Terraforming - Worth the effort?

Antius · 2007-10-31 02:25:20

Given the recent advances in genetic engineering and the use of algaes and bacteria in the production of synthetic fuels, the idea of terraforming may eventually be obsolete, long before we become capable of putting it into practice. Human beings will be capable of efficiently producing sufficient amounts of food from algae and bacteria, using artifical energy drawn from atomic sources. In addition, some proteins, sugars and vitamins could be manufactured entirely chemically. With enough skill, these methods could eventually produce food that is physically indistinguishable from that which we enjoy today.

This has huge implications for future human colonisation of space. Instead of requiring large fields dependant upon sunlight, food production would take place within relatively tiny and compact chemical plants. Land vegetation such as trees and plants would then be maintained purely for aesthetic purposes and the small amounts required, could easily be illuminated using synthetic energy.

What this effectively means for space colonisation is that humna beings can effectively colonise any world with sufficient raw materials. Limitations such as sunlight and low surface temperature, would no longer have any bearing upon the habitability of a world, given that all energy is derived from artificial sources, fission and fusion. Under these conditions, Pluto would be no less habitable than Mars. The moons of Jupiter become hot property because they combine an abundance of raw material with relatively high surfcae gravity.

Martian Republic · 2007-11-03 17:31:19

We would still engage in a terraformation process, because of who we are as humans and what should be motivating us to go into space in the first place. We would still want to terraform Mars and make it as much like Earth as we can possibly make it. There more to life than just eating food or drinking water or just breathing the air of habitat for minimum living requirements of living in space that we can get. We would want to make space home for us, which would require us to terraform Mars so we could walk through a Martian forest sometime in the next two to three hundred years or so in the future. It is also the quality of life that we are interested in having when we move into space to live and not just the minimum requirement to just get by if we choose to live in space that we are also looking at.

Larry,

Tom Kalbfus · 2007-11-04 10:47:43

Terraforming Mars and other places is a means to an end. Just like we chop down trees and build houses with its wood. The point is not to create a house for its own sake, but to create a place for somebody to live.

I think we should terraform Mars because it is there, it is raw material for a home we can make out of it, if we don't do that it is a waste of material. Forests and parks are of significance only because they can be appreciated by human eyes. I'll bet you that somewhere in the Universe is an alien planet with its own forests, and animal life but devoid of any intelligence capable of appreciating it. Of what value are forests we'll never see? Someday an intelligent civilization may develop on that planet, or perhaps that's planet's sun will go through its life cycle without any human-level intelligent life ever evolving there, nothing is inevitable after all.

We terraform Mars for ourselves, we aren't doing Mars any particular favors. If we don't terraform Mars, Mars will simply stay as it is. Mars is raw material for whatever we make out of it.

Antius · 2007-11-05 05:42:12

We would still engage in a terraformation process, because of who we are as humans and what should be motivating us to go into space in the first place. We would still want to terraform Mars and make it as much like Earth as we can possibly make it. There more to life than just eating food or drinking water or just breathing the air of habitat for minimum living requirements of living in space that we can get. We would want to make space home for us, which would require us to terraform Mars so we could walk through a Martian forest sometime in the next two to three hundred years or so in the future. It is also the quality of life that we are interested in having when we move into space to live and not just the minimum requirement to just get by if we choose to live in space that we are also looking at.
Larry,

I am aware that there are numerous aesthetic reasons for terraforming Mars (and other worlds), such as the desire to walk under open sky, walk through living forests, etc.

My point was that full colonisation could take place and probably will take place of all the solid worlds of the solar system without the prerequisite of terraforming. It simply won't be neccesary as a prerequisite of human habitation. We can make all of the food, air and entertainment that we need without terraforming the entire planet. Ultimately, human settlements will probably be extremely compact and capable of meeting all of their food resource needs using very compact equipment. The only imputs that the settlemnet will require from its environment will be Uranium/Thorium/Deuterium, for its energy sources and raw materials to makeup for any innefficiencies in its recycling systems.

