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A.DIM
2013-Apr-20, 11:10 PM
Life Before Earth (http://arxiv.org/ftp/arxiv/papers/1304/1304.3381.pdf), using "Moore's Law" applied to genetic complexity, argues the origin of life dates to ~9G years ago. Personally, I'm neither surprised nor overly skeptical of such a conclusion, as I think life in the universe arose as soon as it was cool enough with plentiful ingredients. Some interesting questions, and assertions, arise...

From the abstract: This cosmic time scale for the evolution of life has important consequences: (1) life took a long time (ca. 5 billion years) to reach the complexity of bacteria; (2) the environments in which life originated and evolved to the prokaryote stage may have been quite different from those envisaged on Earth; (3) there was no intelligent life in our universe prior to the origin of Earth, thus Earth could not have been deliberately seeded with life by intelligent aliens; (4) Earth was seeded by panspermia; (5) experimental replication of the origin of life from scratch may have to emulate many cumulative rare events; and (6) the Drake equation for guesstimating the number of civilizations in the universe is likely wrong, as intelligent life has just begun appearing in our universe.

Nick Theodorakis
2013-Apr-20, 11:29 PM
He cherry-picks a few data points in order to draw a graph then extrapolates through time to find when life began with one base pair? Here's what Mark Twain has to say about extrapolation:



"In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact."

- from Life on the Mississippi


Further critiqued here:

http://scienceblogs.com/pharyngula/2013/04/18/graaarh-physicists-biologists/

Nick

Ronald Brak
2013-Apr-21, 02:30 AM
It's all very silly. If you look at the evolution of complexity in parasites and extrapolate that you'll see that life was more complex before the big bang occurred.

eburacum45
2013-Apr-25, 11:58 AM
We discussed this before, when Sharov first came up with the idea back in 2009. The idea that we can extrapolate backwards like this is almost certainly wrong, for many reasons; first they use the complexity of modern prokaryotes and eukaryotes as an indication of primeval organisms; since they have been evolving for billions of years, this need not be accurate.

Secondly, if you extrapolate other phenomena backwards in this way you end up with wrong answers- the growth of a human being extrapolated backwards suggests that we are all created many months before we are conceived.

Ara Pacis
2013-Apr-25, 09:27 PM
I didn't read it, so I'll ask. Does the extrapolation take into account the possibility of multiple processors? IIRC, Moore's law is considered still valid only because we're increasing processing capability by using parallel processing whereas the rate of increase in processing power of individual CPUs is slowing down. So, I guess I'm asking if the paper includes horizontal gene transfer as part of it's complexity model for back-dating.

BioSci
2013-Apr-25, 09:58 PM
I didn't read it, so I'll ask. Does the extrapolation take into account the possibility of multiple processors? IIRC, Moore's law is considered still valid only because we're increasing processing capability by using parallel processing whereas the rate of increase in processing power of individual CPUs is slowing down. So, I guess I'm asking if the paper includes horizontal gene transfer as part of it's complexity model for back-dating.

Nope, just takes the log value of genome size of unidentified "procaryotes," "eucaryotes," "worms," "fish," & "mammals," modifies the data to represent "functional non-redundant genome", plots verses billions of years, and then extrapolates a simple straight line back to a single base pair as being the start of life!

A good example of pathetic science (not even junk level).

tnjrp
2013-Apr-26, 05:13 AM
It needs to be noted that the authors do seem to present their thought experiment as exactly that. The science reporters look to be erring more on the side of drawing actual conclusions, but that is not new of course.

It also needs to be noted that Moore's law has fairly well held for a product of Lamarckian cultural evoluion. It is not at all automatically applicable to Darwinian biological evolution.

A.DIM
2013-May-17, 04:00 PM
Hi All, and thanks for taking the time. Sorry I’ve not been present to discuss the paper; although it seems of little interest and easily dismissed here. Ah well …
It’s an interesting read, in my mind, even while there is no consensus on the measurement of genomic functional complexity, let alone the origin of life. My main hang up though, was the authors’ ignoring HGT entirely, and arguing against punctuated equilibrium, as major factors in biological evolution. Horizontal Gene Transfer, as I understand it, has the potential to change the way we consider neo-Darwinian evolution and macro-evolutionary development. Whatever the case, earliest known life on Earth was essentially identical to modern life on Earth, biochemically, and so there remain huge gaps in our understand as to how bio chemical goo became life on Earth, especially in as few as ~500 million years.

