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TooMany
2012-Dec-06, 12:33 AM
http://nai.nasa.gov/news_stories/news_print.cfm?ID=137

This is an old article, but still interesting. I just started looking into this much smaller-than-bacteria life idea, so I don't know where it stands now. However, I do find skeptical attitudes among biologist amusing who claim that life cannot be smaller than 100 nm or so because not enough ribosomes would fit. It would seem that these same biologist then believe that life emerged as something as complex as a bacterium with no smaller forebear. Sometimes skepticism can get pathological.

This article is from 2001 with the claim by some that nanobes actually exist and grow on earth. If they are correct, shouldn't we know for sure by now?

Selfsim
2012-Dec-06, 01:19 AM
I agree with Knoll ...

"The size argument is a red herring if we don't know the relevant biochemistry," says Knoll. "The problem is that the structures in question are not diagnostically biological."

They are just that .. 'structures' …

There is no evidence that nanobes are autonomous organisms and not some fragments of some larger organism, either.

They apparently fail to respond to DNA amplification techniques, (http://en.wikipedia.org/wiki/Nanobes#Responses) they lack phosphorous in X-Ray spectrographic analysis.


… which demonstrates that nanobes do not have any DNA or RNA and may have a completely different mechanism for heredity, which accounts for many of their unusual chemical and physical properties and renders the size argument irrelevant.

Strange
2012-Dec-06, 01:24 AM
However, I do find skeptical attitudes among biologist amusing who claim that life cannot be smaller than 100 nm or so because not enough ribosomes would fit.

That seems a little unfair. It says that 200nm is the limit for "life as we know it". Which makes sense, if there were living organisms smaller than that, they would not be "as we know it". You would probably start to run into the tricky problem of defining life versus protobionts versus prebiotic chemistry.


It would seem that these same biologist then believe that life emerged as something as complex as a bacterium with no smaller forebear.

I'm not sure that follows. And, in fact, the editor of the report says, "Simpler forms of life are conceivable and probably existed early in the history of life."

I am not aware of any more recent work in this area (which doesn't necessarily mean much; it's not my area).

TooMany
2012-Dec-06, 06:05 PM
That seems a little unfair. It says that 200nm is the limit for "life as we know it". Which makes sense, if there were living organisms smaller than that, they would not be "as we know it". You would probably start to run into the tricky problem of defining life versus protobionts versus prebiotic chemistry.



I'm not sure that follows. And, in fact, the editor of the report says, "Simpler forms of life are conceivable and probably existed early in the history of life."

I am not aware of any more recent work in this area (which doesn't necessarily mean much; it's not my area).

Various people were quoted in the article and the editor made some comments too. Maybe I am being unfair since one skeptic said:

"If current nanobes can be shown to be living entities, then Earth harbors life forms whose chemistry we do not understand," says Knoll. "That would be interesting."

Well I personally would not be one bit surprised if Earth does harbor life forms whose chemistry we do not understand. It took some convincing for scientist just 150 years ago to accept germ theory. What nonsense, tiny little animals everywhere!

There must have been precursors to bacteria that were far simpler. Bacteria have evolved for 4 billion years, just like us. Their metabolic structures, management of genetic information, cell walls, sensory capabilities and so on are highly developed. The interesting question is are there actually simpler life forms alive now that we have missed?

The nano structures that some have claimed are fossils are very interesting. Here are some photos (https://www.google.com/search?q=Nanobes&hl=en&tbo=u&rlz=1C1CHKD_enUS418&tbm=isch&source=univ&sa=X&ei=uNnAUPXcJeGWjALk44Ag&ved=0CD4QsAQ&biw=1448&bih=852).

Even supposing that they do not indicate life, they undeniably demonstrate the spontaneous formation of structures that are self-similar but very much unlike crystals. In other words they demonstration a remarkable self-assemble power in nature even if they are not remnants of biological life.

TooMany
2012-Dec-06, 06:52 PM
I agree with Knoll ...


They are just that .. 'structures' …

There is no evidence that nanobes are autonomous organisms and not some fragments of some larger organism, either.

They apparently fail to respond to DNA amplification techniques, (http://en.wikipedia.org/wiki/Nanobes#Responses) they lack phosphorous in X-Ray spectrographic analysis.

