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I had been preparing a response between your recent responses, but didn't yet complete.

 

I have read your reference to "2+2", which I presume you intend to be equated with 4, "=4", and I'd like to point you to my thread on this subject, to which I am attempting to write follow-ups when I get time. ==>The 'logic' And Certainty (And Perils) Of '2 + 2 = 4'

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I am continuing to work on my response to this thread and your entries.

 

Yes, your replies were worth reading and I will make reference to "worthiness" in my reply.

 

---------------Added

 

hazelm, the only (singular) question I have entertained is, how did life originate on Earth?

 

Let me add here--just to dispose with it--that we have no persuasive evidence about whether or how it "originated", and whether it was eliminated, to "originate" again; and whether that has happened repeatedly.

 

With respect to exploration, I don't have any inclination to speculate about what may or may not be on planets outside our solar system. Is there a reason I should? One of the reasons I don't is that there is little reason to believe it will be possible soon or, possibly ever, to explore other solar systems.

 

With respect to our solar system, the only question I'll consider is, what would be the implications of finding it devoid of any life? Of course, this question follows a complete understanding of every word, particularly the qualifications, of my previous sentence:

 

Me: "When we have fully explored our solar system, we might get an answer or, at least, a clue."

 

I understand that others are motivated to speculate extensively and deeply without any significant evidence for any of it. I'm not inclined to do that.

 

Keep in mind that any meet-and-greet conducted by beings from outside our solar system would result in the end of all this speculation of all these subjects...hopefully!

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Yes the temperatures on comets would be too low for life to go on, but what we are talking about is the slow synthesis and transport to Earth of small building blocks (CH4, NH3, CH3OH, HCN, HCHO),  fr

There is a lot of questioning and debating about how life got its start.  This one from Science Daily is probably not new to some of you.  However, it just happens to be connected to my uneducated gue

Panspermia is a very popular theory which as you mention is getting more interest due to new hard evidence of extraterrestrial organic material.    It's also another chink in the already silly "irredu

Scherado, please keep in mind that I was reporting what the book says, not what I say.  That was the purpose of the post - to tell what the authors had to say about - well, the origin of water on Earth.  I did try to relate it to what you wanted to hear about life's origins but, as you see, there is little or no connection.  Also, the book was written thirteen yeas ago.  A  lot has come along since there.

 

Exchemist, are you still wanting to hear what the book says about the origins of water on Earth?  I do want to re-read that part.  I know there is a lot of speculation about it but these authors are only relating known facts as facts and labeling the guesses as unproven.

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Scherado, please keep in mind that I was reporting what the book says, not what I say. That was the purpose of the post - to tell what the authors had to say about - well, the origin of water on Earth. I did try to relate it to what you wanted to hear about life's origins but, as you see, there is little or no connection. Also, the book was written thirteen yeas ago. A lot has come along since there.

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Yes, I understand. It was with that understanding that I gave the 1 through 4 summary of the possibilities and it was with that understanding that I gave you my reasons for not being inclined to speculate about far-flung possibilities: stating them in a list is not speculating about their truth-value.

 

Now, I hope, you understand my position and reluctance to participate in speculation that requires monumental assumptions about tentative and tenuous evidence.

 

If you wish to address such things as the profound implication of finding our solar system devoid of any life off-earth, then I will oblige.

 

Thanks.

 

You should be informed that "exchemist" is on my ignore list.

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...

Claim: 2+2=4

Rebuttal: You're not a Lord, therefore you're wrong.

...

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...

In my world, everyone is entitled to a theory so long as it adds up as well as does 2+2. [emoticon omitted for clarity] What we know is that there followed tranquility. But the mystery still exists. The authors say "Great rewards lie in store for those who can resolve this mystery.

...

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Let us begin...to "separate the men from the boys." (I will post, later, some detail on the error of "you are what you eat" so-called truism.)

 

The first thing is that I change the "2+2" part of the "claim"; let's allow "2 + 2" to be substituted with "1 + 3" (or 3+1).

