Thursday 13 October 2016

How to live on Other Planets: Mercury

Nuclear war. Collapse of the biosphere. Catastrophic global warming. Space elevators. Whatever the reason, Earth is no longer green and friendly. Many want to live on other planets, and have the resources necessary to go.
So how will life on other planets look like?


The first on our list for this series. Known for being our Solar System's equivalent of a moth flying too close to the light, it is a planet of extremes. Sunlight varies between five and ten times the intensity on Earth, leading to surface temperatures of up to 700KThat is 427 degrees Celsius. Aluminium loses 90% of its strength. Astronauts will boil in regular spacesuits.

The cold side is not any better. Without any atmosphere, it drops to 100K, or -173 degrees Celsius. That is cold enough to freeze oxygen. It rotates three times (three Mercury days) in two orbits (two Mercury years). Originally much larger, it was struck by an object thousands of kilometres wide: a massive impact that stripped off most of the crust and mantle. Today, it is the cold, naked core of that planet.


Polar craters with unusually reflective basins highlighted in yellow.
One of Mercury's distinctive features is the existence of craters and crevasses at high latitudes (near the poles), deep enough to keep their lowest point in permanent shadow. In these dark pits accumulate volatiles such as water. Scientists believe that a layer of dust and sediments on top of the volatiles prevents their sublimation into space.

So, on the smouldering inferno of Mercury, there are frozen lakes. They contain water and probably ammonia and carbon too. These are all the ingredients needed for an autonomous colony!

Mercury is only 40% wider than our Moon, but its density means it produces a gravity of 0.38G. This is believed to be sufficient for preventing the effects of microgravity, such as bone loss, eyesight problems and muscle atrophy.
Notice the 'flux transfer events'
The planet's iron core is still active. It produces a magnetic field, giving Mercury a magnetosphere about 1.1% as strong as Earth's. It is insufficient to reduce the radiation at the surface in any significant way. Worse, it can reconnect with the interplanetary magnetic field in gigantic magnetic storms, producing funnels that concentrate the solar wind onto a spot on the surface.

The lack of atmosphere, like most places in the Solar System, means that anything exposed to sunlight receives the full dose of UVs and X-rays.


Mercury is nothing special in terms of the minerals available at its surface. Rocky or metallic asteroids offer the same without any digging or any gravity to slow things down. However, it has two advantages over the asteroids:

-Concentrated volatiles
-Plentiful energy

Unlike on a barren rock in space, water is freely available. The dark pits mentioned above contain hundreds of trillions of water in total. They can be connected with overland travel routes (rail, roads, tunnels) or simply pumped from extraction site to mining site.
Water marked on Mercury's North Pole.
An asteroid miner would have to get his water from a comet, which is separated by millions of kilometres, thousands of meter of deltaV and several months, if not years, of travel.

Solar energy is the other advantage. With 5-10x the intensity of sunlight on Earth, solar panels can be expected to produce up to 5kW/m^2, more as efficiency rises. With thin film technology, this translated into energy densities rivalling nuclear reactors, and vastly exceeding them when power generation equipment is taken into account (the solar panels produce electricity directly).

Energy on Mercury does not need fissile materials, and can be produced with a much lower mass investment compared to elsewhere in the solar system. It makes perfect sense to sell this energy as laser beams shooting off into interplanetary space. Without an atmosphere to absorb the beam, low-wavelength lasers can be used to beat diffraction at long distances. 
MMinerals are easier to extract from ore thanks to gravity. At 0.38G, it is significant enough to allow us to use most of the techniques already developed on Earth. Microgravity would require more complicated processes to do the same. The abundance of sunlight means that simple and robust solar-thermal propulsion can become powerful enough to lift cargo out of lower orbits quickly. Tethers, laser-ablative propulsion or electromagnetic accelerators can handle the launch from the surface. Mercury's soil is rich in magnesium (steel industry), sulphur (needed for growing food everywhere) and chlorine (organic chemistry) compared to other sources.

