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#26 2002-10-08 06:52:55

RobertDyck
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Re: Growing plants on Mars

Mars Pathfinder brought along a rover called Sojourner. It had an Alpha Proton X-ray Spectrometer to analyze soil and rocks. You can estimate oxides by applying oxygen stoichiometrically. After doing that, Mars soil contains 0.4-0.7% potassium oxide, 0.5-1.0% phosphorus oxide, 5.4-6.4% calcium oxide, 5.2-6.8% sulphur trioxide. It also has other elements such as sodium, chlorine, magnesium, and lots of iron. Mars atmosphere is 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.13% oxygen, 0.07% carbon monoxide, 0.03% water, and trace amounts of neon, krypton, xenon, and ozone. As I mentioned before, if you pressurizes a greenhouse and use a sorbent to remove 95% of the carbon dioxide and 80% carbon monoxide, and then extract oxygen from the soil by soaking with water to release the super oxides, that should leave you with 45.3% nitrogen, 26.8% argon, 22.3% oxygen, 2.26% carbon dioxide, 0.23% carbon monoxide. The 0.14971% of undetected miscellaneous (probably error factor) becomes 2.51%, and water becomes 0.5%. Humidity can be adjusted by adding water. This is at 5.0 psi pressure. Humans require 60% oxygen at that pressure, but this should be fine for plants. Air on Earth contains 0.03-0.04% carbon dioxide, and concentrations above 2% are poisonous. Carbon monoxide as low as .001% can produce symptoms of poisoning, and 0.5% is fatal within 30 minutes. However, enhanced carbon dioxide accelerates plant growth.

The principle point is that Mars atmosphere contains nitrogen. You don't need to bring nitrogen from Earth.

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#27 2002-10-08 07:47:12

Bill White
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Re: Growing plants on Mars

So the question really is, ?Is it easier to grow plants using complex soil and certain biomass along with lots of bacteria, or is it easier to use raw chemicals in the right ammounts (with some help from bacteria)??

I personally think it would be easier and more efficient to use raw chemicals on Mars.

Josh - I can easily agree that this is the question. I will also agree to keep an open mind as I read further. But, any objection to doing both?

Start with hydroponic greenhouses, using Robert Dyk's idea for obtaining Martian nitrogen and later complement with soil to close the loop on a nitrogen cycle, recovering useful nutrients from plant waste. I agree people waste, and dead bodies, should be pretty much irrelevant to the agricultural systems. Plant waste, however, will contain considerably more useful nitrogen.

However, I did once post an idea that if Mars hydroponics needs a certain element - send extra rations of bananas, for example, and then process the human waste to extract potassium.

Sadly, there may not be much urgency to our settling this debate as it may take decades before the answer is needed.

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#28 2002-10-08 14:17:45

Josh Cryer
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Re: Growing plants on Mars

Hmm, you're absolutely right RobertDyck. I didn't realize the Martian atmosphere contained nitrogen at those levels, I'd been looking at the soil analysis. That totally reduces our shipping requirements. Always a good thing. Your method is pretty smart, and simple, too.

Bill White, nah, not at all. The more I understand how the systems work, the more I think they're both fine, except that hydro/aeroponics are way more efficient, and suitable for space (soil does seem to be more complicated, once you think about it).

I disagree that human waste is not relevent to the agriculture cycle, though. Whenever we empty our bowels, we're literally exhausting those plant molecules we ate three days or so ago. Those molecules have to go somewhere. Allowing them to flow out onto Mars would be inefficient, since they're relatively contained,and we're going to need them anyway. It'd be better to just reintroduce our waste into the system (plus, there's the whole problem with contamination- if we don't recycle, the waste has to go somewhere, and the surface of Mars would make a good place for bacteria; not good for scientists tongue ).


Some useful links while MER are active. [url=http://marsrovers.jpl.nasa.gov/home/index.html]Offical site[/url] [url=http://www.nasa.gov/multimedia/nasatv/MM_NTV_Web.html]NASA TV[/url] [url=http://www.jpl.nasa.gov/mer2004/]JPL MER2004[/url] [url=http://www.spaceflightnow.com/mars/mera/statustextonly.html]Text feed[/url]
--------
The amount of solar radiation reaching the surface of the earth totals some 3.9 million exajoules a year.

