John Campbell’s Solar System

Seventy-one years ago John Campbell, future pivotal, legendary editor of “Astounding/Analog” SF magazine (1938-1971), was just another writer – actually two because he used “Don A. Stuart” as a pseudonym. He was fresh out of University with a physics degree and embarked on a series of monthly fact articles about the Solar System that lasted 18 months. Even 71 years later the series is surprisingly insightful and not woefully dated, unlike the fiction from the same era.

John Campbell’s Solar System

One particularly striking bit of ‘alternative history’ is this little passage…

IN 1666 the hated fourth law of light attracted Newton’s attention, and he tried an experiment to prove that white light is a blend of colored light. He admitted sunlight through a round hole to a prism, getting then the familiar colors, ranging smoothly, gradually, featurelessly, from violet through blue, green, yellow, orange to red. By means of a second prism he showed that they could be recombined to a beam of white light. Newton proved white light was compounded of colored. It was a great discovery.

For the fourth law of light is the law of the spectroscope. By it, to-day, the secret language of light may be read; by it, light talks like a garrulous old maid at a gossip’s tea party. It tells all the secrets of the universe. By it we can analyze the Sun and the million-billion-mile-distant star; we sample the air of Jupiter and Mars; and we time the speed of the moving stars. By it we analyze the minerals of Earth or star.

In 1666 America was a howling wilderness, where Puritan Pilgrims held on by tooth and toenail to a narrow strip of seacoast. England had just overthrown Cromwell. Men sought unicorns for their magic, cure-all horns. Oxygen was not to be dreamed of for a century and more. Chemistry, the basis of modern civilization, was alchemy, and men sought the philosophers’ stone.

In 1666 Newton, the man who developed the law of gravity from idle speculation on a falling apple, used a round opening to produce his spectrum, and got round images of the Sun in every color, smoothly overlapping and featureless. A spectroscope uses exactly the same apparatus save that they have a thin, hairline slit, so that each color is thrown in a hairline, sharply distinguishable mark of light.

Literally, by a hairline Newton missed the spectroscope. Had he used a slit, the spectrum of the Sun would have been bright colors crossed by mysterious black bands and lines. He could not have left that mystery untouched. He would have found that sodium thrown on a candlewick would produce bright-yellow lines matching exactly two powerful dark lines in the mysterious solar spectrum. Calcium would have given him red lines, copper and other metals —

Chemistry would have started up like a stung rabbit from spectroscopy, not test tubes! Oxygen in a year, not a century and a half. The elements of the rocks in months.

But spectroscopy waited untouched from 1666 to 1802. Can you conceive what an alien world this might have been had a man who mastered gravity, calculus and the laws of motion used that slit, the one great thing that challenges gravity for supremacy in teaching mankind?

…a particularly appropos alt.history as Newton investigated alchemy thoroughly to try to discern the fundamental laws underpining its concrete findings. In the end he failed and chemistry needed almost 150 years for Dalton’s atomic theory to revolutionise its methodology and organise its finding’s with an over-arching conceptual structure. But what if Newton had discovered the absorption lines in the spectrum first? Incredible scientific advances would have occurred 170 years early and the world would’ve had scientific chemistry before the Industrial Revolution, perhaps bypassing many of the dead ends.

Postscript

One downside that occurred to me, if chemistry arrived early via spectroscopy, was the fate of SF. Much of the early excitement of science fiction was the prospect of nearby alien life on the planets. If Campbell could pronounce the Solar System mostly dead in the 1930s after the first spectroscopic examinations of the planets, then early spectroscopy might have strangled the babe in its crib. Knowing the planets to be utterly unlike Earth by 1800, say, would have led to the still-birth of spaceflight. Missiles might have been developed, and flight, but with nothing to visit nearby, the major impetus behind the western inventors of the Space Race – the thought of Martians and Venusians amongst American, British & German space enthusiasts in the 1920s-40s – might have killed their efforts. No Goddard, von Braun, Ley, Oberth, and Clarke, to name a few.

