Timeline for What is the nature of "rock vapor" in this description of the formation of the Moon?
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| Feb 28, 2021 at 7:58 | comment | added | Mr. Nichan | I started working on an answer, but I think I'm going this paper anyway. It goes into a lot of detail about the kinds of molecules that might have been involved as the moon was condensing. Thermodynamics of Element Volatility and its Application to Planetary Processes | |
| Dec 17, 2020 at 8:16 | comment | added | Mr. Nichan | Also, I think I've recently figured out that N2 and CO both dissociate around 8000K on average (It's actually a gradually equilibrium change.), and that the energy required to break apart the triple bonds in these molecules is in the same ballpark as their ionization energies. CO supposedly has the highest (technically most negative) bond energy of any molecule: 1072 kJ/mol, wheras N2 has 942 kJ/mol, and SiO, whose bond is probably more like a double bond, only 794 kJ/mol. | |
| Dec 17, 2020 at 7:55 | comment | added | Mr. Nichan | I'm planning to do this, since you've said it twice. I'm just thinking maybe I should wait until after I finish something I'm working on that would be informative here. Of course, I might never finish what I'm working on, and I might answer before I do. I've also just copied and saved the comments before this one. Also, Sarah Stewart's paper that userLTK tracked down seems to be free access, at least for me, unlike he said. I don't appear to be logged in to the website in anyway, so I assume either it's changed since that comment was made or userLTK misinterpreted it. I would guess the former. | |
| Dec 14, 2020 at 8:07 | comment | added | uhoh | @H.H. Thanks for all of this! I wonder if you might consider posting this as an additional answer? I think these comments will stay put, but we can't depend on that the same way that we can question and answer posts, and future readers may skip comments altogether. | |
| Dec 14, 2020 at 7:11 | comment | added | Mr. Nichan | After rereading this question, though, I've noticed something. The vapor that extends out to those far distances that's she's proposing the moon accreted from is probably going to be very low-pressure low-density gas and dust (dust precipitating out of the gas), whereas the papers I linked deal with high pressure gas and supercritical fluid that would also formed by the impact. Of course, it would BECOME pretty dense and high pressure as it accreted, but it also would likely accrete from dust and form much cooler than the vapor when that happened. | |
| Dec 14, 2020 at 7:02 | comment | added | Mr. Nichan | That's based on Ab Initio Molecular Dynamics Simulations. I just now found another one based on laser pulse experiments that deals with diopside (MgCaSi2O6) at much higher pressures and temperatures: agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011JE004031 | |
| Dec 14, 2020 at 6:57 | comment | added | Mr. Nichan | Oh, I forgot to put the link: pnas.org/content/115/21/5371 | |
| Dec 13, 2020 at 21:51 | comment | added | uhoh | @H.H. Did you mean to mention a specific paper? | |
| Dec 13, 2020 at 2:26 | comment | added | Mr. Nichan | Here's another promising looking paper. It's about MgSiO3 vapor, liquid, and supercritical fluid, mentioning temperatures from 4000K to 9000K (though probably not covering all equally), with a specific emphasis on the Moon-forming impact. | |
| Nov 19, 2020 at 23:45 | comment | added | uhoh | @H.H. this is really interesting! Yes this is something I'll have to start reading up on, thanks! just fyi re TiO Why does titanium oxide around Betelgeuse produce this particular sawtooth-shaped absorption spectrum? (I've just added a bounty) | |
| Nov 19, 2020 at 18:54 | comment | added | Mr. Nichan | There is a "bonding continuum" between ionic and covalent bonds, because electrons don't completely transfer all of the time in "ionic compounds". Also, I've just realized that if you want info on rock vapor above 4000K, you may want to look into atmospheres of small stars. M-class stars have photosphere temperatures around 2400K~3700K. The M stands for "molecular" I think, because they have oxide molecules like TiO and (in colder ones) VO. stars up to 6000K contain neutral metal atoms, noting that metals ionize easiest. pages.uoregon.edu/imamura/122/lecture-4/mk.html | |
| Nov 7, 2020 at 15:59 | comment | added | Mr. Nichan | SiO2, and SiO are definitely covalent, and I think AlO (present in vapors, I think) and Al2O3 (I don't know if that exists in rock vapor) probably are too. I think there might actually be a continuum between covalent and ionic bonding, though. In valence bond theory, polar bonds are apparently stronger because of the contribution of "ionic canonical forms", which might simply mean that the different areas of electron-density attract each other, but it's always possible that some sort of quantum superposition could happen when discussing chemical bonding. | |
| Nov 7, 2020 at 15:47 | comment | added | Mr. Nichan | It seems to actually be ABOUT isotopic fractionation, where certain isotopes will be more enriched in the liquid phase vs the gas phase, presumably leading to measurable isotopic differences in modern Earth and Moon Rocks, but on the way it discusses olivine vapor, as well as some other parts of the vapor. I think that gaseous salt "molecules" like MgO and FeO (important in it rock vapor) are still ionically or mostly ionically bonded, but this keeps the ions together in a molecule. The answer should be in the thesis in the chemistry stack exchange answer I linked to, but that's hard to read. | |
