Minimal Martian Terraformed Atmospheres

Midoshi · 2008-02-22 13:56:04

So to be clear, you are suggesting that a mixture of gases like:
CO2: ....... 120 mbar.
O2: ......... 200 mbar.
N2 .............. 5 mbar. (Plants can now fix nitrogen.)
Ar ............... 1 mbar.
could be breathed in both greenhouses and the main residential areas?

Sure, Rick, that'd work just fine. In fact, at those levels of ambient O2 and CO2 your blood O2 pressure would be almost exactly the same as at sealevel on Earth, ~100 mm Hg. Let's walk through the math, converting from "mbar" to "mm Hg" to make comparison with medical data easier:

Ptot = 200 + 120 + 5 + 1 = 326 mbar = 245 mm Hg
FO2 = 200 / 326 = 0.61
FCO2 = 120 / 326 = 0.37

Now that we have the total atmosphere and fractional components, we can find the inspired pressures by accounting for water vapor in the lungs (this is in mm Hg now):

PIO2 = 0.61*(245 - 47) = 121 mm Hg
PICO2 = 0.37*(245 - 47) = 73 mm Hg

Ok, here's where a little research was required. Turns out there's a linear relationship between PIO2, the inspired O2 pressure, and PaO2, the arterial O2 pressure. Using data from (Holstrom 1971), which can be found half-way down the page here, converting to inspired values as we did above, and fitting to the points PIO2 > 64 mm Hg, i.e. altitude < 20,000 ft (because the body begins to reach its limit there and the linear relationship fails), we obtain:

(Eq 1)
PaO2 = 0.84 * ( PIO2 ) - 23 mm Hg

This great little equation works down to PIO2 = 64 mm Hg with <10% error. Caution! It only works for normal CO2 levels.

By culling data from many of the references in my last post, I obtained a very similar equation for adult rats. The PaO2 values it produces agree well with the human equation. In fact, the difference is <10% for values of PIO2 < 100 mm Hg, roughly equivalent to breathing conditions found at altitudes above 10,000 ft on Earth. Since we're interested in minimal terraformation (i.e. low O2 levels), that suggests that rat respiration is a very good human analog for our purposes.

So, what about high CO2 levels? Well, CO2 stimulates respiration in animals, which means you transport more O2 from the air to your blood. Since rats seem to be a good model, I again culled data for adult rats from that list of references and found the relationship between PICO2 and PaO2 for low O2 levels to be:

(Eq 2)
PaO2 = 0.35 * ( PICO2 ) + C

where 'C' is the PaO2 one would obtain for normal CO2 levels, i.e. (Eq 1). So, substituting that in we obtain:

(Eq 3)
PaO2 = 0.84 * ( PIO2 ) + 0.35 * ( PICO2 ) - 23 mm Hg

This is the culmination of a lot of research! It allows you take inspired O2 and CO2 levels in units of "mm Hg" and determine what one's blood O2 pressure would be.

OK, now that we have the tools, back to Rick's example. Plugging PIO2 = 121 mm Hg and PICO2 = 73 mm Hg into (Eq 3) we obtain PaO2 = 104 mm Hg, which is practically the same as the 103 mm Hg recorded for sea-level on Earth by (Holstrom 1971). I think that's some serious serendipity on Rick's part!

I'll be making another post on the limits of a breathable atmosphere later today.

References:

Holstrom, F. M. G. Hypoxia. In: Aerospace Medicine edited by H. W. Randel. Baltimore: Williams & Wilkins Co. (2nd Ed.) 1971, pp. 56-85.

nickname · 2008-02-22 15:19:02

CO2: ....... 120 mbar.
O2: ......... 200 mbar.
N2 .............. 5 mbar. (Plants can now fix nitrogen.)
Ar ............... 1 mbar.

Wouldn't 60+% O2 simply self combust in 326 mb pressure?
It's very close maybe beyond combustion.
Not even sure any plant on Earth can grow in such an oxygen rich environment.
Would plants even grow at with 30+% CO2 at 326 mb pressure?
Beyond safe limits for both C02 and 02 i believe.

At one bar on Earth 30% O2 is about a max before it would self combust.
4% - 5% CO2 a max for plant growth at 1 bar for temporary periods.
2% for sustained plant growth.

