Trouble With Terraforming Mars
    By Robert Walker | December 16th 2013 12:58 AM | 67 comments | Print | E-mail | Track Comments

    Most science fiction and news stories describe Mars terraforming as a long term but simple process. You warm up the planet first, with greenhouse gases, giant mirrors, impacting comets or some such. You land humans on the surface right away and they introduce lifeforms designed to live on Mars. Over a period of a thousand years or so, life spreads over the planet and transforms it, and Mars becomes a second Earth.

    However no-one has yet terraformed a planet. There are many theoretical reasons for supposing it wouldn't be as easy as that. What's more, this process if it goes wrong could lead to a Mars that is worse for humans than it is now. It could so alter the planet that it can never be terraformed again in such a simple way.

    In this article I'll look carefully at some of the ways in which Mars is different from Earth and some of the issues with terraforming which suggest it might not be as easy as you think. We'll see that there are several ways it could fail if it goes wrong, with no chance to turn back the clock and try again.

    A living Mars, by Kevin Gill

    Perhaps Mars could look like this after terraforming - but many things could go wrong along the way, and it could revert back to a cold and inhospitable planet. After that it might be impossible to terraform it again, if most of the existing atmosphere and water was lost to space or turned to rock.

    There are many optimistic news stories about Mars terraforming. Other organizations such as Mars One want to land colonists on Mars, with no intention of terraforming it right away. But might they accidentally start off a process that will transform the planet as a result? If so does that matter?

    What happens if you make a mistake with a planet?

    Our only attempt at making a closed Earth-like ecosystem so far on Earth, in Biosphere 2, failed. There, it was because of an interaction of a chemical reaction with the concrete in the building, which indirectly removed oxygen from the habitat. Nobody predicted this and it was only detected after the experiment was over. The idea itself doesn't seem to be fundamentally flawed, it was just a mistake of detail.

    biosphere 2 sunset
    Biosphere 2. This attempt failed though much was learnt in the process, and many scientific papers were published as a result of their work. They were not able to produce enough oxygen and were not able to produce enough food. However this was mainly because of an issue with chemical reactions with the concrete, and didn't show that the basic idea itself was flawed.

    In the future perhaps we will try a Biosphere 3 or 4, and eventually get it right. When we build self-enclosed settlements in space such as the Stanford Torus, they will surely go wrong too from time to time in the early stages. But again, you can purge poisonous gases from the atmosphere, and replenish its oxygen. In the worst case, you can evacuate the colonists from the space settlement, vent all the atmosphere, sterilize the soil, and start again.

    It is a similar situation with Mars, there are many interactions that could go wrong, and we are sure to make a few mistakes to start with. The difference is, if you make a mistake when you terraform a planet, it is likely that you can't "turn back the clock" and undo your mistakes.

    With Mars, we can't try again with a Mars 2, Mars 3, Mars 4 etc. until we get it right.

    Accidental transformation of Mars

    If we simply land humans on Mars, with no grand intentions to terraform it, as with the private space mission plans such as Mars One, this might well still introduce life to the planet. This would be accidental transformation, with no intent to transform it, indeed most likely, with measures taken to try to prevent it.

     Mars One - Bryan Versteeg
    Artist's impression of Mars One habitat landing on the desert landscape of Mars.

    As with all the current parties with plans to colonize Mars, they intend to comply with all planetary protection regulations. They also have no plans to deliberately attempt to terraform Mars at present. But they could transform the planet accidentally, by their presence on the planet. This could happen through the huge numbers of micro-organisms that always accompany humans, and leaks of atmosphere from the spaceship and spacesuits.

    There are potential habitats on the surface of Mars which could be infected in this way such as the warm seasonal flows, and deliquescing salts. There may also be subsurface aquifers warmed by geological heating and accessible to the surface through caves.

    Water seems to flow freely on Mars
    Locations of Warm Seasonal Flows shown with black stars, some of them in the equatorial regions of Mars. These are believed to be signs of water flowing, due to the temperature range at which they form and location (not to be confused with the dry gulleys, which are a CO2 phenomenon). This is one of the most promising habitats for life on Mars, though there are other possibilities as well. See Water seems to flow freely on Mars (Nature article).

    Experiments by DLR have also suggested that some arctic lichens and cyanobacteria could survive on the surface as is, using the humidity of the night time atmosphere, and protected from UV by specialized chemicals in the plants. For more about all these new ideas for possible habitats on the Martian surface see Might there be Microbes on the Surface of Mars?

    If these habitats exist, life from human settlements would surely spread to them eventually. The spores would get imbedded in cracks in grains of iron rich sand, so protected from UV radiation, and get blown throughout Mars in the dust storms.

    This is Opportunity, and you can see that over a period of about 30 days, from sol 1205 to sol 1235, it got darker and darker and darker until 99% of the sun was cut out by the dust-storm.

    Progression of Mars dust storm over three days, Opportunity Rover
    Dormant microbes imbedded in a grain of dust in this dust storm would be protected from UV light by the iron oxides in the dust, and could spread to anywhere on the surface of Mars in the wind.

    Hubble image showing global dust storm

    At times these dust storms spread to cover the entire planet, as in this Hubble photograph of Mars

    Carl Sagan once calculated that if you introduced a single microbe to a planet, and it reproduced only once a month, then if it was as hospitable as Earth, within ten years you would have the same population of microbes on the surface as you get in a typical Earth soil. Of course Mars is too inhospitable to develop a soil as rich as Earth over that timescale, but it suggests that the process is only limited by availability of the habitats.

    A single microbe introduced to a subsurface aquifer, or surface habitat, could spread throughout that habitat rapidly, quite possibly within a decade, and soon make major changes to the planet. This might for instance lead to large scale release of methane, a greenhouse gas. Following the ideas of Carl Sagan's rough calculation, depending on the availability of the habitat and the rate of reproduction, this could happen as soon as a decade or less after the microbe first got accidentally introduced to the planet.

    Whether biological transformation of a Mars is a fast process like this, or a long slow process, it makes no difference in the long term. Once started, it would be impossible to stop. You can't remove life from a planet, as far as we know, except by heroic measures such as impact by a large body to make the entire surface molten.

    Artist's depiction of the impact of a body the size of the moon impacting a planet the size of Mercury.
    This is an artist's impression of one of the major impacts between Moon sized "planetesimals" in the early solar system - far larger than the normal giant meteorite impact in the present day solar system. These could have made an entire planet surface molten.

    This might be enough to sterilize an entire planet once life gets started there (it is not certain that this would work, since the life could recolonize it by transfer on the numerous meteorites ejected into space and recaptured after the surface cools down again). Short of attempting something drastic like that, any contamination of Mars by microbes, once it begins to reproduce over wide areas, and colonize deep subsurface aquifers, can probably not be reversed.

    Short of something like this, we have no chance of a Mars 2, Mars 3, Mars 4 etc. if our first accidental or deliberate transformation of the planet goes wrong.

    With present technology at least, there seems to be no way to introduce humans to Mars without at least a greatly increased risk of introducing Earth life to the planet. Our spacesuits leak air continuously, airlocks also vent air when used, and in the event of a hard landing, the contents of the lander would contaminate Mars most likely irreversibly. And humans are accompanied by many trillions of micro-organisms which we can't remove or we would die.

    Suitport. Astronaut climbs into the spacsuit through the hatch. It does leak a small amount of air still, about a cubic foot. The spacsuit itself would also leak air constantly, all present day suits do, e.g. through flexible areas such as the joints.
    Spacesuits like this designed for mobility leak air constantly through the joints. So also do airlocks. Even this tiny suit port leaks a cubic foot of air into the Mars atmosphere every time it is used.

    This air would be contaminated with microbes. The skin of a typical human is estimated, to be host to a trillion micro-organisms in about a thousand different species many of which are not well understood, and some with surprising adaptations. This continual leakage from a human habitat greatly increases the risk of contaminating Mars compared with an unmanned rover. A human habitat can't be kept sterilized in the way an unmanned rover can be.

    Inside the body we have a hundred trillion micro-organisms, ten times the number of cells, in ten thousand different species. There are numerous micro-organisms also in our food, the air we breath, and the water we drink.

    In case of a hard landing, there is no way that this life can be guaranteed to remain contained in the spaceship with present day technology.

    Paraterraforming - covering the planet with greenhouses

    This microbial contamination of Mars may be an issue with paraterraforming Mars as well. Paraterraforming means, to cover Mars or part of it, and develop a habitable environment within that covering. For instance, a simple way to do it is to cover the planet, or parts of it, with greenhouses.

    The risk of contamination depends on how this is done, as there are two ways of doing hydroponics, with or without microbes. If you supply the nutrients chemically, and introduce higher organisms only, then it might not be an issue.

    But if you introduce micro-organisms - then though you may only intend to paraterraform, yet, it would be impossible to do that without introducing life to the planet as well. This seems likely to lead to accidental transformation of the planet itself e.g. its subsurface aquifers, if they exist, or surface habitats.

    There is no hurry to get started on terraforming Mars

    In this article I want to highlight some of the things that could go wrong. I'm not saying that we should never terraform Mars. But there is no great hurry to get started on it. On the most optimistic of projections it would take a thousand years, and most think it would take longer than that, perhaps ten thousand or more likely a hundred thousand years. For at least the first few centuries, Mars would remain far more inhospitable than Earth is ever likely to be. It would be no "second home"

    Even immediately after an impact by a (normal sized) giant meteorite on Earth, our home planet would remain far more hospitable than Mars after a century or more of terraforming. The most inhospitable desert on Earth, in Antarctica and the high Atacama desert, would remain more hospitable than Mars.

    Wright valley, from Bull Pass
    This McMurdo dry valley is far colder than it seems, one of the coldest most inhospitable places on Earth. Yet compared with other places in the solar system, it is extremely habitable.

    Mars is not likely to become as hospitable as this even after decades, even centuries of terraforming. You can still breath, you don't need to create your own oxygen, and you are not dependent on a spacesuit to go outside.

    a view of the Earth on September 21, 2005 with the full Antarctic region visible.

    McMurdo valleys from space - they are in the thin area not covered by ice near the top of this photo. These valleys are as cold as the rest of the continent but are kept dry by mountains that hold back the ice, and katabatic winds of up to two hundred miles an hour, cold air from the ice sheets, that sweep down the valleys.

    Mars is also dry, and extremely cold, with equatorial regions similar in average temperatures to the interior of Antarctica but with typical night time temperatures far colder. It looks warmer in the photographs because it is so dry, and the air is so dry because the atmosphere is so thin, so thin that your saliva would boil at blood temperature and you wouldn't last even seconds without a spacesuit. Mars is no second home at present and will surely remain deadly to humans after at least decades, and probably centuries of any attempts at terraforming. It may be possible to paraterraform it at an earlier stage, but it remains far easier to build similar greenhouses on deserts on the Earth than Mars. For more about all this: Mars, Planet Of Surprises, Great To Explore Not So Great To Colonize - 1. Is It As Good A Place To Live As A Desert?

    Humanity can easily afford a few more decades to study Mars first, and decide whether this is what we want to do, and if so, how best to do it.

    In my other articles on this science20 blog, I've talked about the great value of pristine Mars for humanity, and about how it is important to explore Mars thoroughly before we decide what to do next. Also about the possibility of "Marsforming" Mars if it turns out to have interesting indigenous life (Chris McKay's idea). I've also talked about the great benefits of exploring from orbit first, via telepresence, with humans in orbit and machines on the surface working together, each doing what it does best. And I've written about the potential for the materials in the asteroid belt as habitats and potential second homes for humanity, with far greater potential than Mars, enough material for cosmic radiation shielding of a thousand times the surface area of the Earth.

    This article is about more direct issues with terraforming Mars (or indeed, paraterraforming Mars - turning it into a world of greenhouses).

    Some of the things that could go wrong

    Some of the main things that could go wrong with an attempt to terraform Mars are:

    • The simple approach takes far longer than expected. Chris McKay estimates 100,000 years for this simple approach to reach a breathable atmosphere, not 1000 years. Zubrin estimates, it could be accomplished as quickly as 900 years in an optimistic scenario, more complex approach, with mega-engineering such as space mirrors to reflect more sunlight to Mars. Which of these estimates is closest to what would actually happen in practise? Would it work at all?
    • All the CO2 gets turned into limestone or other forms of calcite or similar minerals, and is permanently removed from the atmosphere and is extremely hard to release again
    • It loses its CO2 into space. We don't yet know how early Mars lost its atmosphere, this is what Maven may clarify. However, high energy particles from the sun can strip a planet of its atmosphere, and on Earth these are kept away by its magnetic field, so it might be because of the lack of a magnetic field on present day Mars.
    • It loses water continually from its upper atmosphere due to dissociation into hydrogen and oxygen.
    • The biological cycles are unstable, or go in a direction not suitable for humans e.g. creates a stable atmosphere, but one with high levels of gases poisonous to humans such as H2S or methane, or the planet goes into a deep freeze again with biological cycles reinforcing the deep freeze (e.g. causing clouds that reflect the sunlight away).
    • Some purely biological issue - a micro-organism or higher organism evolves on our transformed Mars which is either hazardous to humans, a disease or an allergen, or damaging to our crops or animals, etc. Or Mars already has such micro-organisms on it.

    Most of these would be potential problems for Mars even if it was an identical twin to Earth geologically. We don't know enough about terraforming to be confident about the outcome of our actions yet for an entire planet. But there are many differences between Mars and Earth which suggest it won't work to try to turn it into an Earth clone. Instead we will need a unique solution tailored to Mars.

    Some differences between Mars and Earth

    There is one remarkable similarity between Mars and Earth. Its day is almost exactly the same as the length of the Earth day. But there are many major differences.

    • Lower gravity - so needs about 3 times as much mass for the same atmospheric pressure, similarly needs three times the mass of oxygen per square meter for a breathable atmosphere,

      This might also cause issues for humans if they live there permanently. We don't know, more research is needed on this. It's known from the ISS that zero g is harmful for health long term, causing a wide range of different medical issues. So far there have been no simulations of Mars or Moon levels of gravity or methods of compensating with artificial gravity (something you can't do on the surface of the Earth but can do in orbit with artificial gravity)
    • More elliptical orbit, so much greater difference of climate of the two hemispheres - cold southern winters, warm northern summers.

