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I’m going to nominate California for its terrain and military presence.The “core” of California—the Central Valley, one of the nation’s most productive agricultural regions, shown on the relief map as a very flat brown region—is surrounded by the Sierra Nevada mountains to the east, the Cascade Range to the north, the Coast Ranges to the west, and the Mojave Desert and various mountain ranges to the south. There are, of course, roads and passes across all of these, but an army that controlled a fairly limited number of choke points could hold out against an attack by land for quite some time.An army attacking from Arizona or Nevada might be able to grab the Mojave Desert in the southeast, but I’m not sure what they’d do with it. And that desert includes a major Army base (Fort Irwin), a major Marine base (Twentynine Palms), and even a major Navy base (China Lake—testing ground for cruise missiles and other weapons systems). The Navy also has a lot of assets in the San Diego area (collectively called Naval Base Coronado), including NAS North Island which is home to a respectable chunk of the US Pacific Fleet, including two Nimitz-class supercarriers. And I assume a few Navy SEALs could be scraped up if need be, Coronado being where they train.The coast doesn’t have that many good natural harbors where you could unload a large invasion force—except for the major port cities of San Francisco, Los Angeles, and San Diego, which I assume would be well defended. I assume the assets at Coronado could intercept any major invasion from the sea. LA might be taken, but then an army would have to get over the Transverse Ranges, and there’s a limited number of passes they could take. I can’t see a Normandy-style invasion of Gaviota or Arcata or New Albion getting very far; they’d have to cross mountain ranges to reach any major population centers.On the other hand, I have an alternate answer: I would nominate Oklahoma as the other most defendable state. Not so much because of its military facilities (Tinker AFB is big, but they mostly do logistics, not warfighting), but because Oklahoma is excellently defended against military invasion by the simple fact of not being worth it. Like, OK, Mister Unfriendly Foreign Power, so you’ve conquered Oklahoma. Great. Now they’re your problem. What the hell are you going to do with it? . . . No, we have no idea what “Boomer Sooner” means either. . . . Now you just have fun trying to come up with a use for Weatherford, a task that has eluded us for a century. . .(To any Okies reading this—just harmless cross-border teasing from an adoptive Arkansan, nothing more. Oh, and congratulations on learning how to read!)

Thousands of years. But there is a huge amount to go wrong. Here is how they envision it in the Mars Society - a thousand years to get to trees, water and a landscape where humans can go out of doors without a spacesuit, using scuba gear:Images from the Big Idea (National Geographic Magazine) See also, How we will terraform Mars - by Jason Shankel and Terraforming Mars by Nicole WilletNote that after a thousand years, with trees, still you can’t breathe the atmosphere (that's why they are wearing scuba gear in the artist's impression), and there are no animals or birds yet. Also, if you research into their plans, you find out that behind the scenes there is a lot of mega technology to make this possible, if it works. For one thing, they will need to have hundreds of factories constantly producing greenhouse gases, and / or planet sized thin film mirrors in space to reflect extra sunlight onto the planet to keep it warm.This may perhaps seem a minor achievement to aim for, used as we are to breathing on Earth, but for a prospective Mars colonist, it as a big step forward. At the moment the air on Mars is so thin that the moisture lining your lungs would boil. This is not something you can adapt to. It is simple physics that no warm blooded creature with lungs can breathe there. If someone put you on the surface of Mars with scuba gear, you couldn't take one breath of air because your lungs would stop working immediately in the low atmospheric pressure of 1% of Earth's or less.Could we do this much? And is it worth doing even if we can, or should we stick to city domes, lava tube settlements, free space habitats and the likes?Our biosphere took hundreds of millions of years to develop on Earth and it might have gone in many different directions. The hope is that the development can be speeded up to a few thousand years, and directed so that you end up with a biosphere like that of Earth at the end, to pretty much the planet you want.Suppose we had another planet exactly like Earth, but with a thin carbon dioxide atmosphere instead of an oxygen / nitrogen one. Let’s stack all the cards in our favour and make it as easy to terraform as you can for a planet that doesn't have life on it. It’s got continental drift, magnetic field, the works. Now imagine it is in the place of the Moon as close and easy of access as that, I will suggest that we are not anywhere near the level of understanding needed to terraform it with any assurance of success.In the case of Mars it may well be the end result of a planet that had life in the early solar system. If so, adding life is not going to make it habitable; it could have the opposite effect. Perhaps normal photosynthetic life on Mars would form an ”anti Gaia” constantly pushing it away from habitability by cooling it down as soon as it gets warm enough for life to flourish.TERRAFORMING ATTEMPTS CAN GO WRONG - BADLY WRONGThere would be so much to go wrong. And I mean badly wrong, mistakes that would make it impossible for anyone to terraform it in the future. Especially if they involved introducing the wrong kind of microbe, there'd be no way you can roll that back.This can be something that builds up slowly, underground, or a few microbes spreading in the wind and weather. By the time you notice it is going wrong, or indeed, it may be a while before you notice the microbe at all amongst the hundreds of billions or even a trillion distinct species of microbes, on a partially terraformed world. It may well have spread throughout the whole planet already before you know it is there.The biologist Cassie Conley gave a simple example. She's the NASA planetary protection officer. And this is just for ordinary expedition to present day Mars, right now not even any attempt to terraform yet. Some Earth microbes, in the anoxic conditions on Mars and in the presence of methane (which may well be present there), could form calcite in underground aquifers - so turning them to cement basically."Conley also warns that water contaminated with Earth microbes could pose serious problems if astronauts ever establish a base on Mars. Most current plans call for expeditions that rely on indigenous resources to sustain astronauts and reduce the supplies they would need to haul from Earth.""What if, for example, an advance mission carried certain types of bacteria known to create calcite when exposed to water? If such bacteria could survive on Mars, Conley says, future explorers prospecting for liquid water instead might find that underground aquifers have been turned into cement."Going to Mars Could Mess Up the Hunt for Alien LifeIn more detail what she is talking about there is the anaerobic oxidation of methane that leads to formation of calcium carbonate in anoxic conditions . It's done by a consortium of methane oxidising and sulfate reducing bacteria. See summary here in wikipedia: Calcite - formation process - which links to this technical paper which goes into more detail.Calcite - calcium carbonate. In the anoxic conditions on Mars, in presence of methane, a combination of methane oxidizing and sulfate reducing microbes can cause calcite to form and so, basically, could turn underground aquifers on Mars into cement. Cassie Conley’s example of one way that accidentally introduced microbes could have unpredictable effects on Mars.When it comes to microbes introduced to an unfamiliar planet that behaves differently from Earth, with many differences in the chemistry, atmosphere, environment - any number of unexpected interactions could happen.Here are a few more examplesYou want to grow green algae to take the carbon out of the atmosphere and generate oxygen, but haloarchaea take over. These salt loving microbes are likely to feel at home on Mars, and they convert the sunlight directly to energy by a process using bacteriorhodopsin similar to the way our retina works - and produce no oxygen at all. How do you change the balance back to the green algae?As the climate warms up and it gets damp, but with no oxygen - those are ideal conditions for microbes that produce bad egg gas (H2S). Hydrogen sulfide smells like a sewer - the whole planet would stink.Maybe you want that (it’s a greenhouse gas and this is one suggestion for a way to start a process of terraforming). But maybe instead you are trying to get a carbon dioxide / oxygen ecology warmed by those planet sized mirrors, and the hydrogen sulfide producers take over and kill nearly everything. Or you are trying to produce H2S as a greenhouse gas and the cyanobacteria take over.One theory of many for the Permian extinction, the largest mass extinction in world history, 251 million years ago, is that it may have been caused by an initial upwelling of hydrogen sulfide that was then maintained by purple and green sulfur bacteria that thrived in the anoxic conditions. See description of their research here, and paper here. Whether or not that's what happened on Earth at the end of the Permian period, that it's a possibility for Earth might suggest that something similar could happen while terraforming Mars, which would start off naturally anoxic.Then, there's the possibility that there might be native life as well with unexpected capabilities. They could interact with your ecosystem and may not behave in the same way as the microbe whose niche they take over. Or may hybridize with Earth life via gene transfer. This is a very ancient mechanism (GTAs) which works between organisms as different as fungi and aphids. If Mars has any life that split of from Earth life after the development of DNA, it may well be able to transfer genes both ways with Earth microbes - and indeed in suitable environments such as warm salty water, it could do this rapidly, overnight.Or some microbe from Earth that’s harmless here and not even been noticed finds the different and unusual Mars environment to its liking and spreads everywhere, and within a few years or a decade or two becomes the most important microbe on Mars - and again maybe it doesn’t behave as you’d like it to.SO MUCH EASIER WITH A SMALLER ECOSYSTEMWith a small free space or lunar habitat of a few cubic kilometers, then we'd be bound to make many mistakes even with an experiment that small. But it is easily reversed (comparatively).If there’s a build up of some problem gas, you can scrub the atmosphere. If there’s an infestation of some diseases, insects,or mold, say, you can treat it with chemicals or tackle it biologically and eliminate it. In the very worst case, if something comes up which you can’t fix - you can purge the atmosphere, sterilize it if necessary and start again, learning from your mistakes.You can't sterilize a planet or purge its atmosphere and start again. Nor can you scrub it of problem gases or easily eliminate some problematical organism. Look at how hard it is for us to reverse an increase of a fraction of a percent of carbon dioxide, or to keep out invasive species from an island or continent, even for higher animals never mind microbes.It