If terraforming takes place it will be for largely aesthetic reasons and by the time it does take place, Mars and the other worlds will already be heavily populated.

Terraformer · 2007-11-08 13:19:07

And if you terraform it you don't have to rely on tech to keep you alive (eg. if all the power goes you can still survive without energy hungry life support.)

Antius · 2007-11-09 06:43:53

And if you terraform it you don't have to rely on tech to keep you alive (eg. if all the power goes you can still survive without energy hungry life support.)

We all depend upon technology to survive - for water, food production, shelter, transport of goods, waste treatment, etc. Without that technology, life for most of the human race living today, would be as impossible as it is on the moon.

But this largely misses my point. My point was, that by the time we get to terraforming Mars, it will already be heavily colonised by human beings who:
1) Do not need a terraformed planet in order to survive;
2) Do not wish to endanger their environment with the sort of massive global changes that terrforming would entale;
3) May have everything that they really want and need within the boundary of their habitats.

On this basis, terraforming would be largely cosmetic as far as these people were concerned. It would be both expensive and risky to the existing inhabitants and would neccesarily be a long term project, which may not make much difference to the planet's ultimate holding capacity.

If we consider other worlds like the moons of jupiter, saturn, ceres, Triton, Pluto, other TNOs, etc, terraforming becomes even more marginal due to the high cost of such things as artificial illumination and the high-column density of the atmosphere required to produce breathable air on low-gravity worlds.

All things considered, most of humanity living 1000 years from now, are likley to reside in artificial habitats, not terraformed worlds, with food, clothing, manufactured goods, etc, all derived synthetically from artificial energy sources. They will have plants and animals largely for cosmetic reasons, but their food and virtually everything they need to survive will be derived from artificial energy sources. The further you are from the sun, the stronger this arguement gets.

I would expect that a heavily populated Mars, would differ little in its fundamental characteristics to the world that we see today. The atmosphere may be marginally thicker, as waste heat from the many thousands of habitats raises the average surface temperature and results in outgassing from the regolith. But human presence would not be immiediately obvious, because habitats would be generally very compact and shielded against cosmic rays by Martian regolith. All food production would take place within compact chemical plants within the habitats, so there would be no obvious signs of agriculture or other tell-tale signs of human presence. Only the plumes from fusion reactor cooling towers would betray the presence of human life.

A heavily populated outer planet moon or TNO, would not show significant visible signs of life, although its average surface temperature would generally be higher than one would expect from sunlight alone, again due to waste heat from habitat fusion/fission power sources. As water is used to remove waste heat from habitat fusion reactors, there would probably be a thin, transient atmosphere of water vapour, which would snow-out on the surface.

Tom Kalbfus · 2007-11-09 09:12:08

Artificial habitats require greater maintenence than a whole planetary system with biofeedbacks. I think people will want to get out of their domes every once in a while. I think people who want to live in closed spaces will live mostly in free space, not on planetary surfaces. I think people will terraform Mars in order to have a recreational park, and so as to relieve the burden on Earth for supporting such a function. Mar's near Earth rotation rate makes Mars an ideal subject for such a project. Otherwise people will live in rotating habitats in orbit. Mars 1/3 gravity may prove detrimental for long term human health, an O'Neill habitat will provide the equivalent of one Earth gravity, and people on their time off can bounce around in the tall forests of a terraformed Mars.

O'Neill colonies will in the meantime give them plenty of "outside" in the meantime, though I think some of the smaller habitats will be greenhouse-like and echo like catherdrals.

RickSmith · 2007-11-12 22:38:57

We all depend upon technology to survive - for water, food production, shelter, transport of goods, waste treatment, etc. Without that technology, life for most of the human race living today, would be as impossible as it is on the moon.
But this largely misses my point. My point was, that by the time we get to terraforming Mars, it will already be heavily colonised by human beings who:
1) Do not need a terraformed planet in order to survive;
2) Do not wish to endanger their environment with the sort of massive global changes that terrforming would entale;
3) May have everything that they really want and need within the boundary of their habitats. ...

