Lunar Water

Currently, if people go to the Moon, they will have to take everything they need with them. Shelter might be able to use some local materials, but almost everything else will have to come from Earth. Tools and manufactured items obviously have to be taken, but so must food, air and water. But what happens in the longer run? The expenses that will be run up like that will mean that the Moon will remain a useless lump of rock unless some alternatives are found.

A recent paper (He et al. Nature geoscience https://doi.org/10.1038/s41561-023-01159-6 ) claimed that the Changé-5 rover found water of about 1mg/g in glass beads formed by impacts. They then estimated that there were enough such glass beads across the lunar surface to get 2.7 x 10^14 kg of water. An interesting point was that the water had the D/H ratio approximately equal to solar hydrogen, and the authors proposed the water was imprinted into the beads by the solar wind. Looks like the problem is solved: the surface area of the Moon is 38 million square km, so one square kilometre will give you 7,000 t of water. If there is that much water in glass beads, and we would have at least 7 million t of such glass beads per square km, why did none of the Apollo samples bring back any of these glass beads? My guess is this is something of a gross overestimate. I have no doubt there are glass beads and they truly found water in them, but sorry, the estimate of how many there are must be wrong. The rover may have accidentally found a good deposit.

So that raises the question, is there water on the Moon? First, the information here is mixed. There is a dreadful bias to find what you expect. The original samples brought back from the Apollo missions had a water content, but the people who found it assumed it came from absorption when the samples were on Earth so they disregarded the water. Interestingly, the samples had a D/H ratio that was effectively solar, so the water could not have come from Earth. So the preconceived notion that the moon was anhydrous meant that the possibility of humans staying there for any length of time was not considered to be serious. Had it been found that there was water, maybe the Apollo program would not have been terminated and maybe the space station would not have been built as more effort would focus on the Moon. The history of space travel changed by “I know best”.

“Water” formed by solar winds is well established,  but it is formed as hydroxyl groups. With silicates, the outer surface does not properly complete its bonding, so hydrogen atoms can convert lone oxygen radicals to hydroxyls. The other half of the bond would be a radical that could react with water in the solar wind. That this probably happens is found by the “water” giving a reasonable spectroscopic signal in the evening, but is much weaker during the lunar morning. There are other samples that have  been shown to contain low levels of water. Apatites returned by Apollo had water up to 200 ppm, and some unusual volcanic glasses had water up to 46 ppm. Even more surprising is a claim that one sample of lunar soil contained nitrogen in low levels, and that nitrogen was not solar as it had enhanced levels of 15N.

So, there is water on the Moon. The TV program, “For All Humanity” had a lunar research settlement beside a crater where, deeper down the sun never penetrated. There was ice. Ridiculous? Not at all because NASA crashed a vehicle into such a region and found water of very approximately 5.6% by mass. Associated with the water was (as a % of the water) H₂S 16.5%, NH₃ 6%, SO₂ 3.2%, ethylene 3.1%, CO₂ 2.2%, methanol 1.6%, methane 0.7% (Colaprete et al. 2010 Science 330: 463-468). The water would be trapped as ice in regions where the sun does not strike, as these get extremely cold, rock being a very poor conductor of heat. It has been estimated that at latitudes greater than 80 degrees, water could be trapped in parts of craters that get no sunlight. Where did those minor materials come from? The assumption is that in this case the Moon was struck by some cometary material, and the temporary atmosphere was cold-trapped.

Water is indeed critical, but in some ways nitrogen is even more critical. Going in and out of a habitat is bound to lose air, and nitrogen is critical to dilute oxygen. It is also critical if you want to grow plants. Whether we would want to stay on the Moon for long is a matter of opinion, but at least now it may be more a possibility.

Advertisement

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!

