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Mars

Attention Mars Explorers: Besides Low-Gravity, There's Also Radiation (scientificamerican.com) 212

The director of astrobiology at Columbia University saw something this week that he just had to respond to: Elon Musk "talking about sending 1 million people to Mars by 2050, using no less than three Starship launches per day (with a stash of 1,000 of these massive spacecraft on call)."

A reader shared this article from Scientific American: The martian radiation environment is a problem for human explorers that cannot be overstated... For reasons unclear to me, this tends to get pushed aside compared to other questions to do with Mars's atmosphere (akin to sitting 30km [18.6 miles] above Earth with no oxygen), temperatures, natural resources (water), nasty surface chemistry (perchlorates), and lower surface gravitational acceleration (1/3rd that on Earth). But we actually have rather good data on the radiation situation on Mars (and in transit to Mars) from the Radiation Assessment Detector (RAD) that has been riding along with the Curiosity rover since its launch from Earth.

The bottom line is that the extremely thin atmosphere on Mars, and the absence of a strong global magnetic field, result in a complex and potent particle radiation environment. There are lower energy solar wind particles (like protons and helium nuclei) and much higher energy cosmic ray particles crashing into Mars all the time. The cosmic rays, for example, also generate substantial secondary radiation -- crunching into martian regolith to a depth of several meters before hitting an atomic nucleus in the soil and producing gamma-rays and neutron radation... [I]f we consider just the dose on Mars, the rate of exposure averaged over one Earth year is just over 20 times that of the maximum allowed for a Department of Energy radiation worker in the US (based off of annual exposure)....

[Y]ou'd need to put a few meters of regolith above you, or live in some deep caves and lava tubes to dodge the worst of the radiation. And then there are risks not to do with cancer that we're only just beginning to learn about. Specifically, there is evidence that neurological function is particularly sensitive to radiation exposure, and there is the question of our essential microbiome and how it copes with long-term, persistent radiation damage. Finally, as Hassler et al. discuss, the "flavor" (for want of a better word) of the radiation environment on Mars is simply unlike that on Earth, not just measured by extremes but by its make up, comprising different components than on Earth's surface.

To put all of this another way: in the worst case scenario (which may or may not be a realistic extrapolation) there's a chance you'd end up dead or stupid on Mars. Or both.

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Attention Mars Explorers: Besides Low-Gravity, There's Also Radiation

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  • So what? (Score:5, Funny)

    by msauve ( 701917 ) on Sunday January 26, 2020 @12:41AM (#59656928)
    " there's a chance you'd end up dead or stupid on Mars."

    Everyone on Earth is going to end up dead, and you're stupid to think otherwise.
    • This "what" (Score:4, Insightful)

      by Jzanu ( 668651 ) on Sunday January 26, 2020 @01:16AM (#59656942)
      For every single reason discussed it is instead the orbits around earth, the land of Antarctica, and even a simple supply depot on the moon that are infinitely more valuable for humanity in every case than every single one of the Mars colonization fantasies. If you don't understand then you don't even know enough to read this article. Brush up on your chemistry, biology, physics, and medicine. Then read the damn article.
      • Re:This "what" (Score:4, Insightful)

        by rmdingler ( 1955220 ) on Sunday January 26, 2020 @08:35AM (#59657374) Journal

        For every single reason discussed it is instead the orbits around earth, the land of Antarctica, and even a simple supply depot on the moon that are infinitely more valuable for humanity in every case than every single one of the Mars colonization fantasies.

        You're absolutely correct.

        Yet, a failed Martian colonization mission would be a better use of human time, energy, and even life, than what the 99% are likely to accomplish in an earthly lifetime.

      • Supply depot on the moon is abject cartoon silliness.

        Brush up on your... physics

        Please. Please.