Hi Antius, everyone.
I agree with what you say about us requiring life support now. I also agree with point 1 above.

But as for 2, my question is "what environment?" If there is no life who cares about the Martian environment? The solar system is filled with lifeless rocks. After you have spent a few years in a lifeless environment, I suspect that giving Mars a biosphere will look pretty darn attractive.

As for your #3, the reason will be many people will want a world that won't kill their kids at a drop of the hat and there will be economic incentives to do so.

Mars is so cold it is dangerous and expensive. If we add greenhouse gases it will warm up making it cheaper to live.

Mars is a near vacuum which is dangerous and expensive. If we thicken the atmosphere it is safer and cheaper to live. Greenhouses in particular get a lot cheaper if Mars is not a near vacuum.

Mars has so much UV that it is dangerous and expensive to protect against. If we add a small amount of O2 we get an ozone layer for radiation protection.

Now all of these steps run into the free rider problem, but it could be argued that the free rider problem is the real purpose of governments. It is true that terraforming is so long term that it will always seem like it is not worth the while. But it is a job that inspires men's souls and I can see people devoting their lives to moving the project forward.

Warm regards, Rick.

Tom Kalbfus · 2007-11-13 01:16:23

I see the Earth, Mars, and even Venus becoming "planetary parks" for people living in the Solar System in mostly O'Neill type habitats. People will go to Earth, Mars, and Venus on their vacations. These planets will be used as a source for growing organisms that will later be shipped to O'Neill's. Earth is fairly fool proof when compared to an artificial habitat. Earth, after all doesn't require walls to hold in its atmosphere, and the planet's environment doesn't need a whole lot of maintenance just so long as we leave it alone. That said, an Earth gone wild would make a fun tourist attraction and camp ground for a human population that mostly lives in space.

Venus is an interesting case. I saw a show on the history channel called "How the Earth was Made" It seems that at one point in its history, the Earth was alot like Venus, it too had a crushing atmosphere that was mostly carbon dioxide, and it had little or no water, but water later arrived from space in the form of comets and icy hydrous asteroids. Earth got fairly peppered with these things in the Early Solar System, mostly within the first 100 million years, and an ocean accumulated on Earth, and it boiled away on Venus. I think we can do the same to Venus as had happened to Earth. If we shade Venus just a bit, and pepper it with comets from the Kuiper Belt and Oort cloud, we can accumulate an ocean on Venus, and as was discussed on how the Earth was made, water will seep into the cracks on Venus and mix with the molten rock forming granite, which is lighter than basaltic rock, it will rise to the top and form continents. Stromalites will form and produce oxygen, turning the iron rich oceans from green to blue. This process, the way it occurred on Earth took millions of years though. But I think Venus ought not be neglected simply because it is there, and its not really much good for anything else. As a source of material for building stuff in space, it really sucks because of its gravity. It is easier to obtain material from the asteroids, and it is easier to travel to other star systems than it is to disassemble planets for their materials.

Antius · 2007-11-13 02:16:02

We all depend upon technology to survive - for water, food production, shelter, transport of goods, waste treatment, etc. Without that technology, life for most of the human race living today, would be as impossible as it is on the moon.
But this largely misses my point. My point was, that by the time we get to terraforming Mars, it will already be heavily colonised by human beings who:
1) Do not need a terraformed planet in order to survive;
2) Do not wish to endanger their environment with the sort of massive global changes that terrforming would entale;
3) May have everything that they really want and need within the boundary of their habitats. ...
Hi Antius, everyone.
I agree with what you say about us requiring life support now. I also agree with point 1 above.
But as for 2, my question is "what environment?" If there is no life who cares about the Martian environment? The solar system is filled with lifeless rocks. After you have spent a few years in a lifeless environment, I suspect that giving Mars a biosphere will look pretty darn attractive.
As for your #3, the reason will be many people will want a world that won't kill their kids at a drop of the hat and there will be economic incentives to do so.
Mars is so cold it is dangerous and expensive. If we add greenhouse gases it will warm up making it cheaper to live.
Mars is a near vacuum which is dangerous and expensive. If we thicken the atmosphere it is safer and cheaper to live. Greenhouses in particular get a lot cheaper if Mars is not a near vacuum.
Mars has so much UV that it is dangerous and expensive to protect against. If we add a small amount of O2 we get an ozone layer for radiation protection.