Fire in Space

Most of us have heard of the dangers of space flight such as solar storms, cosmic rays, leaks to the space crafts, and so on, but there are some ordinary problems too. TV programs like to have space ships in battles, whereupon “shields fail” (there is no such thing as a shield, except the skin of the craft, but let’s leave that pass) and we then have fire. When you stop and think about it, fire of a space ship would be a nasty problem. It burns material that presumably had some use, it overheats things like electronics, which will stop them working, then we come to the real problem: if you don’t have spares, you cannot fix it. You often see scenes where engineers have been running around “beating the clock” but what do they use for parts? If they are going to make parts, out of what? If you say, recycle, then at the very least they should be assiduously collecting “smashed stuff”.

Accordingly, it would make sense for astronauts to prevent fires from starting in the first place. You may recall Apollo 1. The three astronauts were inside the command module practising a countdown. The module used pressurised oxygen, and somehow a fire broke out. Pure oxygen and flammable material is a bad mix, and the astronauts died from carbon monoxide poisoning. The hatch opened inwards, and the rapid increase of pressure from the fire meant that it was impossible to open the hatch. The fire was presumed to have started by some loose wiring arcing, and igniting something. Now, we know better than to have pure oxygen, but the problem remains. Fire in space would not be good.

One obvious defence is to reduce the amount of combustible materials. If there is nothing to burn, there will not be a fire, but that is not entirely practical, so the next question is, how do fires burn in space? At first sight that is obvious: the organic matter gets hot and oxygen reacts with it to make a flame. However, there is more to it.

First, how does a fire burn on Earth? For a simple look, light a candle. What you see is the heat melts the wax, the wax runs up the wick and vaporises. The combustion involves breaking the wax down into a number of smaller molecules (which can be seen as smoke if combustion is incomplete) and free radial fragments, which react with oxygen. Some of the fragments combine to form carbon (soot, if it doesn’t burn further). The carbon is important because it glows, giving off the orange colour, but it also radiates a lot of heat, and that heat that radiates downwards melts the wax. What you will notice is that the flame moves upwards. That is because the gas is hot, hence it expands and occupies less volume than a similar number of moles of air. Going up is simply a consequence of Archimedes’ Principle. As it goes up, it sucks in air from below, so there is a flow of gas entering the flame from below, and exiting above. If you can get hold of some methanol, you could light that. Its formula is CH3OH, which means there are no carbon-carbon bonds, which means it cannot form soot. Therefore, it will burn with a light blue coloured flame and it does not radiate much heat. Methanol burning on your skin will not burn you as long as the skin is below the flame.

Which brings us to space. Since fire is possible on a space ship, NASA has done some experiments, partly to learn more about fire, but also to learn how to put them out on a space ship. The first difference is that in the absence of gravity, flames do not go up, after all there is no “up”. Instead, they form little spheres. Further, since there is no gravity, Archimedes’ Principle is no longer important, so there is nothing to suck fresh air in. Oxygen has to enter by diffusion, and oxygen and fuel combine in a narrow zone on the surface of the sphere. The “fire” continues with no significant flame, and further, while a normal fire burns at about 1500 – 2000 degrees K, these fires using droplets of heptane eventually form cool fire, reaching temperatures of 500 – 800 degrees K. Also, the chemistry is different. On Earth, flames usually produce water, carbon dioxide and soot. In microgravity they were producing water, carbon monoxide and formaldehyde. In short, a rather poisonous mix. Cool fires in space are no less dangerous; just different dangerous. Dealing with them may be different too. Extinguishers that squirt gas may simply move the fire, or supply extra air to it. So far, I doubt we have worked out our final methods for fighting fires in space, but I am sure the general principle is to have the fewest possible combustible materials in the space ship.

Did Mars Have an Ocean?

It is now generally recognized that Mars has had fluid flows, and a number of riverbeds, lake beds, etc have been identified, but there are also maps on the web of a proposed Northern Ocean. It has also been proposed that there has been polar wander, and this Northern Ocean was more an equatorial one when it was there about 3.6 billion years ago. The following is a partial summary from my ebook “Planetary Formation and Biogenesis”, where references to scientific papers citing the information can be found.

