Is science sometimes in danger of getting tunnel vision? Recently published ebook author, Ian Miller, looks at other possible theories arising from data that we think we understand. Can looking problems in a different light give scientists a different perspective?

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There were three papers in November that pleased me quite a bit because they gave additional support to my theory of planetary formation. The first (Earth Planet. Sci Lett. 385: 110) examined the Se and Te systematics of mantle derived peridotites on Earth, and showed that the ratios are not consistent with melt depletion alone. The results indicate no firm evidence for chondritic S-Se-Te signatures in the primitive upper mantle, which challenges the simplistic perception that near-chondritic Se/Te ratios may readily trace the Late Veneer composition. This is of importance because these ratios are often cited as "proof" of a massive late accretion of chondrites, which would be the source of the volatiles on Earth. In my opinion, the volatiles were accreted by other means, and it is good to see the "opposition view" have its main evidence removed. The second (Nature  503: 513 ) showed that a meteorite from Mars is a regolith breccia with zircons of an age 4.428 + 25 My. The evidence implies that Martian crust formed in about the first 100 My of Martian history, which in turn implies no magma ocean. The magma ocean is a requirement of the standard theory where massive embryos collide to form protoplanets, and the inherent gravitational energy would provide so much heat that a magma ocean is inevitable. If no magma ocean, then a different mechanism of formation is required. Finally, (Planet. Space Sci. 87: 130) a trough within Noctis Labyrinthus displays a diversity of hydrated minerals and fluvial channels, including opal, Al clays, gypsum and polyhydrated sulphates., and furthermore, these different minerals had to be laid down under different conditions. Accordingly, there should have been several periods of aqueous alteration.
For those interested in seeing more of my theory of planetary formation, Planetary Formation and Biogenesis will be available for 99 cents  as a special promo on (and 99p on – these are the lowest prices permitted on each case) on December Friday 13, and the prices increase daily for about 5 days until they reach normal price. Also on the promo is my novel Red Gold, which is about fraud during the settlement of Mars.  This ebook was written in the early 1990s, and to expose the fraud, a surprising discovery was required. The surprise was the discovery of what remained of the Martian atmosphere, which provided the nitrogen fertilizer necessary to make the settlement viable. The very first version that led me to the theory in the first book is outlined in the appendix, so this is one of the very few examples of how a theory got started. How important this is depends on whether the theory is correct, and I would love to know the answer to that one.
As an aside, that is the main difference between the experimentalist and the theoretician. If the experimentalist gets the wrong idea, the evidence usually (but not always) becomes evident quickly, such as when the wrong result is obtained. For the theoretician, the required evidence may not be easily obtained, and he is kept in suspense for some time. Thus Peter Higgs had to wait from the mid 1960s until now. At my age, I cannot afford that time, so I probably will never know for sure. Of course, I am convinced!
Posted by Ian Miller on Dec 2, 2013 4:32 AM GMT
The biggest alternative interpretation must surely be of quantum mechanics. So far there are at least three major interpretations, (Copenhagen, pilot wave, many worlds) with variations, but that should not let that deter one should it, after all, who understands quantum mechanics? After more than a little tiring effort, I have finally self-published an ebook on my alternative interpretation of quantum mechanics. (If interested, see ). Why self-publish as opposed to publish a series of papers? There are a number of reasons, not the least of which is that any part of the foundation of the theory that could be condensed into a paper is not very convincing by itself, whereas any of the applications of the interpretation without the underlying foundation is more difficult to understand. There are further reasons, including at my age there is a desire to get this out rather than argue with a sequence of referees.
How can there be a yet another interpretation? Actually, quite easily. We start with the Schrödinger equation, from which we get a wave function. The wave function is a complex function, correct? Well, not entirely. If you take the standard wave function as seen in fundamental text books, and consider this from the point of view of Euler's presentation of complex numbers, then the wave function becomes real at the very extremes of the crest and trough of the wave. The first significant difference of this interpretation is the assumption that the wave only has physical effect on the particle when it is real.
If that assumption is correct, then it follows that the phase velocity of the wave has to equal the expectation velocity of the particle, so that the two can be in roughly the same place at the same time. That gives a further relationship, from which the square of the amplitude must be proportional to the kinetic energy of the particle. Since energy is proportional to mass, it follows that the probability of finding the position of a particle will roughly follow the Born interpretation. It does not quite, but that is a detail.
