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I've been researching the idea of spreading out vast sheets of aerogel across regions of Mars. This would theoretically have the effect of both warming whatever land is under the sheet - thus melting the permafrost and forming lakes - as well as blocking UV rays.

A dome of such material over a large enough parcel of land would mean that colonists wouldn't have to live underground. As long as they remained under the aerogel, their biosphere would simulate being on Earth, albeit with only 38% of our gravity.

Question: What volume within the domed area would be needed to produce its own weather system, including rain and/or fog? I'm envisioning an aerogel "roof" over the entirety of Galle Crater (215km diameter).

Thanks in advance!

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    $\begingroup$ The issue with Mars is not UV radiation - That is blocked easily - but rather solar wind. UV rays on Earth are mostly blocked by the atmosphere. Solar wind is blocked by the magnetic field. Solar wind took a great part in dispersing Mars' atmosphere. It would find the low-density aerogel easy to penetrate. Plus, aerogel may be too brittle to handle micrometeorites and hold pressurized domes. I recommend you to watch Isaac Arthur's Youtube channel, episode "Domes on Mars" for more information. $\endgroup$ Jan 31 at 16:09
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    $\begingroup$ Aerogel is a bizarre choice of materials for construction of pressurized domes. Basically none of its special properties are useful in such an application, and it has enormous disadvantages in mechanical properties, cost, and ease of manufacture and handling. $\endgroup$ Jan 31 at 20:07
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    $\begingroup$ @ChristmasSnow Solar wind is mostly protons. A mm thick layer of anything blocks it. Problem is only that so we have secondary gamma radiation and that is already hard to block (requires tight metal layers, impossible in planet size and anyways it would shade sunshine). $\endgroup$
    – Gray Sheep
    Jan 31 at 21:23
  • $\begingroup$ @ChristopherJamesHuff I think, a power line around the Martian equator, pumped by constant circular current, could serve as the source of an artifical Martian magnetic field. Once I calculated it, the required wiring is huge but not impossibily huge (not much bigger as a huge gas or oil pipeline today). I see some chance that ultimately it could be make more economical to do that with superconductor and push the energy to its cooling (today nitrogen-cooled superconductors already exist, technology should be developed to make them planetary sized). $\endgroup$
    – Gray Sheep
    Jan 31 at 21:27
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    $\begingroup$ The solar wind is a non-issue, it's already blocked by the atmosphere. There is no need for a global magnetic field. $\endgroup$ Jan 31 at 22:38

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In order to get proper "weather systems" the habitat would have to be truly vast and kilometers tall. Rain might be achievable in a much smaller habitat (hundreds of metres) and fog could probably occur in almost any sized open space given the right atmospheric conditions.

But weather systems would be that last thing to worry about. The 800kg gorilla in the room is the pressure inside the structure in fact at 1 atmosphere there would be 10 tonnes of force exerted on every square metre of roof (so a dozen gorilla's worth in force give or take). aerogel just won't stand it and would be blown apart in milliseconds. Any large structure on Mars would require a massive pressure vessel to contain it.

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    $\begingroup$ "almost any sized open space given the right atmospheric conditions". 100% true. My 8' by 8' greenhouse gets quite a bit of fog in just a few hours if I forget to open the vents in the morning. $\endgroup$
    – user4574
    Feb 1 at 1:45
  • $\begingroup$ Yes like my bathroom! $\endgroup$
    – Slarty
    Feb 1 at 18:44
  • $\begingroup$ When I refer to aerogel I'm only thinking of its insulating and shielding properties - not its need for reinforcement. It would likely be placed within layers of tempered glass, plastic, or some other strong and translucent material, webbed with supporting beams. $\endgroup$
    – ajderxsen
    Feb 20 at 19:19
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    $\begingroup$ May be in the fullness of time they will do such a thing, but the "elephant" in the room is the pressure inside the "dome" which would be about one adult elephant's mass pushing out on every 6 square feet. I haven't done the calculations but there must be an awful lot of 6 square feet elephant pressure panels in a crater that is km's across. $\endgroup$
    – Slarty
    Feb 20 at 23:25
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    $\begingroup$ Yeah, extra mass is actually desirable in this application, and aerogel's single most defining characteristic is its low density. You would use aerogel if you needed to minimize the mass of the dome, when you're more likely to be piling regolith on top of it to weigh it down. A thick enough layer of regolith that the insulating properties of aerogel are unnecessary. $\endgroup$ Feb 21 at 21:48
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A lot smaller than you think.

May I present the Goodyear Airdock

It is an airship hangar, 358m long x 99m wide x 64m high or ~2 million cubic meters.

