Minimal Martian Terraformed Atmospheres

RickSmith · 2007-11-18 03:55:55

Hi Everyone,
This thread is intended for a detailed discussion of what would be a minimally useful change to Mars. My hope is that as people find more data we can refine this estimate.

*** IF YOU ARE UP ON THE STANDARD TERRAFORMING IDEAS YOU CAN SKIP DOWN TO THE BAR OF ASTERISKS ***
For newcomers: it has been thought that if we can warm the poles of Mars by 4 degrees C that all the solid carbon dioxide will sublime. Being a greenhouse gas this will warm the planet. Eventually more carbon dioxide will start coming out of clay minerals in the soil (which when cold can hold 8% CO2). Some ice can have CO2 in its crystal structure. (These are called clathrates.) Mars likely has a huge amount of CO2 clathrate and if a significant amount of this melts even more CO2 will join the atmosphere. Mars could end up with a 'permanent' (millions of years) warmer, higher pressure atmosphere.

Mars seems to have two stable climates. When its atmosphere is thick it is much warmer (tho still below freezing). However, usually Mars is in the current cold, thin atmosphere climate. Large volcanic eruptions are believed to in the past have lead to MEGAOUTFLO events (Mars Environmental Glacial Atmospheric OUTburst FLood Oscillations). During these periods the planet is warmer, there may have been frozen seas or lakes and a lot of snow and frost was deposited in the southern regions of the planet. (Mars likely never has had rain but it may have once had snow. Currently it just gets frost.)

The hope is that with relatively small changes to the planet, we can kick it over to the warmer higher pressure phase of its climate.

This can be done by using solar mirrors to warm the poles (especially the south pole), adding super greenhouse gases (especially perfluorocarbons) to the atmosphere and dropping comets or icy asteroids (iceteroids) on the planet to release atmospheric gases. There are other ideas to accomplish these goals but these ones do not require any new science, just engineering.

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Creating a Martian atmosphere that is breathable is very difficult. However there are 3 intermediate steps which would be useful.

1) Evaporate the polar CO2 ice and release enough CO2 in the soil / clathrates to allow humans to move about with out pressure suits. This much pressure will also give very significant radiation protection against solar flares and cosmic rays.

2) Add enough nitrogen that plants that can fix nitrogen from the atmosphere can survive.

3) Add enough oxygen so that a ozone layer forms. This would cut down UV radiation and perhaps slow the loss of hydrogen from the top of the atmosphere by preventing photo-disassociation of water.

In the posts below I will give what I believe to be the smallest, easiest changes that would fulfill the goals above.

Where I have questions, I will highlight them. My hope is that if many eyes keep a lookout for this data we might be able to fine up these estimates. If you discover some data, please give references to where you find it!

If anyone else has ideas to cheaply improve the suggested mix below, don't hesitate to speak up.

Warm regards, Rick.

RickSmith · 2007-11-22 05:27:33

I think that we will likely want to have a soletta reflecting heat to both poles. Simply, the poles are where we really need some heat where as greenhouse gases are make things warmest where the sun is. As the Martian atmosphere thickens it will be better at moving heat around.

Dr. Zubrin estimates that a mirror 125 km in diameter would be by itself enough to increase the temperature at the south pole 5 degrees. The mass of this is about that of a super tanker and their is plenty of aluminum on Luna. If we build it in Earth orbit it will be cheap to move it to Mars, it can act as a solar sail.

However, I think that we will want more than just a 5 degree increase in temperature. Since the Case for Mars has been written, it is clear that there is not as much frozen CO2 in the polar caps as hoped. (They are almost entirely water ice.) This means that if they sublime, they won't give as much pressure and warming as hoped. The warmer the better since the higher the temperature, the more CO2 will be released by the soil and clathrates. Also, the warmer it is the faster the new warmer temperature will work its way into the soil.

Let us say that we wish to have a 5 degree warming in addition to the mirrors.

Zubrin and McKay suggests that for +5 degrees we will need a partial pressure of 0.012 micro bars of PFC's. This will require 260 tonnes per hour to be created for 20 years (with a cost of 1,310 MWe (Mega Watts electric) to refine the ores and produce these gases. This would require several thousand workers (mostly miners) and a dedicated power plant but is certainly doable if we have native industry.