If this interpretation is correct, then all the results of the two-slit experiment follow (and a further experiment is proposed that will give a rather unexpected result), the reason why an electron does not spiral into the nucleus of an atom as expected from Maxwell's relationships follows by following Maxwell's relationships! The Uncertainty Principle and the Exclusion Principle are now derived. But the real great advantage, from my point of view anyway, is that you do not have to solve differential equations! The only physically real picture is when the action is quantized, i.e. occurs in some numbers of Planck's quantum of action. First order computations for simple systems merely require counting. The basics of chemistry are simply obtainable by requiring the quantization of action over the sum of separable components. More on this in later posts, but one final comment. Assuming I am correct, obviously action is a very important concept, but how many chemists know what it is? When is it mentioned in undergrad courses in chemistry?
So, why am I tired? Ever tried compiling an ebook with mathematical symbols? If you do not use Unicode (Universal code) symbols, and Microsoft Word frequently does not, almost anything can come out. And the problem is, in some cases you cannot work out whether the symbol is Unicode or not. Also, you might imagine there would be one Universal code, right? Sorry, no. And, apparently as the versions change to adopt new symbols, old ones drop out, but not all of them. Some sort of standardization would be good!
Posted by Ian Miller on Nov 25, 2013 1:25 AM GMT
The recent Chemistry World highlighted a recent publication on astatine, in which the paper predicted that due to relativistic effects on the inner electrons, it would be metallic and monoatomic in the solid state. As some may recall, in previous posts I have questioned such relativistic corrections since I had previously published a paper ( in which I showed that ionization energies and lower excited state energies could be related through reasonably simple relationships involving quantum numbers. In this, the s electron of gold was actually more "normal", if that means agreement with the required relationship is better, than either copper or silver.
The reason I regard astatine as annoying comes from this consideration. In my paper cited above, the ionization potentials of valence electrons could be calculated from simple relationships involving only quantum numbers when there was only one electron in the level, while an additional term was required for others that approximated to a term only in the quantum number , but in practice was better with a minor empirical correction for each group. The important point was that this term was constant for a given column of elements in the periodic table, and there are relationships between groups. (This term is conceptually due to additional quanta of action being generated through the waves exploring all available space, and attenuates as increases because the number of orbitals to explore increases the number of cycles before the required quantum of action is completed. This lies outside standard quantum mechanics, and I shall elaborate my alternative interpretation in future posts.) Now, in principle if my alternative interpretation is correct and relativistic correction is not required, the ionization energies of the elements I did not calculate should still be given by the published relationships. (I regard the equations as predictions, even if I did not evaluate them.)
The relationships were not exact. There were two unexplained small regularities. The first involved a small term (st for this post) the sign of which depended on whether n and were odd or even, the magnitude of which increased with the distance from shell completion. There was also a positive term (+T for this post) that applied only to paired p electrons following d shell completion, thus Se, Br, Kr, then Te, I and Xe all required +T, as did Po. Recently ionization potentials have been measured for At and Rn, so how do my functions perform?
The prediction for astatine, with +T was 9.7606 ev; without it, 9.1893 ev; the observed value is 9.3175 ev. What should I make of that? Suppose we consider radon. Without +T, the predicted IP is 10.7457 ev; the observed value is 10.747 ev, which in my view, is fairly close, so my obvious conclusion is that there is some interaction with the d electrons that applies to Po when n = 6, not for Rn, and annoyingly, somewhere in between for At. In my opinion, admittedly somewhat biased since I am supporting my own theory, this would indicate that if the "non-hydrogen-like" wave functions are correct, there is no need for relativistic corrections here. Finally, it may be of interest that the IP of Fr is predicted without st to be 3.903 ev; the observed value is 3.938 ev.  These calculated values are based solely on the wave nature, without any terms for interference with other waves or resonances. The value of st required for Fr is of very similar magnitude to that for Rb and Cs, except that Cs is of opposite sign. Then, to confuse everything, the ionization potential for radium is such that some further effect might be operating, and that could be relativistic in origin.