      This also currently causes major storms every two years as the dry ice sublimes. The storms are not a hazard at present but may be when the atmosphere is thicker, at least for as long as there are significant amounts of carbon dioxide locked up as dry ice. I don't know if this would cause storms at a later stage in terraforming - the changes are greater than for Earth but the changes are also more gradual - and I don't know of any attempts at detailed modelling of climate on a terraformed Mars.
    • Further from the sun - half the light we get
    • No continental drift, so long term it may lose all its atmosphere - on Earth the atmosphere is maintained long term by volcanic eruptions - which is also probably the main thing that got Earth out of its snowball Earth phases.
    • Starts off as a near vacuum for atmosphere, and average temperatures same as Antarctica
    • Is not known if it has enough CO2 for terraforming. Much of the original atmosphere may have escaped or locked into carbonates.
    • It has much less nitrogen than Earth, which is important in our atmosphere as a buffer (77% of the atmosphere), as well as needed by many plants. A CO2 atmosphere with no buffer is poisonous for humans even when it has enough oxygen to breath. An almost pure oxygen atmosphere (as in spacesuits) is breathable, but hard to achive biologically, is also flammable, and you get oxygen toxicity on long timescales for humans. Some compromise might work, using smaller amounts of nitrogen than for Earth, but this is not certain. These materials might need to be imported from elsewhere in the solar system, involving megaengineering.
    • The Mars surface is rich in percholorates, and poor in chlorides (such as common table salt). Perchlorates are poisonous to humans, and are present in the dust at levels far above the toxicity levels for humans. This could be significant in early stages particularly.
    • No magnetic field to speak of, no protection from solar radiation.
    • No stabilizing Moon - long term the tilt changes are far greater than for the Earth. Mars sometimes tilts so far that it has an equatorial ice belt instead of polar ice caps.
    • Higher risks of giant meteorite impact because it is closer to the asteroid belt. From the cratering record, scientists estimate a five times greater risk of one megaton impacts, likely to happen on the surface every three years, instead of every fifteen on Earth, of course with no atmosphere to cushion the impact.

    Why it might be impossible to terraform Mars a second time - physical issues

    The problem is, that it is not the same planet after a deliberate or accidental terraforming attempt.

    First, it might lose its CO2 in the first attempt. There is at least a fair amount of CO2 on Mars at present, though the amounts are not fully known. If you terraform Mars, and especially if it has seas with shellfish and other micro-organisms that transform CO2 into limestone or other forms of calcite - then these could remove all the CO2 from the atmosphere again. This time though, instead of just CO2 gas, you get forms of rock, far harder to release into the atmosphere again. Simply warming Mars up a second time would no longer work.

    Mars might also lose its CO2 and water to space, through impact of high energy particles from the sun to strip gases from its atmosphere. The water also could dissasociate into hydrogen and oxygen, and the hydrogen get lost to space leaving it with no water.

    Once the CO2 or water vapour is lost to space, then again, warming Mars up again will be of no avail.

    Biological issues with a second terraforming attempt

    A failed attempt now could leave Mars with lifeforms that would resist future attempts at terraforming.

    The simplest way is if we introduce aerobes that remove oxygen, or methanogens that keep the atmosphere methane rich, or other microbes that interfere when we attempt to set up the biological cycles needed to maintain a planet.

    A minor issue, just mentioning for completeness, something that has been mentioned in the scholarly papers as an issue for early stages of an accidental or deliberate introduction of life to Mars, is that micro-organisms could contaminate subsurface aquifers on Mars and make them undrinkable (without purification) - if we are lucky enough that Mars does have drinkable water. E.g. contaminate with biproducts of miocrobial growth.

    It would also leave Mars contaminated with many new species of life. This is especially so after an accidental planetary transformation starting from a human habitat, most of the life on the planet starts as symbionts or pathogens of humans and our crops and other lifeforms we grow in our habitats. These will evolve rapidly on the surface of Mars because of the different conditions there. There are many different micro-habitats on Mars, depending on the amount of light, depth of soil, mixtures of salts, variation of temperatures, and so on, ideal conditions for adaptive radiation. Also high levels of UV and cosmic radiation requiring adaptations to survive.

    So, we seed an entire planet with descendents of human symbionts and pathogens, and Mars is a planet that would lead them to evolve in numerous different directions, and develop resistance to UV, low pressure near vacuum, and ionizing radiation.

    Microbes tend to retain previous adaptations. So, after their adaptations for Mars, many would still probably be capable of infecting humans and human habitats.

    This seems to have some potential, at least, to lead to development of microbes on Mars that are hazardous to us in one way or another including new diseases, allergens and so on, which by then also have added resistance to UV, vacuum, and cosmic radiation. I just suggest this as something worth investigating before you do it.

    In one way or another surely many new species would evolve on Mars during a terraforming attempt. These may not all be desirable for humans. This also would be a permanent change of the planet. If Mars got infected with newly evolved species of micro-organisms hazardous to humans, or in other ways undesirable, it might be hard or impossible to reverse that.

    Paraterraforming done properly - a gentle way to get started on Mars

    Paraterraforming is by far the quickest way to make parts of Mars habitable, if we decide it is a wise thing to do. And - it doesn't have to be humans first paraterraforming.

    If your aim is to have an oxygen atmosphere there as quickly as possible, I think the best way to do it might well be to use automated seed factories, which we can probably make within a few decades as 3D printing technology develops, and get them to travel over the surface of Mars and usng the sand, make the entire surface into green houses (leaving out of course important regions you want to preserve for now, surely there would be "science parks" on Mars).

    You could fill all those greenhouses with shallow ponds a meter or so deep. There is easily enough water on Mars to do that, we know of enough water already to cover the surface to the depth of at least a few meters (it has enough water just in the South pole ice to cover the entire planet to a depth of more than 10 meters if the water thawed out - and more water elsewhere). So then in all those greenhouses, for the first few centuries, all you have growing are cyanobacteria. Make sure there are no aerobes. Also nothing to eat them. Probably do some gene manipulation to make them as efficient as possible at creating oxygen.

    One of the micro-organisms you might introduce early on to help create an oxygen rich atmosphere in a carefully planned terraforming or paraterraforming of Mars. It is UV resistant and has extraordinary resistance to ionizing radiation, is a prime producer (so needs nothing else in order to survive, just raw materials) and might be able to survive on parts of Mars already just as it is. It can produce oxygen so enrich the atmosphere with oxygen.

    This would be most effective on a planet with no aerobes or other micro-organisms to consume the oxygen, compete with the cyanobacteria, or eat them.

    I think that would be the quickest way to get an oxygen atmosphere on Mars through biological means.

    It could be a garden planet - and you could grow larger plants as well, without introducing unwanted micro-organisms. The difference between plants and animals here is that you can introduce a species of plant to Mars as a single seed - with no associated microbes. This is easily sterilized, and techniques have been developed to grow higher plants completely without any use of micro-organisms, by supplying the nutrients they need in chemical form. In this way you could grow trees, and higher plants like fruit, flowers, vegetables, via hydroponics and aeroponics.

    Then export those to the colonists who would remain in orbit around Mars for now. For that matter, you can start on this approach of growing higher plants on Mars before you even introduce the cyanobacteria. This could be done with no risk of accidentally terraforming Mars, right away, if done with great care.

    It would not be without its risks. Due to the high rates of meteorite impact on Mars, once much of the surface is covered in greenhouses, you have to factor in the effect of a one megaton explosion on the surface every three years destroying some of your greenhouses - at least for as long as the atmosphere of the planet itself remains thin and unable to cushion the impacts. You can also expect numerous smaller impacts to destroy parts of the habitats every year. With the thin Mars atmosphere, only the smallest meteorites will burn up in the atmosphere. The latest estimate (2013) is that every year, each square kilometer of the Mars surface has a 1.65 in a million chance of a crater forming of diameter 3.9 meters or more. New impact craters are observed regularly in the satellite photos of Mars.

    Meteorite on Mars found by Opportunity
    This is the first meteorite Opportunity found on Mars (it has since found several more). This one is too small to cause much damage to paraterraformed Mars, but because Mars is so close to the asteroid belt, calculations show that Mars gets hit by a meteorite large enough for a one megaton impact every three years - and it gets hit by numerous smaller impacts. These do not burn up in the thin Martian atmosphere, as they do on Earth.

    New crater forming on Mars
    The new dark spot in the right-hand image is the result of an impact on Mars between the two dates. These are observed frequently. Because of the thin atmosphere, even small meteorites hit the surface frequently, and would damage habitats on a paraterraformed Mars.

    At a certain point, though, you might decide, enough is enough, once there is enough oxygen in the greenhouses to support people. But by then with the technology to create closed ecosystems developed, and mining of asteroids, probably the solar system is filled with trillions of colonists in Stanford torus type habitats made from the asteroid belt. So then, there is no urgency at all to do that.

    Even the first step of paraterraforming is an irreversible long term decision for the planet - once you introduce even cyanobacteria to Mars (unless it has them already and you just use the indigenous versions, which is of course possible we don't know yet) - then there is no way that we know of to reverse that.

    So we need to be totally sure it is what we want to do, need to do it also based on a thorough understanding of what is there already, and understand what it is going to do to the planet long term. Because paraterraforming of course won't just transform the planet inside the habitats which will not be totally micro-organism impervious, they will leave the habitats and colonize the surface too.

    Though we may intend to just introduce a single species, it would be sure to adapt and spread throughout the planet. We would need to be reasonably confident not just about the effect of it on Mars, but also about what it is likely to develop into as a result of adaptive radiation over decades or centuries on a planetary scale.

    Turning back the clock on Mars

    And - I think at least possible that once we have a thorough understanding of what is there on Mars, especially if we find interesting early life - or indeed - suppose we found proto life, evolution not yet started - then it would be amazing to try to return Mars to its original state billions of years ago and so be able to study close up in our own solar system what the Earth was like 4 billion years ago. That might be thought such an amazing opportunity that it's by far the most valuable way of treating Mars.

    Right now it might seem strange to do that rather than send humans there. But when we have loads of space habitats, with it easy to make new ones, and potential for a thousand times the surface area of Mars as space habitats - there is no reason at all to use Mars for colonization at that point.

    Paraterraforming the Moon

    As for first steps in paraterraforming to try out the technology - you can also paraterraform the Moon, I think probably a better place to start. The Moon is so much easier to get to from Earth and easier to supply and return in an emergency. On Mars, if some equipment goes wrong such as your machines for oxygen generation or even just your heaters fail, then you'd die quickly with no chance at all for supply from Earth (cold enough at night for the CO2 to start to freeze out of your habitat).

    On the Moon though, yes it doesn't have so much water, but it does have some considerable amounts of either water or hydrogen rich organics or both at the poles, and also elsewhere, there is enough water to be useful biproducts of mining. It could also be extracted using microwaves. It is hardly explored at all on the surface, so we don't know what is there yet (e.g. does it have ice deposits in the lunar caves as well?? - we know the Moon does have lava tube caves). Then, once we have NEO (Near Earth Object) mining, it will be easy to supply materials to the Moon. It is also of course far easier to supply from Earth.

    The soil on the Moon is also shown to be good for plants. So if you want to make a start on terraforming, I think first explore the Moon which we can do rapidly from Earth, I think once we have a few modern rovers on the Moon then it will be astonishing how quickly we find out more about it, and there may well be very enticing places on the Moon for colonization once we understand it better.

    Early NASA artwork showing lunar greenhouses. Some NASA scientists are getting together a project to send an automated small greenhouse to the Moon in near future with turnips, basil and flower seeds, as a first try out of the idea

    Though of course need to step carefully - for instance rocket exhausts will contaminate the thin lunar atmosphere. Then, if humans go to the icy regions on the Moon, though there is no risk of contaminating with living organisms, there is a risk of contaminating with dead ones, with organics. We probably want to study the icy deposits on the Moon carefully via telerobotics before we send our first humans to them. The Moon is a great first place to explore these issues, see Organic Measurements on the Lunar Surface: Planned and Unplanned Experiments. But all this preliminary exploration and testing could be done really quickly on the Moon since it is so close and easy to explore

    The Moon does have its long nights, but that may not be such a problem for long term colonization as it seems, as you can use artificial lighting for day and night cycles inside the greenhouses, as for the McMurdo greenhouse in Antarctica.

    One idea, perhaps, is to have solar panels all around the equator and at various latitudes, made from lunar materials of course with long range transmission cables joining them together. Habitats at night are powered by the panels on the day side. .(This idea is one I haven't seen anywhere else yet, but it just combines ideas for long range transmission power on Earth using high voltage direct current, such as Desertec's plans to power Europe from the Sahara desert, with ideas for solar power on the Moon.)

    You can also use nuclear power to start with - this is much less of a problem on the Moon than on Earth because there is no ecosystem to be damaged by radioactive waste, and no water to carry the waste around through the surface, so it is easy to contain and clean up. Current plans for colonizing the Moon depend on nuclear power. So, early colonists might use nuclear power during the lunar night. Later on however, solar power with transmission cables from the sunny day side to the night side of the Moon would generate plenty of power..

    Disadvantages of Mars orbit for long term colonization right away

    The main disadvantage of Mars is the resupply issue. It would take two years to resupply astronauts in Mars orbit from Earth, and we don't yet have any experience of running a space settlement without regular supplies from Earth. The ISS depends on frequent resupply from Earth (even supply of clean clothes in the case of the ISS as it has no facilities for astronauts to wash their clothes), and has needed emergency support such as emergency oxygen from Earth occasionally. So, until we learn to truly make self sustained and contained habitats, or until we reduce the time it takes to send supplies to Mars, I think even Mars orbit is likely to be for hardy explorers rather than long term colonists.

    A NASA artist's concept of a vehicle which could provide an artificial-gravity environment of Mars exploration crews. The piloted vehicle rotates around the axis that contains the solar panels. Levels of artificial gravity vary according to the tether length and the rate at which the vehicle spans.
    This is a 1989 design but similar approach could be used nowadays for early expeditions, just join two habitats together with a tether for artificial gravity. Mars however is far away from Earth, and so because of problems of resupply and emergency return, probably best for explorers rather than colonists at present, with use of multiple redundancy to reduce the high risks of a space colony so far from Earth.

    For small expeditions of highly trained adventurers, this may be not so much of an issue. Either they take a big risk (possible with private ventures though not politically acceptable for NASA astronauts), or perhaps you can deal with the issues of resupply from Earth by multiple redundancy.

    For a reasonably "safe" mission to Mars, it might make best sense to send all your supplies at least in triplicate and have three copies of every spaceship. So, before any explorers, or permanent colonists for Mars orbit leave Earth, you make sure there are at least three habitats in orbit around it, each of them large enough for your entire colony to use in an emergency, and of course all stored with enough supplies to last for several years.

    You would also have three functional space ships there (which could be the habitats themselves), each able to return the entire colony to Earth in an emergency "as fast as possible" - that is, within two and a half years of the emergency in case of Mars as return flights are only possible every two years at present and take about half a year.

    Most of the cost is in development, so it is only adding a certain percentage to do three of everything for the first mission there. That is, except for launch costs of course but I expect those to go down massively in the near future. Mars capture orbit is easier to get to than the surface of the Moon in terms of delta v, which helps with the launch costs. For effective exploration of Mars, colonists don't have to be in a low Mars orbit, indeed one of the best choices is a slowly precessing near sun synchronous Molniya orbit - which is similar to a Mars capture orbit, easy to get to, and brings the habitats close to the Mars surface every twelve hours n the day side, so you get to explore the entire planet via close up telepresence from orbit.

    Something like that seems the "safe" way to do it - at least until the time to resupply Mars orbit, or to return in an emergency, is reduced to less than two years.

    These extra habitats in orbit around Mars will also help you to build a large orbital colony around Mars rapidly (also using resources from the Martian moons) as experience and confidence grows.