It’s a puzzle to be sure: either abiogenesis occurred on Earth and life quickly evolved to the complexity with which we find it(~3.5Gyrs ago), suggesting an easy occurrence given the right conditions; or, abiogenesis occurred on Earth in a rare one off event resulting in biochemically complex life arising rapidly, which suggests “special” circumstances, and pleading.

That life may have originated not on Earth but elsewhere, and was transported to Earth extends the timeframe and potential sites for abiogenesis and early evolution; a good reason why it remains an open question and a valid hypothesis.

Swift
2013-May-17, 05:04 PM
It’s a puzzle to be sure: either abiogenesis occurred on Earth and life quickly evolved to the complexity with which we find it(~3.5Gyrs ago), suggesting an easy occurrence given the right conditions; or, abiogenesis occurred on Earth in a rare one off event resulting in biochemically complex life arising rapidly, which suggests “special” circumstances, and pleading.

That life may have originated not on Earth but elsewhere, and was transported to Earth extends the timeframe and potential sites for abiogenesis and early evolution; a good reason why it remains an open question and a valid hypothesis.
And I have the exact opposite feeling, and is why I find abiogenesis an "unattractive" idea. By stating life originated elsewhere and was transported here, you are just "moving the goal posts" (or shoving the problem to some other planet's backyard), but you haven't gotten rid of that "problem", and now you added the problem of how this life was transported over interstellar distances. Among the three options: it is "an easy occurrence" for life to form, it is not an easy occurrence for life to form and Earth just happened to be lucky, or life was transported here over interstellar distances, I personally find the third choice the hardest to believe (and yes, I used the word "believe" deliberately - I'm only expressing my opinion).

A.DIM
2013-May-17, 05:58 PM
And I have the exact opposite feeling, and is why I find abiogenesis an "unattractive" idea. By stating life originated elsewhere and was transported here, you are just "moving the goal posts" (or shoving the problem to some other planet's backyard), but you haven't gotten rid of that "problem", and now you added the problem of how this life was transported over interstellar distances. Among the three options: it is "an easy occurrence" for life to form, it is not an easy occurrence for life to form and Earth just happened to be lucky, or life was transported here over interstellar distances, I personally find the third choice the hardest to believe (and yes, I used the word "believe" deliberately - I'm only expressing my opinion).

I understand, all too well; it's mostly a matter of preference. But I don't see it so much as "moving the goalposts" as I do "expanding the storyline" (of life in the universe, and on Earth)while removing the problem of too little time. Yes, there's an added problem, and certainly interstellar transport has its hurdles, but galactic collisions, stellar interactions, supernovae (the authors' suggested method), comets, wandering planets, etc. seem plausible mechanisms for spreading life around. Although, it doesn't have to be interstellar in nature. Abiogenesis may have occurred elsewhere in our solar system (if not within the gas/debris cloud which it form), and then deposited on Earth. This also eases the problem of too little time. As you know, I believe, of the three options you outline, the third is as plausible as any other, the first is completely acceptable but the second is not. These "rare, special, unique" scenarios, in my view, are too akin to other special-pleading belief systems; namely, creationism.

I appreciate you taking the time Swift!

Selfsim
2013-May-18, 06:56 AM
These "rare, special, unique" scenarios, in my view, are too akin to other special-pleading belief systems; namely, creationismThen don't think of them as "rare, special, unique scenarios". These concepts have come from within the mind .. there's not a shred of evidence that any of them are physically real!

If you had never heard of "Creationism", would your views be skewed by it? Clearly they are .. and therein lies and unrelated bias!

Hlafordlaes
2013-May-18, 01:20 PM
Local, and not necessarily interstellar, meteorites could have been crucial in the seeding of Earth's surface with chemical precursors, sure. The emergence of life in our system does seem much more likely to involve the entire local system, given the exchange of material among bodies.

I just wish I could send a nickel to NASA every time I think about it. We have exciting hypotheses aplenty, now we need the boring grunt work. Years of it.

A.DIM
2013-May-20, 05:42 PM
Then don't think of them as "rare, special, unique scenarios".

Indeed, which is why I maintain a “nothing special here” attitude towards life in the universe (I think it’s everywhere!).

