Support for a Predicted Mechanism!

What is the point of a scientific theory? The obvious one is that if you understand you can predict what will happen if you have reason to have that proposition present.  Unfortunately, you can lay down the principles and not make the specific prediction because you cannot foresee all the possible times it might be relevant. What sparked this thought is that about a decade ago I published an ebook called “Planetary Formation and Biogenesis”. The purpose of this was in part because the standard theory starts off by assuming that somehow things called planetesimals form. These were large asteroids, a few hundred km in size, and then these formed planets through their mutual gravity. However, nobody had any idea at all how these planetesimals formed; they were simply assumed as necessary on the assumption that gravity was the agent that formed the planets. On a personal level, I found this to be unsatisfactory.

I am restricting the following to what happens with icy bodies; the rocky ones are a completely different story. We start with highly dispersed dust because the heavy elements are formed in a supernova, in which these gases fly out at a very high speed. In one supernova, one hour after initiation, matter was flying out at 115,000 km/second, and it takes a long time to slow down. However, eventually it cools, gets embedded in a gas cloud and some chemical reactions take place. Most of the oxygen eventually reacts with something. All the more reactive elements like silicon or aluminium react, and the default for oxygen is to form water with hydrogen. The silicon, magnesium, calcium and aluminium oxides form solids, but they form one link at a time and cannot rearrange. This leaves a dispersion of particles that make smoke particles look large. If two such “particles” get close enough, because the chemical bonds are quite polar in these particular oxides, they attract each other and because they are reactive, they can join. This leads to a microscopic mass of tangled threads since each junction is formed on the exterior. So we end up with a very porous solid with numerous channels. These channels incorporate gases that are held to the channel surfaces. In the extreme cold of space, when these gases are brought close together on these surfaces they solidify to form ices. These solids filled with ices have been formed in the laboratory.

My concept of how icy bodies accrete goes like this. As the dust comes into an accretion disk where a star is forming, as it approaches the star it starts to warm. If particles collide at a temperature a little below the melting point of an ice they contain, the heat of collision melts the ice, the melt flows between the bodies then refreezes, gluing the bodies together. The good news is this has been demonstrated very recently in the laboratory for nanometer-sized grains of silicates coated with water ice (Nietadi et al., Icarus, (2020) 113996) so it works. As the dust gets warmer than said melting point, that ice sublimes out, which means there are four obvious different agents for forming planets through ices. In increasing temperatures these are nitrogen/carbon monoxide (Neptune and the Kuiper Belt); argon/methane (Uranus); methanol/ammonia/water (Saturn); and water (Jupiter). The good news is these planets are spread relatively to where expected, assuming the sun’s accretion disk was similar to others. So, in one sense I had a success: my theoretical mechanism gave planetary spacings consistent with observation, and now the initial mechanism of joining for very small-scale particles has been shown to work.

But there was another interesting point. Initially, when these fluffy pieces meet, they will join to give a bigger fluffy piece. This helps accretion because if larger bodies collide, the fluff can collapse, making the impact more inelastic and thus dispersing collisional energy. Given a reasonable number of significant collisions, the body will compact. If, however, there are some late gentle acquisitions of largish fluffy masses, that fluff will remain.Unfortunately, I did not issue a general warning on this, largely because nobody can think of everything, and also I did not expect that to be relevant to any practical situation now.  Rather unexpectedly, it was. You may recall that the European Space Agency landed the probe Philae on comet 67P/Churyumov–Gerasimenko, which made a couple of bounces and fell down a “canyon”, where it lay on its side. The interesting thing is the second “bounce” was not really a bounce. The space agency has been able to use the imprint of the impact to measure the strength of the ice, and  found it to be “softer than the lightest snow, the froth on your cappuccino or even the bubbles in your bubble bath.” This particular “boulder” on the outside of the comet is comprised of my predicted fluff. It feels good when something comes right. And had ESA read my ebook, maybe they would have designed Philae slightly differently.

Monarchic Growth of Giant Planets

In the previous post, I outlined the basic mechanism of how I thought the giant planets formed, and how their mechanism of formation put them at certain distances from the sun. Given that, like everyone else, I assign Jupiter to the snow point, in which case the other planets are where they ought to be. But that raises the question, why one planet in a zone? Let’s take a closer look at this mechanism.