Each gas has some wavelengths of heat that it absorbs best and others were the heat can escape easily. Having a mix of gases means that the weaknesses in one can be covered by others. So we will certainly want a variety of these gases.

What would be a suitable mix of gases? See this article:

New data on Greenhouse Gases.

In Marinova, McKay's & Hashimoto article they suggest that 0.2 Pascals are needed of their mix. This is 0.00,000,2 Pascals or 2 micro Bars. However, they are assuming that their is NO mirror, and that with 2 microbars enough heat will percolate down to the pole to start a run away green house event.

In the new study Marinova, et all, suggest that to produce the 2 micro bars it will require the production of 25,700 times the Earths yearly production to reach this value. (Since the break down of these gases is so low their is no reason that this amount could be spread over a period of time. They suggest 50 years.) However, assuming that McKay and Zubrin's numbers are correct, you would reduce the amount of greenhouse gases needed by about 17 times if you put up a soletta as well.

In any case I think we will want a soletta. Mars is cold and even if we get liquid water on the surface, it will evaporate and migrate to the poles. We will have a true desert on the equator and the areas most hospitable to life. If we have a large mirror warming the south pole all winter, then that snow and ice is much more likely to melt (or at least flow as a glacier) and eventually return to the equatorial areas where the humans and their plants are.

As for how much CO2 will be released if we warm the planet 10 to 20 degrees, this is hard to tell. The numbers in the case for Mars are too optimistic I think. (Or rather I think the numbers are realistic but it will take much longer than McKay and Zubrin thought for that much gas to leak into the atmosphere.)

When Zubrin wrote "The Case For Mars" it was thought that Mars had much less water than we do now, and that the South Polar Cap was mostly CO2. We now know that it is mostly water ice.

So when the runaway greenhouse event occurs, we will certainly get enough CO2 to reach 14 or 15 mBars with in months (this is how much its normal pressure varies). It will likely increase more over the next decade or two but I have not been able to find good numbers on how much. After that, there may be a long slow rise.

The greenhouse gases will gain a 30% effectiveness boost when they are in CO2 rather than Ar. And all this gas itself is a greenhouse gas. So it is likely that the temperatures at the poles will increase by 20 C or more. This might be high enough to reach the temperature of desorption (the temperature where much of the CO2 will outgas from clay soils). If not, we will need a northern polar soletta or a few more years of greenhouse gases.

Assuming that the CO2 starts coming out of the clays, the temperature will slowly rise as the pressure increases. However, this higher temperature will have to work its way down into the soils which is a slow process. You will get a rapid increase of 10 to 20 mBar in the first decade and it will slowly drop off as the wave of thawing moves more and more slowly.

Another location for CO2 is in ice. CO2 saturated water will form clathrates where the ice has CO2 in its crystal structure. Clathrates have lower melting temperatures than ice so they will break up sooner than normal ice. However, Mars would still be 40C or so below freezing so freeing up the CO2 in the clathrates will be a very slow process. To speed it up we could darken Mars' poles with black dust, drop a few small asteroids on it or just be very patient.

Anyway, my feeling is that the pressure of Mars will pop up to ~50 mBars partial pressure of CO2 and then slow, (tho continuing to rise for centuries as more CO2 leaks out of the ices and crevasses.)

So eventually we have gotten to my estimate of the composition of a first stage Martian Atmosphere some 20 to 50 years after significant production of PFC's and the addition of a large soletta over the South Pole:

Composition:
- CO2.....50 mBar
- N2..........0.12 mBar
- Ar...........0.095 mBar
- O2..........0.012 mBar
- H2O.......0.0025 mBar (rising with increasing temperature.)

- Various trace gases ~0.001 mBar

- C2F6.....0.00003 mBar
- C3F8.....0.000125 mBar
- C4F10...0.00001 mBar
- SF6........0.000045 mBar
- NO2.......0.00001 mBar

Total: 50.23 mBar.

I've not been able to find if the human skin can take 50 mBar of pressure with out a pressure suit. However, it CAN take it with a suit that 'hugs you close' e.g. a spandex like material reinforced with Teflon fibers and the like. In another 50 to 100 years, the pressure would like rise to around 100 mBar and you could walk around in shirt sleeves and gas mask.

I've had to guess more than I like in this post. I'll correct and update these numbers as I find more information. But I think it likely that even with very conservative assumptions, Mars will have a high enough pressure for humans with gas masks within 100 years after the South Pole subliming away the CO2.