Now all of these steps run into the free rider problem, but it could be argued that the free rider problem is the real purpose of governments. It is true that terraforming is so long term that it will always seem like it is not worth the while. But it is a job that inspires men's souls and I can see people devoting their lives to moving the project forward.
Warm regards, Rick.

RickSmith,
If you look at the previous postings, you will see that these points are answered.

People will not need greenhouses to produce food. Microscopic water-bourne plants (algae), yeasts and edible bacteria can produce food that is as nutritious and tasty as that which we enjoy today. This can be done using artificial energy sources and the plant required is extremely compact and will not need any sunlight.

Human beings will live within compact settlements, under pressurised plastic domes. UV will not be a problem under the domes and on the rare occasions when they need to venture outside, the colonists will wear environment suits, protecting them from the UV, the cold and vacuum.

The cold will not be an issue within compact settlements. They will be heated using waste heat from their power supplys and will generate ample internal heat from equipment and their inhabitants bodies.

The settlements will not need extensive amounts of land based plants for food supply and will keep them purely for aesthetic purposes. As I said before, food can be produced in very compact volumes using algae, yeasts and bacteria.

At no point will a terraformed planet be neccesary for survival. the only thing that the colonists would actually need from mars is raw materials and a stable environment. In fact, once mankind has mastered fusion power and synthetic food production, Pluto would be every bit as colonisable as mars, in terms of environment and resources.

RickSmith · 2007-11-13 04:20:04

People will not need greenhouses to produce food. Microscopic water-bourne plants (algae), yeasts and edible bacteria can produce food that is as nutritious and tasty as that which we enjoy today. This can be done using artificial energy sources and the plant required is extremely compact and will not need any sunlight.
Human beings will live within compact settlements, under pressurised plastic domes. ... <SUMMARY: UV, cold & vacuum won't be an issue.>
At no point will a terraformed planet be neccesary for survival. ...Pluto would be every bit as colonisable as mars, in terms of environment and resources.

Hi Antius,
Bacteria and yeast are anaerobic so if you want oxygen you need photosyntheses. And photosyntheses whether done by crops or plankton is very inefficient. It requires a gigantic amount of energy. I consider it, very, very likely that people will take advantage of the free light from the sun to reduce this energy cost. So unless you postulate that the energy is so cheap that it is not worth building windows then I think we will have greenhouses.

You might want to read "Terraforming: Engineering Planetary Environments" by Fogg. In Chapter 2 he looks at the stability of closed life support systems. Basically he shows that the larger the ecology, the slower it reacts to permutations. I reproduce a chart from page 55:

BIOMASS TO ATMOSPHERE MASS RATIO (Normalized so Earth will be 1:1)

CELSS "Breadboard"........................................... 2000:1
Bios 3.................................................................. 1000:1
Biosphere 2........................................................... 350:1
Stanford Torus....................................................... 250:1
O'Neill Island 2......................................................... 20:1
Bernal Sphere.......................................................... 13:1
Martian "Worldhouse"................................................ 7:1
Earth......................................................................... 1:1
Terraformed Mars....................................................... 1:2.7

All of the above are theoretical except the CELSS "Breadboard" (which failed) Earth (working) and Biosphere 2 (which failed).

The only stable biosystem we know of is Earth. Biosphere 2 is the largest attempt to build an independent self sustaining biosphere and it was wracked by instabilities and problems. The food plants produced too little food in part because they overestimated how much light they would get from the desert sun. Carbon dioxide production (by animals) so greatly exceeded the production of O2 by plants that carbon dioxide scrubbers had to be installed. (Another reason for low food production was that broad mites were not properly kept in check by predators and ate too much of the food.)

