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This topic has probably already been covered in the past, but if colonists are going to set up domes how could you block cosmic rays with such thin material and how will you protect the dome against micro-meteorites that probably hit Mars a lot more frequently than on Earth? If the dome was big enough, would the air inside act as a sufficient radiation shield? I'm beginning to think that maybe more permanent residents might choose instead to build structures that are covered with enough regolith to block out radiation and protect against micrometeorites, or maybe they'll stick to hab-like modules that are well shielded. Personally though, I'd rather live in a big dome where I could have some running space.
To achieve the impossible you must attempt the absurd
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Hmm, to block out harmful light, all you'd have to do is coat the dome with UV blocking material (the same stuff on eyeglasses, sunglasses, car windshields, etc).
As to other radiation. I don't see why we can't simply employ a large magnetic field around the whole base. You could inject plasma outside of the dome, which would extend a magnetic field many many miles.
I don't think micro-meteorites pose much of a problem. If they were to hit one, I doubt they would make a hole. It would be like hitting a steel wall (assuming micro means something smaller than the size of a grain of salt).
Some useful links while MER are active. [url=http://marsrovers.jpl.nasa.gov/home/index.html]Offical site[/url] [url=http://www.nasa.gov/multimedia/nasatv/MM_NTV_Web.html]NASA TV[/url] [url=http://www.jpl.nasa.gov/mer2004/]JPL MER2004[/url] [url=http://www.spaceflightnow.com/mars/mera/statustextonly.html]Text feed[/url]
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The amount of solar radiation reaching the surface of the earth totals some 3.9 million exajoules a year.
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That's a scary thought. If permafrost is indeed uniformly spread over the planet just a few meters deep that might cause some problems. The melted permafrost could definately cause the support structures of the dome to sink.
Civil engineering practices on Earth could be applicable to this problem since the same things happen on this planet. If you encounter ground water that's above a certain level the solution is usually to build up the pad or sometimes you can situate the structure on piers using special and expensive types of concrete. If the underlying material has a high clay content, the supports will likely need expansion joints as clay is very expansive even after it's compacted (that's assuming the water is contained mostly in clays). Then again if the water is mostly contained in rock, it might be a non-issue.
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Micrometeoroids are not a problem on Mars; the atmosphere stops them. I think the smallest craters on Mars are about 100 meters across, which means anything less than about a meter or two in diameter is broken up by passage through the Martian atmosphere.
As for melting any permafrost, this could be a problem. Near the Martian equator the top few meters of regolith probably have very little water in them, so putting a heated dome on top would not result in mud. The liquid water would slowly vaporize and escape into the atmosphere. I suspect a bigger problem, though, would be freezing of the soil inside the dome, because the regolith right now probably has an average temperature of about forty or fifty below zero. You could balance out the problem by putting inside your dome the right amount of soil. Let us say the heat in the interior of a dome were such that the top meter of ground would be thawed by it. Then you install your dome, fill it with a bit more than a meter of soil, and let the top meter thaw out from the heat above. The dome's plastic "ground cloth" would be permamently frozen in place underneath, impermeable to water and gas transfer.
As for cosmic and solar radiation, the Martian atmosphere, according to *The Case for Mars,* provides adequate shielding for growing plants and provides considerable shielding for humans. I suspect the best design for a Martian "town" would be to build the housing and work space into the dome edges, so that they would be under at least two or three meters of regolith for radiation and shielding and insulation, but to have windows opening into the dome for light and easy access to the vegetation areas. If beds and other heavily frequented areas were a few meters back from the windows, they would be very low radiation environments, but would still benefit from the light and airiness of the dome.
People could even have porches and patios to their housing. You'd just want to have a roof over the porch or patio with a few meters of dirt on top of the roof to protect you from cosmic and solar radiation. You could sit in your lawn chair and look out on the corn and vegetables growing in the middle of the dome.
-- RobS
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I tend to thing on the conservative side, since the martian colony won't be viable until martians can safely have children. This may mean everyone donates sperm and eggs which are kept deep underground, but the lower the technology base, the more reliable systems will be.
I favor domes for plants, but they will be pressurized with CO2 compressed from the martian atmosphere, not valuable breathing air. Workers can wear gas masks in a shirtsleeve environment when maintaining the infrastructure.
My favorite vision of a human hab, is a tunnel dug into the side of a canyon or mesa, looking out over the valley. A spectacular view, with plenty of regolith above. And lava tubes, naturally, for the big and cheap solution, if they can be found.
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As far as plants go, I don't know enough biochemistry to do more than guess. I just have a hunch that the cheapest, easiest plantation is going to have an atmosphere that humans wouldnt' want to breathe. Maybe just because it generates more plot potential for science fiction stories. Argon is more common on mars than nitrogen, so I expect it could become the inert 'filler' gas (not sure if it has any ill effects on humans) wheras any available nitrogen is going to want to get used in fertilizer.
Reenforcement of celings against regolith weith might itself be heavy, but I think all of this assumes that we'll be able to use martian materieals for some kind of concrete equivalent. If all structural members have to come from earth, there is no way to make a colony affordable.
As for lava tubes suddelny becoming filled with new lava, all the evidence points to mars with no internal activity at all. No marsquakes to speak of, no magnetic field, nothing to suggest that there's anything hot below tha martian crust. If this turns out to be wrong, it's all for the better, since there would then be a possibility for geothermal power. As for the risks of living on a dorman volcano, humans do it all the time. Of all the risks that martian colonists run, being flooded with hot lave seems really, really, remote.
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