How Did We Escape the RNA World?

In my ebook “Planetary Formation and Biogenesis” I argue that life had to start with nucleic acids because only nucleic acids can provide a plausible mechanism for reproduction, and, of course, that is exactly what they do now – they reproduce. The RNA world may not qualify as life as more is required, but if this step is not achieved there can be no life. The first reproducing agent had to be RNA because ribose is the only sugar that occurs at least partially in a furanose form. (The furanose is a five-membered ring; the pyranose is a six-membered ring and is generally more stable.) Why do we need the furanose? In my ebook I show various reasons, but the main one is that the only plausible experiment so far to show phosphate esters could have formed naturally lead to AMP and ATP. While the ribose is only about 20% furanose, NO pyranose formed phosphate esters.

Later, DNA was used primarily for reproduction for a very simple reason: it uses 2-deoxyribose. The removal of the 2-hydroxyl from ribose makes the polymer several orders of magnitude more stable. So why did this not be part of the starting mix? Leaving aside the fact we do not really know how to get 2-deoxyribose in any synthesis that could reasonably have happened in some sort of pond without help (complicated laboratory chemical syntheses are out!) there is a more important reason: at the beginning high accuracy in reproduction is undesirable. The first such life forms (i.e. things that reproduce) are not going to be very useful. They were chosen at random and should have all sorts of defects. What we need is rapid evolution, and we are more likely to get that from something that mutates more often. Further, RNA can act as a catalyst, which speeds up- everything.

Bonfio (Nature, 605, p231-2) raises two questions. The first borders on silly: why did proteins as enzymes replace most of RNA catalytic activity? The short answer is they are immensely better. They speed things up by factors of billions, and they are stable, so they can be reused over and over again. So why did they not arise immediately? Consider the enzyme that degrades protein; it has 315 properly sequenced amino acids. If we limit ourselves to 20 different ones, and allow for the initial ones being either left- or right-handed, except for glycine, the probability of random selection is 2 in 39^315. That is, 39 multiplied by itself 315 times. To put that in perspective, there are just 10^85 elementary particles in the visible universe. It was simply impossible. But that raises the second, and extremely interesting question: how could ordered protein selection emerge with such horrendous odds against?

What happens now is that messenger RNA has three nucleotide sequences “recognized” and “transfers” this information to transfer RNA which selects an amino acid and attaches it to the growing chain, then goes back to the messenger RNA to get the next selection information. That is grossly oversimplified, but you might get the picture. The question is, how could this emerge? The answer appears to include non—canonical nucleotides. RNA comprises mainly adenine, guanine, cytosine and uracil, and these are the “information” holders, but there are some additional entities present. One is adenosine with a threonylcarbamoyl group attached. The details are not important at this level – merely that there is something additional there. The important fact is there is no phosphate linkage so this is not in the chain. At first sight, these are bad because they block chain formation. Thus for every time this hydrogen-bonded to a uracil, say, it would block the chain synthesis and stop reproduction. However, it turns out that they may assist peptide synthesis. The non-canonical nucleotide at the terminal point of a RNA strand attracts amino acids. This becomes a donor strand, and it transfers to a similar RNA with a nascent peptide, and we have ordered synthesis. It is claimed that this can be made to happen under conditions that could plausibly occur on Earth. The peptide synthesis involves the generation of a chimeric peptide – RNA intermediate, perhaps the precursor of the modern ribosome. Of course, we are still a long way from an enzyme. However, we have (maybe) located how the peptides could be synthesised in non-random way, and from the RNA we can reproduce a useful sequence, but we are still a very long way from the RNA knowing what sequences will work. The assumption is, they will eventually self-select, based on Darwinian principles, but that would be a slow and very inefficient process. However, as I note in the ebook, the early peptides with no catalytic properties are not necessarily wasted. The most obvious first use would be to incorporate them in the cell wall, which would permit the formation of channels able to bring in fresh nutrients and get rid of excess water pressure. The evolution of life probably a very long time during which much stewing and testing was carried out until something sufficiently robust evolved.

The First Atmosphere

Ι have now published the second edition of my ebook “Planetary Formation and Biogenesis”. It has just under 1290 references, each about a different aspect of the issue, although there is almost certainly a little double counting because references follow chapters, and there will be some scientific papers that are of sufficient importance to be mentioned in two chapters. Nevertheless, there is plenty of material there. The reason for a second edition is that there has been quite a lot of additional; information from the past decade. And, of course, no sooner did I publish than something else came out, so I am going to mention that in this post. In part this is because it exemplifies some of what I think is wrong with modern science. The paper, for those interested, is from Wilcoski et al. Planet Sci J. 3: 99. It is open access so you can read it.

First, the problem it attempts to address: the standard paradigm is that Earth’s atmosphere was initially oxidised, and comprised carbon dioxide and nitrogen. The question then is, when did this eventuate? What we know is the Earth was big enough that if still in the accretion disk it would have had an atmosphere of hydrogen and helium. If it did not accrete until after the disk was expelled, it would have no atmosphere initially, and an atmosphere had to come from some other process. The ebook shows the evidence and in my opinion it probably had the atmosphere of hydrogen. Either way, the accretion disk gets expelled, and assuming our star was the same as others, for the first few hundred million years the star gave off a lot of extremely energetic UV radiation, and that would be sufficient to effectively blow any atmosphere away. So under that scenario, for some number of hundred million years there would be no atmosphere.

