reserves in our solar system, where do you think is the most likely place to find life outside of Earth?

I'm putting my money on underneath Mars surface, or in Europa's liquid ocean. Hopefully we make a discovery in my lifetime. :D

16290

Where do you think is most likely?

danscope
2012-Feb-13, 04:34 AM
You mean life like us??? Doubt it very much. You may find some lingering bacteria from another age frozen up in some ice somewhere. You can only generate so much joy over bacteria. But... if it makes you happy.... it can't be that bad....

Selfsim
2012-Feb-13, 05:19 AM
I've got a better question …

"On which of the larger bodies in this list, (moons, planets, big asteroids), have large amounts of water, actually been measured and confirmed ?"

The answer may be surprising.

There are many hypothesised 'large' volumes of water on our planets/moons, but to the best of my knowledge, Enceladus' cryo-geysers are the only hard-evidenced large bodies (confirmed by spectrographic analysis). Mars' surface water is in trace amounts, (confirmed from obiting spectrographs and minor samples taken by the rovers), and its 'large volumes' we hear about, are inferred from MARSIS ground penetrating radar, which actually measured H+ ions, (which then led to a deduction of being water, via earth-envirnment sourced models).

I'm not sure I know for sure where real, 'hard data' actually exists, (for large water bodies), from amongst the 'Our Watery Solar System' diagram ???

Regards

astromark
2012-Feb-13, 08:32 AM
Gas, liquid and solid.. bound into a slurry of mud or as crystalline particles in stones..

or as a parts of a atmosphere.. dirty dust..

You can see it matters as to what form this alleged water it to be found as... or if at all.

It's not just guess work. A level of conclusion can be graded as a probability. But it's not a known fact yet..

Being careful not to draw conclusions without all the information..

Colin Robinson
2012-Feb-13, 11:18 PM
You mean life like us???

The term in the OP is actually "life outside Earth"... Why assume that the writer means "life like us"?


You may find some lingering bacteria from another age frozen up in some ice somewhere. You can only generate so much joy over bacteria. But... if it makes you happy.... it can't be that bad....

Lingering indigenous organisms on another world – however simple or sparse they might be – would kill off lingering suspicions that only Earth has life.

Finding them within our own solar system, would mean this... When we look up at a night sky full of stars (those of us who live in a place from which stars are visible!), we are looking at life in abundance...

redshifter
2012-Feb-13, 11:40 PM
IMO finding life, any life, outside Earth but within the solar system would be HUGE! As Colin says, the implications would be significant to say the least.

Based on what we're finding out about Mars (large amounts of ice below the surface, etc), I think bacteria living deep underground might be the most likely location. Hopefully we'll be able to find out in my lifetime! Given that we've discovered life in places on Earth we thought life couldn't exist, it's possible we'll discover life beyond Earth in a completely unexpected location.

Colin Robinson
2012-Feb-13, 11:51 PM
The diagram in the OP mentions the liquid hydrocarbons on the surface of Titan.

They are not actually water, but on Titan they do watery things, like forming rain, rivers and lakes. And like liquid water, they can function as solvents for organic chemistry.

While I agree that Mars, Europa and Enceladus are possible environments for life, I think Titan is the most likely place to find life beyond Earth in the near future.

Selfsim
2012-Feb-14, 03:37 AM
The term in the OP is actually "life outside Earth"... Why assume that the writer means "life like us"?
Because that's all we're capable of searching for, and detecting.

Anything else, would be beyond 'causal detection'. (Ie: other than 'mind-probes' (whatever they are … and sci-fi).

Regards

John Jaksich
2012-Feb-14, 04:23 AM
The diagram in the OP mentions the liquid hydrocarbons on the surface of Titan.

They are not actually water, but on Titan they do watery things, like forming rain, rivers and lakes. And like liquid water, they can function as solvents for organic chemistry.

While I agree that Mars, Europa and Enceladus are possible environments for life, I think Titan is the most likely place to find life beyond Earth in the near future.



If I am not mistaken ---there has been some speculation that there is water (in some form or another) underneath the many layers of Titans hydrocarbon surface and possibly silicate crust.

I can almost bet my bottom dollar (if that is all I have)-- -but I will admit to being wrong---I will try to find my sources on this one.

Try to get back to you on this one. . . .

Selfsim
2012-Feb-14, 04:43 AM
The diagram in the OP mentions the liquid hydrocarbons on the surface of Titan. Well now here's a speculative question … (I can mach it with the best of 'em :) )… what happens if this material turns out to resemble crude oil? What impact would that have on our society ? :)


While I agree that Mars, Europa and Enceladus are possible environments for life, I think Titan is the most likely place to find life beyond Earth in the near future.Why 'most' likely ?

Regards

John Jaksich
2012-Feb-14, 04:46 AM
Here is what I have on Titan---there seems to be evidence of outgassing of methane---and this comes from the following publication by Tobie et al 2006

Further modeling by Lunine et al--cited here:


http://arxiv.org/pdf/1108.4830.pdf


The work by Tobie et al is cited in the e-print from above --Nature 2006

Selfsim
2012-Feb-14, 06:12 AM
If I am not mistaken ---there has been some speculation that there is water (in some form or another) underneath the many layers of Titans hydrocarbon surface and possibly silicate crust.

Further modeling by Lunine et al--cited here:
http://arxiv.org/pdf/1108.4830.pdf
Hi John Jaksich;
The above paper seems to invoke water as an explanation for there being no noble heavy gases other than Argon, (detected by Huygens' GCMS during its 2005 descent). And yet, the GCMS detected only condensed methane at the surface.

At best, bulk moon density calculations result in a density of the moon of 1.88g/cm3, and on the basis of this figure alone, Titan's bulk composition is inferred as being half water ice, and half 'rocky material'.

Some surface reflectometry measurements (Huygens ?) were also taken, and also seemed to be 'consistent with' the 'possibility' that 'some' surface elements may be composed of frozen ammonia/water ice .. (but that also seems to be a 'maybe').

Does anyone know for certain whether or not hard spectrographic measurements, have ever confirmed the presence of water on Titan ?

(For the life of me, I don't seem to be able to find any hard evidence of this ... anywhere. Is this all still speculation/modelling ?).
I haven't read the Tobie et al material yet, but I've read the Wiki page ... and it is not all that clear about this.
Surely, Cassini would have found some hard data in this respect ?

Regards

John Jaksich
2012-Feb-14, 06:56 AM
Hi John Jaksich;
The above paper seems to invoke water as an explanation for there being no noble heavy gases other than Argon, (detected by Huygens' GCMS during its 2005 descent). And yet, the GCMS detected only condensed methane at the surface.

At best, bulk moon density calculations result in a density of the moon of 1.88g/cm3, and on the basis of this figure alone, Titan's bulk composition is inferred as being half water ice, and half 'rocky material'.

Some surface reflectometry measurements (Huygens ?) were also taken, and also seemed to be 'consistent with' the 'possibility' that 'some' surface elements may be composed of frozen ammonia/water ice .. (but that also seems to be a 'maybe').

Does anyone know for certain whether or not hard spectrographic measurements, have ever confirmed the presence of water on Titan ?

(For the life of me, I don't seem to be able to find any hard evidence of this ... anywhere. Is this all still speculation/modelling ?).
I haven't read the Tobie et al material yet, but I've read the Wiki page ... and it is not all that clear about this.
Surely, Cassini would have found some hard data in this respect ?

Regards

I understand what you are getting at--I am in the midst of retrieving a recent article on the matter from IOP website--(unfortunately --the delivery method is currently not forthcoming)

However, in regards to your post--there may not be straight forward evidence confirming your current question. My sources---the downloaded article and a book in my possession (author: Caleb A. Scharf---Extrasolar Planets and Astrobiology -2008) offer the water clathrate explanation based upon the moon's composition relative to others around (or neaby--so to speak in terms of possible cryovolcanism)--

Scharf argues that there seems to be a probable source for the methane "rain" on Titan so the clathrate of methane from beneath serve that purpose.

Other data may not support that--if I am not mistaken--the seasonal variations of hydrocarbon "lakes" may paint an opposite picture--if there is no evidence of water under the surface--so it is a paradigm of current research that is under scrutiny as to how Titan is able to re-plenish it's tholin surface.

Those are my thoughts on the matter--currently.

Selfsim
2012-Feb-14, 06:58 AM
Gas, liquid and solid.. bound into a slurry of mud or as crystalline particles in stones..

or as a parts of a atmosphere.. dirty dust..

You can see it matters as to what form this alleged water it to be found as... or if at all.

It's not just guess work. A level of conclusion can be graded as a probability. But it's not a known fact yet..

Being careful not to draw conclusions without all the information..

Hmm .. thanks for that astromark.

I'm not sure about whether there's direct evidence for the 'slurry' you mention on Mars (??)
For example .. there's a bunch of information about Mars' water that seems contradictory to me ...
One typical story (http://www.jpl.nasa.gov/news/news.cfm?release=2007-030) is that:

New measurements of Mars' south polar region indicate extensive frozen water. The polar region contains enough frozen water to cover the whole planet in a liquid layer approximately 11 meters (36 feet) deep. A joint NASA-Italian Space Agency instrument on the European Space Agency's Mars Express spacecraft provided these data.
.. then they say ..

The polar layered deposits extend beyond and beneath a polar cap of bright-white frozen carbon dioxide and water at Mars' south pole. Dust darkens many of the layers. However, the strength of the echo that the radar receives from the rocky surface underneath the layered deposits suggests the composition of the layered deposits is at least 90 percent frozen water. One area with an especially bright reflection from the base of the deposits puzzles researchers. It resembles what a thin layer of liquid water might look like to the radar instrument, but the conditions are so cold that the presence of melted water is deemed highly unlikely.
.. so, is there or isn't there, liquid water ?