 

The reason is to remove the irrelevant (and erroneous) impression of symmetry between the operands. The putative logic that is associated with the appeal to "2 + 2", must apply generally--no one would assert that the logic applies only for the natural number '2'; therefore, we can use x + y = z, where all are of the set Natural Numbers (I don't use "Whole Numbers" as to not drag in zero, though some include zero in that set--not for this topic.)

 

I will pause here to determine whether anyone disputes the above--or would like to "anticipate" where I am going with this treatment of "2+2", the logic of, (or "2+2=4, if you like).

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Scherado, please keep in mind that I was reporting what the book says, not what I say.  That was the purpose of the post - to tell what the authors had to say about - well, the origin of water on Earth.  I did try to relate it to what you wanted to hear about life's origins but, as you see, there is little or no connection.  Also, the book was written thirteen yeas ago.  A  lot has come along since there.

 

Exchemist, are you still wanting to hear what the book says about the origins of water on Earth?  I do want to re-read that part.  I know there is a lot of speculation about it but these authors are only relating known facts as facts and labeling the guesses as unproven.

Yes Hazelm, very much so. I find it hard to follow the twists and turns of the water theory these days.

 

As a separate issue, the scenarios for the origin of life also greatly interest me, as someone with a chemistry background. I was very taken with a lecture someone on another forum pointed me, to in which a hypothesis was offered for the "handedness" (what chemists call "chirality") in biochemical molecules: things like the difference in metabolism of L and D forms of sugars for instance. I may have mentioned this before, but can't remember. I notice you mention the possibility of biochemical building blocks arriving with comets. That seems to make a lot of sense, given that low temperatures are what you want, in order to preserve long and complex molecules once they have formed. But if that is what happened I would then want to know how these molecules got synthesised on these comets. 

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Good morning, exchemist.  Good to hear from you.  I thought I quoted something from the book about what the comets brought in but I'm not seeing it.  I'll run that down and either find it or quote it next.  As I remember, it said they brought the  lesser elements that are needed for life to form.  They also brought water from - I think - the icy crystals of the tails.  Only the authors posited that perhaps the temperatures were too low to allow for life.  I was not too sure of that since the temperature would have risen.  Maybe they meant too cold to carry any life forms on the travels of the comet.  We shall see.

 

I do not understand the handedness (chiralty) story but I'll check on that later.  It suddenly occurs to me that I've never taken time to sort out the difference in origins (or formations) of comets, meteors and asteroids.  I am sure I've read that in the far distant dark past.  Better do so again.  There seems to be a grand difference in what a comet does compared to the other two.  Is it perhaps a wandering star - a star that never got caught up in (or escaped from) a galaxy? 

 

Well, I'll work on that later.  Meanwhile, back to the chapter and water. 

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All right.  For what it is worth, here is a complete quote about what comets brought.

 

"In addition to their snow, grit, and rocks rich in minerals and metals, the comets that bombarded Earth during the first few hundred million years contained many different types of small molecules such as methane, ammonia, methyl alcohol, hydrogen, cyanide, and  formaldehyde.  These molecules, along with water, carbon monoxide and carbon dioxide, provide raw materials for life.  They all consist of hydrogen, carbon, nitrogen and oxygen and all represent the first steps in building complex molecules."

 

Exchemist, when they say "they all consist of hydrogen, carbon, nitrogen and oxygen", do they mean by "they" the small molecules?  Or do they mean all the comets, asteroids and meteors?  Pronounitis is a horrible disease. :-)

 

I shall return.

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All right.  For what it is worth, here is a complete quote about what comets brought.

 

"In addition to their snow, grit, and rocks rich in minerals and metals, the comets that bombarded Earth during the first few hundred million years contained many different types of small molecules such as methane, ammonia, methyl alcohol, hydrogen, cyanide, and  formaldehyde.  These molecules, along with water, carbon monoxide and carbon dioxide, provide raw materials for life.  They all consist of hydrogen, carbon, nitrogen and oxygen and all represent the first steps in building complex molecules."

 

Exchemist, when they say "they all consist of hydrogen, carbon, nitrogen and oxygen", do they mean by "they" the small molecules?  Or do they mean all the comets, asteroids and meteors?  Pronounitis is a horrible disease. :-)

 

I shall return.