There were many other problems with Biosphere 2 (concrete absorbing CO2, biological matter rotting and absorbing O2, air conditioning problems in keeping this giant green house cool, etc.) It makes very interesting reading.

I consider Biosphere 2 to be a huge success as an experiment. It showed just how hard it is to create a independent biosphere. We should respect the one we have; it is precious and very rare.

If we postulate that you have very, very cheap power and a perfect biosphere that does not need sunlight (so it works equally well underground or on Pluto) then your point is made. However, I expect we will have largely terraformed Mars before that happens. You feel that a closed ecology is easy to create; I don't. Perhaps we should agree to disagree?

Furthermore, a plant sized biosphere is attractive for more reasons than just aesthetics. In a small colony with a high power life support life is totally dependent on technology. One dark age will end life. Tiny life support systems will also concentrate political power. You will have 'hydraulic empires' unlike history has ever known.

So in answer to your original question: "Terraforming - Worth the Effort?" I think the answer is yes, at least until we see a Biosphere 2 or something that is able to close the ecological cycle. I LIKE ecosystems that are independent of technological intervention.

Warm regards, Rick

Antius · 2007-11-13 06:48:02

Hello Rick,
Excellent post and many thanks for the reference to Martin Fogg's paper.

There would appear to be 2 issues with the idea of human settlements based upon artificially powered CELSS. The first is the cost of energy needed to produce food and oxygen, the second a stability issue, which is common to all small enclosed eco systems. I agree that there are many difficulties contributing to both problems. I will attempt to answer the first complication first, can we economically produce food from algae, using synthetic energy?

Rough screening calculation:

Assumptions: (1) cost of large-scale thermonuclear electricity is $0.02/kWh (2) Basic photosythetic efficiency of algae in natural sunlight is ~5% (3) LED lightsources are able to tailor the frequency of the light precisely, so photosynthetic efficiency with LEDs is roughly double that of natural sunlight (4) LEDs are roughly 20% efficient.

Human beings consume ~2500 calories per day in food energy, which equates to 1000kWh/year of food energy.

How much electricity is needed to grow enough synthetic food to feed 1 person?:

E = 1000/(2 x 0.05 x 0.2) = 50,000kWh/yr.

How much would the electricity cost?

cost = 50,000 x 0.02 = $1000/yr

This is the cost of the electric power. Total costs will include the cost of the plant in which the food is grown and downstream processing of the algae into palatable food. So lets assume that total cost is rough double the power cost at $2000/person/year.

Present US GDP per capita is $43,223/yr. If our colony is only able to achieve this level of income, food will still account for <5% of total spending.

The second problem is the instability of small ecosystems. From what you have told me, large ecosystems tend to be more stable because the massive volume of air serves as a buffer against any sudden changes in atmospheric gas concentrations. The higher the ratio between air volume and biomass, the more stable the system is. There would appear to be two principle problems (1) Too much or too little O2 (2) Too much or too little CO2. This would only appera to be a problematic if we are assuming that the ecosystem is perfectly closed, ie, assuming that no gas is allowed to enter or leave the system. How difficult would it be to have a chemical plant on standby, which could manufacture additional oxygen or pump in CO2 from the Martian atmosphere, as required?

The raw material required is Martian air, which would seem to be available in infinite quantities and can be harvested using a simple pump. On a world like Pluto, our atmospheric raw materials would initially come from frozen ices. Here, we would probably want to keep any vented O2/CO2 in buffer tanks.

Antius · 2007-11-13 07:17:38

Soylent Green, anyone?

RickSmith · 2007-11-13 19:37:49

Hello Rick,
...(2) Basic photosythetic efficiency of algae in natural sunlight is ~5%
...
The second problem is the instability of small ecosystems. From what you have told me, large ecosystems tend to be more stable because the massive volume of air serves as a buffer against any sudden changes in atmospheric gas concentrations.