| Nov 7, 2020 at 15:29 | comment | added | Mr. Nichan | I was just closing tabs I had open from yesterday and I noticed what looks like a paper on almost exactly your question: arxiv.org/pdf/1012.5325.pdf , "Chemical Fractionation in the Silicate Vapor Atmosphere of the Earth", by Kaveh Pahlevan, David J. Stevenson and John M. Eiler. It is specifically the Moon-Forming Impact. | |
| Nov 7, 2020 at 1:44 | comment | added | Mr. Nichan | If one really wanted to answer specific questions like this, one might look at Gibbs free energies to determine chemical equilibria and at the ionization energies and electron affinities of elements, molecules, and ions. For instance, the Gibbs energy change of SiO2 > SIO + O2 drops below 0, and therefore happens, though maybe slowly, around 3200 K, which is also about the boiling point of SiO2 according to Wikipedia, and O2 > 2O seems to happen around 3800 K. (pubs.acs.org/doi/abs/10.1021/cr60206a002 , which you may not have access to.) | |
| Nov 6, 2020 at 23:58 | comment | added | uhoh | @H.H. you are very persistent and brave! I have a little traveling today (bus, train) so maybe I will take some time and have a look at some of those today too. | |
| Nov 6, 2020 at 22:47 | comment | added | Mr. Nichan | Some of the sources for that paper are probably better information for the chemistry details. I've just started looking at them. | |
| Nov 6, 2020 at 21:01 | comment | added | Mr. Nichan | I might do that after reading it all the way through, which is something I have some reason to do but haven't done yet. I mostly just looked at the graphs and checked the "computational methods" section because I wanted to model something similar. I was rather disappointed by their description, though, and it looks like they just modeled equilibrium at the surface and equilibrium by pressure and temperature in the atmosphere, roughly allowing for cloud-forming, w/o considering convective mixing rates, let alone disequilibrium, but it was also hard to tell from their vague description. | |
| Oct 15, 2020 at 12:45 | comment | added | uhoh | @H.H. unfortunately I won't be doing that soon; please consider adding at least a short answer and summarizing what points in those links address this question. Thanks! | |
| Oct 15, 2020 at 8:06 | comment | added | Mr. Nichan | You might also want to check out the recent Durham University planetary collision simulations if you haven't seen them yet, including ones about the collision that formed the moon: icc.dur.ac.uk/giant_impacts They don't really answer your question at all, though. | |
| Oct 15, 2020 at 8:03 | comment | added | Mr. Nichan | That paper only goes up to 4000 Kelvins, though, and assumes equilibrium is reached rather than modelling collisions because it's focus is hot extrasolar planets. | |
| Oct 15, 2020 at 7:56 | answer | added | Mr. Nichan | timeline score: 0 | |
| Oct 15, 2020 at 7:51 | comment | added | Mr. Nichan | You should check out this paper called "The Vaporization of The Earth": iopscience.iop.org/article/10.1088/0004-637X/755/1/41 That mostly talks about composition. As for "nature", I believe the compounds it gives are all "molecules" if not clearly lone atoms or ions, though I don't know if the bonds are covalent. There are weird things at such temperatures like free radicals (e.g., neutral OH) and "molecular" forms of what are normally salts (e.g. NaCl and Na2Cl2 molecules: See the question: chemistry.stackexchange.com/questions/14174/… ) | |
| Jun 17, 2020 at 9:47 | history | edited | CommunityBot |
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| Dec 5, 2018 at 8:43 | vote | accept | uhoh | ||
| Nov 6, 2018 at 6:06 | answer | added | userLTK | timeline score: 4 | |
| Nov 6, 2018 at 4:42 | comment | added | uhoh | @userLTK same title and dates: arxiv.org/abs/1802.10223 and researchgate.net/publication/… | |
| Nov 6, 2018 at 4:39 | comment | added | userLTK | I tracked down her publication though it appears you have to pay for it: agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JE005333 and here's a more detailed article on her research. ucdavis.edu/news/… I'll also add a short answer: | |
| Nov 5, 2018 at 12:00 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Oct 8, 2018 at 18:22 | comment | added | userLTK | You also might find this question interesting: chemistry.stackexchange.com/questions/19521/… The SO2 bond, in gaseous form is probably somewhat similar to the CO2 bond, slightly weaker but similar. It's also worth noting that there's no specific temperature of dissociation or plasma state, both happen gradually over a range of temperatures. Unlike boiling (at specific pressure) or freezing points. At the temperature rock vapor forms, a percentage of it would probably undergo dissociation. At higher temperatures, that % increases. | |
| Oct 8, 2018 at 18:07 | comment | added | userLTK | Small sidebar, but highly ionized rock vapor is unlikely because high-ionization would also undo any chemical bonds. Partially or weakly ionized rock vapor may be possible but high ionization tends to split most gas molecules into atoms. en.wikipedia.org/wiki/… | |
| Oct 7, 2018 at 11:59 | comment | added | uhoh | @userLTK got it! ~100 eV per atom is a phenomenal amount of energy to start with. In that particular part of that sentence, I'm making some attempt to think about how the initial kinetic energy is partitioned amongst the final products. I'm sure there's some upper limit to what fraction can be converted to rotational energy and I'm just guessing it's less than half. I'll do some more reading on this in the next few days. Thanks! | |
| Oct 7, 2018 at 11:52 | comment | added | userLTK | I should have said angular kinetic energy not momentum. Fair enough. | |
| Oct 6, 2018 at 11:47 | answer | added | AtmosphericPrisonEscape | timeline score: 1 | |
| Oct 6, 2018 at 8:37 | history | asked | uhoh | CC BY-SA 4.0 |