Resources of the Solar System 2: Venus

Venus orbits the Sun at ~ 0.72 AU and receives roughly twice the insolation as Earth – with very low variation because its orbit is nearly circular. Its mass, radius and surface gravity are very close to our own – 0.815 Earth masses, 6052 km and 8.87 m/s^2 respectively. Its orbit around Sol lasts 243.1 Earth-days and its rotation on its axis is 224.7 Earth-days, but retrograde. This means the solar-day – time between sunrise and sunrise – is 116.8 Earth-days. Thus, without centrifugal force countering gravity, the Venusian globe is very nearly spherical, unlike all the other large planets, Earth and Mars included.

The most striking feature of Venus is its atmosphere – opaque, very reflective and very massive. By volume it’s 96.5% carbon dioxide and 3.5% nitrogen, and little dashes of everything else. The clouds are a practically unbroken haze of fuming sulfuric acid (H2SO4 + SO3 in solution with a bit of water) and opaque because they’re very deep, many kilometres. Surprisingly, if condensed, they would amount to only a few centimetres of acid. Beneath the haze banks the air is clear, though there are unidentified particles floating around that might be decomposed acid (i.e. grains of sulfur.) From the visible top-deck of the clouds to the surface is about 70 km and the surface pressure is a very high 92 bar. The surface temperature is ~ 735 K or 462 C/864 F, and would glow a dull red if the sunlight didn’t sufficiently penetrate the clouds to give a hellish eternal glow.

So what’s available on such a nasty planet? Let’s do an inventory

(1) Atmosphere – carbon dioxide is about a quarter carbon, which is the high-strength material of the future. Nitrogen is more abundant than on Earth – 2.7 times as much in fact. Combined the atmosphere could supply C,N,O for millions of space-cities, but that’s an as yet non-existent market.

(2) Surface – while hot there are materials that happily tolerate such conditions and retain strength, so teleoperated machines would work just fine, especially using high temperature electronics developed by the US DoD. Venus is similar in bulk density to Earth so its mineral resources will be akin, but differently distributed. Water has played a major role in concentrating ores on Earth, powered by plate tectonic processes. Venus doesn’t seem to have enough water in its mantle and upper crust for the same processes to occur. It might, however, do something completely different yet with similar results. We don’t yet know what so much water-free chemistry with a hot surface might do.

(3) Energy – deuterium is 150 times more prevalent than on Earth and might need removal from what hydrogen is available in the clouds to make potable water. Thus it’s a natural fusion fuel resource, though diffusely spread throughout the clouds. Above the cloud decks the energy flux from the Sun is almost twice Earth’s – and almost as much is reflected back up by the clouds as rains down from above. Thus solar energy is abundant.

(4) Gravity – Venus’s surface gravity is 90% Earth’s, so human health issues of ‘low gravity’ will be non-existent. Gravity also makes some industrial processes easier and that will be a boon.

(5) Space – at the 1 atmosphere level of the atmosphere Venus has 90% of Earth’s surface area, thus 3 times Earth’s dry-land area. Of course any colonies will need to float, but breathable N2/O2 mixtures are lighter than the ambient CO2/N2 mix. Thus vast inflated habitats will float naturally in the nicest part of the planet. The super-rotating atmosphere will mean the effective day-night cycle will be just 4 Earth days, not the 116.7 days of the rocks below. Thus a vast area for building habitats, if so desired.

(6) Any suggestions? Make a comment and let me know.

18 thoughts on “Resources of the Solar System 2: Venus

  1. One point I forgot to add was that enough shading by floating habitats would eventually cause the atmosphere to cool enough to lower the acid clouds. Sulfuric acid decomposes into gases when it gets above ~338 C or so, but enough shade will mean the surface will get to that point and the haze-free layer will be replaced by low level fog. Eventually that’ll mean less heat will reach the surface as high cloud tends to keep the NIR emitted by the surface from escaping to space. Potentially a feedback loop will cause the surface temperature to drop dramatically – from 735 K to 600-450 K – making the surface (marginally) more accessible. Once the temperature drops below ~304 K, then the carbon dioxide will begin liquefying since its critical point is at 304 K and 73.82 bar. But whether it would ever get that cold is anyone’s guess. The rain-out process would continue down to a CO2 partial pressure of 5.173 bar at 216.55 K, beyond which the liquid phase is unstable. But that’s a distant prospect indeed since the crustal rocks probably have a lot of heat to lose.