There is an opposing option. Shortly after the Moon-forming event, there would be a “Great Bombardment” of massive impactors. There are various theories this would form a magma ocean and there is a huge steam atmosphere, but there is surprisingly little evidence for this, which many hold onto no matter what. The one piece of definite evidence are some zircons from the Jack Hills in Australia, and these are about 4.2 – 4.3 billion years old – the oldest of any rock we have. Some of these zircons show clear evidence that they formed under temperatures not that different from today. In particular, there was water that had oxygen isotope ratios expected of water that had come from rain.

So, let me revisit this paper. The basic concept is that the Earth was bombarded with massive asteroids and the iron core hit the magma ocean, about half of it was sent into the atmosphere (iron boils at 2861 degrees C) where it reacted with water to form hydrogen and ferrous oxide. The hydrogen reacted with nitrogen to form ammonia.

So, what is wrong with that? First, others argue that iron in the magma ocean settles to the core. That, according to them, is why we have a core. Alternatively, others argue if it comes from an asteroid, it emulsifies in the magma. Now we have the iron doing three different kind of things depending on what answer you want. It can do one of them, but not all of them. Should iron vapour get into the atmosphere, it would certainly reduce steam and make hydrogen, but then the hydrogen would not do very much, but rather would be lost to space because of the sun’s UV. The reaction of hydrogen with nitrogen only proceeds to make much ammonia when there is intense pressure. That could happen deep underground. However, in atmospheric pressure at temperatures above the boiling point of iron, ammonia would immediately dissociate and form nitrogen and hydrogen. The next thing that is wrong is that very few asteroids have an iron core. If one did, what would happen to the asteroid when it hit magma? As an experiment, throw ice into water and watch what happens before it tries to reverse its momentum and float (which an asteroid would not do). Basically, the liquid is what gets splashed away. Rock is a very poor conductor of heat, so the asteroid will sink quite deeply into the liquid and will have to melt off the silicates before the iron starts to melt, and then, being denser, it will sink to the core. On top of that it was assumed the atmosphere contained 100 bars of carbon dioxide, and two bars of nitrogen, in other words an atmosphere somewhat similar to that of Venus today. Assuming what was there to get the answer you want is, I suppose, one way of going about things, in a circular sort of way. However, with tidal heating from a very close Moon, such an atmosphere with that much water would never rain, which contradicts the zircon data. What we have is a story that contradicts the very limited physical evidence we have, which has no evidence in favour of it, and was made up to get the answer wanted so they could explain where the chemicals that formed life might have come from. Needless to say, my ebook has a much better account, and has the advantage that no observations contradict it.

Some Scientific Curiosities

This week I thought I would try to be entertaining, to distract myself and others from what has happened in Ukraine. So to start with, how big is a bacterium? As you might guess, it depends on which one, but I bet you didn’t guess the biggest. According to a recent article in Science Magazine (doi: 10.1126/science.ada1620) a bacterium has been discovered that lives in Caribbean mangroves that, while it is a single cell, it is 2 cm long. You can see it (proposed name, Thiomargarita magnifica) with the naked eye.

More than that, think of the difference between prokaryotes (most bacteria and single-cell microbes) and eukaryotes (most everything else that is bigger). Prokaryotes have free-floating DNA while eukaryotes package their DNA nucleus and put various cell functions into separate vesicles and can move molecules between the vesicles. But this bacterium cell includes two membrane sacs, only one of which contains DNA. The other sac contains 73% of the total volume and seems to be filled with water. The genome was nearly three times bigger than those of most bacteria.

Now, from Chemistry World. You go to the Moon or Mars, and you need oxygen to breathe. Where do you get it from? One answer is electrolysis, so do you see any problems, assuming you have water and you have electricity? The answer is that it will be up to 11% less efficient. The reason is the lower gravity. If you try to electrolyse water at zero g, such as in the space station, we knew it was less efficient because the gas bubbles have no net force on them. The force arises through different densities generating a weight difference, and the lighter gas rises, but in zero g, there is no lighter gas – they might have different masses, but they all have no weight. So how do they know this effect will apply on Mars or the Moon? They carried out such experiments on board free-fall flights with the help of the European Space Agency. Of course, these free-fall experiments are somewhat brief as the pilot of the aircraft will have this desire not to fly into the Earth.

The reason the electrolysis is slower is because gas bubble desorption is hindered. Getting the gas off the electrodes occurs because there are density differences, and hence a force, but in zero gravity there is no such force. One possible solution being considered is a shaking electrolyser. Next thing we shall see is requests for funding to build different sorts of electrolysers. They have considered using them in centrifuges to construct models to compute what the lower gravity would do, but an alternative might be to have such a process operating within a centrifuge. It does not need to be a fast spinning centrifuge as all you are trying to do is to generate the equivalent of 1 g, Also, one suggestion is that people on Mars or the Moon might want to spend a reasonable fraction of their time inside one such large centrifuge, to help keep the bone density up.