    Venus One instead of Mars One

    Screenshot from Star Wars of cloud city of Bespin, floating in gas giant. Perhaps it might be easier than you think to make floating cities, in the dense CO2 atmosphere of Venus

    There is also Landis's intriguing possibility of floating cloud cities in the dense Venusian atmosphere, floating at the level where the atmospheric pressure exactly matches that of Earth.

    I'm not sure quite how seriously to take this yet as it doesn't seem to have had any detailed feasibility studies in recent times. The scientific literature on it is tiny, just one recent paper and an old 1971 article in Russian as far as I know. But is an interesting proposal,, which highlights how difficult the surface of Mars is to colonize when you compare Venus and Mars.

    The idea is, that in some ways it would be easier to colonize Venus than Mars. This might sound crazy at first, with its atmosphere so dense, surface so hot - but it turns out that there is a reasonably pleasant layer on Venus in the upper atmosphere. There is no oxygen, and it has sulfuric acid so you have to protect the outside of your habitat from that -, but the pressure is just right which is a major bonus for engineering a habitat.

    What's more because the atmosphere is made of the heavy gas CO2, then lightweight structures filled with normal breathable Earth atmosphere at normal pressures, with its mix of nitrogen and oxygen, would float in the Venusian atmosphere in the same way that helium or hydrogen balloons float on Earth. You could use hydrogen as a lifting gase, of course, and would be a much stronger lifting gas than on Earth, but it is not necessary.

    The habitat would be in equilibrium with the atmosphere outside of it, at the same pressure. Just fill with an Earth normal mix of oxygen and nitrogen and it would naturally float at about the right level to maintain an Earth normal atmospheric pressure inside (just as a weather balloon full of helium naturally floats at a high level in our atmosphere). If the city is heavy you could add extra helium or hydorgen chambers for extra lifting power., which would have much more lifting power on Venus than here.

    Also unlike Mars, the Venusian atmosphere does have nitrogen in it, 3.5%. It also ahs water at 20 ppm. But better, it has sulfuric acid droplets in the clouds, and you can make water from H2SO4.

    The atmosphere is also thick enough to give adequate cosmic radiation shielding even at cloud top levels, the level of shielding is similar to that for Earth. It would also protect from the smaller meteorites, up to the megaton level, as for Earth. And it has 90% of Earth normal gravity as well, no need for spinning habitats to give a sensation of Earth normal gravity (if that is needed).

    As Landis said, in his Colonization of Venus.

    "However, viewed in a different way, the problem with Venus is merely that the ground level is too far below the one atmosphere level. At cloud-top level, Venus is the paradise planet."

    Or as he says in his talk to the Mars society about Venus,

    "If you define sea level as the level at which the atmospheric density is the same as the Earth sea level density, the problem with Venus is not that it is too hot on the surface, the problem is that the surface is too far below sea level. "

    Temperatures at the cloud top levels are in the habitable range of 0 to 50 C. The habitats would float naturally at the right level so long as you keep the levels of oxygen and nitrogen inside the habitat at Earth normal levels - just as a hydrogen ballon naturally floats at a high level in the Earth's atmosphere. Then at the cloud top levels, the air moves around the planet with a period of about 4 days, a phenomenon known as super-rotation, giving a much shorter day length than the planetary surface.

    This "Floating habitats in the Venus Atmosphere " idea is one of those ideas that seems completely crazy to start with, but the more you think about it, the more sense it makes.

    Russian idea for Venus cloud colony
    Russian idea for a Venus cloud colony in 1971 - original article (in Russian) - and discussion.

    As for resource utilization, Landis describes various methods for getting materials from the surface. But perhaps you don't need so much of that. Another idea which he doesn't mention in the paper is that trees and other plants would grow well in the CO2 air and abundant sunlight, and take in the gases and convert them to organics.

    It would probably start small. something like a Bigelow type inflatable habitat to start with, but doesn't need to be as robust as the ones for space, don't need to hold in ten tons per square meter of atmospheric pressure. That would get you started with a tiny settlement.

    Once it gets started you can do ISRU from Venus itself. Nitrogen and oxygen from the air. Water from the sulfuric acid in the clouds. Inside you can grow trees and plants and make plastic. Ther plants would grow well in the CO2 air and abundant sunlight, and take in the gases and convert them to organics.

    You might be surprised at how much of the mass of a tree comes from the atmosphere (including water vapour which in case of Venus would be extracted from the sulfuric acid in the atmosphere), and how much from the ground. Try to guess before you watch this video by Richard Feynmann - the famous nobel laureate physicist.

    See this article also, Trees Come 'From Out Of The Air,' Said Nobel Laureate Richard Feynman. Really?

    So in that way you could build new habitats in the Venusian atmosphere largely out of timber and plant based plastics. It could be quite "low tech". You can also get more specialist things from the surface too - a challenge but Landis thinks it can be done. It might not need that much by way of imports from the rest of the solar system.

    I tried listing some of the advantages of Venus atmosphere colonies, and its surprising how many there are:

    • 100% radiation shielding at the destination - same level as Earth
    • Slightly shorter journey times (under 6 months instead of over) and can travel there slightly more frequently (less than two years instead of more than two years between opportuities)
    • No need to compress the air
    • Can make fuel for return journey from the CO2 just as for Mars, from hydrogen feedstock - but with the CO2, at Earth normal pressure
    • No need for landing strip or launch platform. Planes and rockets float in the air anyway on arrival. On launch, may need to suspend it from a hydrogen balloon for lifting to offset the weight of the fuel before you start the motor, but again - does seem simpler than launch from solid surface, just as for air launches of spaceships from Earth.
    • Rockets and spaceplanes and spent rocket stages would all float in the Venus atmosphere so long as you keep them fairly air tight and make sure there is some spent fuel or atmosphere inside to supply the pressure against the Venus atmosphere.
    • Resource utilization - grow plants at Earth normal atmospheric pressure, would take up most of the mass from the atmosphere
    • No risk of habitat depressurizing
    • Can use reasonably normal straightforward engineering construction methods for the habs just as for Earth. Don't need to build to contain many tons of outwards pressure per square meter - which we only have experience of doing for the ISS, and other space stations.
    • Abundant solar energy because closer to the sun.

    Of course lots of things to address, as for Mars. You don't have the problems of the cold or thin atmosphere, and there is no risk of your habitat depressurizing. But you do have plenty of other problems.

    As with Mars, the easiest thing to do is a one way trip to Venus, for permanent settlers. I got the title for this section from this fun discussion of the topic at the Planetary Society. Why Venus One might be better than Mars One. For Geoffrey Landis's technical paper on his idea, see Colonization of Venus. See also the Wikipedia entry on colonization of Venus: Aerostat habitats and floating cities. Also two videos by Geoffery Landis on the subject to the Mars society: part 1 and part 2.

    Of course, as a new idea, nowhere near as much work and thought has gone into Venus colonization as has gone into Mars colonization, and there is much to be worked out. If this intrigues you, try the enthusiastic Venus Society page at Linkedn. started by Dave Kidd. Also Jon Goff has many recent posts on the Selenian Boondocks blog with interesting ideas such as his Venusian Rocky Floaties - that spent rocket stages would float in the Venus atmosphere, would not hit the surface, so long as you seal them and vent a bit of the remaining fuel to keep them bouyant, making it easy to capture them and re-use them to return to Earth.

    I would certainly not say at this stage that its been shown it can be done. It needs feasibility studies and proper peer reviewed papers and all that sort of thing. It has nothing like the number of studies and papers there are for Mars colonization. For now, it is simply an intriguing idea that might easily turn out to have flaws in it and not work.

    Planetary protection issues for Venus

    Though it is far less problematical than Mars, there may also be planetary protection contamination issues to consider as for Mars, because some think it is possible that there may be life already in the Venusian atmosphere. It seems not impossible

    • Venus may well have been habitable in the early solar system when it is thought it had a less dense atmosphere and may well have had oceans
    • The residence time for dust in the Venus atmosphere is months instead of days
    • There have been intriguing measurements that suggest there are particles there that are just the right size for life, and non spherical
    • There is also evidence of OCS (Carbonyl Sulfide) which on Earth would be an unambiguous indicator of life. See Could life exist in the Venus Atmosphere.

    If there is life in the Venus atmosphere, then we certainly want to study it first before we risk contaminating it with Earth life. It might be indigenous and give us clues to the early Venus, and whether life evolved there independently from Earth or was in some way related.

    It is likely to be exremely interesting if there is life there. It is hard to see how life on Venus could be seeded by meteorites from Earth in its present form, because the surface is so hot and dry. That is - unless they break up as dust in the upper atmosphere perhaps?. If there is any life in the clouds it seems likely that it's been there for billions of years and may have evolved into a complex ecosystem of micro-organisms - if so that may be fascinating for biology, and understanding evolution, origins of life, stages of life prior to modern life etc.

    As for Mars shouldn't send humans anywhere near a system like that until we know well what is there and what the impact on it would be.

    But if there is no life, or after studying it, then the issues are far less than for Mars. The surface probably can't be contaminated with Earth life at all, is too hot, and too dry. There is no worry about losing the atmosphere as a result of introducing life, and is hard to think of anything life could do to Venus that would make much difference, and if it did, would probably improve it as a place for humans to live in. The only concern is about life spreading to the cloud tops layer of Venus, would need to think a bit about what effect that would have but seems unlikely on the face of it to be likely to cause any isssues apart of course for the matter of possibly competing with indigenous life if present.

    Far future idea to terraform Mars and Venus in one go

    As for terraforming, then Venus is likely to be hard to terraform, for the opposite resaon to Mars, because it is extremely hard to get rid of the atmosphere. It has so much CO2 that even if you could somehow project all of it into space, it remains within the gravitational influence of Venus, and the planet would just gather it all up again and be back again where you started.

    It could be possible but might involve e.g. ejecting the Venusian atmosphere as dry ice pellets at high velocity - you can even imagine in the future a mega-engineering project which first cools down the atmosphere of Venus using giant reflective sunshades, until it freezes out. Then you fire the atmosphere of Venus to Mars, using a railgun or similar, as a stream of dry ice pellets enclosed in reflective wrappers to protect them from the suns heat, thus making both planets habitable in a single project. But that is a far future idea, and verging on science fiction, at least at present.

    Of course this is something that is way beyond our levels of understanding or wisdom to do right now. Maybe our descendents might think about it a few thousand or even millions of years into the future though....

    What about the Science Fiction stories about terraforming Mars

    You might ask, why are hardly any of these issues with terraforming Mars mentioned in the science fiction stories? Why is it so much easier in the stories, such as the Mars Trilogy?

    Science Fiction authors stimulate the imagination, undoubtedly, and may even foreshadow technological developments before they happen. Their work is a mix of things astonishingly far sighted like the early stories about television long before it was invented, and things that are a product of their time such as Asimov's early stories about Multivac, a supercomputer made of vacuum tubes, with only one computer in the world.

    There are "hard science fiction" early stories with explorers using slide rules in spaceships that travel faster than light. (Full text of the book, "Islands in Space" by John Campbell). Many of the early movies and TV programs have futuristic spaceships with the pilots staring at green monochrome displays on bulky cathode ray type monitors. Many stories by hard sci. fi. writers such as Arthur C. Clarke in one of his best early short stories, "predicted" a lunar surface covered with fine dust so deep that rovers could sink into it without trace, and of course all the early stories had oceans on Venus and Mercury with one face permanently facing the sun. There are many such examples.

    With all the different stories that get published, some may get it right. For instance none of the "big name" sci. fi. authors wrote about a televised landing on the Moon before it happened - they thought that the signals would be blocked by the Heaviside layer. But one minor science fiction author did "predict" this in his short story in 1947.

    Front cover of Amazing Science Fiction Stories, Volume 21 Number 4, April of 1947
    Amazing Science Fiction Stories, Volume 21 Number 4, April of 1947. This little known story "All Aboard for the Moon" by Harold Sherman is notable because it describes astronauts who (crash) landed on the Moon while in direct communication with Earth and the Earth news media via television. Later stories even by the "giants of science fiction" didn't predict a televised Moon landing, because the authors were under the impression the signals would be blocked by the Heaviside layer.

    Similarly, our science fiction stories about Mars may leave out fundamental ideas that are significant, and which we don't know about, or which at least, the science fiction writers don't know about. In the case of the Moon, there was a secret 1950s military experiment, involving bouncing radio signals off the Moon for communication, but presumably this was not widely known by the science fiction authors.

    In the case of Mars there are many detailed issues about the terraforming of the planet that are known by a few academics, in published papers, but are not addressed in popular stories or articles on the topic. And as for the early sci fi, doubtless there are other issues and future developments that no-one at present either knows about or can predict.

    So science fiction may be inspiring, and often far-seeing, and sometimes gets things right but they are a product of their times. Even the best "hard sci fi" should never be mistake for accurate prediction of the future.

    There are also a few science fiction stories about terraforming gone wrong. See for instance "Oh my God, Mars smells like shit" ~ Geoffrey Landis talks about his vision of Mars at 2008 conference

    So, what about a "Second home" for humanity, where does this leave that idea?

    For creating new habitats - well you have all the materials for life in the asteroids. You can create habitats with enough cosmic radiation shielding for land area a thousand times that of the Earth in space habitats, using materials from the asteroid belt - a calculation that goes back to the time of the studies by O'Niel in the 1970s.

    Certainly if you have the technology to successfully terraform a planet, you must have the technology to make hundreds of thousands of Stanford toruses or similar in space, all self contained and able to sustain life independently of Earth. If you can't do that, surely you are nowhere near being able to terraform a planet successfully.

    NASA artwork from the 1970s for the Stanford Torus design
    Stanford Torus Interior (NASA), population 10,000, NASA space colony art from the 1970s
    This was something we could build already with 1970s technology. The idea was to use it to make solar power satellites to beam energy back to Earth (as microwaves). It was projected to cost about 20 times the cost of Apollo and eventually pay itself back over decades
    Such projects are likely to be easier to do as time progresses. Once we have many habitats like this then we may begin to have enough experience to know whether we could terraform Mars, and how to do it. But by then, with habitats potentially with land area of a thousand times that of Earth we may see no need for Mars for colonization and may instead prefer to leave it pristine or turn the clock back to early Mars, or Marsform it to make it habitable for any indigenous Mars life.

    And if we can't build these kinds of habitats successfully, surely we are nowhere near the level of understanding needed to successfully terraform a planet.

    This is especially true for a planet as different from Earth as Mars. However, I think any planet is surely harder to make habitable for life, if not already inhabited, than a small self contained settlement of a few square kilometers, where in the worst case, if you make a serious mistake, you can start again .

    Before we attempt to terrafrom Mars, let's start with smaller habitats, and learn from our mistakes. Before we attempt to paraterraform Mars, let's try something less ambitious, closer to home, such as setting up habitats on the peaks of eternal light on the Moon, and eventually, paraterraform the Moon using solar power for night time energy.

    This may be the best place on the Moon for your very first colony, before you sort out the power issues and so on, is this place. This is one of the "Peaks of Eternal sunlight".