Warm regards, Rick

RickSmith · 2007-11-25 23:00:20

Hi everyone,
The next stage of terraforming needs to increase the nitrogen partial pressure. In many ways, argon would be a suitable buffer gas and I certainly would not mind seeing more argon from comets and the like. But nitrogen has one big advantage over argon, it needed by plants.

The second stage of engineering a minimum atmosphere is to increase the N2 level to 0.5 kPa. This is high enough that nitrogen fixing bacteria (in the roots of some plants) can fix the nitrogen. (This means that the N2 is broken up into a variety of nitride ions which plant and animal tissues can use.)

Now I've argued elsewhere that the high concentration of argon in the atmosphere suggests that Mars has NOT had massive impacts which have knocked off its atmosphere. If it had, the argon would have been lost as well. But the concentration of argon suggests that Mars originally had a dense atmosphere with a normal mix of gases (including a LOT of nitrogen) and gradually lost most of its air, leaving the argon behind.

Where has the N2 gone then? It is unlikely to have lost it to escape to space. With a gram molecular mass of 28, N2 is plenty heavy to stay on the planet. I think it more likely that lightning in Mars atmosphere has turned the nitrogen into nitrates which react with the soil. (This happens on Earth, but the nitrates are absorbed and used in the biosphere and then returned to the atmosphere.) See:

The Biological Nitrogen Cycle

Given that there is likely to be nitrate deposits on Mars, (none have been found so far) how can these be released back into the air?

Well, some bacteria can bore into rocks and release the nitrogen. However this is SLOW, requires a fairly healthy bacteria population and won't work on deeply buried nitride deposits. If we didn't mind terraforming taking hundreds of thousands of years this might be enough.

Fogg suggests using thermonuclear bombs to shock the rocks into releasing nitrogen, CO2 and melting water. (His H-Bombs are not fission bomb triggered so they would produce almost no radioactive fallout.) I suspect that these methods will be used by Martians especially to get water to the surface quickly.

The last method is to drop comets or iceteroids on Mars. (Iceteroid is a term invented by James Edward Oberg in his book New Earths.) This has two advantages. First they will bring more volatiles to Mars which is always welcome. Second by dropping them on Nitrate beds, you can free the nitrogen in the rock as well as adding what ever nitrogen is in the comet itself. Conservatively, (assuming a rich nitrate bed) the amount of N2 generated would be twice what the comet holds itself.

I keep meaning to do the research to allow me to write an article to show a magsail based iceteroid mission to bring ~500 meter sized iceteriods to Mars. (Finding the numbers is slow, the calculations are straightforward). Anyway, I feel that it is affordable to drop a fair number of iceteriods on Mars. Let us assume that this is done. What would our atmosphere look like?

Well, we may be able to find bodies that are 5 to 10% ammonia in the outer solar system. These bodies will likely have a lot of water ice, some CO2, some CH4 and maybe 5% rock and soot like substances in them.

So if we assume that we increase the N2 partial pressure to 0.5 kPa (up from the current 0.0175 kPa) using 50% asteroids and 50% thermonuclear bombs then this will require a lot of iceteroids, which will ALSO bring other gases.

Zubrin and McKay suggested that 40 impacts of 2.6 km diameter 10% pure NH3 asteroids would double the amount of N2 in the Martian air by direct importation. So adding guesses onto assumptions here we might have...

Typical Icteroid:
- Metals, rock, soils and salts.............08%
- H2O ice..........................................55%
- CH4 ice...........................................15%
- CO2 ice...........................................10%
- NH3 ice...........................................10% (Note 2.5 times as much C as N looking at %)
- Everything else (CO, Ar, etc.)...........02%

Now we need to increase the current N2 pressure by about 28 times. I am assuming that half of this comes by H-Bombs in deep rock deposits. I am assuming that for every tonne of nitrogen brought by iceteroid an extra tonne of nitrates are volatilized by the impact. So we would need to increase Mars' nitrogen level by 7 times via direct importation. (This would be 240 impacts of the 2.6 km bodies described above.)

So our atmosphere might now look like:

Composition:
- CO2.....55.0 mBar
- N2..........3.36 mBar
- Ar...........0.1 mBar ?
- O2..........0.012 mBar
- H2O........0.01 mBar (rising with increasing temperature.) ?

