Early Earth: 30 Million years to layering?

[yevaud]

Yes, and that's why I am trying this experiment. I feel that even if there are multiple threads in a Forum filled with nonsense, perhaps one or two, here and there, can be kept to some standards of truth, accuracy, and exactitude.<br /><br />I hope. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[vogon13]

'Dumbing down' a response to hit the target audience also leads inevitably to (hyper) corrective frenzies from the Intelligentsia Storm Troopers here, too.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[yevaud]

All too true.<br /><br />Well, it will be an interesting experiment, anyways. I would very much like to see it work.<br /><br />Have to get the Mods in on this, I think. I'd like these opccasional, "true hard science" threads I am proposing to be held to a higher standard of comportment and accuracy. For example, if someone enters the thread, and keeps trying to subvert it away from it's intented topic and discussion despite requests to go elsewhere, BAN THEM IMMEDIATELY.<br /><br />I think that's fair. There's an entire message board here. If they absolutely *must* meddle that way in the one or two hard science thread, they are proving beyond a shadow of a doubt that their intention for joining SDC is not debate, it's disruption. And they should go.<br /><br />After all, they get free reign almost everywhere. Why would this not be fair? <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[JonClarke]

This is a very murky subject. There is so little evidence on the very early earth and ideas are very model determined. I know very little about the subject. <br /><br />Also this press release has a degree of hype about it. <br />As others have said, it has been suspected for some time that accretion was very rapid.<br /><br />What does seem to be new, if I have read it correctly is the fact that differentiation of the earth was largely complete prior to the formation of the moon. I don't think this was as clear before.<br /><br />But it is a very iffy area, heavily dependent on models of isotopic fractionating during the process of planetary accretion and differentiation.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[yevaud]

<i>There is so little evidence on the very early earth and ideas are very model determined.</i><br /><br />This is very true. Although, of the two ideas here (Early Differentiation and Collision-Lunar formation theory), I'd say we know more about the Early Earth than Lunar Origins. <br /><br /><i>Also this press release has a degree of hype about it.</i><br /><br />Eh. SpaceDaily. Predictable, I suppose.<br /><br /><i>As others have said, it has been suspected for some time that accretion was very rapid.</i><br /><br />I imagine if you think of the Accretion phase in a thought-experiment, I can see why it might be possible. The density of material at that early age might have made our worst examples of gridlock look sparse. So a Protoplanet could have formed rapidly through sheer quantity of matter available to accrete.<br /><br /><i>What does seem to be new, if I have read it correctly is the fact that differentiation of the earth was largely complete prior to the formation of the moon. I don't think this was as clear before.</i><br /><br />That's true, it wasn't. It was always assumed (IIRC) that the impactor, of whatever nature, impacted the Earth when it was still very hot, but cool enough that a reasonable crust had formed. Now...not sure.<br /><br />As Saiph said, assuming that particular theory of Lunar Formation is correct, that is.<br /><br /><i>But it is a very iffy area, heavily dependent on models of isotopic fractionating during the process of planetary accretion and differentiation.</i><br /><br />The method of deriving this theory is where my education takes a Siesta. I gather you have some experience in this particular area, though(?). But yes, it is a rather thin thread.<br /> <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[bonzelite]

<font color="yellow"><br />What does seem to be new, if I have read it correctly is the fact that differentiation of the earth was largely complete prior to the formation of the moon. I don't think this was as clear before. </font><br /><br />right. and this only reinforces my prior belief the earth and it's moon formed concurrently, perhaps approximately simultaneously. <br /><br /><font color="yellow"><br />This is a very murky subject. There is so little evidence on the very early earth and ideas are very model determined. I know very little about the subject. </font><br /><br />yes. thank you. an opinion with scientific experience behind it. an opinion i share --the jury is way out. we don't know.

