Evidence that the Standard Theory of Planetary Formation is Wrong.

Every now and again, something happens that makes you feel both good and depressed at the same time. For me it was last week, when I looked up the then latest edition of Nature. There were two papers (Nature, vol 541 (Dauphas, pp 521 – 524; Fischer-Gödde and Kleine, pp 525 – 527) that falsified two of the most important propositions in the standard theory of planetary formation. What we actually know is that stars accrete from a disk of gas and dust, the disk lingers on for between a million years and 30 million years, depending on the star, then the star’s solar winds clear out the dust and gas. Somewhere in there, planets form. We can see evidence of gas giants growing, where the gas is falling into the giant planet, but the process by which smaller planets or the cores of giants form is unobservable because the bodies are too small, and the dust too opaque. Accordingly, we can only form theories to fill in the intermediate process. The standard theory, also called oligarchic growth, explains planetary formation in terms of dust accreting to planetesimals by some unknown mechanism, then these collide to form embryos, which in turn formed oligarchs or protoplanets (Mars sized objects) and these collided to form planets. If this happened, they would do a lot of bouncing around and everything would get well-mixed. Standard computer simulations argue that Earth would have formed from a distribution of matter from further out than Mars to inside Mercury’s orbit. Earth the gets its water from a “late veneer” from carbonaceous chondrites from the far side of the asteroid belt.

It is also well known that certain elements in bodies in the solar system have isotopes that vary their ratio depending on the distance from the star. Thus meteorites from Mars have different isotope ratios from meteorites from the asteroid belt, and again both are different from rocks from Earth and Moon. The cause of this isotope difference is unclear, but it is an established fact. This is where those two papers come in.

Dauphas showed that Earth accreted from a reasonably narrow zone throughout its entire accretion time. Furthermore, that zone was the same as that which formed enstatite chondrites, which appear to have originated from a region that was much hotter than the material that, say, formed Mars. Thus enstatite chondrites are reduced. What that means is that their chemistry was such that there was less oxygen. Mars has only a small iron core, and most of its iron is as iron oxide. Enstatite chondrites have free iron as iron, and, of course, Earth has a very large iron core. Enstatite chondrites also contain silicates with less magnesium, which will occur when the temperatures were too hot to crystallize out forsterite. (Forsterite melts at 1890 degrees C, but it will also dissolve to some extent in silica melts at lower temperatures.) Enstatite chondrites also are amongst the driest, so they did not provide Earth’s water.

Fischer-Gödde and Kleine showed that most of Earth’s water did not come from carbonaceous chondrites, the reason being, if it did, the non-water part would have added about 5% to the mass of Earth, and the last 5% is supposed to be from where the bulk of elements that dissolve in hot iron would have come from. The amounts arriving earlier would have dissolved in the iron and gone to the core. One of those elements is ruthenium, and the isotope ratios of Earth’s ruthenium rule out an origin from the asteroid belt.

Accordingly, this evidence rules out oligarchic growth. There used to be an alternative theory of planetary accretion called monarchic growth, but this was soon abandoned because it cannot explain first why we have the number of planets we have where they are, and second where our water came from. Calculations show it is possible to have three to five planets in stable orbit between Earth and Mars, assuming none are larger than Earth, and more out to the asteroid belt. But they are not there, so the question is, if planets only grow from a narrow zone, why are these zones empty?

This is where I felt good. A few years ago I published an ebook called “Planetary Formation and Biogenesis” and it required monarchic growth. It also required the planets in our solar system to be roughly where they are, at least until they get big enough to play gravitational billiards. The mechanism is that the planets accreted in zones where the chemistry of the matter permitted accretion, and that in turn was temperature dependent, so specific sorts of planets form in zones at specific distances from the star. Earth formed by accretion of rocks formed during the hot stage, and being in a zone near that which formed enstatite chondrites, the iron was present as a metal, which is why Earth has an iron core. The reason Earth has so much water is that accretion occurred from rocks that had been heat treated to about 1550 degrees Centigrade, in which case certain aluminosilicates phase separated out. These, when they take up water, form cement that binds other rocks to form a concrete. As far as I am aware, my theory is the only current one that requires these results.