- Various trace gases ~0.001 mBar

- C2F6.....0.00003 mBar
- C3F8.....0.000125 mBar
- C4F10...0.00001 mBar
- SF6........0.000045 mBar
- NO2.......0.00001 mBar

Total: ~58.5 mBar.

Note that about 2 mBar of carbon are added via direct importation. What ever the form, most of it will end up as CO2 in a few years. All those impacts are almost certainly drive some CO2 out of clays and permafrost clathrates even if carbinate beds (if any exist) are not targeted. Further, we will get temperary warming during the impact years which will speed CO2 being outgassed by the clays. So I've bumped the CO2 level by 5 rather than by 2.

If we assume 3 of these 2.6 km iceteroid impacts per year, this phase would be take 80 years to complete. If one per year, it would take 240 years.

Also note that many megatonnes of water would be added to the planet. I've not added it to the atmospheric level as it would frost out. I have added a smidge to the percentage of H2O in the air as after adding all these gases, we would have a warmer atmosphere and it would be able to hold more water.

The effort to finish the second level of atmosphere engineering is significantly greater than the first. It will be hard to increase the nitrogen level quickly. However, once this is done, we can use nitrogen fixing plants to enrich the soils of Mars. Great fields of clover would be great steadily adding to the soil's quality and to the partial pressure of O2 in the air.

However, before we can get clover and other higher plants we have to do two things. We must reduce the UV level. And we have to increase the oxygen partial pressure. (Higher plants need O2, mostly for their roots. In an O2 depleted environment they smother.)

These problems will be discussed in the third essay in this series.

By the way, many of these numbers our very rough. I'll fine them up, time allowing, as I learn more. If you have references that suggest that any of them are wrong, please let me know and I will correct this post.

EDIT: The third and last post in this series of essays is at: STAGE THREE: ADDING OXYGEN.

Warm regards, Rick.

nickname · 2007-11-26 07:49:56

Hi RickSmith,

Hate to be the bearer of bad news but NO plants with atmospheric c02 above 5%, none in the only viable place with such an atmosphere the water since water will be frozen solid.
Even cyano cant grow in ice frozen like solid steel.

Depending on cyano even on a warm Mars to convert 90% of even 100mb c02 into oxygen will take nearly forever in human terms, in fact we can only get to 35% oxygen before it self ignites.
It's a long wait for that to happen though.

I can't understand why this is overlooked.
Makes us plant people cringe when talk of a green Mars is impossible without massive inert gas imports first just to balance the c02 % before we have any hope of land plants.

Warm, Nitrogen/inert Gas import, decrease co2, maybe land plants if the temperatures and UV and other high energy radiations and c02/oxygen/inert gas weight are right and Mars induced plant mutation rates due to 1/3 gravity and increased radiation loads are just right.
Plants are very delicate things with very specific needs.

Not even sure its a viable scenario since Mars probably wont stay warm with less than 5% c02 per weight unless we have a few bars of atmosphere.

In my opinion trying to make Mars into Earth 2 is impossible.
The math for land life just doesn't work, the gas mixes don't work, or it takes so long to accomplish the ability to put life on land that its nearly forever in our terms.
Warming Mars and adding life to the water on Mars is possible, it should be our only goal.
Not such a bad thing to walk on Mars with just a gas mask, and live indoors and look at the greenery.

Rules of the game, not mine.

Wish some other plant people would dive in here, i hate being the bad news plant bear alone.

RickSmith · 2007-11-26 11:59:39

Hi RickSmith,
Hate to be the bearer of bad news but NO plants with atmospheric c02 above 5%, none in the only viable place with such an atmosphere the water since water will be frozen solid.

Hi Nickname,
Thanks for the feedback. I will discuss the temperature question
when I have more time (I'm at work right now). But after careful
rereading, I'm not able to make out what the first part of the
sentence is saying. Could you clarify?

Very warm regards, Rick.

nickname · 2007-11-26 15:26:08

RickSmith,
Your welcome.

Did you not understand (hate to be the bearer) ?
I just meant that i hate being the guy to give bad news about the plant/life plans for Mars.

Or that 5% co2 per weight of atmosphere was a max for land plant life?
Or that water on Mars will be frozen solid like steel on most of Mars until we approach 100mb of c02?
Actually i believe 50mb melts a lot of mars for the summer, 100mb to keep the ice from getting to deep year round.

