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Since the component of mars is mostly Fe2O3 (rust) can we use an acid such as H3PO4 to extract oxygen out of the martian soil?
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I suppose, but it's probably not the most economical way to do it. As you probably know Phosphoric Acid reacts with rust via this equation:
Fe2O3 + 2H3PO4 -> 2FePO4 + H20
Which gets you Iron(II) Phosphate and water. This reaction is used in most industrial strength rust removers/converters. The water you could crack into oxygen if you liked. I suppose you could electrolyze the Iron Phosphate as well if you liked, though it would probably be a very energy intensive process. In the end, this is a fairly poor method of oxygen generation as you would need a steady supply of Phosphoric Acid, which could probably be put to better use. Especially if you are talking about doing it on a planet wide scale, in which case there probably isn't enough acid.
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In the end this probably isn't all that necessary. The Viking probe showed that Mars soil contains fairly large quantities of oxygen, trapped up in clays and other minerals. All that is needed is for this soil to be heated and whetted, and it will release the oxygen. Probably still not enough to breath, but it's a start. The rest will probably have to come from sequestering the carbon out of the large amounts of CO2 that would be released.
He who refuses to do arithmetic is doomed to talk nonsense.
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thanks but do you know what would probably be the most economical way? My science fair project is based on extracting oxygen from the martian environment and that's one of the few ideas that came to me.
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by the way, what kind of temperatures would be required to achieve the iron releasing the oxygen?
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thanks but do you know what would probably be the most economical way? My science fair project is based on extracting oxygen from the martian environment and that's one of the few ideas that came to me.
I guess that supposes what you want the oxygen for. If you want oxygen for smallish scale uses (like providing oxygen for the crew, or for fueling a rocket) then the best solution is probably to crack water into H2 and 02. Mars has fairly large quantities of water, and if your station has access to it, that is probably the best choice. Failing that you can either liquefy the thin martin Atmosphere and extract some oxygen from that, though this would be more energy intensive. As a bonus you would be able to extract other useful gasses like Nitrogen and Argon. Or you could crack the C02 in the atmosphere for Oxygen as well, but this is also fairly energy intensive.
If you are talking about a very large scale (like terraforming Mars) then your options are much more limited. Water you obviously want to keep for other uses in your ecosystem, and liquifing the atmosphere obviously will not work. Your only realistic option is to sequester the carbon out of the CO2 getting you oxygen. On Earth this is done by planets (research the carbon cycle) who use photosynthesis. This is not quite so easily done on Mars as likely no terrestrial plant can survive in the current martian conditions. So any carbon sequestration efforts will likely be made as a part of a whole package of terraforming efforts.
First Mars needs to be heated someway. Popular options are decreasing the albedo, or amount of light Mars reflects by dusting its polar caps with soot or black lichen. Or you could put a giant mirror in orbit. Digging giant bore holes to the planets center has even been discussed. Greenhouse gases might also be used. As the planet heats up, the CO2 on the poles will be released, and the atmospheric pressure will be increased. This would both further increase the temperature (CO2 is a greenhouse gas as well) and allow more complex plant life to be distributed. Industrial efforts to sequester carbon on a large scale might also be used. It would also probably be necessary to import large quantities of Nitrogen from Titan or Venus, and possibly some extra water as well. Hopefully at some point the heating and carbon removal operations will result in a livable enviroment. But that would likely be decades if not centuries after the process has started.
by the way, what kind of temperatures would be required to achieve the iron releasing the oxygen?
IIRC the process is actualy exo-thermic (ie releases its own heat). It happens quite readily at room temperature, but you would have to consult a chemical table or do some experiments to get a better read out on how temperature effects it.
He who refuses to do arithmetic is doomed to talk nonsense.
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Hi everyone, Rhodes.
Rhodes, if you gave us more background for WHY you needed the O2 it would be easier to help you. Yes you could ship acid to Mars but shipping anything to Mars is very expensive. If you are shipping people to Mars they will grow plants and O2 will be generated from water using sunlight.
If you want rocket fuel, then ship a nuclear reactor plus some hydrogen to Mars and use its heat and power to make aromatic hydrocarbons (benzine and like products.)
There is more information here:
Using Aromatic Hydrocarbons for Mars Mission.
The key equation is:
6 CH4 --> C6H6 + 9 H2 + heat
Why not ship the Hydrogen directly rather than methane? Hydrogen has such a low boiling temperature that 15% of it will boil off en route. It is expensive (in terms of mass) to handle it and cool it. It would require less mass to hold on to a tank of CH4 (which readily liquefies at spacecraft temperatures under moderate pressure) rather than H2.
The hydrogen is what we want. It is reacted using the Sabatier reaction with CO2 thus:
CO2 + 4 H2 --> CH4 + H2O.
The methane is used as fuel with O2 split from the water. The H2 released from the water is used to make more methane.
Or you can heat the CO2 in hot H2 in the presence of a chrome catalyst:
CO2 + H2 --> CO + H20.
The carbon monoxide is vented as a waste or could be used as a very useful industrial chemical if your economy has gotten that far. The water is cracked into H2 and O2. (The reason we don't just dig up the rock hard ice and use it directly is that it is easier to build an automated chemical processor that uses the air than creating a mining unit.)
You should look at "The Case for Mars" by Robert Zubrin in your library.
Warm regards, Rick.
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Methane and Hydrogen Formation From Rocks
These rocks are called peridotites and consist of minerals that are rich in magnesium and iron. The most common is the mineral olivine, which consists of magnesium, ferrous iron and silica. Below temperatures of about 425°C (about 800° F), olivine is unstable in the presence of seawater and reacts to form the hydrous Mg-rich silicate mineral serpentine and an iron-oxide called magnetite. We refer to this process of hydrating mantle rocks as “serpentinization”. Serpentinization causes important changes to the physical state of the rocks and the chemical composition of the system, and produces important nutrients for microbial activity.
During the formation of magnetite, part of the ferrous (Fe2+) iron in olivine is oxidized to ferric iron (Fe3+) to form magnetite. This change in the valency of iron consumes oxygen from the fluid and leads to a state that chemists call reducing conditions. As a consequence of the formation of magnetite, hydrogen gas (H2) is produced from the reduction of seawater during serpentinization. Seawater also contains carbonate ions (HCO3- or CO22-) and sulfate ions (SO42-) which can become reduced to form methane (CH4) and hydrogen sulfide (H2S) during the serpentinization process. The presence of the reduced species H2, CH4 and H2S in the fluids that seep out of the rocks provide important energy sources for different microbial species that seem to thrive around the Lost City structures.
So collecting the mineral olivine otherwise known as blueberries could be an easy way to get what we need.
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Methane and Hydrogen Formation From Rocks
During the formation of magnetite, ...
The presence of the reduced species H2, CH4 and H2S in the fluids that seep out of the rocks provide important energy sources for different microbial species that seem to thrive around the Lost City structures.
Hi SpaceNut, everyone.
So this is an indication that the Methane found in Mars' atmosphere is NOT created this way. If it is, then we should see H2S in the atmosphere as well and we do not.
This suggests that life, volcanic outgassing, earthquakes or comet impact are the different ways that it could get there.
Thanks for the interesting post! Warm regards, Rick
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