Apparently this reference is to fossilized nanobes. The complete quote from the wiki article is:


One of the original authors of the paper in "American Mineralogist", Dr. Tony Taylor argues that the conspicuous lack of phosphorus in the X-ray spectroscopy data and the failure to find DNA using various DNA amplification techniques demonstrates that nanobes do not have any DNA or RNA and may have a completely different mechanism for heredity, which accounts for many of their unusual chemical and physical properties and renders the size argument irrelevant.

There are several problems with using your selection from this quote to debunk the possibility of life forms. One is that there is no citation to put this quote in context. Do we expect that fossil microbes still have the phosphorus in them? Do we expect to find DNA or RNA that can be amplified in a mineralized fossil of a microscopic life form? If this were the case, perhaps we have already done gene sequencing on 3.5 billion year old fossil stromatolites? Finally, we do not yet know whether DNA is something fundamental to life or whether it emerged from life forms that began without DNA.

In the same sentence from which you extracted you debunking, the author suggests that the nanobes may have a completely different mechanism for heredity.

TooMany
2012-Dec-06, 08:07 PM
I found this much more recent article about "nanobateria" (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2242841/) that concludes:


Here, we demonstrated these particles are self-propagated mineral protein complex containing fetuin as the major biological component which we propose to call nanons.

They are referring to what had been called nanobacteria recovered from animals. Fetuin is a blood protein secreted by the liver. These "nanons" as they call them do not contain DNA. I don't know how this relates to claims of nanobes that are not directly associated with animals (such as those found in some meteorites or mineral deposites).

What is life? In reality bacteria are highly-evolved life forms of great complexity. They are capable of feeding on their surroundings, sensing their chemical environment, growing and reproducing themselves through complex machinery programmed through DNA code. There must be some ladder that is climbed to reach such complexity and there may be many processes involved that some would argue are "not life". If we restrict our notion of "life" to include only these highly evolved forms, then perhaps we need other words for self-propagating forms that may have led to them, perhaps "proto-life".

Between non-life and life there are likely many shades of gray.

Strange
2012-Dec-06, 08:22 PM
Between non-life and life there are likely many shades of gray.

Indeed. Viruses and prions are two we know about. There may well be more.

Selfsim
2012-Dec-06, 08:57 PM
TooMany;
I'm actually with you, (at least in principle), on this thread.

A couple of (arduous) threads ago, Paul Wally (I think?) and myself, had disagreements about whether definitions, (underpinning speculations), required some basis in empirical evidence, or not. My view is that they must, otherwise any speculation which follows, is likely to have very little grounding in physical reality. His was, (I hope I got this right..?), that they can be defined in advance of any new discovery, courtesy of logic, (inference, deduction, abduction) and generalisations from the laws of physical science. I maintain that this technique is known to result in error, so little/no reliance in general should be placed on it. It is a metaphysical technique.

My position is also that our definition of 'exo-life' (for eg) will only have meaning when (and if) some exo-lifeform is discovered by the act of exploration. At that time, the definitions which are all presently based on known Earth-life, will be re-written. Until that discovery is made, all we have is based on what we already know. Biological definitions are based on empirical evidence sourced from carefully tested samples in controlled environments. Biological predictions are usually expressed using probablistic terminlogy. Astrophysical predictions on the other hand, are much firmer, and don't usually require such uncertain terms. We cannot rely solely on Astrophysical techniques alone, in defining exo-life. We need to get away from that type of thinking when it comes to this topic. Constrained predictions of exo-life, for instance, are not feasible.

The definitions of life have been broadened with every new 'unexpected' discovery such as: viruses, crystal phenomena (which meet the broad criteria for being categorised as 'life'), etc, etc.

Your present tack on this thread seems destined to end up in a word-definition quandry. My question for you is: How are you planning on avoiding that?

TooMany
2012-Dec-07, 02:49 AM
Your present tack on this thread seems destined to end up in a word-definition quandry. My question for you is: How are you planning on avoiding that?

I don't know nor really care about words. If people want to sit around arguing about what's life and what's not life, they are missing the point. Earth was just a rock with water and other stuff on it. Now look what we've got. I don't believe we need to postulate that some miracle occurred and suddenly we had single cell animals. We have to open our minds about how life may have developed. To say "life" is only the current end product, is just to make the word "life" useless for taking about abiogenesis. So loudly condemning these nanobes as "not life", is to completely miss the point of what they may be telling us.