Guess i should have spell checked first.
Sometimes you just get an idea and start typing away without thought for grammar.
In my case its two finger typing, so the brain is faster than the fingers.
I'm going to stick with that excuse

I seem to be the only one following the laws of life and the laws of Mars put altogether.

To many very well educated people simply can't imagine Mars as a very hostile place for plants or any life.
They simply skip the needs of plants when calculating oxygen production and how plants can alter Mars.

I think we are just so used to seeing plants here on Earth and expect them to work on Mars.

I guess people just don't like it much when they confront the idea that Mars will be no walk in the park to terra form.

Warming Mars produces a warm toxic Mars instead of a cold toxic Mars.

Things will have to be just right for plants or any other life that finds c02 a toxic substance.
Even to get tough forms of life in watery places will be a struggle to begin with.

samy · 2007-11-26 16:26:03

Nickname, you are absolutely right that we should not ignore the CO2 toxicity.

I think most people are just hoping we'll get huge amounts of oxygen and buffer gas from...somewhere, I dunno, I guess they're thinking of bombarding Mars with asteroids or something.

For humans, building up the pressure is enough, it can be all CO2 if that's what it takes -- we can wear breathing masks if so.

But plants can't wear breathing masks, so if we want to open sky farm on Mars, we'll have to have a lot more gases in the atmosphere than just CO2.

Of course, we could always closed dome farm.

RickSmith · 2007-11-26 17:51:11

Hi Samy, Nickname.
I know that higher plants need a certain level of O2. (I mentioned this at the end of my post.) But are you saying that they have a maximum level of CO2?

Which plants are so affected? I assume that this is not the case with cyanobacteria, and the bryophyte plants.

Will post later, very warm regards, Rick.

nickname · 2007-11-26 18:07:37

samy,

Thanks.

I guess I'm not alone in seeing the problems of c02 on Mars, mostly oxygen not such a good thing either.
No real good place we can get to with either of the gasses in any combination.

I think the teraform of Mars is such a insanely long term project when we logically take all the steps needed into account.
The 1 bar or more of nitrogen import i think a real killer for the idea, importing it is the only way i can see in a semi short time span to decrease c02 levels.
Not impossible to get that quantity of nitrogen to Mars, but maybe 1000-5000 years to deliver it from Titan to complete step 2 of the 50 or so step plan for land life on Mars.

Maybe just warm Mars, put up growing/living domes, wear breathing masks outdoors and add life to the ponds might be the only realistic goals for Mars.

It would still be a great destination, just not earth2.
We can make it earthlike indoors even with the technology we have now

I'm not happy to point out the problems because i love the idea of teraforming myself.
We just need a logical plan with no missed steps to make it a real plan, then learn to live with the time/energy penalties those steps require.

This is just a few i can't get around.
No growing plants on a place that wont support growing them due to toxic gas levels, no converting c02 to oxygen levels that self ignite even at 35% if you could grow plants, no unprotected land life with c02 above 5%, no way to convert c02 to obtain a 5% c02 atmosphere with less than 35% oxygen with current gases on Mars, no open water on a place at minus 100c each night in summer so no cyanobacteria either.

The warming of Mars might make it possible to have cyanobacteria in the water, but little else for the first few hundreds of years until it consumes most of the toxic iron. peroxides and other nasties that are sure to reside the ponds.

samy · 2007-11-26 18:11:16

Figuring out a way to infuse good amounts of buffer gas would pretty much solve all of those problems though. All of those problems more or less just mean, "insufficient buffer gas". That's all it comes down to in the end. We need buffer gas.

nickname · 2007-11-26 18:30:33

Hi Rick,

I think the toughest of all the plants can only withstand about 6% co2 content then it becomes a toxic substance.

Most of the plant life on earth in the 3% range, around 1% for most animals, 2-3% for short durations.
Fungal life is many times more tolerant of C02 and other toxic elements, it might be a good candidate for the surface of mars if its all kept damp.

Cyanobacteria is not as effected with c02 in the water, and water won't be a great co2 holder, so short waits to start it growing.
Even though water will repel c02 semi well, cyanobacteria would be problematic at much beyond 20% co2 content in the water.

If Mars has persistent waves on its ponds we wont be able to keep co2 water content below 20%.

nickname · 2007-11-26 18:54:18

samy,

I agree 100% on the buffer gas, it pretty much solves all the problems.