But that may not have been the ‘kiss of death’ I’ve imagined for Russian space enthusiasts – Tsiolkovsky was of the opinion that ETIs were rare in the Universe, but that did nothing to dampen the passions of Russian wannabe cosmonauts. Perhaps the Soviets would have developed liquid fuel rockets before the Nazis? That alt.history would have been very different indeed with Stalin’s Russia bombarding the upstart fascists with Tsiolkovskyan liquid-fuelled missiles…

How much information is needed for Life?

I’m sick to death of people claiming ridiculous amounts of information in genomes. Pundits with an axe to grind against materialism like to liken the information in a simple cell to the Encyclopaedia Britannica – all of it. But we’ve actually measured the information in microscopic replicating biosystems – viruses, archaea and bacteria – so we have some guide to what’s needed. Biosystems are made of both simple and incredibly complex molecules – and the complex ones, proteins, are encoded as a sequence of DNA. In microbes the DNA is one huge loop – a ring – which tiny molecular machines called ribosomes read and convert the information into proteins. The information itself is the order of amino acids – twenty specific ones in most lifeforms – which make up the protein itself. Once the amino acids are put together into a string connected by chemical bonds the newly made protein then folds up into a shape that lets it do the specific chemistry task that it controls. For many proteins a large fraction of the amino acid sequence can be changed with no change in function or form – most of the action happens in a few small regions. Some protein machines are ubiquitous in function throughout the biological world – cytochrome c for example – but exist in a HUGE variety, with completely different sequences of amino acids.

So how much information will let a biosystem self-replicate? Viruses don’t, though some contain more DNA than the simplest bacteria. But Viruses do self-assemble after their proteins have been made by a host-cell’s ribosomes. In fact many intricate protein machines – which viruses are just one example of – self-assemble from their component proteins, without any apparent molecular “master-builder”. Instead as the proteins jostle around inside their host cell, their specific magnetic linkages will find each other and link up. Brief interactions between the proteins and other unrelated proteins might occur, but in the constant jostling only a proper fit will stick the two together fastly. It’s crowded and busy inside even the simplest cells.

The simplest self-replicating biosystem known is an intra-cellular parasite called Nanoarchaeum equitans a bacterial parasite with a DNA string about 490,885 base-pairs long. A base-pair is the minimal unit of DNA information, which can have four different values (equivalent to 2 bits of computer-style information.) There’s 3 bases per codon in DNA’s “language” so the Nanoarchaeum genome is about 163,000 codons long. A codon is roughly 6 bits. Thus the simplest self-replicator is the equivalent of about 122 kilobytes (1 byte = 8 bits.) There’s 10,000 symbols (including spaces) per page of the Encyclopaedia Britannica – I counted it out of curiosity one day. Each symbol of print is roughly a byte. Thus Nanoarchaeum needs just 12 pages of Britannica to encode its genes.

Taking into account the redundancy of the DNA codon code and the roughly 50%-80% redundancy of amino acid sequences themselves, that means roughly 34 – 13.5 kilobytes of information will code a self-replicating DNA-based cell. Just 3 to 1 page of Britannica.

That’s still a lot of information to “just happen”, but in our ignorance of proto-biochemistry we might be missing the key element that simplifies matters even further.

Weirder things might be needed. Physicist Paul Davies has speculated that backwards causation might cause the past to be at least partially determined by the future – thus biochemistry was arranged to be consistent with the existence of Life by the (future) observation that Life exists. Else there would be no observation for that “consistent history” to ever happen. This occurred not by design, as in engineering by an external god, but by an inner mathematical consistency that insists the Universe is observed and thus observers should exist.

The self-referential nature of that idea gives me a headache, but check out Davies “The Goldilocks Enigma” (called “Cosmic Jackpot” in the USA) for a fuller discussion. There’s a whole barrel of mysteries as to how proteins do what they do and we might find some pretty wild quantum effects are necessary for life itself.

Ask yourself: if you were a god how would you do it? Can Life be designed?

Milky Way Census

I am rather puzzled by just how many stars there are in the Milky Way too. Different sources give different figures, but ask an astronomer and they usually say 100 billion, roughly. That figure comes from actually measuring the light put out by the Milky Way and doing the sums.