    For more about this, see If Mars Is For Hardy Explorers Only, Where Is The Best Place In The Solar System For First Time Colonists?

    Before we send any humans to the Mars surface, let's send explorers to Mars orbit first, far cheaper -, and explore the surface via telerobotics. Humans on the surface don't even have any advantages over robots controlled from orbit, indeed a human in spacesuit with gloves would be far more clumsy than a telerobot, and the surface of Mars is in many ways more inhospitable than an orbital settlement. With humans in orbit around Mars, able to drive rovers in real time via telepresence (e.g. drive Curiosity to the base of Mount Sharp in a day rather than a year), and conduct experiments on the surface in real time, we could find as much about the planet in a few years as would take thousands of years of rovers operated from Earth.

    Artists impression of telerobotic exploration of Mars, created for the NASA organized 2012 Telerobotics Symposium:

    You see the astronauts operating telerobots on the surface in a conventional way, operating them from a desk. They could also explore via telepresence using compact omnidirectional platforms. For many ideas of ways to explore Mars telerobotically, see Telerobotic Avatars On Mars With Super-Powers ("Teleporting" from orbit) - Search For Life - And Long Term Exploitation

    In this way we find a lot about Mars at low cost. It is an affordable program - those who plan to explore the surface of Mars could probably do the same expeditions in orbit for a fraction of the cost, and with far more science return. It would probably cost at least an order of magnitude less to explore Mars in this way.

    This is also the only way humans can explore Mars from close up, and still keep Mars free of contamination. It leaves all our options open for future terraforming, marsforming, paraterraforming, or maintaining a pristine Mars.

    We can decide what to do next after that. after however long it takes to get a reasonably thorough understanding of Mars.

    Responsibility for future Martians

    I am not saying that it is impossible to terraform Mars. It is surely a huge challenge though. If we attempted it right now, surely our terraformed planet would soon lose its atmosphere again, at least on geological timescales.

    In time we may perhaps learn to engineer the cycles needed to keep Mars habitable long term. We may find a way to return the CO2 to the atmosphere, compensating for the lack of continental drift and find a Martian alternative to the Earth system of active volcanoes to maintain the atmospheric pressure. For a start on this, see Dan Popoviciu's "Some Ideas Regarding the Biological Colonization of The Planet Mars", where he describes ideas for biological return of carbon dioxide to the atmosphere.

    We may find a way to set up cycles that work fine on a planet with a highly elliptical orbit and major differences in temperature between the two hemisphere of the planet.

    We may find a way to set up cycles that keep Mars habitable during times of extreme axial tilt, when it tilts so far that it develops equatorial ice belts instead of polar ice sheets, and when its axis is near vertical, which normally leads to ice caps far more extensive than today.

    Changes of tilt of Mars axis and effect on climate (NASA) - current Mars is top left - a permanent terraforming would need to keep Mars habitable through these changes.

    Especially it would need to provide a mechanism for Mars to avoid, or escape from "Snowball Mars" - even present day Mars would be completely ice covered if the atmosphere wasn't so thin and dry that water ice sublimes to water vapour at below 0C over most of the planet.

    Earth is thought to escape from "Snowball Earth" mainly through release of CO2 from volcanoes. This mechanism is not available on Mars, which never developed an active system of plate tectonics and recycling of surface materials through volcanoes, so another method would be needed

    We may find a way to make sure that it does not lose its atmosphere or water to space long term without a magnetic field.

    We may also find a way to deal with biological issues, introduce life in a careful sequence, and make sure that no major biological issues or diseases develop in the planet. We may be able to ensure that the atmosphere does not fall into some state hostile to humans such as a methane or hydrogen sulfide rich atmosphere.

    This doesn't seem totally impossible. Future science and our experiences of attempts to build larger and larger space settlements, combined with our studies of exoplanets (planets around other stars), and perhaps the development of ever faster supercomputers for planetary simulations, may over the decades or centuries give us all the knowledge we need. But I think, we certainly have nowhere near the wisdom, knowledge, and experience needed to make irreversible decisions about Mars quite yet.

    Until then, as Chris McKay has said often (youtube video), everything we do on Mars should be reversible, at least on the planetary scale. We should not alter the planet irreversibly, even accidentally, until we know what we are doing. And as far as I can see, the only way to do that is to keep humans and Earth life away from the planet surface, at least until we know more about what is there.

    What do you think about all this?

    Here I am of course expressing my own opinions on the subject. But there are plenty by way of optimistic news articles and projections suggesting that we don't need any foresight to terraform Mars, just land humans and start growing plants and it will happen almost by itself in a natural way, so is not hard to find the material on this. I have yet to see a single news story suggesting that it might not be as simple as that, though there are scholarly articles on the subject.

    I hope this article helps give potential Mars colonists some pause for thought. Is this indeed true? Might it be wise to study Mars for a few decades from orbit around the planet first before making such a decision.

    This article mainly raises questions and suggests possible things that could go wrong on Mars. What do you think?

    To find out more about all these topics, see my other articles on Mars here on my robertinventor blog


    The simplest problem that can't be overcome is the gravity. It has the atmospheric pressure that it has because of gravity. If you increase the pressure and temperature, the gases increase in energy to escape velocity. So any attempt at in atmosphere will fail.

    That's a good point. Yes, lower gravity means it is easier for the atoms to escape. Especially, light atoms like hydrogen will escape very easily. 
    It is something Maven is hoping to find the answer to, to get detailed figures by measuring the rate at which gases are currently escaping from the Martian atmosphere. 

    Its complex, so can't be sorted out just by modeling it, you have escape of both neutral and ionized gas, and the ionosphere is continually changing in shape and composition on timescales of a few minutes. Mars Express was able to estimate the escape rate for ions, in a preliminary way, and for that, "This process is dominated by hydrogen and oxygen ions (i.e. water), whereas the escape rate of carbon dioxide (CO2) is extremely slow, even though it is by far the most common gas in the martian atmosphere." That doesn't say anything about neutral atoms though.

    For better information about all this, we have to see what Maven finds when it starts to study the Mars atmosphere next year.

    There is good evidence that Mars did have a reasonably thick atmosphere early on, about 4 billion years ago, thick enough for global oceans. Then a second time, about 3 billion years ago, it had another ocean briefly. 

    However, they are pretty sure that early Mars had a strong magnetic field, which kept the solar ionizing radiation away from its atmosphere. We know that, because there are patches of rock on the surface of Mars that still remain strongly magnetized by it's original magnetic field, and have been detected from space. Also from evidence from the Martian meteorites that have landed on Earth. The ionizing radiation from the sun was also much stronger in the early solar system so the rate at which it lost its atmosphere, after it lost its magnetic field, would probably be faster than today.

    You can see the strongly magnetized regions on the surface in this artist's impression. But that's all that's left of Mars's original strong magnetic field.

    (See Earth and Mars Magnetic Fields Compared)

    With the heavier gas CO2 then it could also have got lost to space, or it turned to carbonate rocks, as well as of course just freezing out as dry ice into the ground. Large amounts of dry ice have been detected, frozen deep in the ground, but not yet enough to explain the atmosphere loss.
    So anyway, this is all work in progress I gather and nobody knows the answers yet.


    Extensive and well written article, but you face-planted on the title! How about: "Terraforming Mars: Real Tough... But Not Impossible!" I initially dismissed your article because of it! But... then I took the time to read it through and saw that you covered a lot of useful ground. Other are likely to feel the same way I did at first... and not give you a second chance!


    Oh right, thanks, I'll give it some thought. I've been getting average time on this page recently of under a minute as compared with average time of several minutes for most of my articles - so wondered what was happening. Maybe many have reacted like you do to the title.
    The title is so important I find. Not sure what to do right now, how to change it, it needs to be short, but also clear and to the point and catch the eye. But I think you are right need to do something about this. Thanks!
    For now I've called it "Trouble With Terraforming Mars" as that's what it is called in the linked page from and presumably they have the Journalist's eye for a good title :). And is an open title.
    I can try different titles and see what works best - get a good first idea by the average time on page but need to leave each one up long enough to get at least a few hundred views. I notice that on popular news sites often the title of a story changes as the day progresses so obviously this is something that Journalists pay a lot of attention to and tweak and change, and as you say- it makes a difference to how the article is read, what the reader's expectations are before they start from the title.

    I could try your suggested title too for a bit, or something like it anyway, after this one :). See how it goes.
    I've also added a new introductory paragraph, third para. just to make it clear to the reader some idea of where this article is headed from the outset.

    Okay, that change of title to "Trouble with Terraforming Mars" plus extra short intro para. has nearly doubled average time on page from 44 seconds to 1 min and 19 seconds. That's for over 200 visitors so far with the new title. So clear improvement I think, that probably quite a few were put off as you nearly were before they read far enough to find out what the article was really about.

    Mars will be terraformed by commercial interests as soon as technology allows somebody to do it profitably. All that is really required is for there to be enough Martians for Mars to have a viable economy. Once profits can be made on Mars money can be transfete back and forth between Mars and Earth and then it will be Katie bar the door! Don't expect a lot rational planning to go into the effort.

    Ah, the thing is first, that it is so far away is unlikely that it will be of much commercial interest anyway. 
    Also, terraforming Mars is certainly not a commercial thing to do at present, at least, not if you do it for the sake of the results of the terraforming, because the planet would change only slowly, if it is successful. Imagine trying to get investors for a project that will show no returns for several centuries, as in achieving the thing you paid for, and most likely for millennia. If anyone did attempt it, they would soon give up once they realise how long it will take.
    The "low hanging fruit" for commercial companies are space tourism, orbital hotels, retirement homes on the Moon, and space mining. Things close to Earth because you can do things more quickly and get a return more quickly - and because you can send tourists there for short visits, impossible for the Moon, and far safer also.

    Longer term too, we have plenty of resources on the Moon and in NEOs. For example, Nereus, just 300 meters in length has a weight of, I make it, about 38 million metric tons. In terms of delta v is easier to get to than the Moon when it does its close passes of Earth. Doesn't seem likely we will need to go as far afield as Mars in the near future to get materials. 

    You could exploit Mars commercially in one way. Someone sketched out a plan a few years ago for a business to mine Deimos and sell its water, if it has it, to Earth for use in Earth orbit and rocket fuels, and thought it might be viable - see The Deimos Water Company. That might work because you could use some of the ice as rocket fuel to propel the rest of the ice back to Earth, and Deimos is already in orbit so much less to do to get it back to Earth. Indeed later on once you have a growing orbital colony around Mars, that could be one way it could help pay for itself.
    But for the Mars surface, seems a bit unlikely in near future.

    In more distant future, you could do it. But again no reason to send humans to the surface. Because humans are so clumsy in spacesuits, and it costs much less to send them to Mars orbit than to the surface, and because capabilities for telerobots are rapidly developing, a commercial operation to extract minerals or anything else from Mars, motivated just by minimizing costs, would find it makes more sense to keep the humans in orbit.

    But the other point is, the legal situation. Not only nations are bound by the Outer Space Treaty. Private individuals are too. First, you need a launch site, and the country that provides the launch site has to abide by the OST. They will ask you to say what your plans are and if you say your plans are to colonize the surface of Mars or send humans there, they will require you to show how you will keep it free of contamination by Earth microbes, as required under the OST.

    Then it is no solution to try to launch from sea or from some non signatory nation such as N. Korea (very few nations that haven't signed the OST, and I believe N. Korea is the only one with any space ambitions) because apparently the legal situation is that your country of citizenship is still responsible for upholding the OST and will need to oversee your operations. You would need to resign your citizenship e.g. to the US, and become a citizen of one of the few non signatories of the treaty. Seems unlikely many would want to do that, for such a reason.

    Then we have precedent as well. There are resources in Antarctica of commercial value. They are hard to extract of course, but could pay for themselves. But the Antarctic treaty still holds and all the countries involved keep to it. 

    Antarctica is far easier to get to than Mars. If some company wanted to start doing commercial operations and didn't care what damage they did to the environment, more likely to attempt Antarctica than Mars. But nobody has done that yet, and seems unlikely they will do as long as the treaty holds.

    The OST is a really huge thing for any country or individual to choose to go against. It is the only space treaty almost universally agreed, and the treaty which keeps peace between nations world wide in space. I can't see anyone withdrawing from it, just to do some expedition that is of no immediate commercial value. There was a good program about this recently on the space show, see the space attourney Michael Lister's "Legal review for the year 2013", is an interesting show to listen to if you want to be clear about the legal status of missions to Mars, and other locations in the solar system.

    If you could get enough people on Mars so that they started making things and buying and selling among themselves then you have the beging of an economy. Then you need a bank. Once you have a bank money, profits and investments, can be traded back and forth electronically between Mars and Earth. How many people? Probably less than 100,000. Give it a lot of technology and 200 years. Still, the basic problem is keeping an atmospher due to Mars low mass.


    Yes, I can see that happening. If we do eventually learn how to terraform Mars, or learn enough to decide it is wise to attempt paraterraforming, that might well happen. It could also happen with the orbital colonies too. If we keep sending habitats to Mars orbit, and also build more habitats from materials from Deimos again could have your 100,000 colonists in orbit in your 200 years - that's extra habitats for 5000 colonists a year. Especially as lift costs come down for Earth. 

    We have about a billion commercial passenger flights a year on Earth, so as costs come down, once it becomes as easy to fly into space as to fly to another continent with the likes of skylon etc, it won't be hard to send 5000 colonists a year to Mars orbit, together with the materials they need, if we decide that is what we want to do.

    Long term, there is enough by way of materials in Deimos to provide cosmic radiation shielding for Stanford Torus type habitats with a ground area of 100,000 square kilometers of living area. roughly the size of Iceland, and about twice the size of Switzerland - and in terms of US states, about the same area as Oregon or Colerado. If you had it with same population density as Oregon, that's habs for about 50 million people.

    Then via the "Interplanetary Transport Network" you can, if you have a long enough timeframe, send materials from almost anywhere in the solar system to almost anywhere else by a series of gravitational slingshots with almost no delta v. More about this in my Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths

    One intriguing idea also for the future, you could export materials from Mars surface to orbit,and eventually to Earth or the space colonies, using orbital airships. These are airships that travel faster and faster until eventually they reach escape velocity. There are issues with it such as that the airships will eventually go faster than the speed of sound, but JP Aerospace think they can solve these problems.

    JP Aerospace's Orbital Airship. An airship can't fly straight to orbit because if strong enough to survive the winds at low altitudes, it would be too heavy to fly to orbit. But if you put a floating staging post at about 30 to 43 kilometers above the ground, you can then have airships designed to fly in the upper atmosphere that could float at higher levels and simply accelerate slowly,  until they reach orbital velocity. Passengers fly up to the orbital platform in conventional airships, then transfer to the orbital ships.  These are in between a spaceship and an airship in design, and would be the largest vessels ever constructed, 2 km long (compared with 380 meters for the largest current supertankers). However, they can be amazingly light and don't need much strength, because they don't need to withstand strong winds or indeed much air at all. They would remain permanently at high altitudes.