Selfsim
2012-Dec-07, 04:12 AM
… So loudly condemning these nanobes as "not life", is to completely miss the point of what they may be telling us.
From the Raout/Drancourt linked document …

In order to gain better insights on this calciferous agent, we performed a large-scale project, including the analysis of “nanobacteria” susceptibility to physical and chemical compounds as well as the comprehensive nucleotide, biochemical, proteomic, and antigenic analysis of these particles. Our results definitively ruled out the existence of “nanobacteria” as living organisms and pointed out the paradoxical role of fetuin (an anti-mineralization protein) in the formation of these self-propagating mineral complexes which we propose to call “nanons.” The presence of fetuin within renal calculi was also evidenced, suggesting its role as a hydroxyapatite nucleating factor.
… and then in the 'Author Summary' section:

The comprehensive characterization of nanobacteria was the focus of our study. Our results definitively ruled out the existence of nanobacteria as living entities and revealed that they correspond to self-propagating mineral-fetuin complexes that we called “nanons.”
OK .. so you think that the 15 co-authors listed in this study, may have 'completely missed the point' of what these things might be trying to tell us?

What might they be trying to tell us?

Strange
2012-Dec-07, 10:02 AM
We have to open our minds about how life may have developed.

There are a great number of people studying many (maybe hundreds) of different ways in which abiogenesis may have happened. These range from the plausible to the far out (<cough>panspermia<cough>). I'm not sure how much more open minded the researchers could be.

Paul Wally
2012-Dec-07, 02:04 PM
What is life? In reality bacteria are highly-evolved life forms of great complexity. They are capable of feeding on their surroundings, sensing their chemical environment, growing and reproducing themselves through complex machinery programmed through DNA code. There must be some ladder that is climbed to reach such complexity and there may be many processes involved that some would argue are "not life". If we restrict our notion of "life" to include only these highly evolved forms, then perhaps we need other words for self-propagating forms that may have led to them, perhaps "proto-life".


My argument is that we can't study nature to find out what a word means, because we decide what the word means. If your definition of life is such that nanobes satisfy the criteria put forward in your definition then nanobes are life according to your definition.

If life is defined as self-replicating units then something that uses another organism or catalyst to replicate would not be life according to this definition, but it could be called "proto-life", as you said. Perhaps, life evolved from proto-life: Some catalyst replicated some units and at some point some units 'learned' to incorporate the catalyst into themselves becoming the first self-replicating organisms.

TooMany
2012-Dec-07, 05:01 PM
There are a great number of people studying many (maybe hundreds) of different ways in which abiogenesis may have happened. These range from the plausible to the far out (<cough>panspermia<cough>). I'm not sure how much more open minded the researchers could be.

I wasn't referring so much to all researchers but rather to the insistence by some that there is a clear demarcation between life in non-life. Selfsim above has apparently read the paper I did and has emphasized that they concluded that these are not "living organisms". OK fine, but they also concluded that the are "self-propagating" mineral-fetuin complexes. The point I'm making is that when we are looking for primitive forms that might lead to what we consider "living organisms" today, those forms may not qualify as "life" but that is no reason to discount them as uninteresting in the pursuit of understanding how "living organisms" came to be.

TooMany
2012-Dec-07, 05:07 PM
If life is defined as self-replicating units then something that uses another organism or catalyst to replicate would not be life according to this definition, but it could be called "proto-life", as you said. Perhaps, life evolved from proto-life: Some catalyst replicated some units and at some point some units 'learned' to incorporate the catalyst into themselves becoming the first self-replicating organisms.

Right. That's a kind of path that could eventually lead to "living organisms" (a fairly restrictive term). If you go around looking just for "living organisms" in your search for the origins of life, you're not going to get too far.

Selfsim
2012-Dec-08, 01:12 AM
Interesting to note from the Raoult study, is the 15 or so detailed tests, needed to probe the beastie.

However, they seem to be a little confused about why they had to perform these particular tests, though. In the summary section they say:
The comprehensive characterization of nanobacteria was the focus of our study. Our results definitively ruled out the existence of nanobacteria as living entities …{etc}Then they go on and say in the conclusion:
As recently reviewed [9], while associated with several diseases, nothing was done to identify or characterize the novel form of life known as “nanobacteria.”