 

I'll reply for @exchemist: from a grammatical point of view, the last subject in the previous sentence was "These molecules". One must assume that the "they all consist" refers to "these molecules" because there is no reason to suspect a change of subject to "meteors".

 

If he had meant "meteors" it would be extremely sloppy writing - anacoluthon.

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I'll reply for @exchemist: from a grammatical point of view, the last subject in the previous sentence was "These molecules". One must assume that the "they all consist" refers to "these molecules" because there is no reason to suspect a change of subject to "meteors".

 

If he had meant "meteors" it would be extremely sloppy writing - anacoluthon.

Yes that makes sense scientifically too. Molecules containing H, C, N and O could enable carbohydrates and proteins to be made. However one would also need Phosphorus (P) in order to synthesise RNA or DNA.   

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Early scientific discussions theorized about the interaction of simple molecules, concentrated in pools or tide ponds created more complex molecules.  Today's scientists turn to laboratory experiments to learn exactly what separates inanimate matter from animate and, hopefully figure out how the barrier between the two was breached.  

 

After quoting Darwin about his idea of the "warm little pond", they tell of Stanley Miller's experiment in 1953.  S. Miller and Harold Urey set out to duplicate the "conditions within a simplified and hypothetical pool of water on Earth.  They partly filled a flask with water topped with a gaeous mixture of water vapor, hydrogen, ammonia and methane.  They heated the water, vaporizing some of the contents and sending them along a glass tube to another flask where they simulated  the effect of lightning.  After a few days of repetitions, they found original flask to be rich in "organic gunk", a compound of numerous complex molecules including two different types of sugar along with two of the simplest amino acids, alanine and guanine.

 

There is a lot of detail here that does not bear copying.  I am almost certain you can find the entire story online, giving you more details. Talking about amino acids, the authors end up with "amino acids have also been found  in some of the oldest and least altered meteorites believed to have remained unchanged for nearly the entire 4.6 billion year history of our solar system.

 

But, they say, we can not yet say how these molecules, all primed for life,  generate life itself.  After examining the Bacteria and Eucarya and having their hopes raised, they come to the Extremophiles (Archaea) and what they find causes the entire theory to fall apart.

 

There is so much more and I've wandered from my aim of how did water appeared on Earth.  Well, not really wandered - just not reached it.  Here I come to their question:  "How did Earth acquire its oceans of water?"  Next "chapter" after lunch.

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Good morning, exchemist.  Good to hear from you.  I thought I quoted something from the book about what the comets brought in but I'm not seeing it.  I'll run that down and either find it or quote it next.  As I remember, it said they brought the  lesser elements that are needed for life to form.  They also brought water from - I think - the icy crystals of the tails.  Only the authors posited that perhaps the temperatures were too low to allow for life.  I was not too sure of that since the temperature would have risen.  Maybe they meant too cold to carry any life forms on the travels of the comet.  We shall see.

 

I do not understand the handedness (chiralty) story but I'll check on that later.  It suddenly occurs to me that I've never taken time to sort out the difference in origins (or formations) of comets, meteors and asteroids.  I am sure I've read that in the far distant dark past.  Better do so again.  There seems to be a grand difference in what a comet does compared to the other two.  Is it perhaps a wandering star - a star that never got caught up in (or escaped from) a galaxy? 

 

Well, I'll work on that later.  Meanwhile, back to the chapter and water. 

Yes the temperatures on comets would be too low for life to go on, but what we are talking about is the slow synthesis and transport to Earth of small building blocks (CH4, NH3, CH3OH, HCN, HCHO),  from which more complex - and ultimately living - structures formed on Earth, where it is warmer.