The major downside to an industry on Mercury is the deltaV requirements to get anything from Mercury Low Orbit to the rest of the Solar System. It takes 12.5km/s of deltaV to get from Mercury to Earth. This is very expensive to do by chemical rockets (4500m/s exhaust velocity means you need 16 kg of propellant for every kg of rocket) and difficult even with nuclear propulsion (4.9kg of propellant per kg of rocket).

Cheap solar energy around Mercury allows the effective use of electric drives with 0.4kg of propellant per kg of rocket. They can perform the braking or departure burn near Mercury, which would otherwise cost 7km/s. This reduces the deltaV requirement of a Mercury mission to something comparable to a Mars mission.

In conclusion, despite all of its metals, minerals and volatiles, Mercury is best used as a workshop for energy-intensive items. These high value products are the actual items being sent to the rest of the Solar System, off-setting the cost in propellant. Examples include energy-intensive microelectronics and electro-formed precision components.
An upside to Mercury's position is that it can send out cargo four times a year to anywhere in the Solar system, thanks to its synodic period. Mars, in comparison, requires a two-year wait between minimum deltaV trajectories becoming available. It allows a Mercury colony to be built up quicker, and produce returns twice as fast. This might become of lesser concern for time-insensitive trade, such as bulk metals or volatiles, that can use low thrust electric propulsion.

The Mercury Colony
As described above, the best place to position a Mercury colony is in the shadow of a large, polar crater. Average temperature in the shadow is 108K, or about -165 degrees Celsius. Large amounts of water can be found, covered in dark dust rich in hydrocarbons and unknown amounts of nitrogen.

Solar reflectors are mounted over the edge of the crater. They bounce down calculated amounts of sunlight to where it is needed. It is concentrated on certain parts of the frozen lake, to melt it, and diffused over working areas to create warmer conditions.

The colony will have three main sections.

The first is the habitation section. It consists of inflated living areas and farms sunk into the lake. It will have transparent roofs to take in reflected sunlight. The walls will be insulated, but heat will escape and partially melt the surrounding lake. It will create a muddy ring around the colony.

The habitation section has two levels. The upper level is warm and well-lit, but is not well protected from radiation. It is where colonists enter and exit from, and where most machinery is located. Solariums and greenhouses can be installed near the transparent roofs. Entering and leaving the colony is done through hatches in the roof. The lower level is completely buried under frozen water. It is well protected from radiation, but might end up feeling claustrophobic to some inhabitants. Flexible walls hold in the breathable atmosphere, but escaping heat will melt the outside into an ice-water slush. The walls might move, flex and bulge with temperature variations too.

Walkways extend out of the habitation area and over the lake. It connects to the powerplant and the factory.
PS10 and PS20 solar thermal powerplants in Seville, Spain.
The powerplant uses focused sunlight and boiling water to generate electricity from turbines. It is cheaper and lighter than producing the equivalent energy from solar panels. Some of the energy goes into melting water and splitting it into hydrogen and oxygen. This is used to refuel rockets landing nearby. The rest goes into powering the factory. The most visible features are the large black panels extending up into the sunlight, and the pipes snaking into the lake to extract water.

The factory is the most important component of the colony's survival in the long term. It provides the main economic benefit, and gives work to the colonists. Automated mining machines depart from the factory and onto Mercury's surface. They are covered in gold foil to protect them from sunlight, and drag large tractor-scarpers and buckets behind them. Seen in action, they resemble white flares slowly leaving a dark trail of disturbed earth behind them.
The mining machines return to the factory and dump their load. It is sorted and separated into useful minerals and metals. Some are packaged into large blocks of pure elemental material, others are processed into chemicals. The most valuable items require precision machinery and lots of energy. If it is microprocessors, they might follow a 'rad chain', similar to the cold chain existing for frozen food products. A rad chain ensures that electronics are never exposed to naked solar radiation, and kept inside radiation shielding from production through transport and until delivery.

The factory will send its products to the launch site. This can be an orbital tether, a laser battery powering rockets or a mass driver.

The dangers
Mercury's surface.
Mercury presents some unique dangers.

As Mercury is an airless world, decompression is a significant risk. This is especially important for space-suited colonists. Inside a habitat, the ice that the buildings are sunk into slow down decompression enough for the walls to be patched up.