Various options include: (with bracketed volumes of water in cubic kilometre): a northern lake (54,000), the Utopia basin, (if interconnected, each with 1,000,000), filled to a possibly identified ‘shoreline’ (14,000,000), to a massive northern hemisphere ocean (96,000,000). Of particular interest is that the massive channels (apart from two that run into Hellas) all terminate within an elevation of 60 m of this putative shoreline.

A Northern Ocean would seem to require an average temperature greater than 273 degrees K, but the faint sun (the sun is slowly heating and three and a half billion years ago, when it is assumed water flowed, it had only about two thirds its current output) and an atmosphere restricted to CO₂/H₂O leads in most simulations to mean global temperatures of approximately 225 degrees K. There is the possibility of local variations, however, and one calculation claimed that if global temperatures were thirty degrees higher, local conditions could permit Hellas to pond if the subsurface contained sufficient water, and with sufficient water, the northern ocean would be possible and for maybe a few hundred years be ice free. A different model based on simulations, assuming a 1 bar CO₂ atmosphere with a further 0.1 bar of hydrogen, considered that a northern ocean would be stable up to about three billion years. There is quite an industry of such calculations and it is hard to make out how valid they are, but this one seems not to be appropriate. If we had one bar pressure of carbon dioxide for such a long time there would be massive carbonate deposits, such as lime, or iron carbonates, and these are not found in the required volumes. Also, the gravity of Earth is insufficient to hold that amount of hydrogen and Mars has only 40% of Earth’s gravity. This cannot be correct.

This northern ocean has been criticized on the basis that the shoreline itself is not at a constant gravitational potential, and variations of as much as 1.8 km in altitude are found. This should falsify the concept, except that because this proposed ocean is close to the Tharsis volcanic area, the deformation of forming these massive volcanoes could account for the differences. The magma that is ejected had to come from somewhere, and where it migrated from would lead to an overall lowering of the surface there, while where it migrated to would rise.

Support for a northern sea comes from the Acidalia region, where resurfacing appears to have occurred in pulses, finishing somewhere around 3.65 Gy BP.  Accumulation of bright material from subsequent impacts and flow-like mantling was consistent with a water/mud northern ocean. If water flows through rock to end in a sea, certain water-soluble elements are concentrated in the sea, and gamma ray spectra indicates that this northern ocean is consistent with enhanced levels of potassium and possibly thorium and iron. There may, however, be other reasons for this. While none of this is conclusive, a problem with such data is that we only see the top few centimeters and better evidence could be buried in dust.

Further possible support comes from the Zhurong rover that landed in Utopia Planitia (Liu, Y., and 11 others. 2022. Zhurong reveals recent aqueous activities in Utopia Planitia, Mars. Science Adv., 8: eabn8555). Duricrusts formed cliffs perched through loose soil, which requires a substantial amount of water, and also avoids the “buried in dust” problem. The authors considered these were formed through regolith undergoing cementation through rising or infiltration of briny groundwater. The salt cements precipitate from groundwater in a zone where active evaporation and accumulation can occur. Further, it is suggested thus has occurred relatively recently. On the other hand, ground water seepage might also do it, although the water has to be salty.

All of which is interesting, but the question remains: why was the water liquid? 225 degrees K is about fifty degrees below water’s freezing point. Second, because the sun has been putting out more heat, why is the water not flowing now? Or, alternatively, as generally believed, why did it flow for a brief period than stop? My answer, somewhat unsurprisingly since I am a chemist, is that it depends on chemistry. The gases had to be emitted from below the surface, such as from volcanoes or fumaroles. The gases could not have been adsorbed there as the planet accreted otherwise there would be comparable amounts of neon as to nitrogen on the rocky planets, and there is not. That implies the gases were accreted as chemical compounds; neon was not because it has no chemistry. When the accreted compounds are broken down with water, ammonia forms. Ammonia dissolves very rapidly in water, or ice, and liquefies it down to about 195 degrees K, which is well within the proposed range stated above. However, ammonia is decomposed slowly by sunlight, to form nitrogen, but it will be protected when dissolved in water. The one sample of seawater from about 3.2 billion years ago is consistent with Earth having about 10% of its nitrogen still as ammonia. However, on Mars ammonia would slowly react with carbon dioxide being formed, and end up as solids buried under the dust.