6% - 10% i think is a constant max for CO2 on Mars at 1/3 bar for plants to sustain growth.
30%-50% 02 i think a max for plant respiration. (unknown)

We could probably live in the set numbers for a 326 mb atmosphere but i doubt plants will, and no smoking on the planet for fear of a global fire.

I think if you add around 150 mb N2 and decrease C02 50 % you get pretty close to safe levels for 02 and C02 for us and plants.

So maybe something like this.

CO2: ..........60 mbar.
O2: .......... 200 mbar.
N2 ........... 155 mbar.
Ar ............... 1 mbar.

Would 60mb C02 keep Mars warm though in a 416mb atmosphere or any atmospheric pressure we select.

I think we need to select how much C02 Mars needs to stay warm first, then select 02 as a filler with no more than 50% of the total final volume being 02 and 40% probably a safer number for plants, then the remaining amount will have to be an inert gas probably N2 and trace other gasses.

Midoshi · 2008-02-22 18:45:29

In order to colonize a terraformed planet it is not enough for adult organisms to function, they must also be able to produce healthy offspring. This fact, combined with the knowledge that newborn animals generally have lower tolerance thresholds than their mature counterparts, has been bugging me on the issue of atmospheric breathability for a while now.

Luckily, the use of therapeutically elevated CO2 on infants for lung protection is currently of interest and quite a few studies have focused on collecting data from neonatal rats and mice, and even human infants. Here are summaries of some of those studies:

*************************************************************

Investigating the prenatal and neonatal effects of CO2, (Dean et al. 2001) exposed pregnant mother rats for 1 week pre and post delivery. They found that 7% CO2 slightly slowed the early growth of newborns, but that they caught up with control about 2 weeks after birth. Those exposed to 10% CO2, however, experienced more severe growth retardation and did not seem to recover; much of the litter was sacrificed at birth.

Studying neonatal rats, (Rezzonico & Mortola 1989) found no significant difference in weight between control and subjects exposed to 7% CO2 during the first week of life.

(Kantores et al. 2006) examined the combined effects of hypoxia and hypercapnia on neonatal rats, finding that elevated CO2 levels helped relieve many of the effects of breathing low O2. The most extreme gas mixture used, 10.5% O2, 10% CO2, caused excessive mortality. However, mixtures of 13% O2 and between 5.5-10% CO2 allowed newborns to maintain normal (i.e. 21% O2) blood O2 pressure and red blood cell levels.

In an extremely interesting study by (Li et al. 2006) the gene expression in neonatal mice exposed to 8% CO2 and 12% CO2 for 2 weeks was compared with control to see if there were any differences. The 8% CO2 mice experienced upregulation of 365 genes and the downregulation of 342 out of a total genome of 24,878. These alterations acted to improve lung function and offered increased protection to extreme oxygen levels. In contrast 12% CO2 cause a significant expression change in only 2 genes. The authors point out that at high enough levels CO2 acts as a depressant on biological function, and invoke this as an explaination.

Another fascinating experiment was done by (Gu et al. 2007) on mice beginning at 2 days old which sought to examine the effects of elevated CO2 on neuron activity in the hippocampus. They found that after 2 weeks of exposure, the mice on 8% CO2 has nearly identical neuron operation with control, while neuron excitability in mice on 12% CO2 was significantly inhibited.

In study of premature human infants by (Mariani et al. 1999) it was demonstrated that newborns on assisted respiration required significantly less time on the respirator when given a hypercapnic air mixture than when not (2.5 days vs 9.5 days, on average). Blood CO2 pressure was raised by ~10 mm Hg, so I'd guess they used ~5% CO2.

*************************************************************

These results are fairly consistent with the previous estimates of CO2 toxicity presented in this thread, and indicate that for optimal newborn growth a biological threshold of 50-64 mm Hg inspired CO2 (7-9% CO2 at 1 atm) should be followed rather than the adult tolerance threshold of 86 mm Hg inspired CO2 (12% CO2 @ 1 atm).