    • So, what, we should just stop caring? Give up? Party until we drop dead? Or just start the Apocalypse because why not?
      I really don't get people like you.
      • by Dunbal ( 464142 ) *
        I, for one, would like to see more effort at exploring the moons of Jupiter and Saturn...
  • Kurzgesagt (Score:5, Interesting)

    by Brulath ( 2765381 ) on Sunday January 26, 2020 @12:51AM (#59656934)

    Kurzgesagt made a video on this topic a year ago which I found interesting:

    Building a Marsbase is a Horrible Idea: Let’s do it! [youtube.com]

    It seems that living on mars wouldn't be particularly fun, but building the technology required to do so would be worthwhile.

    • Re: Kurzgesagt (Score:4, Interesting)

      by samkass ( 174571 ) on Sunday January 26, 2020 @02:57AM (#59657008) Homepage Journal

      I donâ(TM)t think itâ(TM)s coincidence that Musks big companies produce rockets, solar panels, electric vehicles, boring machines, and is exploring low-atmosphere tube transport. Iâ(TM)m just surprised Musk hasnâ(TM)t started a water filtration company.

      • Maybe he's waiting for someone else to get results so he can buy them. Isn't that what companies do?
        • How well did that work out for Microsoft when Google was growing?

          For that matter, how well did that work out for IBM when Microsoft was the small, cool kid on the block?

      • Comment removed based on user account deletion
  • I've been wondering off and on for a few years now if it would be possible to generate a sufficient artificial magnetic field to be of any worthwhile level of protection for a Mars (or Moon) base.
    I know we have the technology to generate extremely powerful magnetic fields, (abet for short periods). I have no idea how powerful a field would be needed to be worthwhile, but it is an interesting question.
    • by plopez ( 54068 )

      looks like micro teslas. https://en.wikipedia.org/wiki/... [wikipedia.org]

      How would you power this field

    • Sounds like a fun question for the "What If?" section over on xkcd... Planet-wide: NO. Around a small habitat: maaayyybe. Would probably require a lot of power, supercooled magnets or similar trickery that either wouldn't be technically feasible, or ridiculously expensive to put in place.

      But even then: magnetic fields divert charged particles. Like some of what's in the solar wind. But not EM radiation like gamma or cosmic rays (on Earth, our much thicker atmosphere helps there). So you'd still need the

      • by Dunbal ( 464142 ) *
        Much much easier just to build underground. No power required once digging is complete. No chance of failure resulting in catastrophic radiation while you wait for spare parts from Earth, don't have to deal with extreme temperature swings between day and night as the changes would be more moderate, etc.
      • He's not an expert. His "What if"s are notoriously bad and one-sided and only looking scientific to people even less clueful than him. They exist only because of Munroe's obsession with with a "can't do" attitude and running down ALL the ideas, in order to feel smug about himself.

        I used to like xkcd when it was still harmless and joyful.
        But his smugness and condescending passive insulting of everything that looks less clueful than him ... be it because it actually is, or because it looks like that to cluele

        • by Megane ( 129182 )

          His smug condescension reached my limit a little over three years ago when he made a blatantly political xkcd. I wouldn't even have cared if he hadn't given it a main sequence number. I vaguely recall that it wasn't even on the regular schedule. I suppose I'll check later this year to see how his smugness is getting along. I can't remember seeing anyone reference his newer stuff, so maybe it was just as well. Anyhow, never mix art and politics, it's a good way to piss off half your audience, one way or anot

      • Protecting against the solar wind seems feasible [phys.org] at least. This won't stop cosmic rays, but deflecting the solar wind would reduce the stripping away or Mars atmosphere, so that it would be partially restored. And that in turn would provide better protection against those cosmic rays.
      • The vast majority (99% or more) of cosmic rays are protons and alpha particles, both of which are charged. Gamma rays are fairly rare, and also relatively easy to block (they don't produce a huge shower of penetrating secondaries like protons and alpha particles). That said, we don't really have the technology to create the large-scale magnetic fields we'd need to create an effective shield.