If organic goo became (“primitive” yet highly complex) life on Earth in such a narrow time frame, this suggests the process readily occurs, in the right conditions. Should we assume those conditions were rare, unique or special since we cannot figure out how it happened? Or should we assume physics and chemistry are everywhere the same, that given the right conditions and ingredients, life inevitably happens?


If you had never heard of "Creationism", would your views be skewed by it? Clearly they are .. and therein lies and unrelated bias!

Admittedly, I am biased against creationist thinking, of all sorts (I still can’t get over my aversion to the ex nihilo BBT mindset), but I don’t think that biases my opinion on life on the universe. My “creationist” remark was in response to Swift calling life on Earth a “lucky” accident, which is but a version of the “rare earth” hypothesis. Perhaps I could’ve used another term, but “lucky accident” is too close to “miracle” for my liking. Miracles and lucky accidents generally aren’t repeatable, testable, and don’t seem to fit with scientific reasoning. In a universe which appears naturally geared to produce life as we know it (and spread it around!), why should we assume (and thus prefer) such a lucky accident, such a rare or unique event, is what brought about life on Earth?

A.DIM
2013-May-20, 06:09 PM
Local, and not necessarily interstellar, meteorites could have been crucial in the seeding of Earth's surface with chemical precursors, sure. The emergence of life in our system does seem much more likely to involve the entire local system, given the exchange of material among bodies.

No doubt in my mind. I even have difficulty thinking of our stellar neighborhood as a "closed system," what with stellar perturbations, extrasolar comets, wandering planets etc.
But you might find interesting Comets and the Origin and Evolution of Life, edited by Thomas, Hicks, Chyba and McKay, which deals with what you say. In it, they come very close to supporting (without even a wink, nod or footnote to the theory's originators!) cometary panspermia.

Thanks for the input!

Swift
2013-May-21, 12:48 AM
My “creationist” remark was in response to Swift calling life on Earth a “lucky” accident, which is but a version of the “rare earth” hypothesis. Perhaps I could’ve used another term, but “lucky accident” is too close to “miracle” for my liking. Miracles and lucky accidents generally aren’t repeatable, testable, and don’t seem to fit with scientific reasoning.
Just to be clear, I listed three scenarios: life forms easily, life doesn't form easily (but did on Earth - "rare" or "lucky"), life was transported here. I only expressed a dislike of choice three, I have no opinion between the other two. I have no clue as to whether life is rare or common.

I think you are reading entirely too much into the word "lucky"; though "rare" is probably a "more better" word. And rare events, while more difficult to test, are not the same as miracles, and are still within the realm of science.

Nick Theodorakis
2013-May-21, 01:03 AM
This is one case in which the anthropic principle is actually applicable. We can't really tell how rare it is because we are by necessity living in a place where it is possible. If we find life elsewhere in the solar system, and it is clearly independent of ours, then we can start to make some guesses.

Nick

Selfsim
2013-May-21, 01:32 AM
Indeed, which is why I maintain a “nothing special here” attitude towards life in the universe (I think it’s everywhere!)... then try not thinking about it as "nothing special here" …
Try thinking "nothing", (or "don't know")!
It opens up way more opportunities, y'know .. ;) :)
:)


If organic goo became (“primitive” yet highly complex) life on Earth in such a narrow time frame, this suggests the process readily occurs, in the right conditions. Should we assume those conditions were rare, unique or special since we cannot figure out how it happened? Well, that we can't figure out how it happened would seem to be an indicator of something, eh?
Or should we assume physics and chemistry are everywhere the same, that given the right conditions and ingredients, life inevitably happens? Assuming "physics and chemistry are everywhere the same" says nothing new on the topic of life emergence.. its a moot point. "The right conditions and ingredients" is similar, seeing as we don't know what "the right conditions and ingredients" are.

Making "assumptions", is no substitute for actually finding out via unbiased exploration!


Admittedly, I am biased against creationist thinking, of all sorts (I still can’t get over my aversion to the ex nihilo BBT mindset), but I don’t think that biases my opinion on life on the universe. My “creationist” remark was in response to Swift calling life on Earth a “lucky” accident, which is but a version of the “rare earth” hypothesis. Perhaps I could’ve used another term, but “lucky accident” is too close to “miracle” for my liking. Miracles and lucky accidents generally aren’t repeatable, testable, and don’t seem to fit with scientific reasoning. In a universe which appears naturally geared to produce life as we know it (and spread it around!), why should we assume (and thus prefer) such a lucky accident, such a rare or unique event, is what brought about life on Earth?I can't see anything scientifically wrong with 'apparent uniqueness' existing within a search space conceived by beings of average dimensions of say, for eg: height ~174 cms (etc).

