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One idea that's often floated when discussing ways of constructing martian habitats is that of "doming" over small craters or valleys and pressurizing the whole area. This would have several advantages such as having a large open space for scientists/colonists to spend time out of their spacesuit and protecting the people from the harsh conditions on the surface. One problem that this presents though is that underneath a transparent dome the people would be exposed to more radiation from the sun and cosmic background radiation.

Question: What would be the most effective building material that is transparent, easy to obtain on mars, and protects the people inside from radiation and other martian dangers?

My idea: Glass can be produced on Mars with the abundant silica deposits and reinforced with layers of plastic brought from earth. Then, these glass panels are cut into triangular shapes and two geodesic dome structures are built inside each other. The space in between these two domes is filled with water providing an excellent radiation shield and automatically "repairing" any punctures or cracks due to micrometeorite impacts by freezing upon contact with the martian atmosphere. Water is either insulated so it doesn't freeze inside the dome or is actively heated (maybe as coolant for a nuclear reactor).

Dragongeek
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    Lead glass is used for radiation shielding agaainst gamma and x-rays. – Uwe Nov 30 '17 at 20:21
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    Why does the dome need to be transparent? – Dan Pichelman Nov 30 '17 at 22:03
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    @DanPichelman I think it's important for the psychological health for the people to be in an large open space and have view of the sky. Permanently being inside small confined environments isn't good for people – Dragongeek Nov 30 '17 at 22:09
  • @Dragongeek, but what would be the thickness of this water layer? Wouldn't people feel being confined in a large aquarium instead of a cave? Also I doubt known materials would allow building an economically viable dome aquarium of sufficient height. Current world record is a cylinder 24 meters high, and it's not made of fragile silicate glass. – ZuOverture Dec 01 '17 at 13:04
  • @ZuOverture, I was thinking the water thickness being between 10 and 100cm so not all that thick. I think if constructed in a geodesic dome, this could be strong enough. In this image: http://www.seattleaquarium.org/image/private-events/Aquarium-Photos-017.jpg a dome is used in a museum with much more water overhead than I'm suggesting. I'm suggesting water be used as it's a high-quality radiation shielding material readily available on mars. – Dragongeek Dec 01 '17 at 15:52
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    I have seen the water proposal for the moon, also. You want nearly 10 meters of water, though--not only is your 100cm not enough radiation shielding, but your city needs air pressure. Match the pressure of the air with the weight of the cover and you don't have a bunch of force on it. – Loren Pechtel Dec 03 '17 at 04:41
  • https://space.stackexchange.com/questions/26430/would-a-faraday-cage-made-of-gas-block-radiation – Muze Oct 21 '18 at 22:01
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    @AviCherry, you are accidentally mixing ton force with ton mass. Since Martian gravity is about 1/3 Earth's, you need either 3 times the depth, or 1/3 the air pressure. – Lex Feb 13 '19 at 03:12
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    (thx lex for the reminder of Mars gravity!) Just to add some numbers into @LorenPechtel 's comment, 100cm of water would reduce the radiation to a little more than 1/50th of the original level. That's at the cost of 1/3t per square meter of dome (in Mars gravity). Atmospheric pressure is about 10t per m2, which makes 30m of water equal it out (ignoring Mars's negligible atmo pressure). That would reduce radiation to about 1.1e-50 compared to unshielded. source: space.stackexchange.com/a/1826/17980 – Avi Cherry Feb 13 '19 at 20:34
  • You might get some good responses from Worldbuilding crew for this question, as well. It's a very frequent topic. – Mikey Feb 14 '19 at 18:08
  • somewhat related: Martian Watershield Greenhouse – uhoh Feb 25 '19 at 03:30

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I would use ice. It can still be transparent and can be reinforced with a sort of net, or transparent coat. It seems that on many area of Mars temperatures never reach enough degrees to make ice melt or vaporize.

There is a special glass capable to shield radiation and pure silica was also found on Mars, together with other minerals. The problem I guess, is fabricating it on Mars. osapublishing.org/ome/abstract.cfm?uri=ome-6-2-531 Glass composite as robust UV absorber for biological protection

Ice may be covered with a coat of sprayed polymers, even if it will not last forever. The good thing is: when it starts to become thin, it's easy and cheap to fix it.

Bea
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  • Ice would be a poor material, as it can sublime even in cold temperatures, and especially in the thin atmosphere of mars – Ingolifs Feb 13 '19 at 02:24
  • @Ingolifs see answers If there is actual ice on the moon, why hasn't it sublimated?. Sublimation rate (like evaporation) is a strong function of temperature so it just needs to be kept cold in sunlight. By definition, a transparent slab of ice will not absorb much visible light, at the same time ice is opaque in thermal infrared and so has a high emissivity, and so can effectively radiate into space 24.6/7 even if the Sun is out. So while some careful thermal though and engineering is called for, it may be too soon to call it a "poor choice". – uhoh Feb 13 '19 at 03:00
  • @Ingolifs "...especially in the thin atmosphere of mars." To first order, I don't think that the sublimation rate depends strongly on the atmosphere's total pressure. It does however depend on the partial pressure of water in the atmosphere, so maybe "...especially in the dry atmosphere of mars" is better? – uhoh Feb 13 '19 at 03:02
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    Hmm. It will be a dynamic equilibrium - the ice sublimating and refreezing elsewhere. Doesn't make for a good permanent object. Besides, you've also got the inside of the base to contend with. You could do a triple glaze or something with 2 layers of glass and one of ice, but at that point, you might as well make all the layers out of glass. – Ingolifs Feb 13 '19 at 03:11
  • @Ingolifs I think this is quite an intriguing engineering exercise. It will certainly need a vent at the top and drain at the bottom for safety, sort of a "living shield" requiring maintenance. – uhoh Feb 13 '19 at 04:45
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    Thank you for your help @uhoh, I've edited the answer and deleted the comments, sorry for the oversight. – Bea Feb 14 '19 at 15:21