 

The chirality story is one I like. An example of chirality is glucose. There are carbon atoms in this molecule which are bonded to 4 different groups of atoms. Whenever you get this, you have 2 ways of arranging the 4 groups, which are mirror images of each other*. With glucose they are called L (for laevo = left-handed ) and D (for dextro= right- handed). The whole of terrestrial biology uses the D form only, even though the L form is chemically identical, apart from this issue of handedness. Same atoms, same bonding, same energy, even the 3D shape is the same, apart from one being a mirror image of the other.  If you eat L glucose it tastes the same, but your body cannot metabolise it - in fact it was once proposed as a calorie-free sweetener! This selective use of only one of a pair of mirror-image, "handed" molecules goes for other molecules in biochemistry too. How could it have arisen that only one form was arbitrarily selected for biology, given that all non-biological chemical reactions produce equal quantities of both L and D forms?  

 

There are certain crystalline minerals that are similarly handed on different faces of the crystal. Calcite is one. It is found that handed bio-molecules adsorb onto handed crystal surfaces with different bonding strengths, according to whether they are L or D forms.  This raises the intriguing notion that maybe differential adsorption onto mineral crystals may have selected for one form at the expense of the other. More here: https://www.scientificamerican.com/article/minerals-may-explain-life/ 

 

* Just for Dr Krettin, who likes his Greek, these mirror image pairs are called "enantiomers", and are a particular sort of "isomer".   :)

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Splenda?  When Splenda first came on the market, we were told it is a sugar molecule formed "backward".  Thanks for the explanation.

I had to look this up but no, Splenda is something else, primarily something called sucralose: https://en.wikipedia.org/wiki/Splenda 

 

From what I gather, production of L glucose was far too expensive to be commercial. 

 

The thing is that you'd have to synthesise it chemically, from scratch! You can't get it from organic sources, obviously. And when you did this, you'd get a "racemic" mixture (equal amounts of L and D), and then you'd have quite a job separating the L from the D.   All very expensive. 

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All right.  "How did Earth acquire its oceans of water?"   But first, there is a why.  Why does Earth have an abundant supply of water when it most surely received as much pummeling as did the moon and Venus?  The authors do not put it as "why" but that is the question they are answering before starting on Earth.  Venus is a fast study - temperature and greenhouse effect.  But, the moon?  One, fast evaporation due to lesser gravity.  Two, water deep in polar craters.  So, the moon may have more water than we suspect.

 

Earth also experiences a greenhouse effect but at much lower temperatures.  If ever Earth experiences higher temperatures and harsh greenhouse effect, we cna go the way of Venus.  Then there is Mars, which - if any other planet in our soar system ever had water - was once rich in the liquid.  Now it is bone dry.  As the authors say - looking at these other nearby bodies, "It forces us to look at Earth anew and wonder how fragile our surface supplly of liquid water may turn out to be.

 

Aside:  someone here on this forum commented that Earth has more water than it should have.  I do not remember who is was.  Turtle?  I'm not sure.  But I wonder if this is what she was referring to.

 

Life requires sacs of liquid.  But must that liquid be water?  "Water, which consists of molecules made from two of the most abundant elements in the cosmos exists in comets, in meteoroids, and in most of the sun's planets and their moons.  On the other hand, water in its liquid forum exists only on Earth and beneath the icy surface of Jupiter's largest moon Europa..."  (the latter not yet verified).

 

"Earth grew by accreting large numbers of solid particles and ... and through incessant impacts of mineral-rich asteroids and  water-rich comets. ... The early impact rate of comets may have been sufficiently large to have brought us the water in all our oceans.  Uncertainties (and controversies) surround this hypothesis. Add the above to the water vapor spewn from active volcanoes and we have plenty of water.

 

So, in several places, the authors seem to conclude that the most likely source of all our water is from comets.  They then go into how we are searching for planets that qualify to have life.  They point out that some of the standards for qualification do not necessarily hold up under closer inspection.

 

I'll not get back into "life" as it goes on and on.  If anyone needs to hear all of the authors' points, you'd want to get the book.  It is easy reading, almost too easy for someone educated in the life sciences.  As I think I said at the start, these authors write for what I call the "science-challenged" lay person.  They explain things quite simply.  But it is a good start.  Basically, the latest (and unproven) theory is that nature managed to convert inanimate materials into animate materials.  And therein lies our mystery. 