The final oddity comes from Physics World. As you may be aware, according to Einstein’s relativity, time, or more specifically, clocks, run slower as the gravity increases. Apparently this was once tested by taking a clock up a mountain and comparing it with one kept at the base, and General Relativity was shown to predict the correct result. However, now we have improved clocks. Apparently the best atomic clocks are so stable they would be out by less than a second after running for the age of the universe. This precision is astonishing. In 2018 researchers at the US National Institute for Standards and Technology compared two such clocks and found their precision was about 1 part in ten to the power of eighteen. It permits a rather astonishing outcome: it is possible to detect the tiny frequency difference between the two clocks if one is a centimeter higher than the other one. This will permit “relativistic geodesy”, which could be used to more accurately measure the earth’s shape, and the nature of the interior, as variations in density outcrops would cause minute changes in gravitational potential. Needless to say, there is a catch: they may be very precise but they are not very robust. Taking them outside the lab leads to difficulties, like stopping.

Now they have done better – using strontium atoms, uncertainty to less that 1 part in ten to the power of twenty! They now claim they can test for quantum gravity. We shall see more in the not too distant future.

Your Water Came from Where?

One interesting question when considering why Earth has life is from where did we get our water? This is important because essentially it is the difference between Earth and Venus. Both are rocky planets of about the same size. They each have similar amounts of carbon dioxide, with Venus having about 50% more than Earth, and four times the amount of nitrogen, but Venus is extremely short of water. If we are interested in knowing about whether there is life on other planets elsewhere in the cosmos, we need to know about this water issue. The reason Venus is hell and Earth is not is not that Venus is closer to the Sun (although that would make Venus warmer than Earth) but rather it has no water. What happened on Earth is that the water dissolved the CO2 to make carbonic acid, which in turn weathered rocks to make the huge deposits of lime, dolomite, etc that we have on the planet, and to make the bicarbonates in the sea.

One of the more interesting scientific papers has just appeared in Nature Astronomy ( although the reason I find it interesting may not meet with the approval of the authors. What the authors did was to examine a grain of the dust retrieved from the asteroid Itokawa by the Japanese Space agency and “found it had water on its surface”. Note it had not evaporated after millions of years in a vacuum. The water is produced, so they say, by space weathering. What happens is that the sun sends out bursts of solar wind which contains high velocity protons. Space dust is made of silicates, which involve silica bound to four oxygen atoms in a tetrahedron, and each oxygen atom is bound to something else. Suppose, for sake of argument, the something else is a magnesium atom. A high energy hydrogen nucleus (a proton) strikes it and makes SiOH and, say Mg+, with the Mg ion and the silicon atom remaining bound to whatever else they were bound to. It is fairly standard chemistry that 2SiOH → SiOSi plus H2O, so we have made water. Maybe, because the difference between SiOH on a microscopic sample of dust and dust plus water is rather small, except, of course, Si-OH is chemically bound to and is part of the rock, and rock does not evaporate. However, the alleged “clincher”: the ratio of deuterium to hydrogen on this dust grain was the same as Earth’s water.

Earth’s water has about 5 times more deuterium than solar hydrogen, Venus about a hundred times. The enhancement arises because if anything is to break the bond in H-O-D, the hydrogen is slightly more probable to go because the deuterium has a slightly stronger bond to the oxygen. Also, being slightly heavier, H-O-D is slightly less likely to get to the top of the atmosphere.

So, a light bulb moment: Earth’s water came from space dust. They calculate that this would produce twenty litres of water for every cubic meter of rock. This dust is wet! If that dust rained down on Earth it would deliver a lot of water. The authors suggest about half the water here came that way, while the rest came from carbonaceous chondrites, which have the same D/H ratio.

So, notice anything? There are two problems when forming a theory. First, the theory should account for everything of relevance. In practice this might be a little much, but there should be no obvious problems. Second, the theory should have no obvious inconsistencies. First, let us look at the “everything”. If the dust rained down on the Earth, why did not the same amount rain down on Venus? There is a slight weakness in this argument because if it did, maybe the water was largely destroyed by the sunlight. If that happened a high D/H ratio would result, and that is found on Venus. However, if you accept that, why did Earth’s water not also have its D/H ratio increased? The simplest explanation would be that it did, but not to extent of Venus because Earth had more water to dilute it. Why did the dust not rain down on the Moon? If the answer is the dust had been blown away by the time the Moon was formed, that makes sense, except now we are asking the water to be delivered at the time of accretion, and the evidence on Mars was that water was not there until about 500 million years later. If it arrived before the disk dust was lost, then the strongest supply of water would come closest to the star, and by the time we got to Earth, it would be screened by inner dust. Venus would be the wettest and it isn’t.

Now the inconsistencies. The strongest flux of solar wind at this distance would be what bombards the Moon, and while the dust was only here for a few million years, the Moon has been there for 4.5 billion years. Plenty of time to get wet. Except it has not. The surface of the dust on the Moon shows this reaction, and there are signs of water on the Moon, especially in the more polar regions, and the average Moon rock has got some water. But the problem is these solar winds only hit the surface. Thus the top layer or so of atoms might react, but nothing inside that layer. We can see those SiOH bonds with infrared spectroscopy, but the Moon, while it has some such molecules, it cannot be described as wet. My view is this is another one of those publications where people have got carried away, more intent on getting a paper that gets cited for their CV than actually stopping and thinking about a problem.