If you look at the mass of the Milky Way – for example by taking the orbital radius and velocity of the stars at the galactic periphery, then working backwards – you get hundreds of billions of solar masses. However a BIG fraction is dark-matter and dark gas etc. and we really don’t know how much there is of either. If you look at the Milky Way from M31 and measure its mass via its satellite galaxy orbits you get about 1.2 trillion solar masses.

The total luminosity gives a less theory laden measure. That works out at about 55 billion solar luminosities and a baryon mass of about 60 billion solar masses. For a recent study check out this link. Divide that mass-figure by the average stellar mass and multiply by the fraction that is stars, and you only get about 100 billion stars. About 20 billion of those are roughly Sun-like. Assuming a Galactic disk age of 10 Gyr, a random spread of ages, and an oxygenic biosphere life-time of 1 billion years, thus there’s about 2 billion stars that could have planets with oxygen.

I’ll put my head out and say that 50% have terrestrial planets (Geoff Marcy’s estimate) and 50% of those systems have a planet in the habitable zone (Kasting’s estimate.) Thus there’s 500 million planets as old as Earth and in the right place for life-as-we-know-it. Not a lot different from Stephen Dole’s estimate from 1964 of 640 million. What’s different is that we now KNOW there are planets out there. Dole only know of a few possible planets – none of which are correct, though 61 Cygni is still a maybe.

But how many actually have life? A new study by researchers from my Alma Mater has demonstrated actual microbial remains from 3.5 billion years ago which is a boost to prospects for figuring out just when Life got started here. But does it tell us about Out There? Many popularists for SETI – the Search for ExtraTerrestrial Intelligence – argue that because Life arose very soon after Earth became stable (any time after 3.9 billion years ago) then it must be ‘inevitable’ and arise wherever it can. However the mystery of Life’s origin is still a matter of debate and very few facts. We do know that DNA-RNA style life is incredibly complex compared to basic organic chemistry, but we also know that cells make themselves using relatively small amounts of information. Their constituent molecules assembly themselves into an ordered whole very easily. How?

Until we know that the numbers of planets with Life might just be one.

Engineer the Sun!

Trying to imagine Life billions of years from now seems kind of futile to me. But if there’s any trace of us left then I can imagine they’d be familiar and yet very strange too. Certainly no end of SF writers have tried – Stephen Baxter, Poul Anderson and Charles Sheffield have had the balls to take readers to the end of Time, and beyond. Let’s be a bit more prosaic and stick to our little Solar System. So what would billions of years of technological advancement let us do?

We all know the Sun will evolve into a bloated, overluminous giant about 5 billion years from now – a timeframe that depends on the amount of heavy elements in the Core. According to a fairly standard model, the Sun’s future is as follows (in gigayears of the Sun’s age. Subtract 4.6 Gyr to get the date from now)…

(A) Core burning ends, t = 9.4 Gyr
(B) Redwards Traverse, end of Main Sequence, t = 10.9 Gyr (Sun pretty stable, Mars’ temperature rather nice)
(C) First RedGiant ascent, t = 11.6 Gyr (Sun goes from about 3 times present luminosity to about 2,400)
(D) Sun’s Core explodes, Helium burning begins, t = 12.1 Gyr (Sun pretty stable, Jupiter’s rather nice)
(E) Asymptotic Giant Branch, t = 12.2 Gyr (Sun goes from about 45 to 6,000 times present)
(F) Planetary Nebulae shed off, Sun dies as White Dwarf, t = 12.25 Gyr

Of course Earth, left to Nature’s course, dies long before the Sun even finishes Core burning. In about a billion years photosynthesis will crash and/or the oceans will be ploughed into the mantle by plate tectonics. Bacteria might survive for another billion, but eventually it’s all desert and a slow warming towards a Venus-like greenhouse. For Earth’s biosphere – and our “descendents” – the usual options are:

(1) extinction
(2) Move the Earth
(3) Live in mobile space colonies
(4) Put up sunshades
(5) Move to another planet

Instead of migrating, moving the Earth, or moving into space permanently – and they’re all options that might be taken – I would suggest a more radical option: engineer the Sun.

A few facts suggest this might be worthwhile.

First, the Sun will go red giant after using a tiny fraction of its total energy potential. This seems rather wasteful to me.