might even be a species introduced deliberately, and then it causes problems you never expected. The European starling in the US, for instance, introduced by shakespeare enthusiasts in the 1890s. That's not going to happen on Mars any time soon. But plants, yes, if they were successful. Kudzu might be a good analogy. Encouraged to plant it for erosion control, as a livestock feed and to make paper. Then it became a problem. Imagine a situation where some plant like that is out of control on Mars, what do you do?Even feral camels are an issue in Australia. Deliberately introduced, but in such a vast continent, it's hard to get rid of them. Rabbits also, famously. Then moving in the other direction to the very small, diseases of microbes might also become a terraforming issue. For instance bacteriophages, viruses of bacteria, significantly reduce the amount of hydrogen sulfide produced by sulfur bacteria. This can be used as a biological control if the problem is too much H2S - but it may be a nuisance on Mars if your aim is to produce as much of the gas as possible to warm up the planet.With a Stanford Torus or O'Neil habitat, or a lava tube cave or a city dome, none of these are an insoluble issue. You are not going to have a problem with feral camels, and rabbits also wouldn't be hard to deal with. With invasive plants like kudzu, at worst you have to sift the soil to remove the roots. Even sulfur bacteria, cyanobacteria, or microbes that could turn your water supply to cement - none of these are an insoluble issue. Even with bacteriophages, if you can't control them in any other way, just press the "reset button" of sterilizing the habitat, analyse what went wrong, and start again.VAST TIMESCALES OF MILLENNIA TO COMPLETE THE PROJECTWith the plans to terraform Mars, as proposed by the Mars Society, they are counting on everything going right for a thousand years to get to the point where you have an atmosphere suitable for trees.The humans still can't live there even with an oxygen supply. It turns out that carbon dioxide is a poison to us at concentrations above 10% in the atmosphere (not many know that, and I am not mixing up carbon monoxide with carbon dioxide). If the Apollo 13 hadn't found their duct tape McGyver type solution to the problems with their carbon dioxide scrubbers, this risked killing them all, dying in a carbon dioxide rich atmosphere, with plenty of oxygen sitll available.You can't live in a mixed CO2 / O2 atmosphere. They would need to use closed system air breathers like aqualungs rather than an oxygen mask.Then, there is not enough CO2 in the ice caps to do more than double the atmospheric pressure to under 2 millibars, far too little for humans to take off their full body spacesuits. So to go any further then they have to assume lots of CO2 in the form of dry ice mixed in with the soil to considerable depths - but there's no evidence either way about this yet.They usually suggest using greenhouse gases to warm it up to the point that the dry ice sublimates into the atmosphere. That's a big megatechnology project, 500 half gigawatt power stations according to one estimate, and mining cubic kilometers of fluorite ore on Mars per century to make the gases. That’s the ‘easy solution’. The harder solution is to use planet sized thin film mirrors in space to reflect extra sunlight on Mars.If this succeed, then a thousand years later, you end up with an atmosphere that only trees and plants can tolerate which is poisonous to humans. That is if everything breaks in your favour.GENERATING AN OXYGEN RICH ATMOSPHERE - IS IT 900 YEARS (ZUBRIN) OR 100,000 YEARS (MCKAY)?Then after that if you use photosynthesis it's around 100,000 years to pull all the carbon out of the atmosphere according to Chris McKay. Perhaps that can be speeded up, but somehow or other, you have to create a layer of meters thickness of organics averaged over the entire planet to get rid of the carbon.Zubrin is much more optimistic and he estimates, it could be accomplished as quickly as 900 years, with mega-engineering.His proposal is to first release one millibar of oxygen from the perchlorates which he estimates requires 2200 terrawatt years of power (that’s the equivalent of 20,000 half gigawatt power stations operating for 220 years). It’s a lot of power but he would use space mirrors, and assumes a 3,125 km radius space mirror focusing the power of the sun as the source of energy.After that he envisions higher plants genetically engineered with an efficiency of 1% spread over the planet. He doesn’t explain, but for this to work, for all that photosynthesis to be dedicated to increasing the oxygen content of the atmosphere - the plants have to be harvested and buried and more grown on top. For his objective, it’s no good just having them in a cycle returning the material to the atmosphere when they die, as that is just a seasonal oscillating cycle of more and then less oxygen.With this background he writes:“… they would represent an equivalent oxygen producing power source of about 200 TW. By combining the efforts of such biological systems with perhaps 90 TW of space based reflectors and 10 TW of installed power on the surface (terrestrial civilization today uses about 12 TW) the required 120 mb of oxygen needed to support humans and other advanced animals in the open could be produced in about 900 years. If more powerful artificial energy sources or still more efficient plants were engineered, then this schedule could be accelerated accordingly….”As he goes on to say, if we had easy access to fusion power we’d have far higher levels of power available which could change many things. But as it is now it’s a huge megatechnology project.Photosynthesis cools down the planet by removing carbon dioxide (a greenhouse gas of course). So now you have to step up your greenhouse gas production even more. You are committed to greenhouse gases or large thin film mirrors for as long as Mars remains habitable.An Earth atmosphere transferred to Mars would not be anything like Earth without artificial means - the water would all freeze and it would be too cold for trees even at the equator. That's simple physics, it is too far from the Sun for Earth's atmosphere to work there.Also plants on Mars will have to work three times as hard as on Earth to maintain the same level of oxygen, because in the low gravity you need three times the mass for the same atmospheric pressure. But they also have to do that with half the level of sunlight. This is why Chris McKay says it would take so long, 100,000 years, to generate an oxygen atmosphere there. On Earth in similar conditions it could happen in a sixth of the time.MAGNETIC SHIELD DOESN’T HELPThe idea of a giant magnetic shield got some publicity, but is just useful to protect the Mars atmosphere long term. It is not going to thicken it up in the near term. Even if you had Earth’s volcanic production of CO2 on Mars it would take around a million years to reach 6 millibars, which is the point at which they think a runaway effect could happen.Since Mars is only barely active with no current volcanism or even known hot spots or fumaroles, it would take a lot longer, perhaps into billions of years. This is more useful for helping to stabilize an atmosphere on the very long timescales. If you do succeed in terraforming, this could help ensure your terraformed atmosphere lasts for billions of years rather than millions of years. It is not so easy to create one this way.NITROGEN AND WATERFinally, an oxygen only atmosphere is a fire hazard so you have to add nitrogen as a buffer gas (it absorbs some of the heat from a fire and so acts as a fire retardant). Mars seems to be rather deficient in nitrogen. Perhaps its original atmospheric nitrogen is partly buried underground in nitrates beneath its northern sea? Nobody yet has a clear idea where to find it except to import it by hitting Mars with ammonia rich comets.There's enough ice in the polar caps for a few meters of water over the surface of Mars but that's assuming you have a Mars with no ice caps - how likely is that?Its ice caps are much smaller than Earth's and an Earth-like Mars would have larger ice caps, not smaller ones.Mars north pole ice cap - Composite of 1000 Viking Orbiter red- and violet-filter images (NASA / JPL / USGS) - got it from: When Humans Begin Colonizing Other Planets, Who Should Be in Charge?A terraformed Mars would still have ice caps, larger if anything. Terraformers hope that there are large supplies of ice in the southern uplands beneath the surface. Some of this at least has been found so there may be some reason for optimism, but how much is there?Also the equatorial regions are dry to considerable depth and any water would have to fill the desert sands to levels of hundreds of meters to kilometers before you have any on the surface.If you are optimistic you hypothesize enough ice from the earlier oceans trapped in the southern uplands to pour out onto the northern ocean area, and maybe even the ocean that used to cover the entire northern hemisphere is still there somewhere, trapped as ice underground.If you are pessimistic then nearly all that ice got lost to space as water vapour split by solar storms with the hydrogen escaping and the oxygen reacting with the surface of Mars and rusting it - or it ended up in the hydrosphere kilometers below the surface. After terraforming, unless you import ice from comets - at most you have a few flowing streams of water and a lake or two, in a still largely dry planet covered mostly in desert.NOT AN AUTOMATIC OUTCOMEAs well as that, supposing you do find all the water you need, it took hundreds of millions of years for Earth to develop a microbial biosphere supporting an oxygen rich atmosphere.But as well as that we don't know that Earth's present biosphere is the automatic outcome. There are probably thousands of possible ways that our planet could have gone, with a variety of ecosystems, and perhaps only a few of those habitable to humans. Some perhaps totally uninhabitable as a result of some runaway effect that tipped it out of habitability.And we are hoping to speed up those hundreds of millions of years into centuries. If it can be terraformed that quickly it can probably unterraform just as quickly.WASTEFUL OF RESOURCES - PLANETARY CHAUVINISMIt is just so incredibly wasteful of resources to try to terraform a planet. All that water, all that carbon dioxide, all the resources on Mars for habitability together with gathering thousands of comets too, probably, and smashing them into Mars in order to create 2-3 meters thickness of breathable air (we don't care about the rest) and all that water poured into the dry sands in order to have a tiny amount on the surface for habitability.This is why in the 1970s, many space settlement advocates turned their attention away from Mars and looked into space habitats. They calculated that you can do settlement far faster, more efficiently, more easily and with fewer resources if you built space habitats. And if you are doing that, you don't need to build them on a planetary surface.We may be planetary chauvinists because of our familiarity with living on a planet. Isaac Asimov explains here that he got the term "Planetary Chauvinism" from Carl Sagan. He can't say for sure that Carl Sagan invented it, but that was the first he heard of it. He talks about this 35 minutes into this video:Settlements in space provide much more living area than planets can, for much less investment of effort and much less use of resources. As he says in that interview, our future, for most of humanity, is likely to lie in space habitats rather than on the surface of planets. From his interview in that