In terms of O2 requirements, (Xu & LaManna 2006) identify PaO2 ~ 50 mm Hg as the limit of chronic mild hypoxia, i.e. the point below which degradation of biological functions begins over long periods. They also suggest PaO2 ~ 35 mm Hg as the limit of consciousness for long term exposure. These values are consistent with previous estimates in this thread as well as this one.

So using the theory of "normal adult function threshold" as the safe limit for infants, should we take PaO2 = 50 mm Hg as an acceptable limit? Well, the city of Potosi says "Yes!" Having over 130,000 people, and existing since 1546 A.D. at an elevation 4000 m, adults and infants alike in Potosi inspire O2 at PIO2 ~ 90 mm Hg, which corresponds to a PaO2 ~ 50 mm Hg. While (de Meer et al. 1995) do find a moderate reduction of children's stature at such an altitude, in part attributible to the mild hypoxia, severe growth retardation is not observed. If you want to read more about the adaptation of animals, including humans, to high altitudes (Monge and Leon-Velarde 1991) is a wealth of information.

My gut says that the respiration stimulation by CO2 should not be relied on when thinking of how much O2 is in the blood. I think the effect of CO2 should be used as relief for already bearable hypoxia, not a tool that allows us to drive the atmospheric O2 below normally untolerable levels. The fact that all the rat newborns on 10.5% O2, 10% CO2 in (Kantores et al. 2006) died supports this. Though one might have expected sufficent PaO2 from (Eq 3) in my previous post, the actual PaO2 was much lower, suggesting some limit had been reached and the linear relationships involved failed. I suspect the hypoxia was too much and the effect of CO2 couldn't cope.

My suggestion is that an inspired O2 of PIO2 = 90 mm Hg (13% O2 @ 1 atm) be used as the minimum limit for oxygen.

A simple atmosphere of just O2 & CO2 at PIO2 = 90 mm Hg and PICO2 = 57 mm Hg (equivalent to breathing 13% O2, 8% CO2 @ 1 atm), would look like this:

O2:.......160 mbar
CO2:.....100 mbar

You can add any inert gas (N2, H2O, Ar, etc.) within reason and this will still be breathable. In fact, its breathability will be slightly enhanced by adding other gases due to the increase in total pressure.

From (Eq 3) in my previous post, one would expect to have a blood O2 pressure circa 68 mm Hg, which is comparable to the oxygenation experienced at ~9000 ft on earth. Substantial inhabited portions of Colorado are above this elevation.

References:

Developmental changes of the response of in vivo ventilation to acute and chronic hypercapnia in rats
JB Dean, PB Douglas, JA Filosa, AJ Garcia, RW Putnam and CE Stunden, Respiratory Research 2001, 2(Suppl 1):P13
http://respiratory-research.com/content/2/S1/P13

Respiratory adaptation to chronic hypercapnia in newborn rats
R Rezzonico & JP Mortola, J. Appl. Physiol. 67(1): 311-315, 1989

Therapeutic hypercapnia prevents chronic hypoxia-induced pulmonary hypertension in the newborn rat
C Kantores, PJ McNamara, L Teixeira, D Engelberts, P Murthy, BP Kavanagh, and RP Jankov, Am J Physiol Lung Cell Mol Physiol 291: L912–L922, 2006.

Effect of carbon dioxide on neonatal mouse lung: a genomic approach
G Li, D Zhou, AG Vicencio, J Ryu, J Xue, A Kanaan, O Gavrialov, and GG Haddad, J Appl Physiol 101: 1556–1564, 2006.

Chronic High-Inspired CO2 Decreases Excitability of Mouse Hippocampal Neurons
XQ Gu, A Kanaan, H Yao, GG Haddad, J Neurophysiol 97: 1833–1838, 2007.

Randomized trial of permissive hypercapnia in preterm infants.
G Mariani, J Cifuentes, and W A Carlo, Pediatrics. 1999 Nov; 104 (5 Pt 1):1082-8

Chronic hypoxia and the cerebral circulation
K Xu & J C LaManna, J Appl Physiol 100: 725-730, 2006

Physical adaptation of children to life at high altitude
K. de Meer, HSA Heymans, and WG Zijlstra, Euro J of Ped, V 154; 4, 1995

Physiological Adaptation to High Altitude: Oxygen Transport in Mammals and Birds
C Monge & F Leon-Velarde, Physiological Reviews, V 71; 4, October 1991

RickSmith · 2008-02-22 23:37:59

CO2: ....... 120 mbar.
O2: ......... 200 mbar.
N2 .............. 5 mbar. (Plants can now fix nitrogen.)
Ar ............... 1 mbar.
Wouldn't 60+% O2 simply self combust in 326 mb pressure?