Second, magnetic fields can potentially reach all the way down into the Sun’s core. Thus we might be able to control the Sun’s energy output and its chemical evolution by inducing convection.

So just how much energy is available? If all the Sun’s mass converted to energy at current output it would last 14.5 trillion years. But it’s a giant fusion reactor instead. Proton-proton fusion, and associated reactions, convert 0.7% of the mass into energy. As the Sun is currently 74% hydrogen, proton-proton fusion would last 75 billion years using all the hydrogen. If we ignited helium fusion after that we might get another 30 billion years.

That sounds pretty good, but could we go further?

Some of the energy involved in the Sun’s evolution is from gravitational collapse. About half the Sun’s mass will collapse into a white dwarf liberating a few billion years worth. If the Sun could be collapsed further then even more would be liberated. The absolute limit is, of course, when the Schwarzschild radius is reached and we’ve made a black hole. If we collapsed the Sun into a quark-star just 6 km in radius we might extra a few trillion years of energy out of it.

Via reverse baryogenesis we might then extract all the mass-energy out of the remaining quark mass, thus getting the full 14.5 trillion years. All up we might extract 20 trillion years out of the Sun. But what happens then?

Instead of burning the Sun’s mass up perhaps we could change power sources. There’s a lot of dark matter around and the evidence is good that it self-annihilates with a release of real energy. Perhaps the Sun could be converted into a dark matter reactor? This is believed to happen naturally in white dwarf stars – but the power level is low. We might clever enough to develop a means of funnelling dark matter in to improve the output.

After all the options of this universe are tried perhaps we’ll have to look into higher dimensions to extend the Sun’s life even longer. We have a long, long time to figure out what to do.

Clovis and after…

North America was devastated by a cometary explosion as recently as 12,900 years ago, according to a bunch of geoscientists at a recent meeting. Now a palaeoanthropologist has chipped in…

Comet theory collides with Clovis research

…pointing to the apparent decline in a Clovis-style culture, known as the Redstone culture, just after the putative comet explosion. Clovis and Redstone are known, as cultural groups, by distinctive spear-points and the later Redstone points are much, much rarer than the Clovis points – about 5-to-1 in numbers. Very odd, unless the originating people group has declined.

Plasma life

New research on plasma crystals raises the prospect of inorganic helices encoding genetic information…

‘It might be life Jim…’, physicists discover inorganic dust with life-like qualities

…for a long time I have pondered the possibility that UFOs – unexplained ones, not the mundane sort – are caused by coherent plasma structures that we can call “alive” though not ‘organic’. Work on plasma crystals seemed a way for plasma beings to have some sort of stability though made out of a medium in continual flux like plasma, and now this new work has confirmed my suspicions.

If plasma beings – which I call “plasmons” even though that means something else in optical physics – exist how would they manifest to us? Balls of glowing light are one possibility – their raw physical natures concentrated and leaking visible energy. They might also, after co-existing with us for millennia, know how to manipulate our perceptions magnetically, via fine-scale magnetic-field variations around our skulls to excite our neurones. Plasmons might then appear in whatever form the brain dredges up to explain the imperfect firings of neurones – could religious, paranormal & UFO visions result from plasmons trying to communicate with us? Being plasma they could have existed almost from the dawn of time, spanning the cosmos, perhaps even playing a role in the creation of life on “cold matter” worlds like our own.

Think on it.

Palaeoanthropology chaos

Old bones speak volumes, but how we understand them depends on our prejudices. The latest news about Homo erectus and Homo habilis is that they aren’t a simple ancestor-descendent set of species. Instead they co-existed…

Fossils Could Force a Rethink

Twin fossil find adds twist to human evolution

…though that’s an arguable point. Tim White, of Berkeley, points out that the putative habiline jaw is distorted and hard to get precise measurements off – an important thing as erectus and habilis are very similar in that particular feature. Even if the jaw is just an Erect, the new skull is really interesting – all the robust features of the Erects, but very small.

Small enough, perhaps, to produce a Hobbit after a bit of island dwarfism?

