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.

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Science in fiction II

In my previous post, I tried to show that science is a way of thinking, but that left the main issue of the title, “Science in fiction” more or less free of comment. On television, at least, there has been a glut of programs showing forensic science, with various level of realism, but the general rules of cause and effect are generally followed, and given that most of the audience would know nothing of forensic science before these programs started, and given their apparent popularity, I think this shows that if properly done, there is no reason to suspect that readers would be put off by science. The important point of such forensic science programs is that there is usually someone present, like the policeman, who knows nothing about it, and hence can be told what is going to happen. I think the concept of “No surprises!” is important. If the reader is told in advance what is going to happen, and why, the reader accepts it, provided the explanations are reasonably clear.

However, you cannot do that with a surprising discovery, and sometimes the story needs just that to drive the plot along. Thus in my novel Red Gold, which was about fraud during the colonization of Mars, I needed a very big surprise of considerable economic significance to expose the fraud. Up until the critical point, it was believed that colonization of Mars might be very difficult because the soil, or more specifically, the regolith, is rather nitrogen deficient. At the same time, the atmosphere of Mars has very little nitrogen in it. These are standard facts and are correct, as far as we have been able to find out. Rather remarkably, we have found very few nitrates, which is something of a surprise since we have found perchlorates, and it would be something of a surprise if chloride in the regolith was oxidized to perchlorate, and nitrogen did not convert to nitrates. The obvious conclusion is that there has always been very little nitrogen in the Martian soil, although there is a reason why that reasoning might be superficial.

Accordingly, one question is, did Mars accrete with almost no nitrogen, or did it have some, and that nitrogen has disappeared. This is important, because unless nitrogen is plentiful in what is called a reduced form, life is very unlikely to evolve. Suppose the nitrogen was there in the reduced form: that means there was a lot of ammonia around. If it were, as the atmosphere oxidized and carbon species turned into carbon dioxide, the ammonia would be slowly turned into urea, which would then be carried more deeply below the surface by water. Any urea or ammonia left on the surface would be oxidised to nitrogen, and would contribute to the residue in the atmosphere. The surprise could therefore be simply the discovery of urea, which would act as he fertilizer and make the settlement viable. The important point of this, at least for me, was that the story could have the settlement declared viable at a point where the fraudsters were building up a case to cash in on compensation when the settlement failed.

A feature of a genuine scientific discovery is that once you make it, in most cases it also explains a number of other problems that had been a puzzle. In this case, the problem is, where did Martian rivers come from, Mars is too cold for water to flow now, and when these rivers did flow, the sun was only about 2/3 as strong as now. There is significant evidence that Mars has never been above – 60  for any reasonable length of time. Had there been ammonia around, water can flow down to -80,  so the story can be given more credibility. This, admittedly, is something of a special case, but I think there are other options if we do not need to know too many genuine facts. Thus, if something ‘amazing’ only applies to one thing, it looks suspiciously like the proverbial ‘magic wand’, designed to do nothing more than get the author out of a plot hole.

For interested readers, on December 13, Amazon.com and Amazon.co.uk will have promotional specials of both Red Gold and Planetary Formation and Biogenesis, the latter of which gives far more details of this theory.