Early Earth: 30 Million years to layering?

[spacester]

Wow, it looks like there is a radically new view of the early Earth. It turns out that better measurements of the mass 142 isotope of Neodymium leads them to think that the crust formed much earlier than previously thought. Only 30 Million years after the solar system was formed!<br /><br />Are they are saying the Moon was formed even earlier? If one assumes the thinness of the crust is due to the moon-forming impact, wouldn't that be a logical conclusion? <div class="Discussion_UserSignature"> </div>

 

[bonzelite]

says there's more evidence the moon formed from the earth. doesn't go into specifics as to how. <br /><br />article is very interesting. implies earth was molten very early and crust was pretty much decided very early. i tend to believe the earth was molten right away and did not take eons to accrete from fine dust. the article kind of sort of maybe could be construed to mean that. <br /><br />the article does not really pose to question traditional accretion theory, per se, but one could wander dangerously close to going there from what it says about the chondrites. i'm apt to feel that the moon and earth formed near or at the same time in tandem.

 

[yevaud]

Since Apples and Oranges appear to be being mixed here (<i>the earth was molten right away and did not take eons to accrete from fine dust.</i>), allow me to explain:<br /><br />What this article means is that the process of planetary accretion is not any different than it has been understood to be. The planet did *not* "accrete from fine dust," in the sense you mean, Bonzelite.<br /><br />As a Protoplanetary disc forms, dust and small particles are attracted together by Van Der Waals forces. Only later, as larger and larger bodies accrete, does gravity take over as the driving force for accretion.<br /><br />Once a large body has formed - in this case, the Earth - the body is in a more-or-less molten state and begins to shed heat. This is when the process known as "Differentiation" is occurring. Heavier elements sink towards the core and lighter elements rise towards the surface. The rate at which this occurs will determine to a great extent the composition of the material at the surface and the crust.<br /><br />So what this article is implying is that the process of Differentiation took place much faster than was originally assumed. E.g., that within 30 million years of what would be considered the "beginning" of Differentiation, most of the Differentiation has taken place, leading to the crustal composition we see today, rather than was originally believed, that Differentiation took place over a much longer period of time.<br /><br />Hope that clarified things for you. <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>

 

[spacester]

Nice post as always, Yevaud. I’m interested in what this means for lunar science.<br /><br />My understanding is that the reason the Earth’s crust is so thin is believed to be that when the giant impact scenario of lunar formation occurred, much of the lighter material of the proto-Earth was stripped off, leaving a thin crust of lighter material.<br /><br />So if Proto-Earth already had a crust formed by 30 Million years, does that mean that this impact occurred even sooner? IIRC, the standard date of the Moon’s formation is 50M years after solar system formation, I take it that factoid is under review? Or could the crust have formed in 30M years and then recovered after a later lunar-forming impact?<br /> <div class="Discussion_UserSignature"> </div>

 

[centsworth_II]

<font color="yellow">"I’m interested in what this means for lunar science."</font><br />I take it then that you are interested in getting humans back on the moon to do science. In that case you should be as excited about NASA's plans to do so as I am. <br /><br /> <div class="Discussion_UserSignature"> </div>

 

[najab]

><i>So if Proto-Earth already had a crust formed by 30 Million years, does that mean that this impact occurred even sooner?</i><p>Not necessarily - the crust could have been largely formed by 30M years, then much of it could have been lost in the Moon-forming impact - what we see now could be just a remanent of the original crust.</p>

 

[spacester]

<font color="yellow">I take it then that you are interested in getting humans back on the moon to do science. In that case you should be as excited about NASA's plans to do so as I am. </font><br /><br />Um, yeah. Did you think otherwise? Of course, I can only guess at your level of excitement - maybe I'm *more* excited than you are!<br /><br />One thing that would make me even more excited than I am is to speed up the schedule . . . . <div class="Discussion_UserSignature"> </div>

 

[bonzelite]

Yev, i understand what you mean. so, then, why did the differentiation of materials happen so soon and quickly? <br /><br />in essence, the scenario of accretion from fine dust is correct, though. it took that for larger clumps of matter to accrete. right? <br />

 

[yevaud]

Hi. Sorry - away for several hours.<br /><br />Well, it does begin with dust and molecules at the very outset - this is when I was taught that Van Der Waals forces predominate. As time goes on, and a Protoplanetary disc forms out of the original dust/gas cloud, larger and larger clumps begin to form, and gravity begins to take over, until large bodies (protoplanets) begin to accrete.<br /><br />As far as the *why* it is now believed that it took only 30 MY, I'll have to go do some digging (joke half-intended) to find out, if there's even a theory on why (which is not the same as the discovery utilizing the isotope ratios, which is more of a what, not a why).<br /><br />More later, after I go and find out. <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>

 

[yevaud]

Hard to say. Obviously, the new theory on Differentiation would affect that - likely increasing the amount of lighter material carried away than was originally understood. But generally, that is (or was, last time I checked) the reigning theory. <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]

30 MY is extremely quick and nearly non-existent a time frame in this context. would accretion theory, too, be up for revision, then?

 

[yevaud]

Doubtful. There is no other way for Protoplanetary bodies to form. <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]

ok.