 

[JonClarke]

Well, on a subject like this I am not better than the next person with a general technical training and good general knowledge.<br /><br />I recall that one of the big problem with the early earth has to do with a global magma ocean and hafnium isotopes. I may have to check this, but the prediction is that if the earth was very hot, whether by accretion, radiogenic heating, or a giant impact, you would have got global melting and a particular hafnium isotope signature. This apparently is not seen, suggestion something is either wrong with the isotope model (which is based on stnadard chemistry) or there as no global melting. I may email Ross Taylor on this, he has done some of the fundamental work on this, and may have some light to shed.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>right. and this only reinforces my prior belief the earth and it's moon formed concurrently, perhaps approximately simultaneously.<p><hr /></p></p></blockquote><br /><br />Well, you won't be at all alone in that. Popular press aside, there isn't really a universal feeling as to how the Moon formed. The impactor theory is enjoying a large amount of popularity right now (I admit it does have a certain asthetic appeal to me), mainly due to some recent advances in computer models which showed it was more plausible than many had previously thought. But it's really not been shown to be anything more than plausible. Lots of scientists favor the idea that the Moon formed separately from the Earth.<br /><br />I can't wait for the new "Apollo on steroids" missions. <img src="/images/icons/wink.gif" /> We need more lunar data! More lunar crust samples! More seismology experiments! <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[centsworth_II]

<font color="yellow">"I can't wait for the new "Apollo on steroids" missions. We need more lunar data! More lunar crust samples! More seismology experiments!"</font><br /><br />Yeah! I love you're (and spaceter's) attitude! I'm discouraged by those who poo poo the notion of returning to the moon because the "ride" is not snazzy enough for them. It's about the science (stupid), not the ride. <div class="Discussion_UserSignature"> </div>

 

[bonzelite]

yes, calli, in my opinion, i don't see why core accretion theory prohibits the earth and it's moon from coalescing as individual bodies. that would be the absolute first thing i would assume, as it is very simple and rather understated. <br /><br />so why do seemingly most of the core accretion freaks jump right onto the highly unbelievable "giant cataclysmic impactor with a mars planet made the moon" idea??? wuh?? <br /><br />sure, it MAY have. but is highly unbelievable and asking a lot of a purely model-based speculation. because it cannot (at this point) actually be disproved, i cannot sit here and say with absolute certainty that the impactor idea is total nonsense --but i believe it is total nonsense and absolute crap. <br /><br />

 

[CalliArcale]

It would be interesting to do a survey of actual scientists and see just how popular the various theories really are, and whether or not there are any patterns. <img src="/images/icons/wink.gif" /> I know the impactor idea is more popular in the mass media, and I think this has a lot to do with drama. Things blowing up good is always popular. <img src="/images/icons/wink.gif" /><br /><br />I think it especially appeals to nerds, to be honest. I mean, have you ever seen "Mythbusters"? Most nerds like things blowing up, so there's a certain asthetic appeal there.<br /><br />Perhaps one of the best ways to test it would be to get not only more lunar samples but also samples from other bodies. Stardust will shortly be returning the very first non-lunar extraterrestrial samples, but I rather doubt they'll be of much use for this. If Hayabusa can be coaxed home and if the gun really did fire, then maybe that will give us better answers, although there's still too much pot-luck involved for me to really cast any bets on that. Bigger missions in the future, especially manned ones, may be what is required to really test this. Because I've just thought of a way to actually test it. (JonClarke or anyone else, feel free to step in and tell me where I'm wrong! I'm no geologist.)<br /><br />The impact has to have happened early in the history of the Earth-Moon system. Since it would've liquified both bodies, odds are there aren't any rocks predating it, so the oldest rocks on Earth and the Moon will give the dates when those bodies last solidified. They should match, regardless of whether they formed separately or were fragments of a larger body. But if the impactor theory is correct, they should be younger than the oldest rocks in the solar system. You use old rocks to date an object, so if the Moon is younger than Mars (for instance), that would tend to favor the impactor theory. If, however, they are the same age, it would severely limit the possible opportunities for s <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[bonzelite]

