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Carl_12
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Age of the Moon
      #5918163 - 06/13/13 02:51 AM

While my internet access was sporadic at best, the thread I started "What do you guys make of this?" was locked. On the one hand, that's a shame, but on the other, the timing was good.

Looking at the Moon at 4m and 2m resolution changes one's perspective - everything is rounded. The sharpness we perceive through a telescope, or even from orbiters at lower resolution, is an illusion of scale. Get closer, and you see just how universally eroded the object is. This makes it nigh on impossible to derive conclusions about formation.

Which leads me to a new thought - the Moon is likely older than we think.

My reasoning as is follows. There are no materials subject to condensation that would preferentially condense or precipitate into larger objects before smaller ones. Take water for instance, it condenses first into a mist, before the tiny droplets aggregate into larger drops.

So if we take a cloud of dust and gas (a post Population I situation you might say, if you see what I mean), then the nebula would begin condensing into planetoids first, before they aggregate and collapse into ever larger objects, ultimately forming a star. The new star would then form its own protoplanetary disk, and new planetoids may form within it. The point being, that some of the planetary objects orbiting the star are likely to be older than those created in the disk.

The interaction between the old and the new planets is likely to be violent, resulting in a period of heavy bombardment before the "dust settles" and we have a solar system with relatively stable orbits and clearer interplanetary space.

Looking at the battered and eroded surface of the Moon, it would seem to be a good candidate for one of the older objects. And so perhaps would Mercury. And other objects, Kuiper belt comes to mind. Comets would be almost certainly of the old type, the remnant of the very initial condensation of the nebula much before the star was born.

Thoughts, anyone?

And a polite note to the mods, please don't lock threads if the discussion is civil (as the previous one was, even if argumentative). Thank you!


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David Knisely
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Re: Age of the Moon new [Re: Carl_12]
      #5918206 - 06/13/13 04:05 AM

The oldest lunar rocks have been radiometrically dated at around 4.5 billion years. There are various theories about the moon's formation, but the moon probably isn't a great deal older than that figure. Clear skies to you.

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brianb11213
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Re: Age of the Moon new [Re: David Knisely]
      #5918349 - 06/13/13 08:37 AM

The bombardment age of an object's surface is not necessarily the same as the age of the object ... all solar system objects are more or less the same age, but erosion has wiped the older features off the surface of many of them. Only partially so in the case of Earth's moon (lava flows filling in mare basins) but completely in the case of the Earth itself ... atmosphere, ocean and tectonics have recycled the Earth's original surface many times over.

Yet current theories of lunar origin have Earth and Moon essentially created at the same instant from the collision of two protoplanets. Well it took a hundred years or so for the moon to coalesce from the material thrown into orbit by the collision.


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THEPLOUGH
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Re: Age of the Moon new [Re: brianb11213]
      #5919453 - 06/13/13 07:56 PM

Quote:

Yet current theories of lunar origin have Earth and Moon essentially created at the same instant from the collision of two protoplanets. Well it took a hundred years or so for the moon to coalesce from the material thrown into orbit by the collision.






Yes, the BBC had a documentary on this very subject...


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Carl_12
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Re: Age of the Moon new [Re: THEPLOUGH]
      #5921832 - 06/15/13 08:50 AM

Dear friends, the proposed theories are lacking in logical rigour.

1. RADIOACTIVE DATING
The dating can only measure the age of the material, at best, not the age of the lunar formation. (This is discounting the fact that the lunar surface is heavily contaminated.) If we establish the rocks are 4 billion years old, then all we know is that the material is that old, the Moon could be a lot younger. So what is of interest here is not so much the absolute age, but the age in relation to the age of the other planets. Which object is younger, which is older? If we assume all objects were created in the same nebula, all will be made of materials of roughly the same age. Dating of the rocks will not help us understand when the planets formed.

2. COLLISION THEORY
This theory of Earth-Moon origin is farcically implausible. Three main reasons for that.

Firstly, if an object struck the Earth with sufficient force to break off quantities of material the size of the Moon, that broken-off material would be scattered about as a collection of smaller parts, strewn in a number of directions. You can posit a far-fetched posibility that the mess would then somehow come together to form the Moon, but if this be the case, it is a more elegant and likely supposition to say that the mess existed and agglomerated coincidentally, without the necessity of collision. In other words, the collision theory annihilates itself by virtue of complexifying a simpler, more likely process.