Does this help a northers sea? If this is correct, there should be substantial deposits of nitrogen rich solids below the dust. If we went there to dig, we would find out.

Space – To the Final Frontier, or Not

In a recent publication in Nature Astronomy (https://www.nature.com/articles/s41550-022-01718-8) Byers point out an obvious hazard that seems to be increasing in frequency: all those big rockets tend to eventually come down, somewhere, and the return is generally uncontrolled. Modest-sized bits of debris meet a fiery end, burning up in the atmosphere, but larger pieces hit the surface and the kinetic energy makes comparison of them to an oversized bullet or cannon-ball make the latter seem relatively harmless. In May, 2020, wreckage from the 18 tonne core of a Chinese Long March 5B rocket hit two villages in the Ivory Coast, damaging buildings. In July 2022, suspected wreckage from a SpaceX Crew-1 capsule landed on farmland in Australia, Another Long March 5B landed just south of the Philippines. In 1979, NASA’s Skylab fell back to Earth, scattering debris across Western Australia. So far, nobody has been injured, but it is something of a matter of luck.

According to Physics World the US has an Orbital Debris Mitigation Standard Practices stipulation that all launches should have a risk of casualty from uncontrolled re-entry of less than one in 10,000, but the USAF, and even NASA have flouted this rule on numerous occasions. Many countries may have no regulations. As far as I am aware my own country (New Zealand) has none yet New Zealand launches space vehicles. The first stage always falls back into the Pacific, which is a large expanse of water, but what happens after that is less clear.

In the past thirty years, more than 1500 vehicles have fallen out of orbit, and about three quarters of these have been uncontrolled. According to Byers, there was a 14% chance someone could have been killed.

So what can be done? The simplest is to provide each rocket with extra fuel. Each time it is time to end its orbit, the descent can be controlled to the extent it lands at the point in the Pacific that is farthest from land. So far, this has not been done because of the extra cost. A further technique would be to de-orbit rocket bodies immediately following satellite deployment. That still requires additional fuel. In principle, with proper design, the rocket bodies could be recovered and reused. Rather perversely, it appears the greatest risk is for countries in the Southern hemisphere. The safest places are those at greater inclination than the launch site.

Meanwhile, never mind the risk to those left behind; you want to go into space, right? Well, you may have heard of bone density loss. This effect has finally had numbers put on it (https://www.nature.com/articles/s41598-022-13461-1) Basically, after six months in space, the loss of bone density corresponded to 20 years of ongoing osteoporosis, particularly in load bearing (on Earth) bones, such as the tibia. Worse, these only partially recovered, even after one year on Earth, and the lasting effect was equivalent to ten years of aging. The effect, of course, is due to microgravity, which is why, in my SF novels, I have always insisted on ships either having a rotating ring to create a centrifugal “artificial gravity”. On the other hand, the effect can vary between people. Apparently the worst cases can hardly walk on return for some time, while other apparently continue on more or less as usual and ride bikes to work rather than drive cars. And as if bone loss was not bad enough, there is a further adverse possibility: accelerated neurodegenerations. (https://jamanetwork.com/journals/jamaneurology/article-abstract/2784623). By tracking the concentration of brains specific proteins before and after a space mission it was concluded that long-term spaceflight presents a slight but lasting threat to neurological health. However, this study concluded three weeks after landing, so it is unclear whether long-term repair is possible. Again, it is assumed that it is weightlessness that is responsible. On top of that, apparently there are long-lasting changes in the brain’s white matter volume and the shape of the pituitary gland. Apparently more than half of astronauts developed far-sightedness and mild headaches. Seemingly, this could be because in microgravity the blood no longer concentrated in your legs.