Where did a Nervous System Come From?

Ever wondered how a nervous system evolved, and how we evolved to get around to thinking? If you do think about it, at first sight it is not obvious how it evolved; what caused it? The point about evolution is that it progresses in tiny steps, so what could possibly be a step towards a nervous system? It has to be something really simple that a minor change from the first simple organism that feeds and reproduces, BUT it has to do something that gives it an advantage, so the question comes down to what could that be?

The first thing to note is that there would be little point in a single-cell creature developing such a system. The point of a nervous system is to coordinate the activities of different parts of the whole, but a single cell is sufficiently small that coordination is unnecessary. Notwithstanding that, there may be an advantage for a single cell to sense whether there are nutrients nearby. The first such cells would simply absorb, but if it could sense when there were nutrients or not, it would have a better way of knowing whether to reproduce. That could arise initially with nothing more than having two activities. Microalgae show such an extremely primitive sensing. If a microalga has a good supply of nitrogen, it makes nucleic acid as fast as it  can, together with some protein, and these are just what it needs to reproduce. If it is nitrogen starved, it cannot turn off its photosynthesis mechanism so it takes CO2 from the air and makes lipids. It just swells up with fat! If it cannot get nitrogen nutrients for a prolonged time, it bloats and dies.

According to Musser et al. 2021 (Science 374: 717 – 723) a clue to how the nervous system evolved comes from sponges. Sponges are an animal clade that lack neurons, muscles or a gut, so they are rather simple. They have canals for filter feeding and waste removal and they have cilia that drive water flow. Yet despite this simple structure, they perform whole-body contractions that can expel debris, and while they have no integrated signalling functions, nevertheless they have genetic material usually found in nerves and muscles. Apparently sponges can use an intricate cell communication system to regulate their feeding and potentially eliminate invading bacteria. They do not have neurons, but they have genes that encode proteins to help transmit chemical signals, which could be regarded as an initial move towards a nervous system.

The sponge that was studied has 18 distinct cell types and synaptic genes (i.e. potentially capable of transmitting a signal) were active in some of the cells that were clustered around the digestive chambers.

They then showed that some such cells send out long arms to contact the cells with hair-like protrusions that drive the water flow systems. In other words, there is something there made of protein that starts where food is digested and stretches to the cells that control the flow of water, thus either telling these cells to send more food or alternatively to clear out the debris from previous digestion. It is important to note that these connectors are not nerves and it is not a rapid communication. Nevertheless, a system that could tell when it was time to get rid of debris from the region where it digests would be an evolutionary advantage over those that could not, and would hence take a greater percentage of the food and reproduce faster. Eventually it would predominate, especially those specimens that could do it a little better than the others. Over the generations the system would gradually predominate. It should also be noted that this does not mean we evolved from a sponge. This sort of behaviour could have started many times in different families. The point is, there is a distinct advantage when developing multi-celled creatures for one end to let another end know that it would like more food, or that it is flooded with debris. Obviously, this is a long way from a nervous system. The next evolutionary step would probably be to do it faster in larger multi-celled species. However, the means of sensing food would be the first prerequisite for sending messages to help digestion; it is not just the ability to send messages, but the message must have some sensible relevance. Food (or nutrient acquisition) would be the first reason to communicate across cells. Whether this was really how a nervous system started is debatable, but at least it makes sense.

Where to Look for Alien Life?

One intriguing question is what is the probability of life elsewhere in the Universe? In my ebook, “Planetary Formation and Biogenesis” I argue that if you need the sort of chemistry I outline to form the appropriate precursors, then to get the appropriate planet in the habitable zone your best bet is to have a G-type or heavy K-type star. Our sun is a G-type. While that eliminates most stars such as red dwarfs, there are still plenty of possible candidates and on that criterion alone the universe should be full of life, albeit possibly well spread out, and there may be other issues. Thus, of the close stars to Earth, Alpha Centauri has two of the right stars, but being a double star, we don’t know whether it might have spat out its planets when it was getting rid of giants, as the two stars come as close as Saturn is to our sun. Epsilon Eridani and Tau Ceti are K-type, but it is not known whether the first has rocky planets, and further it is only about 900 million years old so any life would be extremely primitive. Tau Ceti has claims to about 8 planets, but only four have been confirmed, and for two of these, one gets about 1.7 times Earth’s light (Venus get about 1.9 times as much) while the other gets about 29%. They are also “super Earths”. Interestingly, if you apply the relationship I had in my ebook, the planet that gets the most light, is the more likely to be similar geologically to Earth (apart from its size) and is far more likely than Venus to have accreted plenty of water, so just maybe it is possible.