    • I'd be worried about living my life inside the rough equivalent of a MRI machine, never mind the electricity bill. But a couple of meters or rock will do the trick, and the best thing? That rock is already there. Maybe some pre-drilled tunnels already exist (lava tubes) but to be realistic, better count on sending up a couple of boring machines, or scoping out some per-existing overhangs. Real life cavemen! Oh, the glamour.

      • Especially apparent in countries woth real brick and mortar houses.

        So I find it silly to act as if living in a natural cave would be any more primitive.
        My student apartment also used to ony have one side with daylight, and was essentially a tube with drywall separations for the kitchen, closet and bathroom. It still was nice, with paint and curtains and carpet and furniture and a nudist girlfriend and such. :)

        • You're on to something. Send only hot babes and toyboys and nobody will give a crap about going outside.

      • Real life cavemen!

        Someone needs to do a cartoon about human evolution, with neanderthals living in caves at the beginning, and modern day humans living in caves on Mars at the end.

    • by Sique ( 173459 )
      One of the least solvable problems on Mars is the low gravity. It boils down to the situation where Marsians will never be able to return to Earth as they are unable to survive the high gravity there. Basicly the moment you settle permanently on Mars, Homo sapiens will split into two subspecies Homo sapiens terrans and Homo sapiens martians which will no longer be able to live side by side.
      • Gravitation of 0.4g solves a lot more problems than it creates. It will simplify habitat design and construction, most especially, which is how you address the radiation problem for those living on the planet. Instead of forking the human species, colonists will probably opt for sending all pregnant women to Earth for an extended maternity leave, coming back when the child has reached some medically specified age.

        The radiation problem is going to be for those in transit, rather than for those on Mars. It wi

        • by Sique ( 173459 )
          I guess that most families will not do that. They are families because they want to live together. They don't want to split for several years. I guess, confronted with the immediate problem, most people will opt for staying on Mars, doing their business there, living on Earth be damned.
    • You don't need any of that to produce magnetic fields. Just hire Jean-Michel Jarre.

  • So you must spend your life indoors, shielded by a meter or two of martian rock, what's the big deal? Every time you feel like whining about not being able to go outside to play, think about Stephen Hawking. He couldn't go out and play, right here on earth, and he had a good life. Basically it comes down to what your purpose is. If you must spend your life on the beach then don't go, it's that simple.

    • What are you talking about? Hawking was always able to go out and play - he was superficially healthy until around the time he started college, and even after being confined to a wheelchair he was still able to go outside whenever he wanted, and play just as well as he could indoors.

      I also really doubt you could find anyone who would choose his path voluntarily. Just because humans are able to adapt to almost anything, doesn't mean it's "a good life"

    • The article indicates that you don't have to spend all your life indoors, though. It says that the exposure on Mars in an Earth year is 20x what's allowed for radiation workers. All you have to do, then, is limit your time on the surface to an average of an hour and 12 minutes per day. You can do a full 8 hour surface exploration trip once a week if you like. Colony supplies are likely to limit you to that anyway.

  • I have heard that the main reason that Mars has very little atmosphere is because the solar wind strips it away in the absence of a magnetic field. There seems to be an assumption that we will one day terraform Mars. However, even if we could create a new atmosphere (which we can't), wouldn't the solar wind just strip it away again?

    • Re: (Score:3, Informative)

      It's a matter of timescale. If it were possible to generate a useful new atmosphere for Mars, it would survive at least millions of years without being dramatically eroded by solar wind. So as far as our species (let alone our civilization) is concerned, it's not something to worry about. After we're gone, if someone else wants to remake the atmosphere again to their desired specs, it'll be up to them.

      • by Dunbal ( 464142 ) * on Sunday January 26, 2020 @04:00AM (#59657066)
        Too bad it would take at least a million years to create such an atmosphere. A whole planet's worth of atmosphere is one hell of a lot of gas. How many liters per minute do you plan on generating?
        • How many liters per minute are generated by life on Earth? I've heard biologists claim they could do the job in centuries, if not decades.