Radiation Protection on Mars

The settlement of Mars is a popular science fiction staple. I have written some “Mars novels” myself. One criticism of settling Mars is that the planet does not have magnetic field to deflect radiation, so what is the situation? In my ebook “Red Gold” I suggested a magnetic field be generated by a superconductor placed between Mars and the sun, specifically at the first Lagrange point so it would be there continuously. That would divert charged particles in the solar wind. However, suppose you do not do that, what are the options. An account has been written on May 27, 2022 and is at arXiv:2205.13786.

There are two sources of radiation. The first is from the sun and consist mainly of protons, helium nuclei (5 – 8%) and heavier nuclei (~1%). These arrive with energies ranging from some keV to hundreds of MeV. Very occasionally they go to even higher energies, and their intensity varies with the solar cycle. The other source are the cosmic rays. These are accelerated by supernova shocks and interstellar magnetic fields, and appear to come evenly from all directions. They have similar composition to the solar radiation, but they arrive with far higher energies, their average being in the GeV range, and of particular hazard are the high-charge ions, thus there may be particles up to iron that are stripped of their electrons and are travelling through space near the speed of light. It is this high energy and high charge that makes them so dangerous.

The first defence Mars offers is bulk. A person standing on the Martian surface, particularly in a crater, receives less than half what they would receive in space, and that applies to cosmic rays. None of these have energy anywhere nearly enough to go through a planet. The atmosphere, while thin, offers some protection, and will remove protons with less than 150 MeV energy, and possibly more if in a deep enough crater (which is partly why in “Red Gold” I had my settlement near the bottom of Hellas Planitia, the deepest part of Mars.) Accordingly, the major chronic hazard is cosmic radiation, but a sudden strike by a major solar event is also lethal.

There are two types of shielding. The first is active, the use of magnetic or plasma shields, but currently these are theoretical, such as my suggested L1 superconducting magnetic field generator. The second is passive, which is to place matter between the person and the source. At present we are reliant on passive measures. The better materials for stopping such charged particles are those with a high number density of atoms with many electrons per unit mass, which ends up meaning elements of low atomic number. Materials rich in hydrogen such as water or polyethylene perform well, although nothing practical can totally eliminate cosmic radiation.

For settlers on Mars, interactions with the atmosphere lead to neutrons and gamma rays being dominant. Terrain offers protection, thus being adjacent to a cliff will halve the exposure compared with open terrain. The water in regolith will greatly attenuate neutrons with less kinetic energy than 10 MeV. Liquid hydrogen is probably the best, but its extremely low temperature probably makes it impractical. Organic plastics work well; aluminium, which is used in spacecraft, is somewhat less satisfactory, but οn Μars the regolith is probably optimal, because it is already there and hence is cheap. On the other hand, it has to be bound by something, otherwise the wind will blow it away. The article suggests making bricks from regolith. The simplest protection is to live in caves. However, there may be a shortage of caves. People talk about lava tubes, but much of the volcanism on Mars has been around very large volcanoes, or older ones that erupted more in a pyroclastic fashion. They will be short on caves, while settlers are more likely to head for craters, which are not the obvious place to find caves, although rapidly exiting steam might leave one. One place where there might be caves is the Margaritifer Chaos, where there  are signs of massive water outflows from a very small source.