I suspect that if the nanons had no pathanogenic properties, (or known associations with calcification in the human body), then perhaps such a comprehensive suite of tests may not have been absolutely needed, but that, in itself, raises a very interesting issue.

For example, if this degree of testing is what is needed, here on Earth, to produce a definitive statement about how a previously unknown 'thing' fits into our understanding of biology, how can we even remotely think that some telescope detecting O2 or CH4, (etc), in some exo-planetary atmosphere, could possibly mean anything at all, when it comes to diagnosing the characteristics of life?

The thought of remote probes being able to be designed for, and executing such tasks remotely, (and, as in this case, to rule out other known Earth-life possible organism categories), is almost absurd! Take a look at what they had to go through, just to be able to set up the tests ..!!..

Even the thought that multiple autonomous probes, operating over light-year distances, sent out en masse, (in order to cover a reasonable sample space), could achieve this, and return any level of confidence in the results, is also well and truly into the realm of science-fiction!

Sorry folks … I just don't think anyone is seriously thinking about the impracticalities of testing anything beyond our immediate Solar System neighbourhood, in order to reach any sort of useful conclusion … and this study highlights what it takes to reach a (relatively) definitive one.

If the tests themselves aren't practical, then neither is diagnosing remote exo-life over light-year distances. There can be no meaning from any remote 'discovery' if we have no practical tests.

TooMany
2012-Dec-08, 06:52 PM
Interesting to note from the Raoult study, is the 15 or so detailed tests, needed to probe the beastie.

However, they seem to be a little confused about why they had to perform these particular tests, though. In the summary section they say:Then they go on and say in the conclusion:

I suspect that if the nanons had no pathanogenic properties, (or known associations with calcification in the human body), then perhaps such a comprehensive suite of tests may not have been absolutely needed, but that, in itself, raises a very interesting issue.

For example, if this degree of testing is what is needed, here on Earth, to produce a definitive statement about how a previously unknown 'thing' fits into our understanding of biology, how can we even remotely think that some telescope detecting O2 or CH4, (etc), in some exo-planetary atmosphere, could possibly mean anything at all, when it comes to diagnosing the characteristics of life?

The thought of remote probes being able to be designed for, and executing such tasks remotely, (and, as in this case, to rule out other known Earth-life possible organism categories), is almost absurd! Take a look at what they had to go through, just to be able to set up the tests ..!!..

Even the thought that multiple autonomous probes, operating over light-year distances, sent out en masse, (in order to cover a reasonable sample space), could achieve this, and return any level of confidence in the results, is also well and truly into the realm of science-fiction!

Sorry folks … I just don't think anyone is seriously thinking about the impracticalities of testing anything beyond our immediate Solar System neighbourhood, in order to reach any sort of useful conclusion … and this study highlights what it takes to reach a (relatively) definitive one.

If the tests themselves aren't practical, then neither is diagnosing remote exo-life over light-year distances. There can be no meaning from any remote 'discovery' if we have no practical tests.

If this is so futile, I think you should let the astrobiologists know so they can find another career.

We have taken only the first baby steps. Our instruments are primitive in comparison with what is possible. Just four centuries ago Galileo discovered the moons of Jupiter. One half century ago, the first satellite was orbited. In the past 20 years our space craft have had a close up look at the moons of Jupiter and Saturn.

Selfsim
2012-Dec-08, 11:28 PM
If this is so futile, I think you should let the astrobiologists know so they can find another career. Astrobiology is some kind of 'craft', looking to explain its own subject matter, I think ...


We have taken only the first baby steps. Our instruments are primitive in comparison with what is possible. Just four centuries ago Galileo discovered the moons of Jupiter. One half century ago, the first satellite was orbited. In the past 20 years our space craft have had a close up look at the moons of Jupiter and Saturn.How does any of that change the idea of wide-scale testing of exo-'worlds', (in order to categorise some form of exo-life discovery), from presently being science fiction?

TooMany
2012-Dec-08, 11:58 PM
Astrobiology is some kind of 'craft', looking to explain its own subject matter, I think ...

How does any of that change the idea of wide-scale testing of exo-'worlds', (in order to categorise some form of exo-life discovery), from presently being science fiction?

Well, if you mean everything is science fiction until you actually do it then yes, it's science fiction. But if the connotation of "science fiction" is supposed to mean hopelessly impractical or fantasy, then no.

