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Where did our elements come from?

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newtonian

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I know, btw: supernovae. <br /><br />I am asking for more detail.<br /><br />Like, how does our proportion of elements compare with supernovae or the proportion of elements in our local region of space?<br /><br />Assuming the standard model of planetary formation and accretion - what was the product proportions of the stellar disc from which earth and other planets were formed?<br /><br />Do these proportions agree with what is predicted by simple accretion from disc matter which changed by mass as one gets closer to the sun?<br /><br />Why does earth have so much oxygen in its crust? Oxygen is the most abundant element in earth's crust.<br /><br />Why?<br /><br />Also, why is aluminum so abundant in earth's crust? And silicon?<br /><br />How did earth accrete its water? <br /><br />Do you consider condensation catastrophes, among which the Noachian flood would be the last, to be consistent with known facts about early earth and its geology?<br /><br />How unique is earth's geochemistry compared with other planets?<br /><br />Is there any other planet with an ozone shield?<br /><br />Could such be formed abiotically by photolysis of water by UV irradiation by starlight?<br /><br />I have many more questions on this, but the above is good, I hope, for starters.
 
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weeman

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These are all very good questions. Questions that most people ponder.<br /><br />Massive galactic explosions of some kind, like supernovae, are most likely the key to the diversity of elements. If indeed hydrogen and helium were to most prominent elements at the time of the Big Bang, then some other force in the Universe is what gave us so many different elements.<br /><br />It is not entirely known how Earth accreted its water. It may have been from comets pounding early Earth, or moister may have been released through volcanoes when Earth was much more volcanic than it is today. I have also heard of a theory about a ice-rich planet, or large body of some kind that slammed into Earth early in its formation. <br /><br />Oxygen is certainly a very abundant element on Earth. However, its early atmosphere may not have been like it is today. Earth may have had an atmosphere rich with carbon dioxide in its early days. If indeed Earth was more volcanic, this would have meant higher levels of carbon dioxide than today. Three of the main elements released by volcanic activity are sulphur dioxide, water vapor, and carbon dioxide. <br /><br />Oxygen is certainly abundant in rock samples. When we take samples from oceanic crust, in the ocean floors, we often see rock that can be high in carbon dioxide. This too hints at a carbon dioxide-rich atmosphere in Earth's early days. If volcanoes released vast amounts of wator vapor into the atmosphere, they may have lead to the early storms on Earth. Rain would have pulled the carbon dioxide out of the atmosphere, diffusing it in the oceans.<br /><br />As for an ozone shield, I am not entirely sure, but here is my best guess. As weather started to pull carbon dioxide out of the atmosphere, and the landmasses of Earth became more abundant with water, plantlife might have errupted at this point. Oxygen started to become more prominent in the atmosphere, and the average surface temperature of Earth became much lower. Ozone is often created when ox <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>
 
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newtonian

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weeman - Excellent response - informative, thought provoking.<br /><br />To add a few things I already knew:<br /><br />1. Early earth CO2. The 1989 print edition of Encyclopedia Brittanica outlined the surface (crust) composition of earth - in petagrams.<br /><br />It noted that carbon is very common in carbonates, for example. It also noted that the geologic carbon cycle was responsible for this. That is similar to your post - except that CO2 does not need rain to dissolve into oceans. It also dissolves by direct interface especially as CO2 is relatively heavy.<br /><br />When one compares how much CO2 is actually locked up in earth's carbonates, and then assume most of this was once in early earth's atmosphere, we end up with an atmosphere approximately as rich in CO2 as is presently on Venus.<br /><br />My question, of course, is whether this proportion of CO2 is consistent with supernovae origin of this molecule, which has double the oxygen compared with carbon. Compare less dramatic origin of some elements, including notably carbon, from red giant emissions.<br /><br />I do remember reading a scientific paper detailing origin of oxygen in stars (not specifically supernovae), but I have lost the link due to my computer crash last year.<br /><br />It seems earth has more oxygen than neighbor planets in proportion - am I correct?<br /><br />2. Early earth oxygen. Chemical evolutionists often state there was zero oxygen - due to circular reasoning involving origin of life by chemical evolution rather than by creation or seeding from space or both.<br /><br />However, early earth clearly had water. And if there was no oxygen, then there would be no ozone shield -n which would then expose the water to intense UV irradiation.<br /><br />The latter would cause photolysis of water into hydrogen and oxygen. If early earth did have a thick CO2 atmosphere, then hydrogen may have escaped due to relative weight compared with CO2 - but oxygen, which is heavier, would likely have rema
 
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weeman

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<blockquote><font class="small">In reply to:</font><hr /><p> Such discs would naturally concentrate heavier elements closer to parent stars - which is likely why gaseous planets like Jupiter, Saturn, Uranus and Neptune are further out. Why Kuiper belt objects, and Pluto, are not gaseous is quite another matter though - and it is interesting that these contain, apparently, an abundance of water (ice) - as do comets. <p><hr /></p></p></blockquote><br /><br />Gaseous planets might also have to do with temperature. The inner, terrestrial planets might have had very gaseous atmospheres when the Sun was a protostar. When it did ignite into a full fledged star, the temperature became too hot for the inner planets to maintain their gaseous atmospheres. These thick atmospheres would have eventually been boiled away. The gas giants still maintain their atmospheres because they are much colder since they are at such greater distances. <br /><br />I don't exactly know how Pluto and the Kuiper Belt can be more rocky. Could it be possible they didn't form in the disc with the rest of the planets? Is it possible the Kuiper Belt has been sort of acquired over the life time of our solar system?<br /><br />I agree with what you are saying about Earth needing some levels of oxygen, even when scientists might say there weren't any at all. What we would have to research is how thick the ozone shield has to be to allow cooler temperatures on Earth. We would have to know how much oxygen it takes to produce a thick enough ozone shield to lower surface temperatures, and protect the surface from harmful UV rays. If there was a point in Earth's past of almost no ozone shield, the surface would have been much too hot for any type of condensation or weather. <br /><br />So if volcanoes did indeed give Earth much of its liquid water, then there would have had to be cool enough temperatures for it to condensate. This would have to mean that the atmosphere was thin enough (not high in CO2), and that it also had a str <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>
 
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MeteorWayne

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<font color="orange"> "I don't exactly know how Pluto and the Kuiper Belt can be more rocky. Could it be possible they didn't form in the disc with the rest of the planets? Is it possible the Kuiper Belt has been sort of acquired over the life time of our solar system? " </font><br /><br />I think the jury is still out on the rock/ice ratio beyond Neptune. Masses are not well known for more than 3 or 4 such objects. So composition is not well constrained.<br /><br />So far it seems likely that the KBO's, etc formed from the proto-disk, mixed with material ejected from the young sun to the outer reaches of the solar system. (See stardust results)<br /><br />Acquistion from outside the solar system (if that's what you were implying) is a very rare process. The dynamics of non solar objects being captured requires a very narrow set of circumstances. It probably has happened, but would likely be an exceedingly unusual event amounting to a few dozen objects among the millions or more that are in the solar sphere of influence.<br /><br />That's what I've gleaned from the research.<br /><br />MW<br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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