However, living underground does not help plant growth, and the idea of having huge caverns with lights would require a huge investment in lights. It should be easy to make glass that will be opaque to UV radiation and will offer tolerable radiation protection. Silicate uses light atoms and should compare favourably with aluminium. Further, the danger of cosmic rays is largely long-term health; plants for food are not long-lived. One of the main problems for people settling on Mars is the cost and mass of what they have to take with them. Making bricks from regolith is great because regolith is there. The cost of lifting stuff up from Earth and taking it to Mars is huge, so as much as possible has to be made there. That is why lights for the underground growing of food would be very expensive. But the making of any habitat or plant growing area on the surface requires sealing to prevent gas pressure escaping. In my “Red Gold” I suggest one of the very first things that has to be learned is how to make a cement from Martian materials. The ability to make concrete is the first requirement to make the footers of “glass-houses” to grow plants, and cement is necessary to put bricks together. There is an awful lot of detail that has to be addressed because once settlers get there, if they haven’t got something, they cannot go to the corner store and get it.

Molecular Oxygen in a Comet

There is a pressure, these days, on scientists to be productive. That is fair enough – you don’t want them slacking off in a corner, but a problem arises when this leads to the publication of papers: there are so many of them that nobody can keep up with even a small fraction of them. Worse, many of them do not seem to say much. Up to a point, this has an odd benefit: if you leave a lot unclear, all your associates can publish away and cite you, which has this effect of making you seem more important because funders like to count citations. In short, with obvious exceptions, the less you advance the science, the more important you seem at second level funding. I am going to pick, maybe unfairly, on one paper from Nature Astronomy (https://www.nature.com/articles/s41550-022-01614-1) as an illustration.

One of the most unexpected findings in the coma of comet 67P/Churyumov-Gerasimenko was “a large amount” of molecular oxygen. Something to breathe! Potential space pilots should not get excited; “a large amount” is only large with respect to what they expected, which was none. At the time, this was a surprise to astronomers because molecular oxygen is rather reactive and it is difficult to see why it would be present. Now there is a “breakthrough”: it has been concluded there is not that much oxygen in the comet at all, but this oxygen came from a separate small reservoir. The “clue” came from the molecular oxygen being associated with molecular water when emitted from a warm site. As it got cooler, any oxygen was associated with carbon dioxide or carbon monoxide. Now, you may well wonder what sort of clue that is? My question is, given there is oxygen there, what would you expect? The comet is half water, so when the surface gets warm, it sublimes. When cooler, only gases at that lower temperature get emitted. What is the puzzle?

However, the authors of the paper came to a different conclusion. They decided that there had to be a deep reservoir of oxygen within the comet, and a second reservoir close to the surface that is made of porous frozen water. According to them, oxygen in the core works its way to the surface and gets trapped in the second reservoir. Note that this is an additional proposition to the obvious one that oxygen was trapped in ice near the surface. We knew there was gas trapped in ice that was released with heat, so why postulate multiple reservoirs, other than to get a paper published?

So, where did this oxygen come from? There are two possibilities. The first is it was accreted with the gas from the disk when the comet formed. This is somewhat difficult to accept. Ordinary chemistry suggests that if oxygen molecules were present in the interstellar dust cloud it should react with hydrogen and form water. Maybe that conclusion is somehow wrong, but we can find out. We can estimate the probability by observing the numerous dust clouds from which stars accrete. As far as I am aware, nobody has ever found rich amounts of molecular oxygen in them. The usual practice when you are proposing something unusual is you find some sort of supporting evidence. Seemingly, not this time.

The second possibility is that we know how molecular oxygen could be formed at the surface. High energy photons and solar wind smash water molecules in ice to form hydrogen and hydroxyl radicals. The hydrogen escapes to space but the hydroxyl radicals unite to form hydrogen peroxide or other peroxides or superoxides, which can work their way into the ice. There are a number of other solids that catalyse the degradation of peroxides and superoxides back to oxygen, which would be trapped in the ice, but released when the ice sublimed. So, from the chemist’s point of view there is a fairly ordinary explanation why oxygen might be formed and gather near the surface. From my point of view, Occam’s Razor should apply: you use the simplest explanation unless there is good evidence. I do not see any evidence about the interior of the comet.