 

[yevaud]

Although, if there's a new schema for the period of time for Earth to almost fully differentiate, it may well also be the case for Mars. <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]

in all due respect, i ask the question because if the differentiation is nowhere near what was assumed according to conventional theory, i would as well question the entire daisy-chain of events leading up to this differentiation. in other words, i'd be less apt to just keep the rest of the story but allow for only rapid differentiation as a compartmentalized "new" thing. the entire accretion process, in my opinion, is up for grabs --not entirely wrong, but inevitably up for some serious chopping block type of revisions. and i know this cannot be taken into account until there is actual evidence. i'm just not in love with the idea as it stands. particularly when we have KBOs posing gigantic and uncomfortable questions. <br /><br />i know that i am not a scientist, and i know i am only speculating. i'm posing the idea, though. my intuition tells me that the rapid crustal formation is not the only "shocking" thing in this story. there is more to come. i will bet my house on that.

 

[yevaud]

<i>i will bet my house on that.</i><br /><br />Start scoping out Homeless Shelters to move into then. <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]

LOL!! funny <img src="/images/icons/wink.gif" /><br /><br />you're not even up to harmless private pondering that the theory may need a little tweaking? just a wee bit? not entirely discarded. but just a little revised? <br /><br />no?<br /><br />you can't possibly tell me the rapid crustal formation evidence is the only little anomaly we're going to hear about? right?

 

[yevaud]

Seriously, you make statements that I frequently hear: "My Intuition," "i am not a scientist," "i am only speculating," "in my opinion."<br /><br />Ok, well that's fair, except in the absence of formal training in Planetary Science, all of the above is irrelevant and meaningless. I can express "opinions" about Molecular Biology, but I will be wrong 99% of the time (and probably more), as I have little training in that field.<br /><br />Speculation is fine, but - BUT - unless you know a huge body of knowledge in a subject, you're not even an amateur. If you want to debate something, sure, more than happy to - but those kind of comments are frequently used to try to shut off the professionals from stating fact.<br /><br />*Not saying this is what you're doing, but please be warned* <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>

 

[yevaud]

Well, are we likely to discover new things? Yes. Will they completely jigger everything that's previously known?<br /><br />NO. <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>

 

[yevaud]

Sorry I am of late a bit of a pecker-head on this sort of thing, but please understand. Having an idea challenged is one thing. Having it *constantly* challenged by someone not in the particular field is something else entirely. And I have experienced it way too much of late.<br /><br />I'll express this a different way. Suppose you're a Civil Engineer. And it is discovered that the properties of a type of steel utilized in the construction of large buildings are slightly different than understood. But that's all.<br /><br />Along come people who start to say, "well, I have no experience in Construction or Civil Engineering, but IMO this now means that the properties of every metal used in Construction must be way, way wrong, beginning with the mining process."<br /><br />That's what I mean. <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]

i understand that. yes, very annoying.

 

[yevaud]

Sorry if it sounded like a rant. It was intended as more a "I will go *this* far, but will not go *here*" commentary, and I got a bit carried away. <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>

 

[spacester]

I am definitely a not-even-an-amateur, I’m just trying to work thru the basic logic of the information presented here.<br /><br />So everything is assumed to have the same ratio of the precursor 146Sm when the solar system formed. We have recently discovered that the ratio of its decay product, 142Nd, to other isotopes, is not the same for Earth and Moon as it is for meteorites, it’s a higher ratio. Thus, something happened to cause the composition of Earth/Moon to diverge from that of the meteorites. Further, the measurements place this ‘differentiation event’ (my term) as ‘within the first 30 Million Years after solar system formation (meaning Sol is formed or that all the planets are formed?)’<br /><br />So we have a proto-Earth at, say 1 Million years after forming, a big molten ball made up of the same stuff as found in present-day meteorites: chondrites and other types. It rapidly differentiates, and within another 29 Million years there is a core and a mantle and a crust. The Carnegie Scientists think that the rapid crystallization of the early magma ocean caused the mantle to separate into chemically distinct layers (how?), and the high-ratio stuff of the Earth’s crust is matched by low-ratio material at the bottom of the mantle, where it helps keep the outer core molten due to radioactive decay; this decay being consistent with the lower ratio stuff.<br /><br />Now somewhere in time (20 Million years later if current lunar age estimates are correct and IIRC) the lunar-forming impactor comes along and itself does a pretty fine job of creating large pools of differentiated matter. The theory is that a lot of the lower density stuff in the Earth’s proto-crust at the impact point was ejected, but the higher density stuff deep in the mantle, not so much. The moon’s 142Nd ratio is the same as Earth’s, so that is consistent.<br /><br />But how do we know that the lunar forming impact didn’t happen much sooner, and that “somehow” it wasn’t the cause of the differentiated m <div class="Discussion_UserSignature"> </div>

 

[bonzelite]

Yev, it's okay. i respect your creds and knowledge even if it appears that i've gone to join the loony-crowd of illuminati UFO conspiracists --i have not. rest assured, i'm very much digging this stuff. the new findings are extremely exciting and awesome. part of the coolness factor is knowing that there is an endless stream of discovery waiting for us. my imagination perhaps replaces hard-core engineering training. so i hope you're at least entertained by that. <br /><br />i am vexed over traditional accretion models because myriad extra-solar planets and our own KBOs are throwing out very compelling evidence of ----something not yet heeded. accretion or "coagulation" of planets may be more dynamic and rapid a process than is made out to be. <br /><br />and if it isn't, then i can hang with that, too <img src="/images/icons/wink.gif" />

 

[bonzelite]

it would be fun to consider that the earth/moon system developed locally, concurrently, and not out of a cataclysmic impact event. it would simplify matters as well.