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The temperature, pressure and radiation are all not optimum on Mars for life. But if the pressure were several fold higher (20-30 mbar instead 6 mbar), the temperature 5C higher, and with less radiation could we manage an open air lake seeded with all the life needed and fish? This could provide food for a colony but I want to make sure it is doable.

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  • $\begingroup$ Is it allowed to have the lake under a thick sheet of ice? Like miles thick, similar to Lake Vostok in Antarctica? Because I don't see how you could have open water... $\endgroup$
    – AlexP
    Oct 21, 2021 at 15:55
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    $\begingroup$ no. No oxygen, no fish in a lake $\endgroup$
    – MolbOrg
    Oct 21, 2021 at 16:13
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    $\begingroup$ @MolbOrg why no oxygen? What about oxygen making algae? $\endgroup$
    – Charley R.
    Oct 21, 2021 at 16:39
  • $\begingroup$ @CharleyR. or you have enclosed system, like lake covered with ice and there will be not a lot of sun for plants, but it may be possible in some exotic situation, as it seems to me, however, pressure may be a problem as well. Or if the system aka lake is open there will be more CO2 than O2, and it is not expected that algae can pump oxygen faster than the lake loses it - it is not a place with plenty of suns. Low pressure also means lower concentrations of oxygen in water, and even if it is there a fish will need to "filter" proportionally more water to get it usual amount of oxygen - so, no $\endgroup$
    – MolbOrg
    Oct 21, 2021 at 16:51

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You can not have an open air lake on Mars

Lower gravity causes gases on Mars to escape off into space. It's solid core also means that Mars has no magnetosphere so solar wind speeds up this process. Since you are assuming slightly higher air pressure and slightly less radiation, I will suppose you gave mars a molten core, but your low gravity will still be a very big problem. On Earth, water vaporizes, gets caught in the atmosphere by gravity, and eventually becomes dense enough to form rain and come back down.

Mars will still have evaporation, but the air will never get thick and cold enough at the same time to precipitate; so, an open air lake will quickly dry up.

As for Fish as a Food Source on Mars

If you want an "open air" lake, it will need to be part of some contained habitat. Keep in mind however that open lakes are REAL inefficient sources of meat. In a natural lake, most of the biomass is not things that humans eat; so, you generally only get about 25-100 lb of meat per acre per year. For comparison, 1 acre can sustain a production of about 1700 lb of chicken per year or about 3000lb of wheat or soy or 50,000 lb of potatoes making open pond fish farming a bad source of food anyway.

If you insist on fish, you will want to really min-max how your raise them. If you have a catfish farm, you could use reflectors to heat vertical glass tanks, and add sewage to encourage rapid algae growth providing a good food source for a dense fish population. Mechanically aerating the water is also a must. This way you can get a good sized meal fish that eats an easily grown high energy primary producer. Done right, you could probably achieve close to chicken levels of efficiency with fish, but not in an open lake.

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  • $\begingroup$ There is a small area at the bottom of one of the Martian canyons where the air pressure gets above water's triple point. Still too cold for most fish and their food organisms, but a lake could freeze over there and avoid evaporation (except on the hottest days) for decades or maybe even centuries. $\endgroup$
    – Zeiss Ikon
    Oct 21, 2021 at 17:12
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    $\begingroup$ @ZeissIkon yeah... but if it freezes over, is it really open air lake? $\endgroup$
    – Nosajimiki
    Oct 21, 2021 at 17:15
  • $\begingroup$ I guess that depends on the OP's definitions. Still, there's life below the ice in many lakes in North America, Europe, and Asia -- albeit they all thaw for much of the summer. Under-ice lakes in Antarctica are closer to what we're after, in terms of long term permanent ice cover, but they don't have much complex life, certainly not enough to be a food source. $\endgroup$
    – Zeiss Ikon
    Oct 21, 2021 at 17:17

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