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#29 2002-10-08 15:51:58

RobS
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Re: Growing plants on Mars

I think I read somewhere that a Sabatier reactor can be used to make ammonia, just like it can make methane. Ammonia is a key ingredient in making nitrogen fertilizer.

I would guess that even if we bring hydroponics to Mars, we would want to start experimenting with making Martian soil for plants, if for no other reason than growing potted trees (which would be pretty). One would start by bringing hydroponic "miracle grow" and steadily add to it nutrients derived from human waste, Martian air, and even Martian soil (such as phosphorus), but eventually it would be easier to make soil. Once your "starter soil" from Earth has expanded to a couple of cubic meters of soil that is functioning, you can probably add 10% of inorganic regolith to it every couple months, add more fertilizing nurtients, and add dead plant matter. It would steadily increase in mass and after a few years you'd have enough to grow the base's vegetable supply. Then a few years more and you'd be able to support chickens and rabbits. In a decade or two, you could have a pretty complex ecology. Assuming, of course, you have a full time person or two watching the ecosystem and preventing collapses.

             -- RobS

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#30 2002-10-17 12:55:17

RobS
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Re: Growing plants on Mars

Bob Dyck noted that we could easily make an atmosphere with these components:

<<<if you pressurize a greenhouse and use a sorbent to remove 95% of the carbon dioxide and 80% carbon monoxide, and then extract oxygen from the soil by soaking with water to release the super oxides, that should leave you with 45.3% nitrogen, 26.8% argon, 22.3% oxygen, 2.26% carbon dioxide, 0.23% carbon monoxide.>>>

Bob, if you're still reading this thread, how much regolith did you have to soak to release that much oxygen? I ask because it occurs to me that if oxygen is fairly readily available in the regolith, that simplifies Mars exploration greatly. An expedition crossing the surface in pressurized rovers would have to bring along methane fuel for their engines, but not oxygen; and since a kilo of methane requires 3.5 kilos of oxygen to burn completely, that's pretty important! A tonne of "fuel" would take you 4.5 times as far if you don't need to bring the oxygen. But what we don't know is how much reg we have to wet to release the needed oxygen, or how much water we need to release it. Any ideas?

         -- RobS

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#31 2002-10-19 01:16:49

RobertDyck
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Re: Growing plants on Mars

I tried to do a calculation using data available. The problem is estimating the exact composition of Mars soil. The final paper published with results from Sojourner's Alpha Proton X-ray Spectrometer included estimates of oxides by projecting oxygen stoichiometrically. If you assume that Mars soil is exactly those oxides then the chemical reactions are as follows:

Sodium oxide [Na2O] will combine with chlorine [Cl] to form salt [NaCl] and release oxygen. Dissolved carbon dioxide will combine with water to form carbonic acid [H2CO3], which is an ionic compound consisting of 2 H+ ions and 1 CO3-2. Sodium oxide [Na2O] will also combine with carbonic acid to form soda. Dissolved soda will be indistinguishable between sodium carbonate [Na2CO3] and sodium bicarbonate (baking soda) [NaHCO3] due to the presence of H+ ions in water. Potassium is as ionic as sodium, so potassium oxide [K2O] will form potassium salt and potassium soda. Calcium oxide [CaO] will combine with sulphur trioxide [SO3] and water to form gypsum [CaSO4?2H2O]. Calcium oxide is also known as quicklime, which will react with water to form slaked lime and give off heat: CaO + H2O -> Ca(OH)2. Phosphoric oxide will react with water to become phosphoric acid: P2O5 + 3 H2O -> 2 H3PO4. Sulphur trioxide [SO3] will also react with water to form H2SO4, when dissolved in water that is sulphuric acid. Since sulphur exists as a trioxide instead of dioxide, all sulphur reactions will be quicker.

The result of the above calculation is 1.6 grams of oxygen for each kilogram of regolith. If enough CO2 is bubbled through water under pressure to consume all sodium and potassium, then based on sample A-2 it will also produce 11.5 grams salt, 12.7 grams gypsum, 11.0 grams phosphoric acid, 113.1 grams baking soda, sulphuric acid consumed, and 1.8 grams left over calcium oxide (CaO).