Hi Nickname.
It should not. The inferno in Apollo 1 was caused by pure O2 at
slightly above ambient pressure (16 pounds per square inch). The
gas mixture I picked had the same partial pressure of O2 as Earth's
sea level.

By the way, I assume you do not literally mean self combust. The
O2 won't burn with O2, it needs some sort of fuel.

Now fires in pure O2 burn a bit hotter. One use of a buffer gas is
to lower the flame temperature because this gas that is not adding
to the flame energy will absorb heat to warm it up.

CO2 takes a bit more heat to warm it than N2 (more vibration modes
in the molecule) but there is less CO2 (in the above suggested atm)
than Earth's sea level N2. So likely the atmosphere suggested above
would have slightly higher flame temperatures. However, I can't
see the flammability of things being orders of magnitude more
combustible. The key point in the Apollo 1 fire was that there was
5-6 times more O2 than normal. The above atmosphere, has 1
times the normal (sea level) O2. Look at the partial pressures of the
gas components and not their percentages.

Now the air mixture does not have to have that much O2. We can
breathe lower partial pressures of O2 and if we pick a mix that say
has 50 mbar less, then fires should be slightly less likely to spread
than sea level fires on Earth.

(I am a bit out of my area here. Can someone comment on my
educated guesses?)

Rick

Midoshi · 2008-02-23 02:34:02

nickname, thanks for your input

Plants honestly don't care what percentage of their atmosphere is O2. Like us, all they care about is the partial pressure inside their stomata (our alveoli). So a plant in Rick's example will actually "see" slightly less than the amount of oxygen it would at sea-level on Earth. Hardly overwhelming.

Now for a stab at the old question of flammability. Rick is correct that CO2 is a more effective buffer gas per molecule because of its increased internal energy capacity, i.e. specific heat. Its ability to absorb and emit infrared also allows it to radiate heat away from the core of a fire in a way that nitrogen cannot.

Unfortunately, though not through lack of investigation, there is no simple equation to determine the flammability of an atmosphere. The best I can offer are the following two resources.

************************************************************

Java Applet for Downward Flame Spread Over Solid Fuels

This link leads to an applet that allows you to enter various parameters such as oxygen fraction, atmospheric pressure, and gravity to find flame spread rate on either PMMA (acrylic glass) or cellulose. The applet assumes an N2 diluent, so any results for Mars will be pessimistic with regard to a CO2 diluent. Nevertheless, the results are encouraging:

Take cellulose under current Earth conditions. A flame spread velocity (V_f0) of 0.83 mm/s is calculated. Now try 35% O2 at 1.2 bar, which approximates the Carboniferous Period on Earth. You should get something like 2.6 mm/s for the flame velocity. Now try Rick's 61% O2 at 0.326 bar and 3.7 m/s^2 gravity. I got 2.2 mm/s, which is comfortably lower than the flame velocity for the Carboniferous.

Now wouldn't it be nice if we had some numbers on N2 vs CO2?

************************************************************

Effect of Ambient Atmosphere on Flame Spread at Microgravity

This link goes to a study experimentally comparing the diluent effects of N2, Ar, He, CO2, and SF6 in both 1g and microgravity.

The paper contains a good survey of the all effects that need to be taken into account when considering a diluent's effects on flammability. But if you're interested in results just skip down to the Figure 5 images of "Flame Spread Rate versus O2 Mole Fraction" for N2 and CO2. You can see that 50% O2 in CO2 has a similar flame spread velocity to 35% O2 in N2 at 1 atm and 1g. This suggests that in order to obtain a more accurate flame spread velocity calculation in the applet we should use 43% instead of 61% O2 to model Rick's example since that would be the flammably equivalent percentage for N2. This produces a flame spread rate of 1.2 mm/s, about the same as a 25% O2 atmosphere on Earth and much lower than the 2.2 mm/s calculated by assuming CO2 was equivalent to N2. In reality the flame velocity would probably be somewhere between these two numbers due to the fact that the diluent abilities of N2 and CO2 converge as gravity is reduced and Mars' gravity is less than Earth's. It would be much closer to 1.2 mm/s though.