So, why do I feel depressed? My ebook contained a review of over 600 references from journals until a few months before the ebook was published. The problem is, these references, if properly analysed, provided papers with plenty of evidence that these two standard theories were wrong, but each of the papers’ conclusions were ignored. In particular, there was a more convincing paper back in 2002 (Drake and Righter, Nature 416: 39-44) that came to exactly the same conclusions. As an example, to eliminate carbonaceous chondrites as the source of water, instead of ruthenium isotopes, it used osmium isotopes and other compositional data, but you see the point. So why was this earlier work ignored? I firmly believe that scientists prefer to ignore evidence that falsifies their cherished beliefs rather than change their minds. What I find worse is that neither of these papers cited the Drake and Righter paper. Either they did not want to admit they were confirming a previous conclusion, or they were not interested in looking thoroughly at past work other than that which supported their procedures.

So, I doubt these two papers will change much either. I might be wrong, but I am not holding my breath waiting for someone with enough prestige to come out and say enough to change the paradigm.

Origin of life, and a challenge!

Here is a chance to test yourself as a theoretician. But do not worry if you cannot solve this. Most people will not, and I predict nobody will, but prove me wrong! And as a hint, while nobody actually knows the answer, as I shall show eventually, getting a very reasonable answer is actually relatively simple, although you need a little background knowledge for the first question.

Just before Christmas, I posted with the title Biogenesis: how did life get started?” (http://wp.me/p2IwTC-6e ) but as some may have noticed, I did not get very far along the track indicated by the title. The issue is, of course, somewhat complicated, and it is easier to discuss it in small pieces I also mentioned I was about to give a talk on this early this year. Well, the talk will come on March 4, so it is approaching quickly. Accordingly, I have put out an abstract, and am including two challenges, which readers here may or may not wish to contemplate. Specifically,
1. Why did nature choose ribose for nucleic acids?
2. How did homochirality arise?
Put your guesses or inspired knowledgeable comments at the end of this post. The answers are not that difficult, but they are subtle. In my opinion, they are also excellent examples of how to go about forming a theory. I shall post my answers in due course.

The question of, why ribose, is a little complicated and cannot be answered without some chemical knowledge, so most readers probably won’t be able to answer that. Notwithstanding that, it is a very interesting question because I believe it gives a clue as to how life got underway. RNA is a polymer in which each mer is made up of three entities: one of four nucleobases, ribose and a phosphate ester. The nucleobase is attached to C-1 of ribose (if you opened it up, at the aldehyde end) and the phosphate is at C-5 (the other end, ribose being a five carbon sugar. The nucleobases are, in general, easy to make. If you leave ammonium cyanide lying around, they make themselves, but that is the only thing that appears to be easy about this entity. Sugars can be made in solution by having formaldehyde, which is easily made, react in water with lime, and a number of other solids. That seems easy, except that when you do this, you do not get much, if any, ribose. The reason is, ribose is a high-energy pentose (five carbon sugar) because all the hydroxyl groups are eclipsing each other in the closest orientation (axial, for those who know some chemistry). In the laboratory, double helix nucleobases (duplexes) have been made from xylose and arabinose, and in many ways these have superior properties to ribose, but nature chose ribose, so the question is, why? Not only did it do it for RNA, but the unit adenine – ribose – phosphate turns up very frequently.

Adenine combined with ribose is usually called adenosine, and the adenosine phosphate linkage turns up in the energy transfer chemical ATP (adenosine tripolyphosphate), the reduction oxidation catalysts NAD and FAD, where the AD stands for adenosine diphosphate, and in a number of enzyme cofactors, to give solubility in water. Giving solubility in water is an obvious benefit, but putting a sugar unit on the group would also do that. Giving an electric charge would also be of benefit, because it helps keep the entity in the cell, nevertheless there are also other ways of doing that. You may say, well, it had to choose something, but recall, ribose is hard to make, so why was it selected for so many entities?

The phosphate ester also causes something of a problem. In the laboratory, phosphate esters are usually made with highly reactive phosphorus-based chemicals, but life could not have started that way. Another way to form phosphate esters is to heat a phosphate and an alcohol (including the hydroxyl groups on a sugar) to about 180 oC, when water is driven off. Note that if water is around, as in the undersea thermal vents that are often considered to be the source of life, the superheated water converts phosphate esters to phosphate and alcohol groups. Life did not start at the so-called black smokers, although with sophisticated protection mechanisms, it has evolved to tolerate such environments. Another problem with phosphate is that phosphates are insoluble in neutral or alkaline water, and phosphate esters hydrolyse in acidic water.
However, notwithstanding the difficulty with using phosphate, there is no real choice if you want a linking agent with three functions (two used up to join two groups, one to be ionic to enhance water solubility). Boron is rare, and has unusual chemistry, while elements such as arsenic, besides being much less common, do not give bonds with as much strength.