Then, towards the end of the same article, they say ...

Detecting the shape of the ground surface beneath the ice deposits provides information about even deeper structures of Mars. "We didn't really know where the bottom of the deposit was," Plaut said. "Now we can see that the crust has not been depressed by the weight of the ice as it would be on the Earth. The crust and upper mantle of Mars are stiffer than the Earth's, probably because the interior of Mars is so much colder."
Well, so if the interior is cold and stiff, why are we led to think that there may be large sub-surface liquid water ?
I just don't get it whenever I delve into this Mars water thing ... it just never seems to quite add up for me.

Why are we looking for sub-surface liquid water, if the crust and mantle are too cold (and stiff) ?

Is it possible that Mars never had any large volumes of liquid surface water, in spite of the surface structures looking like they've been eroded by liquid water ? Is it possible that something other than liquid water created these eroded formations ? (Eg: ablating CO2)?

Other geological formations would seem difficult to explain, other than by the presence of some liquid water, (during some past era) ... eg: I think evidence of gypsum has been found recently by one of the rovers (?) But is this sufficient to explain large volumes in the past (???)

These questions, hopefully, might be answered by MSL/Curiosity. I sure hope so ... because if they aren't, it seems we're doomed to even more speculation in the light of the scarcity of hard data.

Regards

Selfsim
2012-Feb-14, 07:08 AM
I understand what you are getting at--I am in the midst of retrieving a recent article on the matter from IOP website--(unfortunately --the delivery method is currently not forthcoming)

However, in regards to your post--there may not be straight forward evidence confirming your current question. My sources---the downloaded article and a book in my possession (author: Caleb A. Scharf---Extrasolar Planets and Astrobiology -2008) offer the water clathrate explanation based upon the moon's composition relative to others around (or neaby--so to speak in terms of possible cryovolcanism)--

Scharf argues that there seems to be a probable source for the methane "rain" on Titan so the clathrate of methane from beneath serve that purpose.

Other data may not support that--if I am not mistaken--the seasonal variations of hydrocarbon "lakes" may paint an opposite picture--if there is no evidence of water under the surface--so it is a paradigm of current research that is under scrutiny as to how Titan is able to re-plenish it's tholin surface.

Those are my thoughts on the matter--currently.
Many thanks for your comments, John.
Its certainly puzzling .. I try hard to keep an open mind, but everytime I look into such papers/articles/research, there is almost always, a default invocation of water to explain things. I really do question the objectivity sometimes, and our abilities to step beyond the familiar.

Many thanks for your posts and your links. They're always interesting to read. :)

Regards

Colin Robinson
2012-Feb-14, 01:01 PM
Why 'most' likely ?

Why do I think Titan is the most likely place to find life beyond Earth in the near future?

* Lots of liquid on the surface. I know the liquid on Titan's surface is not water, but how much does that matter? Liquid solvents other than water are often used by human scientists to facilitate chemical reactions in laboratories, especially in organic chemistry. Why shouldn't microbes use non-water solvents too?
* Much thicker atmosphere than Mars, Europa or Enceladus. Titan's atmosphere is somewhat thicker than Earth's, actually. But closer to Earth thickness than any other atmosphere in the solar system.
* Complex chemistry. Organic molecules produced by photolysis in the atmosphere. Compare with Mars -- we don't know that Mars even has organic molecules (more complex than methane).
* Energy sources: an atmosphere like Titan's can absorb ultraviolent light, and turn it into chemical energy which organisms could use.
* The "splat". The Huygens probe came down on Titan not with a thud, nor with a splash, but with what ESA (if I remember correctly) termed a splat: an impact consistent with a moist, mud-like surface. This means that there is stuff on Titan's surface that can hold liquids, contain them. If you think about it, contained liquid is an important characteristic of life.
* Apparent depletion of energetic molecules: dihydrogen (H2), acetylene (C2H2), ethane (C2H6). The very molecules which Titan organisms (if they exist) were expected to gobble up...

I think these are reasonable grounds for suspicion that Titan may be harboring aliens, at least microscopic ones.

They are not proof beyond reasonable doubt. But if I had to choose one place in the solar system to send space probes equipped to look for life, I would definitely choose Titan.

Colin Robinson
2012-Feb-14, 10:49 PM
Well now here's a speculative question … (I can mach it with the best of 'em :) )… what happens if this material turns out to resemble crude oil? What impact would that have on our society ? :)

Would you expect a fleet of interplanetary oil tankers, transporting Titan's hydrocarbons to Earth? They could also use Titan hydrocarbon as fuel for their own rocket motors... Which sounds very profitable, except for one catch... Rocket motors need an oxidant as well as a fuel, and Titan doesn't seem to have oxidants... which is why the hydocarbon lakes there can't catch fire, even if struck by lightning...

You could picture the fleet of space tankers transporting great tanks of oxygen from Earth to Titan, in order to then transport hydrocarbons from Titan to Earth... Eventually Titan will have no hydrocarbons left, and Earth will have no oxygen left, and someone will have made a lot of money...:)

What does the lack of oxidants say about the chances of life on Titan? Actually, it may make life more likely to have gotten started, because it's easier to build up complex organics in a hydrogen-rich environment than an oxygen-rich one. Even today on Earth, there are anaerobic organisms that neither need oxygen nor produce it.

The lack of oxidants may however limit how "like us" Titan life could be... I wouldn't expect humanoids there, or even fishoids.

Selfsim
2012-Feb-14, 11:40 PM
Why do I think Titan is the most likely place to find life beyond Earth in the near future?

* Lots of liquid on the surface. I know the liquid on Titan's surface is not water, but how much does that matter?
Goodness me ! This is almost ATM ! (Just kidding … well, sort of .. :) ). I understand where you're coming from, but in exo-planetary research, the search for liquid water is the key driver ! Are you suggesting 'the mainstream' is looking for the wrong compound (and has the wrong Habitable Zone definitions ?)

Beyond visual imaging, what kind of robotically based experiment could be designed to detect something 'living', which is non-water based ? This could be an interesting topic for another thread (?) And it might get us beyond the fascination/obsession with water, and onto thinking about technologies capable of detecting 'life' processes, rather than only familiar 'life' chemistries ! But should we go on to develop such technologies to narrow the options in exo-environment searches ?

If we go looking for something other than water-based 'life', how would we ever remotely detect it, or recognise it, as something we call 'life', other than by a pure chance discovery, brought on by physically going to a place like Titan ?

Why should we change our search/detection strategy by making Titan the exceptional case ? How many other exceptional cases might be out there ? What does this say about our present definitions of 'Habitable Zone', ... what does 'Habitable Zone' mean ? How far 'off the mark' is it ?


Liquid solvents other than water are often used by human scientists to facilitate chemical reactions in laboratories, especially in organic chemistry. Why shouldn't microbes use non-water solvents too?
* Much thicker atmosphere than Mars, Europa or Enceladus. Titan's atmosphere is somewhat thicker than Earth's, actually. But closer to Earth thickness than any other atmosphere in the solar system.But we're back to Earth-like properties and Earth-like models. Humans also synthesise new forms of life in the lab, but how does this decouple Earth-based life from the Titan conjecture ? Why are a human's actions being compared with a microbe synthesising a chemical reaction on Titan ?
Sure, the atmosphere was a direct contributor to only Earth-based 'life', but why would this contribute to the different 'life' you're hypothesising about on Titan ? What then, is the overlap with Earth's life (from a biological perspective)? What produces the hypothesised fairly radical differences from Earth based life ?

* Complex chemistry. Organic molecules produced by photolysis in the atmosphere. Compare with Mars -- we don't know that Mars even has organic molecules (more complex than methane).
* Energy sources: an atmosphere like Titan's can absorb ultraviolent light, and turn it into chemical energy which organisms could use.Regarding my underline: What chemical basis/properties of these 'organsims' would lead towards such a possibility ? Where does the energetic UV come from (ie: is there a plausible source, (or accumulation from multiple sources), of sufficient energy to do this ?)

* The "splat". The Huygens probe came down on Titan not with a thud, nor with a splash, but with what ESA (if I remember correctly) termed a splat: an impact consistent with a moist, mud-like surface. This means that there is stuff on Titan's surface that can hold liquids, contain them. If you think about it, contained liquid is an important characteristic of life.

Yep (and including your first and third points).. all good lines of enquiry … and perhaps one could use these points as the skeleton design for a customised Titan-environment-like robotic probe. But what if the Lunine et al process is the correct explanation for there being no noble heavy gases, other than Argon .. and, (reasonably), there is water present ?


* Apparent depletion of energetic molecules: dihydrogen (H2), acetylene (C2H2), ethane (C2H6). The very molecules which Titan organisms (if they exist) were expected to gobble up…Well, there may be other processes which could explain this .. you have mentioned previously the Krebs cycle which results in O2. What makes the depletion of the above molecules exceptional, leading towards a conclusion of possible life ? (Other than energy content. In some environments similar to Titan's, these molecules would be toxic to life, and would extinguish it as soon as it got a foothold !)

I think these are reasonable grounds for suspicion that Titan may be harboring aliens, at least microscopic ones.
They are not proof beyond reasonable doubt. But if I had to choose one place in the solar system to send space probes equipped to look for life, I would definitely choose Titan.
You would choose a Titan environment over say, environments exhibiting large volumes of liquid water, eh ?