So where do we look for suitable planets? Very specifically how probable are rocky planets? One approach to address this came from Nibauer et al. (Astrophysical Journal, 906: 116, 2021). What they did was to look at the element concentration of stars and picked on 5 elements for which he had data. He then focused on the so-called refractory elements, i.e., those that make rocks, and by means of statistics he separated the stars into two groups: the “regular” stars, which have the proportion of refractory elements expected from the nebular clouds, or a “depleted” category, where the concentrations are less than expected. Our sun is in the “depleted” category, and oddly enough, only between 10 – 30% are “regular”. The concept here is the stars are depleted because these elements have been taken away to make rocky planets. Of course, there may be questions about the actual analysis of the data and the model, but if the data holds up, this might be indicative that rocky planets can form, at least around single stars. 

One of the puzzles of planetary formation is exemplified by Tau Ceti. The planet is actually rather short of the heavy elements that make up planets, yet it has so many planets that are so much bigger than Earth. How can this be? My answer in my ebook is that there are three stages of the accretion disk: the first when the star is busily accreting and there are huge inflows of matter; the second a transition when supply of matter declines, and a third period when stellar accretion slows by about four orders of magnitude. At the end of this third period, the star creates huge solar winds that clear out the accretion disk of gas and dust. However, in this third stage, planets continue accreting. This third stage can last from less than 1 million years to up to maybe forty. So, planets starting the same way will end up in a variety of sizes depending on how long the star takes to remove accretable material. The evidence is that our sun spat out its accretion disk very early, so we have smaller than average planets.

So, would the regular stars not have planets? No. If they formed giants, there would be no real selective depletion of specific elements, and a general depletion would register as the star not having as many in the first place. The amount of elements heavier than helium is called metallicity by astronomers, and this can vary by a factor of at least 40, and probably more. There may even be some first-generation stars out there with no heavy elements. It would be possible for a star to have giant planets but show no significant depletion of refractory elements. So while Nibauer’s analysis is interesting, and even encouraging, it does not really eliminate more than a minority of the stars. If you are on a voyage of discovery, it remains something of a guess which stars are of particular interest.

The Fermi Paradox: Where are the Aliens?

This question, as much as anything, illustrates why people have trouble thinking through problems when they cannot put their own self-importance to one side. Let us look at this problem not from our point of view.

The Fermi paradox is a statement that since there are so many stars, most of which probably have planets, and a reasonable number of them have life, more than half of those are likely to have been around longer than us and so should be more technically advanced, but we have seen no clue as to their presence. Why not? That question begs the obvious counter: why should we? First, while the number of planets is huge, most of them are in other galaxies, and of those in the Milky Way, stars are very well-separated. The nearest, Alpha Centauri, is a three star system: two rather close stars (A G-type star like our sun and a K1 star) and a more distant red dwarf, and these are 4.37 light years away. The two have distances that vary between 35.6 AU to 11.2 AU, i.e. on closest approach they come a little further apart than Saturn and the sun.  That close approach means that planets corresponding to our giants could not exist in stable orbits, and astronomers are fairly confident there are no giants closer to the star. Proxima Centauri has one planet in the habitable zone, but for those familiar with my ebook “Planetary Formation and Biogenesis” will know that in my opinion, the prospect for life originating there, or around most Red Dwarfs, is extremely low. So, could there be Earth-like planets around the two larger stars? Maybe, but our technology cannot find them. As it happens, if there were aliens there, they could not detect Earth with technology at our level either.  Since most stars are immensely further away, rocky planets are difficult to discover. We have found exoplanets, but they are generally giants, planets around M stars, or planets that inadvertently have their orbital planes aligned so we can see eclipses.

This is relevant, because if we are seeking a signal from another civilization, as Seti seeks, then either the signal is deliberate or accidental. An example of accidental is the electromagnetic radiation we send into space through radio and TV signals. According to “An average large transmitter transmits about 8kW per multiplex.” That will give “acceptable signal strength” over, say, 50 km. The signal strength attenuates according to the square of the distance, so while the signals will get to Alpha Centauri, they will be extremely weak, and because of bandwidth issues, broadcasts from well separated transmitters will interfere with each other. Weak signals can be amplified, but aliens at Alpha Centauri would get extremely faint noise that might be assignable to technology. 

Suppose you want to send a deliberate signal? Now, you want to boost the power, and the easiest way to get over the inverse square attenuation is to focus the signal. Now, however, you need to know exactly where the intended recipient will be. You might do this for one of your space ships, in which case you would send a slightly broader signal on a very high power level at an agreed frequency but as a short burst. To accidentally detect this, because you have a huge range of frequencies to monitor, you have to accidentally be on that frequency at the time of the burst. There is some chance of Seti detecting such a signal if the space ship was heading to Earth, but then why listen for such a signal, as opposed to waiting for the ship.

The next possible deliberate signal would be aimed at us. To do that, they would need to know we had potential, but let us suppose they did. Suppose it takes something like 4.5 billion years to get technological life, and at that nice round number, they peppered Earth with signals. Oops! We are still in the Cretaceous. Such a move would require a huge power output so as to flood whatever we were using, a guess as to what frequencies we would find of interest, and big costs. Why would they do that, when it may take hundreds or thousands of years for a response? It makes little sense for any “person” to go to all that trouble and know they could never know whether it worked or not. We take the cheap option of listening with telescopes, but if everyone is listening, nobody is sending.