Freezing or getting trapped might be counter-intuitive, but it is the risk of living on a lake at -165 degrees Celsius. While water melts at 0 degrees Celsius, the lake can contain frozen oxygen or nitrogen. They evaporate and much lower temperatures, low enough that the heat from a human body can cause them to burst out of their bubbles and create a sinkhole. This is made worse by the fact that most of the lake will be covered by gray-brown dust and look like solid ground. Getting stuck in the ice can cause hypothermia and death...

Overheating will happen. A man in a space-suit might be asked to hike out to a damaged mining robot and fix it. He will take the reflective cover, the water cooler, the insulated sheath... but these will only provide a few extra minutes in case of an accident. The combination of intense sunlight and insulating vacuum will mean that direct exposure to sunlight is a messy, if at least rapid, way to go.
The reflective, insulating sheets used for the James Webb telescope.
Blinding might be a more commonplace danger. With everything covered in reflective surfaces, the risk of catching some of the sun's rays at an unexpected angle is great. This might enforce the use of dark sunglasses even in shadowy or dim areas on Mercury.

Orbital debris is very dangerous on an airless world. Without anything to slow them down, even the tiniest speck of dusk makes it to the surface without slowing down. These can penetrate habitats, kill people on the surface or wreck equipment. Armored plates might become habitual features of anything designed to work on the surface. Thankfully, 0.38G gravity might not make them much of a burden.
Hypervelocity impact
Spaceships in orbit face dangers related to the intense sunlight. Radiators are less efficient and have to angled edge-on to the sun. Large tanks of liquid hydrogen become dangerous explosives, as they catch a lot of sunlight, and the transition of the contents from a liquid to a gas can rupture the tank.


A Mercury colony will start out in craters, and scrape the surface for minerals.

As colonists increase in number and decide to spend a large part of their lives on the planet, more permanent habitats will be dug into the rock around the crater. This will greatly improve radiation protection, enough for infants to develop with no risk of cancer.
In green, the habitable ring.
Eventually, the craters will not be enough. There exists a vast ring of habitable underground area around Mercury's poles. Only 70cm deep and covering 200 thousand square kilometers, they offer comfortable living conditions at a constant 22 degree Celsius (room) temperature.

Mercury's industries will start focusing on planetary megaprojects. A 2km wide reflector can focus an infrared (1000nm) laser beam on a 1km wide target at the distance of Jupiter! Even with transmission and conversion losses, it will provide plenty of cheap energy... and a potent weapon.


  1. Mercury has always interested me as a place for a colony. Counterintuitively, I would think Mercury will be a much more important destination for space colonization than Mars, mostly for the reasons you gave. Mercury could become one of the economic hubs of the Solar System in the 22nd century.

    If I were to build on Mercury, I might dig a shaft at one of the poles and use it as the atrium for a city lining the walls. A series of reflectors would bring sunlight down the shaft. You could almost think of this as an inside out skyscraper (or arcology would be more fitting in this case).

    I notice you didn't mention solar sails. Of all the places in the solar system, this is by far the best place to build and deploy them, especially when sending cargos to distant markets in the asteroid belt or customers on Neptune.

    Looking forward to the rest of the grand tour.

    1. Indeed, Mercury is an attractive place for colonization, but Earth-centric views places Mars as a closer destination.

      Solar sails are of some interest, but I doubt they will every carry the quantities of cargo needed to compensate for very slow travel. Solar electric, even solar thermal, beats them from an economic point of view.

    2. "Solar electric, even solar thermal, beats them from an economic point of view." Hardly. These systems are based on a required propellant that must be produced, transported and transferred to the vehicles. This requires on on-site infrastructure whose cost must be taken into account. Sails, by design, do not need as complex an infrastructure. In their case, they need a system that delivers a cargo to the sail from Mercury's surface - a maximum delta-v of 4.2 km/sec. with ~3.5 km/sec. being more likely. Also, so far as sails being 'slow' this is a function of the payload mass/sail area and can be established for very fast transfers. Add zero-maintenance reuse; low initial launch mass (~4,000 kg for a sail 820 meters to a side) and likely lower production cost compared to more complex systems (above), combined with the 3- or 4-fold launch window opportunities noted for Mercury. . . Solar sails are a very good bet for making Mercury a low cost construction site and viable in commercial operations.