video:"I'm convinced that we will build space settlements in space, we will live inside small worlds, and we will eventually recognize that as the natural way to live. It is economical. You have just a relatively small amount of mass, and it is all used. In the case of the Earth, you've got an enormous mass, and almost all of it is not used. It's down deep where we can't get at it, and the only purpose is to supply enough mass to produce enough gravitational intensity to hold stuff onto the outside. And that's a waste! With the same mass you can build a trillion space stations carrying incredible numbers of people inside. And this is what we will eventually come to. I'm sure we will use the asteroid belt to build any number, thousands upon thousands, hundreds of thousands of space stations, which will eventually flee the solar system altogether."Isaac AsimovAnyway that's the idea. That planets are not where it is at for the future of space settlement. One calculation they did back then is that there are enough resources in the asteroid belt to build habitats for a thousand times the surface area of Mars (its surface area is also about the same as the land area of Earth).For any here who are unfamiliar with it, the idea of mining the asteroid belt is to turn the materials there into habitats that spin to create artificial gravity. This is an idea developed by many engineers and scientists in the 1970s including O'Neil and some scientists at Stanford university who drew up detailed engineering plans for how to do it. This has been rather forgotten recently with all the fanfare about Mars.It's not a case of living on Ceres. Nor is it a case of hollowing out an asteroid and spinning it and living inside it. It's a case of making a habitat out of asteroid materials and then spinning the habitat. And you can generate any level of gravity. Typically the design is to have a habitat under full Earth gravity because the designers assume that's best for human health. If a lower level of gravity is better they can just spin it more slowly. You could have a thousand times the land area of Mars as space habitats with Mars gravity if that was preferred. And you can have any level of sunlight you like and any length of day or night, using thin film mirrors to reflect the sunlight into the habitat, and then shades to simulate night and day.I discuss it in my Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand EarthsIf you do it that way you end up with a thousand terraformed planets in terms of living area, for much less by way of megatechnology than would be needed to attempt to 'terraform' a single planet Mars. You can do it faster too, far faster, with the first habitats completed in decades.And what's more, they can be customized to whatever gravity level you like. The atmosphere, temperature, ecology, all easily regulated and within your control.If this is not feasible, there is no way that terraforming Mars is feasible.I think myself that it is only after we have thoroughly mastered the art of making space settlements like that of a few cubic kilometers that we should even contemplate terraforming.These are my articles about it on my Science 2.0 blog:To Terraform Mars with Present Technology - Far into Realms of Magical Thinking - Opinion PieceTrouble With Terraforming MarsImagined Colours Of Future Mars - What Happens If We Treat A Planet As A Giant Petri Dish?MARSFORMING MARS - AND MARTIAN GAIA OR ANTI-GAIAPerhaps the problem with terraforming Mars is that we are fighting against Gaia? Perhaps that is why we would need all that technology?Gaia is the idea of James Lovelock that a planetary biosphere can be self maintaining and as conditions change it responds to stay in balance much as a microbe does - but on a vaster scale.This leads in to an idea for Mars by Chris McKay - if we find interesting Martian life on Mars, perhaps independently evolved, that we try to “turn back the clock” to create conditions hospitable to Mars life.Well if we do this, perhaps the answer is to set up an ecosystem with hydrogen sulfide as a major component of the atmosphere as this is a strong greenhouse gas. Or methane, or both.Perhaps early Mars had powerful greenhouse gases to keep it warm. Or perhaps it was habitable only briefly when its orbit is much more eccentric than it is now and with its axis optimally tilted to reduce the polar caps to a minimum. Whether or not that is how it did it originally - maybe we could set up an ecosystem like that today?So what if we make this the objective anyway, whether or not there is life there already? If we work with Mars rather than against it, find where the Mars climate “wants to go” rather than try to make it into a copy of Earth then it may be easier to achieve. We need to find what kind of ‘Gaia’ comes naturally to Mars. Then - rather than a pale shadow of Earth, Mars becomes whatever it is best suited to become. We help it to realize its own potential - which then may well also benefit us too.An Earth like ecosystem, without megatechnology, on Mars might even be a kind of “anti Gaia” (my own suggestion here, do let me know if you have seen someone else suggest it).Photosynthetic life would cool down the planet just as it does on Earth, by pulling carbon dioxide out of the atmosphere. But that is the opposite of what you want on Mars to maintain a Gaia like balance. It’s going to keep pushing the planet to colder conditions again as soon as it gets warm enough for life.That’s why we need all the artificial greenhouse gases and planetary sized mirrors in all the terraforming plans and why none of them can do it all using biology alone. It is too cold, not too hot, so a thermostat that ‘Gaia’ can use to cool it down when life flourishes, based on photosynthesis can’t work there.But perhaps some thermostat based on hydrogen sulfide producing bacteria can? Maybe biologists can think of a way this could work? That the cooler it gets the more hydrogen sulfide it produces? Anyone got any thoughts about how that could work? Or any other way to help it become self regulating?If we can't make it self regulating, it might need constant attention and megatechnology to keep it in balance, and as soon as we stop, then it reverts to its current state. So, to get a sustainable world warmed by greenhouse gases, we would need to establish something more, some form of 'Gaia' in the "weak Gaia" sense. We’d also need the magnetic shield on a very long timescale, otherwise any attempt at "Marsforming" it is going to make it even drier once the atmosphere is stripped by solar storms over long time periods.To be clear, I'm not suggesting we do this right now. But it may not be too soon to start thinking about it.PARATERRAFORMING THE MOON AS THE NATURAL STARTING POINTWe can do “paraterraforming” which is covering a body with habitats. The main disadvantage compared with free space settlements is that you have to use the local gravity and also work with the local levels of light.Mars has half the levels of sunlight you get on Earth, so photosynthesis has to work twice as hard or be supplemented by artificial light,It is occasionally blocked out for weeks on end during the dust storms, which go global every decade or so, sometimes more often.Compare this with the Moon:The Moon has plenty of sunlight and no dust storms.But a cycle of a night of 14 Earth days and a similarly long dayThough it has 24/7 sunlight close to year round in some favoured areas at the two poles.I suggest that the natural starting point is a habitat at the lunar poles, perhaps eventually even a city dome there. This is where ESA plan to build their "Lunar village" in collaboration with other space agencies, worldwide, and also many private companies. It's much more like a village than like the ISS with separate habitats sharing some common facilities. I think myself that it is perhaps the most exciting idea we've had for ages in the field of humans in space.After that, the best starting point is to paraterraform a lunar cave. These are known to exist and in the low lunar gravity they may be vast, kilometers in diameter and over 100 km long.The 14 Earth days long night is not such a drawback for the lunar caves as you might think. Modern LED lighting and especially the purple lights optimized to produce only the light needed for photosynthesis reduce the lighting you need a lot, to only a hundred watts per square meter.Remember that on Mars you have to supplement the low levels of light anyway if you want to grow crops that need a lot of sunlight (tropical plants) and you also have to be able to supply sunlight through weeks long global dust storms, unless you just stop all agriculture whenever that happens. It’s not much of an engineering difference if you do it for an unpredictable length of time of at least a few weeks every few years or you do it every 14 days. You still need some way to supply the power for 2 weeks, and in the case of Mars probably longer.You can grow just about all the food for one person and also provide all their oxygen from 30 square meters of crops, actually tested in the BIOS-3 experiments in Russia. Also, there are many crops that can withstand 14 days of darkness so long as you cool the roots during the lunar night, and continue to crop as normal with a double length growing season.So, the lunar caves are far more manageable than they seem at first. Also, the Moon has a major advantage that it is within easy access of Earth), has tourist potential, and it may have commercial potential (enthusiasts struggle to find commercial potential for Mars), and in one comparison after another it comes up better than Mars.I see lunar caves agriculture as involving LED lights mixed with some areas of crops that just go dark at night, and with light piped from the surface in the lunar day.There are many ways to store enough energy for the night. But longer term, then they are bound to have solar panels that are constantly in sunlight, as solar panels are easy to construct on the Moon. At any time one of those arrays will be in sunlight and the electricity transferred to settlements throughout the Moon using microwaves or else long distance power transmission using high voltage direct current which should be easy to do with cables laid over the lunar surface. They might well run alongside the lunar railways that take you around the Moon.This is a fair bit of engineering - large solar arrays, long distance HVDC cables, eventually city domes, lava tube cave settlements, and lunar railways, but it is nothing compared to what is needed to terraform a planet.Of course you can paraterraform Mars as well, live in lunar caves or build city domes. However Mars is by far the most vulnerable from Earth microbes of any place in the solar system, if you are interested in searching for extraterrestrial life.WHAT IS THE BUSINESS MODEL FOR MARS? OR THE MOON?Mars has also got many other disadvantages. For instance, when asked how his Mars colony is going to support itself commercially, Elon Musk talks about the half million dollar proceeds from the sale of the prospective colonists' homes on Earth as the main way to sustain the colony initially. See his interview on the SpaceX YouTube channel: What is the Business Model for Mars?But that can't last for long with the high cost of living on Mars, with spacesuits (currently st two million dollars each and good for a couple of dozen or so space walks from the ISS, also needing constant servicing). Even if they are reduced in cost ten fold, it's $200,000 each, and they will need to be repaired - and will need to be replaced from time to time. Then what about their habitats - you've sold your house on Earth but now you have to buy a much