Another useful graph from the paper is Figure 8, the last image. It shows the relative flame spread velocities for the various gases at fixed O2 fractions and illustrates pretty clearly how CO2 is a much better diluent than N2 at 1g and about the same in microgravity. It also shows how pressure effects flammability.

nickname · 2008-02-23 06:48:09

Hi RickSmith,

Tough to wrap the mind around the lower pressure on Mars and % of things.(Earth Bias) lol

I would have guessed at 60% 02 we were much closer to the combustion point of oxygen, nice to see that it's still well within safe levels.
As soon as we started teraforming Mars we would be adding methane, hydrogen and other fuels to the atmosphere so it's nice to see we have some margins at that level of oxygen.

C02 i still think is the main problem to teraforming Mars.
We have such a limited % that will work for keeping the planet warm and keeping life in safe levels and plants at safe levels.

I think we are stuck somewhere around 10% total weight of C02 in a 326 mb atmosphere.

As the bar pressure goes up so should the C02 % go down to stay safe.
We also need that % of C02 to keep Mars warm, so it's a game of what % C02 works on Mars for everything.

In a 150mb atmosphere we might get away with 20% C02, a 500 mb atmosphere more like 5%.

N2 we really don't need a lot of to keep plants happy so 5 mb will work well.
With some luck just out gassing at Mars will produce that.
Bet not though.

nickname · 2008-02-23 07:09:52

Hi Midoshi,

On Earth plants beyond 30% O2 content have a very difficult time collecting C02.
Since levels of C02 would be much higher on Mars and pressures much lower i can't see it as a big problem.
A real unknown though how plants function at much higher levels of O2 and C02 in lower pressure with just trace amounts of N2.

It's nice to see that high levels of both almost work together, but i still see 30% C02 as a problem even in a 326 mb atmosphere.
We also need to think about the bacteria that fix nitrogen in this atmosphere scenario.
How do they function in that atmosphere, can they tolerate 60% 02 with 30% C02 with 1% N2.?

Bacteria are tough life forms so they probably would survive, but would they fix enough N2 for the plants.

I have a gut feeling around 10% C02 as a comfortable level for Mars at 1/3 bar.
I also have a feeling 1% N2 although more than enough for plants, won't be enough for the bacteria to fix it well.

Thanks for the interesting data on your posts.
Interesting reading.

dunwich · 2008-02-23 11:36:22

It's nice to see that high levels of both almost work together, but i still see 30% C02 as a problem even in a 326 mb atmosphere.
We also need to think about the bacteria that fix nitrogen in this atmosphere scenario.
How do they function in that atmosphere, can they tolerate 60% 02 with 30% C02 with 1% N2.?

What abouth anammox bacteria they live in oxygen poor waters.
This gives a whole range of advantages, they can begin releasing Nitrogen at a earlier stage (I recon) and the surface ice protects them from radiation.
http://www.sciencedaily.com/releases/20 … 104202.htm

Midoshi · 2008-02-23 16:07:22

You know, I've been wondering about this nitrogen thing for a while now. I'm not so sure atmospheric nitrogen is a prerequisite for a stable ecosystem. It would seem that once there is "fixed" nitrogen in a biological system (e.g. ammonia, nitrates, nitrites) there can exist a nitrogen cycle entirely decoupled from the atmosphere. See the EPA image below:

Through plant and animal decomposition and assimilation, the nitrogen can make a complete cycle and sustain a happy ecosystem. The only rub is that "denitrifying" bacteria, who live in anoxic conditions such as the soil and stagnant water, like to use nitrate instead of oxygen as their metabolic electron acceptor. This turns the fixed nitrogen into atmospheric N2, which is useless to all life except nitrogen fixing bacteria, who help return it to a biologically accessible form. There are also abiotic ways nitrogen is fixed, such as UV radiation, lightning, and volcanic activity.