          Vaporizing the ice caps would go a long way towards kick-starting the process (say, via nuclear bombardment, giant orbital mirrors, or better yet, bombarding them with giant snowballs from the asteroid belt to further increase the total mass) - the combined size of the polar ice caps during their respective summers is around 3.2 million cubic km of ice, or 3.2e6km^3 * (1

          • How much energy and materials is required to build and transport giant orbital mirrors to Mars? How much energy would be lost due to the ice reflecting it back out into space? If nukes are used instead, then how much material from Earth needs to be transported, and is there enough of it? After nuking Mars, what will be able to live there? How long before the radiation levels drop low enough? And if crashing asteroids into Mars, the same questions come up. How much energy is required? Where is it coming from
            • Well, you can get a 3m^2 space blanket from REI that masses 85g (https://www.rei.com/product/407104/space-emergency-blanket). That would be 28 metric tons per square km (probably a lot more than that, since solar mirror material doesn't need to be nearly as durable as camping equipment) , So you could fit at least 3.5 km^2 worth into a single Starship launch from Earth.

              Except that you'd have to be pretty stupid to be shipping it from Earth. Terraforming is an incredibly ambitious long-term project - we ca

          • by Dunbal ( 464142 ) *

            I've heard people talk a load of shit, too. It's really easy to say "vaporize the icecaps". But you said it yourself - it's 3.2 million cubic km. How many joules do you think you're going to need? Plus you'd have to vaporize it all at once to get some sort of "greenhouse effect" going, otherwise the tiny bit you vaporized is just going to re-freeze and settle again. As for harvesting the asteroid belt to bombard Mars - exactly how many asteroids do you think you'll need, and how much fuel do you think this

    • even if we could create a new atmosphere (which we can't), wouldn't the solar wind just strip it away again?
      Yes we can.
      It would last several 100 million years.

      And there are ideas to have a huge magnet between the Sun and Mars at Mars L1 point. That alone might regenerate the atmosphere already to a certain level.

  • Why would you send people many millions of miles away to live in the bottom of a gravity well which is inhospitable to life, when you could instead build habitats in microgravity orbiting the Earth to your own exact needs/specifications?

    • You're at least as vulnerable in orbit as you are on a planet, even if it's in different ways.
      • And kiss goodbye all those cool science fiction space mega-habitats like giant donut wheels and giant cylinders, at least without airlocks every 100 feet to deal with catastrophic assholery.

        No gorgeous interior Grand Canyon-sized Garden of Eden vistas for you!

    • a) Adventure
      b) Bordom
      c) courage

      r) resources

      I have not enough fantasy to fill all out at the moment :D

      On Mars the resources are right there, for habitats you need to shoot up everything.

    • by Megane ( 129182 )
      To be fair, I recall reading that they really need lunar resources to build them; it's just not feasible to haul that much stuff up from Earth. So let's get lunar production going first, then we can see some cylinders happen. (Note that Mars is its own thing; there's very little that can be done with the Moon to help with getting to Mars beyond learning about the effects of partial gravity on the human body.)
    • Because
      1) we don't have anywhere near the orbital industrial capacity we'd need to do that yet.
      2) Such things are crazy fragile, and pretty much require that you build them inside hollowed out asteroids for shielding from radiation and meteor impacts (see 1)
      3) We don't have any such asteroids in Earth orbit, and it's probably a really bad idea to bring such massive ready-made kinetic warheads into place until we've resolved a few other geo-political problems. Especially since they'll need constant station