smaller and still far more expensive house on Mars. That also will need to have much of its equipment replaced from time to time and there will be many supplies you need from Earth.You have got to Mars, but you are planning to live there for the rest of your life and raise a family there too, presumably, or it is not really a colony. The half million proceeds from sale of your house on Earth isn't going to take you far. Some of it is gone on the ticket to get there, then you pay the $200,000 for your first Mars spaceesuit, and a deposit on the cost of your habitat - and what next?.He says a colony can't support itself by exports from Mars, and the only other source of income he suggests for the colony, apart from the sale of their houses on Earth is intellectual property rights - the income from their inventions and other IP that they export from Mars. Presumably the idea is that some of the billionaires there employ others, from their earnings from sales of their inventions on Earth, and so keep the colony going. But what's to stop a new billionaire who has invented something on Mars from just using their billions of dollars to return to Earth, which is where they may well want to be to keep a close eye on the manufacturing process anyway? Earth will seem like a paradise to them. And - wouldn't the colony need at least as much IP from Earth as it can export to Earth, no matter how inventive it is?Sorry, I just don't "get" their business model.Anyway, whether it would work or not, In one way after another, the Moon actually wins over Mars - I was surprised. There's a lot of work to be done, but at least on paper it seems promising. There are several enthusiastic space engineers, geologists and scientists who have written books with detailed working out of what seem to be practical economics for the Moon on paper, involving exports of platinum, or exports of ice from the lunar poles to LEO (if those are easily mined) or by setting up tourist hotels on the Moon and many other ideas.See for instance:The Value of the Moon by Paul SpudisMoonrush by Dennis WingoThe Moon: Resources, Future Development and Settlement by Madhu Thangavelu, David Schrunk, and many other contributing scientistsMuch of the material in these books is devoted to a detailed business case for the Moon.You just don't get this for Mars. The nearest I've seen is David Kuck's idea of the Deimos water company - and that could be feasible if Deimos does indeed have ice in it (as it might) - though if there is ice at the lunar poles, it's hard to compete (except for export to Mars itself, which can't work unless Mars has a business case).For exports from the Mars surface, just not much. Robert Zubrin talks mainly about the same idea of export of intellectual property. His deuterium export idea from his section on Interplanetary Commerce in “Case for Mars” page 239 chapter simply doesn't work, as it's only saving one step in a process that on Earth is done in bulk in 27,000 tons deuterium factory, the size of a skyscraper, and powered by a large hydro-electric scheme with an output of 128 MW. . Hard to compete with that on Mars. He has other speculative ideas there, but none of the details of the lunar ideas.It's far easier to export from the Moon because of the low delta v to get back to Earth. Then you also have the fixed distance, the short travel time there and back (especially for tourism), and that you can go there any day of the week, any month of any year. There's even the Hoyt cislunar tether system, which acts a bit like a siphon feeding a waterwheel - it takes materials from the surface of the Moon, and through two rotating orbital tethers, one in low lunar orbit and one in LEO, it transfers it to LEO, lower in the gravitational gradient of the Earth, and if you time things carefully with a net flow in the Moon - Earth direction it actually generates power instead of using power and fuel.For these and many other reasons, I suggest that the Moon is the best place to start with human settlement. But that's not the main focus here - I cover it in Case For Moon First: Gateway to Entire Solar System - Open Ended Exploration, Planetary Protection at its HeartWHAT ABOUT THE GRAVITY LEVELS?As for gravity levels - first nobody knows what is needed for health. We may even be healthier in lunar gravity. And - though there is no way to know for sure - at least it seems likely that after months or a year at lunar gravity it would be much easier to adapt to the Earth on returning home than if you spend the same time in zero g. Not likely that you are unable to stand at all and have to be taken off the spaceship in a stretcher until you adapt back to Earth gravity as happens for many astronauts who spend a long time in zero g.But if we do need more gravity then we may well need it for only a short time per day, e.g. while exercising, or eating or sleeping which we could do spinning for artificial gravity.Spinning is much better tolerated in zero g than on Earth with astronauts able to tumble end over end without any feeling of nausea or dizziness and this might be the case for the Moon too. It’s a conflict between the otoliths that sense linear acceleration and the vestibular system that senses spinning that makes us feel nauseous while spinning and in zero g the otoliths are not stimulated so there is no conflict. At least that was the hypothesis that Skylab researchers thought most likely to explain this observation.LOWEST MAINTENANCE HABITATS AND HABITATS WITH LEAST OUTLAYAny space habitat requires some level of constant maintenance. If just the airlocks and the spacesuits, as the inhabitants do have to be able to get out of it occasionally, however maintenance free it is inside.However, remember, so does a terraformed Mars with constant production of the greenhouse gases or maintenance of the planet sized mirrors to reflect more sunlight onto it. If you do succeed in terraforming it, then on the surface it may seem an easy place to live but you are dependent on a lot of technology working “behind the scenes” to keep it going long term.There are also many Biogeochemical cycles you need to complete, carbon cycle, nitrogen cycle, oxygen cycle, phosphorous cycle etc and those won’t necessarily work automatically as they do on Earth. It might be a constant on-going challenge to keep its ecology on track and stop it “unterraforming” - if you succeed in terraforming in the first place.It is also a very long term commitment. In the middle ages there were some projects to complete cathedrals on a timescale of centuries. But this far exceeds any of those projects. It’s like the inhabitants of the Lascaux caves starting a project that would take so long that we’d still be at the early stages of it 17,000 years later.Any civilization that can contemplate such immensely long timescales has to be very mature. I think that a civilization that takes on a terraforming project with confidence of success, and of seeing it through to completion would probably be at least thousands of years old, and more likely millions of years old. It’s probably completed many centuries and millennia long projects before it tries this one.Even houses on Earth of course take time to build, and need maintenance. However, Earth is the only place though where humans can survive without any technology at all, like the gorillas, in at least some places. And with minimum technology we can survive anywhere from the Kalahari desert to the Arctic (San people, to Inuit).There are some places outside of Earth where we can live with minimal technology, though nowhere we can live without any at all, not anywhere that we know of. Titan’s surface has an atmospheric pressure actually greater than Earth’s. You need thermal insulation, and you need an Earth atmosphere inside your habitat, but you do not need to hold in the internal pressure. Habitats on Titan could be any shape and be lightweight flimsy things like houses on Earth, indeed flimsier and easier to construct in the lower gravity (apart from any artificial gravity requirements if you need spinning for AG for health).The Venus cloud colonies are similarly lightweight and also arguably low tech. These float just above the clouds at the level where the temperature and pressure is similar to that on Earth. It needs the technology of an airship + sulfuric acid resistance. But the acid protection is only for the outer skin of a large habitat. Arguably acid resistance is easier to engineer for than holding in Earth’s atmospheric pressure against a vacuum - and is far less mass at least, just a thin layer of teflon or similar.When it comes to paraterraforming or the large spinning habitats in space, then as for the Venus cloud colonies what matters is how easy it is to maintain the outer skin.If you think about it that way, then perhaps the lava tube caves are strong contenders too. Most of the mass is already there - in the form of the lava tube itself. Perhaps you just need to fill in cracks and make it impervious to air. If so, the launch mass from Earth could be very low, lower even than a cloud city or Titan dwelling.If you can make any of the big structures nearly maintenance free and within it you have an Earth normal atmosphere, it might well end up being lower maintenance than e.g. living on Titan without a city dome . Once it is built, that is. If it is exceptionally low maintenance it could be easier than living on a house on Earth.However nowhere in space can be lower maintenance than living in a tropical jungle on Earth, unless you find a way to make the maintenance totally automated with robotic machinery (as is the case in many science fiction stories).Note - large spinning habitats do not need any form of propulsion to keep spinning. Maintenance, and the level of technology needed to live in such a habitat would be similar to a city dome, or a lava tube cave.That’s just the external structure. The internal ecology is likely to require constant monitoring and “gardening”. But that again is the same for a planet.Only a very mature civilization would have confidence that the ecology of their terraformed planet could continue long term without constant vigilance and monitoring, and then correction of issues as they arise, I think. And it would probably gain that confidence at least in part through working with larger and large enclosed habitats, starting with much smaller scale closed cycle ecosystems of up to a few cubic kilometers, and gradually gaining confidence through those experiences and also through study of exoplanets.That is, unless, of course, we make contact somehow with a mature ETI that has solved these problems already, long ago. Even then, their solutions may need adaptation to terrestrial biology.WHAT ABOUT ELON MUSK’S “NUKES TO TERRAFORM MARS”This was just an off the cuff joking remark he made. He talks about it here at 2 minutes in to this video, where he called it a “fixer upper of a planet”. He says is“There’s a fast way and a slow way… The fast way is to drop thermonuclear weapons on the poles":He gave no details yet it was taken up in many news stories. presented half seriously as a way to terraform Mars. This was not based on any research, just an off the cuff joking remark by a CEO of a space company. It was soon followed by other news stories by the more techy and geeky journalists saying it was impossible to do it that way.Could his remark he based it on that idea that if you liberate enough dry ice, you could kick start the runaway greenhouse? But there isn’t enough dry ice at the Martian poles anyway to reach the magic 6 mbar to start a runaway greenhouse, at most you could double the current 0.6 mbar. Then, the number of nuclear bombs you’d need if there