Hi Antius, everyone.
That 5% figure sounds wildly optimistic. Do you have a reference for it ?

EDIT: The figures I was thinking of were discussing conversion of light into biomass on Mars and NOT talking about the efficiency of photosynthesis itself. I have been doing some research and 5% seems totally possible for algae. (Natural ecosystems usually run from 0.5% to 2% efficiency. I could easily see some species of algae reaching 5%.)

As for the stability of ecosystems, Fogg was not saying the air volume was the key problem. He was suggesting that small ecosystems were less stable than large ones. I think that he picked the air volume to biomass ratio because it was something he could use even for theoretical habitats since they had published their volumes and the size of the biomass could be estimated.

But, if your air is going out of whack, it is nice if it has enough volume to buy you some time to fix it.

Warm regards, Rick.

RickSmith · 2007-11-14 02:41:22

Assumptions: ...
Human beings consume ~2500 calories per day in food energy, which equates to 1,000 kWh/year of food energy.

Hi Antius,
I checked this. ~2,356 kilo calories / day almost exactly equal 1,000 kWh/year. (Workings shown below.) Close enough for government work.

I did more research and Bios 3 was a life support experiment in the USSR. It did not get to the stage of being a closed biosphere but it did recycle 30 to (eventually) 70% of the crew's food. They eventually reached 6 month duration before trace element loss became a major concern. Anyway this was not a theoretical ecosystem, it was an actual experiment.

Some more from Fogg:
(pg 52) "Realistically, it seems that such systems may always fall short of the ideal, simply because it may be impossible to scale down the volume of the Earth's biosphere by a factor of >10E13 and adequately maintain all its functions. ..."

(pg 54) "Another consequence of low volume is that the dynamics of the contained biosphere are poorly buffered. This means that the biota are connected with a much smaller reservoir of biogenic materials than on the Earth. Such materials therefore, as a proportion of their abundance, have to cycled through the biota at a much faster rate. ..."

He goes on to describe how Biosphere 2 had to cycle ALL of its CO2 in just a few days. There were 600 ppm variations in CO2 between day and night. He goes on to say,

(pg 54) "... This faster pace of change has the effect of making the system intrinsically less stable. Minor imbalances significantly affect the composition of the buffer in a short period of time. Any habitable equilibrium must therefore be extremely precise as these imbalances could run away very rapidly. The less-than-total predictability of the dynamics of the ecological systems may make achievement of such a fine balance very difficult, especially as natural stabilizing biotic responses that function with in the vast and massive biosphere of the Earth may be too slow or inoperable in a confined space. Once the buffer has changed to the extent that the biological function is endangered (e.g. by levels of CO2 falling too low or rising too high) the system is in danger of crashing completely."

(Emphasis his.)

He goes on and discusses all the tasks that technological life support must do that we get for 'free' from our biosphere. (This cost is measured in energy consumption.) For example, Biosphere 2 had to pay energy for:

- External structural maintenance teams.
- Fans to circulate air.
- Temperature regulation system.
- Dehumidifiers in basement air coolers.
- Pumps to circulate water.
- Misting machines for 'rainforest' cloud.
- Desalination system to maintain fresh water reservoir.
- Algae scrubbers to transfer water between 'salt marsh' and 'ocean'.
- Wave machine to oxygenate 'ocean'.
- Soil bed reactor to neutralize trace contaminants in air.
- CO2 scrubbers (unplanned).
- Emergency oxygen injection system (unplanned).
- Compost machine for rapid recycling of inedible plant waste.
- Monitoring systems.

In Table 2.6 he lists human power consumption & compares it to Earth and contained biospheres.