The basis of any 'reason', in the study of the non-linear synergies between the environment and biology in physical reality, is prior evidence. The complexity of life distinguishes it from the determinism inherent in pure chemistry and classical physics, without excluding it from such.

In biology, if there is no 'prior evidence', there can easily be no distinguishable 'reason'. Similarly, there can be no distinguishable 'doubt'. There can be no distinguishable 'cause'. There can be no distinguishable 'effect'. These are mundane realities.

A chance discovery, which results in hard data, which could be used in a comparative model, is the only 'reasonable' mechanism which would lead to such data .. and 'reason'.

Interesting.

Regards

Selfsim
2012-Feb-14, 11:54 PM
Would you expect a fleet of interplanetary oil tankers, transporting Titan's hydrocarbons to Earth? I should clarify …

In the (purely hypothetical) scenario of chemically analysed ground-based hydrocarbons on Titan, being found to be indistinguishable from what we refer to as 'crude oil', and there is no evidence of prior 'life' there, (ie: no 'fossils'), then might Earth's have been caused by the same physical process ? (Ie: entirely independent of degenerated life-based organics ?) :confused:

Regards

astromark
2012-Feb-15, 08:05 AM
This thread was about water in the solar system.. and we find ourselves talking of hydrocarbons on Titan...

and I agree with 'Selfsim'...

We need to address this in its own thread.. I want a lot more information please...?

John Jaksich
2012-Feb-15, 10:13 AM
This thread was about water in the solar system.. and we find ourselves talking of hydrocarbons on Titan...

and I agree with 'Selfsim'...

We need to address this in its own thread.. I want a lot more information please...?


Well in terms of Titan --there is the question of whether water clathrates are source for replenishing methane into the Titan's atmosphere. The mechanistic detail (if you can pardon the term mechanism) is that cryovolcanism seems to be a source from under the frozen hydrocarbon surface that serves to release methane.


That seems to be a current line of research for Titan. . . .

In regards to other Solar System bodies---Ice seems to be almost everywhere.

I listened to a BAUT Google+ hangout (featured at the current site) talking about certain aspects on a possible (under the crust) Martian water.

Lake Vostok seems to have water that is so pure --we (humanity) may not have seen such before and there is an inkling of evidence of new types of life at Lake Vostok (extremophiles that have no resemblence to current models of life).

That is just to scratch the surface of what I listened to earlier yesterday.

Colin Robinson
2012-Feb-15, 10:31 AM
Goodness me !

Thanks for your lively response!


This is almost ATM ! (Just kidding … well, sort of .. :) ). I understand where you're coming from, but in exo-planetary research, the search for liquid water is the key driver ! Are you suggesting 'the mainstream' is looking for the wrong compound (and has the wrong Habitable Zone definitions ?)

Well, I am suggesting that in this area there is a debate going on within the mainstream. Late last year the peer-reviewed scientific journal Astrobiology published a paper by Dirk Schulze-Makuch and a number of others about comparative habitability of various worlds within and beyond the solar system. The paper assessed planets and moons according to two different measures, an Earth Similarity Index (ESI), and a Planetary Habitability Index (PHI). On the ESI, high scoring worlds included Mars and Mercury. However, on the PHI, Titan was rated as currently the most habitable of known worlds, after Earth. Here is a link to a summary of the paper...

http://cosmiclog.msnbc.msn.com/_news/2011/11/22/8956644-which-alien-worlds-are-most-livable


Beyond visual imaging, what kind of robotically based experiment could be designed to detect something 'living', which is non-water based ?

Mass spectrometer, to get an inventory of chemical compounds.


Why are a human's actions being compared with a microbe synthesising a chemical reaction on Titan ?

Because the same laws of chemistry apply to the microbe and the human chemist. Just as the same laws of physics apply to a pendulum and a planet.


Where does the energetic UV come from (ie: is there a plausible source, (or accumulation from multiple sources), of sufficient energy to do this ?)

It comes from the Sun. Yes, there is enough energy to break methane molecules apart, liberating dihydrogen (H2) and a range of organic compounds including acetylene and ethane. I think you will find this is the mainstream understanding of Titan's atmosphere.


Well, there may be other processes which could explain this .. you have mentioned previously the Krebs cycle which results in O2. What makes the depletion of the above molecules exceptional, leading towards a conclusion of possible life ?

You are quite right – the apparent decomposition of acetylene and ethane on Titan may be due to a non-living catalyst, rather than being the work of microbes. We won't know until we get a closer look at Titan.


In some environments similar to Titan's, these molecules would be toxic to life, and would extinguish it as soon as it got a foothold

Meat for one organism is poison for another. Even here on Earth, a oil spill at sea is a disaster for many life forms... but there are also microbes that break down the oil slick... in other words, they make a meal out of it.


But what if the Lunine et al process is the correct explanation for there being no noble heavy gases, other than Argon .. and, (reasonably), there is water present ?

The term "noble gases" refers to what used to be called "inert gases" – helium, xenon, neon etc. I am not sure what these have to do with question of life on Titan.

Regarding water, as I understand it, the mainstream view is that Titan has plenty of water ice, but on the surface it behaves like rock or sand – it never turns into liquid, except in the sort of conditions where rock becomes lava. Subsurface liquid water, as in the case of Europa, Enceladus, and other outer moons, is a distinct possibility. Or a mixture of liquid water and liquid ammonia.

Which makes the Titan all the more complex and interesting as a huge natural chemical laboratory, whether or not actual living things have been invented there...

Selfsim
2012-Feb-17, 03:23 AM
Thanks for your lively response!
:lol:

Well, I am suggesting that in this area there is a debate going on within the mainstream. Late last year the peer-reviewed scientific journal Astrobiology published a paper by Dirk Schulze-Makuch and a number of others about comparative habitability of various worlds within and beyond the solar system. The paper assessed planets and moons according to two different measures, an Earth Similarity Index (ESI), and a Planetary Habitability Index (PHI). On the ESI, high scoring worlds included Mars and Mercury. However, on the PHI, Titan was rated as currently the most habitable of known worlds, after Earth. Here is a link to a summary of the paper...

http://cosmiclog.msnbc.msn.com/_news/2011/11/22/8956644-which-alien-worlds-are-most-livable

Thanks for that ... interesting.
Fyi: the "Planetary Habitability Laboratory" (http://phl.upr.edu/projects/habitable-exoplanets-catalog/methods) has a few more detailed ranking categories: (HZD, HZC, HZA, ESI, SPH, PClass and hClass).
After having read through all of this material however, I still feel the thinking overlooks significant (unconsidered) aspects (see below).


Beyond visual imaging, what kind of robotically based experiment could be designed to detect something 'living', which is non-water based ?Mass spectrometer, to get an inventory of chemical compounds.Works for the chemistry side .. but there's a whole lot more complexity, beyond just organic reactions, involved in life. Reducing a cell to its chemical components, tells us nothing about whether it is/was alive, or not. Even chirality tests are a stretch, when assuming a non-water based life model. Looking for metabolic by-products, requires having to (again) narrow the field using prior knowledge of earth life-based metabolic processes, which are likely specific to Earth.


Why are a human's actions being compared with a microbe synthesising a chemical reaction on Titan ?
Because the same laws of chemistry apply to the microbe and the human chemist. Just as the same laws of physics apply to a pendulum and a planet.This is the crux of what I'm trying to get at. Just because those laws produce repeatable, predictable results, when combined in a specific way in a lab, says absolutely zip about the influences of the majority of the non-linear processes in an exo-environment.

Life displays many characteristics of complexity. Complexity occurs in non-linear systems, which usually exhibit dynamic chaotic behaviours. The characteristics of such systems are internal and external feedback, self organised assembly, many components interacting non-linearly and, under certain conditions, extreme sensitivity to initial conditions. The sum of the components does not equal the whole. Life fits this description to a tee. If our own life matches in detail with these characterisation parameters, then it is entirely possible, even probable, (based on the frequency of appearance of non-linear systems in the natural environment), that life originated from similar initial processes (and 'systems'). Such 'systems' can be critically balanced (dynamically speaking). If the processes originating 'life' were also critically balanced, then any slight disturbance, or any slight differences in initial conditions between say, two origination life events, will render the outcome completely unpredictable. This would suggest that one cannot determine the outcome of one origination event, based on any other. Failure-to-generate-life cases, are just as likely as life-generating cases. One cannot predict one or the other outcome, because of the nature of the system.

Even if the 'originating system' was not critically balanced, external or internal influences could nudge it into such a state. There is evidence that life and its crucial biological processes, may be presently poised at criticality .

Just about everyone skims over this huge 'mainstream' elephant in the room .. beats me why ?

At any point in time, in critically balanced systems, the slightest change in any of these processes, can make or break the end result. And yet, a huge amount of emphasis is placed on the easy bit .. ie: the deterministic outcomes of organic chemistry and classical physics !

Why should this be given any more weight when compared with the influences of the overwhelming majority of non-linear natural processes ?

It just doesn't make sense for me, unless the reasons are pure guesswork, (which I think, is the honest answer).

Regarding water, as I understand it, the mainstream view is that Titan has plenty of water ice, I am not clear as to whether the presence of water has been confirmed, spectrographically (?) It seems to be invoked in various models, but this does not make it so, physically. (Happy to hear otherwise, though).

Subsurface liquid water, as in the case of Europa, Enceladus, and other outer moons, is a distinct possibility. Or a mixture of liquid water and liquid ammonia.Possibilities are one thing .. reality is another. Enceladus' water vapour has been confirmed spectrographically (by Cassini). The belief that Europa has large volumes of subsurface water goes way back to Voyager and Galileo photographic images, (and accompanying geological models), and is thus inferred. To the best of my knowledge, there is no spectrographic data in support of these models (and is thus, still highly controversial).

