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.

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 (https://doi.org/10.1038/s41550-021-01487-w) 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.

Interstellar Travel Opportunities.

As you may have heard, stars move. The only reason we cannot see this is because they are so far away, and it takes so long to make a difference. Currently, the closest star to us is Proxima Centauri, which is part of the Alpha Centauri grouping. It is 4.2 light years away, and if you think that is attractive for an interstellar voyage, just wait a bit. In 28,700 years it will be a whole light year closer. That is a clear saving in travelling time, especially if you do not travel close to light speed.

However, there have been closer encounters. Sholz’s star, which is a binary; a squib of a red dwarf plus a brown dwarf, came within 0.82 light years 78,000 years ago. Our stone age ancestors would probably have been unaware of it, because it is so dim that even when that close it was still a hundred times too dim to be seen by the naked eye. There is one possible exception to that: occasionally red dwarfs periodically emit extremely bright flares, so maybe they would see a star appear from nowhere, then gradually disappear. Such an event might go down in their stories, particularly if something dramatic happened. There is one further possible downside for our ancestors: although it is unclear whether such a squib of a star was big enough, it might have exerted a gravitational effect on the Oort cloud, thus generating a flux of comets coming inwards. That might have been the dramatic event.

That star was too small to do anything to disrupt our solar system, but it is possible that much closer encounters in other solar systems could cause all sorts of chaos, including stealing a planet, or having one stolen. They could certainly disrupt a solar system, and it is possible that some of the so-called star-burning giants were formed in the expected places and were dislodged inwards by such a star. That happens when the dislodged entity has a very elliptical orbit that takes it closer to the star where tidal effects with the star circularise it. That did not happen in our solar system. Of course, it does not take a passing star to do that; if the planets get too big and too close their gravity can do it.

It is possible that a modestly close encounter with a star did have an effect on the outer Kuiper Belt, where objects like Eris seem to be obvious Kuiper Belt Objects, but they are rather far out and have very elliptical orbits. It would be expected that would arise from one or more significant gravitational interactions.

The question then is, if a star passed closely should people take advantage and colonise the new system? Alternatively, would life forms there have the same idea if they were technically advanced? Since if you had the technology to do this, presumably you would also have the technology to know what was there. It is not as if you do not get warning. For example, if you are around in 1.4 million years, Gliese 710 will pass within 10,000 AU of the sun, well within the so-called Oort Cloud. Gliese 710 is about 60% the mass of the sun, which means its gravity could really stir up the comets in the Oort cloud, and our star will do exactly the same for the corresponding cloud of comets in their system. In a really close encounter it is not within the bounds of possibility that planetary bodies could be exchanged. If they were, the exchange would almost certainly lead to a very elliptical orbit, and probably at a great distance. You may have heard of the possibility of a “Planet 9” that is at a considerable distance but with an elliptical orbit has caused highly elliptical orbits in some trans Neptunian objects. Either the planet, if it exists at all, or the elliptical nature of the orbits of bodies like Sedna, could well have arisen from a previous close stellar encounter.

As far as I know, we have not detected planets around this star. That does not mean there are not any because if we do not lie on the equatorial plane of that star we would not see much from eclipsing observations (and remember Kepler only looks at a very small section of the sky, and Gliese 710 is not in the original area examined) and at that distance, any astronomer with our technology there would not see us. Which raises the question, if there were planets there, would we want to swap systems? If you accept the mechanism of how planets form in my ebook “Planetary Formation and Biogenesis”, and if the rates of accretion, after adjusting for stellar mass for both were the same, then any rocky planet in the habitable zone is likely to be the Mars equivalent. It would be much warmer and it may well be much bigger than our Mars, but it would not have plate tectonics because its composition would not permit eclogite to form, which is necessary for pull subduction. With that knowledge, would you go?