  • I am well into middle-middle-age now, but I could have sworn that years ago the general theory of any Earth-like planet would need a very big moon orbiting very closely (probably big & close enough to be tidal-locked, just like ours is) because the moon was the source of churning the Earth's iron core, that caused the magnetic poles, that shielded Earth's surface from lots of rather-not-healthy space radiation. There was no other theoretical force within a planet that would cause anywhere near as strong
    • Actually most of the planets have magnetic fields, arising from different phenomena. Mercury and Earth are the only two that generate a field based on moving molten metal cores (and Mercury's is mostly gone now). Jupiter has an intense magnetic field (10X Earth) that is actually problematic, because it traps so much radiation that orbiting the planet is dangerous (for both us and our space probes). Venus doesn't have a magnetic field, but its ionosphere does the same job at protecting the surface from the s

    • by gtall ( 79522 )

      The moon does more than that for the Earth, it stabilizes its rotation so that it doesn't vary. That evens out temperatures among other effects.

    • but I could have sworn that years ago the general theory of any Earth-like planet would need a very big moon orbiting very closely (probably big & close enough to be tidal-locked, just like ours is) That never was a theory, it is only uttered in "popular science" magazines.
      because the moon was the source of churning the Earth's iron core, that caused the magnetic poles,
      That is nonsense. The earth is rotating, that generates the magnetic field.

      • The iron in the mantle swirling around in giant convection loops generates the Earth's magnetic field. And it is molten because of nuclear fission in the material in there and the long time it takes to radiate the heat up and out of the planet.

  • Fact of the matter is: we have no idea whether or not humans can take up permanent residence on other worlds or not, and we won't know until someone tries it.
    Living on the ISS doesn't really count, even though at least one person spent more than a year in orbit -- but remember that even anyone who stayed in orbit for extended perioids of time suffered physiological effects. Living even on the Moon for years or permanently, let alone Mars? We have no idea and won't until someone tries it.
    I'd like it if we
    • by Megane ( 129182 )

      even though at least one person spent more than a year in orbit

      Yes, and since then it was learned that sufficient exercise, and of the right type, really does help. The real problem will be children; it's one thing for an Earth-born adult to go into space, it's another thing to be in space while your body is still growing, and also you likely won't have the maturity to understand the importance of exercise.

  • SCHOTT makes radiation shielding glass, which provide
    excellent protection against gamma and X-rays.

    https://www.us.schott.com/arch... [schott.com]

    • Hmm. Schott glass is basically lead glass (SiO2 and PbO). Autonomous factories on Mars would need to locate, mine, refine the necessary materials. This'd require tons of energy. Additional energy and materials would be needed to bootstrap the factories themselves (probaby mostly polymer materials, though some metal refining would also be necessary). We just don't have the necessary energy to spare for all of this (we have about 200 years of nuclear fuel left [scientificamerican.com]). If we did, wouldn't we rather terraform Earth's

      • by Megane ( 129182 ) on Sunday January 26, 2020 @09:09AM (#59657422)

        We have plenty of nuclear fuel left. We just use it very inefficiently right now. So sure, we only have about 200 years of fuel left, if we keep using nothing but enriched Uranium reactors. Why do we use that particular process? Because it's the one that provides the easiest path to make nuclear bombs! Then after that one single isotope of Uranium is used up, we call what's left "waste" and try to bury it, instead of using up the remaining 98% of its potential energy. And we don't even try to do anything with Thorium, so it gets counted as zero years out of that 200.

        That's like all the doom predictions about oil production, according to the predictions of 30 years ago, we should have passed peak oil long ago. The reason we didn't was because all the predictions completely ignored oil that wasn't feasible 30 years ago and would come online as prices increased and technology improved, such as shale fracking.

        Also, Scientific American went hard left almost 20 years ago. That's when I permanently stopped subscribing. I was not surprised a few years later when the editor was on Charlie Rose and basically admitted to the change in direction. So it's not surprising that they would go for the click-bait doom articles.

    • Domes are wasteful and impractical. They take a lot of materials for space you're not using, and they are difficult to anchor. It makes more sense to build rectangular structures which are essentially like an air mattress, which are also easier to compartmentalize as a hedge against depressurization. Domes look cool in movies, but they make no sense on Mars.