How do they choose a planet? My “Planetary Formation and Biogenesis” concludes you need a rocky planet with major felsic deposits, which is most probable around the G type star (but still much less than 50% of them). So you would need some composition data, and in principle you can get that from spectroscopy (but with much better technology than we have). What could you possibly see? Oxygen is obvious, except it gives poor signals. In the infrared spectra, you might detect ozone, and that would be definitive. You often see statements that methane should be detectable. Yes, but Titan has methane and no life. Very low levels of carbon dioxide is a strong indication, as it suggests large amounts of water to fix it, and plate tectonics to renew it. Obviously, signals from chlorophyll would be proof, but they are not exactly strong. So if they are at anything but the very closest stars they would not know whether we are here, so why waste that expense. The Government accountants would never fund such a project with such a low probability of getting a return on investment. Finally, suppose you decided a planet might have technology, why would you send a signal? As Hawking remarked, an alien species might decide this would be a good planet to eradicate all life and transform it suitable for the aliens to settle. You say that is unlikely, but with all those planets, it only needs one such race. So simple game theory suggests “Don’t do it!” If we assume they are more intelligent than us, they won’t transmit because there is no benefit for those transmitting.

The Sociodynamics of Science

The title is a bit of an exaggeration as to the importance of this post, nevertheless since I was at what was probably my last scientific conference (NZ Institute of Chemistry, at Christchurch) I could not resist looking around at behaviour as well as the science. I also gave two presentations. Speaking to an audience gives the speaker an opportunity to order the presentation so as to give the most force to the surprising parts of it, not that many took advantage of this. Overall, very few, if any (apart from yours truly) seemed to want to provide their audience with something that might be uncomfortable for their preconceived notions.

First, the general part provided great support for Thomas Kuhn’s analysis. I found most of the invited speakers and keynote speakers to illustrate an interesting aspect: why are they speaking? Very few actually wished to educate or convince anyone of anything in particular, and personally, I found the few that did to be by far the most interesting. Most of the presentations from academics could be summarised as, “I have a huge number of research students and here is what they have done.” What then followed was a very large amount of results, but there was seldom an interesting unifying principle. Chemistry tends to be susceptible to this, as a very common student research program is to try to make a variety of related compounds. This may well have been very useful, but if we do not see why this approach was taken, it tends to feel like filling up some compendium of compounds, or, as Rutherford put it rather acidly, “stamp collecting”. These types of talks are characterised by the speaker trying to get in as many compounds as they can, so they keep talking and use up the allocated question time. I suspect that one of the purposes of these presentations is to say, “Look at what we have done. This has given our graduate students a good number of scientific publications, so if you are thinking of being a grad student, why not come here?” I can readily understand that line of thinking, but its relevance for older scientists is questionable. There were a few presentations where the output would be of more general interest, though. I found the odd presentation that showed how to do something new, where it could have quite wide applications, to be of particular interest.

Now to the personal. My first presentation was a summary of my biogenesis approach. It may have had too much information across too wide a field, but the interesting point was that it generated a discussion at the end relating to my concept of how homochirality was generated. My argument is that reproduction depends on it because the geometry prevents the formation of a second strand if the first strand is not either entirely left-handed or right-handed in its pitch. So the issue then was, it was pure chance that D-ribose containing helices predominated, in part because the chance of getting a long-enough homochiral strand is very remote, and when one arises, then it takes up all the resources and predominates. The legitimate question then is, why doesn’t the other handed helix eventually arise? It may be slower to do so, but it is not necessarily impossible. My partial answer to that is the mer units are also used to bind to some other important units for life to give them solubility, and the wrong sort gets used up and does not build up concentration. Maybe that is so, but there is no evidence.

It was my second presentation that would be controversial, and it was interesting to watch the expressions. Part of the problem for me was it was the last such presentation (there were some closing speakers after me, and after morning tea) and there is something about conferences at the end – everyone is busy thinking about how to get to the airport, etc, so they tend to lose concentration. My first slide put up three propositions: the wave functions everyone uses for atomic orbitals are wrong; because of that, the calculation of the chemical bond requires the use of a hitherto unrecognised quantum effect (which is a very specific expression involving only universally recognised quantum numbers) and finally, the commonly held belief that relativistic effects on the inner electrons make a major effect on the valence electron of the heaviest elements is wrong. 

As you might expect, this was greeted initially with yawns and disinterest: this was going to be wrong. At least that seemed to be written over their faces. I then diverted to explain my guidance wave interpretation, which is essentially the de Broglie pilot wave concept, but with two additions: an application of Euler’s complex number theory that everyone seems to have missed, and secondly, I argued that if the wave really causes diffraction in the two-slit-type experiment, it has to travel at the same speed as the particle. These two points lead to serious simplifications in the calculation of properties of chemical bonds. The next step was to put up a lot of evidence for the different wave functions, with about 70 data points spanning a selection of atoms, of which about twenty supported the absence of any significant relativistic effect. (This does not say relativity is wrong, but merely that its effects on valence electrons are too small to be noticed at this level of analysis.) What this was effectively saying was that most of the current calculations only give agreement with observation when liberal use is made of assignable constants, which conveniently can be adjusted so you get the “right” answer.So, question time. One question surprised me: Does my new approach do anything new? I argued that the fact everyone is using the wrong wave functions, there is a quantum effect that nobody has recognised, and everyone is wrong with those relativistic effects could be considered new. Yes, but have you got a prediction? This was someone difficult to satisfy. Well, if you have access to a good physics lab, I suggested, here is where you can show that, assuming my theory is correct, make an adjustment to the delayed choice quantum eraser experiment (and I outlined the simple change) then you will reach the opposite conclusion. If you don’t agree with me, then you should do the experiment to prove I am wrong. The stunned expressions were worth the cost of going to the conference. Not that anyone will do the experiment. That would show interest in finding the truth, and in fairness, it is more a job for a physicist.