Selfsim
2012-Dec-09, 01:08 AM
Well, if you mean everything is science fiction until you actually do it then yes, it's science fiction. But if the connotation of "science fiction" is supposed to mean hopelessly impractical or fantasy, then no.Not realistic would seem to suffice.

MaDeR
2012-Dec-10, 07:31 PM
Sorry folks … I just don't think anyone is seriously thinking about the impracticalities of testing anything beyond our immediate Solar System neighbourhood, in order to reach any sort of useful conclusion…
As far I know, sciencists are fairly sure about results of remotely sensing, say, chemical composition of stars and the like without personally testing star matter in labolatories here on Earth. They also seems to be pretty sure of useful conclusions derived from remote sensing, like size, age of universe, laws of physics and all of that. Claims that remote sensing on planetary scale suddenly somehow ceases to be useful is just nothing more than...


and this study highlights what it takes to reach a (relatively) definitive one. If the tests themselves aren't practical, then neither is diagnosing remote exo-life over light-year distances. There can be no meaning from any remote 'discovery' if we have no practical tests.
...fervent preemptive denial.

Selfsim
2012-Dec-10, 11:01 PM
As far I know, sciencists are fairly sure about results of remotely sensing, say, chemical composition of stars and the like without personally testing star matter in labolatories here on Earth. They also seems to be pretty sure of useful conclusions derived from remote sensing, like size, age of universe, laws of physics and all of that. Claims that remote sensing on planetary scale suddenly somehow ceases to be useful is just nothing more than…The 'useful conclusions', in the sense I was referencing, is limited to any detections which would lead scientists to call upon the results capable of being generated by the type of tests executed in this report. (Meaning suspected biology of some kind). Clearly there is scientific value which results from remote spectrographic detections. (Eg: it adds to knowledge about the spread of diverse compounds and elements throughout the universe, including also exo-planet atmospheres, etc).

I wonder what would have happened if this discovery was made on Mars (or some other non-Earth planet .. which I think, was one of TooMany's original points)? (Speculators are gonna love that question …)

To the best of my knowledge, the LR style tests on Viking, are about the most advanced remotely executable tests for biology beyond Earth, so far attempted. The tests performed in this particular study however, went way beyond the Viking style of tests.

The impetus for the Raoult (et al) tests, seems to have been attributable to the suspected pathogenic implications of the initial finding. This would also seem to be quite a valid approach for characterising something not yet known, no matter where its discovered. If such tests were decided to be needed, it would seem that the complexity involved in executing them, calls for the presence of human experimenters working directly on the sample. A return sample expedition might be the simplest way of doing this, but removing samples from their natural environments, and expecting them to retain their native properties, for the duration of such a voyage, would also introduce some degree of uncertainty, (the details of which, cannot be predicted at this point). The idea of gathering them, and then returning them over light year distances for testing, and then producing meaningful results, calls into question, the basis of the practicality of the exo-life hypothesis' ability to contribute value for science, within some reasonable measures of certainty, in the present.

The most sophisticated remote (and compact) biology test I've seen to date, is bound on a single bio-chip which makes use of antibodies to detect biological materials like sugars, DNA and proteins, (IIRC).



and this study highlights what it takes to reach a (relatively) definitive one {conclusion}. If the tests themselves aren't practical, then neither is diagnosing remote exo-life over light-year distances. There can be no meaning from any remote 'discovery' if we have no practical tests....fervent preemptive denial. .. a statement of scientific reality in the present.

When it involves complexity, the future is uncertain, and thus cannot be denied or accepted.

TooMany
2012-Dec-11, 12:01 AM
When it involves complexity, the future is uncertain, and thus cannot be denied or accepted.

And so what is your point? That we should be so skeptical about all possibilities that we should abandon their pursuit? Sorry, but it's the optimists who accomplish things, not the pessimists who a priori declare their impracticality or worthlessness.

Selfsim
2012-Dec-11, 02:21 AM
And so what is your point? That we should be so skeptical about all possibilities that we should abandon their pursuit?No. Where did that come from?

Sorry, but it's the optimists who accomplish things, not the pessimists who a priori declare their impracticality or worthlessness.You seem to constantly relate a pragmatic outlook with a pessimistic one. Why do that?

Science is about the quest for knowledge. I'm personally quite passionate about acquiring that knowledge.
Aren't you?