Regards

Colin Robinson
2012-Feb-17, 10:01 AM
Fyi: the "Planetary Habitability Laboratory" (http://phl.upr.edu/projects/habitable-exoplanets-catalog/methods) has a few more detailed ranking categories: (HZD, HZC, HZA, ESI, SPH, PClass and hClass).
After having read through all of this material however, I still feel the thinking overlooks significant (unconsidered) aspects (see below).

There is a subtle but important difference between saying a planet or moon is habitable, and saying that there is actually life on it.

The Planetary Habitability Laboratory page that you've linked to, and the article I linked to in my last posting, are both talking about habitability, and are looking at how to compare the habitability of different worlds.

Models of habitability can narrow and focus the search for life. For instance, if Europa is considered more habitable than Mercury, then it makes sense for someone looking for organisms to pay more attention to Europa than to Mercury. But this does not mean they can count on finding life in either place.

For it is another question how probable or improbable it is that life will emerge on any particular habitable world. Biologists who have looked at this question have very different views... It seems to me that your argument about complex systems relates to this second question, not to the question of habitability as such.


Looking for metabolic by-products, requires having to (again) narrow the field using prior knowledge of earth life-based metabolic processes, which are likely specific to Earth.

I agree that metabolism might differ quite a lot. On the other hand, the overall direction of metabolism would be governed by the same laws of thermodynamics as here on Earth. (One could imagine a state of affairs where Titan life-forms were governed by different principles of thermodynamics. But such a conjecture really would be ATM!) The life-forms would need a source of Gibbs free energy.

That is why astrobiologists including Chris McKay and David Grinspoon predicted that any organisms on Titan would be likely to turn hydrogen and acetylene into methane, rather than e.g. turning methane into hydrogen and acetylene.


This is the crux of what I'm trying to get at. Just because those laws produce repeatable, predictable results, when combined in a specific way in a lab, says absolutely zip about the influences of the majority of the non-linear processes in an exo-environment.

The argument I mentioned about use of non-water solvents for organic chemistry in laboratories does not prove that life will in fact emerge on a world with lots of non-water solvent.

It simple says that known laws of chemistry (based on laboratory experience) leave open the possibility of living cells based on a fluid other than water. That if we are going to look for life on other worlds, then non-water lakes or rivers should be considered as possible habitats.


Life displays many characteristics of complexity… This would suggest that one cannot determine the outcome of one origination event, based on any other. Failure-to-generate-life cases, are just as likely as life-generating cases. One cannot predict one or the other outcome, because of the nature of the system.

You may be quite right on that point.

But the question raised in the OP was where life is most likely to be found — Mars, Europa or where? Doesn't your point about the unpredictable character of life's emergence apply to all these places?


Enceladus' water vapour has been confirmed spectrographically (by Cassini).

Certainly, if a strict "follow the water" strategy is considered the best way to look for life, then Enceladus would logically be top of the list…

Extrasolar
2012-Feb-18, 04:21 PM
Because that's all we're capable of searching for, and detecting.

Anything else, would be beyond 'causal detection'. (Ie: other than 'mind-probes' (whatever they are … and sci-fi).

Regards

We are capable of searching for and detecting more than life like ours. We would find life like ours most easily, but we're made of the same stuff that everything else in the universe is made of. We can find that stuff and put 2 and 2 together, just like we have always done as humans when making discoveries. We weren't looking for microwaves before they were discovered either.

Colin Robinson
2012-Feb-18, 11:07 PM
Gas, liquid and solid.. bound into a slurry of mud or as crystalline particles in stones..

or as a parts of a atmosphere.. dirty dust..

You can see it matters as to what form this alleged water it to be found as... or if at all.

Yes. When talking about water and astrobiology, it is important to distinguish between water as a chemical compound (H2O), and liquid water.

The compound H2O is not at all rare in the universe. Why should it be? Hydrogen is the most common element, and oxygen is the third most common (by mass), and hydrogen and oxygen atoms combine readily to produce molecules of H2O. So, water, water everywhere...

But does that mean lots of water-based life, as on Earth? The problem is, all living cells on Earth contain liquid water in their cytoplasm. Even if they can survive in a dormant state without liquid water (e.g. as spores), they cannot metabolize without it. And liquid water only occurs in a limited range of temperatures and pressures...

For instance, the discovery of H2O molecules in the ultra-thin atmosphere of Mercury is certainly remarkable, because the worlds near the Sun are generally the least hydrogen-rich. But it doesn't necessarily make Mercury a plausible habitat for life.

In many parts of the solar system, the situation may be as described by Samuel Taylor Coleridge in his "Rime of the Ancient Mariner".

Water, water, everywhere
Nor any drop to drink.

Colin Robinson
2012-Feb-19, 12:10 AM
Does anyone know for certain whether or not hard spectrographic measurements, have ever confirmed the presence of water on Titan ? …
Surely, Cassini would have found some hard data in this respect ?

Spectrography is about interaction between matter and radiation. It is great for studying gases that are incandescent, or volumes of gas or clouds of particles through which light can shine. If Titan's atmosphere contained more than a trace of water vapor, or of water ice particles, then yes, Cassini would probably have found that. I am not so sure whether you would expect spectrography by Cassini to provide direct evidence of rock-like H2O on Titan's surface, or of liquid H2O a few kilometers down.

Selfsim
2012-Feb-19, 04:19 AM
Hi Extrasolar Flapjacks ! (Nice to chat with you) :)

We are capable of searching for and detecting more than life like ours. We would find life like ours most easily,

On Earth only. And it seems, only because it is based on water!

We know nothing about 'life' beyond Earth. I have no problems with the 'searching for' part of your statement. The more local searching, the better, as far as I'm concerned. The absoluteness of your 'detection' claim, in this case however, would seem to be based on predictive theory, not prior empirical results of exo-life.

How can we predict that we could detect exo-life, if we have no prior evidence of it, and with the legitimately evidence-based, even stronger statement that we can never predict it, coming from systems theory?
If we can, I'd like to know exactly the reason we say we can do that. Presence of liquid water or any other 'constants' or 'variables' ? I don't think so … why ? I'll explain ...

Most real non-linear systems (in nature) are also irreversible. We cannot extrapolate back to what we think was the original state, and then make predictions of what the 'likely' outcome might be in another isolated system, starting from those same approximations. Any initial fluctuations in the values of, or even in presence/absence of, the system 'constants' or 'variables', can fundamentally alter the outcomes and diverge the results, often radically so.
… We cannot constrain the possible outcomes. We thus, cannot draw any legitimate inference from the presence or absence of water. This is completely at odds with trying to associate habitable zones, with inferred exo-life. Note: I'm not saying this rules out any so-called 'possibilities'. But it raises an interesting issue from systems theory, about our Earth-centric, 'water-based' assumptions, and 'predictions' therefrom.

The systems nature creates, are not the systems humans create to explain them. In the case of the life systems we know about, there is a huge difference. We know nothing about 'exo-life' systems nor their implications, as far as the presence of liquid water, (or liquid organic solvents), is concerned.

I cannot see how that life on Earth requires liquid water, can be legitimately extrapolated to exo-life supporting environments. The systems processes are irreversible .. the fact that Earth based life requires water, is our particular constraint - nothing more. Extrapolation of this seems to have no legitimate systems theory foundations (?)


We would find life like ours most easily, but we're made of the same stuff that everything else in the universe is made of. We can find that stuff and put 2 and 2 together, A linear function analogy ..?.. not at all valid in many complex, non-linear biological, (or environmental), systems.

just like we have always done as humans when making discoveries. We weren't looking for microwaves before they were discovered either.I'm reminded of the mindset which resulted in James Cooks' voyages in pursuit of the Northwest Passage .. or of the Great South Land. 'Twas the act of exploration which resulted in the discovery of reality .. not the prediction coming from deterministic physical principles. As a matter of fact, Cook falsified all of those !

Regards

Colin Robinson
2012-Feb-19, 04:23 AM
At best, bulk moon density calculations result in a density of the moon of 1.88g/cm3, and on the basis of this figure alone, Titan's bulk composition is inferred as being half water ice, and half 'rocky material'.

Some surface reflectometry measurements (Huygens ?) were also taken, and also seemed to be 'consistent with' the 'possibility' that 'some' surface elements may be composed of frozen ammonia/water ice .. (but that also seems to be a 'maybe').
I haven't read the Tobie et al material yet, but I've read the Wiki page ... and it is not all that clear about this.

Judging from the Wiki article, theories about the composition of Titan (apart from its atmosphere) are indeed based largely on its density.

Density, at least, is in the category of hard fact. After all, density is mass divided by volume and both mass and volume can be determined with reasonable accuracy by careful observation from Earth using known laws of gravity. Plus, if the astronomers had been seriously wrong about Titan's mass and/or volume, could the Huygens probe have achieved a soft landing?

When you consider not only the known density, but also what is known about the composition of the solar system generally, and the outer solar system in particular, it is possible to make an estimate of the bulk composition of Titan which is not just a guess, even if it can't be confirmed directly by a method like spectroscopy.

For instance, it is known (from spectroscopy of the gas giants) that hydrogen is abundant in the outer solar system. And hydrogen-rich ices (eg NH3 and H2O) would account for the comparatively low density of outer moons such as Titan (low compared to rocky worlds like Earth and Mercury). On the basis of this data alone, is it not reasonable to think that hydrogen-rich ices are an important constituent?