My guess is 1 bar needed with a warm Mars having a native atmosphere of 70mb all co2.
Mars will lock some c02 away for us leaving maybe 50mb co2 or about 5% of 1 bar.

Oxygen for land life will be a problem at that point, but water separation could solve that.
At least enough oxygen so plants can have the night cycle they need.

We are still stuck with oxygen masks on Mars for a very long time, but at least the plants can grow on the surface and happily convert c02 for the next billion years or more.

We have lots of places we can get the buffer gas, asteroids, Kbo's, ort objects.
Since Titan has so much of it, is well positioned to get it and has a low escape velocity i think its an excellent choice.
A bonus is that the gas is nitrogen.
We can steal some methane and other potent greenhouse gasses from Titan for Mars, lakes of fuel at Titan for transport is everywhere.
Titan even has hydrogen and oxygen in ice format should we need them to fire rockets.

We are sure to turn Titan into a different place though.

Midoshi · 2007-11-26 20:52:55

I feel I have to come in here and mention that many animals (including humans) can be acclimated to relatively high CO2 levels.

The reason that high atmospheric CO2 levels are usually harmful to animals is that they lead to hypercapnia (excess CO2 in the blood), which causes carbonic acid to form in the bloodstream and results in acidosis (dangerously low blood pH).

Many studies have shown that if animals are exposed for several days to several percent CO2 their kidneys begin retaining bicarbonates in the blood, which increases its alkalinity and renormalizes blood pH.

Human beings have been acclimated to 4% CO2 (40 mbar) with no psychological or motor skill impairment, rhesus monkeys have been fully acclimated to 6% CO2 (60 mbar), and sheep have been reported to remain alert and maintain a normal diet when breathing up to 12% CO2 (120 mbar), even at lowered oxygen levels.

In fact, increased CO2 levels help human beings (and presumably other animals) better tolerate low oxygen conditions. In one study, people exposed to 10% O2 and 4% CO2 (40 mbar) with N2 backfill to 1 atm maintained normal arithmetic competancy whereas people exposed to 12% O2 with just N2 backfill experienced lower scores (Lambertsen et al. 2001).

I'd also like to gently remind everyone that it is really the partial pressure and not the percentage that is important in determining CO2 toxicity. It is for this reason I have listed the approximate CO2 partial pressure as well as the atmospheric percentage for all the numbers I have given.

RickSmith · 2007-11-26 22:03:15

Hi Rick,
I think the toughest of all the plants can only withstand about 6% co2 content then it becomes a toxic substance. ...
Cyanobacteria is not as effected with c02 in the water, and water won't be a great co2 holder, so short waits to start it growing.
Even though water will repel c02 semi well, ...

Hi nickname,
This is not at all my understanding. People grow plants in high concentration CO2 greenhouses. Above a certain point, plants don't grow any faster with more CO2, but I've not seen anything that says it becomes toxic to them (providing they have a high enough partial pressure of O2).

CO2 is absorbed well in sea water. I've seen estimates that say that 50 times the CO2 is in the Oceans compared to the atmosphere. (That is why some people are so worried about the warming ocean waters.)

Anyway, could you give the reference where it shows that CO2 is toxic to plants at high concentrations?

Warm regards, Rick.

samy · 2007-11-26 22:15:23

There's also the concern that if you started having plants on a planetary scale, not just in one or two craters, having enough of them, they'd start eating up all the CO2 and soon you'd have an O2 atmosphere which would self-ignite and everybody would die in a firestorm.

You could try to regulate the pace of CO2 -> O2 conversion, but we're not even managing to do that here on Earth...

So again, buffer gas, buffer gas, buffer gas. It is the cureall.

Midoshi · 2007-11-26 22:26:34

There's also the concern that if you started having plants on a planetary scale, not just in one or two craters, having enough of them, they'd start eating up all the CO2 and soon you'd have an O2 atmosphere which would self-ignite and everybody would die in a firestorm.

Ummmm, not exactly.

Yes, natural fires would increase as O2 levels rose on Mars. However, once you get to the point where you're having forest/tundra fires that convert O2 to CO2 at the same rate that the plants are converting CO2 to O2, you've reached a stable equilibrium. What O2/CO2 ratio that'd exactly be is a very complex question.

samy · 2007-11-27 01:10:37

Well, if the only flammable things on Mars are our farms and colonists, then that's what'll burn.