In some sense the question comes down to this: Are we setting up our terraformed ecosystem using gaseous N2 or a fixed form like nitrates? Either will work. If we use gaseous N2 we need to make sure we have >5 mbar, and it will take a while for fixing bacteria to build up enough fixed nitrogen from this for an ecosystem to operate. On the other hand, if we initially introduce nitrates higher plants will be able to immediately use it as a nutritive resource. Again, we have the requirement that we have >5 mbar worth of nitrates so that when denitrifying bacteria start bleeding nitrogen off to the atmosphere there will be enough pressure for nitrogen fixing bacteria to reabsorb it.

There is a second reason nitrates are attractive: they probably already exist on Mars. Many people claim that this is speculation since we haven't observed any nitrates on Mars, but this is uncompelling. The truth is that: 1) nitrates are extremely hard to detect using spectrographic techniques, and 2) there is every reason to believe that nitrates would only exist in substantial quantities at depths of ~1 meter. An excellent paper by (Sutter et al. 2007) demonstrates this by using soil from the Atacama Desert, an oft used terrestrial Martian analog. The Atacama is hyperarid (50 times less water than Califronia's Death Valley), with heavy saline deposits, nearby volcanos, and has thin air and high UV due to its elevation. It also boasts the world's most incredible nitrate deposits: in many regions >7% of the soil is nitrate by weight (Prellwitz et al. 2006). However, as (Sutter et al. 2007) show, even in the areas with the most concentrated nitrate deposits we cannot discern them via spectrometry until they occupy ~1% of the soil by weight, and that doesn't happen until a depth of ~1 meter has been reached. Below this depth the nitrate fraction can quickly explode up to 30% of the soil's weight.

So the Atacama has huge nitrate deposits; why think that Mars does too? It is thought that Atacama's deposits are due largely to the volcanism of the surrounding area, which is estimated to have fixed 2800 megatons of nitrogen from the air (Oyarzun & Oyarzun 2007). Extrapolating this to the global volcanism of Mars using (Geeley & Schneid 1991), we would expect 180 million megatons, or 45 mbar worth of nitrogen to be fixed as nitrates and nitrites. In addition it has been experimentally demonstrated by (Segura et al. 2005) that UV radiation could have fixed almost 2 megatons of nitrogen every year on early Mars. Between the time of Mars formation 4.6 Gyr ago and the beginning of the Late Heavy Bombardment 4.0 Gyr ago, this mechanism could have fixed 250 mbar of nitrogen in the soil before impactors blew off much of Mars' atmosphere. This would also be before the Martian global magnetic field decayed and solar wind erosion began.

But did Mars even have this much nitrogen to start with? By analogy with Earth a planet of Mars' mass could have accumulated 120 mbar of N2 during formation, and by analogy with Venus it might have begun with 560 mbar. Even if Mars began with an extremely pessimistic 1 bar CO2, the ratio of C/N = 20 in comets and terrestrial planet atmospheres means it should have begun with at least 25 mbar N2. And since (Phillips et al. 2001) estimate a magmatic outgasing of 1.5 bar of CO2 during the formation of Tharsis, anywhere from 38 to 250 mbar N2 could have been added to the atmosphere later, based on possible magma N2 contents from (Segura et al. 2005).

Ok, Mars had the ability to fix large amounts of nitrogen in the past, as well as a significant inventory from which to fix it. So where is it? Well, nitrates are extremely soluble, meaning that during Mars' wet period(s) most of it would have quickly dissolved and been transported to the northern plains. As the water froze/evaporated the nitrates would have been deposited primarily in the Utopian basin, which seems to have originally been an impact crater the size of Hellas that's been filled in with sediment due to its watershed containing over 2/3 of the Martian surface (Bandert 2004). Other locations of heavy nitrate deposits might be the Acidalia, Amazonis, Argyre, Chryse, Echus, Hellas, and Isidis plains.