I mean is there, (or has there ever been in the evidenced history of life on Earth), an exact duplicate of A.DIM?

Matej Velko
2013-May-21, 08:54 PM
In a universe which appears naturally geared to produce life as we know it (and spread it around!), why should we assume (and thus prefer) such a lucky accident, such a rare or unique event, is what brought about life on Earth?

The same could be extrapolated to the universe itself (...in a way); There is no conceivable meaning of the universe (seeing it as not anthropomorphic) despite the fact it wasn't a lucky accident (I believe that would be your assumption considering you assume life is not an accident). The fact that an accident led to such complex, yet not understood, arrangement of atoms and molecules (preferably nothing more) forming life is counter-intuitive does not exclude it from being true ... just consider quantum theory.

Hlafordlaes
2013-May-21, 09:26 PM
Didn't want to start a new LiS thread just for this, but there is a nice piece today (http://arstechnica.com/science/2013/05/linking-simple-chemistry-to-something-like-life/) on prebiotic chemistry over on Ars. Readers here might be interested.

As I mention in the comments there, when you start putting together the little data we have so far, it appears the entire local disk may the system level one needs to take into account to derive the processes leading to life. The goalposts don't move in the sense that we still need to find how it happened on Earth's surface, but the surface needs to be seen as very much part of the system-wide chemistry, not just what might spew out of a volcano or fumarole. IMHO from my reading of the reports coming in here and there, at least.

Trakar
2013-May-21, 09:57 PM
I understand, all too well; it's mostly a matter of preference. But I don't see it so much as "moving the goalposts" as I do "expanding the storyline" (of life in the universe, and on Earth)while removing the problem of too little time. Yes, there's an added problem, and certainly interstellar transport has its hurdles, but galactic collisions, stellar interactions, supernovae (the authors' suggested method), comets, wandering planets, etc. seem plausible mechanisms for spreading life around. Although, it doesn't have to be interstellar in nature. Abiogenesis may have occurred elsewhere in our solar system (if not within the gas/debris cloud which it form), and then deposited on Earth. This also eases the problem of too little time. As you know, I believe, of the three options you outline, the third is as plausible as any other, the first is completely acceptable but the second is not. These "rare, special, unique" scenarios, in my view, are too akin to other special-pleading belief systems; namely, creationism.

I appreciate you taking the time Swift!

Indeed, perspective adds much to the consideration and understanding. To me "special" has a different connotation, in that rare sequences of circumstance are not "privileged or preferred" merely "unusual" and "atypical."

If talking anything more complex than base-protein seeding of stellar-nurseries, with regards to panspermia, then I would tend to side with Swift that the viable transit of more generally complex (cellular) life over interstellar distances and conditions, without intelligent design. Is by far the most difficult step. It is my considered opinion that life in general is a very rare phenomenon, with complex, intelligent and technological being additionally rare sequences of expression. I am not saying that we are without peer or superior in the universe, merely that until I find compelling evidence suggesting otherwise, it is not at all unreasonable to build upon the evidences at hand.

Perception comes from which evidences you view, how you vet and weight them, and which correlations you focus on. There are a lot of unknown unknowns, in this area of understanding with regards to our universe.

Selfsim
2013-May-21, 11:02 PM
Didn't want to start a new LiS thread just for this, but there is a nice piece today (http://arstechnica.com/science/2013/05/linking-simple-chemistry-to-something-like-life/) on prebiotic chemistry over on Ars. Readers here might be interested.

As I mention in the comments there, when you start putting together the little data we have so far, it appears the entire local disk may the system level one needs to take into account to derive the processes leading to life. The goalposts don't move in the sense that we still need to find how it happened on Earth's surface, but the surface needs to be seen as very much part of the system-wide chemistry, not just what might spew out of a volcano or fumarole. IMHO from my reading of the reports coming in here and there, at least.Consider that the 'system' may well be self-similar at all scales .. with unknown scale limits!

The emergence of order by means of self-assembly in a hierarchically viewed complex system, can typically happen by virtue of interactions amongst different levels of that system, or by interactions across any given level.