Secondly, if we suppose that somehow the collision did result in two sufficiently distinct objects to survive it intact, the Earth and the Moon, the force of the collision would mean that the two would not remain in the same orbit. The Moon would have been knocked outta dodge!

Thirdly, if in our generous tolerance of illogical thinking we for a moment suppose it is possible for the Moon to remain in the same orbit as the Earth, that begs the question where the collisionary object has gone. If the force of the collision was low enough that the Moon could break off without being propelled out of orbit, that must inversely mean that the third object, the collider, would remain in the same orbit too. You can't have your cake and eat it. Either there was enough force for all participants to scatter, or there wasn't, and the three would remain together. Where's the third?


It is quite amazing that in our modern, enlightened age we must deal with such "epicycles". All because of a central falsehood, the idea that ALL planetary objects must have been created in the stellar protoplanetary disk.

Yet, consider this: the Sun contains more than 5000 Earth masses of heavier materials than helium and hydrogen. That's a lot of Earths to fall together into the forming star. What makes anyone think that ALL of the pre-existing proto-planetoids would have collapsed into the star? Surely it is stating the obvious that planets would have formed well before the star was formed, indeed, planets are a necessary step toward the stellar creation. With 5000 Earth masses gone to the star, how many Earth masses would have survived? The answer of our present "science" is NIL.

If that passes for science, we're barely out of the cave. Neanderthal logic, you might call it.


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David Knisely
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Re: Age of the Moon new [Re: Carl_12]
      #5922360 - 06/15/13 02:09 PM

1. It is "radiometric" dating, not radioactive dating, and is used to measure the last time that the rock being dated was either melted or disturbed sufficiently to rehomogenize its radioactive elements. Some study of the subject might help a little here. The moon is not exactly "heavily contaminated. Different types of lunar rocks have been dated to different ages. The rocks from the lunar maria for example date back only around 3 billion years or so in age, while those from the older lunar highlands are past four billion years old.

As for the formation methods, a lower velocity impact of a large planetoid on a primordial Earth during the late phases of planetary accretion would blow a lot of material into space, but some would fall back and some would either escape completely or probably achieve a rather irregular orbit around the Earth, potentially allowing it to coalesce via its own gravity into the moon. Computer simulations have shown this method of formation to work, although again, it isn't the only valid theory of lunar formation. Quite simply, we don't know exactly how the moon was formed. We do know, however, that it is quite old. This is not based on "neanderthal logic", but decent scientific theory. Clear skies to you.


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UND_astrophysics
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Re: Age of the Moon new [Re: Carl_12]
      #5922382 - 06/15/13 02:24 PM

I have never heard of "radioactive dating"
But....you are proposing popular mechanics pseudoscience. Observing craters in ordering of relative time is called the law of superposition. The moon has no atmosphere to burn up a lot of the material before it impacts. hence the large amount of visible cratering. Of course The moon is going to look older if your do not take that into account. And on top of that the Moon lacks geological erosional processes from an atmosphere. The younger darker areas are newer magmatic flow. the discrepancies of relative age are determined by crater counting. Take a Look at Venus. It has very few, evenly scattered o large craters because it's atmosphere only allows the largest impactors (after it's crustal resurfacing .5 GYA). It is very simple. There is no "big mystery" or conspiracy.


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Greyhaven
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Re: Age of the Moon new [Re: Carl_12]
      #5922527 - 06/15/13 04:45 PM

"Looking at the Moon at 4m and 2m resolution changes one's perspective - everything is rounded."

My guess is Moon dust from tiny impacts. Slowly building up evenly on all surfaces.
My logic, my coffee table, by rubbing my finger across its' surface I can tell it is made of wood not suede.

"My reasoning as is follows. There are no materials subject to condensation that would preferentially condense or precipitate into larger objects before smaller ones. Take water for instance, it condenses first into a mist, before the tiny droplets aggregate into larger drops."