MaDeR
2012-Dec-11, 07:15 PM
Clearly there is scientific value which results from remote spectrographic detections. (Eg: it adds to knowledge about the spread of diverse compounds and elements throughout the universe, including also exo-planet atmospheres, etc).
Remote results about composition of exo-planet atmosphere can indicate elements, signatures and composition that is, according to current knowledge, impossible to explain without life. You, since your apperance here, oppose against this possibility for reasons that are, at best, unclear for me.

I cannot see any wiggle room in this. Either remote results can be useful, or they cannot. Remote sensing of exoplanet atmosphere is no different than remote sensing of star atmosphere. Spectra is spectra is spectra. Diffference is only in sensitivity of instruments. In fact, we already played with certain measurements of hot jupiter's atmospheres (temperature and basic chemistry).

This is why many independent confirmations of life-indicating results from remote sensing will be recognized as good evidence of exolife on scale that is capable of changing exoplanet atmosphere in significant way. No need for precise local measurements of methane at level of 5 ppm or whatever you need to research dead or almost dead planet like Mars. Successful, prevalent life, like life on Earth, will be detectable without problems with anyone having sufficient remote sensing technology - that will be achieved in our lifetime.

Colin Robinson
2012-Dec-12, 12:43 AM
Remote results about composition of exo-planet atmosphere can indicate elements, signatures and composition that is, according to current knowledge, impossible to explain without life.

I wonder whether you're right about this... The chemical compositions associated with life can, in principle, be produced without life... Say we find an Earth-like planet with abundant O2 in its atmosphere and organic compounds at or near the surface... Certainly one explanation would be a population of organisms performing photosynthesis. Another explanation might be a series of chemical reactions — solar energy breaking up water into hydrogen and oxygen, some of the hydrogen then combining with CO2 to produce organics, and some of those organics have catalytic properties which facilitate both break up of water and hydrogenation of carbon dioxide... After all, this is what photosynthesis actually is, when you look at it chemically...


Either remote results can be useful, or they cannot.

Remote results can certainly be useful, in the sense that they provide useful pieces for the jigsaw puzzle we have to solve, if we want to know the big picture about life in the universe.

Other pieces of the jigsaw puzzle can be provided by other current and future research programs, including:

* missions like Cassini and Curiosity to Earth's neighbors, the worlds of our own solar system,
* Earth-based study both of the range of living things here, and also of complex phenomena which resemble life — for instance, the self-perpetuating organic-mineral complexes called "nanons" in the OP article of this thread.

Selfsim
2012-Dec-12, 01:19 AM
Remote results about composition of exo-planet atmosphere can indicate elements, signatures and composition that is, according to current knowledge, impossible to explain without life.Not 'impossible' … in the language of the LIS Forum, just "not likely".

(If the paradigm which seems to unfortunately reign supreme in this Forum, is also attempting to be consistent, then precision in statements drawn from it, should at least be evident. I'll allow myself the exception of using this speculative style of argument, to assist in making the point easier to relate to).


You, since your apperance here, oppose against this possibility for reasons that are, at best, unclear for me.That would be because my position is that whilst what you mention might be our 'best present estimate', there is plenty of evidence that there are natural processes in operation in exo-environments, which we have not yet incorporated into those models. Ie: our models are incomplete, and are almost exclusively generalised from an instance of one planet having abundant life, (for which there is abundant data). We have only an extremely limited sample (or knowledgebase) about what processes can result in 'what' by-products, in other atmospheres. We already know our models are incomplete. Where incompleteness exists, uncertainty exists. Where uncertainty exists in complex systems, prediction at certain levels of scales, is not possible. Attempts to make predictions are subject to the resultants of those uncertainties. (This is a mathematically proven theorem from fractal geometry .. not some philosophical view). We also know from our own local Solar System, that diversity of environments is abundantly evident .. no two atmospheres are the same, in detail. No two planets (collectively) have evolved communicative, 'intelligent' lifeforms. (Have you ever considered why that is so?).


I cannot see any wiggle room in this. Either remote results can be useful, or they cannot. Remote sensing of exoplanet atmosphere is no different than remote sensing of star atmosphere. Spectra is spectra is spectra. Diffference is only in sensitivity of instruments. In fact, we already played with certain measurements of hot jupiter's atmospheres (temperature and basic chemistry).All you have said is that remote spectroscopy is a sound science … and I'm in complete agreement with that. As far as drawing inference about the complex systems being necessarily the sole cause of those observations, is something completely different. Do you see why?