    3. Please add some sort of name to your comment, or else the Spam filter will catch it.

      By economic point of view, I was thinking in economics terms: a solar-electric/thermal propulsion system will allow for a very fast turnover compared to solar sails. If you can buy, transport and sell your products four times in the time it takes for one solar sail shipment to arrive, you will make more money in the end, even after paying for propellant.

      I doubt solar sails have lower production costs that solar-electric engines. The sails have to be very thin and smooth, which requires a large amount of very fine and consistent work. The only cost department they will save on is propellant costs: all others, such as lifting the payload to orbit, transferring it down to a surface and so on, do not benefit from the solar sails.

      But you are correct in one thing: I need to sit down and take a proper look at how much performance we can get out of solar sails.

  2. What about radiation on mercury approach? I was under the impression that most of the radiation in space is from the sun, since every other source is light years away. How would you shield the spacecraft, and is any amount of shielding adequate to reach NASA's tiny risk thresholds?

    Would a colony on an asteroid have less problems with the radiation? It's not just the health risk, in the 'early days' of such a colony, you'd expect that teleoperated robots would have some serious limitations and it to be very convenient to have a human in a skin suit doing maintenance in person. That's something you would have a tough time doing on mercury since X and gamma rays from the sun are going to go right through any portable "solar shield" an astronaut brings out when he goes to work on maintenance.

    Not that this isn't all basically just fantasizing. Aren't there orders of magnitudes more resources left on Earth to be harvested, albeit at above today's market prices? There's the ocean floors, vast tracts of less developed nations, and so on. Not to mention recycling, since the only resource modern industry "consumes" is helium and energy. (helium because leaked helium escapes to space, energy obviously is the difference between fuel and CO2 in the air)

    1. The amount of shielding required for a Mercury colony is measured in centimetres of metal plating with water behind it, or about a meter of dirt plus water behind it.

      Both are easily set up. Metal can be slag surplus from the refineries, and the water could be natural lake formations (the two types of radiation shielding do not have to be in a specific order).

      As for spacecraft coming to and fro, it depends on their cargo. Dumb cargo can take months of radiation without worry, so slow and efficient electric drives are sufficient. Fragile cargo like humans, food (?) and electronics will have to take fast transport. Radiation shielding requirements are a balance between extra plating or lower travel times.

      In a setting where interplanetary trade is possible, fast human transport will have to include nuclear rockets with mass ratios commonly seen on chemical rockets. This will reduce travel times to manageable levels. With a mass ratio of 10, even a simple nuclear thermal solidcore rocket like NERVA can produce 20km/s of deltaV, and cross the 77 million Earth-Mercury distance in 44 days.

      Humans on Mercury will travel around on wheeled bunkers. The reflective suits is for when everything goes haywire, the bunker is stranded and you cannot call for help. A quick run to the nearest shelter might cost you a tumor, but its better than frying alive.

      Earth is a great place to stay in. But there will reach a point where it won't become the best place for a fraction of the population. If I told you that you can do your current job, for three times the salary all expenses included, aboard a cruise ship (with a thousand other people) for 1 year, would you want to? Many will.

      Now replace that cruise ship with a mining operation on another planet, drawing in ridiculous profits.

      Heck, I'd go if it meant paying off my mortgage in 2 years instead of 25 years,

    2. Do you think humans will actually do this or do you think they'll crack the problems behind AI first?

      It seems like progress on AI is happening far faster than at any point in the past, because several different groups have found refinements on artificial neural networks that boost their performance far above anything before. And the necessary hardware - GPUs, custom chips - is finally available with enough performance and complexity to make a difference.

      That was why AI progress seemed so slow since 1956 when it was started. It wasn't a matter of inadequate software, it was actually a matter of inadequate hardware.

      I know it's still an immense gap to "human" equivalent general purpose AI, but it's not a linear process. AI developers can quite possibly bootstrap their way there by building advanced "helpers" that internally use ANNs to do all the well defined, repetitive tasks in the way of designing an AI.

