This and That from the Scientific World

One of the consequences of writing blogs like this is that one tends to be on the lookout for things to write about. This ends up with a collection of curiosities, some of which can be used, some of which eventually get thrown away, and a few I don’t know what to do about. They tend to be too short to write a blog post, but too interesting, at least to me, to ignore. So here is a “Miscellaneous” post.

COP 27.

They agreed that some will pay the poorer nations for damage so far, although we have yet to see the money. There was NO promise by anyone to reduce emissions, and from my point of view, even worse o promise to investigate which technologies are worth going after. Finally, while at the conference there were a number of electric buses offering free rides, at the end of the conference these buses simply disappeared. Usual service (or lack thereof) resumed.

Fighting!

You may think that humans alone fight by throwing things at each other but you would be wrong. A film has been recorded ( https://doi.org/10.1038/d41586-022-03592-w) of two gloomy octopuses throwing things at each other, including clam shells. Octopuses are generally solitary animals, but in Jervis Bay, Australia, the gloomy octopus lives at very high densities, and it appears they irritate each other. When an object was thrown at another one, the throw was far stronger than when just clearing stuff out of the way and it tended to come from specific tentacles, the throwing ones. Further, octopuses on the receiving end ducked! A particularly interesting tactic was to throw silt over the other octopus. I have no idea what the outcome of these encounters were.

Exoplanets

The star HD 23472 has a mass of about 0.67 times that of our sun, and has a surface temperature of about 4,800 degrees K. Accordingly, it is a mid-range K type star, and it has at least five planets. Some of the properties of these include the semi-major axis a (distance from the star if the orbit is circular), the eccentricity e, the mass relative to Earth (M), the density ρ  and the inclination i. The following table gives some of the figures, taken from the NASA exoplanet archive.

Planet     a              e            M        ρ           i

b           0.116      0.07       8.32      6.15      88.9

c           0.165      0.06       3.41      3.10      89.1

d           0.043      0.07       0.55      7.50      88.0

e           0.068      0.07       0.72      7.50      88.6

f           0.091      0.07       0.77       3.0        88.1

The question then is, what to make of all that? The first thing to notice is all the planets are much closer to the star than Earth is to the sun. Is that significant? Maybe not, because another awkward point is that the inclinations are all approaching 90 degrees. The inclination is the angle the orbital plane of the planet makes with the equatorial plane of the star. Now planets usually lie on the equatorial plane because that was also the plane of the accretion disk, so something has either moved the planets, or moved the star. Moving the planets is most probable, and the reason the inclinations are all very similar is because they are close together, and they will probably be in some gravitational resonance with each other. What we see are two super Earths (b and c), two small planets closest to the star, which are small, but very dense. Technically, they are denser than Mercury in our system. There are also two planets (c and f) with densities a little lower than that of Mars.

The innermost part of the habitable zone of that star is calculated to be at 0.364 AU, the Earth-equivalent (where it gets the same radiation as Earth) at 0.5 AU, and the outer boundary of the habitable zone is at 0.767 AU. All of these planets lie well inside the habitable zone. The authors who characterised these planets (Barros, S. C. C. et al. Astron. Astrophys. 665, A154 (2022).) considered the two inner planets to be Mercury equivalents, presumably based on their densities, which approximate to pure iron. My guess is the densities are over-estimated, as the scope for error is fairly large, but they certainly look like Mercury equivalents that are somewhat bigger than our Mercury

Laughing Gas on Exoplanets

One of the targets of the search for exoplanets is to try and find planets that might carry life. The question is, how can you tell? At present, all we can do is to examine the spectra of atmospheres around the planet, and this is not without its difficulties. The most obvious problem is signal intensity. What we look for is specific signals in the infrared spectrum and these will arise from the vibrations of molecules. This can be done from absorptions if the planet transits across the star’s face or better (because the stellar intensity is less a problem) from starlight that passes through the planet’s atmosphere.

The next problem is to decide on what could signify life. Something like carbon dioxide or methane will be at best ambiguous. Carbon dioxide makes up a huge atmosphere on Venus, but we do not expect life there. Methane comes from anaerobic digestion (life) or geological activity (no life). So, the proposal is to look for laughing gas, better known as nitrous oxide. Nitrous oxide is made by some life forms, and oddly enough, it is a greenhouse gas that is becoming more of a problem from the overuse of agricultural fertilizer, as it is a decomposition product of ammonium nitrate. If nothing else, we might find planets with civilizations fighting climate change!