In the standard mechanism, dust accretes into objects by some unknown mechanism, and does this essentially based on collision probability, and so the disk progresses with a distribution of roughly equal sized objects that collide under the same rules, and eventually become what is called planetesimals, which are about the size of the classical asteroid. (I say classical because as we get better at this, we are discovering a huge number of much smaller “asteroids”, and we have the problem of what does the word asteroid mean?) This process continues, and eventually we get Mars-sized objects called oligarchs, or embryos, then these collide to get planets. The size of the planet depends on how many oligarchs collide, thus fewer collided to make Venus than Earth, and Mars is just one oligarch. I believe this is wrong for four reasons: the first is, giants cannot grow fast enough; second, the dust is still there in 30 My old disks; the collision energies should break up the bodies at any given size because collisions form craters, not hills; the system should be totally mixed up, but isotope evidence shows that bodies seem to have accreted solely from the material at roughly their own distance from the sun.

There is an alternative called monarchic growth, in which, if one body can get a hundred times bigger than any of the others, it alone grows by devouring the others. For this to work, we need initial accretion to be possible, but not extremely probable from dust collisions. Given that we see disks by their dust that are estimated to be up to 30 My old, that seems a reasonable condition. Then, once it starts, we need a mechanism that makes further accretion inevitable, that is, when dust collides, it sticks. The mechanism I consider to be most likely (caveat – I developed it so I am biased) is as follows.

As dust comes into an appropriate temperature zone, then collisions transfer their kinetic energy into heat that melts an ice at the point of contact, and when it quickly refreezes, the dust particles are fused to the larger body. So accretion occurs a little below the melting temperature, and the probability of sticking falls off as the distance from that appropriate zone increases, but there is no sharp boundary. The biggest body will be in the appropriate zone because most collisions will lead to sticking, and once the body gets to be of an appropriate size, maybe as little as a meter sized, it goes into a Keplerian orbit. The gas and dust is going slower, due to gas drag (which is why the star is accreting) so the body in the optimal zone accretes all the dust and larger objects it collides with. Until the body gets sufficiently large gravitationally, collisions have low relative velocity, so the impact energy is modest.

Once it gets gravitationally bigger, it will accrete the other bodies that are at similar radial distance. The reason is that if everything is in circular orbits, orbits slightly further from the star have longer periodic times, in part because they move slightly slower, and in part because they have slightly further to go, so the larger body catches up with them and its gravity pulls the smaller body in. Unless it has exactly the same radial distance from the star, they will pass very closely and if one has enough gravity to attract the other, they will collide. Suppose there are two bodies at the same radial distance. That too is gravitationally unstable once they get sufficiently large. All interactions do not lead to collisions, and it is possible that one can be thrown inwards while the other goes outwards, and the one going in may circularise somewhere else closer to the star. In this instance, Ceres has a density very similar to the moons of Jupiter, and it is possible that it started life in the Jovian region, came inwards, and then finished accreting material from its new zone.

The net result of this is that a major body grows, while smaller bodies form further away, trailing off with distance, then there is a zone where nothing accretes, until further out there is the next accretion zone. Such zones get further away as you get further from the star because the temperature gradient decreases. That is partly why Neptune has a Kuiper Belt outside it. The inner planets do not because with a giant on each side, the gravity causes them to be cleaned out. This means that after the system becomes settled, a lot of residues start bombing the planet. This requires what could be called a “Great Bombardment”, but it means each system gets a bombardment mainly of its own composition, and there could be no significant bombardment with bodies from another system. This means the bombardment would have the same chemical composition as the planet itself.

Accordingly, we have a prediction. Is it right? It is hard to tell on Earth because while Earth almost certainly had such a bombardment, plate tectonics has altered the surface so much. Nevertheless, the fact the Moon has the same isotopes as Earth, and Earth has been churned but the Moon has not, is at least minor support. There is, of course, a second prediction. There seem to be many who assume the interior of the Jovian satellites will have much nitrogen. I predict very little. There will be some through adsorption of ammonia onto dust, and since ammonia binds more strongly than neon, then perhaps there will be very modest levels, but the absence of such material in the atmosphere convinces me it will be very modest.

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 ( )

will be available for 99 cents  as a special promo on (and 99p on 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, (  ) 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.