My calculations assumed exactly these proportions, a greenhouse with 280 cubic metre volume, and 20 tonnes of regolith to release 32 kg of oxygen. If the temperature was 20?C and 257.86 mbar (3.74 psi) before adding the oxygen, the result should be 344.96 mbar (5.00 psi). That volume was estimated from the dimensions of the greenhouse painting, and the soil mass estimated for soil trays from the same painting.

I have been bugging the head of the geology department of my alma mater to help me with a CIPW analysis of the APXS data to get a reliable estimate of Mars soil minerals. He hasn't had time to work with it. I have also bugged the scientist who did the original CIPW analysis for NASA, and he gave me a copy of his spreadsheet. I got the final results of the APXS instrument directly from the Principle Investigators. I have tried to do an analysis myself, and passed my results and all accumulated papers to another MS member who has geology training. We'll see if he comes up with a better result.

These depend on the composition of regolith. For example, if CaO is combined with silica and alumina to form tricalcium silicate [3CaO?SiO2], tricalcium aluminate [3CaO?Al2O3] and dicalcium silicate [2CaO?SiO2], then that together with magnesium oxide, iron oxide and gypsum is portland cement. When water is added to portland cement it will form concrete. When concrete sets the silicate forms jellylike hydrated silica [SiO2?NH2O]. This could consume nitrogen from greenhouse air and turn the soil to concrete.

Another possibility is clay. The data published by Dr. Philip Christensen, et. al., for the results from the Thermal Emission Spectrometer on Mars Global Surveyor shows two predominant surface types. Type 1 includes 2.4% kaolinite and 9.9% illite. Type 2 includes 2.2% illite. These are minerals of clay. Since clay forms by hydrological weathering of feldspar, this implies Mars had a great deal of liquid surface water at one time. The authors of that paper, however, point out the difficulty in getting accurate results from that instrument. The results they did get indicate minerals that cannot be distinguished by that instrument, so these results are highly preliminary.

The soil will be some sort of mineral, so the chemical reactions I list are highly simplified; but you will notice I didn't include any superoxides either. I also have a paper regarding superoxides as an explanation of oxygen generated when Viking added a soil sample to water. I havn't included the superoxides because I want a much more accurate description of Mars soil minerals before recalculating.

Rob Dyck (last name pronounced Dick)

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#32 2002-10-19 21:39:32

RobS
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Re: Growing plants on Mars

Thank you, this is very interesting. I will look forward to anything your geologist friend says. I never knew that much geochemistry, and the little I know makes me worrisome about all the assumptions. The problem we have is that the Viking and other elemental analyses can tell us the elements, but not their combinations. Sometimes combinatins can be guessed, but even then we are not sure. And the existing combinations make a huge difference in terms of releasing the oxygen. If the Martian regolith basically formed in an aqueous environment millions of years ago and the only modifications that have occurred since are dessication and exposure to intense ultraviolet light (which made the superoxides and peroxides), then wetting the soil now will not release oxygen at all, except from breakdown of the superoxides and peroxides. The other chemical breakdowns to release oxygen upon wetting would have already happened millions of years ago when the sample was wet then. As far as I know, Na2O and K2O almost never exist in nature; they are part of complex molecules, feldspars originally, probably clays now(smectite and montmorillonite have been mentioned as possibilities on Mars).

Even the existence of superoxides and peroxides are now disputed. I remember when the gas release experiment was first performed and the strange results had everyone scratching their heads. Then someone remembered Bob Hugenin's work where he had theorized the existence of superoxides and peroxides. He was flown out to JPL and gave some talks to the scientists and was a hero; he had solved the problems. This is as I remember the events, as a lowly graduate student at the time. I remember looking at Hugenin's papers and being utterly baffled by the chemical equations, pages and pages of them. I even wondered whether the biology experiment guys understood 20% of what he was saying! It was pretty specialized research. Since then the idea of peroxides and superoxides has been disputed, but I haven't read those papers because they were published between 1980 and 2000, when I wasn't paying much attention to Martian geology.

At any rate, we know when you wet the Martian regolith, it releases oxygen; Viking proved that. The mechanism is in dispute, but not the result. I suspect 20 tonnes of reg should degas at least 20 kilos of oxygen; that's only 1/10 of 1% of the mass. It might degass 10 times that; I don't know. I wonder whether 20 tonnes of regolith needs something like 5 tonnes of water to release it, though? I suppose that's not a problem, since it has to be wetted for the plants anyway!