    On Earth you need two stages, to go to a high floating platform in normal airships - and then use much lighter airships, too fragile for the surface but easily able to cope with the near vacuum conditions, which then slowly accelerate (e.g. using ion thrusters or whatever) until they reach orbital velocity. The higher altitude airships could be made of hydrogen, though I think JP Aerospace plan to use helium - hydrogen is actually used for airships by flying enthusiasts in Europe and can be as safe as Helium if well designed, with a Faraday cage type covering to deal with lightning hazard. It's called "Gas ballooning" - if you search for "hydrogen balloon" you get lots of pages about the Hindenberg disaster, but if you search for "Gas ballooning" you can find out about modern hydrogen balloons. Wikipedia article on Gas balooons.

    On Mars you wouldn't need to have a two stage process, as on Earth. and due to the CO2 atmosphere, then firstly, hydrogen airships would not be a fire hazard at all, and secondly, in a CO2 atmosphere, the lifting effect of hydrogen would be much more so the ships could be smaller. 

    I talk about this some more in my Telerobotic Avatars On Mars With Super-Powers ("Teleporting" from orbit) - Search For Life - And Long Term Exploitation

    This export of materials from Mars  can of course all be done via telerobotics with no need to send humans to the surface of Mars. Once it becomes really easy to export from Mars to orbit, then it might make a lot of sense to grow higher plants on Mars using hydroponics. Again this is something that doesn't have planetary protection issues if you use the version of hydroponics that does not need microbes - and export those to colonists elsewhere. This also could be part of the economy of the colonists in orbit around Mars.

    Have just added a new section about Venus, as quite possibly far easier to colonize than Mars.
    Includes link to this 1971 Russian idea for habitats in the Venus atmosphere (original paper in Russian, and discussion), and to the Venus Society pages on Linkedn, and Geoffrey Landis's original paper. Also here is his video talk about it on youtube

    And part 2

    Plus mentioned the far future idea to terraform Venus and Mars in one go by freezing out the Venus atmosphere (with sunshades) then firing it as dry ice pellets to Mars using e.g. electromagnetic railguns.
    Sunshades would be overkill if your intent was to fire Venusian dry ice pellets at Mars. Just a small gas pump and a stirling heat pump at the back of each railgun could provide the pellets without mega-scale engineering required for a sunshade.

    Let's start by terra forming our home - planet earth. There's a lot to do - let's start with reversing Fukushima effects. We can then move on to less pressing issues like removing rocket fuel contamination from the Colorado river. And there is more to do - not hard to find issues that need attention.

    Yes, that's one thing I didn't quite agree with in Geoffrey Landis's talk - though he made lots of excellent points, it is just one minor detail. and quite possibly he may have changed  his views since the talk anyway, was a few years ago.
    It's when he says, that we can use other planets to experiment with terraforming to find solutions to problems on Earth. The reason being, that if our experiments go wrong we can't try again with a new planet. 

    I think the place we can experiment is in space habitats. For planets, better to just study them and understand how their cycles work as is, which may help us understand how Earth works. Anyway they are too different from Earth for attempts at terraforming to tell us too much about the best things to do on Earth or about how the Earth climates work, at least not in any direct way.

    As for Earth yes lots of pressing things to do. I think myself though that e.g. the Apollo mission to the Moon, expensive as it was, yet gave far more to the Earth than it cost, by inspiration, new ideas etc and probably a lot more than many other high cost undertakings. 

    So, to go all out to spend hundreds of billions to try to solve Earth's problems by establishing colonies outside of Earth - it is just too hard to be sure of the payback. Back in the 1970s they estimated that the Stanford Torus would pay for itself with cheap electricity, and if they were right we might have cheap world wide almost free energy from space as a result of expenditure ten times that of Apollo by the US in the 1970s which they could have found, and our world would be a very different place, we might not even have a global warming crisis.

    But it is hard to be sure about such projections and whether their ideas are valid. Still I think is worth continuing to explore such ideas, it is just a question of whether we should go all out for them as "The solution" then I wonder, but as a reasonable part of continuing space development, I think there is so much potential in space mining, settlements in space, and energy from space plus all the innovation and developments of understanding. Also in case of Mars, and possibly also finding e.g. ancient evidence of Earth life in lunar meteorites and so on, possibility of learning new things about biology, origins of life, things that are alive but intermediate between inorganic processes and the smallest cells we know - those things could be of incalculable benefit to humanity. 

    As for terraforming type activities on Earth, one nice idea is the seawater greenhouse, this is an ingenious way to make habitats in deserts, using seawater for cooling, and then also water is created by evaporation of the seawater, so you get clean water as well, in deserts close to the sea (of which there are many.

    Here is a picture of the Sahara Forestation Project (artist's impression) - a form of "terraforming" of Earth by reversing desertification directly using habitats, similar to ideas for terraforming Mars but much easier and more effective, and could do much more for same cost because of course a desert on Earth is already far more habitable than Mars would be after several centuries of terraforming so you have a huge head start. 

    This is the seawater greenhouse.

    More about it in If Mars Is For Hardy Explorers Only, Where Is The Best Place In The Solar System For First Time Colonists?

    What about using Maxwell Montes, the tallest mountain on Venus, as a base station?

    Yes is a bit better than Venus's average surface 462 °C; 863 °F and 92 atm., from Wikipedia
    Due to its elevation it is the coolest (about 380 °C or 716 °F) and least pressurised (about 45 bar or 44 atm) location on the surface of Venus 
    Hi Robert, great article!
    Did you see this 5 minute story on Adelaide's SeaWater Greenhouse? Supermarkets have evaluated the commercial prototype, and 4 hectares of SeaWater Greenhouse have now gone into production!

    There's an Israeli version that also focusses on creating *more* freshwater than is needed in the greenhouse to grow trees outside and cool the region. I'd love to see a model that combined all this with a biochar scheme, to both create a (little) syngas energy to backup the solar powered greenhouses but most importantly to suck CO2 out of our air and into our soil! Now, while the sci-fi geek kid in me LOVED the Mars Trilogy, how can be be sure we can afford to Terraform Mars when we can't even run a few biochar schemes or grow enough trees in our deserts to solve our own global warming problem? It's 'only' getting CO2 from 400ppm back under 350 or even 300ppm, and we can't agree on who's going to pay to do that! So I'm with you: first get a Moon base and asteroid field O'neil Halo's going, and once a few Halo's are beaming all the solar power we need down to the Earth, THEN we can think about Mars.

    But if we can't afford the Halo's, then we're just going to have to invest in GenIV, waste eating Integral Fast Reactor nukes to prevent climate catastrophe!

    Hi Eclipse Now, good to hear you liked it, thanks!

    No I didn't is good news. I'd wondered what happened with the seawater greenhouses, now seems they are alive and flourishing in Australia, great!

    Followed up the story and found a couple more video clips:

    earthrise - Saltwater Greenhouse

    Sundrop Farms ABC Gardening Australia

    Also from their website:

    Website: Sundrop Farms

    Yes exactly how I feel, and if we want to create new habitable areas, grow crops and support new colonists in our solar system, is obvious that right now the best place, by far the best return for the money you spend on it, is here on Earth sorting out our problems here, and greening the deserts.
    Yes,  if we can't get our CO2 back to 0.03% of the atmosphere from 0.04%, here on Earth with billions of people and all the technology ready to hand, what chance can we have with controlled terraforming of a planet several months travel away with only a small colony of people? I expect you read my section on magical thinking for terraforming in the new article, anyway here is the link for anyone who hasn't seen it yet:

    Will we Build Colonies that Float Over Venus like Buckminster Fuller's "Cloud Nine"?

    Yes some of the newer ideas for advanced fusion concepts, such as the salt reactors, look pretty good. I used to think that nuclear reactors were impossibly dirty, creating waste that would persist for tens of thousands of years or more and still be a danger for anyone who digs it up millennia into the future (maybe after losing all technology, like C19 with radium).

    But no longer seems it has to be like that. And it may be possible to "burn" the longer lived radioactive waste also.

     Quite possibly, if plants are simpler also, better than nuclear fusion to start with - the first big fusion plant is a huge thing and has some issues with it still, just a demo reactor so far.

    I also wonder if some of the micro-fusion ideas such as the polywell, or the laser fusion might become a reality first before the tokamak.
    Hi Robert,
    I'm a writer with a bit of a humanities background, and so cannot comment on Polywell verses other forms of fusion. For a long time I blogged *against* nuclear power, until I met Barry Brook's blog online and started arguing with them. They convinced me!

    In summary, the key points that I came to understand, and in the layman's terms I use to communicate about it, are that nuclear is the:

    *SAFEST form of large scale power we have, (as George Monbiot says, coal kills more people in a week when it goes RIGHT than the *whole* history of nuclear power going WRONG!),
    * CLEANEST (with low emissions, and waste burning Integral Fast Reactors. There is *some* waste left over after running it through the fuel cycle dozens of times, but that can be stored on site for 300 years and then is safe!)
    * CHEAPEST form of clean *baseload* reliable clean energy. (There are a few geothermal and hydro hot spots that can do 100% reliable renewables, but they're rare).
    * and is effectively renewable, with erosion constantly carrying more uranium particles than we can use down to the ocean. We can extract 1kg of uranium from seawater for about $300. 1kg also happens to be the amount of uranium to power a whole human life! It's the size of a golf-ball, and only costs $300 worth of fuel to power an entire life. (That's the fuel cost alone: the expensive part is the nuclear infrastructure).

    So until a super-cheap super-battery comes along, renewables just can't do the job. I hope some kid cooks up a superbattery soon, because Australia, at least, is simply unready for the word 'nuclear'. People run kicking and screaming, when in reality they should probably be more concerned about climate change and plastic rubbish in their foods than the rare chance that a tiny percent of our deserts might become 'off limits' in the EXTREMELY unlikely event of an accident!

    Rightio, yes I've found out much the same here. Which is not to say that all nuclear power plants are good, the one in Japan obviously  hit major issues for instance. I'm not sure that all present day plans for nuclear power plants should go ahead.
    But - that the way I'd always thought it was until just a few years ago - that nuclear plants unavoidably create long lived 100,000 years waste, doesn't seem to be the case any more with new ideas and designs, though it was true last century. That is so long as it is developed in that way. If someone designs a plant and then buries plutonium  I think that's a really bad idea mainly because in some low tech future people might dig it up, not realizing what it is and how hazardous it is. Also our planet does get regularly hit by pretty large meteorites over time periods of tens of thousands of years, and nuclear waste with half lives in the hundreds of thousands of years does have probably quite a chance of getting hit by a meteorite.

    But if it can be done safely, then that's all good.

    Didn't know that it was likely to be economical to extract uranium from seawater.

    Yes with polywell - that's better than nuclear fission, also normal nuclear fusion too if it works. If the Boron 11 version works, it can run it with almost zero radiation effects, as that reaction is aneutronic, produces no neutrons. It's interesting enough that the US Navy are actively developing it with a program of several million dollars a year. It's interesting because a full scale power plant would be about the size of a two story house, really tiny, able to serve as the power supply for a small  community, also very portable so that's probably why the US Navy is interested.

    All though developed with US Navy - they have said they will share the techology,  but sadly, it is a secret project, they don't share their data, just progress reports. Lot's of others working on it independently, but they are handicapped because they don't have access to the US Navy data.

    Somewhere there is something by the US Navy saying that they will share the technology once developed and not just keep it for themselves. But I can't find it right now.

    I think also lots of potential in solar power - as solar panel prices come down, there is enough power certainly for all our needs just from largish solar panel plants in the deserts of the world. They could also be integrated into roads, and roofs of houses and such like. Has already reached break even in Australia where without any subsidies, a consumer solar power unit pays for itself (because you don't have the extra costs for transmission from the power source).

    There is also the idea of solar power from space, and I think that might well be where we get it eventually, once we have cheap lift into space + space mining underway, solar satellites beaming microwaves to Earth seems safest of the proposals there, where even in the centre of the receiving station you receive less than the safe dose of microwaves.

    Just a thought, of course I am likely wrong, future has a tendency especially in technology of making fools of anyone who tries to make hard and fast predictions :).
    BTW for anyone else reading this, the biochar is a really interesting project.
    It is a way to use waste products (coconut husks for instance or straw etc) for fuel - and at the same time it is carbon negative. You burn it in a way that generates charcoal which you then bury in fields to increase their productivity. 

    So reduces fuel needs, takes carbon dioxide out of the atmosphere, and improves the soil and so improves productivity all in one go. 

    It is a technology that was developed by the ancient Mayans, for use in the Amazon rainforest, originally. The modern technique was developed as a result of studying the soil that resulted from Mayan agriculture.

    It's not likely it could completely undo the effect of our anthropogenc contributions to carbon dioxide in the atmosphere quickly or totally offset the other ways we create carbon dioxide. But it has its place as a part of the mix of everything we are doing on the issue, and would count towards carbon credits, so you could also earn carbon credits by doing this.
    A seedling grown in a potting mixture including Biochar. Cornell University scientist Johannes Lehmann thinks biochar is crucial way to reduce human carbon emissions, by burying them. Photograph:

    Hi Robert,
    I'm a writer with a bit of a humanities background, and so cannot comment on Polywell verses other forms of fusion. For a long time I blogged *against* nuclear power, until I met Barry Brook's blog online and started arguing with them. They convinced me!

    In summary, the key points that I came to understand, and in the layman's terms I use to communicate about it, are that nuclear is the:

    *SAFEST form of large scale power we have, (as George Monbiot says, coal kills more people in a week when it goes RIGHT than the *whole* history of nuclear power going WRONG!),
    * CLEANEST (with low emissions, and waste burning Integral Fast Reactors. There is *some* waste left over after running it through the fuel cycle dozens of times, but that can be stored on site for 300 years and then is safe!)
    * CHEAPEST form of clean *baseload* reliable clean energy. (There are a few geothermal and hydro hot spots that can do 100% reliable renewables, but they're rare).
    * and is effectively renewable, with erosion constantly carrying more uranium particles than we can use down to the ocean. We can extract 1kg of uranium from seawater for about $300. 1kg also happens to be the amount of uranium to power a whole human life! It's the size of a golf-ball, and only costs $300 worth of fuel to power an entire life. (That's the fuel cost alone: the expensive part is the nuclear infrastructure).

    So until a super-cheap super-battery comes along, renewables just can't do the job. I hope some kid cooks up a superbattery soon, because Australia, at least, is simply unready for the word 'nuclear'. People run kicking and screaming, when in reality they should probably be more concerned about climate change and plastic rubbish in their foods than the rare chance that a tiny percent of our deserts might become 'off limits' in the EXTREMELY unlikely event of an accident!

    GE have the S-PRISM ready for commercial deployment.

    We've just got to get legislative approval for someone to build one of these things, and then the world can stand back in awe as they demonstrate the financial viability of burning all that waste! Barry says because nuclear waste can run the world for 500 years, the world's nuclear 'waste' stockpile is now a *resource* worth $30 TRILLION dollars. Don't tell anyone: I want Australia to make a grab for it in the name of 'storing' it! ;-)
    (To think governments are still wasting billions trying to think of ways to store this waste for a million years, when they should be building the reactors to fission away the problem in abundant clean energy!)