  2. If Venus was put into permanent shadow, I wonder how long it would take for the CO2 in the atmosphere to freeze out, then if 2/3 of the nitrogen rained out you’d be left with a planet with 0.9 G and 1 atmosphere pressure.

    If the dry ice and liquid N was at one pole, the other pole could be tropical without too steep a temperature gradient between them.

    1. In the 1960s a model Venus was proposed with frozen water ice caps and 300 C equatorial conditions. However those multi-hundred degree gradients are unsustainable in realistic atmospheres. Dry-ice can remain solid at relatively high temperature if under several kilobars pressure. Such can be created inside C60+ molecular cages.

  3. Bear in mind that we’re not talking about a natural planetary environment, but rather one in which radiation reaching the planet is strictly controlled for a given purpose.

    While controlling the liquid N2 might be a challenge, I don’t see too many difficulties controlling the dry ice.

    How about as the atmosphere is cooled the CO2 is controlled to form a ring of 15km high mountains at one of the poles, (though it could be made to happen at whatever location the geology dictates is most appropriate) the area enclosed by this ring is then cooled so that the excess N2 precipitates out there, N2 remains a liquid at 0.125 bar and -210C and the mountains isolate this N2 ocean enough from the bulk of the atmosphere so that the little heat that is brought in is radiated away to the eternal night experienced at this location without causing enough N2 evaporation to be a problem.

    Whilst the mountains continually flow outwards as does the Antarctic ice cap on Earth, they are also continually replenished by atmospheric CO2.

  4. Hi Andrew
    Nice idea. That might actually work – if necessary. The amount of N2 isn’t excessive and can probably be adapted to easily enough. But the idea of storing the CO2 as polar caps is a good idea by itself without that particular tweak. Venus has essentially no seasons so it might be feasible to cause it to eventually pile-up at the poles.
    The cooling timescale of the atmosphere can be roughly estimated from the heat content of a column of air, which is approximately ~5oo GJ/m^2 of radiating surface, and the effective temperature, which is 235 K. That means a characteristic time of ~90 years.

    What might speed it up significantly is if Rayleigh-Taylor instabilities can form, producing huge bubbles of hot surface gas to rise as cold upper-atmosphere starts descending. That kind of advection might raise the effective temperature of the atmosphere’s radiating surface. If it could all radiate at the average temperature (~630 K) of the whole atmospheric column, then the heat would radiate away in less than ~2 years. So the real timescale is probably somewhere in between the two extremes. The geometric mean is ~13 years. The only way to get a more definite estimate is a full GCM allowed to evolve until the CO2 is all frozen out. Got a spare supercomputer handy?

  5. You’re probably right about leaving all the N2 in the atmosphere, it would provide some protection against fast particles.

    Better to freeze the CO2 out at one location rather than two, it could be piled higher and so occupy less area.

    Can I now claim that terraforming Venus would be easier than terraforming Mars?

  6. Hi Andrew
    Unfortunately Venus is too dry to terraform without a massive import of water from the Outer Solar system. That’ll make the job tougher than Mars for sure, because we know that Mars is pretty wet, with significant groundwater just below the surface over much of the planet. If we could magically cool Venus overnight most (all?) of the few centimetres of acid/water in the clouds would vanish into the parched regolith. To give it just a fraction of the water on Mars or Earth would need diversion of multiple comets and their controlled fragmentation and careful impact. And not small comets full of CO2 like Hartley 2. A mostly water-ice Kuiper Belt cometoid or two would be ideal – the collision fragments of Haumea perhaps?

  7. Hi Andrew
    A planetological terraform is wasted effort really. Better to aim for making a planet habitable, yet different to Earth. The needed nitrogen level is a matter of considerable debate – we debated this very point on the “New Mars” forum for ages. In the end all the old misconceptions about enhanced flammability from excessive fractions of oxygen were really about absolute partial pressure levels of oxygen. If a terraformed Mars had 200 mb of O2 and 200 mb of N2, then everything would be dandy and things no more flammable than on Earth. Potentially an enhanced level of CO2 could be used as buffer gas because similarly its toxicity is from high partial pressures, not high relative proportions. About 50 mb of CO2 could be adapted to by almost everyone. Thus 200 mb of O2, about 150 mb of N2 and 50 mb of CO2 would be a breathable mix.

