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[Edits added in italic]

BACKGROUND A few thousand years from now the moon has become one of many habitable places in the solar system. Economy, constant growing knowledge and human will made drastic technological progress possible.

Early on people sat up moon bases and mines and flourishing trade quickly drew more and more investors. In some hundret years domes and cities of domes rouse on the moons surface, as resources were extracted from underneath, experiments and modifications were made in a variety of fields, and AI became deeply engaged in the maintainenace of all of this. People made business out of the delivery of resources from and to wherever they were needed in the solar system. During the course of many centuries humanity learned to terraform effectively and domes became temporary startup solutions. Terraforming is not cheap, but the moons location as easy-to-access trading spot in the solar system (earth-to-moon-to-mars / mars-to-moon-to-io / Kuiper belt-to-moon-to-earth etc) made it rich and thriving for progress.

People have for long preserved earth's genetic heritage for multiple reasons and spread it to the other habitable places, in adapted forms. The moon, closest and therefore a perfect second hard drive, becomes over the course of a millenia swamped with flora and fauna. Modification in order to preserve is morally totally fine, but still not completely discovered. People, plants and animals feel fine (enough) to not suffer from living on the moon.

This future moon acquired the following conditions

  • Energy is provided by mega structures (have to look into that), as well as provided by nuclear fusion with helium 3 mined on place, but there is a lot of solar energy around, especially from tall towers in more or less permanent sunlight on the poles. Waste-to-energy became also pretty efficient, and there are some neat setups that use waste for other productions, like biochar, and some waste heat is converted into energy as well.
  • A thick, breathable atmosphere, rich on water vapour, is kept up with imported resources (AI and complex structures keep it dense, balanced and maintained). It keeps the temperatures in range and protects from space threats.
  • An artificial magnetic field (AI is my cheap answer on that, too), to help keeping the atmosphere.
  • Enough water to create lakes and seas with a depth of 10 meters, and more brought by daily delivery (just like the 1950s milk man, only a business some million times bigger, travelling from the Kuiper belt to the planets).
  • 29 earth-day long days (14,5 days day time, 14,5 days night time, a sunset about 1 day long)
  • 13 days per year. The four seasons as we know them are about 3 days long each.
  • Temperature differences caused by the long "nights" and "days", ranging from -90 C to +70 C in the most extreme places. These provoke strong winds and thunder storms. The average temperature is +25 C in summer and -20 C in winter.
  • Habitable places, close to the poles and further off from the equator, experience -5 C during "summer nights" and up to -50 C during "winter nights", and the days warm up to +45 C during "summer days" and +5 C on "winter days". Just like on earth now, no one lives long without a house of some kind, but you can be outside for a limited amount of time with the right clothing.
  • [Comment: deep-freezing is apparently something to avoid, going to look into that]
  • There are mainly fast travelling clouds, clearing off in the middle of the day in spring, summer and autumn (after about 8-11 earth-days) when air starts to get heated up by the sun, and clouding in during or after sunset when the temperatures drop again, often resulting in thunder storms. Rain and snow falls mainly during the night.
  • Since there is only a 6th of earth gravity rain falls slower and in thicker drops. Hail is a common threat, balls get bigger, but the impact is a 6th softer. It almost always freezes during night.
  • Soil is made from 1/8 th compost or manure, 1/8th biochar and 6/8th gravel (trust me, this works on earth, too). Biochar can be produced on place as soon as there is vegetation. Not the entire surface will be soiled (ha!), only about 3-5%, with an average depth of 30 cm (trees get 80cm, but most plants need less). The manure and compost comes mainly from people and livestock on the moon.
  • Moon-outdoor-plants are modified to have a 13 times faster cycle: daytime is their "summer", night time is their "winter". And just as on earth there are stronger and milder winters; as long as they withstand the hardest temperatures they survive. = My list of outdoor-plants will mainly be inspired by Scandinavian flora, adapted to survive long and strong summers and winters.
  • A lot of annual crops mature within 10-30 days, their seeds are cultivated inside during night and then planted out in sunlight, some might even withstand a few frosty nights (like kale).
  • Greenhouses exist, too. [Will look into how these might look like]
  • I don't go into depth with the description of fauna on this list because it seems not as relevant, but lets say it exists, it's integrated into the system and of use, but also has and causes problems. Like there are bees but they don't adapt well to short seasons, there are birds but they don't adapt well to the magnetic field, and something rabbit-like populates as freely as on earth.

My question is not if it is humanly possible, we assume there was motivation and money. But I wonder if these parameters are plausible or condradictory in any way? Are there "necessities" or consequences from these conditions that I did not see?

