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I favor dirt and worms, as soon as it becomes feasible to have them, over hydroponics for the first generations of Martian settlement because of the moving parts issue. If you can bring the microbes and worms from Earth along with the minimum of chemical fertilizer, then treat some regolith as described further up this thread, you have dirt. Dirt+organic waste+attention=more dirt. A hydroponics setup, however, has parts that wear out, and until the Martians can make replacements on Mars from raw materials, those parts will have to come from Earth. On the other hand, a hydroponics setup can produce lots more food in much less space, and don't some versions double as water purifiers . . . ? I think a permanent base should start with a double hydroponics/dirt setup, then go to all dirt as parts wear out, then back to hydroponics when Martians are doing their own manufacturing.
The main principle behind hydroponics is gravity it is the gentle running water flowing down hill that powers the system with the occasional astronaut pouring the solution in the lower bucket into the top one...simplicity.
Why use such a basic system, basically hydroponics lends itself to using lights etc to stimulate growth. And we will have to use these artificial lights just to top up the poor amount of light available naturally. And we cant really afford to have pumps drawing power as well and it is best to set up a system that requires as little mechanical devices as possible. We can also use hydroponics to break down the water that astronauts use for washing so called grey water into useful systems.
Quote RobS Dec. 07 2004, 19:03
Grypd, I dont think rare metals are that serious of a problem. I dont think basalt, for example has significant quantities of them. Most soils on Earth dont have them. There may be soils on Mars that have them, though.
We can be assured that trace rare metals will be spread across the martian regolith there is no soil or condensation to have kept it stuck to the ground and each dust storm will simply move it about. We cannot take the risk of astronauts being affected by the insidious ways that metals poison people. We do know the Regolith fines will get everywhere and pose a danger to a lot of systems. At least with Hydroponics these can be filtered to remove as much as is possible. What we also do know is the Mars has a lot of sulfur. These for plants are extremely dangerous and will damage them. Also the oxygen is bound up in the form of stable iron oxides so reducing two important needed elements to impossible to get at. Iron and free Oxygen. Bluntly the Martian soil is a salty mess with no biomass and it would have to be extensively treated to become useful. You put a worm in the Martian soil and it will become dessicated very very quickly.
Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.
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I'm not sure we will need to supplement natural light artificially. If the greenhouse is oriented north-south and the east/west sides have a silvered reflecting surface, the western side being up and reflecting in morning light and the east side being up in the late afternoon to catch the afternoon light, that will increase total sunlight as much as 60%. Except during duststorms (when you may want to plant only a few crops able to handle lower light levels; basically terrestrial shade crops) it may be possible to grow crops like on Earth.
Yes, there is wind-blown dust everywhere. But that dust probably does not have toxic levels of rare elements because the wind-blown dust will be an average of the Martian crust. In fact, rather like the muds on abyssal plains under our oceans, the eolian dust can be used to study the average crust. It is unlikely that selenium, arsenic, cadmium, etc., are toxic in average Martian crust. Present, yes; but they are present in farming soil on Earth as well.
The best potential farm soil on Mars may be old sedimentary deposits made by catastrophic floods, because all that water may have washed many substances out of the regolith, and would have sorted it by size as well. It will still be slightly salty, but rinsing will probably solve the problem. Eolian dust may be good as well; some of the best farmland on Earth is in loess deposits. Loess is wind-blown dust blown off the front of a melting continental ice sheet or a desert (like the Gobi). it's mostly inorganic material, physically weathered and rather poorly chemically weathered. One possible problem, though, is that Martian loess deposits will be made of much smaller particle sizes.
And of course, all this is speculation until we bring back samples.
-- RobS
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A topic of Robert Dyck
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