Of course, we could plant forests and tundra (?) so the rising O2 concentrations would have something else to burn than our farms and colonists...kind of like providing false targets...

nickname · 2007-11-27 05:54:07

Hi Rick,

Here is a quick one about animal life co2 toxicity.
Will hunt out a good plant one today that isn't to long.

Animal toxicity
Carbon dioxide content in fresh air varies between 0.03% (300 ppm) and 0.06% (600 ppm), depending on the location (see graphical map of CO2 in real-time).

A person's exhaled breath is approximately 4.5% carbon dioxide.

It is dangerous when inhaled in high concentrations (greater than 5% by volume, or 50,000 ppm). The current threshold limit value (TLV) or maximum level that is considered safe for healthy adults for an eight-hour work day is 0.5% (5,000 ppm). The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues is significantly less.

These figures are valid for pure carbon dioxide. In indoor spaces occupied by people the carbon dioxide concentration will reach higher levels than in pure outdoor air. Concentrations higher than 1,000 ppm will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration. The discomfort will be caused by various gases coming from human respiration and perspiration, and not by CO2 itself. At 2,000 ppm the majority of occupants will feel a significant degree of discomfort, and many will develop nausea and headaches. The CO2 concentration between 300 and 2,500 ppm is used as an indicator of indoor air quality.

Acute carbon dioxide toxicity is sometimes known as by the names given to it by miners: blackdamp (also called choke damp or stythe). Miners would try to alert themselves to dangerous levels of carbon dioxide in a mine shaft by bringing a caged canary with them as they worked. The canary would inevitably die before CO2 reached levels toxic to people. Carbon dioxide caused a great loss of life at Lake Nyos in Cameroon in 1986, when an upwelling of CO2-laden lake water quickly blanketed a large surrounding populated area. The heavier carbon dioxide forced out the life-sustaining oxygen near the surface, killing nearly two thousand people.

Carbon dioxide ppm levels (CDPL) are a surrogate for measuring indoor pollutants that may cause occupants to grow drowsy, get headaches, or function at lower activity levels. To eliminate most Indoor Air Quality complaints, total indoor CDPL must be reduced to below 600. NIOSH considers that indoor air concentrations that exceed 1,000 are a marker suggesting inadequate ventilation. ASHRAE recommends they not exceed 1,000 inside a space. OSHA limits concentrations in the workplace to 5,000 for prolonged periods. The U.S. National Institute for Occupational Safety and Health limits brief exposures (up to ten minutes) to 30,000 and considers CDPL exceeding 40,000 as "immediately dangerous to life and health." People who breathe 50,000 for more than half an hour show signs of acute hypercapnia, while breathing 70,000 – 100,000 can produce unconsciousness in only a few minutes. Accordingly, carbon dioxide, either as a gas or as dry ice, should be handled only in well-ventilated areas.

nickname · 2007-11-27 06:20:55

Hi Rick,

A short greenhouse c02 supplement guide.

http://www.gov.mb.ca/agriculture/crops/ … 01s02.html

nickname · 2007-11-27 06:56:50

Midoshi,

I think oxygen levels would easily obtain the self ignite point on Mars with its current gases or a warmed Mars with similar gas in thicker amounts.
On a planet with no land bio mass to burn, and all the oxygen production from water sources it's inevitable.

Since no land life will grow with toxic c02 levels, fires wont exist until the 0xygen is at ignite point.
Co2 would still be 9X beyond toxic levels for any land life when this happens.

It's a really long wait though to convert over 35% of the co2 into oxygen with just cyano and few other very tough water plants.
We have lots of time to bring in the buffer gas to stop this

Rick,

I think on Mars the c02 levels in ponds will stay below 20%, dissolved iron and other water contaminants will help keep it in check and the water weight itself.
Since Mars atmosphere would be almost 100% c02, water will be much higher percentages of c02 than on earth, but the water itself will only take up so much co2 before reaching a balance point.
We just don't need persistent waves on mars adding and mixing fresh c02 into the water like happens on earths oceans.

nickname · 2007-11-27 07:09:15

Midoshi,

Really interesting info on acclimatization of animals to C02.
I wouldn't have even guessed that was possible.

Would love to read a bit about that.
Got a link i can visit?