    Oh yes, I remember reading about the Prism one. The UK government is interested in using it to reduce our plutonium stockpile.
    One rather sad thing about the news reports I saw is that the UK plan seemed to be to use up the fuel as quickly as possible. Seems is one way you can run it, where the aim is to get as much power out of the plutonium, and another way where the aim is to get rid of the plutonium quickly with less power produced, and that they are going for the second option.

    That seems a bit short sighted if it is indeed such a great source of power as all that. I can understand they might want to do that for safety reasons, the idea that for as long as they have the plutonium it is a safety issue so want to get rid of it quickly if they can. But seems a shame that it has to go that way, if we do really have several centuries worth of power locked up in the plutonium that needs to be destroyed. I hope that if so then somehow it can be released as power. To get rid of it all within a few centuries, to my mind, is as good as to get rid of it quickly as the main concern is over periods of tens or hundreds of thousands of years, not so likely to get a big natural disaster threatening it in the next century or two. But just my own opinion there :). Anyway I'm not sure what the latest is on this. Interested to hear what happens. Like we probably shouldn't have made the plutonium in the first place, arguably, in a rather unstable world situation, but now it is there, best to make the best possible use of it.
    I love Roberts' articles. He writes in a clear style and is very interesting, his enthusiasm is infectious. Makes me want to re-read some of the classic Sci-Fi novels of my youth. Thank you Robert.

    I did. Well, I think. It was either a comment on one of Robert's pieces here, or David Brin's, that someone mentioned a sci-fi anthology of old stuff so I bought it. 

    As I said then, if you watch old sci-fi movies, they date rather poorly because of visuals, but if you read those old stories, a lot of them could have been written last week.
    Thanks Bobby, glad to hear it, yes I have old classics of Sci. Fi. I read over and over :). Have several boxes of them up in my attic (after a move) look forward to unpacking them some time.
    Finally! Someone comes out with the truth, which is that teraforming is incredibly difficult, hugely expensive, and takes a hundred thousand years to be a success.

    Far easier, then, to seek out, among the thousands upon thousands of exoplanets already discovered or yet to be discovered with the next generation of telescopes, an Earth-like planet -- a blue orb in space that is just as hospitable, or nearly so, as Earth.

    Robotic probes can visit the likely candidates within a few dozen lightyears' distance and send back their findings within a few thousand years. Then, a Goldilocks planet having been found, one that is neither too hot nor too cold nor too massive or too light etc., colonization can begin. Human germ cells, snugly packed in deep freeze, are transported by robot-crewed spaceship across the vast expanse. A few decades after departure -- time shortened by dilation due to traveling at up to two thirds the speed of light -- Noah's Ark II arrives.

    The robotic crew does not begin gestation and incubation of humans just yet. Surveyor bots map the planet and carefully determine the most promising habitats. (It will also be necessary to carry a complement of nuclear arms to break any resistance in case there are hostiles already living there.)
    Eventually the first generation of explorers is birthed by robo-wombs, reared by robo-nannies, and educated by robo-teachers. Finally the glorious colonization begins.

    Mr. President, sir, I hereby place at the disposal of the U.S. government my brain for uploading into the ship's onboard computer system. I have thought long and hard on many of the issues that touch on interstellar colonization. I believe I would be an asset to our program.

    Please contact me in the usual way to signify your support for my proposal.

    Okay yes, that's an interesting way to do it, the seed colonies, is a way that would work if you want to send humans to another star, if you can also work out how to bring them to maturity at the other end. 

    I think though there are some potential issues with it also that would need to be thought through. First is, is there life on that planet already? Just as for Mars, if it is a habitable planet, it might well have life on it already. If so, well that does raise all sorts of issues of whether you should terraform a planet that has life on it already. Plus as for Mars if it has life on it, that your first thing you'd want to do is to study what is there.

    Plus, the life might be incompatible with Earth life. Indeed if it is independently evolved, is almost certain it would be. At least differences in how the DNA encoding works, how it is transcribed, what the bases are, probably what the backbone of the DNA is made of also. 

    So then you have three possibilities. One is that DNA always takes over from the XNA (Xeno DNA). One is that the XNA always takes over from DNA, and the other is that they coexist.

    If they coexist, may be many ways that could happen, that may be in an uneasy way that they are in continual conflict over the same resources, or may be that they work together as communities of creatures or symbionts, each supplying things that the other lacks - or that they have their own niches - or in more extreme case that they can't survive in each others habitats at all -  e.g. that XNA does better at much higher temperatures or much lower tempratures than DNA - e.g.  if there is life in the extremely cold methane / ethane lakes of Titan then it is likely to be so different from DNA that neither could survive in each other's habitats.

    So is a lot to find out and think about before you decide what to do, beyond whether the planet is an Earth clone or near to.

    Then - why are you doing it? That's one of the things I brought up in the article on Why Didn't ETs, Or Self Replicating Machines, Colonize Our Solar System Millions Of Years Ago?

    The thing is, if it is just one new star you seed in that way and then it stops at that - then fine. But once you have the technology - then that star could then send out its own seed colonists - maybe just a thousand years later or if it starts off already with all the tecchnology it needs as may well be the case, maybe just after a century or less. Doesn't matter how long it takes. As soon as they then send off new seed ships to other stars and are successful - you then have exponential growth. Before not long in geological time entire galaxy is filled with humans.

    Which you might think, great! But they would evolve and change and by the time they colonize the entire galaxy may not be recognizably human at all and may have values you find very strange - and some of them may be reckless and build von Neumann machines that would then proceed to turn the galaxy into things that make sense to them - but maybe makes no sense to us. So - e.g. the paperclip event horizon - some ET - but in this scenario could be a descendant of humans - decides it is a great idea to make a self replicating machine that turns everything into copies of itself plus loads of paperclips. But it then gets out of hand and evolves to be more and more efficient at turning everything into paperclips -and is nanotechnolgoy and turns out to be pretty much unstoppable. And then one of these eventually finds us and turns the Earth into paperclips.

    The same is also possibly true of colonists in habitats using materials from the asteroid belt also. Once you turn most of the asteroid belt into Stanford Toruses you have trillions of colonists.Then eventually you surely start to do the same with the Oort cloud - unless specifically decide not to - and then - you end up colonizing the Oort clouds of other stars because the clouds mingle from time to time as stars pass close to each other - so eventually you end up colonizing the galaxy that way too, with many more colonists.

    So - I had the idea - this might be why we don't see ETs here - because ETs are either reckless and so destroy themselves or their civilization by any of many things that can go wrong. Humans have already survived a few such as nuclear war, all out biological warfare leading to plagues that decimate humanity - total destruction of the ozone layer - although a lot has gone wrong of course - we have avoided some of the very worst disasters to date. A more reckless ET might not.

    So perhaps all ETs either destroy themselves - or else - they are cautious enough and forward thinking enough to take good care not to seed the galaxy with destructive descendants or von Neumann machines. Or - that they naturally reach a peak population. Humans have already reached peak child, that happened a year or two ago, though population is growing there are the same number of children this year as a couple of years ago, the extra population of the Earth is due to people living longer, which seems to suggest, that we may also be approaching peak population too.
    Or - that we are first ET in our galaxy which is also a possibility in which case responsibility is up to us. 

    I think particularly when we start to have space colonies, humans in space will need to be more peaceful than we are on Earth - or none of the colonies will last long as they would be so very vulnerable to any warfare - can't see any way they could be hardened against deliberate attack. Just a ship that travels at full speed and doesn't stop would destroy a habitat. 

    The Outer Space Treaty is a good start there. So I think either we destroy ourselves in space before we are able to do much at all - but on our history so far - I do think there is a good chance we don't. If so then we would be necessarily far seeing as a species and then - if there are any dangers in seeding the galaxy then we would find out and investigate carefully and not do it or limit it in some way to prevent that happening.

    So - yes I think it could happen something like that but probably would involve a lot of finding out new knowledge first and developing in our wisdom and understanding as a species, and is probably not really possible to work out in detail how it would happen as there would be new discoveries along the way that we don't have yet.
    Mr. Walker, you humble me by taking the time to pen a long, thoughtful reply to my only semi-serious comment. Am feeling a little ashamed right now.

    That's all right, I knew it was a humerous post and I enjoyed it too :). No need to apologise at all, and stimulates imagination, but thanks for the apology!
    Not to mention the Martians might have something to say about the matter.

    "Ack-ack-ack-ack-ack!"—Martian spokesman.

    Terraforming Mars is a pipe dream.

    Because Mars has no molten core nor consequent magnetic field, it cannot maintain a significant atmosphere and ozone layer. Not even viruses are known to survive the resultant UV radiation. Any accessible H2O is sublimating into space and will go on doing so. Life is simply impossible without the radioactive decay that has kept the Earth's core hot and the magnetic field active for 4.5 billion years. The laws of physic preclude ever jump-starting on Mars this incredibly powerful process.

    The input of energy onto the martian surface is insufficient to counteract entropy and maintain the structures and functions essential to life. (The same problem caused the Biosphere experiment to collapse). Mars lacks sub-crustal magma, needed to provide the life-giving forces associated with plate tectonics (mountains, volcanoes, and the transformation of elements). It's too far from the sun to absorb enough sunlight for significant, outdoor photosynthesis or a viable hydrological cycle (as if those things could occur without an atmosphere). Even assuming you could find a source of water, huge nuclear power plants would be necessary to grow food indoors and support even a modest human colonization. (Unhappily, in this barren environment, there are no fossil fuels).

    There are intractable, physical reasons why Mars is lifeless--- and why it will remain dead, and inhospitable, despite any number of hare-brained schemes.

    Okay, well something a bit like that is what scientists used to think about ten years ago, which shows how little we understand the planet. There are many major things that we don't know. We can see it really clearly from orbit, but have almost no ground truth.
    For an analogy, it's a bit like observing Earth from orbit and then speculating about what kinds of birds and animals might live in the jungles, when the only evidence you have is from a few rovers that landed in our flattest desert regions, and most without any means of detecting life directly.

    However we do have a pretty good idea of physical conditions on Mars, if not of whether there is life there, now. And there is a lot of striking evidence now that suggests that life could survive there and may well even be there now on the surface. Most striking, the experiments by DLR aerospace who found it possible to grow arctic and alpine lichens in simulated Martian conditions without any water, just the humidity of the night time air - which reaches 100% humidity - and simulating also the thin atmosphere, and the cold day night cycle, and the UV radiation. They continued to grow apparently normally - very slowly of course as they are lichens, but were still photosynthesizing and metabolizing - in semi-shade conditions directly on the simulated Martian surface. This is an on-going series of experiments.

    There are also theoretical reasons for supposing that there is a thin layer of water a cm or so below the surface it may be damp, very cold, very salty but damp, actual liquid water due to deliquescing salts at certain times of day - and this may be a habitat over much of the surface of Mars, though not where Curiosity is as that is too dry, doesn't even have ice near the surface. Then also even in equatorial regions, evidence for actual flowing water as in the warm seasonal flows.

    There is gradually mounting evidence for all this. Started with Phoenix when there was evidence for possibly deliquescing salts from what look like droplets on its legs and grew and then fell off - sadly couldn't be analysed. Then also isotope measurements of the atmosphere show first that some of the CO2 is recently emitted from volcanoes - so over geologically recent times then Mars has been active - and then the O2 signature showed something else, that intriguingly, the Oxygen in the CO2 is not the same oxygen that got emitted from the volcanoes, isotope signature is wrong. Some of it must have exchanged atoms with other sources of oxygen and about the only way that could happen chemically is if some of the CO2 in the atmosphere has reacted chemically in presence of liquid water. So has been liquid water on the surface of Mars, extensive enough to be able to change the isotope signatures of the atmosphere so not just tiny amounts either - could either be occasional melting due to meteorite impacts - or these hypothesized sub surface layers of deliquescing salts over much of the surface of Mars - or some other source, even deep down aquifers connection with the surface but whatever, is promising for habitability and perhaps present day life.

    So situation has changed hugely over the last decade if you look at the leading edge scientific discoveries about Mars. Was a major conference earlier this year on the Present Day Habitability Of Mars. The whole thing was video recorded and you can watch it online:
    The Present-Day Habitability of Mars 2013 | UCLA Planets

    Here is a report of the new results about the equatorial warm seasonal flows: 

    The arrows show one of these warm seasonal flows, form every year - and seems to be a flow pattern for liquid - and what's more - form only when the temperatures rise above OC on mainly S. facing slopes and now been found even in the equatorial regions of Mars - is hard to see what else it could be except some form of flow of liquid water - presumably salty water. (BTW salty here is in chemists sense, of "salts" - not likely to be much actual sodium chloride as on Earth - more likely to e.g. have a lot of perchlorates - which is actually good for life though toxic for humans, some microbes use it as a source of energy).

    The source of it is unknown and is a bit of a challenge to explain how the water can continue to flow year after year - how is it replenished? Is hard to see how it could still be flowing now if only source is ancient ice deposits laid down when the Mars atmosphere was briefly thicker when its axial tilt was greater a fair while ago geologically.

    But Mars h as many mysteries at present, things we don't understand, and things that were once thought impossible, and then later proved beyond doubt such as for instance the early oceans.
    This is the article about it: Water still flows on Mars, potentially harboring life – and we need to be careful not to contaminate it

    You are right that those are all major challenges you mention, e.g. that it is further from the sun, so harder to photosynthesize, that it has no magnetic field to speak of so much easier to lose even what atmosphere it has, is also colder, many things make it harder to be habitable than the Earth. 

    However, is a matter of many details that we simply don't know the answer to. Is I think indeed possible that Mars is impossible to terraform as you say, because too cold, too small, lost its magnetic field. On the other hand it was more habitable in the early Mars, when it had an extensive ocean, excellent evidence for that now. So that suggests that maybe there is some possibility of terraforming, it all depends on how it lost its atmosphere and ocean and if there is enough water and air left on Mars in its surface, and on detailed understanding then of what would happen if we tried to warm it up again.

    I was careful in this article to keep the balance between those. We simply don't know, and I think to say Mars can't be terraformed - though it might be true, at least without heroic mega-engineering such as crashing moons into Mars etc - it might also be true the other way that it can be terraformed .

    Is certainly a major challenge, I think, it needs a lot more knowledge and understanding than we have now to settle the question either way or to find out how to do it if it can be done.

    See also my Might there be Microbes on the Surface of Mars?

    BEHOLD!! The Mightiest and Most Thorough Concern-Trolling of All Time!

    You are welcome to your views on this :). Just saying it needs to be debated and understood. If the things I said here are incorrect then we should discover this as we learn more about Mars.
    As far as I know then what I've said here summarizes current scientific understanding about Mars, and possibility of terraforming. The conclusions I drew from them about need for caution and projections about what might happen in the future are my own. 

    But the OST and planetary protection legislation is clear that we would need to have a better understanding of Mars before we could send humans to the surface, I expected what I say here to be controversial as there are of course several significant space advocacy groups and private companies who have as their "mission objective" to send humans to the surface of Mars as soon as possible. 