Selfsim
2012-Feb-19, 05:12 AM
Judging from the Wiki article, theories about the composition of Titan (apart from its atmosphere) are indeed based largely on its density.

Density, at least, is in the category of hard fact. After all, density is mass divided by volume and both mass and volume can be determined with reasonable accuracy by careful observation from Earth using known laws of gravity. Plus, if the astronomers had been seriously wrong about Titan's mass and/or volume, could the Huygens probe have achieved a soft landing?

When you consider not only the known density, but also what is known about the composition of the solar system generally, and the outer solar system in particular, it is possible to make an estimate of the bulk composition of Titan which is not just a guess, even if it can't be confirmed directly by a method like spectroscopy.

For instance, it is known (from spectroscopy of the gas giants) that hydrogen is abundant in the outer solar system. And hydrogen-rich ices (eg NH3 and H2O) would account for the comparatively low density of outer moons such as Titan (low compared to rocky worlds like Earth and Mercury). On the basis of this data alone, is it not reasonable to think that hydrogen-rich ices are an important constituent?
Hi Colin;
Yep. My original question was no so much to query the bulk compositional estimates.
It was more coming from just not knowing whether or not, direct spectrographic measurements have ever been taken, in order to actually confirm its surface, (or detailed atmospheric), composition. So far, no-one here has answered this question.

I was watching Fraser's interview with Mike Brown (ie: of 'The man who killed Pluto .. and why it had it coming' fame). He rattled off details of just about all the recently discovered dwarfs and outer moons. From memory, he mentioned that Eris (? I think), surprised them all because its density was greater than Pluto's .. and yet, it orbit was further out (?) .. (I'm going by memory here .. so I may be mistaken .. I'll have to check out that interview again .. it was terrific, by the way …)

He also had a bit to say about Europa .. he discussed the sub-surface 'liquid ocean' thingy as well.

One of his 'take-aways', was the buzz he gets when they find out how far off they are in their estimates. :)

He also mentioned the new 'star eclipse method' of spectral moon/outer planet atmospheric gas analysis .. precision stuff, eh ? Apparently Pluto is still just beyond the resolving distance of the big ground and space-based scopes .. (hence the need for New Horizons). He said they gave up trying to compete with Cassini ..

Regards
PS: He also mentioned the importance of detecting orbiting moons around the outer objects for the purposes of calculating densities etc.

Selfsim
2012-Feb-19, 07:11 AM
Yes. When talking about water and astrobiology, ...
...[snip]...
When talking about water and astrobiology, it is important to distinguish between water as a chemical compound (H2O), and liquid water.
...[snip]...
For instance, the discovery of H2O molecules in the ultra-thin atmosphere of Mercury is certainly remarkable, because the worlds near the Sun are generally the least hydrogen-rich. But it doesn't necessarily make Mercury a plausible habitat for life.
Would the presence of liquid water, necessarily make any natural environment outside of Earth, a 'plausible' habitat for evolved exo-life ?

If so, what is the empirical, or theoretical basis for this 'plausibility' ?

The problem is, all living cells on Earth contain liquid water in their cytoplasm. Even if they can survive in a dormant state without liquid water (e.g. as spores), they cannot metabolize without it. And liquid water only occurs in a limited range of temperatures and pressures...
Why do generalised metabolic processes, necessarily require liquid water ?
Anabolism defines pathways that construct molecules from smaller units. These reactions require energy (ie: they're endothermic). Catabolism defines pathways that break down molecules into smaller units and release energy (ie: they're exothermic).
There are lots of exothermic and endothermic processes in nature not involving water.

Regards

Colin Robinson
2012-Feb-19, 08:39 AM
Hi Colin;
Yep. My original question was no so much to query the bulk compositional estimates.
It was more coming from just not knowing whether or not, direct spectrographic measurements have ever been taken, in order to actually confirm its surface, (or detailed atmospheric), composition. So far, no-one here has answered this question.

Regarding detailed atmospheric composition, the Cassini-Huygens mission has made measurements with several different devices. The measurements answered many questions and raised many new ones.

E.g. as Hugyens descended thru Titan's atmosphere, it took measurements with a GCMS (gas chromatograph mass spectrometer), getting information about atmospheric composition at different levels.

During fly-bys, Cassini used its plasma spectrometer (CAPS), and discovered negatively charged molecules with mass/charge ratio of 10,000 amu/q, which means they are at least 10,000 times the mass of a hydrogen atom.

http://en.wikipedia.org/wiki/Atmosphere_of_Titan
http://adsabs.harvard.edu/abs/2007GeoRL..3422103C

That's a large molecule...

Not much is known yet about the character of these molecules, however, except that they are described as "tholins". As "tholin" is the generic name for the sorts of compounds of carbon, hydrogen and nitrogen that can form in a Titan-like atmosphere, it would be strange if they were not "tholins".

Regarding surface composition... both Cassini and Huygens have taken photographs of various surface features (apart from the hydrocarbon lakes) including dunes and pebbles. But I don't think the composition of these features has been ascertained directly.

As Wiki says: "Titan is known to have extensive fields of dunes, though the origin of the material forming the dunes is not known - it could be small fragments of water ice eroded by flowing methane, or possibly particulate organic matter that formed in Titan's atmosphere and rained down on the surface."

http://en.wikipedia.org/wiki/Regolith#Titan

Why (you may ask) isn't more precise information about composition of the surface available from Cassini or from Huygens?

Well, Huygens was basically designed to descend through the atmosphere, making measurements and taking pictures. It was not designed to do experiments on the surface. This was because the mission planners didn't know enough about the surface of Titan to have any confidence that Huygens would survive the landing.

As for Cassini, it is one thing to use spectrometers etc from orbit to investigate the chemistry of an atmosphere, but the composition of a surface... The point is, more sorts of radiation can pass thru an atmosphere than through solid ground, so in the case of the atmosphere there is a lot more for an orbiter to measure.

Selfsim
2012-Feb-19, 10:00 AM
Well, this is about the best I've come up with so far ... Data from the Huygens Landing Site. (http://planetary.org/explore/topics/saturn/titan_huygens.html)

So, about three quarters of the way down, there is a graph called "Spectrum of Titan's Surface", which is a reflectance spectrum, taken by the Huygens probe. The caption says:

The visible part of the spectrum is dark and brownish, and there are absorption features in the infrared part of the spectrum that match water ice. However, the slope of the spectrum in the infrared wavelengths matches no existing laboratory measurements. The black lines show laboratory spectra of two "tholins.

.. I am presently trying to work out exactly what this means .. ie: Is there water ice there, or not?

A little further down, there is a mass spectrum of the atmosphere ... no signs of water in that (as expected).

Here's (http://www.planetary.org/blog/article/00003326/) a discussion about evaporites discovered on Titan's surface. It says:

A third planetary instance of evaporite has now been discovered in an exotic location: Saturn's moon Titan. Being so far from the Sun, Titan has a low surface temperature of 90°K (-183°C), just warmer than liquid nitrogen. Hence all of Titan's water is permanently frozen. However, methane on Titan plays the same role that water does on Earth and Mars. Titan has methane clouds, methane rain, methane rivers, and methane lakes and seas.

Therefore, the evaporites on Titan have an unusual nature compared to those on rocky planets. Instead of water being the solvent, on Titan the solvent is methane. And instead of salts being the solute, on Titan organic molecules derived from ultraviolet photolysis of methane dissolve in rain, surface, and ground liquid. Those organics precipitate out of lakes when the liquid methane solute evaporates, becoming evaporite."

So, is it possible that those 'rounded rocks' at the Huygens site, (which are just about everywhere cursorily referred to as 'water-rounded rocks'), might actually be evaporite remnants, weathered by methane rain ? After all, Huygens landed on a lake shore didn't it ?

Regards

Colin Robinson
2012-Feb-19, 10:57 AM
Would the presence of liquid water, necessarily make any natural environment outside of Earth, a 'plausible' habitat for evolved exo-life ?

I am not sure what you mean by "evolved exo-life". Mainstream biology, as I understand it, takes the view that all life evolves. Indeed I have seen life defined as "a chemical system capable of Darwinian evolution".

Would any place with liquid water be a plausible habitat for something to evolve in? Well, not necessarily. It is hard to see how a chemical system capable of Darwinian evolution could be made out of hydrogen and oxygen alone... Plus life requires a source of energy...


If so, what is the empirical, or theoretical basis for this 'plausibility'?

The theoretical issues are discussed in some detail in a book-length report called The Limits of Organic Life in Planetary Systems, prepared by a committee of the US National Research Council that was chaired by John A. Baross of the University of Washington. You can read it online (without charge) at...

http://www.nap.edu/catalog.php?record_id=11919


Why do generalised metabolic processes, necessarily require liquid water ?

In the words of Baross and his committee: "A liquid phase facilitates chemical reactions, something that has been known empirically for centuries."

Does the liquid have to be water? Not necessarily. The report discusses a range of other liquids (and supercritical fluids) that might serve as solvents for life on other worlds, in the same that liquid water serves as a solvent for life on Earth.

They also briefly mention the possibility of extraterrestrial life based on chemical reactions that did not take place within a liquid medium, but within a gas or a solid.

It is difficult to rule anything out in this field...

But you yourself, Selfsim, have raised doubts about whether we humans would be able to identify life in a form different to our own.

If that would be a challenge in the case of life-forms based on a different liquid solvent (such as life on Titan with a liquid methane/ethane solvent), would it not be an even greater challenge in the case of life forms based on a solid-phase chemistry or a gas-phase chemistry?