      • Domes are wasteful and impractical.

        Wrong.

        They take a lot of materials for space you're not using

        Why do you think that? Have you ever lived in a dome?

        There does not have to be "wasted space", you can partition a dome into rooms and different levels. You can use portions of the slanted side walls as storage.

        As for taking a "lot of materials" they are way more efficient than a traditional building and more structurally sound. I wonder if on a remote planet people might want a structure that is more, or less

        • "Also why do you think anything is easier to anchor than a dome? A dome is also much more resistant to anything you are trying to "anchor" to protect against"

          You have to anchor against the pressure from inside. Domes are good at resisting pressure from outside, not inside. HTH

      • Actually there are good structural and material reasons for domes - they're an optimal engineering shape for both pressure containment and load distribution - bridges aren't arched for aesthetics, but because that's the optimal shape to carry the load with the fewest materials. A dome is the three-dimensional extension of the same principle, which is why the ends of pressure tanks are always domed. They (nearly) minimize the amount of structural material needed to enclose a given (ground) surface area wor

        • You don't need internal support columns on Mars, you need anchor points. The internal pressure will hold up the structure as long as it weighs less than ten to fifteen pounds per square inch, depending on your chosen pressure. But having to have all of the anchor points around the circumference is a liability. And you can't easily subdivide it as a hedge against decompression.

  • after landing in MuskyShipOne:

    "We look for things. Things that make us go."

  • I'd rather live on a planet that was made just for me. -The puddle
  • After sending a million people to Mars, haven't you put so much shit in Earth's atmosphere that the people who stay there have at least severe problems?

    • No, every single day we have 2.7 million flight passengers.

    • Well, CO2 is really the only problem - Starship burns natural gas, which is about the cleanest fuel on the planet, producing only CO2 and water as exhaust products.

      Starship has a 100t capacity to orbit, call it 1428 average-mass people at 70kg each. Or 100 people with 14 people worth of additional supplies each.
      Total fuel for the Starship+Superheavy = 1200t+3300t, or 45t per person (with cargo).
      1t of methane produces 2.75t of CO2 when burned
      So launching each person (with their 14 people worth of cargo) wou

  • Send all the stupid people to Mars! Then it does not matter whether they turn dead or even more stupid. Of course, that requires a bit more effort than the 3 launches per day that Musk is planning.

  • by stabiesoft ( 733417 ) on Sunday January 26, 2020 @10:11AM (#59657508) Homepage
    that many are comparing going to mars like when Spain sailed to the new world. And when they did, they found it was good and settled there. But of course the elephants in the room are. There were already people living there. There was water to drink, berries to eat, oxygen to breathe, and fuel to keep warm with. Even with all that, they still had colonies that starved because they could not grow enough food. Here is the key though, once they established, it was easy peasy. Because well, there was water to drink, land with fertile soil, oxygen to breathe. What is mars missing? Water to drink, fertile soil, oxygen to breathe. And one the settlers never worried about, radiation to fry. We are at least decades and possibly centuries away from easy peasy mars/moon development. Go ahead and send some explorers wanting to die, but to believe Joe Shmoe is going to settle on mars to mine martian goodies next year, nuts.
  • Instead of selecting future astronauts from people with a "normal" length, the space organizations should imo select from the group of people with a (much) shorter than average length. The smaller the astronaut, the more effective the use of resources and available space in a habitat of spacecraft. And shorter humans have a smaller surface so the collected radiation is less too. Maybe someday being small is an advantage for high-demand jobs like space business, hell, maybe humans start to breed for smalle
  • You know that Cohaagen's gonna protect us with cheap domes. And no air to screen out the rays.
  • by phaserbanks ( 1977290 ) on Sunday January 26, 2020 @11:21AM (#59657676)

    Cosmic rays wreak havoc on transistors, and space-qualified electronics are orders of magnitude more expensive than terrestrial. Anything electronic on the Mars surface is going to cost a fortune, if you want any semblance of reliable functionality.