What relativistic corrections are suggested? In one account (Chem. Rev. 112: 371-384) without relativistic corrections, the ionization potential of gold was 7.057 ev, and with it, 9.147 ev (observed, 9.2254 ev). Thus it would appear that contraction of the inner orbitals adds over 2 ev, and this should increase as the charge on the nucleus increases. I am sorry, but for me, this does not add up.
Perhaps chemistry would solve this issue? My calculation of the bond distance in At2 is 150 pm, and the bond energy of hydrogen astatide is 273 kJ/mol. Would that settle the question? Perhaps, but annoyingly I can't see the data coming any time soon because the most stable isotope of astatine has a half-life of 8.1 hrs. 
Posted by Ian Miller on Nov 18, 2013 4:28 AM GMT
A recent opinion in Chemistry World focused on the issues of the practicality of turning ideas into useful technologies. One of the arguments seemed to be that curiosity driven science was giving the world a false sense of what could be achieved, and worse, was taking funding away from where it could be more usefully spent. As usual in such issues, there are several ways of viewing the issue. First, look at the issue of why scientists make some of the outrageous claims. In my view, the answer is simple. It is not because the scientists have lost track of thermodynamics as implied in the article (although I guess some might) and it is not because they are snake-oil merchants. My guess is that the biggest reason is dressing up work to satisfy the providers of funding. Let me confess to one example from my own past.
My very first excursion into "the origin of life" issue came in the 1970s. I was supposed to be working on energy research, but funding was extremely tight, energy research needs expensive equipment that we did not have, so there was scope to do experiments that did not cost much. Gerald Smith and I had seen that the theory of the initial atmospheres required it to be carbon dioxide, which was thermodynamically very bad for biogenesis in terms of energy. Carbon dioxide is what life gets rid of at the bottom of the energy chain and is only returned to life by photosynthesis. So, if the geologists were correct, how did carbon biogenic precursors form from such an unpromising start?
Our idea was that the carbon dioxide could still be reduced through photochemistry. Water and carbon dioxide attacks olivine, and somewhat more slowly, pyroxenes, to dissolve magnesium ions and ferrous ions, and the concept was, Fe II and light would reduce CO2 to formic acid and thence to formaldehyde, whereupon the magnesium carbonate could help catalyse the Butlerov type reactions. So, we did some photochemistry, and persuaded ourselves that we were reducing CO2. It was then that a thought struck me. The Fe II must end up as Fe III, and what would Fe III do to organic materials? The answer was reasonably obvious: try some and find out. So we irradiated some dilute sugar with Fe III, and the carbohydrates simply fell to pieces, with an action spectrum corresponding to the spectrum of the iron complex. Many other potential biochemical precursors suffered the same fate. So, we wrote up the results, but then came the question, how were we going to justify this work? Well, since energy was the desired activity, we wrote a little comment at the bottom of the paper about the potential of photochemical fuel cells.
Did we think this was realistic? No, we did not. Did we think there was any theoretical possibility? Yes, while outrageously unlikely, it remained possible. Did it satisfy the keepers of returns to funding sources? Yes, because they never read past the keywords. You may say there was a little duplicity there, but first, this work cost very little and it did not distract us from doing anything else. We used equipment that otherwise would have been doing nothing, and the only real costs were trivial amounts of chemicals and the time spent writing the paper, because that was a real cost. Was the result meaningful? I leave that to you to decide, BUT for me, it was because it set me off realizing that the standard theory of atmospheric formation cannot be right. The carbon source for life could not have come from carbon dioxide initially, because in getting to reduced carbon from the most available source in the oceans, a much worse agent from the point of view of biogenesis was formed. Had we been able to show how CO2 could be the carbon source for biogenesis, I think that would have been interesting, but just because you fail in the primary objective, that does not mean the time was wasted. The recording of the effects of a failed idea are just as valuable.
Posted by Ian Miller on Nov 10, 2013 10:51 PM GMT
The  first round of results came in from Curiosity at Gale crater, and I found the results to be both comforting but also disappointing. The composition of the rocks, with one exception, and the composition of the dust were very similar to what had been found elsewhere on Mars. We now know the results are more general, but they are not exactly exciting. Dust was heated to 835 oC and a range of volatiles came off, and there was, once again, evidence of some carbonaceous matter, but the products obtained (SO2, CO2, and O2, HCN, H2S, methyl chloride, dichloromethane, chloroform, acetone, acetonitrile, benzene, toluene and a number of others) were almost certainly pyrolysis products.