Interestingly, the crustal thickness at these locations is very thin, on the order of that found at Iceland or thinner, suggesting that the geothermal gradient there may be sufficient to support liquid water at relatively shallow depths. According to (Halevy et al. 2007) such sites could experience large carbonate deposit formation after the recession of Mars' acidic seas. I find it intriguing that large deposits of both nitrates and carbonates might be located in the same places, along with the geothermal means to decompose them directly into CO2, N2, and O2. Just drill down to ~650°C, pipe down your carbonates and nitrates with some sand, and you get all those nice atmospheric gases boiling out plus a "slag" of useful building materials like sodium silicate (water glass) and calcium silicate (the prime component of Portland cement). If you don't throw in the sand you can get sodium hydroxide (lye) and calcium oxide (lime), both of which are also very useful. This is all currently within our technological reach, and perhaps could be used to provide raw materials for early research facilities and colonies.

However, even if you could magically use all the geothermal heat flux of Mars (~4 terawatts) to decompose nitrates for 1000 years, you still wouldn't have 5 mbar N2. One could conceivably use nuclear or solar furnaces to decompose nitrates, but I'm not sure it's worth it when you can just spread the nitrates around like fertilizer, which is all it really is. Just let the ecosystem absorb it and redistribute it naturally.

References

Terrestrial analogs for interpretation of infrared spectra from the Martian surface and subsurface: Sulfate, nitrate, carbonate, and phyllosilicate-bearing Atacama Desert soils
B Sutter, JB Dalton, SA Ewing, R Amundson, and CP McKay, Journal of Geophysical Research, Vol. 112, G04S10

Nitrate Concentrations in Atacama Desert soils and Their Implications for the Antiquity of the Atacama Desert.
J Prellwitz, J Rech, G Michalski, B Buck, MS Howell, and A Brock, 18th World Conference of Soil Science, July 15, 2006
http://a-c-s.confex.com/crops/wc2006/te … P18247.HTM

Massive Volcanism in the Altiplano-Puna Volcanic Plateau and Formation of the Huge Atacama Desert Nitrate Deposits: A Case for Thermal and Electric Fixation of Atmospheric Nitrogen
J Oyarzun & R Oyarzun, International Geology Review, Volume 49, Number 10 / October 2007

Magma Generation on Mars: Amounts, Rates, and Comparisons with Earth, Moon, and Venus
R Geeley & BD Schneid, Science 15 November 1991: Vol. 254. no. 5034, pp. 996-998

Ancient Geodynamics and Global-Scale Hydrology on Mars
RJ Phillips, MT Zuber, SC Solomon, MP Golombek, BM Jakosky, WB Banerdt, DE Smith, RME Williams, BM Hynek, O Aharonson, and SA Hauck II, Science, Vol 291, 30 March 2001

Implications of the Utopia gravity anomaly for the resurfacing of the northern plains of Mars
WB Banerdt, Second Conference on Early Mars (2004)

A Sulfur Dioxide Climate Feedback on Early Mars
I Halevy, MT Zuber, and DP Schrag, Science Vol 318, 1903, 21 December 2007

nickname · 2008-02-24 08:40:30

dunwich,

Anammox bacteria would be an excellent addition to the watery places.
The toxic brew, chemical rich, oxygen poor water will need lots of opportunistic and tough bacteria on Mars for the first while.

nickname · 2008-02-24 09:35:49

Midoshi,

I can't figure why more studies are not done on minimum levels and maximum levels for plants for C02 and 02 combinations and the n2 fixing cycle of bacteria in n2 poor places such as Mars.

With all the thought about some day colonizing Mars you would think these basic studies would have been done long ago.
Even greenhouse domes would need this basic info on Mars if we plan to grow plants and not be permanent nitrate miners.

We sure could spread out nitrate around the planet to get plants going.
Down side to that is we become the nitrate cycle for plants when natural process don't replace the nitrate at the rate it is used.

With a bit of bio engineering we could probably alter the bacteria to fix nitrogen more efficiently so poor quantities of nitrogen might not be a big problem.

With the same sort of engineering we could probably have plants happy in 30+% C02 60+% 02 at 1/3 bar.
Or even the best of both with plants that have an efficient nitrogen fixing gene and high tolerance to C02 gene incorporated into the cell structure.

Nature would do this itself on Mars over long periods of time, so we would just be accelerating that process.