Another interesting bit of news is the idea that bipedalism was a feature of our last common ancestor (LCA) with the Asian and African apes. Both orangutans and gibbons walk around on tree-branches using two legs and a new study has supported the idea that our LCA with the orangs was a biped…

Red Ape Walking

…a curious bit of the article is some palaeoanthropologists pointing out the knuckle-walking peculiarities of Australopithecus afarensis which, they say means we humans evolved from knuckle-walkers. Perhaps not, I say, as very recent molecular work suggests a split between humans and chimps at c. 4.1 mya, not long before the appearance of afarensis with its chimp-like features. Perhaps A. afarensis is a chimp ancestor? After all chimps and gorillas have had as long to evolve their peculiarities as we have had to evolve ours. Much of what we see in them today is, potentially, as derived from our LCA as what we see in ourselves.

How Big is a Planet?

Stars are fundamentally different to planets and one surprising way in which they differ is just how big they can get. Heavy stars get hotter and they puff-up from very fast fusion rates – stars heavier than the Sun fuse hydrogen chiefly via the much faster carbon-nitrogen-oxygen cycle, which is a minor cycle in the present Sun. What faster fusion rates means is that the big, fat stars are BIG – some are much larger than the Sun. Some are so large and violently bright that they’re losing mass into space, forming gigantic nebula. One spectacular example is Eta Carina and its rather pretty nebula.

But what about planets? “Cold” matter – anything less than a 10,000 K – supports itself against the remorseless pressure of gravity by electrostatic forces, rather than the fusion heat of a star’s interior (which is over 3,000,000 K at a minimum.) As the pressure increases – and thus the planet’s mass – the electrons and nucleii of the planet’s core part company, becoming pressure ionised. Past this point the planet is supported by the mutual Pauli exclusion of electrons, which has some strange properties, one of which is increasing mass causes the planet’s size to shrink. When this happens the core is said to be composed of degenerate matter. Shrinking a planet releases energy and this causes the interior to become increasingly hot, puffing the planet up slightly. As a result planets heavier than Jupiter are roughly all the same size – roughly Jupiter size (about 10% of the Sun’s diameter.)

But that’s planets composed of so-called “cosmic abundancies” of matter – about 3/4 hydrogen, 1/4 helium and a bit of everything else. Planets can lose all their gaseous hydrogen/helium as they form and thus be composed of things like water, carbon, sulphur, “silicates” (chiefly metal oxides) and iron. Other elements are too rare to make bulk components of a planet, though they can be selectively concentrated in the outer crust (like uranium/thorium and potassium seem to be on Earth.) A new paper has come out discussing just how big a planet made of such things can get, with some interesting results…

Mass-Radius Relationships for Solid Exoplanets

…one of the co-authors is Marc Kuchner, who has previously enticed us with descriptions of carbon-rich planets, and planets made of ice. A few years ago one of the first exoplanets in a circular habitable zone orbit was discovered…

HD 28185

…and it masses about 5.7 Jupiter masses. Most exoplanet watchers assumed it might have habitable moons – if moon mass scales linearly with planet mass it should have about 4-5 moons as big as Mars – but one brave soul thought the planet itself might be a “super-Earth” made of Earth-like stuff. At that mass, if silicate/iron mixes didn’t get denser with pressure, the planet would be as big as Jupiter (about 12 Earth diameters) with about 12 gees gravity. But, as the new paper describes in detail, such materials get a LOT denser with pressure, and the MAXIMUM size a super-Earth can get to is 3 Earth radii. Thus HD 28185b would have a surface gravity of 200 gees – a most unsuitable home for life-as-we-know-it.

Hypothetically, though, what would such a planet be like? Firstly it would have 1800 times the radioactive material heating up only 9 times the surface area – thus a radioactive heat flow of 16 watts (cf. Earth’s mere 0.08 W.) Such a heat-flow would mean the planet would remain at 130 K even without a star – though that’s an average temperature, and in reality much of the surface would be lava. With so much tectonic activity and so much mantle heat flow gases and volatiles wouldn’t remain trapped in its mantle for long – it would probably be wrapped in a thick layer of superheated steam and carbon dioxide, the surface aglow at over 900 K before its heat could escape into space. Even in interstellar space the planet would glow a dull red and remain at hellish temperatures for billions of years.