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  • $\begingroup$ I'm not clear what you are asking here. 1/8 th of the top 18 inches of topsoil is a huge lot of manure, if you are handwaving away this and the necessity for vast quantities of water/oxygen etc: could you specify what the actual problem is that needs solving? What is it that you can't handwave away? If you tell us then we can help. $\endgroup$ – We are Monica. Sep 18 at 14:24
  • $\begingroup$ I don't see how atmosphere and magnetic field relate to AI at all. Generating a magnetic field requires massive amounts of power, no intelligence, and keeping an atmosphere requires gravity, otherwise losses will be enormous. $\endgroup$ – Whitecold Sep 18 at 14:30
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    $\begingroup$ @Whitecold Titan has a thicker atmosphere than the moon and a similar gravity. There's lots involved with atmosphere retention, but most of it applies to retaining atmospheres over geological time. Artificial atmospheres could be maintained by the using the same means they were created with. $\endgroup$ – Starfish Prime Sep 18 at 17:25
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waste heat is converted into energy as well

Thermodynamic forbids you this, after a certain point. If you dump to the cold side of space that point is pretty low, though

An artificial magnetic field (AI is my cheap answer on that, too), to keep radiation and other space threats at bay.

No magnetic field is going to protect you from UV, X and gamma rays, nor from asteroids. A magnetic field will just protect you from ions.

since there is only a 6th of earth gravity rain falls slower and in thicker drops.

With the same amount of incoming energy and less gravity, clouds will form higher up, since they have to gain the same potential energy. Thus I infer that the drop velocity will be roughly the same as on earth.

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    $\begingroup$ A thick atmosphere will do an excellent job of protecting from hazardous EM radiation and asteroids, just as it does on earth. $\endgroup$ – Starfish Prime Sep 18 at 15:11
  • $\begingroup$ @StarfishPrime, right, but the OP is stating that the magnetic field does that $\endgroup$ – L.Dutch - Reinstate Monica Sep 18 at 15:20
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    $\begingroup$ @L.Dutch I did not mean ALL waste heat, but thought more about something like stirling engines, which are about 25% effective at converting waste heat into energy. $\endgroup$ – Backup Plan Sep 18 at 19:21
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Energy is mainly provided by nuclear fusion with helium 3 mined on place

Moon-encircling superconducting powerlines mean that everyone can use solar, even in the dark bits. Solar power satellites are also a possibility, if you're not into megascale engineering (and if you're not, why are you trying to terraform the moon?)

A thick, breathable atmosphere, rich on water vapour

Where's the nitrogen coming from? How did you transport it to the moon? It isn't as convenient to harvest or ship as ice is, you know.

Dew and rain in the evening will freeze hard, and that's gonna be punishing for outside structures and natural stone. You're going to get massive freeze-thaw damage, and lots of large-scale periglacial landforms. You'll have problems building stuff on terrain like this.

Soil is made from 1/8 th compost or manure, 1/8th biochar and 6/8th gravel

Across the entire moon? If manure is 400kg per cubic metre, and the moon has a surface area of 3*1018 square metres, then a 1mm thick layer of poop is gonna weigh about 15 teratonnes. How are you going to make it all? The same problem applies to the biochar, of course, because you need a suitable amount of bio to char in the first place.

Greenhouses exist, too, but they are less since they need to be powered and can fail

A thousand years in the future, colonies all over the solar system, multiple terraformed worlds, and you can't make power supplies that stay up for a few weeks at a time? Seriously?

Given how throughly mangled all fields will get through deep-freezing overnight, you may as well either dome or bury all your vegetation in underground greenhouses with openable roofing. Of course you're going to be able to keep the lights on, because you can't possibly have got this far and been unable to do so. Hell, if your solar power is efficient enough, it might make more sense to just keep all farms undergound and just have solar panels on top. Certainly, there's no point germinating crops indoors and then taking them outside for dawn. Just take the lighting and insulation layer off the top.

I'll also reiterate my previous suggestion of orbital mirrors to illuminate the nightside so it doesn't just turn into a frozen pitch black desert of death at regular intervals. There's no need for it, and if you've colonised the solar system it is clearly within your power to fix.

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  • $\begingroup$ The OP specified a thick atmosphere, so there's not going to be a deepfreeze at night, just as there isn't on Earth. I do agree that the scale of a lot of what they specified is unreasonable, though.\ $\endgroup$ – jdunlop Sep 18 at 17:37
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    $\begingroup$ @jdunlop the night is 15 earth days long. Its gonna get cold. $\endgroup$ – Starfish Prime Sep 18 at 17:43
  • $\begingroup$ Solid nitrogen could be mined on Pluto, and shipped to Luna by mass driver. $\endgroup$ – jamesqf Sep 18 at 18:45
  • $\begingroup$ @jamesqf that's not a bad idea. I'm not totally sure how much nitrogen you need... lets say half the amount Titan has, so a few petatonnes. That's a few million years of work if you shift a billion tonnes per year. I'll have a think about the energy budget required to lift all that ice, and then land it gently at the other end ;-) $\endgroup$ – Starfish Prime Sep 18 at 19:36
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    $\begingroup$ @jamesqf rough first guess at the energy needed to lift that much nitrogen into a 100km orbit around pluto: about $1.5*10^{25}$ joules. Over the million year delivery schedule, that's a continuous 500GW or so... easy peasy! Punting the nitrogen back in-system should be much less energy intensive, though safely lowering it to the lunar surface will be tricky. $\endgroup$ – Starfish Prime Sep 18 at 19:47

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