Homochirality is different matter. (Chirality can be though of like handedness. If you have gloves, your left hand has its glove and the right hand its, even though they are identical in features, such as four fingers and a thumb. The handedness comes from the fact you cannot put those fingers and thumb on a hand where the top differs from the bottom without making the right hand different from the left.) The sugars your body uses are D sugars (think of this as right handed) while all your amino acids are L, or left handed. The problem is, when you synthesis any of these through any conceivable route given the nature of the starting materials, which have no chirality, you get an equal mix of D and L. How did nature select one lot and neglect the others?
Put your guesses below! In the meantime, my ebook, “Planetary formation and biogenesis”, which summarizes what we knew up to about 2012, is going to be discounted on Amazon for a short period following March 6. This is to favour those going to my talk, but you too can take advantage. It has a significant scientific content (including an analysis of over 600 scientific papers) so if your scientific knowledge is slight, it may be too difficult.

Theory and planets: what is right?

In general, I reserve this blog to support my science fiction writing, but since I try to put some real science in my writing, I thought just once I would venture into the slightly more scientific. As mentioned in previous posts, I have a completely different view of how planets, so the question is, why? Surely everyone else cannot be wrong? The answer to that depends on whether everyone goes back to first principles and satisfies themselves, and how many lazily accept what is put in front of them. That does not mean that it is wrong, however. Just because people are lazy merely makes them irrelevant. After all, what is wrong with the standard theory?

My answer to that is, in the standard theory, computations start with a uniform distribution of planetesimals formed in the disk of gas from which the star forms. From then on, gravity requires the planetesimals to collide, and it is assumed that from these collisions, planets form. I believe there are two things wrong with that picture. The first is, there is no known mechanism to get to planetesimals. The second is that while gravity may be the mechanism by which planets complete their growth, it is not the mechanism by which it starts. The reader may immediately protest and say that even if we have no idea how planetesimals form, something had to start small and accrete, otherwise there would be no planets. That is true, but just because something had to start small does not mean there is a uniform distribution throughout the accretion disk.

My theory is that it is chemistry that causes everything to start, and different chemistries occur at different temperatures. This leads to the different planets having different properties and somewhat different compositions.

The questions then are: am I right? does it matter? To the first, if I am wrong it should be possible to falsify it. So far, nobody has, so my theory is still alive. Whether it matters depends on whether you believe in science or fairy stories. If you believe that any story will do as long as you like it, well, that is certainly not science, at least in the sense that I signed up to in my youth.

So, if I am correct, what is the probability of finding suitable planets for life? Accretion disks last between 1 to even as much as 30 My. The longer the disk lasts, the longer planets pick up material, which means the bigger they are. For me, an important observation was the detection of a planet of about six times Jupiter’s mass that was about three times further from its star (with the name LkCa 15) than Jupiter. The star is approximately 2 My old. Now, the further from the star, the less dense the material, and this star is slightly smaller than our sun. The original computations required about 15 My or more to get Jupiter around our star, so they cannot be quite correct, although that is irrelevant to this question. No matter what the mechanism of accretion, Jupiter had to start accreting faster than this planet because the density of starting material must be seriously greater, which means that we can only get our solar system if the disk was cleared out very much sooner than 2 My. People ask, is there anything special regarding our solar system? I believe this very rapid cleanout of the disk will eliminate the great bulk of the planetary systems. Does it matter if they get bigger? Unfortunately, yes, because the bigger the planets get, the bigger the gravitational interactions between them, so the more likely they are to interact. If they do, orbits become chaotic, and planets can be eliminated from the system as other orbits become highly elliptical.

If anyone is interested in this theory, Planetary Formation and Biogenesis (http://www.amazon.com/dp/B007T0QE6I )

will be available for 99 cents  as a special promo on Amazon.com (and 99p on Amazon.co.uk) on Friday 13, and it will gradually increase in price over the next few days. Similarly priced on Friday 13 is my novel Red Gold, (http://www.amazon.com/dp/B009U0458Y  ) which is about fraud during the settlement of Mars, and as noted in my previous post, is one of the very few examples of a novel in which a genuine theory got started.