My reasoning, Moon rock samples show a remarkable likeness to the rocks making up Earth's crust and the Moon does not have a molten iron core. This lends it self to the collision theory being that the Earth would have melded cores with that of the other body,ejecting crustal material into space to condense into the Moon.

"The interaction between the old and the new planets is likely to be violent, resulting in a period of heavy bombardment before the "dust settles" and we have a solar system with relatively stable orbits and clearer interplanetary space."

See you are introducing the "dust settling" into your own theory as to the softness of the details on the Moon.I think micro meteoroids could be a more likely source of much of this material. The Moons composition, the mathematical plausibility in explaining current physical relationships of the Earth Moon system, combined seem to at least meet and explain the results we observe today.

I do not expect you to take my thoughts as a serious scientific rebuttal to your reasoning of the age of the Moon. I hope you can understand why I must view yours' like wise.
I am not trained as an astronomer, but once met and spoke with John Dobson.
Be Well
Grey


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Carl_12
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Re: Age of the Moon new [Re: Greyhaven]
      #5922545 - 06/15/13 04:57 PM

A standard reference on radioactive or radiometric dating is "Radiogenic Isotope Geology" by Dickin, and it contains this most interesting paragraph:

"The first application of the common Pb)Pb dating technique was actually to meteorites rather than terrestrial rocks. In this study, Patterson (1956) calculated a Pb)Pb age of 4.55 " 0.07 Byr on a suite of three stony meteorites and two iron meteorites (Fig. 5.26). The least radiogenic of these samples was troilite (FeS) from the Canyon Diablo iron meteorite, which was responsible for Meteor Crater, Arizona. The U/Pb ratio measured on this sample (0.025) was so low that Patterson concluded that ‘no observable change in the isotopic composition of lead could have resulted from radioactive decay after the meteorite was formed’. Hence Canyon Diablo troilite represents the primordial Pb isotope composition of the solar system. This is an important benchmark for terrestrial Pb isotope evolution, just as the chondritic reservoir constrains terrestrial Nd isotope evolution."

http://www.onafarawayday.com/Radiogenic/

What this is saying is that a part of the meteorite is so old that it cannot be dated. Hence the "primordial" label. The unacknowledged implication is that planetary matter condensed before solar system formation. And where there are meteorites, there will be, given enough of the material, comets and asteroids, and ultimately, planets.

Is there anyone here willing to engage with this assertion that planets must by the very nature of condensation and accretion precede the formation of the star? Anyone have anything pertinent to say about that?


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UND_astrophysics
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Re: Age of the Moon new [Re: Carl_12]
      #5922580 - 06/15/13 05:26 PM

Given the fact that everything is ultimately an accretion of primordial hydrogen partially recycled, and elements have been recycled several times, and will continue to be recycled until the universe is only filled with heavy elements and no more star formation will occur, what is there to engage? What you just cited does not support your assertion. The fact that the rocky planets are near Sol, and the lighter gas planets are all in the outer part of the solar system tends to prove that the materials were sorted by the Sun, Lighter elements were blow outward farther than the silicates. which then accreted. If what you are asserting were true, we would not have sorted developed planetary compositions, The fact that we can directly observe proplyds tends to support it. You probably should take a few classes in planetary geology, that might help you understand things a little better, because you seem to be jumping from a lack of basic understanding to a research paper that has little to do with what you are asserting.

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Carl_12
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Re: Age of the Moon new [Re: UND_astrophysics]
      #5923323 - 06/16/13 07:21 AM

So you think a molecular cloud would condense into a larger object before smaller ones? That's like saying a hailstone will form before mist... Insanity!

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UND_astrophysics
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Re: Age of the Moon new [Re: Carl_12]
      #5923344 - 06/16/13 08:06 AM

What does that have to do with anything? You claimed the Sol system was capable of forming planets independent of Sol. You are talking apples and oranges now, which is why I have to bite my tongue and remind myself that this is simply an amateur astronomy site, and sometimes I should expect nothing more from certain users. You can believe anything you want. If you wish, you can also believe the moon is made of green cheese, And believe the planets in our solar system formed independent of Sol, That is for you I guess a good thing about the freedom of the internet. If you do not want to pay for a real education, you can always look up any source you want, and create your own version of physics, right?