    I'm not so far away from that though. I think it is of great value to send humans to Mars orbit and to explore it via telepresence. Is just the final step of sending humans to the surface, that I think we simply don't have the knowledge about its consequences to make that decision yet in any responsible way, if we think about what is best for the future - even of prospective colonists themselves and certainly for humanity as a whole.

    In orbit around Mars in an orbital colony - you could explore the surface via telepresence with telerobotic avatars. This would actually give you a more immediate experience of living on Mars than if you were actually there - because instead of the dull muddish reddish gray landscape and skies (which you rarely see in press images, nearly all colour corrected) - you can actually see details in colours adjusted to human vision. Also without a clumsy spacesuit, and with haptic feedback, you could touch the surface of Mars, feel it, much more directly than with spacesuit gloves. And could run and walk over the surface in your avatar, once the technology matures, is pretty close to being able to do that now. 

    It would actually be better than being there in person. And plenty of materials in Deimos for cosmic radiation shielding of your orbital habs and for resources.

    If this vision is right, if I haven't somehow missed something important there - what I'd like to see is for these various Mars advocacy groups to focus on sending humans to Mars orbit instead of to the surface. That is also more easily affordable. Even Robert Zubrin suggested his Double Athena project as a first step to Mars, a bit like Dennis Tito's idea for Inspiration Mars, but in some ways more practical. Have opportunities for it every two years - and has much lower return velocity so easier to return to Earth, not the problem of atmospheric braking you have with Tito's plan.

    So is actually the same as the Mars society as far as the first stages are concerned, and I'm saying - do more of that, focus your attention on sending humans to Mars orbit, and to explore the surface thoroughly from orbit, start on resource utilization from orbit too - and water from Deimos for supply to Earth orbit or to the Moon - or indeed eventually, to Venus also if we start cloud cities in the Venus atmosphere - is one of the few ways a Mars colony could support itself easily financially anyway - so is a good thing to get started on whatever happens in future.

    And then to keep an open mind about whether we should send humans to the surface eventually and make no irreversible decisions such as introducing new life to Mars until you are totally sure. And when it comes to deciding whether humans can go to the surface without contaminating it which some still say (doubtful myself) - that needs to be based on direct observation on the surface. A good start would be to look at our existing spacecraft there and see what has happened to microbes on the earlier spacecraft that landed and crashed on Mars for ground truth.

    For more about this see my Telerobotic Avatars On Mars With Super-Powers ("Teleporting" from orbit) - Search For Life - And Long Term Exploitation
    Of course what you're missing is that we'll have gotten in LOTS of practice at terraforming before we try it on Mars, because we're going to have to spend a couple of centuries terraforming Earth if we want to survive to reach the other planets.

    Yes, good point, by learning to help Earth to heal itself, we are learning a lot about terraforming.
    I think not enough by itself because Earth is only the one planet with a fair number of things probably unique to it, in our own solar system certainly. Earth's "Gaia" certainly wouldn't work at all if simply transplanted to Mars. 

    Even move Earth itself out to the orbit of Mars, with the highly elliptical orbit and remove its Moon so its axial tilt varies as for Mars and even with the continental drift it might well fall into snowball Earth or in other ways become far less habitable. 

    Remove the continental drift, make it a tenth of the mass of Earth (as Mars is), remove the magnetic field, and I think the chance that Earth's Gaia would survive all that and continue to keep the planet habitable anything like it is today is surely a bit remote. Then remove much of the atmosphere and most of its water as well, and that gives you roughly, present day Mars.

    I think we might get better ideas about whether it is possible, and how,if we find exoplanets like Mars around other stars with atmospheres and see how they work.
    I like your point about McKay or Robinson's scheme of importing atmosphere via crashing comets to Mars' surface.

    Due to Mars' taller scale height, a larger mass of volatiles would be needed to give earth pressure. Leave asteroidal volatiles where they're at and they could be used to make pressurized habs at the asteroids. As you point out, utilizing many asteroids would give far more real estate and usable resources than a planetary surface.

    Deep gravity wells suck. But maybe Luna's an exception. The short trip times and frequent launch windows somewhat compensate for the extra delta V. If the more optimistic estimates of cold trap ice are true, the moon's a very attractive target.

    In an earlier blog you were kind enough to point to my scheme of using some NEOs as cyclers to the Main Belt. Have you seen videos of the Hilda asteroids? The Hildas are natural cyclers between the Main Belt and Jupiter's Trojans.

    Oh rightio, yes, in Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths, ingenious idea. 
    Here is the link to your scheme again for anyone reading this: Railroad Towns.

    No I hadn't seen the videos of the Hilda asteroids, have just looked them up now, and found them, spectacular :).

    Here is a video showing the Hilda asteroids in first half (second half shows the Trojans).0

    Yes I agree Moon seems a very attractive target if the optimistic estimates are true. Even if not ice, but organics, again very attractive. 

    They are also conveniently, right next to the very easiest place on the Moon for a first colony, the peaks of eternal light where there is sunlight almost all they year around except when the Moon is in eclipse, so no need to worry about lunar night, or about how you supply the habitat with energy during the night, or about how to engineer the exterior of your habitat and any explosed machinery for regular huge temperature changes of 100 C to -173C and back again, every lunar month. Plus, temperature is just about right to make it not too hard to maintain habitat at human friendly temperatures.

    It may be the most easily habitable place in the solar system outside Earth because so easy to access also. Though, I've been thinking about Landis's Venus cloud cities idea, it grows on you, may be even more habitable long term if there are no "gotchas" to prevent it. Without any terraforming needed at all, the cloud tops of Venus are not far off as habitable as Earth if you make your own oxygen and protect the outside of your habs from sulfuric acid and extract water from the sulfuric acid. Far more so than Mars I believe, and possibly better than the poles of the Moon also, but future will tell :).

    I wonder what anyone here thinks about my idea for rotating carousels to provide gravity in the lunar colony? Not rotating entire hab, but just a thin shell of living quarters inside it, in a bigger hab if say a couple of hundred meters across, greenhouse domed, have like the living habs around the outside rotating continuously - perhaps on a track or something like that - at just the right speed for 1 g for the inhabitants. Smaller habs just rotate the entire room - and easier to construct than e.g. fairground rides on Earth because of the low gravity.

    I think it could also be a breakthrough for making Stanford Torus type habs, as no need to rotate entire hab at full g, rotate at 1/100th g say, just for the plants, and inside the big hab have smaller habs for colonists rotating independently on a horizontal axis relative to the ground of the habitat - a bit again like a merrygoround or carousel - and that is where you sleep and do desk work, and e.g. watching TV or indoor type entertainment, make sure you are indoors as much each day as is needed to be healthy (how much we don't know might be enough just to sleep there for instance).
    There is also the intriguing possibility of ice inside the recently discovered lunar lava tube caves.
    Seems at least possible - and if the polar ice formed by condensing of water from brief moments when the lunar atmosphere is thicker after an impact - seems to me quite likely it would also form in the caves too. Again like the poles, more constant temperature because underground though doesn't have the advantage of continuous sunshine year round.
    "Another idea proposed is that the sheltered environment and consistently cold temperatures in the lava tubes may serve as a trap for water ice and other volatiles"

    from: Detection of potential site for future human habitability on the Moon using Chandrayaan-1 data
    The lunar carousel notion prompted a blog entry:

    Great! Yes the 200 m was based on a back of envelope calc.  I did a while back can't remember now but going by your table presumably I assumed 3 rpm as that fits your 99 meters there and is within the range that at least some people find tolerable. So full g with a 200 meter wide hab. 
    If you are restrained so you can't move your head you can withstand well over 10 rpm for short periods. Experiment involving people in a centrifuge for 30 minutes each day for 30 rpm - I found it in this discussion in Selenian BoonDocks - if you just need 30 minutes of full g a day for instance then that would do you fine. 

    Or if 8 hours a day is fine, could do it as you sleep, and you sleep in a hammock in full g somewhat restrained from moving about to reduce effects of motion sickness as you sleep, and maybe 10 rpm.

    But in the link you just found, then people adapted fine to a remarkable 25 rpm. 
    Spinning Brains One day, astronauts might travel through the solar system onboard spinning spaceships. Can human brains adapt?

    Maybe especially if you only need the high g for a short while or when asleep, then that would be fine too? 

    At 10 rpm a 9 meter radius hab has full g. 
    At 15 rpm a small 4 meters radius hab can have full g. At 25 rpm a tiny 1.45 meters radius hab can have full g. 

    I work this out the easy way with this online centrifugal force calculator :).

    With such a small hab your feet and heads at wildly different g force, especially at 4 meters.

    But if it is for sleeping, you just sleep in beds and spin up the beds in a circular room 8 meters or spin up inner shell of entire room -, and stop the spinning when  you wake up - then that seems likely to be well tolerable. 

    At 1.45 meters if you stood up then your head would be at zero g or even other side of the hab pulled away from your feet - but could do fine for a sleeping quarters type hab.

    Seems, you need long duration experiments because of adaptation - and what he says there about how people adapt to no longer experience coriolis and instead have a reverse coriolis when the wheel stops.

    That suggests the idea that perhaps you need to set the experiment running for weeks or months with volunteers - probably continually spinning them faster as they adjust and learn to tolerate larger rpm.
    Maybe even humans could tolerate well over 10 rpm as a working environment once they get used to it?

    After all with seasickness,  most people get seasick after a few hours in a rough sea - but sailors get used to it and can spend months at sea no problem. Perhaps it might be like that? 

    After reading your article and a bit of a google, I found this interesting idea too in an online forum: Surface-based centrifuge for lunar colonization - there the idea is to build a train that goes around a circular line on the moon perpetually, tilting train. 

    It's a bit like my idea of habs inside a larger greenhouse, where you spend much of the day that move constantly around the inside of a 200 meter greenhouse hab on the Moon - but without the greenhouse. You could build it without the greenhouse first and then at a later date when you can do more advanced projects then build the greenhouse as well. The habs would give extra security if the greenhouse is breached, retreat to the habs which would be made airtight. So double layer of security there.

    BTW could do the same in a Stanford torus too, have a perpetual train that goes in a track around the hab continually at night when people sleep - and maybe also in the day, slows down from time to time when people want to get in or out - or some other way of getting out while it is moving - so instead of entire inside moving at 200 mph inside the cosmic radiation shielding shell which seems a bit hair-raising somehow - have the whole hab + shielding rotating just fast enough for 1/100 g micro-gravity - for plants - and inside, a smaller like tube train but bigger for the living quarters for humans.

    - or else - the idea of lots of smaller 200 meter across - but according to these ideas - could perhaps be much smaller than that if humans can adapt to tolerate coriolis force - maybe just 20 meters across or whatever, for living quarters ./ hamlets where residents can spin their habs to whatever they like or tolerate.

    It has the advantage that as you are buiolding the hab for plants - first build the whole thing as a plants habitat - nothing for humans yet - and then once it is all nice and hospitable with breathable recycling ecosystem inside - then your colonists come and colonize a habitat that is already pretty earth -like  and then they can gradually build their spinning houses or tube trains inside as they colonize.

    Means much less infra-structure to start with. You build a bare shell just for plants, and spin at 1/100g - and then leave your colonists to do everything else.
    Also a couple of other things re toleration of spinning. I don't know if it is the same thing but might be. Dancers and ice skaters have to get used to spinning very quickly and it can make you nauseous but they get used to it. So that suggests again you could get used to higher rpm as you acclimatize. I wonder if they would get better results if they tested professional ice skaters?

    Also sometimes younger children tolerate this better than adults. So your ideal subject might be a young child who is also an ice skater :). They might be the best lunar colonists or orbital colonists if tolerance of high rpm is a bonus :).

    For figure skaters see Why Don't Figure Skaters Get Dizzy - notice how they say that even in a spin, the figure skaters get used to the spinning motion and the issue is the transition from spinning to stopped and vice versa so you acclimatize a bit even in a short spin such as a figure skater does.

    For young children tolerate spinning - maybe it is just that many adults develop conditions that mean they can't tolerate it so well rather than that it is particularly age related. Not found too much on it but this is interesting. For adults, motion sickness can take away fun of many rides - and I wonder - if fairground attendants might be good candiates for astronauts as well. 

    Oh and here is someone who spent 25 hours in a Ferris wheel so setting a world record  - began to get motion sickness at the end.

    Anyway surely needs more research rather than just design habitats and space settlements on the assumption that people will only tolerate 1 rpm or whatever it is you think it is likely to be. I'm pretty sure at least 3 rpm but sounds from this that, pending experiments to test it thoroughly maybe much more like 10, 15, even over 20 rpm could be tolerated may need to build up to it gradually and maybe good to recruit astronauts from professional ice skaters or at least - possibly good subjects for early tests of tolerance :).

    A lot of these experiments can be done on Earth. If we can achieve full g in a small hab like this by spining, then don't need zero g environment to prove that :). 

    Would be good to get ground truth on effects of low g on long term health too. But one thing there that seems pretty likely is that even if you remain healthy, if you grow up or spend many years at  lunar g, seems your muscles would adjust to it and you simply wouldn't be able to stand up or keep your head upright in full g on Earth - the big thing would be - can you then adjust to full Earth g after e.g. a childhood at lunar g. Or does it mean you are cut off from earth for life - and how long does adaptation take. If it means cut off from full g for life or months of adaptation needed e.g. if you wanted to go to college on Earth or just visit Earth for a holilday - that would be strong incentive to make sure that lunar habs are full g.. 
    I like the notion of a train around torus perimeter. In a conventional torus, the structure must be strong enough to carry mω^2r where m is the mass of the entire structure. In your scheme, m would only be the mass of the train. Fewer newtons to newtons means the structure can be less robust and massive.

    If the train is accelerated by pushing against the torus, that would induce a counter spin on the rest of the hab. So I would favor two train tracks, one clockwise and the other counterclockwise. That way the net angular momentum would be zero. The trains could use each other to brake or accelerate without having an effect on the rest of the structure.

    If most the hab is not spinning, I would imagine it would be easier to dock with.

    Yes, are you talking about the larger stanford torus type habs? Would be easy to have trains both ways with those.
    I think 1/100 g better than 0 g for plants. So that makes, for radius 0.9 km as in original Stanford Torus plan, diameter 1.8 km, that habitat outer wall is rotating at 21 mph which you'd think would be pretty easy to dock with even outer wall though more likely to dock with hub. 

    As rpm it's a leisurely 1 rotation every 10 minutes for a full scale Stanford Torus at 1/100 g. Docking with hub should be very easy I imagine.

    For full g the two trains need to travel at a rather fast 210 mph (and 1 rpm) but if you think of them as like maglev electric trains on Earth and they are inside a hab with meters thick walls for shielding, so seems safe enough.

    And if you can go to say 3 rpm with same scheme, your hab is only 200 meters across, trains now travelling at 70 mph. At 2 rpm diameter 440 meters, speed of trains for full g 102 mph.

    BTW just to say for anyone else reading this not that up on physics, this is only an issue during acceleration and deceleration, will only change the spin rate at those times. When it is in steady motion, even though the train is doing continuous work against friction to keep going, this does not spin the habitat any faster. Is all to do with conservation of angular momentum.