         -- RobS

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#33 2002-10-20 00:31:39

RobertDyck
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Re: Growing plants on Mars

If you're really interested in the superoxides, read the paper Evidence That the Reactivity of the Martian Soil Is Due to Superoxide Ions, A. S. Yen, S. S. Kim, M. H. Hecht, M. S. Frant, B. Murray. This was published in Science, 15 September 2000, volume 289, page 1909-1912. Notice the superoxides can be formed with only 20 hours exposure to UV light in a Mars jar.

The Thermal Emission Spectrometer is based on infrared spectra. One feature it uses is thermal momentum (how fast does it heat up at dawn, and how fast does it cool down at dusk). The reflection spectrum and thermal momentum are compared to known minerals to find a match. Notice this is based on minerals, not elements. The gas spectrometer on Viking and the APXS on Sojourner measured elements, but TES is an attempt to measure combinations. We can only hope the Thermal Emission Imaging Spectrometer (THEMIS) on Mars Odyssey will give better results.

Thanks for the mention of smectite. I knew surface type 2 had a second clay mineral. The TES paper lists 9.2% Fe-smectite. That is a total of 12.3% clay for surface type 1, and 11.4% clay for type 2. The web site webmineral lists 3 minerals in the Smectite/Montmorillonite group that contain iron: Aliettite, Corrensite, and Hydrobiotite. I suppose we have no way of knowing which one(s) is(are) present.

The epithermal neutron map from Mars Odyssey shows a strong water pocket (permafrost) on the equator. If I read the radiation data correctly, that location is estimated at 15 rem/year. That looks like a good location for a base; lots of water.

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#34 2002-10-21 18:11:17

RobS
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Re: Growing plants on Mars

Thank you for these marvelous references!

       -- RobS

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#35 2002-10-22 13:39:11

RobertDyck
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Re: Growing plants on Mars

A couple other references. The radiation is from Odyssey's Marie instrument.

The paper I keep referring to with TES results is A Global View of Martian Surface Compositions from MGS-TES, Joshua L. Bandfield, Victoria E. Hamilton, Philip R. Christensen. Published in Science volume 287, 3 MARCH 2000, pages 1626-1630. An important page of supplimental data is the complete list of surface minerals. These 2 links will require a subscription to Science Online.

The Sojourner data is Chemistry of Mars Pathfinder Samples Determined by the APXS, C. N. Foley, T. E. Economou, R. N. Clayton. Published at Lunar and Planetary Science 32 (2001). A couple qualifications for this paper. There is no nitrogen listed, but the meteorite ALH84001 from Antarctica is believed to come from Mars and it contains polycyclic aromatic hydrocarbons which do contain nitrogen. That nitrogen is in parts per million, and the APXS instrument can only detect elements with concentration at least 0.1%. Carbon content is debated; it is either less than 0.3% or less than 0.8%, but notice both claims say "less than". Hydrogen was not measured by the APXS instrument, so water content is a guess. Oxygen was measured, so the more water the less available for other oxides. This would affect the ratio of FeO vs Fe2O3.

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#36 2003-05-27 18:35:52

Shaun Barrett
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Re: Growing plants on Mars

Hi Robert (Dyck, that is.)!
    I don't seem able to access the paper you mention - "Evidence That The Reactivity Of The Martian Soil Is Due To Superoxide Ions", Yen et al. - without subscribing to Science Online.
    I have come across statements elsewhere, though, which suggest Yen and company used UV  light intensities 100 times higher than actual Martian levels in order to obtain their results.
    Is this true?


The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

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#37 2003-05-27 19:56:06

Critter
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Re: Growing plants on Mars

Why grow plants directly in the soil when you can just grow them hydroponically?  Some greenhouses in Antartica do this very well even in structures that rely on artificial lighting.  They just use PVC plugs to attach the plants to the waterline.  Hydronponically grown plants are often more productive than ones grown in soil.