Space News

There were two pieces of news relating to space recently. Thirty years ago we knew there were stars. Now we know there are exoplanets and over 4,000 of them have been found. Many of these are much larger than Jupiter, but that may be because the bigger they are, the easier it is to find them. There are a number of planets very close to small stars for the same reason. Around one giant planet there are claims for an exomoon, that is a satellite of a giant planet, and since the moon is about the size of Neptune, i.e.the Moon is a small giant in its own right, it too might have its satellite: an exomoonmoon. However, one piece of news is going to the other extreme: we are to be visited by an exocomet. Comet Borisov will pass by within 2 A.U. of Earth in December. It is travelling well over the escape velocity of the sun, so if you miss it in December, you miss it. This is of some interest to me because in my ebook “Planetary Formation and Biogenesis” I outlined the major means I believe were involved in the formation of our solar system, but also listed some that did not leave clear evidence in our system. One was exo-seeding, where something come in from space. As this comet will be the second “visitor” we have recorded recently, perhaps they are more common than I suspected.

What will we see? So far it is not clear because it is still too far away but it appears to be developing a coma. 2 A.U. is still not particularly close (twice the distance from the sun), so it may be difficult to see anyway, at least without a telescope. Since it is its first visit, we have no real idea how active it will be. It may be that comets become better for viewing after they have had a couple of closer encounters because from our space probes to comets in recent times it appears that most of the gas and dust that forms the tail comes from below the surface, through the equivalent of fumaroles. This comet may not have had time to form these. On the other hand, there may be a lot of relatively active material quite loosely bound to the surface. We shall have to wait and see.

The second piece of news was the discovery of water vapour in the atmosphere of K2-18b, a super-Earth that is orbiting an M3 class red dwarf that is a little under half the size of our sun. The planet is about eight times the mass of earth, and has about 2.7 times the radius. There is much speculation about whether this could mean life. If it has, with the additional gravity, it is unlikely that, if it did develop technology, it would be that interested in space exploration. So far, we know there is probably another planet in the system, but that is a star-burner. K2-18b orbits its star in 33 days, so birthdays would come round frequently, and it would receive about five per cent more solar radiation than Earth does, although coming from a red dwarf, there will be a higher fraction of infra-red light and less visible.

The determination of the water could be made because first, the star is reasonably bright so good signals can be received, second, the planet transits across the star, and third, the planet is not shrouded with clouds. What has to happen is that as the planet transits, electromagnetic radiation from the star is absorbed by any molecule at the frequency determined by the bond stretching or bending energies. The size of the planet compared with its mass is suggestive of a large atmosphere, has probably retained some of the hydrogen and helium of the accretion disk. This conclusion does have risks because if it were primarily a water or ice world (water under sufficient pressure forms ice stable at quite high temperatures) then it would be expected to have an even greater size for the mass.

The signal was not strong, in part, from what I can make out, it was recorded in the overtone region of the water stretching frequency, which is of low intensity. Accordingly, it was not possible to look for other gases, but the hope is, when the James Webb telescope becomes available and we can look for signals in the primary thermal infrared spectrum, this planet will be a good candidate.So, what does this mean for the possibilities of life? At this stage, it is too early to tell. The mechanism for forming life as outlined in my ebook, “Planetary Formation and Biogenesis” suggests that the chances of forming life do not depend on planetary size, as long as there is sufficient size to maintain conditions suitable for life, such as an adequate atmospheric pressure, liquid water, and the right components, and it is expected that there will be an upper size, but we do not know what that will be, except again, water must be liquid at temperatures similar to ours. That would eliminate giants. However, more precise limits are more a matter of guess-work. The composition of the planet may be more important. It must be able to support fumaroles and I suspect it should have pre-separated felsic material so that it can rapidly form continents, with silica-rich water emitted, i.e.the type of water that forms silica terraces. That is because the silica acts as a template to make ribose. Ribose is important for biogenesis because something has to link the nucleobases to the phosphate chain. The nucleobases are required because they alone are the materials that form with the chemicals likely to be around, and they alone form multiple hydrogen bonds that can form selectively and add as a template for copying, which is necessary for retaining useful information. Phosphate is important because it alone has three functional sites – two to form a polymer, and one to convey solubility. Only the furanose form of the sugar seems to manage the linkage, at least under conditions likely to have been around at the time and ribose is the only sugar with significant amounts of the furanose form. I believe the absence of ribose means the absence of reproduction, which means the absence of life. But whether these necessary components are there is more difficult to answer.