      What might these "helpers" be like? Well, you'd need some to properly visualize a synapatic map of the human brain. Once that mapping is done in a decade or two from today, you'll need some serious visualizing tools to convert 86x10^12 connections to the mere few thousand distinct subsystems actually in a brain.

      Other tools could spot the patterns in a subsystem and essentially create the equivalent, cleaned of noise, pattern in an ANN so you could play with it. And so on. Essentially these advanced tools would act like the scaffolding and heavy construction equipment needed to actually construct an intelligent system with that much complexity.

    3. The discussion of the future of AI should have its own dedicated post, but I'll say this for now:

      The gap between 'expert system' and natural AI is as big as the gap was between chemistry and nuclear physics. It is a conceptual divide that requires a whole new discipline of study to emerge. Our current theories are as reliable as phlogiston and ether.

      It's not physically impossible to create natural AI. Our brains do it all the time. It's just that it requires a SF author to make the same leap in realism as FTL travel or antigravity.

    4. But FTL travel and antigravity are not even known, by our current understanding of physics, to be possible in any form at all, no matter how advanced technology becomes.

      We know that even if we NEVER solve the problem you mention, we could just copy existing human brains if we have the advanced manufacturing and teardown/imaging technology needed. (the manufacturing is to make a synthetic brain, the teardown/imaging is to scan a preserved brain to clone it)

    5. Currently, we do not understand why the brain is more than the sum of its parts, in other words, why large-scale behaviour cannot be replicated using smaller models. It leaves room for theories such as 'quantum consciousness' and 'scientifically reasoned souls' to remain unchallenged.

      Also, I have the image of a well-meaning dysotopia that ends up cloning and growing humans that are genetically engineered to act as low-level natural AI. It takes only one person to question the morality of GMO wetware to reveal the horror of it all. Imagine if your CPU woke up one day and displayed 'HELP' on your screen!

    6. On AI see this
      especially halfway down "AI is possible...but AI won't happen"

      Jim Baerg

  3. WRT solar sails, ultra lightweight metal films were investigated by K Eric Drexler as far back as 1975 (he even made samples) for high performance solar sails, and with a suitably minimal mass sail, it is possible to get from Earth to Pluto in as little as 3 years (although the only plausible way a solar sail racing to Pluto at that speed could stop is "Lithobraking". So I wouldn't count out Solar sails for product delivery from Mercury.

    Solar sails should be another subject to look into at a later date.

    1. Quite right. I was wondering mostly about the solar sail mass to payload mass ratio required to get useful acceleration.

    2. Yeah really. Thrust per photon is so terrible, I always assumed that the sail would weigh too much.

    3. I removed the duplicate comment.

    4. A sail weighing less than 4,000 kg can deliver a 20-ton payload to Mercury from earth in a flight of about 2.1 years. The same sail can deliver a 10-ton payload in about 1.6 years. When it comes to inert items where space exposure is not a main issue, this is very reasonable. Since sails launch on the same synodic period basis as most fuelled systems, you only have to add 115 days to these figures to get the total delivery time for an ordered item. In contrast, payloads delivered to Mars from Earth would need .7 years (actual flight time) plus 2.2 years synodic waiting period. This is why Mercury will cost less to develop than Mars.

    5. An 83% payload ratio is excellent! It will beat out chemical propulsion for sure.


      A solar-electric propulsion system with 20km/s exhaust velocity and averaging 2.5kW/kg between Mercury and Earth, massing 10 tons and using liquid hydrogen as propellant, could get the 20 ton payload across in barely 60 days by using 51.3 tons of propellant (30km/s deltaV). It could make the same trip 12 times, ignoring any synodic period. Its initial acceleration will be 3mm/s^2, rising to 0.08mm/s^2

      But... you have to have your payload be worth more than twice its weight in liquid hydrogen, plus service costs. This might rule out cheap and plentiful stuff such as nickel, iron, copper... those are the products that are most likely to be relegated to

  4. Nice article, keep it up!
    Will you write something about terraforming Venus, especially its atmosphere, in future post?