Extrasolar
2012-Feb-19, 05:26 PM
Hi Extrasolar Flapjacks ! (Nice to chat with you) :)


On Earth only. And it seems, only because it is based on water!

We know nothing about 'life' beyond Earth. I have no problems with the 'searching for' part of your statement. The more local searching, the better, as far as I'm concerned. The absoluteness of your 'detection' claim, in this case however, would seem to be based on predictive theory, not prior empirical results of exo-life.



We will find a subset of worlds similar in composition to ours in terms of ratio of elements and compounds. That would be where we start looking. I wouldn't call the claim I made an absolute, and yes it is based on the only data available (Earth). I don't believe prediction to be part of my statement though. The only time I would throw that out there is if we have looked at a set of planets and can say that x number of planets match conditions of Earth. Not just Earth as it is now, but Earth as it has been in the past as far back as we can gather data for in terms of atmospheric composition. And if a natural process could be responsible for what is being detected, then it wouldn't be included in the subset.



How can we predict that we could detect exo-life, if we have no prior evidence of it, and with the legitimately evidence-based, even stronger statement that we can never predict it, coming from systems theory?
If we can, I'd like to know exactly the reason we say we can do that. Presence of liquid water or any other 'constants' or 'variables' ? I don't think so … why ? I'll explain ...

Most real non-linear systems (in nature) are also irreversible. We cannot extrapolate back to what we think was the original state, and then make predictions of what the 'likely' outcome might be in another isolated system, starting from those same approximations. Any initial fluctuations in the values of, or even in presence/absence of, the system 'constants' or 'variables', can fundamentally alter the outcomes and diverge the results, often radically so.
… We cannot constrain the possible outcomes. We thus, cannot draw any legitimate inference from the presence or absence of water. This is completely at odds with trying to associate habitable zones, with inferred exo-life. Note: I'm not saying this rules out any so-called 'possibilities'. But it raises an interesting issue from systems theory, about our Earth-centric, 'water-based' assumptions, and 'predictions' therefrom.


I couldn't agree more, and the very idea that our own system and every system is based on such radical dynamics that depend on such long timescales is one of the most fascinating things to think about. It raises the possibility in the mind that life really could be so abundant and undetectable at the same time. We can't predict those until we have accurate computer models that perfectly predict our own system and other systems that are close by. I don't even know if there are basic simulation programs that model chemistry right now, let alone one that models an entire galaxy. So, all we can do is look for similar worlds and search for data that would not occur in our system by natural means alone. SETI only explores one area of life signal detection, but what have we done in terms of spectroscopic surveys, and what are we actually capable of doing in terms of spectroscopic surveys?



The systems nature creates, are not the systems humans create to explain them. In the case of the life systems we know about, there is a huge difference. We know nothing about 'exo-life' systems nor their implications, as far as the presence of liquid water, (or liquid organic solvents), is concerned.

I cannot see how that life on Earth requires liquid water, can be legitimately extrapolated to exo-life supporting environments. The systems processes are irreversible .. the fact that Earth based life requires water, is our particular constraint - nothing more. Extrapolation of this seems to have no legitimate systems theory foundations (?)

A linear function analogy ..?.. not at all valid in many complex, non-linear biological, (or environmental), systems.


I wasn't trying to imply anything linear when I wrote that. I was only suggesting that realistically, we have to initially narrow the search to a subset of planets. We can only look for what we know. Even then, of course we don't know what the possibility of life taking on a completely different and undetectable form of life is. Maybe out of that subset, 3*(x)% of planets will have life but we only find (x)% that will be within the constraints that we're looking for. I do concede that. However, from that x% subset, that's when we can start to say, this planet has lots of X compound in the atmosphere for some reason, and the only way that can be made is by a specific process. I am not a chemist, but don't such compounds exist?



I'm reminded of the mindset which resulted in James Cooks' voyages in pursuit of the Northwest Passage .. or of the Great South Land. 'Twas the act of exploration which resulted in the discovery of reality .. not the prediction coming from deterministic physical principles. As a matter of fact, Cook falsified all of those !

Regards


That makes the same point as the discovery of microwaves. It wasn't something that was predicted. It was stumbled upon as a result of other actions. Its observation was realized and explored. Of course, I'm almost sure predictions and hypothesis result from such discoveries. Thanks for the reply!

Colin Robinson
2012-Feb-19, 08:31 PM
.. I am presently trying to work out exactly what this means .. ie: Is there water ice there, or not?

Would direct evidence of water ice on the surface of Titan make you think it worth looking for life there? Or, if the sand grains and pebbles are made of carbon compounds instead of water, would that lead you to think there is no life on Titan?


So, is it possible that those 'rounded rocks' at the Huygens site, (which are just about everywhere cursorily referred to as 'water-rounded rocks'), might actually be evaporite remnants, weathered by methane rain ?

I agree they were very likely weathered by methane rain.

Actually I'm surprised by your statement that the rocks were called "water-rounded" just about everywhere. I don't doubt people have said, quite rightly, that they look like water-rounded rocks commonly found on Earth, and therefore imply recent presence of an eroding liquid, flowing about on the surface. However, the mainstream view has always been that the liquid in question would have been methane or ethane.


After all, Huygens landed on a lake shore didn't it ?

Actually no, it didn't. At least not on the shore of a present-day lake.

There are lakes on Titan that have liquid right now, and some of them the size of inland seas. But they were discovered by Cassini taking infrared photographs from its orbit, quite some time after the Huygens landing.

Selfsim
2012-Feb-19, 11:21 PM
Would direct evidence of water ice on the surface of Titan make you think it worth looking for life there? Or, if the sand grains and pebbles are made of carbon compounds instead of water, would that lead you to think there is no life on Titan?
Well Colin, thanks for your question much appreciated. :)
As far as I'm concerned, it doesn't really matter what I think .. :) … what I think has no bearing on what exists in the physical world .. (and you're welcome to call me on that, anytime). I don't have enough time to argue about opinions, beliefs or speculation .. there's too many other interesting things in science to learn. :)

In this instance, all I want to know is … is there any direct measured evidence of water on Titan ?

NASA has a planetary/astrobiology exploration policy of 'follow-the-water' and, as you point out, there are other schools of thought about where to look for 'life'. Beats me how we'd ever deliberately detect that 'life' if this 'policy' drives the various programs and detection technologies (??). Even if it doesn't, I still don't know how we'd detect it, other than by a pure fluke discovery. (No amount of hypothesising, theorising or conjecture will change the chance of a 'fluke' discovery. 'The fluke' seems to remain as our best bet).

NASA (& ESA) together, dominate dissemination of information relating to the findings of planetary exploration.

In this case, attempted NASA/ESA direct measurements of the surface composition of Titan (http://www.mps.mpg.de/homes/schroder/Publications/Schroder_Keller_2008.pdf) and, as far as water ice is concerned, returned the result: "inconclusive" (because of problems with the design of the experiment procedure). So the answer to my original question is: 'inconclusive', which I think John inferred in his previous post. Now it seems reasonably 'confirmed'.


Actually I'm surprised by your statement that the rocks were called "water-rounded" just about everywhere. I don't doubt people have said, quite rightly, that they look like water-rounded rocks commonly found on Earth, and therefore imply recent presence of an eroding liquid, flowing about on the surface. However, the mainstream view has always been that the liquid in question would have been methane or ethane.Yep. I think the reporting language is at cause in this one. Official releases usually become accepted as 'mainstream', in spite of the actual findings. Here are some more examples ...


After landing, Huygens photographed a dark plain covered in small rocks and pebbles, which are composed of water ice.[ (http://en.wikipedia.org/wiki/Titan_(moon)#cite_note-Seeing_Touching_Titan-ESA-117)118]So, the '118' reference, turns out to be an out-of-date ESA release. In that release, they say unequivocally…

Titan has frozen water ice instead of dirt,

Titan volcanoes spew very cold ice
… none of which, has any hard supporting direct evidence. Clearly, this is not 'mainstream'. Perhaps here at BAUT, it is now ATM (?) :)

Regards.

Colin Robinson
2012-Feb-19, 11:23 PM
Well, this is about the best I've come up with so far ... Data from the Huygens Landing Site. (http://planetary.org/explore/topics/saturn/titan_huygens.html)

So, about three quarters of the way down, there is a graph called "Spectrum of Titan's Surface", which is a reflectance spectrum, taken by the Huygens probe. The caption says:


The visible part of the spectrum is dark and brownish, and there are absorption features in the infrared part of the spectrum that match water ice. However, the slope of the spectrum in the infrared wavelengths matches no existing laboratory measurements. The black lines show laboratory spectra of two "tholins.


.. I am presently trying to work out exactly what this means .. ie: Is there water ice there, or not?

Here is another report (dated 2008) about Titan's surface composition:

http://www.lpi.usra.edu/meetings/scssi2008/pdf/9093.pdf

This one states (underlining added by me):


Recent analysis of data from the Cassini Visual and Infrared Mapping Spectrometer (VIMS) [1, 3] confirms the presence of “dirty” water ice deduced from earlier ground-based studies [4, 5]. However, many regions of Titan are not spectrally consistent with water ice as the dominant component, and the identity of the other constituents remains ambiguous.

What these passages are saying, if I understand it correctly, is that yes, there is water ice in the surface, but it is certainly not the only stuff there, and is not necessarily the main stuff. And the other constituents are more difficult to identify.

Colin Robinson
2012-Feb-20, 12:40 AM
In this instance, all I want to know is … is there any direct measured evidence of water on Titan ?