<font color="yellow"><br />I think it especially appeals to nerds, to be honest. I mean, have you ever seen "Mythbusters"? Most nerds like things blowing up, so there's a certain asthetic appeal there. </font><br /><br />LOL!! LOL!! you are right! that is funny as hell; you are so correct. bravo! they're always using a 30-0-6 to blow off the head of a transparent gelatinous person with the skull inside! and they pee on the third rail to see if it will shock them. <br /><br />i think it's an inside subconscious rebellion against the absolutely dull and paint-drying waiting room of core accretion theory. man is that dull. <br /><br />i guess that's why they need the big bang --it's a great selling point of some excitement: out of the lifeless mechanical vacuum of cold they at least have that one moment of fiery glory! <br /><br />

 

[jatslo]

<font color="yellow">The link now is only to the abstract. Back then Elsevier was temporarily allowing full article to be read.</font><---- The link is good, but the abstract did not load. What is a the policy about posting copyrighted material that is not accessible by the general public?

 

[jatslo]

I am allowed to write about and quote about anything, so long as I provide a citation. Posting on the Internet would be considered self-publishing by some, but I don't make money doing it, so... I can also save files to my computer, in which I only do when writing.<br /><br />Anyway, the Earth's Moon: If the Earth was mostly fluid (90%, for example), and a mass hit the Earth, we would have a splash, so to speak, i.e. like tossing a pebble into a stream. The droplet that pops up has zero trace of the impact'er, but is clearly water; however, if you want symmetry faster, relative to the moon, then we need a 90 degree impact'er, because otherwise the droplet would not be symmetrical. Drop a pebble in a stream, and you will see a droplet pop up, and pretend that droplet had escape velocity, but how did the Moon reach 2000 miles per hour orbit on a 90 degree impact?

 

[bonzelite]

wow. that is a great insight, jatslo.

 

[mikeemmert]

<blockquote><font class="small">In reply to:</font><hr /><p>"Because I've just thought of a way to actually test it. (JonClarke or anyone else, feel free to step in and tell me where I'm wrong! I'm no geologist.) <br /><br />The impact has to have happened early in the history of the Earth-Moon system. Since it would've liquified both bodies, odds are there aren't any rocks predating it, so the oldest rocks on Earth and the Moon will give the dates when those bodies last solidified. They should match, regardless of whether they formed separately or were fragments of a larger body. But if the impactor theory is correct, they should be younger than the oldest rocks in the solar system. You use old rocks to date an object, so if the Moon is younger than Mars (for instance), that would tend to favor the impactor theory. If, however, they are the same age, it would severely limit the possible opportunities for such an impact to have occured, down the point where it becomes less plausible. If Mars proves younger, that would show pretty much nothing about the Earth-Moon system, but give room for new speculation about Martian history."<p><hr /></p></p></blockquote><br />We can test some of this right now. There's a warehouse full of meteorites from Antarctica somewhere. It's even got a few Martian meteorites.<br /><br />I'm in the "fast acretion" camp, based on Lagrangians. But I don't really know why it was so fast. The best guess I've got is some residual gas in the solar nebula creating friction. Or maybe very fine particles acting like a gas that somehow didn't get blown away by the solar wind.<br /><br />Rapid collapse strands material at Lagrange points, which I've posted about extensively.<br /><br />Vogon, how's your look at Valhalla and Aesgard going? I saw some of that on wikipedia today because I was wondering why Titan has a dense atmosphere and Ganymede does not, and decided to take a look at all the Galileans while I was at it. Something about that huge round spot on Ganyme

 

[bonzelite]

i'm for fast accretion as well, as said before. i think some accretion events are molten from the very beginning, and then cool. <br /><br />not always cold, then vander walls forces clump, then getting hot, then molten, then cool.

 

[raghara2]

"It is indeed an interesting question whether one can refer to information once offered completely free to the public that later was sequestered after this release."<br /><br />That work was willingly public at internet, so you can cite from it freely. It's the same as you'd have borowed a book from friend, however no such book is in the public library.<br /><br />If it would be something like company secret, or information that is state secret, or information that could damage someone, or you'd be contacted by author(prefferably)/publisher, some restrictions would apply.<br /><br /><br /><br />Look at Bern treaty.<br /><br />For example if you'd hack US army server and show perfect plans for new version of nuclear warhead, you might have been in several problems in US, In much smaller problems in other countries, and in completely no problem in countries that hate US.