An interesting paper (Nature Geosci. doi:10.1038/ngeo1930) found that when ices similar to those in comets were subjected to high velocity impacts, several aminoacids were produced. However, some were aminoacids such as α-aminoisobutyric acid and isovaline, which are not used for protein, and the question is, why not? One reason may be that our aminoacid resource did not come from such comets.
A circumstellar disk was identified around a white dwarf, and the disk was considered to have arisen from a rocky minor planet (Science 342: 218 – 220). There was an excess of oxygen present compared with the metals and silicates, and a lack of carbon, and this is consistent with the parent body having comprised 26% water by mass. This was interpreted as confirming that water-bearing planetesimals exist around A and F-type stars that end their lives as white dwarfs. Of particular interest was the lack of carbon. What sort of body could it have come from? I have seen suggestions that it would be a body like Ceres, in which case my proposed mechanism for the formation of minor planets would not be correct (because of the lack of carbon) but another option might be something that accreted in the Jovian zone, where I argue carbon is not accreted significantly.
Finally, Curiosity made a specific search for methane in the Martian atmosphere and put an upper limit of 1.3 ppbv, which suggests that methane seen on Mars did not come from methanogenic microbial activity, but rather from either extraplanetary or geologic sources. The latter fits nicely with my proposed mechanism of formation of Mars.
Posted by Ian Miller on Nov 4, 2013 1:35 AM GMT
The prize appears to have been given for work that leads to the modeling of how enzymes work. If I follow the information I have seen correctly, the modelling involves three different levels. The very inner site of reactivity involves a quantum mechanical evaluation of the reaction site and the reactivity. Outside this, where the protein strands fold and interact, the situation is simplified with simple (in comparison) classical physics, while outside this there is further simplification by which the situation is considered simply as a dielectric medium.
All of that seems eminently sensible, and there is little doubt that even with such simplifications there remains some serious work that has been done. However one thing concerns me: up until this award, I was totally unaware of it. Yes, this might indicate a lack of effort on my part, but in my defence, there is an enormous amount of information available, and for matters outside my immediate research interests, I have to simply rely on more general articles. Which gets me to the point: assuming this work has been successful, it is obviously important, but why has more not been made of it? Again, perhaps this illustrates a fault on my part, but again I feel there is more need to promote important work.
I guess the final point I would like to make is, could someone highlight the principles that this modeling work has uncovered? The general chemist has little interest in wading through computations of the various options open to such a complex molecule as an enzyme, but if some general principles are uncovered, could they not be better publicized? After all, they may have more general applicability.
Posted by Ian Miller on Oct 28, 2013 5:22 AM GMT
There was a recent comment to one of my posts regarding the formation of rocky planets, so I thought I should outline how I think the rocky planets formed, and why. The standard theory involves only physical forces, and is that dust accreted to planetesimals, then these collided, eventually to form embryos (Mars-sized bodies), then these collided to form planets. First, why do I think that is wrong? For me, it is difficult to see how the planetesimals form by simple collision of dust, and it is even harder to see how they stay together. One route might be through melting due to radioactivity, but if that is the case, one would need very recently formed supernova debris to get sufficient radioactivity. Then, as the objects get bigger, collisions will have greater relative velocities, which means much greater kinetic energy in impacts, and because everything is further apart, collisions become less probable and everything takes too long. The models of Moon formation generally lead to the conclusion that such massive impacts lead to a massive loss of material.
The difference between the standard theory and mine is that I think chemistry is involved. There are two stages involved for rocky planets. The first is during the accretion of the star, and near the star, temperatures are raised significantly. Once temperatures reach greater than 1200 oC, some silicates become semi-molten and sticky, and this leads to the accretion of lumps. By 1538 oC, iron melts, and hence lumps of iron-bodies form, while around 1500 – 1600 oC. calcium aluminosilicates form separate molten phases, although about 1300 oC a calcium silicate forms a separate phase. (The separation of phases is enhanced by polymerization.) Material at 1 A. U., say, reaches about 1550 - 1600 oC, while near Mars it reaches something like 1300 oC. Of particular relevance are the calcium aluminosilicates, as these form a range of materials that act as hydraulic cements. Also, the closer the material gets to the star, the hotter and more concentrated it gets, so bigger lumps of material form. One possibility is that Mercury is in fact essentially formed from one such accreted lump that scavenged up local lumps. Another important feature is that within this temperature range, significant other chemistry occurred, e.g. the formation of carbides, carbon, nitrides, cyanides, cyanamides, silicides, phosphides, etc.