would involve a vast megaproject, hardly an “easy” solution. You are talking here about hundreds of thousands of hydrogen bombs as powerful as the 50 megaton Tsar Bomba - the largest nuclear bomb ever tested.This was my article about his idea, in response to those many journalist stories:Why Nukes Can't Terraform Mars - Pack Less Punch Than A Comet CollisionWhen asked for clarification he later explained he meant constantly exploding nuclear fusion bombs to form two “mini suns” above both the lunar poles. Rather a science fiction scenario. See Elon Musk Clarifies His Plan to "Nuke Mars".Probably many of you saw this as the screen saver as you wait for a SpaceX video to start - it doesn't give any timescale however.As far as I know they are focused on space engineering and are not actively researching into terraforming. They leave that to the likes of the Mars society and keen scientists who are researching into it anyway.WHAT ABOUT KIM STANLEY ROBINSON’S ‘THE MARS TRILOGY’This is a series of three books, Red, Green and Blue Mars that came out in the mid 1990s together with a book of short stories with the history as backdrop called “The Martians”. In this he envisions Mars terraformed and developing a planet spanning civilization in a couple of centuries. The main focus is on social issues but he has a backdrop of terraforming with plausible sounding science, and this has influenced many people to think that terraforming Mars would be easy and accomplished as soon as a couple of centuries. See Mars trilogy - WikipediaThe Martians coverKim Stanley Robinson himself says that it would take far longer than his trilogy suggests, which is based on 1980s ideas. In a podcast he gives as his main pointsMars seems to have lost its nitrogen. We need nitrogenThere could be life in the basement regolith a hundred meters or a kilometer underground and that’s going to be very hard to disprove. So we may be intruding on alien life.Its surface is covered by perchlorates, poisonous to humans in the parts per billion. They could be changed into something more benign to humans, by introducing something to eat them, but that would take time.The best analogy is Antarctica - beautiful, scientifically interesting, and for Mars, especially of interest for comparative planetology - going to Mars is a way to study EarthMars trilogy is a kind of allegory of people on Earth. We have over 7 billion people and may end up with 9 or 10 billion. There is no way we can use Mars as an escape valve in less than thousands of years.He was following Carl Sagan - and Martin Fox who suggested thousands of thermonuclear bombs so deep they heat up the planet. Then you introduce genomes from Earth.He thinks terraforming is for later - once we have a sustainable civilization on Earth and proved we will not wreck this one, we can then consider the next great project.He does not think that Mars is in the same relation to Earth as the New World is to the Old World. The New World wasn't really a pioneering colonization anyway as the first people were there already. Also, Mars is not habitable without terraforming, with thousands of years needed to terraform. All of this make the analogy not applicable in his view. It’s not going to be a solution in decades. He says he has a profound disagreement with Robert Zubrin on the New World analogy, and says that this is not what Mars is about.He says that we can’t use Mars as a ‘backup planet’. We have to fix our problems on Earth to have any hope of surviving on the timescales of the book. See the podcast here and summary on Io9 here hereThere are many other issues with his book though, if you consider it as science rather than science fiction:He assumes that the humans can be genetically engineered to tolerate carbon dioxide instead of nitrogen in the atmosphere - supposedly by using crocodilian hemoglobin then humans become able to tolerate high levels of CO2 as well as becoming nearly immortalHe greatly accelerates the timescales, e. g. the effects of photosynthesis, a hundred fold or a thousand fold.He doesn’t explain how Mars is kept warm with a CO2 / O2 atmosphereHis Mohole wouldn’t work - he fudges the numbers and there is no serious scientific paper suggesting use of moholes to terraform Mars. He proposes to warm the atmosphere of an entire planet using a number of large radiators at a temperature of 50 C or so..They are typically one kilometer in diameter, let's call the area one square kilometer. There are ten of them, so call that ten square kilometers. With this he proposes to warm up a planet with a surface area of 144.8 million km². The atmosphere is in thermal equilibrium with the surface - so he has to warm up at least the top few millimeters of the regolith, not just the atmosphere. I'm not sure how to do the detailed calculations to see what temperature difference there would be, but it's going to be minute.His windmills idea is plain silly for a physicist - I know it's meant as a deception to illegally spread algae - but how could it deceive the other scientists in his plot line?The wind is going to be slowed down anyway. Slowing it down prematurely using windmills is just a way of concentrating the energy dissipated by slowing it down into a single place on the surface. So there would be no net heat input into the atmosphere as a result of the windmills. It would only make a difference if the atmosphere was moving as an ideal fluid without friction.Fun scientific quibble for geeks,: this is a simplification. Actually, as Lee Weinstein (mechanical engineer and energy researcher at MIT) wrote in his blog post "Windmills on Mars", there would be a very minute, but temporary, warming effect. By slowing down the winds with the windmills, this reduces the kinetic energy of the Mars atmosphere due to wind, and by conservation of energy, this has to mean a slight increase in the temperature of Mars. However this is just a temporary effect while they reduce the speed of the wind. Once the average speed of the wind has reached a new, lower, equilibrium, then Mars returns to thermal equilibirum witth the rest of the universe. So there would be a really tiny increase in temperature for a short while after the windmills are deployed, after which the temperature resturns to normal. When you stop the windmills, the opposite happens, it cools down then returns to normal.You could use the same argument for the moholes. The temperature of Mars can only increase temporarily as a result, because no heat is being created. The heat from the interior is just being lost more quickly at that point. The rest of the crust of Mars must be getting slightly less heat radiated through it, so eventually this is going to cause Mars to cool down slightly elsewhere, by tiny immeasurable amounts but probably only on long timescales.The physicist Raymond Pierrehumbert, specialist in climates of Earth Earth, planets in our solar system and exoplanet atmospheres puts it like this in his article "Science Fiction Atmospheres":"Robinson has certainly set up the puzzle correctly, but the physics behind many of the solutions his characters propose is silly. Silliest of all are the windmills, which are supposed to heat the planet by using wind-generated electricity to drive heating coils. (I won’t insult the reader’s intelligence by spelling out why this wouldn’t work.) One could argue that the windmills were really just a ruse for illegally dis- persing Mars-adapted algae, but it’s more than a little implausible that all the high-powered physicists among the Mars colonists would be taken in. There is other silliness. Polar caps are dissipated by albedo-reducing algae, and water vapor is added to the atmosphere by cometary impacts and ”mo-holes” without regard to the constraints imposed by Clausius-Clapeyron."On the other hand, there are some interesting and workable ideas in Robinson’s book. There is a space mirror to catch sunlight and turn Martian night into day, but to bring Martian insolation up to Earth levels would require a mirror with a cross sectional area equal to Mars itself; still, a more modest mirror with 10% of the Martian cross-section could make a useful contribution. The question of the microclimate of low-lying areas like the Hellas Basin, where surface pressure will be greatest, bears thinking about, as does the circulation one would get around the rim of the basin. It would be rather like Death Valley (how jolly!) or a drained Mediterranean, only more so. If it were up to me, I’d make some use of algae bio-engineered to release HFC’s, and perhaps also synthetic cloud particles optimized to reflect infrared while letting through a lot of sunlight"All of this is acceptable in a science fiction book written for entertainment, especially given that he says his main aim was to reflect on conditions on Earth. But it is not a scientific blueprint for terraforming Mars, and was surely never intended as such.On the issue of intruding on alien life on Mars, then there are many suggestions now for habitats not just at the base of the regolith, but on the surface or in the top cm or so of the soil as well. There is an almost bewildering variety of possible habitats for surface, near surface and subsurface life. None confirmed but many to be investigated. Here are some of them - the links take you to the section of my online Touch Mars? book.Nilton Renno's droplets that form where salt touches ice - why did he call a droplet of salty water on Mars "a swimming pool for a bacteria"?Recurring Slope LineaeLichens and cyanobacteria able to take in water vapour directly from the 100% night time humidity of the Mars atmosphereLiquid brines beneath the surface of sand dunes at night - beneath the sand that Curiosity drives over - that one was reported as uninhabitable but Nilton Renno was not so sure, biofilms might make it habitableTransgressing sand dunes bioreactorDesert varnishSun warmed dust grains embedded in iceSouthern hemisphere flow-like features - these may involve fresh water!Methane plumes on Mars and the possibility of water deep below the surface in its hydrospherePorous basaltTwo ways Curiosity's methane spikes could be generated in the shallow subsurface (centimeters deep at most)Ice covered lakes habitable for thousands of years after large impactsIce covered lakes from volcanic activityPossibility of geological hot spots in present day MarsLife in ice towers hiding volcanic ventsAlso see Modern Mars Habitability in Wikipedia (one of my contributions to the encyclopedia)NATIVE MARS LIFE IS NOT NECESSARILY SAFE FOR US OUR ANIMALS OR CROPSThe terraforming plans assume that there is nothing on Mars that can harm us already. If there is - or some ancient microbe is activated as a result of the terraforming - there is nothing to say it has to be safe for us or our animals or crops. They do not have to be adapted to us to harm us. Indeed microbes normally become less harmful when they adapt to humans, and may eventually become symbionts.For instance legionnaire’s disease infects amoebas and biofilms. It uses the same mechanism to attack the lungs of humans. So a disease of Martian biofilms could easily attack human lungs too.Microbes can also harm us indirectly through producing a toxin. Examples include botulism, ergot disease, tetanus, and aspergilliosis (a fungus that can cause allergic reactions such as asthma and can be fatal to people with damaged immune system). None of these are adapted to us.For another example that is plausible for some alien biochemistry, Alzheimer's disease may perhaps be caused by cyanobacteria which produce a mimic BMAA for an amino acid L-serine that is not exactly the same and gets misincorporated in the proteins of our body. This is ongoing