    1. The 'how to live on other planets' is a series that will cover every single habitable spot in the Solar system. Venus is next :)

  5. Thanks for your great blog! It's very helpful. Looking forward to the rest of this series. Is there any chance of you doing a post on terraforming sometime? Don't know if terrarforming is even remotely possible though :)

    1. Thank you for your support!

      Terraforming is an energy-intensive and long-duration operation with dubious economic benefit. It is possible, and we can complete 90% of it with current technology, but we would have to develop a level of patience even pyramid-builders did not display.

    2. A lot depends on motivations. You could consider the Terraforming of Mars to be a sort of long term civilization level project to bind people together for a thousand years or more achieving a common goal. Most Empires don't last anywhere near that long (the Res Publica Roma only lasted @ 400 years, and the follow on Imperium lasted for another 400, so the best known Western civilization was around for a cumulative 800 years.) Commercial Empires like the *Serenìsima Republica Vèneta* also had similar lifetimes. Someone well versed in Chinese history could tell us how long the various Dynasty's lasted, but I suspect that we would only be looking at a few centuries.

      Long term political, social and economic stability is one of the goals people try to achieve, and a millennial project along these lines might have far more attraction than the simple economic payoff when Terraforming ends.

    3. If mars can be terraformed in the same way that Britain turned from forest to fields, or urban areas spread over the planet over millenia, i.e.: incrementally, then it could happen.

      The Taj Mahal, the Pyramids, and many ancient monuments have all been studied and maintained by polities long after their original builders died out. They were maintained due to the pride they brought their new owners. Perhaps terraforming could be seen as a form of national prestige, incrementally undertaken by the superpower of the day, with no self-respecting power wanting to be seen dropping the baton when they take over from the previous group.

  6. Your thinking is correct Geoffrey, but I am looking at this as being more internalized. The "Eastern Empire" might have no overarching interest in Mars, except as a way of thwarting the ambitions of the "Southern Empire", but the Martians themselves might see this as a quasi-religious calling for themselves and their descendants, and a way of mobilizing capital and labour to stay on Mars for generations working towards the ultimate goal of walking unprotected on the surface.

    How this would play out in fiction might be to make Mars considered a sort of sinkhole of investment capital, and a place where most people are considered to be cultists following the thousand year vision of Terraforming. People on asteroids or the moons of Gas Giants won't be drawn into projects like that because they are effectively impossible where they are, so more "practical" short and medium term projects like building domes or tunnelling into the interiors of asteroids will be the general direction for these people.

    I wonder if there might even be a distinction between the civilizations living in free space (asteroids, artificial colony structures) and those burrowing into moons and tied to their planetary system?

    1. I kind of disagree with both of you. Extremely long-term projects require equivalent gains for the investors, but we'd end up with:
      -Investors dying before the project is completed.
      -The end result being a habitable planet... which you can't really sell.

      There is no financial or economic method to compensate investors for projects that require several lifetimes to be completed. Terraforming projects do not produce any valuable assets until they are completed. Once you have a habitable planet, you'll be able to sell access to it indefinitely, but you'd never realistically get your money back. 'You' in this equation would be governments and megacorporations. The only way to make a profit would be massive immigration, and the masses cannot give up so much money on arrival or through taxes that they become poor. They would simply point to the orbital space stations above and say: I lived my entire life there. What's so much better about this planet?

      What I think is more realistic would be habitable sections, and techno-genetic adaptations.

      Habitable sections are something we are familiar with. It is a large-scale version of a space colony, placed on a planet. Unlike space-going habitats, these planetary 'parks' can grow organics, food and medicinal products in very large quantities, with little risk of radiation damage. That is their economic advantage. These 'green spots' on the planet are isolated from the inconvenient atmosphere and temperature, but have easy access to volatiles such as oxygen and water.

      In the shortlist of posts coming up on ToughSF, I speak of genetic modification and technological augmentation, comparing and contrasting the two. People will find themselves genetically engineering for compatibility with technological augments. These augments will allow people to live on Titan or Mars as simply as humans do on Earth. It is vastly cheaper for willing individuals to adapt themselves to the environment, than for the planet to be adapted to potential customers.

  7. From a capitalistic and free market perspective, you are quite right there is no "payoff" for the initial investors. But people have lots of other motivations as well....