Notably, in high humidity conditions, it is well known for the internal humidity condensing into a mist and raining inside the building.

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  • $\begingroup$ Thanks for the info. When you refer to "high humidity," how would that relate to the average temperature that humans would experience within? $\endgroup$
    – ajderxsen
    Feb 20 at 19:26
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Martian atmosphere is only 0.6% of ours. That is the main problem. Mars is practically vacuum. Aerogel will fall down to the soil.

The density of the lightest aerogel is about the same as air, however as aerogel is essentially a sponge. Air goes into it and the density of the result will be roughly the sum of the density of the air and of the aerogel.

It is very likely not possible to have aerogel floating in the Martian atmosphere. I can not find a reference of an aerogel floating in the Earthian, 160 times denser atmosphere, on the reason above.

Even if it would work, the problem of the lack or air would still exist. You need to find a way to give them air. About a 0.1 atm of oxygen would be already enough. Mars has 0.006 atm of carbon dioxide.

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    $\begingroup$ The only use of aerogel I conceive in this setting is serving as an insulator lining the inside of the domes, which are made out of a much stronger material. Aerogel still lets in most of the light while being a good insulator and would not add too much weight to the structure. The domes, on the other hand, will carry most of the load comprising the weight, the internal pressure, radiation and micrometeorites. $\endgroup$ Jan 31 at 18:53
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    $\begingroup$ You know you can add atmosphere via asteroids right? The question if not explicitly stating it implies an imported atmosphere. $\endgroup$ Jan 31 at 19:30
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    $\begingroup$ @Slarty there are proposals for terraforming mars that include adding nitrogen (which mars lacks, and a breathable atmosphere needs something inert as a buffer) from one or more outside sources. One such source is outer belt asteroids. That's only one of many steps though. $\endgroup$
    – Syndic
    Feb 1 at 7:51
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    $\begingroup$ The question seems to imply several misunderstandings, so I could be wrong, but I don't think they were suggesting that the dome material would be buoyant and floating in the atmosphere of Mars, I think they were suggesting conventional pressurized domes, just constructed of aerogel for some reason. $\endgroup$ Feb 1 at 17:16
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    $\begingroup$ @Slarty Not bad, but also the asteroids have no oxygen. Some of them has water, from which oxygen can be extracted. Much more simple: extracting the O2 from the Martian soil. About half of the mass of the Martian crust is O2. It has to be heated to about 1000C and catalized electrolysis can extract the O2 from that. Another problem: the required mass of oxygen is about 300 000 times of steel produced by the whole Earth in a year. $\endgroup$
    – Gray Sheep
    Feb 1 at 18:51
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Addressing some issues with the premise: aerogel is simply not a viable material for construction of pressurized domes, its tensile strength is quite low. It has impressive compressive strength, but it is so fragile that attempts to build actual structures with it are likely to result in a pile of aerogel shards and powder. Nobody builds anything out of aerogel, it's used as a non-structural material.

Also, UV protection is trivial, it's charged particles you need to worry about. For ionizing radiation capable of penetrating the atmosphere (mostly galactic cosmic rays), an aerogel dome may as well not be there. The radiation environment on the surface of Mars is already a little bit better than that on the ISS due to the shielding of the atmosphere, but permanent habitation will require more protection, and for that you want mass between you and the source, not the lightest material you can manufacture.

Additionally, with a full breathable atmosphere inside, there's 100 kN of outward force on every square meter of the dome. Ultra lightweight materials are the opposite of what you need here...you want a heavy dome, so its weight counters part of that pressure. A sufficiently thick layer of radiation shielding will help reduce the tensile requirements of the dome, and will also be a good thermal insulator. Aerogel just isn't advantageous here.

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  • $\begingroup$ (a) The aerogel would be reinforced; I just didn't mention that. (b) There's already lots of literature on aerogel usage on Mars. Just google "aerogel + mars" and you'll immediately find some. (c) I shouldn't have mentioned the aerogel, since my concern here doesn't require a particular material in the dome; it concerns the /sheer volume/ of the habitat required to produce its own weather system. $\endgroup$
    – ajderxsen
    Feb 20 at 19:32
  • $\begingroup$ The aerogel would not be reinforced. The dome would simply not be constructed of aerogel. Aerogel is not a structural material. You don't build domes out of it. $\endgroup$ Feb 20 at 20:46
  • $\begingroup$ Hmm, not sure how to take this (and similar) article, then: discovermagazine.com/the-sciences/… $\endgroup$
    – ajderxsen
    Mar 20 at 17:10

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