research - but it highlights something that could easily happen in response to an alien biology with similar but not identical chemicals to those used by Earth biology.Similarly some algae blooms that form in Lake Eyrie in the States to kill cows. There is no evolutionary advantage - cows are not their natural “prey”. It’s just a coincidence. The same could happen with Mars life and ourselves. For more on all this see this study, lead by David Warmflash of the NASA Johnson Space Center: Assessing the biohazard potential of putative martian organisms for exploration class human space missions and see the section Many microbes harmful to humans are not "keyed to their hosts" in my online book.LONG TERM SPACE SETTLEMENT IN FREE SPACE HABITATSI think one way or another we are likely to find a way to be able to live in large habitats on the Moon. But if not, we have the large habitats in free space, such as the Stanford Torus. They can be positioned anywhere in the solar system and have whatever gravity levels you want and with thin film mirrors, as much sunlight as you want whenever you want it. I think they are the natural end point for space settlement myself.You could make a habitat like this using materials mined from a small 300 meter diameter NEO such as 4660 Nereus4660 Nereus, 300 meters diameter, NEO, easier to get to than the Moon, has more than enough material for the cosmic radiation shielding (main part of the mass) for an entire Stanford Torus with 10,000 inhabitants.Long before you have the capability for terraforming, or can have got even a fraction of the way towards terraforming your first planet, if you ever do succeed at it, you have the capability for these free space habitats.FREE SPACE HABITATS CAN FILL THE ENTIRE SOLAR SYSTEM TO BEYOND PLUTO - AND GALAXY PROTECTIONOnce you have them, just by using larger and larger thin film mirrors to concentrate the sunlight, you can live anywhere in the solar system right out to well beyond Pluto. The mass for larger thin film mirrors will be only a small fraction of the mass of the habitat.It's a case of do it once, colonize the entire solar system. Indeed it would become so easy to colonize that I am concerned about the effect it could have on the galaxy and wonder how we will achieve galaxy protection, a long way into the future that is at present. See my draft article: Galaxy Protection Solutions to Fermi's Paradox - No Need to be Scared of 'Great Filter' - I'm working on that one at present and plan to post it in my blog here in the near future. I have a long section on Galaxy Planetary Protection in my Touch Mars? book and it's based on that. SeeTravel to other starsPlanetary protection for other stars and exoplanetsGalaxy protection - what about colonizing other star systems?I think we will find a way through it though and if so, well then we could end up with a solar system with trillions upon trillions of humans living sustainably if we so wish.And such a civilization would be immune to anything. When the sun goes red giant - just move the habitats further out. Or reduce the size of the thin film mirrors reflecting sunlight into the habitats for the already distant settlements.I cover the lunar gardening in detail in myAn Astronaut Gardener On The Moon - Summits Of Sunlight And Vast Lunar Caves In Low GravityI cover the asteroid habitats in myAsteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand EarthsMy original motivation for exploring alternatives to Mars was for reasons of planetary protection. For someone keen on humans in space but also keen on science and interested in the possibility of finding life based on a different biology, it would be tragic to make life on Mars extinct in our eagerness to send humans there.But I then realized that the Moon is greatly favoured anyway and that Mars is not the natural next place for humans that it seems to be at first.You can read my Touch Mars? book free online here:Touch Mars? Europa? Enceladus? Or a tale of Missteps? (equivalent to 1938 printed pages in a single web page, takes a while to load) also available on Amazon kindleThe other ones areCase For Moon First: Gateway to Entire Solar System - Open Ended Exploration, Planetary Protection at its Heart - and on kindleMOON FIRST Why Humans on Mars Right Now Are Bad for Science - and on kindle.This includes my An astronaut gardener on the Moon>

Ok, here are some tips and tricks for someone contemplating the jump to electric power. Just stuff I have managed to pick up over the 4 years we have had no use for gasoline. Yea, it’s long, I expect to make a faq out of it someday. (Edit to add even more details)Some basics.You should choose a car with a range at least 50% longer than your round trip daily commute. Makes sure you can run some errands, or it’s real cold or hot, and you have the heat or AC on full blast, etc. This isn’t hard to find these days, since the average US driver does 13,000 miles a year, or less than 40 a day, and even the cheap, small battery models have 130 or more mile range.You should have a place for daily charging. For almost all of us, that’s at home in our driveway or garage. For apartment dwellers, or on street parkers, this could be at the office. If you don’t have either option it is possible to get by with public charging, but it is annoying. This should be solved eventually, around here apartment buildings are adding chargers, even including them in the amenities listed on the “now leasing” banner.Some cities, and an entire Canadian province have required all new residential construction to be charger ready, (an open space in the breaker panel, and a wire good for 50 amps pulled to a parking space). For cities, there are some schemes under test that add charging points to streetlights, another that adds it to parking meters.You don’t need a garage to charge in. You can safely plug in the charging cable even in driving rain. You could drop the cord into the puddle you are standing in, and not get shocked. (I wouldn’t, but the system is designed to cope). Basically when you grab the plug, off the hanger, there is only low voltage in the cable. Only after the box determines that the plug is fully seated in an actual car, and that you let go of the latching button, will you hear the clunk that is line voltage getting applied to the cable.I admit that charging when it’s snowing is annoying. When you are finished charging, you may need to dig snow out from around the socket in order to close the flap, and if you drop the plug, the end is deeply recessed, and can pack full of snow.Ok, some details on charging.First, there are chargers built into the car. There is a box hanging on the wall, or built into a kiosk. That actually isn’t a charger, it’s actually the safety system alluded to above. It’s official name is an EVSE They have two jobs, tell the car how big a fuse they are connected to, and to turn on the power when it’s safe to do so. It’s the chargers job to only draw the amount of power the box says to.The chargers built into the car vary in size, and are rated in kw. Typical sizes are 3kw on a few base models, and on plug in hybrids, 6 and 7.2 kw on the mid priced. The standard Tesla has a 10kw charger, there is an option for the model S to have a second one installed. To calculate an approximate from empty charge time, divide the battery capacity by the charger size. So your 30 kWh Leaf with its 6 kw charger, takes 5 hours. My 24 kWh eGolf with its 7.2 kw charger takes 3.4 hours. That P85D Tesla will need 8.5 hours.EVSE come in 3 strengths.Level 1 is an ordinary wall outlet. The cord comes with the car. It can add 5 miles of range for each hour you are plugged in. If you are in Europe, your outlets charge 2.5 times faster than ours. I used to carry an extension cord, I don’t bother any more.Level 2 is a dryer or electric stove amount of power. It will have you charging at speeds between 25 and 40 miles an hour. Most public charging kiosks are at this level. All cars sold will be able to use them. If you have a Tesla, it will come with an adapter. These will refill an empty battery (unless huge) in under 8 hours. If you need or want one for home, they start at $300, the cost of getting power to them will vary depending on what needs to be done, but figure $250 at the low end, with 5–600 more typical. You can even buy an open source board and controller for $100 that will let you make your own. Some places will insist the box be hard wired (especially if you mount it outside), others allow outlets. A few of the cords that come with the car will also work with a stove circuit, or other versions of 220 volt outlets, with adapters. The Tesla cord can do this, and comes with the adapter for stove circuits.The standard plug on level 1 and 2 chargers is the J-1772. All cars can be charged with one. Tesla uses its own plug, but includes an adapter. There are a few Tesla specific level 2 chargers in the wild, Tesla had a program that would supply them to hotels. There isn’t an adapter to use Tesla specific chargers on other cars (that I know of). The J-1772 includes a latch. Some cars can use this to lock the plug in place, requiring you to have the key fob to disconnect. We live down the street from a middle school. I am sure a 5th grader passing by would consider unplugging the car to be a funny and most original prank. (Our driveway is very short, Our chargers cable is bright orange, it’s not subtle). Our car came with a lock.Level 3 is what you will be using to top up on a long trip. They are very. fast, with speeds ranging from a low of 100 mph, to a high over 600 mph. They are a lot more expensive than a level 2, and even the mere 100 mph version is $10,000, and it takes as much power as your whole house. 100 amps, 240 volts. The rest want the sort of voltage and current that you might find at a smaller manufacturing plant. They can be hard on your batteries, as keeping them in balance at those speeds is difficult.Of course there are annoying complications. There are three different plugs for high speed connections, Japanese, the rest of the world, and Tesla. A public charger will usually support both of the public standards, and Tesla chargers are their own world. If you find one at a car dealer, it will only support a single standard, whatever that brand supports. You find them next to interstates, and most have food or at least coffee available. Tesla has a 5 year head start on building their network, and has the fastest chargers for now.On some cars the ability to use a level 3 charger is standard, others make it optional, or dependent on which trim level you purchase. A few models don’t have it, even as an option. If you are even just thinking you might want to take a longer trip someday, and it’s optional, get it. We have only used fast charging a few times, but it made the difference between a routine dinner stop, and a delay.To tell them apart, or tell if your car is equipped to use one, if it is a Tesla, it uses the same plug as their slower chargers. In the case of a Leaf, the Chademo standard uses a completely separate and noticeably larger plug, the socket is next to the normal plug under the door. In the rest of the cars, SAE/CCS is two additional pins just outside of , and at the bottom of the standard J-1772 socket. Most have a cover over the pins when not in use.The best way to find chargers is Plugshare (phone app or web page). It’s crowdsourced, so it shows all chargers no matter who is providing them. It also assigns a rating to them, showing how often you could actually charge, or that you always find them ICEed, (conventional car parked) or a victim of their own popularity and with someone already plugged in. It can filter out chargers