EARTH (WITH GRATIS LIFE SUPPORT)
------------------------------------------------------------------------------------------------------
World average primary power................................~ 2kW / person
World average electric power.................................~0.2 kWe / person

Industrial nations primary power............................~6 kW / person
Industrial nations electric power.............................~0.7 kWe / person

EXTRATERRESTRIAL ESTIMATES:
------------------------------------------------------------------------------------------------------
EC/LSS only (stored food).......................................~2 kWe / person
Stanford Torus Space Settlement...........................~3 kWe / person
CELSS only (hydroponics w/ fluorescent light)......~15 kWe / person
Ohbayashi Mars Colony 2057
(Total power for all activities)................................~50 kWe / person

Biosphere 2........................................................~100 kWe / person

Quoting Fogg again:
(pg 58) "A particularly worrisome feature about table 2.6 is the power consumption of the one working model of a biosphere habitat, Biosphere 2, which requires a huge ~100 kWe / person to operate, ..."

(Its power requirements were so great that they had to build a power plant on site to pay for this energy. The electrical energy was actually ~1/2 that which was supplied by the sun over its area.)

He then goes on to point out that larger ecological containers than Biosphere 2 will not have to pay all these costs. If you have a big enough biosphere that you have a natural weather cycle you don't need to worry about wave machines and weather simulators for example.

Anyway, this is food for thought.

Kim Stanley Robinson has written a novel called "Icehenge" where a key plot point in the early part of the book is the difficulty in closing a life support system. You might find it interesting.

Warm regards, Rick.

Math Appendix:

// Human beings consume ~2500 calories per day in food energy,
// which equates to 1000kWh/year of food energy.

Checking this:
You say that humans need ~2500 calories / day. These are of course, kilo-calories. 1 k Calorie = 4,184 Joules.

So 4,184 J / kCal * 2,500 kCal (per day) = 10,460,000 J (per day)

1 kWh= 3.6e6 J (a kilowatt hour is a measure of energy so this is correct).

(Power = energy / time so: power * time = energy)

10,460,000 J (per day) / 3,600,000 J/ kWh = ~2.91 kWh (per day)

2.91 kWh / day * 365.25 days / year = 1,061 kWh / year

So:
2,500 kCal / day / ((1,061 kWh / year) / (1,000 kWh / year)) =
= 2,356.27 kCal / day

Antius · 2007-11-14 06:29:58

Thanks Rick.

Many thanks. Some interesting material you have provided, which highlights the difficulty of attempting to create a trully closed system.

On Mars, the situation will perhaps be a little easier (easier in some respects than on Earth) for the simple reason that we would have a convenient and infinite reservoir of CO2, which can be compressed into the habitat if CO2 levels drop, or processed in a simple Sabatier reactor to produce oxygen, if O2 levels drop.

The whole process is critically dependant upon power supply. Food production would be less of an issue given that it can be stockpiled in large amounts. Gas balance is clearly a more significant problem and is dogged by a positive feedback effects which would appear to make active control an absolute neccesity, especially in small systems.

the system that i had in mind would have human beings on one side of the equation and tanks of artificially lit algae on the other. The temperature of the algae tanks would be precisely controlled, as would the nutrient content of the water. Both can be measured in real time and kept within narrow limits. Atmospheric CO2 would pass into the algae either by bubbling air through the tanks or by feeding in neat CO2. the only other variable is light levels.

On Mars, the food production element could actually be decoupled entirely from the atmospheric regulation system. For example, the atmosphere of the colony could be provided by a sabatier reactor with Martian atmospheric CO2 as a feedstock and the algae food-producing tanks could be fed with compressed martian CO2 with the O2 waste product venting into the atmosphere. In reality, it will be more energy efficient to maintain some degree of closure, recycling biologically produced oxygen into the habitat.

The key point here I suppose is that the system is at no point completely 'closed'. It continuously exchanges gas with the Martian atmosphere and would probably need to import trace elements from Martian soil as well. The system also depends critically upon artificial power and mechanical systems for the survival of human life. The systems maintaining the atmosphere would therefore need a very high degree of reliability and redundancy. The food production system would be less critical, given that the system could presumably be buffered to allow a repair time measured in years.

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