When the disk cooled down, collisions between bodies formed dust, while some bodies would come together. Dust would form preferentially from the more brittle solids, which would tend to be the aluminosilicates, and when such dust accreted onto other bodies, water from the now cool disk would set the cement and make a solid body that would grow by simply accreting more dust and small bodies. Because there is a gradual movement of dust and gas towards the star, there would be a steady supply of such feed, and the bodies would grow at a rate proportional to their cross-section. Eventually, the bodies would be big enough to gravitationally attract other larger bodies, however the important point is that provided initiation is difficult, runaway growth of one body in a zone would predominate. Earth grows to be the biggest because it is in the zone most suitable for forming and setting cement, and because the iron bodies are eminently suitable for forming dust. The atmosphere and biochemical precursors form because the water of accretion reacts within the planet to form a range of chemicals from the nitrides, phosphides, carbides, etc. What is relevant here is high-pressure organic chemistry, which again is somewhat under-studied.
Am I right? The more detailed account, including a major literature review, took just under a quarter of a million words in the ebook, and the last chapter contains over 80 predictions, most of which are very difficult to do. Nevertheless, an encouraging sign is that the debris of a minor rocky planet around a white dwarf (what remains of an F or A type star) shows the presence of considerable amounts of water. Such water is (in my opinion) best explained by the water being involved in the initial accretion of the body, because it is extremely unlikely that such an amount of water could arrive on a minor rocky planet by collision of chondrites because the gravity of the minor planet is unlikely to be enough to hold such water. Thus this is strongly supportive of my mechanism, and it is rather difficult to see how this arose through the standard theory.
Posted by Ian Miller on Oct 21, 2013 1:57 AM BST
Leaving aside the provision of employment for modelers, I am far from convinced that the climate change models are of any use at all. As an example, we often hear the proposition that to fix climate change we should find a way to get carbon dioxide from the atmosphere, or from the gaseous effluent of power stations. This sounds simple. It is reasonably straightforward to absorb carbon dioxide: bubble the gas through a suitable base. Of course, the problem then comes down to, how do you get a suitable base? Calcium oxide is fine, except you broke down a carbonate at quite high temperatures to get it. Amines offer an easier route, but to collect a power station's output, regenerate your amine, and keep the carbon dioxide under control will require up to a third of the power from your power station. Not attractive. The next problem is, what to do with the carbon dioxide? Yes, some can be sunk into wells, preferably wet basaltic ones as this will fix the CO2, and a small amount could be used as a chemical, say to make polycarbonates, but how many power stations do you think will be accounted for by that?
The problem for climate change is that we currently burn about 9 Gt of carbon per annum, which means we have to fix/use something like 33 Gt of CO2 per annum just to break even, and breaking even is unlikely to fix this carbon problem. The problem is, CO2 is not a very strong greenhouse gas, but it does stay around in the atmosphere for a considerable time. One point that nobody seems to make in public is that even if we stopped emitting CO2 right now, the additional carbon we have already put in the atmosphere will remain for long enough to do a lot more damage. Everybody seems to behave as if we are in a rapid equilibrium, and that is not so. The Greenland ice sheet is the last relic of the last ice age. If we have created the net warming to melt so much per annum, that will keep going until the ice retreats to a position more resilient, at which point our climate will change significantly because we have a much different albedo over a large area. We cannot "fix" climate change by simply stopping the rate of increase of burning carbon; we have to actively reduce the total integrated amount, and not simply worry about the rate of increased production. I suggest that to fix the climate problem, assuming we see it as a problem, we would be better to put more effort into something with a stronger response than fixing CO2.