that don’t apply to your car, and it has a system for people to offer up their home charger to a passing traveler in need. One thing really in its favor, they include detailed directions on where the thing is located.If your average daily mileage is under 40, you can do pretty well with just overnight wall outlet charging. It will use less than $1 in electricity to do this. We ordered a level 2 charger when we bought our car, but it was more than a year before I installed it. Remember, since you can easily plug in every day, your charging time will reflect how far you drove, not how long it takes from empty.Tip: if you are renting the place, and park in a spot next to the house, look around for an outlet on the outside (the one they plug hedge clippers into) and buy a heavy duty extension cord. When my brother bought his Volt, until he got around to installing an outdoor outlet, they ran an extension cord out a window. In my case, it took me close to a year to get around to wiring and mounting the charger, and the outlet on the front of the house served.Check with your power company. In some places they offer a plan with off peak pricing, so your evening fill up will be half or more off. The car and possibly the charger will have timers that will make it easy to delay charging for when rates are cheap.If you are staying at a campground, the RV hookup will be an electric stove outlet, that will run a level 2. At a farm? Do they have a welder in the barn? The voltages are correct, but the outlet is an older 3 pin sort, rather than the modern stove plug that level 2 chargers use. Adapters aren’t hard to make, and you might be able to buy one at a place that has RV supplies. (For the roll your own sorts, welders use 6–50 plugs and sockets, stoves use 14–50)Wintertime. Batteries don’t work as well when very cold. Some cars will warm the batteries to an optimal temperature if you are plugged into the grid. The other problem is heat. A gas powered car throws away 75% or more of the energy in the fuel, as heat out the tailpipe and radiator. It doesn’t change your gas mileage to divert some of it from the radiator in front, to one inside the cabin.In an EV, 90% of the energy goes toward motion, which doesn’t leave enough to warm the cabin with. So to get a warm cabin you have to spend some of the energy in the battery. There are two ways this happens, using the air conditioning “backwards” as a heat pump, or by using the same sort of resistive heater that you aren’t supposed to have under your desk at the office. The heat pump is the more efficient system. Both do have the advantage that warm air happens quickly, no waiting for an engine to warm up.There is another way, that is great in cool but not frigid weather. You want the heated seats. They will keep you comfortably warm when it’s 40F out, without affecting range.One thing about heating and air conditioning in an EV that will make conventional car owners jealous, the car has timers that can start the heat, air conditioning or the defroster, and if plugged in, they will use grid power for this. You go out in the morning, and the car will be already warm, and the windshield clear. You get back to the car that has spent all day in the August sun, and when you open the door, you aren’t hit with the waves of heat that feel like you are standing in front of a blast furnace. You can sit down, wearing shorts, and the back of your thighs won’t get branded with the upholstery’s stitching pattern. A number of them have the ability to also turn on the heat, etc. from a phone app. When the meeting finally is winding up, you poke the phone, and the car starts whirring all by itself.One other weather related thing: the batteries can freeze. If it gets below -20F -27C, and stays there for days, the batteries can freeze. Supposedly they aren’t harmed by this, as long as you don’t try to charge them. Just move the car into a warmer space, and let them thaw. The manufacturers build a heater into the pack, to prevent this. If connected to outside power, it will keep them safe, till mud season. If it isn’t plugged in, it will use the batteries themselves. Even a small pack will keep them safe for more than a week. So if you live in someplace like frostbite falls, or Barrow, be sure to plug it in when you leave it for a few days. Wall outlets are more than sufficient.Range anxiety and charging times, the usual elephants in the room. You get over it. Most of us charge at home, while we are sleeping. As far as we are concerned the car takes 30 seconds or less a day to charge, 10 seconds to plug in, 20 to unplug and hang the cord up. It’s like charging your phone, you don’t know how long it takes, you just plug it in before bed, and it’s full when you wake up.The real change in outlook happens after a month or so. Imagine there were pixies that came around every night, and topped up your tank. Every day you get in, and the “tank” is always full, you just stop worrying about range or charging. Gone is the arriving late to something, because you forgot to stop the night before, and had to make an unplanned pit stop on the way. (Or your teenaged kid borrowed it last night, and left it a needles width above empty.) And no more making a side trip, and spending 10 minutes in the rain, heat or cold, pumping fuel. If it’s alwas full in the morning, often would you think about your gas gauge? Would you really choose filling up yourself.Now I get range anxiety when I wind up driving a conventional car. Refueling requires a conscious effort, I have to notice that I need some, and figure out where I can get it. (if I am driving a gas car, it means that it is a rental, I got off a plane, and I am in an unfamiliar city). After a while driving electric, you will stop noticing gas stations, and won’t know what a gallon of the stuff costs anymore. The last habit to go, seeing a station, and glancing at the “gas” gauge.We have never sat around waiting for a charge. Even when we made trips further than a full charge would take us. Yes it took a bit of planning, it was long enough ago that high speed chargers were still limited in availability. We just picked a high speed charger at a shopping mall next to the interstate , and had dinner while it charged. It finished charging before we finished eating.Right now the only time you will make use of a high speed charger, is on a trip that today would have you buying gas more than once in one day. You may even not need it for trips where you fill up two days in a row. (You pick a hotel that has level 2 charging available, and the car is full by the time you finish breakfast)One reading of the name of the Japanese high speed standard (Chademo) is vaguely “a cup of tea”. The implication is that you would stop, brew a cup of tea, and drink. The car would be mostly recharged, and you could continue.If you are the sort of driver that packs sandwiches to eat on the way, and tells the kids “if you aren’t back from the bathroom by the time I am done filling the tank, we’re leaving you here”, using an EV will make your trip take longer.For a more typical trip to the in-laws, you pull into the rest area, find an open charger, wave your phone or RFID card at the box bolted to the concrete pad, and plug in. In the time it takes to herd the kids thru the toilet, wait in line for to-go at deathburger, get back to the car, and get them strapped back in, a good charger will have added enough range to drive for 3 hours, or about mean time to meltdown for siblings under 10. If you are being all adult, and actually sit down for a meal that is brought to you and you don’t have to unwrap before eating, you will get the charge complete text before you get the check.Time to finish charging isn’t linear. As the pack gets full, they slow the charging down so the batteries don’t overheat. If it takes X time to charge to 50%, going from 50 to 75% might take that long again. And the last 25% might take 3X to spoon in.What this means is on long trips, is that you start thinking like a transport pilot, you take on only enough fuel to get you to your next stop plus a reserve. In EV terms, it means you try to stay on the fast end of the curve, and you don’t stick around for the battery to fully charge. Pick the charger 3/4ths of the way, instead of half way, so you are down to 10%. Then if by leaving with only 60% you will get there with 30 miles range in reserve, you leave then rather than wait as long again for 80%. If you have a Tesla, the navigation system will actually do the calculations for you, saying you need to stop at charger Q for at least 12 minutes to reach your destination.One last comment on range. High speeds on the highway make a more noticeable difference with EV than with a conventional car. Since other losses are low, aerodynamic drags contribution is more prominent. A long way of saying you will get a lot further at 65 than you will at 85.Other random things….Check your tire pressure. If it’s low, rolling restance takes a disproportionate jump, and I have found that the warning system wants you to be 20% low before it lights up. I have a compressor at home, so I just check them on the first Saturday of the month. (Unless it’s raining or snowing). A tire delays the airs escape, it can’t keep it confined forever. Plus when the temperatures drop, so does the pressure in your tire.Regenerative braking. This is where the car starts to recharge the battery as a way of slowing down. It will happen when you hit the brakes, it’s why the brake pads last so long. On an EV you can also get it to happen by just lifting your foot off the accelerator. On some cars it is the default, on others you have to tell the car you want it. it’s wonderful, it reminds me of engine braking with a manual transmission. I really notice its absence when I get back into an IC car. You can drive in city traffic, just using the accelerator. You only hit the brake pedal when you need to hold on a hill.Parking lots. Pedestrians walk 3 abreast down the middle of the lane, unless they hear an engine behind them. Engine noise, and they go single file at the edge of the lane. We learned this 20 years ago driving hybrids. Just a heads up, so it doesn’t surprise you.Since the horn is overkill in this situation, some cars come with a “growler” fake engine noise that comes on automatically below 10 mph or so, to warn people. At one point it was going to be required, don’t know if it happened. Our car is so equipped, even tho it wasn’t required that year.I find it annoying, I like the silent glide. At least it shuts up when you are stopped. I suppose I wouldn’t mind it so much if I got a choice of sounds. (A poll was taken on the VW EV forum, some of the nominees included Italian V12, Mack truck, big V8, air cooled VW, Harley, turbo 4 cylinder with blowoff noise, and a chainsaw, but the winner was the noise that the Jetsons cartoon flying car made). One solution for cars sans growler, that some proposed was to briefly turn on the air conditioning, as the compressor makes a similar noise to an engine. A wag on the Chevy Volt forum said “my car has a pedestrian warning system, 4 of them, they were made by Goodyear”. Apparently the factory low rolling resistance tires weren’t the quietest.Adressing some of the other “facts” that are routinely brought up by people that haven’t been in the same zip code as an EV.