Terraforming Mars

In the 1990s, there was much speculation about terraforming planets, particularly Mars. The idea was that the planet could be converted into something like Earth. To make Mars roughly like Earth, the temperature has to be raised by about ninety Centigrade degrees, atmospheric pressure has to be raised by something approaching a hundred times present pressure, and a lot of water must be found. That presumably comes from buried ice, so besides uncovering it, an enormous amount of heat is required to melt it. The reason Mars is colder is that the sun delivers half the power to Mars than Earth, due to Mars being further away. The gas pressure depends on two things. The first is there has to be enough material, and the second is we have to get it into the gas phase. The most obvious gas is carbon dioxide, because as dry ice, it could be in the solid state, but would be amenable to heating. The problem is, if carbon dioxide is present with a lot of water, it will be absorbed by the water, particularly cold water, and slowly turned into material like dolomite. Nitrogen is the major gas in our atmosphere, but that would be a gas on Mars, and there is very little in the Martian atmosphere.

Why did anyone ever think Terraforming was possible? One reason may be that about 3.6 Gy ago (a gigayear is a thousand million years) it was thought that there were huge rivers on Mars. The Viking images found a huge number of massive river valleys, and so it was thought there had to be sufficient temperatures to melt the water. Subsequent information has suggested that these rivers did not persist over a prolonged wet period, but rather there were intermittent periods where significant flows occurred.  Such rivers probably never flowed for more than a million years or so, and while a million years might seem to be an extremely long period to us, it is trivial in the life of the solar system. Nevertheless the rivers meandered for that period, which is at least suggestive that they were relatively stable for that time, so what went wrong?

When I wrote Red Gold, I needed the major protagonist to make an unexpected discovery to expose a fraud, and it was then that I had an idea. The average temperature on Mars now is -80 degrees C, and while we could imagine some sort of greenhouse effect warming the early Mars, the sun only emitted about two-thirds the energy it does now, so temperature would have been a more severe problem. To me, it was inconceivable that the temperature could get sufficiently above the melting point of ice to give significant flows, but there is one way to make water liquid at -80 degrees C, and that is to have ammonia present. If the volcanoes gave off ammonia as well as water, that would give some greenhouse gas, and the carbon would be present as methane, this being what is called a reducing atmosphere. Sunlight tends to act with water to oxidize things, giving off hydrogen that escapes to space. This has happened extensively on Mars, indeed at many sites where chloride has been deposited on the surface, it has been converted to perchlorate. So methane would oxidize to carbon dioxide, and carbon dioxide would react with ammonia to make first, ammonium carbonate, then, given heat or time, urea. So my “unexpected discovery” was the fertilizer that would make the settlement of Mars possible. I had something that I thought would make my plot plausible.

Funnily enough, this thought took on a life of its own; the more I thought about it, the more I liked it, because it helps to explain, amongst other things, how life began. (The reduced form of nitrogen is a set of compound called nitrides. Water on nitrides, plus heat, makes ammonia, and also cyanide, which is effectively carbon nitride.) Standard theory, of course, assumes that nitrogen was always emitted as the nitrogen gas we have in our atmosphere. Of course you might think that all the scientists are right and I am wrong. Amongst others, Carl Sagan calculated that if ammonia was emitted into the atmosphere, it would be removed by sunlight in a matter of a decade or so, and he had to be right, surely? Well, no. Anyone can be wrong. (Of course you may say some, such as me, are more likely to be wrong than others!) However, in this case I maintain that Sagan was wrong because he overlooked something: ammonia dissolves in water at a very fast rate, and in water it will be protected to some extent. To justify that, we have found rocks on Earth that are 3.2 billion years old and that have samples of seawater enclosed, and these drops of seawater have very high levels of ammonia. These levels are sufficiently high that about 10% of Earth’s nitrogen must have been dissolved in the sea as ammonia at the time, and that is after the Earth had been around for about 500 million years after the water flowed on Mars.

If anyone is interested in why I think this occurred, Red Gold has an appendix where my first explanation is given in simple language. For those who want something a bit more detailed, together with a review of several hundred scientific papers, you could try my ebook, Planetary Formation and Biogenesis.