 

My comment:  Why not?  I remember when we children used up all of our parents' baking soda pouring vinegar onto it.  If an inanimate material can do that, what else can it do?  Or, would you prefer invading Martian refugees escaping a dry planet?  Not a bad idea.  :-)

 

Me?  I have reservations on the next ship to Pern.  :roll:

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I had to look this up but no, Splenda is something else, primarily something called sucralose: https://en.wikipedia.org/wiki/Splenda 

 

From what I gather, production of L glucose was far too expensive to be commercial. 

 

The thing is that you'd have to synthesise it chemically, from scratch! You can't get it from organic sources, obviously. And when you did this, you'd get a "racemic" mixture (equal amounts of L and D), and then you'd have quite a job separating the L from the D.   All very expensive. 

Thanks. 

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All right.  "How did Earth acquire its oceans of water?"   But first, there is a why.  Why does Earth have an abundant supply of water when it most surely received as much pummeling as did the moon and Venus?  The authors do not put it as "why" but that is the question they are answering before starting on Earth.  Venus is a fast study - temperature and greenhouse effect.  But, the moon?  One, fast evaporation due to lesser gravity.  Two, water deep in polar craters.  So, the moon may have more water than we suspect.

 

Earth also experiences a greenhouse effect but at much lower temperatures.  If ever Earth experiences higher temperatures and harsh greenhouse effect, we cna go the way of Venus.  Then there is Mars, which - if any other planet in our soar system ever had water - was once rich in the liquid.  Now it is bone dry.  As the authors say - looking at these other nearby bodies, "It forces us to look at Earth anew and wonder how fragile our surface supplly of liquid water may turn out to be.

 

Aside:  someone here on this forum commented that Earth has more water than it should have.  I do not remember who is was.  Turtle?  I'm not sure.  But I wonder if this is what she was referring to.

 

Life requires sacs of liquid.  But must that liquid be water?  "Water, which consists of molecules made from two of the most abundant elements in the cosmos exists in comets, in meteoroids, and in most of the sun's planets and their moons.  On the other hand, water in its liquid forum exists only on Earth and beneath the icy surface of Jupiter's largest moon Europa..."  (the latter not yet verified).

 

"Earth grew by accreting large numbers of solid particles and ... and through incessant impacts of mineral-rich asteroids and  water-rich comets. ... The early impact rate of comets may have been sufficiently large to have brought us the water in all our oceans.  Uncertainties (and controversies) surround this hypothesis. Add the above to the water vapor spewn from active volcanoes and we have plenty of water.

 

So, in several places, the authors seem to conclude that the most likely source of all our water is from comets.  They then go into how we are searching for planets that qualify to have life.  They point out that some of the standards for qualification do not necessarily hold up under closer inspection.

 

I'll not get back into "life" as it goes on and on.  If anyone needs to hear all of the authors' points, you'd want to get the book.  It is easy reading, almost too easy for someone educated in the life sciences.  As I think I said at the start, these authors write for what I call the "science-challenged" lay person.  They explain things quite simply.  But it is a good start.  Basically, the latest (and unproven) theory is that nature managed to convert inanimate materials into animate materials.  And therein lies our mystery. 

 

My comment:  Why not?  I remember when we children used up all of our parents' baking soda pouring vinegar onto it.  If an inanimate material can do that, what else can it do?  Or, would you prefer invading Martian refugees escaping a dry planet?  Not a bad idea.  :-)

 

Me?  I have reservations on the next ship to Pern.  :roll:

OK so they think the water on the primordial Earth came from comets. But it seems this is not yet definitively settled: http://science.sciencemag.org/content/350/6262/795 This article suggest water was always part of the Earth's makeup from the start. 

 

So it rather looks as if we don't really know yet, though there are several rival hypotheses.

 

Regarding other solvents for life, I've always thought it would be fun if life could have evolved elsewhere using liquid methane, as on Jupiter's moon Titan. But I'm sure a polar solvent would be more versatile. I've always rather fancied liquid ammonia. Unfortunately there does not seem so far to be any evidence of that in our solar system, though it might happen elsewhere I suppose. 

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