Where are the Planets that Might Host Life?

In the previous posts I showed why RNA was necessary for primitive life to reproduce, but the question then is, what sort of planets will have the necessary materials? For the rocky planets, once they reached a certain size they would attract gas gravitationally, but this would be lost after the accretion disk was removed by the extreme UV put out by the new star. Therefore all atmosphere and surface water would be emitted volcanically. (Again, for the purposes of discussion, volcanic emission includes all geothermal emissions, e.g. from fumaroles.) Gas could be adsorbed on dust as it was accreted, but if it were, because heats of adsorption of the gases other than water are very similar, the amount of nitrogen would roughly equal the amount of neon. It doesn’t. (Neon is approximately at the same level as nitrogen in interstellar gas.)

The standard explanation is that since the volatiles could not have been accreted, they were delivered by something else. The candidates: comets and carbonaceous asteroids. Comets are eliminated because their water contains more deuterium than Earth’s water, and if they were the source, there would be twenty thousand times more argon. Oops. Asteroids can also be eliminated. At the beginning of this century it was shown that various isotope ratios of these bodies meant they could not be a significant source. In desperation, it was argued they could, just, if they got subducted through plate tectonics and hence were mixed in the interior. The problem here is that neither the Moon nor Mars have subduction, and there is no sign of these objects there. Also, we find that the planets have different atmospheres. Thus compared to Earth, Venus has 50% more carbon dioxide (if you count what is buried as limestone on Earth), four times more nitrogen, and essentially no water, while Mars has far less volatiles, possibly the same ratio of carbon dioxide and water but it has far too little nitrogen. How do you get the different ratios if they all came from the same source? It is reasonably obvious that no single agent can deliver such a mix, but since it is not obvious what else could have led to this result, people stick with asteroids.

There is a reasonably obvious alternative, and I have discussed the giants, and why there can be no life under-ice on Europa and reinforced by requirement to join ribose to phosphate. The only mechanism produced so far involves the purine absorbing a photon, and the ribose transmitting the effect. Only furanose sugars work, and ribose is the only sugar with significant furanose form in aqueous solution. There is not sufficient light under the ice. There are other problems for Europa. Ribose is a rather difficult sugar to make, and the only mechanism that could reasonably occur naturally is in the presence of soluble silicic acid. This requires high-temperature water, and really only occurs around fumaroles or other geothermal sites. (The terrace formations are the silica once it comes out of solution on cooling.)

So, where will we find suitable planets? Assuming the model is correct, we definitely need the dust in the accretion disk to get hot enough to form carbides, nitrides, and silicates capable of binding water. Each of those form at about 1500 degrees C, and iron melts at a bit over this temperature, but it can be lower with impurities, thus grey cast is listed as possible at 1127 degrees C. More interesting, and more complicated, are the silicates. The calcium aluminosilicates have a variety of phases that should separate from other silicate phases. They are brittle and can be easily converted to dust in collisions, but their main feature is they absorb water from the gas stream and form cements. If aggregation starts with a rich calcium aluminosilicate and there is plenty of it, it will phase separate out and by cementing other rocks and thus form a planet with plenty of water and granitic material that floats to the surface. Under this scene, Earth is optimal. The problem then is to get this system in the habitable zone, and unfortunately, while both the temperatures of the accretion disk and the habitable zone depend on the mass of the star, they appear to depend on different functions. The net result is the more common red dwarfs have their initial high-temperature zone too close to the star, and the most likely place to look for life are the G- and heavy K-type stars. The function for the accretion disk temperature depends on the rate of stellar accretion, which is unknown for mature stars but is known to vary significantly for stars of the same mass, thus LkCa 15b is three times further away than Jupiter from an equivalent mass star. Further, the star must get rid of its accretion disk very early or the planets get too big. So while the type of star can be identified, the probability of life is still low.

How about Mars? Mars would have been marginal. The current supply of nitrogen, including what would be lost to space, is so low life could not emerge, but equally there may be a lot of nitrogen in the solid state buried under the surface. We do not know if we can make silicic acid from basalt under geochemical conditions and while there are no granitic/felsic continents there, there are extrusions of plagioclase, which might do. My guess is the intermittent periods of fluid flow would have been too short anyway, but it is possible there are chemical fossils there of what the path towards life actually looked like. For me, they would be of more interest than life itself.

To summarise what I have proposed:

  • Planets have compositions dependent on where they form
  • In turn, this depends on the temperatures reached in the accretion disk
  • Chemicals required for reproduction formed at greater than 1200 degrees C in the accretion disk, and possibly greater than 1400 degrees C
  • Nucleic acids can only form, as far as we know, through light
  • Accordingly, we need planets with reduced nitrogen, geothermal processing, and probably felsic/granitic continents that end in the habitable zone.
  • The most probable place is around near-earth-sized planets around a G or heavy K type star
  • Of those stars, only a modest proportion will have planets small enough

Thus life-bearing planets around single stars are likely to be well-separated. Double stars remain unknown quantities regarding planets. This series has given only a very slight look at the issues. For more details, my ebook Planetary Formation and Biogenesis( has far more details.