Does it matter? From my point of view when someone with some sort of authority/standing says something like this, there is the danger that the next paper will say “X established that . . “  and it becomes almost a gospel. This is especially so when the assertion cannot be easily challenged with evidence as you cannot get inside that comet. Which gives the perverse realization that you need strong evidence to challenge an assertion, but maybe no evidence at all to assert it in the first place. Weird?

Ebook Discount

For a short  time my ebook Spoliation is price reduced on Amazon. Unlike Kindle Countdowns, this discount applies world-wide, and I am experimenting to see how effective this strategy is.

The Board, is a ruthless, shadowy organization with limitless funds that employs space piracy and terrorism. A disgraced Captain Jonas Stryker is acting as an asteroid miner, and when The Board resorts to using a weaponised asteroid to get its way, only Stryker can divert the asteroid. The Board is determined to have Stryker killed, officially he is wanted for murder, so Stryker must expose and destroy this organization to have any future.

A story of greed, corruption and honour, combining science and visionary speculation that goes from the high frontier to outback Australia. The background also gives a scientific perspective on asteroid mining.

Warp Drives

“Warp drives” originated in the science fiction shows “Star Trek” in the 1960s, but in 1994, the Mexican Miguel Alcubierre published a paper arguing that under certain conditions exceeding light speed was not forbidden by Einstein’s General Relativity. Alcubierre reached his solution by assuming it was possible, then working backwards to see what was required while rejecting those awkward points that arose. The concept is that the ship sits in a bubble, and spacetime in front of the ship is contracted, while that behind the ship is expanded. In terms of geometry, that means the distance to your destination has got smaller, while the distance from where you started gets longer, i.e. you moved relative to the starting point and the destination. One of the oddities of being in such a bubble is you would not sense you are moving. There would be no accelerating forces because technically you are not moving; it is the space around you that is moving. Captain Kirk on the enterprise is not squashed to a film by the acceleration! Since then there have been a number of proposals. General relativity is a gold mine for academics wanting to publish papers because it is so difficult mathematically.

There is one small drawback to these proposals: you need negative energy. Now we run into definitions, and before you point out the gravitational field has negative energy it is generated by positive mass, and it contracts the distance between you and target, i.e. you fall towards it. If you like, that can be at the front of your drive. The real problem is at the other end – you need the repulsive field that sends you further from where you started, and if you think gravitationally, the opposite field, presumably generated from negative mass.

One objection often heard to negative energy is if quantum field theory were correct, the vacuum would collapse to negative energy, which would lead to the Universe collapsing on itself. My view is, not necessarily. The negative potential energy of the gravitational field causes mass to collapse onto itself, and while we do get black holes in accord with this, the Universe is actually expanding. Since quantum field theory assumes a vacuum energy density, calculations of the relativistic gravitational field arising from this are in error by ten multiplied by itself 120 times, so just maybe it is not a good guideline here. It predicts the Universe has long since collapsed, but here we are.

The only repulsive stuff we think might be there is dark energy, but we have no idea how to lay hands on it, let alone package it, or even if it exists. However, all may not be lost. I recently saw an article in Physics World that stated that a physicist, Erik Lentz, had claimed there was no need for negative energy. The concept is that energy could be capable of arranging the structure of space-time as a soliton. (A soliton is a wave packet that travels more like a bubble, it does not disperse or spread out, but otherwise behaves like a wave.) There is a minor problem. You may have heard that the biggest problem with rockets is the mass of fuel they have to carry before you get started. Well, don’t book a space flight yet. As Lentz has calculated it, a 100 m radius spacecraft would require the energy equivalent to hundreds of times the mass of Jupiter.