Bible errancy

As I noted below, the Bible contains history and has a history. During the course of its development certain quite notorious “exaggerations” of specific numbers crept in – famously the +900 year ages of pre-Flood patriarchs, like Methuselah’s 969 years, and the shorter, but still implausible, ages of post-Flood patriarchs. Abraham is said to have lived to 175, Isaac to 180 and Jacob only managed 147. There’s no evidence anyone ever lived so long in all human history, so such figures have to be either deliberately inflated by Biblical scribes or misread from old ancestor-lists. Either option is unacceptable to a believer in “Biblical Inerrancy”, but fits with the principle that God accommodates his message to its listeners and uses their pious scribblings to deliver His Word to those ready to hear.

Less obvious number games give us some exaggerated census figures in the book of “Numbers” – on two separate occasions Moses counts the Israelite men, 20 and over, as 603,550 and 601,730 – implying a much larger populace. By itself such figures aren’t totally absurd, but a moving population of over 2 million would have stood out like a sore thumb in the archaeological record of the Sinai. Tent traces, bones from their flocks, latrines, fireplaces and small personal items tend to last in such dry, dusty conditions, and they exist through archaeological time, but only for an estimated 20,000 or so people at any one time.

Also the Bible itself calls the numbers into question.

Firstly, it claims Israel was to displace 7 much larger nations – and that would’ve crammed the Levant with living traces that just don’t exist. A population of over 14 million just can’t live in that region with Bronze Age technology, and even today the few million in Israel/Palestine is stretching the limit.

Secondly, it gives us a proxy for the number of adult women by its recording of a count of Firstborn males, 1 month old or more, amongst the Israelites – surprisingly low at 22,273. Unless the average number of male children per woman was about 54 plus then clearly someone has messed up the sums.

So what happened? And why did no one notice?

The second is easiest to answer – misplaced piety. A bit of thought caused any rational person to say “there’s something wrong!” but no one wanted to commit “blasphemy”, Jewish or Christian, by questioning what “Moses” wrote. Eventually the Enlightenment brought rationalism to Biblical criticism, but of a rather negative variety that consigned all such Bible stories to the “pious fiction” bin. I want to avoid that trap, myself, so I’d rather believe some scribes got the figures wrong, and misplaced piety meant later scribes let the error stand.

The first question is much harder to reconstruct an answer to because we have no clear idea of what the original figures were. If we accept the 22,273 figure we also have to accept the number of Levites was 22,000 – which might be a bit high. Later in the book the number of male Levites between 30 and 50 is recorded as 8,580, which doesn’t quite fit the 22,000 total either. But if we accept that as an average, then 13 tribes of Israel (12 + Levi) has roughly 286,000 males, and the total populace is roughly double that. Still a bit high in terms of Firstborn… the average woman has had about 26 kids. Since earlier in the Book of Exodus only two mid-wives are mentioned this is a tad high.

Let’s call this one a work in progress. In an associated page I’m going to put down all the genealogical data in the relevant books and that can be the data to work off. Bright ideas welcome!

Chilling Venus

An old SF dream, independently invented by Olaf Stapledon and Jack Williamson, is the idea of terraforming. Venus has long been viewed as a suitable target. When CO2 was first found in huge amounts in the 1920s, Stapledon imagined giant electrolysis stations converting the atmosphere. In the 1940s the “dry formaldehyde” Venus was a popular model and became the setting of Poul Anderson’s “The Big Rain” – the planet-obscuring clouds were believed to be formaldehyde polymer dust and the surface was a dry 100 degrees C. Clever chemistry would convert the clouds into water and eventually the Big Rain would fall.

By 1960 the clouds were believed to be water and the surface was roughly 270 degrees C with about 2 bars pressure – thus Carl Sagan’s famous suggestion: seed the clouds with algae to convert the CO2 into oxygen. But by 1963 Sagan had abandoned the water cloud model and the temperature was estimated to be a scorching 700 K with about 100 bars of nitrogen causing a super-greenhouse effect and “cloudiness” was due to scattering. Larry Niven famously described the surface conditions as “a searing black calm” and proposed Earth only avoided such a fate by the early Moon stripping excess air away.