If you mean spectrographic evidence of water ice, the answer seems to be yes.

Which is different to what I wrote a few posts ago -- I knew that spectrography works well as a way of analysing gases and dust clouds, but I wasn't sure whether it can be used for solid surfaces.

Anyway here is another paper, long and quite technical, on what the Cassini instrument VIMS (Visual and Infrared Mapping Spectrometer) says about the surface of Titan...

http://barnesos.net/publications/papers/2008.02.Icarus.McCord.Search.for.Spectral.pdf

A quote from the abstract:

"Our search for spectral diversity using seven methane transmission windows in the near infrared suggests that spectrally distinct units exist on the surface of Titan and that most of the surface can be modeled using only a few distinct spectral units: water frost, CO2 frost, atmospheric scattering, and an unknown material bright at 2 μm. A dark, spectrally neutral material is also implied."

In simple English... As far as these scientists can tell, based on the spectrometric data, the surface of Titan has solid water, solid carbon dioxide, and other stuff as well.

Selfsim
2012-Feb-20, 12:44 AM
Yes Colin … many thanks for your time, and assistance, in helping to answer this one .. its much appreciated. :)

It seems there might have been a lot of hype around the 2008/2009 timeframe.

I'm going to go with the Schroder/Keller report, (http://www.mps.mpg.de/homes/schroder/Publications/Schroder_Keller_2008.pdf) as it was peer reviewed and published in 'Planetary and Space Science', (Volume 56, Issue 5, p. 753-769, 2009). It seems that Schroder has been fairly involved in the design and data interpretation of the Huygens project, as there are numerous papers by him on the Titan topic. (http://adsabs.harvard.edu/cgi-bin/nph-abs_connect) He's also published a recent follow up paper confirming their findings of 2009, in January this year. (http://adsabs.harvard.edu/abs/2012P%26SS...60..342K)

They also explain, (in the orginal 2009 paper), why the findings were inconclusive. The 1500nm peak, also looks similar to one of the lab tholin samples. The width of the peak is also a clue that it is probably not water. Lab peak widths for water ices are much sharper around 50nm, whereas the Titan spectrum shows about 150nm width. The 2000nm range would've been a better region to sample, but methane which absorbs in that region, would've prevented this.

According to Schroder/Keller:

The only unambiguous absorption feature is at 1500 nm, which may be associated with either tholins or water ice. We agree with Tomasko et al. (2005) that the evidence for water ice in DISR spectra is inconclusive. We find this line to be significantly deeper after landing, possibly indicating surface heterogeneity.
...
We confirm the blue slope in the near-IR, featureless apart from a single shallow absorption feature at 1500 nm. We agree with Tomasko et al. that the evidence for water ice is inconclusive. By modeling of absorption bands we find a methane mixing ratio of 4.5±0.5% just above the surface. There is no evidence for the presence of liquid methane, but the data do not rule out a wet soil at a depth of several centimeters.

Overall, the Huygens probe had many problems .. and perhaps this measurement may be another one to add to the list. A real pity. :(

Regards

Colin Robinson
2012-Feb-20, 02:02 AM
I'm going to go with the Schroder/Keller report, (http://www.mps.mpg.de/homes/schroder/Publications/Schroder_Keller_2008.pdf) as it was peer reviewed and published in 'Planetary and Space Science', (Volume 56, Issue 5, p. 753-769, 2009). It seems that Schroder has been fairly involved in the design and data interpretation of the Huygens project, as there are numerous papers by him on the Titan topic. (http://adsabs.harvard.edu/cgi-bin/nph-abs_connect) He's also published a recent follow up paperconfirming their findings of 2009, in January this year. (http://adsabs.harvard.edu/abs/2012P%26SS...60..342K)

I agree that the Schroder/Keller paper has to be taken seriously. However, the paper by Thomas McCord and others (http://barnesos.net/publications/papers/2008.02.Icarus.McCord.Search.for.Spectral.pdf) was also published in a peer-reviewed journal -- Icarus -- and McCord happens to be a NASA specialist in spectrometry.

So I'd suggest to you that McCord's paper ought to be taken as seriously as Schroder's.

Why then, does one paper say there is no sign of water ice on the surface, while the other says there is?

Well, one reason may be that Schroder's paper is specifically about "Titan's surface at the Huygen's landing site", as the title of the paper itself makes clear. The findings were based on data collected by the Hugyen's probe as it was about to land. Whereas McCord's paper is a general look at Titan's surface, and is based on data collected from orbit.

Titan, like Earth, has different terrains in different places: there are light regions and dark regions, highlands and lowlands, differences between what happens at different latitudes.

Apart from the question of solid water, Schroder notes that liquid methane was not detected. Is this an argument against the large methane/ethane lakes which Cassini has photographed in Titan's polar regions?

No, because Huygens landed nowhere near the poles.

Does Earth have solid granite at its surface? Does it have liquid H2O? It depends very much where you look.

Selfsim
2012-Feb-20, 05:01 AM
Ok, Colin. Read through the McCord paper. It's basically mostly concerned with creating a model which fits previous (Earth) ground based surveys, the initial interpretations of the Huygens ground based DISR spectra (2005/2006) which inferred 'probable' ground based water ice - (which was subsequently reinterpreted by the 2009 Schroder/Keller paper), the Cassini VIMS spectra of the Huygens site, and other previous analyses of this data.

The purpose of doing this, is to come up with an explanation which fits the facts. Ie: the 'usual' scientific process in action, leading towards developing a theory, in the light of the absence or paucity of available data.


Why then, does one paper say there is no sign of water ice on the surface, while the other says there is?
Do either papers make either of these claims ?
(I don't seem to be able to find such .. perhaps I missed them somehow ?).

What I see from McCord, is lots about synthesis of spectral effects resulting from introducing models of various ice particles into the methane transparent windows, in order to see whether or not this fits the various measurement datasets. The ices they are modelling, assume various mixtures of CO2 and H2O 'frosts' (of varying particle sizes), all of which have varying success, depending on which dataset one is examining (which is discussed quite thoroughly).

What I see from the Schroder et al paper is 'inconclusive' (as far as Huygens site H2O ice is concerned).

Glad I read the papers. I now have the modelling perspective, and the onsite measurement data perspective.

Regards

Colin Robinson
2012-Feb-20, 11:57 AM
Read through the McCord paper. It's basically mostly concerned with creating a model which fits previous (Earth) ground based surveys, the initial interpretations of the Huygens ground based DISR spectra (2005/2006) which inferred 'probable' ground based water ice - (which was subsequently reinterpreted by the 2009 Schroder/Keller paper), the Cassini VIMS spectra of the Huygens site...

That's funny. I had the impression that the data from the Cassini instrument VIMS came from a much larger area of Titan's surface than the Huygens site looked at by the DISR instrument...

Selfsim
2012-Feb-20, 08:35 PM
That's funny. I had the impression that the data from the Cassini instrument VIMS came from a much larger area of Titan's surface than the Huygens site looked at by the DISR instrument...I'm sure it does. It explains that the reason for designing the DISR instrument, and mounting it on Huygens in the first place, was because of the known difficulty in getting a ground-indicative spectrum from 'orbiting' Cassini. Titan's dense atmospheric methane's proximity to water in the absorption spectrum, also causes noise in the nearby water peaks. The VIMS instrument can only look through several methane windows to pick up the ground reflected spectrum. They seem to be averaging the results so obtained, in order to piece together a comprehensive spectrum of what the ground looks like from a Cassini fly-by.

There are a lot of secondary 'problems' in the VIMs spectra, (particle scattering, etc), mainly caused, again, by the complexity of Titan's atmosphere. This means that the VIMS data has to be 'cleaned up' by using various nifty data processing techniques, in order to separate atmospheric effects from the ground-based readings. I'm not sure of what physical area the VIMS spectrum covers, but there is also variance with the surface features, which then complicates the interpretation even further.

The DISR spectrum would have eliminated a lot of that complexity, at the expense of providing a more constrained sample (as you say).

It seeems the very complexity of Titan you mention, (which also seems to act as the reason for hope of possible life), might actually be preventing us from seeing it in the complex spectra obtained, unfortunately. :(

I'm reading through the NRC's 'Limits of Organic Life' thesis, also. I understand the perspective, but I also see a somewhat necessarily constrained, myopic focus on the whole subject. (Perhaps discussion material for another thread ?)

Regards

Xibalba
2012-Feb-26, 01:50 AM
If panspermia is right, then life on another planet in our solar system might resemble our own, though they've been digressing for 3,5 billion years. If they're still there, or ever were, they may not resemble Earth life at all.

If panspermia ain't correct, the possibility that other bodies in our solar system harbours life is slimmer still. But then anything could pop up if "life", or more precisely self-replicating organisms, decided to take another planet as home. It could be quite different.

Selfsim
2012-Feb-26, 05:35 AM
If panspermia is right, then life on another planet in our solar system might resemble our own, though they've been digressing for 3,5 billion years.(I think you may mean 'diverging' for 3.5 billion years (?) ).

But even if this might be possible, what makes you say/think there's some kind of (divergent, or even convergent) trajectory at all, over the same 3.5 billion year period ?

Why would anyone think that of the myriad of possible outcomes, a chance 'seeding' of another proto-planet in our Solar System, would now bear any resemblance to the outcomes here on Earth ? So you're suggesting that someone has some basis for speculating that of the myriad of possible environmental combinations, somehow, two roughly similar environments occurred, which fitted the common progenitor's sensitivity constraints, in order for the same 'progression' to occur across both instances ? But even if they did have some basis for speculation, the complexity exhibited in our own modern-day life, demonstrates that chaos has played a big role. So, as this occurs, then somewhere along the two progression paths, there has been extreme sensitivity to conditions, resulting in completely unpredictable outcomes, across the two permutations. Where does that leave the speculative basis for assuming resemblance across two previously 'seeded' worlds (permutations) ?