There will be other problems. It is one thing to have opposite energy densities on different sides of your bubble. You still have to convert those to motion and go exactly in the direction you wish. If you cannot steer as you go, or worse, you don’t even know for sure exactly where you are and the target is, is there a point? Finally, in my science fiction novels I have steered away from warp drives. The only times my characters went interstellar distances I limited myself to a little under light speed. Some say that lacks imagination, but stop and think. You set out to do something, but suppose where you are going will have aged 300 years before you get there. Come back, and your then associates have been dead for 600 years. That raises some very awkward problems that make a story different from the usual “space westerns”.

What Happens Inside Ice Giants?

Uranus and Neptune are a bit weird, although in fairness that may be because we don’t really know much about them. Our information is restricted to what we can see in telescopes (not a lot) and the Voyager fly-bys, which, of course, also devoted a lot of attention to the Moons, since a lot of effort was devoted to images. The planets are rather large featureless balls of gas and cloud and you can only do so much on a “zoom-past”. One of the odd things is the magnetic fields. On Earth, the magnetic field axis corresponds with the axis of rotation, more or less, but not so much there. Earth’s magnetic field is believed to be due to a molten iron core, but that could not occur there. That probably needs explaining. The iron in the dust that is accreted to form planets is a fine powder; the particles are in the micron size. The Earth’s core arises because the iron formed lumps, melted, and flowed to the core because it is denser. In my ebook “Planetary Formation and Biogenesis” I argue that the iron actually formed lumps in the accretion disk. While the star was accreting, the region around where Earth is reached something like 1600 degrees C, above the melting point of iron, so it formed globs. We see the residues of that in the iron-cored meteorites that sometimes fall to Earth. However, Mars does not appear to have an iron core. Within that model, the explanation is simple. While on Earth the large lumps of iron flowed towards the centre, on Mars, since the disk temperature falls off with distance from the star, at 1.5 AU the large lumps did not form. As a consequence, the fine iron particles could not move through the highly viscous silicates, and instead reacted with water and oxidised, or, if you prefer, rusted.

If the lumps that formed for Earth could not form at Mars because it was too far away from the star, the situation was worse for Uranus. As with Mars, the iron would be accreted as a fine dust and as the ice giants started to warm up from gravitational collapse, the iron, once it got to about 500 degrees Centigrade, would rapidly react with the water and oxidise to form iron oxides and hydrogen. Why did that not happen in the accretion disk? Maybe it did, and maybe at Mars it was always accreted as iron oxides, but by the time it got to where Earth is, there would be at least ten thousand times more hydrogen than iron, and hot hydrogen reduces iron oxide to iron. Anyway, Uranus and Neptune will not have an iron core, so what could generate the magnetic fields? Basically, you need moving electric charge. The planets are moving (rotating) so where does the charge come from?

The answer recently proposed is superionic ice. You will think that ice melts at 0 degrees Centigrade, and yes, it does, but only at atmospheric pressure. Increase the pressure and it melts at a lower temperature, which is how you make snowballs. But ice is weird. You may think ice is ice, but that is not exactly correct. There appear to be about twenty ices possible from water, although there are controversial aspects because high pressure work is very difficult and while you get information, it is not always clear about what it refers to. You may think that irrespective of that, ice will be liquid at the centre of these planets because it will be too hot for a solid. Maybe.

In a recent publication (Nature Physics, 17, 1233-1238 November 2021) authors studied ice in a diamond anvil cell at pressures up to 150 GPa (which is about 1.5 million times greater than our atmospheric pressure) and about 6,500 degrees K (near enough to Centigrade at this temperature). They interpret their observations as there being superionic ice there. The use of “about” is because there will be uncertainty due to the laser heating, and the relatively short times up there. (Recall diamond will also melt.)

A superionic ice is proposed wherein because of the pressure, the hydrogen nuclei can move about the lattice of oxygen atoms, and they are the cause of the electrical conduction. These conditions are what are expected deep in the interior but not at the centre of these two planets. There will presumably be zones where there is an equilibrium between the ice and liquid, and convection of the liquid coupled with the rotation will generate the movement of charge necessary to make the magnetism. At least, that is one theory. It may or may not be correct.