Terraformer · 2007-11-27 08:48:18

A pity the colonists can't have children then (they wouldn't be aclimatized.)

samy · 2007-11-27 09:32:05

Is there any reason they wouldn't become acclimatized in the womb? They do share the mother's blood circulation at that point, after all.

RickSmith · 2007-11-27 11:30:10

Hi Rick,
A short greenhouse c02 supplement guide.
http://www.gov.mb.ca/agriculture/crops/ … 01s02.html

Hi Nickname, everyone.
The link above is to a Canadian government study that talks about increasing productivity by adding CO2. The relevant portions I've copied below:

How Does C02 affect Plant Growth?
The ambient level of C02 in the atmosphere is 340 PPM. At 100 PPM of C02 the rate of photosynthesis would be stopped completely. At 150 PPM the plants begin to respire, and photosynthesis is stopped. At this low level the plant will no longer be able to obtain C02 from the atmosphere and photosynthesis is restricted. The plant will eventually use all of the C02 present, photosynthesis will stop and the plant will die.
The rate of photosynthesis at 350 PPM will be consistent with growing conditions outside of a controlled environment, given that ambient levels of C02 in the atmosphere are 340 PPM.
With no other limiting factors such as heat, light and nutrients the plants will photosynthesize at a rate consistent with ambient conditions (i.e. outside of the greenhouse). There may be a slight increase in photosynthetic efficiency due to the higher than ambient C02 level, however this increase will probably be insignificant. The level of 1000 PPM C02 is very close to the optimum level of C02 required, given no other limiting factor, 1200 PPM, to allow a plant to photosynthesis at the maximum rate.
At this level most plants will respond favorably by increasing photosynthesis, however this is dependent on all the other limiting factors being optimum for the plant. Therefore at 1000 PPM the photosynthetic rate should be almost at maximum for most plants. However unlikely, at 10,000 PPM of C02 the photosynthetic rate in the plants will be very low due to the closing of the plant stomata and the exclusion of air into the leaf interior.
This level of C02 is sufficient to cause toxic effect on the plants and cause damage and eventually death of the plant. Also at this level of C02 it would be very hazardous to workers in the greenhouse, as they too would experience C02 poisoning. The photosynthetic rate would likely be zero at 10,000 PPM of C02 for the above stated reasons.

This study is not talking about if they are using C3 or C4 plants. (Likely C3 as I expect that most C4 plants are not usually found in greenhouses.) But the effect that they refer to is the closing of the plant's stomata. So cyanobacteria would not be affected by this. I am also not convinced that 'primitive' plants such as Bryophites or mosses will be affected. (In fact I have evidence that they would not be.)

(I will round up references and edit them into this post later.)

Anyway, many thanks Nickname. This is the first I've heard that some plants have a maximum CO2 level.

Warm regards, Rick.

Midoshi · 2007-11-27 15:58:47

Midoshi,
I think oxygen levels would easily obtain the self ignite point on Mars with its current gases or a warmed Mars with similar gas in thicker amounts.
On a planet with no land bio mass to burn, and all the oxygen production from water sources it's inevitable.
Since no land life will grow with toxic c02 levels, fires wont exist until the 0xygen is at ignite point.
Co2 would still be 9X beyond toxic levels for any land life when this happens.

If you're getting your O2 from photosynthetic autotroph processing of CO2 then there will be a stable equilibrium somewhere. As you suggested, this is still potentially viable, if somewhat slow.

If you are NOT getting your O2 from photosynthesis (hydrolysis or nitrate decomposition for example) then yes; you can get above the self ignition point and then have any organics you try to introduce be consumed in flames. Pretty silly thing to do if you ask me, but I guess if you had an incompetant terraforming foreman... (;

You could of course use industrial nonbiological techniques to bring up the O2 level to a certain level under the organic self ignition point and then let your autotrophic friends loose to get the rest of the way to a stable equilibrium. How far you "jumpstart" the atmosphere with industrial techniques will determine how violent wildfires will be, but there's nothing to suggest you couldn't stuff at least a few mbar of O2 in there early on and still have a non-apocalyptic wildfire situation.

I get your point though, that CO2 toxicity is an issue that cannot be overlooked.

Per your other post, here's a link to a 1986 review of the effects of acute, intermittant, and chronic effects of CO2 on animals:
http://legacy.library.ucsf.edu/tid/sgo40e00/pdf

The appendices at the back are probably the most interesting.

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