    • Drag some old-school engineers from retirement homes. The people who knew how to make a pressure sensor control a valve without needing an arduino in between.

  • by Slicker ( 102588 ) on Sunday January 26, 2020 @11:59AM (#59657746)

    I have yet to see a proposal for a martian habitat that doesn't include radiation shielding. It is certainly not a neglected risk. Also, the gravity is 38% that of Earth -- that's closer to 40% than 1/3rd. The toxic chemistry in the regolith (perchlorates) are just salt -- an oxygen rich salt. There are also about 2 liters of water ice per cubic meter of regolith. It takes between 3 to 5 washings of Earth soil to remove enough salt for farming purposes. In regolith, it should take far less. And the perchlorates will be very useful for making food tasty and for making rocket fuels, welding, etc.

    Cosmic rays and solar flare radiation are hard to shield against but you don't need 100% shielding. Actually 3 feet of regolith is often recommended, as it can fully block the radiation from an atomic bomb. Some measure of radiation is arguably good for you. It even helps add telomeres to DNA, slow down aging. Furthermore below 3 feet (roughly a meter), temperatures stay at the annual average of the surface temperature (on Earth). This is because most forms of radiation stop between 2 and 3 feet (depending on composition). Three feet of water (or water ice) will block 100% of dangerous space radiation.

    It is true that the secondary radiation from cosmic rays can be more deadly than cosmic rays themselves but that is only when hitting heavy metals, like lead. Actually today, polymers and water are more recommended for space radiation shielding than heavy metals like lead.

    Given a strong energy source, it should be reasonably straight forward to mass produce large amounts of polyvinyl chloride (PVC plastic) from the plentiful salts, water, and CO2. This would be perfect for habitats underground, overground, etc. It holds pressure exceptionally well, insulates exceptionally well, and does not burn (sustain a flame) unless excessive oxygen is provided (far more than the 21% we have on Earth). Versions of PVC itself have been suggested for building space faring vessels for its temperature, chemical, UV, electrical, fire resistance in addition to its shielding of space radiation.

    Another easy idea is to build dwellings inside Martian glaciers. Mars is dotted with glacier ice typically more than 2 kilometers deep ringing the planet just north and just south of the equator. Also, the regolith over it tends to be very thin (2 centimeters to around 2 feet or so). Placing an airlock on top, and melting out a palace below would be easy and practical. Ice caves can be warmer than freezing because the coolness deeper behind the walls keeps the walls themselves from melting beyond a certian point. That point can be higher, depending on the size of the ice cave. Bigger cave, higher temperatures tolerable without melting. About 70F is very reasonable in 8 foot diameter round ice cave (the floor could be flat). This is very akin to a lava tube. For gardening, I would suggest a foam membrane to line the walls such that 80F temperature could be obtained. Obviously, you are going to use LED plant lights and aquaponics.

    Now that I mentioned lava tubes, we should also mention those. The article made one brief mention of them. I twice visited a lava tube on Jeju-Do Island, Korea. It's about 30 feet wide -- round except for a flat floor. It's quite cool inside, even when burning hot summer outside -- again, the average annual surface temperature persists below 3 feet underground. Mars has many lava tubes visible from satellites and the sizes look to be more typically 120 meters or so -- (about 360 feet wide). You can definitely build cities in them. They are also a very likely place to find water ice reservoirs. The problem is that the obvious ways in are skylights (hole broken in the tops) that are like very wide and very deep. They will not be easy to access that way. If we can found the outflow points, which are very hard to spot from satellite images, then we could likely just walk in.

    Some years back, I investigated the idea of building inflatable wall segments to seal of

  • I would posit that if you're on freaking Mars, you're already stupid. The radiation would put these people into a coma.

Ocean: A body of water occupying about two-thirds of a world made for man -- who has no gills. -- Ambrose Bierce

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