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Trees for Carbon Capture, and Subsequent Problems

A little over fifty years ago, a 200 page book called The Limits to Growth was published, and the conclusion was that unless something was done, continued economic and population growth would deplete our resources and lead to global economic collapse around 2070. Around 1990, we predicted that greenhouse gases would turn our planet into something we would not like. So, what have we done? In an organized way, not much. One hazard with problem solving is that focusing on one aspect and fixing that often simply shifts it, and sometimes even makes it worse. Currently, we are obsessed with carbon dioxide, but all we appear to be doing is to complacently pat ourselves on the back because we shall be burning somewhat less Russian gas and oil in the future, oblivious to the fact that the substitute is likely to be coal.

One approach to mitigate global warming involves using biomass for carbon capture and storage (See Nature vol 609, p299 – 305). The authors here note that the adverse effects of climate change on crop yields may reduce the capacity of biomass to do this, as well as threaten food security. There are two approaches to overcoming the potential food shortage: increase agricultural land by using marginal land and cutting down forests, or increase nitrogen fertilizer. Now we see what “shifting the problem” means. If we use marginal land, we still have to increase the use of nitrogen fertilizer. This leads to the production of nitrous oxide gas, and these authors show the production of nitrous oxide would be roughly three times as effective as a greenhouse gas as the saving of carbon dioxide in their model. This is serious. All we have done is to generate a worse problem, to say nothing about the damage done to the environment. We have to leave some land for animals and wild plants.

There is a further issue: nitrogen fertiliser is currently made by reacting natural gas to make hydrogen, so for every tonne of fertilizer we will be making something like a tonne of CO2. Much the same happens if we make hydrogen from coal. Rather interestingly for such a paper, the authors concede they may have over-estimated the problems of food shortages on the grounds that new technology and practices may increase yields.

Suppose we make hydrogen by electrolysing water? Ammonia is currently made by heating nitrogen and hydrogen together at 200 times atmospheric pressure. This is by no means optimal, but higher pressures cost a lot more to construct, and there are increasing problems with corrosion, etc. Hydrogen made by electrolysis is also more expensive, in part because electricity is in demand for other purposes, and worse, electricity is also made at least in part by burning fossil fuels, and only a third of the energy is recovered as electricity. When considering a new use, it is important to not that the most adverse in terms of cost and effectiveness must be considered. Even if there are more friendly ways of getting electricity, you get favourable effects by doing nothing and turning off the adverse supply, so that must be assigned to your new use.

There is, however, an alternative in that electricity can directly reduce nitrogen to nitride in the presence of lithium, and if in the presence of a proton-donating substance (technically an acid, but not as you would probably recognize) you directly make ammonia, with no high pressure. So far, this is basically a laboratory curiosity because the yields and yield rates have been just too small, but there was a recent paper in Nature (vol 609, 722 – 727) which claims good increased efficiency. Since the authors write, “We anticipate that these findings will guide the development of a robust, high-performance process for sustainable ammonia production.” They do not feel they are there yet, but it is encouraging that improvements are being made.

Ammonia would be a useful means of carrying hydrogen for transport uses, but nitrogen fertilizer is important for maintaining food production. So can we reduce the nitrous oxide production? Nitrous oxide is a simple decomposition product of ammonium nitrate, which is the usual fertilizer used, but could we use something else, such as urea? Enzymes do convert urea to ammonium nitrate, but slowly, and maybe more nitrogen would end up in the plants. Would it? We don’t know but we could try finding out. The alternative might be to put lime, or even crushed basalt with the fertilizer. The slightly alkaline nature of these materials would react in part with ammonium nitrate and make metal nitrate salts, which would still be good fertilizer, and ammonia, which hopefully could also be used by plants, but now the degradation to nitrous oxide would stop. Would it? We don’t know for sure, but simple chemistry strongly suggests it would. So does it hurt to do then research and find out? Or do we sit on our backsides and eventually wail when we cannot stop the disaster.