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UND_astrophysics
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Re: Age of the Moon new [Re: Carl_12]
      #5923352 - 06/16/13 08:18 AM

Quote:

So you think a molecular cloud would condense into a larger object before smaller ones? That's like saying a hailstone will form before mist... Insanity!




Now you are comparing humidity, atmospheric pressure gradient and temperature with stellar formation? I would have to say that is not just insanity, more like ignorance.


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azure1961p
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Re: Age of the Moon new [Re: UND_astrophysics]
      #5923418 - 06/16/13 09:05 AM

I'm starting to think Carl IS 12.

Pete


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Carl_12
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Re: Age of the Moon new [Re: azure1961p]
      #5923556 - 06/16/13 10:59 AM

Guys, would you kindly refrain from sarcastic personal attacks and actually address the question?

To repeat, does a molecular cloud preferentially condense into a larger object before smaller ones? There is only one answer to this... Comparison with water vapour is valid, the process of condensation is fundamentally the same.

If you can't have a reasoned discussion, please don't bother replying. It doesn't look good on anyone to be having the kind of childish, flippant retorts that I'm receiving here. Thanks for your understanding.


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Greyhaven
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Re: Age of the Moon new [Re: Carl_12]
      #5923786 - 06/16/13 01:26 PM

No
Be Well
Grey


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David Knisely
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Re: Age of the Moon new [Re: Carl_12]
      #5923857 - 06/16/13 02:18 PM

Quote:

Guys, would you kindly refrain from sarcastic personal attacks and actually address the question?

To repeat, does a molecular cloud preferentially condense into a larger object before smaller ones? There is only one answer to this... Comparison with water vapour is valid, the process of condensation is fundamentally the same.

If you can't have a reasoned discussion, please don't bother replying. It doesn't look good on anyone to be having the kind of childish, flippant retorts that I'm receiving here. Thanks for your understanding.




The problem is that you are posting this on a forum which is more commonly used for observing reports or images of the moon, and not necessarily for extensive speculation on its origin, the origin of the solar system, its age, or radiometric dating techniques. I didn't give you any "childish" remarks. I answered your question. As for your questions on the Uranium/Lead dating technique, the rock (the Canyon Diablo sample) is not "too old to date", but represents something pretty close to a limit on that particular dating technique. There are other dating techniques that can go farther back in time, which can be more fully understood with a little additional study on radiometric dating techniques. Again, this particular forum may or may not be the best place for your "debate" on the age of the moon or its mode of creation, which may be one reason you are getting a little "flack" from some people. Clear skies to you.


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UND_astrophysics
sage


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Re: Age of the Moon new [Re: Carl_12]
      #5923937 - 06/16/13 03:06 PM

Quote:

Comparison with water vapour is valid, the process of condensation is fundamentally the same.




Condensation is a phase change, a function of temperature, pressure and relative humidity- and not remotely related to accretion of a GMC.. In all politeness, you need some physics classes.
-
Clear skies.


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Carl_12
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Re: Age of the Moon new [Re: UND_astrophysics]
      #5924139 - 06/16/13 05:24 PM

David, if this isn't the right place for this thread, it will die off naturally. Let's just see how it goes.

UND_astrophysics, my point applies to accretion as well as to condensation. I focused on one word to try and reduce the problem to the bare minimum in the hope the point I'm making will actually be discussed instead of serving as a platform for pointing out my ignorance.

But you can look at all of the processes involved and it amounts to the same thing: the growth process is from smaller object to larger. Condensation, accretion, clumping, agglomeration, whatever.

It must follow therefore - and this is backed by the simplest of observations - that a large object will grow from smaller ones. In a post Population I dust and gas nebula giving birth to stars, there would be a multitude of such smaller objects, variously growing into larger ones. Most will not grow to the size required for stellar ignition, but some may. The point being that as the star is about to be born, there are many failed candidates in the cloud, in other words, planetary objects of various sizes.