“Your electricity comes from coal, it pollutes more than a gas engine….” A couple of “facts”. with this one.. First, because EV are so energy efficient, the equivalent of over 100 mpg in a gas car, even if you had 100% coal fired electricity, (true in some parts of West Virginia, near the coal fields) it would still result in less pollution than a normal car.The second point, coal is only 30% of US generation, and dropping as fast as the utilities can get their hands on the hardware to convert to combined cycle natural gas, which halves the fuel costs, and carbon footprint. Predictions say that coal firing will essentially end by 2030. Some places like the New England states, it’s already gone. Carbon neutral generation is at 31% nationwide, last I checked, And any new generation built these days will be a renewable source. A lot more solar, especially household arrays, and for utility scale the current cheapest per kWh to construct and operate are wind turbines. (And that includes the generators that burn stuff) So your car is green already, and it gets greener without you doing anything. A gas burner doesn’t get better with time. (And you can make your car very green quickly if you have the ability to buy your power from carbon neutral sources only).“They are all slow”. This one is best dispelled by stuffing them in the passenger seat and demontrating. If a P100D is available, it should take under 3 seconds to convince them, but even more modest examples should suffice. Besides the torque curve everyone mentions, they don’t have a flywheel. It was an old rule of thumb with the drag racing crowd, that taking a pound off the flywheel was like taking a hundred pounds off the car.“The batteries only last 3–5 years, and cost more than the car is worth to replace”. We don’t know yet how long a set of batteries will last, we haven’t been using them long enough to wear many of them out. A car owner doesn’t have that much to worry about, the EPA requires that the batteries be warranted for 8 years/80,000 miles, if you live in a state that adopted CARB rules, the warranty jumps to 10 years/150,000 miles. As they are emissions equipment, they are transferable.Ok, some actual data instead of speculation. Some brands collect data from their cars when they are in for regularly scheduled inspections (there is essentially no regular maintenance on an EV) To get down to 70% of original capacity looks like it will take nearly 20 years. Faster in hot climates, slower in more temperate ones. There are already some cars running around with more than 250,000 miles on their original batteries. Should a pack loose enough capacity to be not useful for transportation, they can be rebuilt, which thanks to volume lowering battery prices, will be fairly cheap to do. Yes the first few years of the Leaf did have a battery life issue, they had air cooled packs, and didn’t use a particularly heat tolerant battery chemistry, the LA crowd did have issues with reduced capacity. After the outcry, Nissan switched to what got nicknamed “lizard” batteries. The companies that water cooled their packs didn’t have a problem.“But toxic batteries in the landfill”. First, most (but not all) aren’t toxic waste. The stuff inside is harmless should it wind up in the trash, and is legal to toss into a landfill. But landing in the trash is just Not going to happen, for a number of reasons. First, they are on a car. We do an excellent job with cars, something like 98% of them get recycled when they are dead. What that means is that if a battery is part of a car, it will not get dumped.The batteries are excellent candidates for recycling, they come in a handy easily isolated container, they are marked as to what chemistry they use, the metals inside are valuable, some as much as $10/lb, and there could be a half a ton of them.But most of them won’t get recycled, instead they will get reused. Space and weight are limited on a car, so you want the batteries at their best. But transportation isn’t the only thing that wants mass quantities of batteries, and some are a bit less fussy. Stationary power banks to pick the most likely. People and utilities use them to even out load on a power system. You have a fine solar array, but your peak demand is at 6 PM, nearly sunset. So you take a bunch of these batteries. You get them cheap because they are reclaimed. So you have to use 25% more of them, they are less than half the price of new, space under the array isn’t being used for anything else, it’s a little big, so what.Yes this is already happening. The junkyard owners learned long ago that there is real money at the end of those fat orange wires. When a car with a traction battery gets dragged into the yard, it is immediately stuck up on a stand, and they drop the battery out first thing. They are by their standards gentle, (wrenches not torches, and they won’t let it fall more than a couple of inches. They might even include a pallet to cushion the landing, and not just the unadorned forklift blades), and they move it to a shelf indoors.The owner knows there is a ready market, and its not just owners of that make. If you damage it, he will be pissed. (If the secret junkyard cabal finds out that a yard owner sold scrap for less than they could have gotten, they will swoop in, switch the office coffee for decaf, the donuts for bran muffins, and replace their pit bull with an equal weight of toy poodles, yorkies, and other tiny yapping breeds)The people buying the packs are doing or updating an EV conversion, rebuilding traction batteries, some live off grid, and are building a storage facility for their solar array, etc. GM has contracted with a third party to buy the batteries that are replaced under the emissions system warranty. The off grid folks are particularly keen customers. Lithium is a whole lot lighter than lead. So a pack of lithium cells while a bit more complicated to build, is a whole lot easier on your back than half the capacity of deep cycle lead acid. Even better you don’t have to make weekly rounds with the distilled water, checking that they aren’t low.The motorhead community has been wrong about battery life before. When we bought a hybrid the same short life was predicted. Well for those we actually can speak from experience. We bought a Prius in 2000. 14.5 years later, it was facing repairs to the internal combustion side of things that had a parts cost greater than the current value. As part of the decision that led to us trading it in, I checked the health of the original, unmolested, traction battery. It was just over 90% of its original capacity, and the cell to cell balance was good. The hybrid, where I know the owner, with the highest mileage was a first US generation Prius with 350,000 miles on it when a teen ran a stop sign and T boned it. There are reports of ones in taxi service with double that on the original pack.I think the reputation for short EV battery life is from the early homebrew lead acid conversions. Use of any sort of cell level battery balancing was unheard of. Charging could best be described as having a bit of a brute force approach. They didn’t limit discharge depth, which unchecked actually leads to some cells getting a reverse charge, when they hit 0 before their neighbors. All combine to leave them with a very weakened battery.If you have a lithium pack, you must have an active battery management system, especially since you the manufacturer are on the hook for 8 years.“But but they catch fire…. We read about that one in the news”. Yea, you don’t here much about regular cars catching fire. That’s because it happens so often, that it isn’t news. Try 171,500 times a year or about every 3 minutes in the US alone. Once a day, the event is fatal. 4 times a day someone is injured enough to need treatment. The fires only get reported if the car belonged to someone prominent, or it happened someplace that it was particularly disruptive, like a tunnel. Conventional cars have many ways that collision or parts failure can set things alight.There are two things that can get a lithium pack to self ignite, mechanical damage, and incompetent battery management. Those hoverboards that got recalled were because they did the battery management wrong. Every cell did have a protection chip, but they used the ones designed for a single cell, and not the ones with the extra circuits to deal with multiple cells in series.Mechanical damage fires start more slowly, than a fuel fire, the batteries smolder and vent smoke for a while before flames happen. You have more time to get away. And the battery fire doesn’t spread anywhere near as fast as you will see with a gas tank leaking it’s contents downhill.Remember, in most gas powered cars, the bottom of the fuel tank is at or at times below the floor pan. Random obstacles on the road can tear them open. Some are even made of rotary molded plastic. While some metal gas tanks are sturdy, a lot of them will collect a substantial dent if an adult were to jump up, and land on them with both feet.I helped a friend that bought a wrecked Leaf for its battery pack, to salvage the cells for some electric motorcycles he had built. The battery comes in a very sturdy can, that is mounted under the floor. Yes if you jumped and hit the center, it would deflect. At an edge or the corner, not so much. They are pretty well protected. Tesla goes one better, armoring the bottom and front edge with a substantial titanium plate. They also fill the space between the cells with a fire extinguishing gel.But cars can set themselves alight in other ways, ones that don’t even require a collision as a trigger. Conventional cars have fuel running 10 feet or more from the tank to the engine, in a steel tube at the bottom of the car. In fuel injected cars, this line is pressurized to 4 bar (50–60 psi) by a pump in the tank. At various places, there are sections of rubber hose connecting things.There is a guy on YouTube that rebuilds salvage vehicles, and records the process. He just finished recovering a Lamborghini that had a cracked fitting lead to a fire when refueling. He just started on a Ferrari where a rubber line rubbed against the worm drive hose clamp securing its neighbor, wore through, and sprayed the engine compartment with 50 psi fuel, and the exhaust manifold made certain that the failure of that cheap bit of hose did terminal amounts of damage. (The channel is Tavarish if you want to check it out)Last one, I promise.“Look at the damage mining the materials for the batteries makes” this is always accompanied by a distant view of a large open pit mine, or a detail view of excavation machines working on the ramp sides typical of open pit mining. This is a clear attempt at disinformation. Neither photo is a lithium mine. The distant view has been identified as a Russian copper mine. No identification on the close view that I have seen, but what they are mining appears to be coal or oil shale.A lithium mine and refinery looks like a bunch of man made shallow ponds, in the middle of an alkaline salt flat. It makes things a lot easier when what you want to extract is water soluble. If you have flown over the southern edge of the bay south of San Francisco, you would have seen some rectangular ponds that are somewhat unusual colors. This is a “mine” for sea salt. They just use sun and wind to evaporate the water, and the salt eventually crystallizes out.If you flew over a lithium mine, the ponds would look similar, but surrounded by the white sand of the desert, instead of the ocean. The primary source for lithium is the Atacama desert high in the Andes mountains. It is one of the most inhospitable places on the planet. Nothing lives there. It hasn’t rained there in recorded history. They used it to test the signs of life instruments used in Martian exploration.Anyhow you “mine” lithium, by rinsing the alkaline sand, leaving cleaner sand and some brine. You pump the brine into the ponds. After a while the lithium will crystallize on the surface, and you skim it off. Further refining is done electrically.