Then the same coincidence happens as far as the myriad of mutations possible, and the corresponding adaptations further down the track? How do these astronomical-proportion-permutations, measure up against the limited numbers of determinable chemical reactions resulting in progression towards life-viable organic compounds and cell structures ? (Completely swamps it, I would think). And, what if at some point during the 'evolution' of such an exo-protolife element, a key mutation necessary for resulting in similarity to the Earth-life, doesn't happen, (in the non-Earth based proto-life) ? How does this compare, in frequency, with ultimately successful 'similarity' adaptations across both environments ?

Come to think of it, why assume only two outcomes .. ie: (i) two comparable life outcomes (bearing similar resemblances); (ii) two comparable life outcomes (bearing no similar resemblances) ?
What happened to the third possible permutation .. ie: (iii) one viable life outcome, (Earth's), and one non-viable life outcome, (ie: in the other panspermia's 'drop-off zone') ?



If they're still there, or ever were, they may not resemble Earth life at all.… or may never have been viable prospects at all ! (Ie: outcome (iii) above). How big is the non-viable prospects list of permutations, compared with the viable prospects list ? Why do we spend so much effort focusing on what could quite easily be, a miniscule set of possible outcomes ? How could we conclude panspermia "ain't correct" just because we don't find any other recognisable life forms ?


If panspermia ain't correct, How would we ever conclude that .. even if life wasn't discovered locally ? Did we miss it ? Did we look in the wrong places ? What are the 'wrong' places ? How do we know what the 'right' places are, (or were, in the past) ? Can we say anything about the 'possibility' (or otherwise) of panspermia? Sure we can .. ie: 'no change' in the status of panspermia's 'possibility'.
Conversely, coming from the principle of chaotically unpredictable life emergence, why even think that a local chance life discovery, which may happen to result in life recognisable by us, would be related to us, to the point that we could even think we could eliminate the possibility of a second natural emergence of identical life ? If we can, then what is the basis of this 'belief' (a big hint there).

the possibility that other bodies in our solar system harbours life is slimmer still. Why ? Where is the relationship between the non identification of evidence of panspermia, and the possibility of life being 'slimmer' elsewhere (locally) ?

But then anything could pop up if "life", or more precisely self-replicating organisms, decided to take another planet as home. It could be quite different.Different all right .. like maybe instantly terminated proto-life .. resulting in a dead planet, in spite of its co-incident (in time) seeding !
(Amongst many, many other finer variations, of myriads of other permutations).

We know absolutely zip about exo-life, panspermia, or their respective 'possibilities' ! We should face up to the reality of this.

We know way more about the unpredictability of it all !
Nothing we conjure up as 'possibilities', alters any of this reality.

Regards

Xibalba
2012-Feb-26, 11:03 AM
I agree that we know nothing, I'm only speculating.

KABOOM
2012-Feb-26, 12:00 PM
Even if panspermia within the solar system did occur, it may be unrecognizable to bacteria life on Earth.

Life on Earth is DNA-based, previously RNA-based and previously a simpler, but unknown, replicator-based form. To the extent that the "seeds" took the latter form when they arrived on Earth and still exist in such form or evolved into non RNA-based life, there may be no way to tell if there is a relationship at all.

Also, many feel that while bacterial-like life may be plentiful, the events that arose in which multi-cellular life evolved from bacterial life are much rarer. So life may be abundant, but "complex" life (multi-cellular) not.

Selfsim
2012-Feb-26, 11:27 PM
At the risk of seeming to be some kind of crank pushing a particular biased point of view, my only point in all of this discussion, is to highlight how speculation about exo-life seems to consistently rely on an innate Astrophysical penchant for connecting-the-dots, and extrapolating therefrom. In biology this simply doesn't work consistently enough to be credible. Modern day organisms are the products of eons of complex evolution, (which in itself, has been cited as a chaotic, non-linear process, with feedback1).

The Astro community has traditionally had great success in predicting outcomes on the basis of simple systems behaving deterministically. With the exception of the quantum physical domain, all of our classical models depend on the base assumption of deterministic outcomes and yet, the simplest test of this assumption, when applied to biology, demonstrates the inadequacies of applying such models, to explain the majority of biological systems and processes. The seemingly default, broad-brushed application of such classical physical principles, in order to make predictions about exo-life, is thus highly questionable.


Also, many feel that while bacterial-like life may be plentiful, the events that arose in which multi-cellular life evolved from bacterial life are much rarer. So life may be abundant, but "complex" life (multi-cellular) not.It should be noted that there is no concensus (http://en.wikipedia.org/wiki/Prokaryotic#Evolution_of_prokaryotes) amongst biologists, that multi-cellular eukaryotic life evolved from prokaryotic life (bacteria).

The generalised speculative conclusion about the 'abundance' thereof, (which seems to be, presumably, another linearly based extrapolation from the modern-day relative 'abundance' in Earth's case), thus has no scientific consensus basis, and is thus, a biased representation of how multi-cellular life might evolve.

Regards
1. Joseph Ford (http://132.187.98.10:8080/encyclopedia/en/fordJoseph.pdf) - one of the eminent physicists who defined mainstream Chaos Theory in the 70s.

Paul Wally
2012-Feb-27, 01:21 AM
At the risk of seeming to be some kind of crank pushing a particular biased point of view, my only point in all of this discussion, is to highlight how speculation about exo-life seems to consistently rely on an innate Astrophysical penchant for connecting-the-dots, and extrapolating therefrom. In biology this simply doesn't work consistently enough to be credible. Modern day organisms are the products of eons of complex evolution, (which in itself, has been cited as a chaotic, non-linear process, with feedback1).

The Astro community has traditionally had great success in predicting outcomes on the basis of simple systems behaving deterministically. With the exception of the quantum physical domain, all of our classical models depend on the base assumption of deterministic outcomes and yet, the simplest test of this assumption, when applied to biology, demonstrates the inadequacies of applying such models, to explain the majority of biological systems and processes. The seemingly default, broad-brushed application of such classical physical principles, in order to make predictions about exo-life, is thus highly questionable.



When searching for life, the methodology is to formulate a hypothesis and then to see whether it is true. It could even mean taking an intuitive guess and then check whether it is so. If it turns out to be wrong then we try something else. Based on the only example that we have, water seems to be important, so we try looking for liquid water elsewhere to check whether there is life there too. This doesn't mean that scientists believe liquid water is necessary or that they predict that it is necessary. No, they're checking whether it is necessary. Nobody is believing, predicting or assuming anything.

Then the nonlinear modelling: You get deterministic chaos, but what makes chaos unpredictable is sensitivity to initial conditions. As far as living self-organizing systems are concerned; they're not chaotic but somewhere in between simple and chaotic. Living systems are organized not chaotic and there are recurring patterns. Look for instance at a particular class of cellular automata (class 4 I think); these systems are temporally unpredictable, yet no matter what the initial conditions, the same kinds of patterns emerge. It may very well be that all life in universe have certain structural similarities, even though they emerge from different particular conditions.

Selfsim
2012-Feb-27, 03:03 AM
Hi Paul ! Good to have you involved in this discussion .. :)


When searching for life, the methodology is to formulate a hypothesis and then to see whether it is true. It could even mean taking an intuitive guess and then check whether it is so. If it turns out to be wrong then we try something else. Based on the only example that we have, water seems to be important, so we try looking for liquid water elsewhere to check whether there is life there too. This doesn't mean that scientists believe liquid water is necessary or that they predict that it is necessary. No, they're checking whether it is necessary. Nobody is believing, predicting or assuming anything.
Yep .. acknowledged, and good point. Its tricky to pin down exactly who we're talking about here, and I apologise if I over-generalised .. ('twas mostly on the basis of speculative statements I have observed) . It seems that as Biologists come together with Astrophysicist types, there is much to be learned from each discipline.

The voluminous superficial mainstream media messages we get however, sway many to jump towards developing a 'consensus reality' picture, which frequently ignores many aspects which serve to bring balance into the overall scientific perspective. (As well as complicating it). Speculation then seems somewhat constrained towards the familiar, resulting in heavily deterministic speculation where it may, or may not be, warranted.


Then the nonlinear modelling: You get deterministic chaos, but what makes chaos unpredictable is sensitivity to initial conditions. As far as living self-organizing systems are concerned; they're not chaotic but somewhere in between simple and chaotic. Living systems are organized not chaotic and there are recurring patterns. Look for instance at a particular class of cellular automata (class 4 I think); these systems are temporally unpredictable, yet no matter what the initial conditions, the same kinds of patterns emerge. Some pre-established living systems ... sure … and this would be a balanced conversation.
The same statement would seem to be more difficult to apply to areas such as evolutionary adaptation, biological/environmental sensitivity, or protein synthesis/transcription, (as examples). There are many other examples of biological systems which are closer to a self-organised critical state (eg: the brain). The periods over which some of these systems are predictable, are not known. The origins of these systems may well have been purely chaotic, due to their sensitivity to the initial environments from which they emerged (which are likely to have been chaotic, also).


It may very well be that all life in universe have certain structural similarities, even though they emerge from different particular conditions.Sure .. and for every speculative statement like this one .. there's another one with slightly different, or more radical perspectives. These should be included in a balanced discussion, don't you think ?

Regards