    Consider the great cathedrals of Europe. they were erected for a spiritual purpose (the glory of God) and to proclaim the power of the Roman Catholic Church over the spiritual and temporal realms. Most of these Cathedrals took over 200 years to build, in an age where the average lifespan was about 40 years. Similar calculations may have applied to the Acropolis, the Great Pyramids, the Hanging Gardens of Babylon, the Temple of Solomon, the Great Wall of China etc.

    Martians might develop some similar beliefs, so conventional economic calculations based on supply and demand or ROI are no longer relevant (although economics will still play an important role). I might suggest the real reason to carry out a terraforming project is to bind capital and human resources to a place, rather than allow them to be speculatively dispersed across the Solar System (Martians want future generations to live and work on Mars, not emmigrate to Uranus or Mercury). A quasi religious motivation like "the inevitable spread of life across the Universe" could be invoked to provide the philosophical foundation. And of course, scientific advances might mean that the initial investors would actually be alive one thousand years after the project's start to see the culmination of their dreams...

    People do far stranger things.

    1. No pay-off for the original investors? Apollo lasted only 15 years altogether, yet all of the companies involved ('investors' by analogy here) made profits and were able to make gains on the stock market to the extent the market was able to perform. The initiators of a terraforming project would realize a personal profit through their connection to the various industries involved.

    2. Well the american government didn't try to recuperate costs by selling moon rocks, did it? It just footed the bill under 'Cold War expenses' and hoped secondary actors gained benefits, such as the aerospace, military and electronics industries.

      Also, you can't really convince a Wall Street exec that he'll gain money by investing in a colonization effort by creating connections... he can do that over a game of golf!

  8. Are we sure terraforming can't pay for itself? Green house gas emitting factories cheaply producing goods, tourists invited to watch ice comet bombardments... On the latter point, what if terraforming was a tourist attraction in and of itself?

    Regards Mercury, its placement near the sun and lack of athmosphere means it would have access to mirrors as defensive weapons, could produce most of its own materials and would have cities deep down in the crust. A planet in such a defensive position would be well placed to dominate the solar system at least for a time. Even if all its surface defences were knocked out, the only way to take control of the place would be to send ground troops into the tunnels below. Not a pleasant prospect.

    1. The cost of moving a lot of ice comets (after finding them, sending a probe out there, covering them from sunlight and securing them) is probably far, far greater than the potential earnings of a tourism industry.

      Plus, safety regulators might not want tourists sitting under kilotons of ice falling on their heads.

      If terraforming becomes a tourist attraction, its progress would be limited to the waning and waxing of public enthusiasm.

  9. Only just discovered this blog and am having a great time reading through it! Keep up the good work. Your Mercury colony idea reminded my of a lunar habitat I conjured up literally in a dream a few years back and quickly sketched out before I forgot about it. Just wondering if you think this makes any sense? The central idea is to provide a 1g environment by supplementing the lunar gravity with spin. I'm not an engineer though, so I have no idea what is actually feasible in terms of materials, etc.

    1. I'm glad you find these posts interesting! Don't hesitate to comment wherever you have a question.

      The problem with massive spinning constructs is that they wobble. The taller it is, the larger the wobble, with spheres being the worst offenders, and disks the least 'wobbly'. The lateral forces have to be compensated for structurally. For something the size of a colony, it would require a dynamic suspension system anchored by miles of metal beams dug into the surrounding rock to spread the forces.

      I think it is just more practical to let the colonists live in 0.4G, and move them once they develop problems. If we have interplanetary colonization, we have interplanetary transport. Similar to an oil worker staying in harsh Alaska for two years, then moving back to continental USA to enjoy his money, a colonist could go work on Mercury, then depending on how much money they make, risk it on Venus or pay premium for a spot on the Overcrowded Earth (T) of the future.