In terms of physics, I'm not stating anything controversial. What may be controversial is the implication, that planets can predate stars. But that's not my fault, it's the fault of those who seem to suppose a star can be born in isolation, from a "pure" cloud that otherwise is not creating anything. In post Population I times, this is physically impossible.


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THEPLOUGH
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Re: Age of the Moon new [Re: Carl_12]
      #5924311 - 06/16/13 07:48 PM

This forum is for MOON related topics... Your question regarding "The age of the Moon" as has far as I can tell been answered, please move on...

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photonovore
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Re: Age of the Moon new [Re: THEPLOUGH]
      #5924587 - 06/16/13 10:52 PM

Surely the origin of the Moon is a relevant topic in this forum.

The hypothesis i see being touted by carl12 is the lunar capture theory (an older hypothesis from the pre-apollo era), where a (possibily pre-solar system formation) object wanders/pre-exists in/into the early/proto solar system and is eventually "captured" by Earth. Ok.

Why this is has been discounted/dismissed as a valid hypothesis:
1) Moon has been physically dated radiometrically at no more than ~4.4 by. (This is a date of *accretion*--crust solidification--which post-dates that of Earth by ~200my)
2) The chemical composition of the Earth/Moon does not match what would be expected if these were physically unrelated bodies. (ex: relative abundance of titanium-50 and titanium-47 in Moon rocks; Zhang 2012--match to Earth w/in 4ppm making a related origin highly probable)
3) Extreme improbability of capture due to angular momentum limitations, lacking a third body of sufficient (substantial) mass in the equation--for which there is no evidence.
4) Moon is an iron depleted body (core), which is a inconsistency for a body formed independently via currently understood processes.
5) Orbital inclination of Moon relative to Earth is not accounted for (among other orbital parameters inconsistent with capture theory)

There are actually *two* theories that are *currently* in competition for the title "the most probable" re; lunar formation--
1) Impact, still the preferred hypothesis
a)2x mars mass impactor (Canup, 2012)
b) smaller higher velocity impactor, coupled with fast-spinning proto earth (Cuk/Stewart 2012)
c) and other variations

2) Fission is being re-examined; if the spin rate of the proto earth is not sufficiently constrained (as heretofore, making this unlikely due to angular momentum insufficiency issues) then this theory can gain probability.(Zhang)
----------------------------------

The problem with 'popular' science education (such as documentaries on tv, many lay books etc) is that (currently leading) hypotheses are often presented very positively (as established fact) when they are anything but. What they actually represent are statements of relative higher probability based wholly upon _current data and understanding_ of that data. That's all. The field of lunar genesis is actually still relatively active...


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Mare Nectaris
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Re: Age of the Moon new [Re: photonovore]
      #5925031 - 06/17/13 08:40 AM

Quote:


There are actually *two* theories that are *currently* in competition for the title "the most probable" re; lunar formation--
1) Impact, still the preferred hypothesis
a)2x mars mass impactor (Canup, 2012)
b) smaller higher velocity impactor, coupled with fast-spinning proto earth (Cuk/Stewart 2012)
c) and other variations

2) Fission is being re-examined; if the spin rate of the proto earth is not sufficiently constrained (as heretofore, making this unlikely due to angular momentum insufficiency issues) then this theory can gain probability.(Zhang)




Hi all,
Sarah T. Stewart-Mukhopadhyay from the Department of Earth and Planetary Science, Harvard University, is reviewing as a co-writer the article Mardi mentioned above (Cuk & Stewart: Making the Moon from a fast-spinning Earth...).

Be well all!


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Carl_12
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Re: Age of the Moon new [Re: Mare Nectaris]
      #5925613 - 06/17/13 01:58 PM

Thank you, photonovore, much appreciated. Though you must admit you're being very selective, leaving out all the acknowledged problems with the impact theory.

To say that pre-existing planetaries would be likely in the Solar System isn't the same as touting the capture theory. Early, perhaps smaller, versions of the Earth and Moon could have both formed before the Solar System, and then experienced additional growth in the newly energized protoplanetary disk.

In fact, the impact theory was considered too improbable to be taken seriously before the Apollo rocks were dated. The dating of the rocks hasn't made the event any more probable, it merely makes the theory more coherent.