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#38 2003-05-28 08:53:33

RobertDyck
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Re: Growing plants on Mars

The question of whether Mars has Labradorite has been raised. I tried to perform a CIPW analysis myself using the oxide data from the paper Chemistry of Mars Pathfinder Samples Determined by the APXS. My preliminary result shows Albite 28-30% for samples A-2, A-4, and A-5, about 9.5% for sample A-9, about 14.7% for sample A-10, and just under 26% for sample A-15. The Anorthite concentration is 8.17-9.22% for samples A-2, A-4, and A-5, about 18.5% for sample A-9, 15% for sample A-10, and about 8.5% for sample A-15. These two minerals are the minerals for plagioclase feldspar; their relative concentrations determine which type of feldspar. According to this result, the feldspar in samples A-2, A-4, A-5, and A-15 are Oligoclase, and the feldspar of samples A-9 and A-10 are Labradorite. I also calculated about 2.8% Microcline in samples A-2, A-4, and A-5, 3.95% in sample A-9, 2.25% in sample A-10, and 3.95% in sample A-15. Microcline is an orthoclase feldspar. I had only studied the "soil" samples, not the rocks because I am interested in producing a regolith simulant for greenhouse experiments and a Mars rover test facility.

This is consistent with the TES data from MGS. Again I am referencing the paper A Global View of Martian Surface Compositions from MGS-TES, Joshua L. Bandfield, Victoria E. Hamilton, Philip R. Christensen. Published in Science volume 287, 3 MARCH 2000, pages 1626-1630. That paper identified two surface types on Mars, and determined the surface composition to be varying mixtures of the two surface types. Surface type 1 consisted of 50% feldspar (primarily plagioclase), 25% clinopyroxene (predominantly Augite), and 15% sheet silicates. Surface type 2 was 35% feldspar, 25% glass, 15% sheet silicates, 10% clinopyroxene. The supplemental data web page listed in the references indicated the detailed minerals for Type 1 included 5.8% Microcline, 22% Andesine, 21.5% Bytownite; and Type 2 included 5.7% Microcline, and 27% Bytownite. My CIPW analysis assumed all feldspar within a single sample would be one type, and Labradorite is half way between Andesine and Bytownite, so I think I'm not too far off. The conclusion by other researchers that there is Labradorite would be based on the same assumption.

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#39 2003-05-28 09:04:35

RobertDyck
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Re: Growing plants on Mars

Why grow plants directly in the soil when you can just grow them hydroponically?  Some greenhouses in Antartica do this very well even in structures that rely on artificial lighting.  They just use PVC plugs to attach the plants to the waterline.  Hydronponically grown plants are often more productive than ones grown in soil.

There are researchers studying hydroponics. The issue with hydroponics is balancing the liquid nutrients. Nutrients are very sensitive in hydroponic production, whereas soil provides a buffer as well as a source for mineral nutrients. Besides, if you want to grow something large like a fruit tree, soil provides a stable base to hold it from falling over.

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#40 2003-05-28 22:49:31

rgcarnes
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Re: Growing plants on Mars

I've just done a quick review of these posts and more than once the comment has been made that there may not be enough available sunlight. 

I could tell a long story giving the background of this information, but I'll refrain.  The source of this idea is a physicist, a Mr. Graham Flint. 

A great deal more optical energy is available than is used directly by chlorophyl.  Chlorophyl uses mostly red light to perform photosynthesis and (NASA research also says it takes a little blue).   The other parts of the spectrum are, in the simplest view, just absorbed as heat, or reflected, or, in the case of some of the ultraviolet, utilized in raising problems with important chemical bonds.

It turns out, that some of this other energy can be converted to red photons by certain flourescent materials.  This can be done simply by painting the portions of your greenhouse enclosure not appropriate for use as window surface with fluorescent orange paint.   Light striking these surfaces is partially converted to the absorption bands of chlorophyl, increasing the efficient use of the available light.

Mr. Flint did experiments on the island of Gurnsey and showed earlier ripening tomatoes with the available seasonal sunlight by this method.


Rex G. Carnes

If the Meek Inherit the Earth, Where Do All the Bold Go?

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#41 2003-05-29 10:32:10

RobertDyck
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Re: Growing plants on Mars

This is an excellent idea; however, the absorption spectrum of chlorophyll is not as simple as that. (It's never simple.) The Estrella Mountain Community College has an excellent photosynthesis page. If you go to the chlorophyll section and scroll down to the chart titled "Relative rate of photosynthesis" you will see that chlorophyll absorbs blue light, and some red. The accessory pigments absorb yellow and orange. In fact, chlorophyll a absorbs about 25% of violet light, and the accessory pigments absorb a little ultraviolet light (less than 20%). In the visible range, the least absorptive is at 500-520nm wavelength, which is green light. That is why plants appear green. It is interesting that the lowest rate of photosynthesis is at 550nm wavelength, indicating that the accessory pigments don't work as well as chlorophyll.