  8. “A planetological terraform is wasted effort really” not sure I agree, but ok, you’ve gotten it down to importing 4 tonnes of N2/sq M, how would the resulting environment compare to a cool Venus with 4 tonnes of H2O/sq M? That should be enough to service a functioning biosphere.

    Think I still prefer Venus.

    Since we’re talking about using mirrors and sun shades to help terraforming, is there any reason you know of that means we can’t do Mercury as well? 4.5km/sec escape velocity only a little less than Mars, and surface gravity the same as Mars.

  9. I’ve been working on the assumption that for each of the three planets sun shades at L1 and/or mirrors at L2 would be a prerequisite for terraforming, how else do you freeze Venus’ atmosphere? How else do you get a length of day on Venus or Mercury that would allow an Earth type ecology?

    Such space based insolation control would be the scaffolding for the whole process, and it’s not like the expenditure would be great compared to the other expenses, eg moving those trillions of tonnes of volatiles from the outer solar system.

    To get the best cost/benefit these structures would be as substantial as solar sails, so would need to be designed to minimize the effects that light pressure would have on them, for the sunshades that would mean changing the direction of sunlight by the smallest angles possible.

    Having thought more about how much to change these worlds to make them Earth like, I think bringing in one fifth as much N2 to Mars, or one tenth as much H2O to Venus is as sensible as expecting people to live in $2000 tin shacks rather than $200,000 houses, it’s that extra effort that would make the whole thing worthwhile, remember that terraforming these worlds would have to compete as business prospects and living environments with domed cities on Luna and O’Neil colonies in space, environments I’ve always imagined as very comfortable indeed. Living in thin cold atmospheres on desert worlds wouldn’t attract too many resident investors. They should be worlds as rich in life as the Earth.

  10. Depends on the aesthetics of the age in which we try to terraform those planets.

    As for the soletta (a) we could balance the outward pressure against its weight by placing it slightly sunwards of the Sun-Venus L1 point.
    (b) it would then need to be ~twice Venus’s diameter to adequately shade the planet. That’s a huge power collection area and would be sufficient to power mining & delivery operations importing hydrogen from Uranus or methane from Triton or Pluto. Methane? I hear you think. At delivery speeds it would pyrolyze into carbon and hydrogen, which would react with the CO2 via the Bosch reaction, creating more carbon. We could give Venus oceans and coal-beds or diamond-dust sand.

  11. “As for the soletta (a) we could balance the outward pressure against its weight by placing it slightly sunwards of the Sun-Venus L1 point.”

    Yep, thought of that but I’m a bit doubtful that alone would be enough to balance as light a structure as could be built, and the further you shift it sun ward of L1 to increase the gravitational pull, the larger the area of the structure has to be.

    As far as covering it with solar cells and then beaming the energy 30 AU to Uranus where it would then have to be collected again, I think it would be more practical to just build another soletta at Uranus and concentrate the sunlight there, mind you at that distance from the sun and at 20% efficiency, a 24,000 km diameter collector would only produce around a hundred million megawatts of power…

    This mining the gas giants though does bring me back to the original topic of your post, habitats floating in an atmosphere. Imagine vast habitats tens of kilometers across floating in the atmospheres of the 3 smaller gas giants supported by hot hydrogen balloons, the balloons themselves would serve to concentrate the sunlight onto the habitats (admittedly not an original idea) .
    That would give us 7/8 in terms of colonizing the planets. :-)

  12. in my humble opinion, i can say that we can’t consider the planet Venus as one of our resources yet. i dunno how it is being define to enable planet Venus to be also part of our resources. in fact, i guess that we can penetrate first Mars ahead than Venus or have their been any exploration already to planet Venus in the past? well, perhaps in some ways we can acquire resources of our Solar System in Venus.

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  13. Hi Sabertorque
    Your little ad-link makes me suspect you’re an advanced chat-bot (please allay my suspicions), but your question is worthwhile. My “Resources of the Solar System” series is a (very slow) roam through the Solar System from near the Sun out to Pluto/Eris. Next stop is Earth/Moon, Mars, Main Belt, Jupiter-System, Trojans etc… So I will get to Mars eventually. My discussion of uranium resources in the continental crust of the Earth is one part of the “Resources of the Earth/Moon System”. You might find that to be an interesting discussion.

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