Food on Mars

Settlers on Mars will have needs, but the most obvious ones are breathing and eating, and both of these are likely to involve plants. Anyone thinking of going to Mars should think about these, and if you look at science fiction the answers vary. Most simply assume everything is taken care of, which is fair enough for a story. Then there is the occasional story with slightly more detail. Andy Weir’s “The Martian” is simple. He grows potatoes. Living on such a diet would be a little spartan, but his hero had no option, being essentially a Robinson Crusoe without a Man Friday. The oxygen seemed to be a given. The potatoes were grown in what seemed to be a pressurised plastic tent and to get water, he catalytically decomposed hydrazine to make hydrogen and then he burnt that. A plastic tent would not work. The UV radiation would first make the tent opaque so the necessary light would not get in very well, then the plastic would degrade. As for making water, burning hydrazine as it was is sufficient, but better still, would they not put their base where there was ice?

I also have a novel (“Red Gold”) where a settlement tries to get started. Its premise is there is a main settlement with fusion reactors and hence have the energy to make anything, but the main hero is “off on his own” and has to make do with less, but can bring things from the main settlement. He builds giant “glass houses” made with layers of zinc-rich glass that shield the inside from UV radiation. Stellar plasma ejections are diverted by a superconducting magnet at the L1 position between Mars and the sun (proposed years before NASA suggested it) and the hero lives in a cave. That would work well for everything except cosmic radiation, but is that going to be that bad? Initially everyone lives on hydroponically grown microalgae, but the domes permit ordinary crops. The plants grow in treated soil, but as another option a roof is put over a minor crater and water provided (with solar heating from space) in which macroalgae grow and marine microalgae, as well as fish and other species, like prawns. The atmosphere is nitrogen, separated from the Martian atmosphere, and some carbon dioxide, and the plants make oxygen. (There would have to be some oxygen to get started, but plants on Earth grew without oxygen initially.)

Since then there have been other quite dramatic proposals from more official sources that assume a lot of automation to begin with. One of the proposals involves constructing huge greenhouses by covering a crater or valley. (Hey, I suggested that!) but the roof is flat and made of plastic, the plastic being made from polyethylene 2,5-furandicarboxylate, a polyester made from carbohydrates grown by the plants. This is used as a bonding agent to make a concrete from Martian rock. (In my novel, I explained why a cement is very necessary, but there are limited uses.) The big greenhouse model has some limitations. In this, the roof is flat, and in essentially two layers, and in between are vertical stacks of algae growing in water. The extra value here is that water filters out the effect of cosmic rays, although you need several meters of it. Now we have a problem. The idea is that underneath this there is a huge habitat, and for every cubic meter of water, we have one tonne mass, and on Mars, about 0.4 tonne of force on the lower flat deck. If this bottom deck is the opaque concrete, then something bound by plastic adhesion will slip. (Our concrete on bridges is only inorganic, and the binding is chemical, not physical, and further there is steel reinforcing.) Below this there would need to be many weight-bearing pillars. And there would need to be light generation between the decks (to get the algae to grow) and down below. Nuclear power would make this easy. Food can be grown as algae in between decks, or in the ground down below.

As I see it, construction of this would take quite an effort and a huge amount of materials. The concept is the plants could be grown to make the cement to make the habitat, but hold on, where are the initial plants going to grow, and who/what does all the chemical processing? The plan is to have that in place from robots before anyone gets there but I think that is greatly overambitious. In “Red Gold” I had the glass made from regolith processed with the fusion energy. The advantage of glass over this new suggestion is weight; even on Mars with its lower gravity millions of tonnes remains a serious weight. The first people there will have to live somewhat more simply.

Another plan that I have seen involves finding a frozen lake in a crater, and excavating an “under-ice” habitat. No shortage of water, or screening from cosmic rays, but a problem as I see it is said ice will melt from the heat, erode the bottom of the sheet, and eventually it will collapse. Undesirable, that is.

All of these “official” options use artificial lighting. Assuming a nuclear reactor, that is not a problem in itself, although it would be for the settlement under the ice because heat control would be a problem. However, there is more to getting light than generating energy. What gives off the light, and what happens when its lifetime expires? Do you have to have a huge number of spares? Can they be made on Mars?

There is also the problem with heat. In my novel I solved this with mirrors in space focussing more sunlight on selected spots, and of course this provides light to help plants grow, but if you are going to heat from fission power a whole lot more electrical equipment is needed. Many more things to go wrong, and when it could take two years to get a replacement delivered, complicated is what you do not want. It is not going to be that easy.