If you want to use florescent paint to increase light available to plants, I would suggest something that fluoresces in the wavelengths 410-450nm (blue) or 660-670nm (red). The blue light actually produces more photosynthesis, but that is because shorter wavelength photons have more energy. As an alternative, it might be simpler to coat non-transparent surfaces with a mirror-like coating. Simply reflecting more light into plants would help.

Also, I tried to do a calculation of the amount of light available, ignoring any absorption by the atmosphere. The light available per unit surface area on the equator of Mars at high noon of the spring and autumn equinox is the same as Fairbanks, Alaska, (also high noon at the equinox). This is due to the curvature of the Earth spreading light over a larger area. The higher latitude you go on Mars, the higher latitude on Earth you need to find an equivalent. Notice that Fairbanks, Alaska, is not as far north as Devon Island.

How did I calculate that? The intensity of light follows the inverse square law. Earth is an average of 149,600,000km from the Sun, Mars is 227,940,000km from the Sun. If M is Mars average orbital radius and E is Earth's average orbital radius then the relative sunlight is (M^2)/(E^2) = 43.075%. This is the intensity of sunlight available in space or in orbit. The amount of light on each planet per unit area at the equator at high noon at the equinox will also be exactly this ratio (ignoring absorption by the atmosphere). As you move on Earth to a higher latitude, the curvature of the Earth will spread light out over more land: normal 100% light at 0? latitude (equator), 70.71% at 45?, 0% at 90? (pole). Light intensity is COS of the latitude. Since Earth tilts toward the sun in summer, you would have to subtract Earth?s axial tilt at summer solstice, or add it for the winter solstice. Mars has an axial tilt of 25.19? so the tropics are +/- 25.19? latitude. Sunlight at the Mars tropics at noon on an equinox will be COS 25.19? x 43.073% = 38.978%. Earth has an axial tilt of 23.45? so the latitude on Earth with that same light intensity at noon on the summer solstice will be (arcCOS 38.978%) + 23.45? = 90.509?. It is not possible to go farther north than 90? so this means any location on Earth has more light at summer solstice; however, at spring equinox it is simply arcCOS 38.978% = 67.059? which is farther south than Devon Island. Haughton Crater is 75?22'N so the day which has light intensity most similar to the Mars tropical latitudes at equinox will be 32 days before and after the summer solstice, so May 20 and July 23.

What does this mean? The summer season when FMARS operates has an equivalent light level as latitudes on Mars where a manned mission is likely (relatively warm latitudes). If you can grow plants in a greenhouse on Devon Island, then you have enough light to grow plants in a greenhouse on Mars.

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#42 2003-05-29 12:33:49

RobertDyck
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Re: Growing plants on Mars

By the way, Cindy, this is what I meant by expressing yourself in numbers. I could claim that the light intensity on Devon Island is the same as tropical latitudes on Mars, but someone else could say "no it isn't". We could argue back and forth with "yes it is", "no it isn't", "yes it is", "not it isn't", but expressing it in numbers and showing the calculations explains why I made this assertion. The numbers do add up. In fact, to ensure any solar panels have equivalent illumination as you would expect on Mars, the panels would have to be oriented flat. Tilting the panels to 75? would cheat and give the full illumination available on Earth. This wouldn't account for Earth's ozone layer absorbing ultraviolet light, but that issue would exist anywhere on Earth. The numbers show that Devon Island is a good location to conduct tests.

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#43 2003-05-29 20:49:21

rgcarnes
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Re: Growing plants on Mars

Just reviewed the information on chlorophyll at the link provided.

I must point out that, in the absorption spectra, absorption is not necesarily by photosynthesis.  Be careful of jumping to that conclusion.  Also, I'm very suspicious of plots, such as the one with the vertical axis labeled "relative rate of photosynthesis" with no further details of the measurement.  It may be true in some respect, it may be completely true for the species on which the measurement was made, but it's certainly not definitive for the wider problem.

I haven't really looked at it for a couple of years, but NASA supported research on growing plants most efficiently with electrically powered illumination sources and again found that red light emitting diodes along with a small amount of blue light did a fairly efficient job.