This is why many independent confirmations of life-indicating results from remote sensing will be recognized as good evidence of exolife on scale that is capable of changing exoplanet atmosphere in significant way. .. and yet you accuse me of "… fervent preemptive denial"?? :)

I'd call that a classic example of "fervent pre-emptive affirmation" ...


No need for precise local measurements of methane at level of 5 ppm or whatever you need to research dead or almost dead planet like Mars.'Almost dead planet like Mars'???? Huh??? (So we know that already, eh??)


Successful, prevalent life, like life on Earth, will be detectable without problems with anyone having sufficient remote sensing technology - that will be achieved in our lifetime.… Well, if you say so, I s'ppose .. :shouldershrug:

Selfsim
2012-Dec-12, 01:36 AM
I wonder whether you're right about this... The chemical compositions associated with life can, in principle, be produced without life… There are chemical compounds which are also regarded as being so artificial that their presence, if detected in an exo-atmosphere, would be considered 'almost conclusive' evidence of life.

A reasonable scientist might concede to a conclusion of it being highly 'suspicious of life', should such a compound be discovered via remote spectroscopy. That's Ok .. this may serve as a basis for falsification. Before such a detection occurs, the unanswerable question then becomes: 'How likely is it that such a compound might be discovered' … which is almost equivalent to: 'how prevalent is exo-life in the universe' .. (a fairly moot point, therefore).

John Mendenhall
2012-Dec-12, 01:39 AM
How about self reproducing and capable of evolving as a definition for life? Gets us around the crystal problem.

Colin Robinson
2012-Dec-12, 01:54 AM
No need for precise local measurements of methane at level of 5 ppm or whatever you need to research dead or almost dead planet like Mars.


'Almost dead planet like Mars'???? Huh??? (So we know that already, eh??)

I agree with MaDeR's statement, except that MaDeR has overstated the methane level in the atmosphere of Mars. It is actually measured in parts per billion (ppb), not parts per million (ppm). 10 ppb is a figure based on observations from the Mars Express Orbiter and the Canada-France-Hawaii telescope.

Bottom line is that the atmosphere is very very close to chemical equilibrium. This means there is very little happening there chemically. If you accept that chemistry is a necessary part of life, surely it follows that Mars is "dead or almost dead"?

Selfsim
2012-Dec-12, 08:19 AM
I agree with MaDeR's statement, except that MaDeR has overstated the methane level in the atmosphere of Mars. It is actually measured in parts per billion (ppb), not parts per million (ppm). 10 ppb is a figure based on observations from the Mars Express Orbiter and the Canada-France-Hawaii telescope. So the concentration level somehow leads to a conclusion, or a non conclusion of life existence, eh? So just how is the concentration threshold decided? Where does that come from and how 'likely'/'unlikely' are those assumptions elsewhere in the universe? (And why?)


Bottom line is that the atmosphere is very very close to chemical equilibrium. This means there is very little happening there chemically. If you accept that chemistry is a necessary part of life, surely it follows that Mars is "dead or almost dead"?Chemical reactions can still occur in a system which has reached chemical equilibrium ... this is called dynamic equilibrium. In fact, it is unlikely that this condition could be detected remotely via spectroscopy.

Colin Robinson
2012-Dec-12, 12:50 PM
So the concentration level somehow leads to a conclusion, or a non conclusion of life existence, eh? So just how is the concentration threshold decided? Where does that come from and how 'likely'/'unlikely' are those assumptions elsewhere in the universe? (And why?)

Chemical reactions can still occur in a system which has reached chemical equilibrium ... this is called dynamic equilibrium. In fact, it is unlikely that this condition could be detected remotely via spectroscopy.

I've replied to this in a new thread, as we seem to have moved away from the original topic of this one "How Small Can Life Be?".

MaDeR
2012-Dec-12, 03:44 PM
I wonder whether you're right about this... The chemical compositions associated with life can, in principle, be produced without life. Say we find an Earth-like planet with abundant O2 in its atmosphere and organic compounds at or near the surface
Main point is that known non-biological sources cannot maintain this kind of atmosphere for planet like ours. Without life, Earth would have oxygen fall to background level in about 300 years - blink in a eye for astronomy. This is why detecting planet like Earth with atmosphere like Earth's would be very strong evidence for presence of life similiar to our kind. Caveat "like Earth" is important. For example, literal waterworlds according to current theories could have certain significant level of oxygen with abiological sources only.