In the previous post, I attempted (unsuccessfully!) to irritate some people relating to how climate change research is spent. When money becomes available for this, what happens? What I believe happens is that we see numerous proposals for funding to make more accurate measurements of something. My argument is, just supposing we do get more accurate data on, say, the methane output of some swamp, what good does that do? It provides employment for those measuring the output of the swamp, but then what? Certainly it will add more to the literature, but the scientific literature is hardly short of material. Enough such measurements will help models account for what has happened, perhaps, but the one thing I am less confident about is whether such models will be able to answer the question, "Exactly what will happen if we do X?" For example, suppose we decided to try to raise the albedo of the planet by reflecting more light to space, and did this in a region that would lower the temperature of cold fronts coming into Greenland, with the aim of increasing snow deposition over Greenland, how much light would we need to reflect and where should we reflect it? My argument is, until models can give an approximate answer to that sort of question, they are useless. And unless we do something like geo-engineering, we are doomed to have to accommodate the change, because nobody has suggested any alternative that has the capacity to solve the problem. We can wave our hands and "feel virtuous" for claiming that we are doing something, but unless the sum of the somethings solves the problem, it is a complete waste of effort. Worse than that, such acts consume resources that could be better used to accommodate what will come. The only value of a model is to inform us which actions will be sufficient, and so far they cannot do that.
Posted by Ian Miller on Oct 14, 2013 10:13 PM BST
Currently, NASA is asking for public assistance for their astrobiology program, or they were up until the current government shutdown, and in particular, asking for suggestions as to where their program should be going. I think this is an extremely enlightened view, and I hope they receive plenty of good suggestions and take some of them up. This is a little different from the average way science gets funded, in which academic scientists put in applications for funds to pursue what they think is original. This is supposed to permit the uncovering of "great new advances", and in some areas, perhaps it does, but I rather suspect the most common outcome is to support what Rutherford dismissively called, "stamp collecting". You get a lot of publications, a lot of data, but there is no coherent approach towards answering "big questions". That, I think, is a strength of the NASA approach, and I hope other organizations take this up. For example, if we wish to address climate change, what questions do we really want to have answered? What we tend to get is, "Fund me to set up more data gathering," from those too uninspired to come up with something more incisive. We do not need more data to set the parameters so that current models better represent what we see; we need better models that will represent what will happen if we do or do not do X.
So what are the good questions for NASA to address? Obviously there are a very large number of them, but in my view, regarding biogenesis, I think there are some very important ones. Perhaps one of the most important one that has been pursued so far is how do the planets get their water, because if we want life on other planets, they have to have water. The water on the rocky planets is often thought to come from chondrites, as a "late veneer" on the planet. Now, one of the peculiarities of this explanation is that, as I argued in my ebook, Planetary Formation and Biogenesis, this explanation has serious problems. The first is, only a special class of chondrites contains volatiles; the bulk of the bodies from the asteroid belt do not. Further, the isotopes of the heavier elements are different from Earth, the ratios of different volatiles do not correspond to anything we see here or on the other planets, so why is such an explanation persisted with? The short answer is, for most there is no alternative.
My alternative is simple: the planets started accreting through chemical processes. Only solids could be accreted in reasonable amounts this close to the star, unless the body got big enough to hold gravitationally gases from the accretion disk. Water can be held as metal and silicon hydroxyl compound, the water subsequently being liberated. This, as far as I know, is the only mechanism by which the various planets can have different atmospheric compositions: different amounts of the various components were formed at different temperatures in the disk.
If that is correct, we would have a means of predicting whether alien planets could conceivably contain life. Accordingly, one way to pursue this would be to try to understand the high temperature chemistry of the dusts and volatiles expected to be in the accretion disk. That would involve a lot of work for which chemists alone would be suitable. Now, my question is, how many chemists have shown any interest in this NASA program? Do we always want to complain about insufficient research funds, or are we prepared to go out and do something to collect more?