Mirrored surfaces would probably be very difficult to take advantage of for the reason that to make any real gain, angular positioning of each surface with respect to incoming sunlight and the plant target positions must be taken into account.  One could, of course, build your greenhouse at the output port of a nonimaging concentrator structure, but that's not quite as easy as simply painting already existing surfaces with fluorescent conversion paint which really is available to anyone now. 

A very good white paint can reflect light diffusely to achieve a higher total reflectance than most common mirror surfaces, but why not do the fluorescent conversion step and really use some of the optical energy that a plant could otherwise not use even if it were to arrive at the photosynthesis surfaces?

I also will repeat that the effectiveness of the process was not just an idea, but was implemented and verified in a real world experiment.  Tomatoes ripened significantly earlier in the year in the specially treated growing enclosure compared to the standard greenhouses near by, other factors were maintained as nearly equivalent as could be accomplished.  Try it yourself.  It should be both inexpensive and easy.


Rex G. Carnes

If the Meek Inherit the Earth, Where Do All the Bold Go?

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#44 2003-08-17 22:12:25

RobS
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Re: Growing plants on Mars

Does anyone know where one can find a typical elemental breakdown for average plant matter? I am curious what percent by weight of a typical plant is nitrogen, in particular. It is probably the element most lacking in the Martian soil. I suspect plants are only 1-2% nitrogen, but don't know for sure.

      -- RobS

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#45 2003-10-07 22:11:54

grommet37
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From: Earth, currently
Registered: 2003-10-07
Posts: 5

Re: Growing plants on Mars

My personal take on the subject of a future Martian ecosphere would be to utilize those very plants and animals which we find so hard to control on earth: the weed species. By this I mean all the so-called "invasive species", as well as all of the human-introduced "feral" species.
   
   This would include all the "pests" commonly associated with people and their colonization of any area: cats, rats, dogs, pigeons, flies, fleas, ticks, spiders, ants, beetles, termites. Plants would include dandelion, clover, English Ivy, kudzu, crabgrass, purple loosestrife, thistle. For aquaculture, I recommend algae and carp (and tiger mussels).

   Let's face it, if it's hard to kill, if it'll "grow anywhere", that's the stuff we want on our side. People were originally foragers, and ate lots of companion animals and bugs, too. These people will be explorers. They will be somewhat inured to hardship. They will need a source of protein which is not a major drain on their oxygen resources. Small mammals and birds are called for. As well as insects.

    Not only are such animals as dogs, cats, and pigeons useful animals, in that they can be trained to perform useful work functions, they are easily handled by humans. Insects, too, perform many useful functions in the field and garden (pollinators, soil conditioning, etc.).

   Further, our colonists will need a source of raw nutrients, besides just protein. What do doctors constantly tell us we never get enough of? Why our green leafy vegetables, that's right, the bitter greens, the salad greens, the primitive greens. What better source than LED-grown fresh young dandelions? And after the clover and the crabgrass has kicked the crap out of the Martian soil for us we can thank it, by (hopefully) choking it out with primitive grains like buckwheat and alfalfa. I think we'll have to work our way up to your cattle and apple trees.

   One last note. An eminent entomologist who was also a theologian was asked if his many years of study of the processes of Nature had given him any insight into the character of the Creator. His reply was: "An inordinate fondness for beetles". I suggest we take a couple dozen varieties along to our new home, as well.

   For more on Man and his pests, see Twain's "Letters From the Earth."

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#46 2003-10-07 22:38:58

grommet37
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Re: Growing plants on Mars

One more point about greenhouses. I don't believe that they will necessarily need to be transparent. Between the low Martian air pressure and gravity, what goes up may stay up, for a while.

This means that outside the greenhouse, incident light will be greatly scattered before even arriving at the greenhouse barrier. Inside the greenhouse, if we are capable of producing a warm, wet climate, water vapor will be similarly hanging in the air for much longer than it would on Earth (even if the dome is semi-pressurized, for plants, or has 5 psi shirtsleeve life-support atmosphere, that is still less than 14.7 psi). Lastly, have you ever been inside a greenhouse on a cold day? Condensation covers all the interior glass surfaces where the outside air touches them. And Mars ambient average temperature is a lot colder in the winter than Brooklyn.