In evolution, co-operation, altruism, mutually beneficial symbiosis and their ultimately 'opposing' effects: competition for resource, advantageous adaptation, extinction, etc could be viewed as such hierarchical levels, (as an example), I suppose.

Considering the interplanetary disc as the boundary of such a complex system, I would think, would lead towards a broadening of potential hypothetical emergence environments .. on top of the hypothesised potential emergence micro-environments we are presently familiar with, (volcanos, fumaroles etc). Without evidence of the emergence of life elsewhere, I do not see how the development of such a model would lead to new knowledge(?) It might improve awareness of the complexities of biology and organic chemistry though .. (which would be an improvement over the current 'bake and shake, just add water' formulae, which seem to pervade current thinking on the topic, however).

Also, the potential variables in such a model, would easily outstrip and computational resource needed for analysis in such a simulation exercise. The modelling of a single cell already pushes those boundaries, and this is based on already known processes.

In summary, the establishment of such a model might sound nice in theory, but in reality, there is insufficient knowledge of the inputs, to make the outputs credible.

Hlafordlaes
2013-May-22, 02:04 AM
What I mean is that if you take the most probable elements available on the surface or under the ocean, based only on the workings of the posited local chemistry, you may not find solutions. Add bombardment close to volcanic pools that adds elements or molecules 'easier' to produce in space, then you have a rich enough primordial soup. So Earth's environment in the system in its conditions at the time is what I mean as the focus. Perhaps less panspermia than pan-prebiotica.

[Much later ETA:]

So the twin benefits of the approach are:
1) Better approach to looking at the problem on Earth
2) Identification of places in the system that, at the time, may have had any similar surface conditions.

The second item is the one that may indicate very early locations that may have become hostile to life shortly thereafter. The importance of this is that while geologically active places, such as Earth, may have eradicated initial conditions completely, there is a chance that by finding locations where the initial conditions may have held, say, for only 500m yrs, we can look for the earliest signs of the transitions from precursor to life. So, in theory, there may be a spot or two in places we have not yet looked that could provide good 'paleo-life' information. The false starts that also happened in the system, if you will.

Seaumas
2013-May-30, 12:35 AM
Firstly, it is absolutely and stgupidly arrogant to think we are the only ones out here or were the first ones. The Great Coalescence after the Big Bang created, during a very long time, everything structually and chemically needed to build a living molecule, then grow something recognizable. Our universe is at least 14 billion years old and we are only, say, 4 billion years old. And any life we would detect out in the universe with instruments we have now, or anytime in the near future, would already be millions of years old. Moore's Law? Howabout the Supreme Creator's Law?

tnjrp
2013-May-30, 04:50 AM
Firstly, it is absolutely and stgupidly arrogant to think we are the only ones out here or were the first onesPossibly so, tho both arguments can be somewhat rationally defended all the same. See in particular the rare Earth hypothesis for the first one. The other is a bit less well defined but there are some indications that -- at least for life as we know it -- conditions in the earlier universe were not all that conductive.


And any life we would detect out in the universe with instruments we have now, or anytime in the near future, would already be millions of years oldVery likely, if we assume (as many do) that we are roughly average. And even in the best case, it's a bit difficult to see how complex organisms at least would develop in just hundreds of thousands of years.


Moore's Law?Would be the subject of this thread, specifically as to if it can be assumed to hold for biological evolution. Even assuming we can draw conclusions about xenolife (and be advised that quite many on this forum quite stringently maintain that we cannot) it doesn't automatically make that particular assumption true.


Howabout the Supreme Creator's Law?I sense an infraction coming my way, but all the same: we have plenty of evidence of a certain Mr. Moore setting down his law. We don't have all that much evidence about Supreme Creator. Discussing His/Her/Its laws or lack thereof would therefore seem somewhat moot, especially given the prior focus of the thread.

Trakar
2013-Jun-07, 12:52 AM
Firstly, it is absolutely and stgupidly arrogant to think we are the only ones out here or were the first ones...

This is your unsupported assertion. It is up to you to compellingly support that belief.

A.DIM
2013-Jun-08, 01:13 PM
Just to be clear, I listed three scenarios: life forms easily, life doesn't form easily (but did on Earth - "rare" or "lucky"), life was transported here. I only expressed a dislike of choice three, I have no opinion between the other two. I have no clue as to whether life is rare or common.