Posted by Ian Miller on Oct 7, 2013 1:10 AM BST
Perhaps one of the more interesting questions is where did Earth's volatiles come from? The generally accepted theory is that Earth formed by the catastrophic collisions of planetary embryos (Mars-sized bodies), which effectively turned earth into a giant ball of magma, at which time the iron settled to the core though having a greater density, and took various siderophile elements with it. At this stage, the Earth would have been reasonably anhydrous. Subsequently, Earth got bombarded with chondritic material from the asteroid belt that was dislodged by Jupiter's gravitational field (including, in some models, Jupiter migrating inwards then out again), and it is from here that Earth gets its volatiles and its siderophile elements. This bombardment is often called "the late veneer". In my opinion, there are several reasons why this did not happen, which is where these papers become relevant. What are the reasons? First, while there was obviously a bombardment, to get the volatiles through that, only carbonaceous chondrites will suffice, and if there were sufficient mass to give that to Earth, there should also be a huge mass of silicates from the more normal bodies. There is also the problem of atmospheric composition. While Mars is the closest, it is hit relatively infrequently compared with its cross-section, and hit by moderately wet bodies almost totally deficient in nitrogen. Earth is hit by a large number of bodies with everything, but the Moon is seemingly not hit by wet bodies or carbonaceous bodies. Venus, meanwhile, is hit by more bodies that are very rich in nitrogen, but relatively dry. What does the sorting?
The first paper (Nature 501: 208 – 210) notes that if we assume the standard model by which core segregation took place, the iron would have removed about 97% of the Earth's sulphur and transferred it to the core. If so, the Earth's mantle should exhibit fractionated 34S/32S ratio according to the relevant metal-silicate partition coefficients, together with fractionated siderophile metal abundances. However, it is usually thought that Earth's mantle is both homogeneous and chondritic for this sulphur ratio,  consistent with the acquisition of sulphur  ( and other siderophile elements) from chondrites (the late veneer). An analysis of mantle material from mid-ocean ridge basalts displayed heterogeneous 34S/32S ratios that are compatible with binary mixing between a low 34S/32S  ambient mantle ratio and a high 34S/32S recycled component. The depleted end-member cannot reach a chondritic value, even if the most optimistic surface sulphur is added. Accordingly, these results imply that the mantle sulphur is at least partially determined by original accretion, and not all sulphur was deposited by the late veneer.
In the second (Geochim. Cosmochim. Acta 121: 67-83), samples from Earth, Moon, Mars, eucrites, carbonaceous chondrites and ordinary chondrites show variation in Si isotopes. Earth and Moon show the heaviest isotopes, and have the same composition, while enstatite chondrites have the lightest. A model of Si partitioning based on continuous planetary formation that takes into account T, P and oxygen fugacity variation during Earth's accretion. If the isotopic difference  results solely from Si fractionation during core formation, their model requires at least ~12% by weight Si in the core, which exceeds estimates based  on core density or geochemical mass balance calculations. This suggests one of two explanations: Earth's material started with heavier silicon, or (2) there is a further unknown process that leads to fractionation. They suggest vaporization following the Moon forming event, but would not this lead to lighter or different Moon material?
One paper (Earth Planet. Sci. Lett. 2013: 88-97) pleased me. My interpretation of the data related to atmospheric formation is that the gaseous elements originally accreted as solids, and were liberated by water as the planet evolved.  These authors showed that early early degassing of H2 obtained from reactions of water explains the "high oxygen fugacity" of the Earth's mantle. A loss of only 1/3 of an "ocean" of water from Earth would shift the oxidation state of the upper mantle from the very low oxidation state equivalent to the Moon, and if so, no further processes are required. Hydrogen is an important component of basalts at high pressure and, perforce, low oxygen fugacity. Of particular interest, this process may have been rapid. On the early Earth, over 5 times the amount of heat had to be lost as is lost now, and one proposal (501:501 - 504 ) heat pipe volcanism such as found on Io would manage this, in which case, the evolution of water and volatiles may have also been very rapid.
Finally, in (Icarus 226: 1489 -1498), near-infrared spectra show the presence of hydrated poorly crystalline silica with a high silica content on the western rim of Hellas. The surfaces are sporadically exposed over a 650 km section within a limited elevation range. The high abundances and lack of associated aqueous phase material indicate high water to rock ratios were present, but the higher temperatures that would lead to quartz were not present. This latter point is of interest because it is often considered that the water flows on Mars in craters were due to internal heating due to impact, such heat being retained for considerable periods of time. To weather basalt to make silica, there would have to be continuous water of a long time, and if the water was hot and on the surface it would rapidly evaporate, while if it was buried, it would stay super-heated, and presumably some quartz would result. This suggests extensive flows of cold water.
Posted by Ian Miller on Sep 30, 2013 3:30 AM BST
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