I believe some sort of low-tech wax-paper/izing glass/visqueen type product could be used if farmers could work in the low pressure plants can grow in. Less internal pressure in the dome could mean building bigger domes. More soil conversion, quicker terraforming. Since plants live on CO2, exposing them to some of the rigors of the Martian atmosphere may not be detrimental.

I think it might be a question of providing the workers with compression fabric clothing, like a luge suit, to keep their skin and fluids in place (full body power shorts). They could also wear very lightweight breating apparatus, as their CO2 and water vapor would be vented to benefit the plants.

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#47 2003-10-07 23:09:37

grommet37
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Registered: 2003-10-07
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Re: Growing plants on Mars

Last thought for tonight. Concerning building domes and greenhouses, Robert Zubrin mentions both inflatables, and pressurized domes made of Kevlar (like an arena cover) with Plexiglas geodesics over them (for cosmic ray protection).

These seem to be fairly clever solutions. Are there other ways to make a bubble?

The first thought that came to my mind was a soap bubble. The inherent flaw in that idea is that it pops.

Okay so instead of soap (which is rarified grease) we use grease itself, or wax (another semi-rendered grease). I've already stated above that I don't think that building a transparent dome will do you much good on Mars. You don't need a clear bubble, like a soap bubble or a glass bubble. That material may be too pure, too brittle.

But it's the method of working the material that intrigues me. In low ambient pressure, under 38% Earth-gravity, just how big a soap bubble can you blow? How big could you grow a glass bubble by forcing hot gas inside? Of course ambient temperature would play a huge role, but on midsummer day on the Equator?

I think that since plastics are really just another form of grease (a complex organic molecule that acts as a lubricant as a gel or a smooth, hard substance when solid), that this could prove to be the way domes are raised on Mars, by blowing giant soap bubbles of a special, waxy polymer, to optimum size, thickness, clarity, color temperature, radiation blockage, or any other necessary parameters.

If you think they'll blow away in the withering Martian wind, remember that it's so much thinner than on Earth (I believe Zubrin said a 60 mph wind would feel like 6 knots or something to that effect). Thoughts?

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#48 2003-10-21 21:25:13

Bill White
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Registered: 2001-09-09
Posts: 2,114

Re: Growing plants on Mars

Grommet37 writes:

My personal take on the subject of a future Martian ecosphere would be to utilize those very plants and animals which we find so hard to control on earth: the weed species. By this I mean all the so-called "invasive species", as well as all of the human-introduced "feral" species.

Okay, here are some fun links on kudzu weed:

The Amazing Story of Kudzu

It can grow up to 12 centimeters per day if conditions are right; you can weave baskets from it; and

You can eat it! with nutrition!

Nutrients - Per 100 grams.   Note: 4 ounces = 113.40 grams

Basic Components
Calories  - 345                     
Protein  - 21.85 g                     
Carbohydrates  - 61.14 g                     
Dietary Fiber - 48.4 g
Sugar-Total - 1.96 g                     
Fat-Total - 1.48 g                     
Saturated Fat - 0.14 g                     
Cholesterol - 0 mg               
Water - 6.22 g               
Ash - 9.31 g                     
Calories from Fat - 13.32                     

Vitamins
Vitamin A   - 14600 IU                     
Vitamin C   - 3.13 mg                 

Minerals
Calcium - 1700 mg                 
Iron - 11.6mg                     
Potassium - 1950 mg                                         
Sodium  - 9 mg

Is this thinking "outside the box" or what?

One more thing - - the purple flowers seem rather pretty. But then again I do not live in the southeastern United States.

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#49 2003-10-22 06:46:04

TJohn
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Registered: 2002-08-06
Posts: 149

Re: Growing plants on Mars

I had forgotten about kudzu.  I grew up in the southeast and remember that stuff covering old houses.  I wonder, if it is able to be grown on Mars, would it grow just as fast.  I did not know that you could eat it.  Very good idea!


One day...we will get to Mars and the rest of the galaxy!!  Hopefully it will be by Nuclear power!!!

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#50 2003-10-22 13:18:29

Palomar
Member
From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Growing plants on Mars

*Bill, wow.  smile  I've never heard of kudzu before.

Lots of nutrients in it; seems a little heavy on the carbs, though.

Purple flowers, huh?  You know, wine and even jellies can be made from some flowers (dandelions, for instance).

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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