  10. 4 years late, but I have to say this: the terminator on mercury is really slow. You could stay in the night side on the equator simply by walking. I could see gigantic colony rovers circling mercury to stay in in the shadow. Think bagger 293 mixed with a cruise ship, housing 600 inhabitants

    1. That's right! Kim Stanley Robinson made good use of this fact for his novel 2312.

      I don't see the utility of having a giant colony-rover though. It would be destroyed if it breaks down, whether due to mechanical failure from equipment that cannot be allowed to stop and rest, or random events such as a meteorite striking the road or tracks it relies upon.

  11. "Mercury is only 40% wider than our Moon, but its density means it produces a gravity of 0.38G. This is believed to be sufficient for preventing the effects of microgravity, such as bone loss, eyesight problems and muscle atrophy."

    I'm not sure about this: Mercury (0.377G) has almost exactly the same as Mars (0.378G) gravity-wise, and on your article for Mars you say that it's doubtful that that's enough. There's some studies of plants at Mars gravity (so it should be applicable for Mercury); most seem to suggest it's okay, but one found changes to the cell cycle even at Martian gravity. The threshold for plants seems to be somewhere between lunar gravity (which is worse than microgravity even) and Martian gravity. I'd give the URLs, but I worry that that won't pass the spam filter: I've previously posted them at the Wikipedia talk page for "Colonization of Mars". :)

    LCROSS found native precious metals in the permanently shadowed regions of the Moon: the paper "Prospecting for native metals in lunar polar craters" by Platts, Boucher, and Gladstone (doi 10.2514/6.2014-0338) suggests mass abundances 0.11% Ag, 0.52% Au, 0.53% Hg. This is probably from electrostatic dust transport. These are extremely high compared to abundances on Earth, and we could presumably expect the same in the polar craters of Mercury. So precious metals might be another Mercurian export, and there shouldn't be any worries about running out of gold for reflective surfaces. Might want to purify the water ice before drinking it because of all that mercury, though. :)

    1. The doi for the plant studies: 10.1111/plb.12031, 10.1038/s41526-018-0041-4, 10.1038/s41598-018-24942-7, 10.3389/fpls.2019.01529, 10.3389/fspas.2021.72915.

    2. Oops, I made a mistake: the 0.11% figure is actually for Au. The authors' model predicts this, in good agreement with 0.52% as found by LCROSS. Similarly, the authors predict 0.53% Hg, versus 0.39% estimated from LCROSS data. No figures are given for Ag.

      Still, those are tremendously high values, so the point stands. Some emission lines were also found suggesting the presence of Pt.

    3. Nice finds! I knew that mercury is good source of metals but not that precious metals could also be found at reasonable concentrations.

      It remains to be seen whether Mercury is a better source that metallic asteroids though. The deltaV cost for travelling to Mercury is very high, and you need a high thrust engine to land on it on top of that. Asteroids cost less deltaV to reach and you can use a single low thrust but high efficiency propulsion system for all your maneuvers.

    4. According to 10.1016/j.pss.2022.105608, even metallic asteroids should have Au abundances similar to on Earth; it's the PGMs proper where they are better. (True, economics may make it more worth it anyway to go to asteroids even for Au, to avoid pollution concerns.) Polar craters on Mercury and Luna are likely up to two orders of magnitude more concentrated in gold. But this is still not a good reason to go all the way down to Mercury when exactly the same process happens on the Moon.

      So I agree with your conclusion that the real point of industrialising Mercury is to make use of abundant solar energy, rather than to mine it for metals. The significance of this rather is that the polar colonies would pretty much have the complete periodic table in high abundance on their doorstep, so there's no such worry as there is for Jovian polities needing to trade with the inner system for heavy metals. Given the immediate self-sufficiency, the huge delta-V needed to get there, and (as Geoffrey mentioned above) the difficulty an invading force would have taking the planet's underground cities even after arriving, Mercury seems like it has the dystopic potential to become the Solar System's North Korea, holding the inner planets to ransom with laser weapons. I guess this fate could be avoided with advances in solar propulsion, so that its short synodic period that connects it with the rest of the system can actually get used more effectively. And given that Mercury is airless, perhaps Jupiter could retaliate with magsail-propelled bombardment. Hmm, an interesting storyline already! :D

    5. (I guess I should also add that this is by no means the only possibility, just one that has clear storytelling potential. :D)

  12. I Want to Colonize Mars Not Mercury