    How much it spins the hab in opposite direction, depends on ratio of the moments of inertia of the train and the hab. and is by conservation of angular momentum. If most of the mass is in the shielding, all that matters is the ratio of the masses.

    At 15 tons per square meter as is normal for torus (need to shield both roof, sides and floor so this is total mass per square meter of floor), train is going to be much less mass than the torus.

    E.g. Stanford torus 10,000 tons, suppose 1/10000th of the mass which is pretty massive, 1000 ton maglev train, then with torus spinning at 21 mph for 1/100 g, the train when it goes 210 mph would reduce the speed of outer rim of the torus relative to non rotating frame by 0.21 mph.

    If 10,000 tons train, then it would reduce the speed of the torus by 2.1 mph, and so on.

    Another idea, you could have a hybrid design between the original Stanford torus idea or all the other ones with fast rotating habs - and my idea of spinning internal habitats inside a larger hab, all built by the colonists later on only a couple of hundred meters across like carousels.


    As before have whole thing at 1/100 g for plants (or whatever they need). Then have say a quarter of the width of the tube (or whatever is needed) for humans - as a smaller inner torus that spins around at 210 mph for full gravity. That's where most of the humans live, and it has its smaller gardens in it too, for recreation and pleasure but most of the crops and forests etc are in the 1/100th g section. If the human occupied torus was continuous, all the way around, not sure even the air friction matters too much as maglev trains do fine enough on Earth in atmosphere, and will have plenty of power from the sun to power it.

    In this case with relatively large mass in the "trains", would definitely help to have two copies of these, to either side of the torus, each one an eighth of the width, and spinning in opposite directions and slowing down and speeding up in synchrony.


    More significant for smaller lighter habitats. 

    Could also, if it is inconvenient to keep the trains in sync or not enough space to have them in both directions at once - just have a very heavy weight e.g. beneath the track that is programmed to accelerate in opposite direction. This doubling of the mass to accelerate probably won't matter that much if you have regenerative braking, so that most of the energy that goes into accelerating is recovered, doubling mass won't double the power requirements, and also in steady motion, then the small compact mass will have less friction and air resistance, again won't double power requirements - and probably abundant energy from the sun anyway.

    All just ideas to think over, and see where they lead to if they turn out to be of any interest, which might be something quite different eventually if they suggest anything :)

    Lively discussion of this article going on in James Nicoll's blog - see: This could inspire any number of SF novels (but it probably won't)
    Perhaps we could set up some permanent Venus probes that would dwell in the upper atmosphere and send constant video feed (and other useable data) back to Earth. We could determine what kinds of coatings would be most effective in the Venusian atmosphere, try out different methods of distilling water and other nutrients from the atmosphere and at the same time watch the scenery at the cloud tops of another planet.
    After running for a decade or so, perhaps a mission with a human crew could be attempted.

    Yes, and as with the Mars direct ideas, have a fully functional habitat already there, or rather, several for redundancy, with Earth atmosphere inside, plants growing, working ecosystem and everything all set up and tested working, before the first human colonists go there. Habitats would be much lighter for the same volume if inflatable and just need to be designed to withstand the sulfuric acid rather than to contain tons of atmospheric pressure per square meter - so could send much larger volume habs than for Mars for same launch costs - and probably not much problem with winds just floating in the atmosphere same as for a hot air balloon or gas balloon on Earth.

    More comments on this article here: Red Planet Blues

    and here: on the James Nicoll blog: This could inspire any number of SF novels (but it probably won't)

    Short of the re-liquification of Mars' iron core, so that it will have an effective magnetosphere, all attempts at terraforming would be, in the long run, futile half-efforts: any costly created atmosphere will be steadily blown off again as it was the first time.

    A more effective approach would begin first with the search for large, high iron content asteroids which would be used for a direct but careful bombardment of the planet, in effort to re-start the magnetosphere: the trick would be to first increase the whole planetary rotation period, as the mass of the high velocity iron-rich asteroids heats the core–then, when the core is sufficiently fluid, to slow the surface with a counter-bombardment of water ice-rich asteroids until the surface reaches a rotation period suitable for life...

    and then wait till things begin to cool–several thousand years. And hopefully harvest (posthumously) the thanks of future generations.

    Yes could be. So far we don't know for sure how Mars lost its atmosphere - that is one of the main things Maven hopes to find.

    Then in this article I brought up many other things that would need to be thought through and addressed. If it turns out it doesn't lose its atmosphere to space at significant levels, or if your project of restarting its magnetosphere is undertaken - or some other way of doing it - you still have all those other issues mentioned in the article to address.
    Your idea might perhaps also restart continental drift - if not, we need a way to do that, or an alternative long term method of CO2 recycling back to the atmosphere from the sea bed. Then you have the distance from the sun, and the more elliptical orbit, lack of Moon, lower gravity so needing more atmosphere and oxygen in tons per square  meter, the various biological issues and so on.

    If you took the Earth's ecosphere and somehow could magically transplant it to the surface of Mars, fixed the atmosphere (e.g. with the dry ice from Venus idea), fixed the magnetosphere following your plan or somehow artificially generated, it would still probably turn into a snowball Mars because it has half the sunlight of Earth, so add greenhouse gases to counteract that, or giant mirrors in space to reflect more light onto the planet, add a Moon perhaps from the Jovian system to stabilize the axis long term. Then, you still have the third of Earth gravity (we don't know if humans are healthy in 1/3 gravity, also needs three times as much oxygen production per square meter to get the same oxygen pressure) and no continental drift and the elliptical orbit which at the least would probably cause major storms every two years - like the present dust storms but with stronger winds because of the thicker atmosphere - it's still not clear you'd end up with a stable ecosphere like Earth. How can we tell how significant those differences would be?

    And we can't magically move an entire ecosphere there, but have to build it bit by bit and have no previous experience of doing anything like that. It is true that it happened on Earth over a period of billions of years. That is kind of promising, but doesn't immediately mean you can do the same thing on a planet over a period of centuries or millennia, there may be tricky things there we don't know about, and Earth could be a rarity, for all we know maybe most planets in our galaxy fail to form a long term ecosphere. 

    And as for tweaking it if things go wrong, is one thing to tweak a greenhouse if you get a disease or fixing the ISS if you get problems with the air regeneration and other parts of the closed system. Is a totally different matter trying to fix an entire planet when you get lifeforms there that mess up the cycles, or wrong amounts of the greenhouse gases (too much or too little - see how hard a time we have adjusting the levels of CO2 on Earth to suit us - how hard would it be to adjust the greenhouse gas levels on Mars?), or gases build up poisonous to humans or the plants or animals we want.

    To my mind the best worked out ideas for terraforming Mars at present still seem to be one science fiction idea, piled on top of another, with no ground truth from experiments or data to back them up. With the risk that the process, if started in a blind way with insufficient knowledge, could spoil Mars for our descendants, whatever they want to do.

    Which is not to say it might be possible with vastly increased knowledge which could happen possibly sooner than we expect. 

    Meanwhile I think the thing to do is to explore, find out as much as we can, but think long and hard before we do anything irreversible such as introducing life to Mars that isn't there at present - or adding greenhouse gases, or colliding things with it. All that might possibly be something our more knowledgeable descendants just possibly might decide to do, I doubt if we will gain enough knowledge for it in a few decades, who knows though...
    And personally, I think there is at least a good chance that we will find out things amazingly interesting about life if we continue to study Mars in its pristine state (e.g. through increasingly sophisticated autonomouse robots or via telerobotics), either about the stages of evolution before the earliest life forms we know on Earth (already vastly complex with DNA, RNA, transcriptase, cell walls, metabolism etc etc impossible to arise by chance) - or about alternative paths of evolution even alternative forms of biology - or both. We have barely started on our exploration of Mars. See my How Valuable is Pristine Mars for Humanity - Opinion Piece?

    Have just posted about this topic to the New Mars forum - they have an excellent discussion section on Mars terraforming, and here is my post there: Trouble with Terraforming Mars - new post at
    There is lots of other interesting material there too for those with an interest in terraforming, Mars colonization etc.
    Excellent page Robert! I was all for send in the cyanobacteria seeding vessels until I read your article. Now, I've set my sights on Venus, or Venera as those pioneering Soviets called it. Keep up the good work and maybe the first manned one-way mission to Mars will in fact be an ISS type orbiting laboratory for ground telemetric exploration.

    Interesting article and discussion but I believe that I found two mistakes.

    First: If the 38% gravity on Mars might be too low for humans to live healthily in then this must be an even bigger issue on the Moon with far less gravity.

    Second: The strong seasonal winds on Mars that create the famous planetary wide dust storms are created by rapid carbon dioxide sublimation on its poles and this would clearly not take place on a much warmer Mars.

    The Martian year is also roughly twice as long as an year on Earth. So while the seasons are more pronounced on the two hemispheres due to a more elliptical orbit the changes in temperature happen at half the speed.

    Please feel free to correct me if I'm wrong.

    Okay, thanks, on the gravity - yes, didn't talk about that in the article itself, but in the comments.
    Yes low gravity for health could be an issue on Mars and on the Moon. One solution might be to have spinning habitats for artificial gravity inside the habitat - so that might be a solution for the Moon if it is needed.

    The subject has simply not been researched, no-one has done the basic experiment of putting a human into a low g environment  in orbit, resembling the Moon (or Mars) surface to see what effect it has on health, or muscle and bone strength. Also similarly we don't know if humans can adjust long term to the coriolis effects of a small rapidly rotating artificial g habitat.

    The other effect of low g on Mars though, which I mention in the article, is that it means you need three times as much atmosphere and three times as much oxygen to get the same atmospheric pressure as for Earth.

    You might be right about the dust storms. They would continue and get stronger as the planet warms up, but I see what you mean, perhaps they would subside once all the CO2 at the poles has sublimed.

    Good point there, thanks for the correction!

    Yes good point, that the changes in climate, though greater, happen at half the speed. I'm not sure if anyone has simulated this difference of climate of the two hemispheres in a model of a terraformed Mars, what the climate would be. I haven't come across anything that detailed yet.
    Thanks for your quick reply! This is all very interesting.

    Another thing that should probably be stressed is that the summers and winters in the northern Martian hemisphere are mild and only more pronounced in the southern hemisphere. That's because Mars is the furthest from the sun during the northern summer while closest to the sun during the northern winter.

    Okay I'll make that point. I can continue to edit the article and will do a new version with these corrections, plus will also mention the issue of low g on Mars, the situation that we don't know if it matters and the possible work around for it.
    Have updated it now
    Regarding Venus, I was wondering if the following makes sense: you start with one floating habitat which has a breathable atmosphere inside so you can create a biosphere with plants and trees (assuming Biosphere 3 shows the concept works of course). Step by step you add more and more of these floating habitats (using advanced 3D printing). Wouldn't this start affecting the atmosphere of Venus? It would be interesting to calculate how many of such habitats you would need before the atmosphere of Venus becomes thinner and the habitats start floating closer and closer to the surface of Venus. So you would fixate the atmosphere of Venus as biomass. I wonder how much biomass are we talking about in terms of mass and volume. And could it be stored in the habitats or would they become too heavy? And does the atmosphere of Venus have enough of the right elements to turn into the nutrients plants and trees need?

    And hopefully one day the atmosphere is thinned enough for the floating habitats to become cities on the surface.

    Okay - yes, sadly there is a problem with that idea. The thing is, there isn't enough water in the Venus atmosphere to take up all the carbon as organics. Carl Sagan had that idea originally but it doesn't work unless you can import hydrogen. In some future if we could import hydrogen from Saturn say, then you could use that to convert the carbon and also create water. If your habitats were continually importing hydrogen to make more water that could work very long term. 

    Venus does have plenty of water to let you construct habitats for a long time - if you find a way to separate it from the sulfuric acid, and also you would get most of the nutrients from the atmosphere, plenty of nitrogen and carbon dioxide of course, also sulfur plentiful. Some trace elements you'd need to get from the surface but most of the mass of the biomass would come from the atmosphere. 
    So, is plenty to get started with colonization. But there isn't enough water to combine with all the dense carbon dioxide atmosphere to remove it. Just enough for a layer of water a few meters thick over the surface of Venus.

    For summary see the Wikipedia article Terraforming of Venus

    BTW don't know if you discovered it, I discuss all this some more in Will We Build Colonies That Float Over Venus Like Buckminster Fuller's "Cloud Nine"?

    Thanks for mentioning your other article. I see you also mention sulfuric acid there and that some sort of (bio, photo) chemical reaction needs to be found which can get us the needed H2O. After some googling I mostly found chemical information on how to make sulfuric acid. The only thing of interest was which says that sulfuric acid is used to pretreat biomass to let it break down into simpler sugars. But i'm not sure if that would be applicable.

    Well Geoffrey Landis just says "Atmospheric carbon dioxide and nitrogen are a plentiful resource. Along with hydrogen reaped from condensing sulfuric acid droplets, the basic elements needed for human survival can be found in the atmosphere
    I'm  not sure how he'd do it in detail, but there is this idea, to just duplicate the way it happens naturally on Venus, I thought seemed possible.

    "One idea for production of water in Venusian cloud cities. The Venus atmosphere has a sulfuric acid cycle which produces water vapour naturally. 
    Sulfuric acid droplets fall towards the surface until eventually the water evaporates, and the sulfuric acid also decomposes, to sulfur dioxide (eventually) and water vapor. These two ingredients then rise in the atmosphere and recombine to make sulfuric acid and the cycle repeats.
    Perhaps by heating the cloud droplets with concentrated solar energy (solar furnaces) in the cloud colonies, and increase of pressure also if needed, we can separate the water from the sulfur dioxide in the same way to produce water for the habitats.

    Thanks, I'll look into Geoffrey Landis his article. I've mostly been interested in the planet Mars so far (next to our own beautiful home planet of course) but reading about this Goldilocks region in the Venusian atmosphere is intriguing. Your articles are a good read, thanks.

    Interesting article. While I appreciate some of the considerations made, would it not be practical to begin sending more satellites and robots to the Moon, Mars & Venus to collect data as we decide how to proceed?


    Yes exactly. The more we know the better chance we can understand it better. 

    With terraforming, I think it is likely to be some decades or more, before we can learn enough to have an idea what will happen if we try to terraform Mars. Or what else we should do if we decide not to terraform Mars. Are many other possibilities.

    For more on these issues, see: Imagined Colours Of Future Mars - What Happens If We Treat A Planet As A Giant Petri Dish?

    A question rather than a comment. Has anyone considered the climate effects of a terraformed Mars' land distribution? I've been reading lately about the geologic history of Earth, and during times when Earth's landmasses formed a supercontinent much of the land area in the interior was a hyper-arrid desert. Given the arrangement of highlands and lowlands on Mars, it seems to me that this might be a problem. Terraforming Mars when most of your land area ends up uninhabitable hardly seems worth it. Losing all that area for plant life and photosynthetic bacteria on a planet that already has trouble producing a high enough partial pressure of oxygen is also a concern. Any thoughts?

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