By 1968 Russian Veneras had shown the surface to be even hotter and the atmosphere to be almost all CO2. The clouds had become a total mystery because the measured water vapour levels were so low. Venus’ surface was depicted as a stormy darkness with red-hot patches of glowing rock. Carl Sagan’s idea of seeding the clouds had become SF mythology and remained unchallenged.

After the probes of 1974/5 – Venera camera landers and Mariner X – the clouds were known to be sulphuric acid and the surface was surprisingly bright. More like an overcast day on Earth than an abyss of Hell, though even hotter at 735 K. By 1976 serious studies for terraforming Mars had also led to a re-examination of Venus and the realisation that it was too dry for algae. To make O2 from CO2 requires H2O – and 90 bars of CO2 needs an ocean of water to turn into algae and oxygen. But all that oxygen was far too much oxygen. James Oberg’s “New Earths” proposed combining the oxygen with hydrogen tanked in from the Outer Planets – Saturn being a favourite. A bit “cart before the horse” because there would be no oxygen made without water…

A number of approaches were proposed through the 1980s, but the scenarios all required millennia. David Brin mentions a 10,000 year terraforming project being undertaken by the Earth Clan, to impress the Galactics that we “wolflings” weren’t too hot-headed and impatient to join Galactic society. Nice fiction, but unlikely for a standard human society to undertake. Paul Birch proposed in 1991 a different approach – why not cool Venus enough to freeze out the atmosphere and then bury it for later export off-world?

That’s the new “orthodoxy” of terraforming – chilling Venus’ atmosphere with a gigantic soletta parked in the Sun-Venus L1 point. A major question, then, is just how long would it take to cool, condense and freeze? Currently Venus’ “photosphere” – the region heat escapes from – is at a temperature of about 231 K, but this is due to the high cloud deck giving the planet a high albedo in visible and IR light. Chilled just a bit and the cloud deck would probably collapse since its main component is sulphuric acid, which boils at over 338 degrees C at 1 atm. With a higher emissivity Venus would lose heat somewhat faster, but just how much heat is there?

Carbon Dioxide (96.5% of the atmosphere), unlike nitrogen (3.5%), has quite a variable specific heat capacity – it stores more heat, the hotter it gets in the temperature range in Venus’ atmosphere. Nitrogen remains pretty stable, being a diatomic molecule, but carbon dioxide is triatomic and thus its ways of storing energy are quite complex. I’ve created a model of this process in an Excel spread-sheet and it has some interesting results, which I’ll elaborate on in a future post. But for now basically the hotter Venus’ photosphere is the quicker it’ll lose heat.

Once the temperature of the lowest layers reaches about 31 C the carbon dioxide will start condensing at the 74 bar pressure level, with interesting results – the phase-change heat liberated will drive convection, perhaps keeping the upper layers at a roughly constant 31 C until all the condensible CO2 below the 74 bar pressure level has rained out. Then it will only continue condensing, as the lower levels cool, down to a partial pressure of about 5 bar. Liquid CO2 can’t exist below that pressure – it’s either ice or gas past that point, and as it cools it will increasingly freeze-out, perhaps coating the underlying seas of cold CO2 in a pressure cap – except, unlike water ice, it’s heavier than its liquid phase. A bit of water might be needed to ice over the cold CO2 seas, which will be percolating into Venus’ regolith, and probably making geysers all over as it cools the underlying rocks. A big fraction might then be trapped in the regolith, but Venus’ sub-surface will probably be too hot for it to remain there indefinitely.

Once the CO2 is frozen out and capped over what remains? The nitrogen won’t freeze or liquefy under such conditions and so will make an atmosphere of about 3 bars, which would be a bit much for a prolonged human presence. The regolith might soak up a bit and some will probably “dissolve” in the CO2. Big thinkers have proposed haulling it off-world for Mars and free-space habitats, providing a long term export product. All the CO2 would be even more valuable as carbon nanotubes might eventually be the macro-engineering material of choice, with a theoretical 2 teraPascal strength. Stephen Baxter has Venus supplying carbon across the Galaxy for the War against the Xeelee in his novel “Exultant.” I would hope for something more peaceful.

My daughter’s first-typing… apryll jane georgia crowl, 5