I would urge those who are seeking to plug holes in the impact theory to stop running round the epicycles and to consider a smaller, more probable impact, with a smaller Moon already in place. The impact is then a re-surfacing event rather than whole creation, all the more probable for it. The relatively small core of the Moon would support this idea, and many of the present issues with the impact theory would disappear.


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David Knisely
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Re: Age of the Moon new [Re: Carl_12]
      #5925628 - 06/17/13 02:08 PM

Quote:

Thank you, photonovore, much appreciated. Though you must admit you're being very selective, leaving out all the acknowledged problems with the impact theory.

To say that pre-existing planetaries would be likely in the Solar System isn't the same as touting the capture theory. Early, perhaps smaller, versions of the Earth and Moon could have both formed before the Solar System, and then experienced additional growth in the newly energized protoplanetary disk.

In fact, the impact theory was considered too improbable to be taken seriously before the Apollo rocks were dated. The dating of the rocks hasn't made the event any more probable, it merely makes the theory more coherent.

I would urge those who are seeking to plug holes in the impact theory to stop running round the epicycles and to consider a smaller, more probable impact, with a smaller Moon already in place. The impact is then a re-surfacing event rather than whole creation, all the more probable for it. The relatively small core of the Moon would support this idea, and many of the present issues with the impact theory would disappear.




Mardi isn't being selective. All of the theories of the moon's origin have their problems, but given the data currently available, the impactor idea does provide somewhat of an answer to some of the compositional similarities between Earth and moon rocks. Dynamically, it has also been shown to be possible using extensive computer simulations, so it is better supported than it was years ago. The capture hypothesis is less likely dynamically, but is probably still in the running, although capturing the existing moon into Earth orbit via an impact is somewhat less likely than something just impacting the Earth and creating material which would eventually collect together to form it in the first place. It would be better if you didn't accuse people of "running around epicycles" and just stick with the actual facts of each theory. That way, you would be less likely to ruffle any feathers here. Clear skies to you.


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UND_astrophysics
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Re: Age of the Moon new [Re: Carl_12]
      #5926130 - 06/17/13 06:47 PM

Quote:


I would urge those who are seeking to plug holes in the impact theory to stop running round the epicycles and to consider a smaller, more probable impact, with a smaller Moon already in place.




But this is not your original assertion. You implied earlier that the moon was formed prior and independently of the original circumstellar disk, based on your thinking that because there were a lot of craters on the moon, it must be older than Sol system (an invalid conclusion)
I am totally lost as to where your reasoning is going, because your original premise is morphing from post to post into something else.


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Carl_12
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Re: Age of the Moon new [Re: UND_astrophysics]
      #5931141 - 06/20/13 11:39 AM

Quote:

Quote:


I would urge those who are seeking to plug holes in the impact theory to stop running round the epicycles and to consider a smaller, more probable impact, with a smaller Moon already in place.




But this is not your original assertion. You implied earlier that the moon was formed prior and independently of the original circumstellar disk, based on your thinking that because there were a lot of craters on the moon, it must be older than Sol system (an invalid conclusion)
I am totally lost as to where your reasoning is going, because your original premise is morphing from post to post into something else.




I've been quite consistent throughout, that planetary objects must pre-date the Sun by the very nature of the processes by which the Sun came to be.

That said, the state that those planetaries were in at the moment of stellar ignition is unknown to us, further evolution would be more than likely in the no doubt energetic solar nebula. Growth through impacts and resurfacing would be plausible.

I would also add that the age of the Moon's surface is far from proven as we haven't dated the very oldest structures, likely to be found in the ancient highlands on the other side. The margin of 200my difference from Earth, as reported in this thread, doesn't seem so great and could easily be overcome.

In short, I'm being flexible on the detail due to paucity of evidence, but consistent on the main point.


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photonovore
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Re: Age of the Moon new [Re: Carl_12]
      #5933978 - 06/22/13 12:28 AM

There isn't any reason why noritic anorthosites would vary significantly in age between farside/nearside highlands since the oldest of these plutonic rocks from either hemisphere would be reasonably expected to date to the same stage of the Moon's geologic history (crystallization stage of the lunar crust, which current data indicate to have been a global event).

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