I think you are reading entirely too much into the word "lucky"; though "rare" is probably a "more better" word. And rare events, while more difficult to test, are not the same as miracles, and are still within the realm of science.

Yeah, I may've read too much into "lucky" (the creationist quip was spillover from a separate issue I was addressing; apologies) and I'll agree "rare" is probably more better, though it seems mostly a matter of connotation. You were clear enough.

A.DIM
2013-Jun-08, 01:25 PM
This is one case in which the anthropic principle is actually applicable. We can't really tell how rare it is because we are by necessity living in a place where it is possible. If we find life elsewhere in the solar system, and it is clearly independent of ours, then we can start to make some guesses.

Nick

How do we find life as we don't know it?
Any guesses?
:D

A.DIM
2013-Jun-08, 01:30 PM
... Making "assumptions", is no substitute for actually finding out via unbiased exploration!
Agreed!
We need another life detection package sent to Mars, and others elsewhere!

A.DIM
2013-Jun-08, 01:36 PM
The same could be extrapolated to the universe itself (...in a way); There is no conceivable meaning of the universe (seeing it as not anthropomorphic) despite the fact it wasn't a lucky accident (I believe that would be your assumption considering you assume life is not an accident). The fact that an accident led to such complex, yet not understood, arrangement of atoms and molecules (preferably nothing more) forming life is counter-intuitive does not exclude it from being true ... just consider quantum theory.

Certainly, and I don't suggest there should be any "meaning" to life having arisen, other than the fact that in our universe twenty some constants make it so.

A.DIM
2013-Jun-08, 01:43 PM
Indeed, perspective adds much to the consideration and understanding. To me "special" has a different connotation, in that rare sequences of circumstance are not "privileged or preferred" merely "unusual" and "atypical."

If talking anything more complex than base-protein seeding of stellar-nurseries, with regards to panspermia, then I would tend to side with Swift that the viable transit of more generally complex (cellular) life over interstellar distances and conditions, without intelligent design. Is by far the most difficult step. It is my considered opinion that life in general is a very rare phenomenon, with complex, intelligent and technological being additionally rare sequences of expression. I am not saying that we are without peer or superior in the universe, merely that until I find compelling evidence suggesting otherwise, it is not at all unreasonable to build upon the evidences at hand.

Perception comes from which evidences you view, how you vet and weight them, and which correlations you focus on. There are a lot of unknown unknowns, in this area of understanding with regards to our universe.

Well put and I don't disagree. As I perceive the evidence, the simplest and most elegant explanation is that life as we know it arises inevitably in a universe with constants such as those we find in ours.

A.DIM
2013-Jun-08, 02:02 PM
Didn't want to start a new LiS thread just for this, but there is a nice piece today (http://arstechnica.com/science/2013/05/linking-simple-chemistry-to-something-like-life/) on prebiotic chemistry over on Ars. Readers here might be interested.

As I mention in the comments there, when you start putting together the little data we have so far, it appears the entire local disk may the system level one needs to take into account to derive the processes leading to life. The goalposts don't move in the sense that we still need to find how it happened on Earth's surface, but the surface needs to be seen as very much part of the system-wide chemistry, not just what might spew out of a volcano or fumarole. IMHO from my reading of the reports coming in here and there, at least.

I saw that; thanks for sharing here.
Again, I very much agree with your notion that it must at least have been a system wide event, if it occurred locally.

You and other readers may be interested in a couple recent and relevant pieces. The first of which addresses your points about phosphorus:

Solving a 3.5 Billion Year Old Mystery (http://news.usf.edu/article/templates/?z=38&a=5477) ... "Scientists may not know for certain whether life exists in outer space, but new research from a team of scientists led by a University of South Florida astrobiologist now shows that one key element that produced life on Earth was carried here on meteorites."

And then this (http://phys.org/news/2013-06-life-earth-shockingly-world.html) suggests "Cometary impacts could result in the synthesis of prebiotic molecules without the need for other 'special' conditions, such as the presence of catalysts, UV radiation, or special pre-existing conditions on a planet," Goldman said. "This data is critical in understanding the role of impact events in the formation of life-building compounds both on early Earth and on other planets and in guiding future experimentation in these areas."

IMO, we're a whisper away from saying biotic ingredients and molecules ...

;)