We already know our models are incomplete. Where incompleteness exists, uncertainty exists. Where uncertainty exists in complex systems, prediction at certain levels of scales, is not possible. Attempts to make predictions are subject to the resultants of those uncertainties.
All you say is useless truism. Nothing is certain, indeed - but that apllies to everything in science, not only exolife search.

For example, all these "planets" remotely discovered could be Borg cubes with same mass - and with current technology it is impossible to distinguish those two. Somehow those darn sciencists still insists they are planets.
Oh, by the way: creating planets is very complex thing, there are many models that are incomplete, we still do not know much about it... sounds familiar? Yet many exoplanets are considered as actually existing with very high degree of certainity.


As far as drawing inference about the complex systems being necessarily the sole cause of those observations, is something completely different. Do you see why?
Protip for you: getting to know about something (life, planet) is not related to complexity of process that leads to existence of that something (be it planet or life). This is why argument "oh noes it is COMPLEX!" don't have any validity.




This is why many independent confirmations of life-indicating results from remote sensing will be recognized as good evidence of exolife on scale that is capable of changing exoplanet atmosphere in significant way.
.. and yet you accuse me of "… fervent preemptive denial"?? :) I'd call that a classic example of "fervent pre-emptive affirmation" ...
This is case of "exact words". I did not claimed we surely will find exolife (my personal opinion is that we will indeed, but this was not topic of discussion). I claimed remote sensing is sufficient to detect exolife with high degree of certainity.


'Almost dead planet like Mars'???? Huh??? (So we know that already, eh??)
Dead or almost dead. If Mars was teeming with life like on Earth, we would know it for centuries already.

Paul Wally
2012-Dec-12, 10:34 PM
How about self reproducing and capable of evolving as a definition for life? Gets us around the crystal problem.

That is an elegant definition that I particulary like, perhaps because of it's universality. I.e. it doesn't make arbitrary distinctions like size or place. It doesn't even say anything about any particular chemistry or any particular physical medium for that matter.

So the question relevant to this thread is how small can a self-replicating evolvable thing be? What is the theoretical scale limit?

I think the fundamental unit of replication is memory. This memory must contain unique information and it is this unique information that must be replicated, and if over time this information can randomly change slightly then the memory would also be evolvable. So one can ask: What is the smallest scale at which information can be stored and replicated, and in what kind of physical medium would that be naturally possible?

Colin Robinson
2012-Dec-12, 10:49 PM
Main point is that known non-biological sources cannot maintain this kind of atmosphere for planet like ours. Without life, Earth would have oxygen fall to background level in about 300 years - blink in a eye for astronomy.

Yes, I've seen similar statements... Perhaps the reason scientists can say that sort of thing, is that they've studied Earth much more thoroughly than any other planet...


This is why detecting planet like Earth with atmosphere like Earth's would be very strong evidence for presence of life similiar to our kind. Caveat "like Earth" is important. For example, literal waterworlds according to current theories could have certain significant level of oxygen with abiological sources only.

Yes, if another world was like a twin of Earth, and had a similar amount of oxygen in its atmosphere, that would be taken as very strong evidence for life.

On the other hand, we may find continue to find worlds which are not twins of Earth though they may resemble Earth in various ways. In that case it will be more of a challenge to work out whether an unusual chemical mix in the atmosphere is due to life, or due to simple but unfamiliar chemistry, or due to a chemistry which is far from simple and which might be considered "protolife" — e.g. something like a "nannon"...

Selfsim
2012-Dec-13, 05:30 AM
I think the fundamental unit of replication is memory. This memory must contain unique information and it is this unique information that must be replicated, and if over time this information can randomly change slightly then the memory would also be evolvable. So one can ask: What is the smallest scale at which information can be stored and replicated, and in what kind of physical medium would that be naturally possible?This question closely parallels (I think), the new Paul Davies approach of looking at abiogenesis from an informational modelling perspective.

I've started a new thread about the paper here:

http://cosmoquest.org/forum/showthread.php/140239-Abiogenesis-The-Information-Model?p=2088311#post2088311