Much like animals that have high tolerance to C02 levels will be naturally selected on Mars.
Nature would quickly adapt all forms of life on Mars through natural selection.

I would guess in as little as 10-20 generations what we put on Mars will only look semi familiar to what we placed as the originals.
The long term effects of 30% C02 60% 02 at 1/3 bar on animals and plants and bacteria is sure to alter life very fast at best, at worse create a very high mutation rate.

With 1/3 gravity, additional UV radiation, additional cosmic ray doses added into the mix we would end up with some pretty odd plants and animals when they settled into normal natural selection.

I think the basic idea of the 326mb Mars atmosphere might work, but we probably won't be placing natural Earth organisms on it.
If we do they won't stay that way for long anyway.

dunwich · 2008-02-24 14:02:45

I think the basic idea of the 326mb Mars atmosphere might work, but we probably won't be placing natural Earth organisms on it.
If we do they won't stay that way for long anyway.

Would it be wise to put a lot of organisms that convert O2 into CO2 on the surface? Wildlife is necesairy for a lot of the more advanced plant life, but the seem to be a bit counterproductive in general.

nickname · 2008-02-24 17:23:59

dunwich,

I guess if we had to much oxygen on Mars the most simple solution would be some big fires.

We are already pretty good at converting oxygen to C02 on earth so i doubt we would need anything other than a similar lifestyle on Mars. LOL

dunwich · 2008-02-27 14:16:06

We are already pretty good at converting oxygen to C02 on earth so i doubt we would need anything other than a similar lifestyle on Mars. LOL

I have no ID how but Iaccidently only posted part of a first draft

Most of it went about
Denitrifying bacteria witch are anaerobic (they don't like oxygen)
and stromatolits.

The Denitrifying bacteria extract Nitrogen out of the soil and put it in the atmosphere while Stromatolits would clean the the salt and alkalik lakes/sea on a paraterraformed Mars yust capable to keep some surface water.
Annyway the conclusion was that Denitrifying would work but leave the soil infertile. While Stromatolites would fail in producing oxygen they would clean up the young martian oceans producing large volumes of lime (think in a lime formating periode) (they would fail because the oxygen would react with the large amount of iron in the water and at the bothem)

Annyway it wouldn't be that useful until a second terraform stage, that would allow the most simple lifeforms to exist on it's surface.

Annyway getting nitrogen would be tricky because Mars has verry little and getting that little out of the ground would give you a nitrogen deprived soil witch isn't nesesairly better.
And all that iron is yust waiting to react with any hard procured free oxygen

(PS I know this post is rushed)

Midoshi · 2008-02-27 18:51:18

Cool idea with the stromatolites, dunwich. I hadn't thought about their existence on a terraformed Mars before.

The vast majority of the iron on Mars is already heavily oxidized; that's why it's rusty colored. If anything, the soil will give up excess oxygen during terraformation, not absorb it from photosynthetic sources.

As far as nitrogen is concerned, denitrifying bacteria would indeed remove nitrogen from soil, but it would be ok because nitrogen fixing bacteria would put it back, just like they do on Earth.

JoshNH4H · 2008-02-28 15:17:02

so final result:
MINIMAL Martian survivable atmosphere w/ biosphere:

5 mb N2
100 Mb CO2
160 mb O2

Total: 265 mb Atmosphere, 60% Oxygen

However, I would suggest something morre like:

100 mb N2
100 mb CO2
200 mb O2
Plus trace gases.

Total: 400 mb, 50 % Oxygen

What are some other available gases we could put in in large amounts?

dunwich · 2008-02-28 16:27:02

Sorry I'm new here. Do you have a previous post discussing the effects of blood acidosis (CO2 poising).
I've have the ID that anything above 1000 partspermillion of CO2 in the atmosphere mixture will have serious health effects if breathed over a lifetherm

nickname · 2008-02-28 19:07:30

jumpboy11j,

I've been working on this problem and come to a conclusion about a secondary problem with C02 on Mars.

I personally think we could resolve quite a bit of the toxicity problems and bar quantity problems of C02 with small amounts of Methane or super greenhouse gasses in it's place.
Our main goal for C02 is warming Mars so we can use whatever we like for that.
1% C02 will be more than enough for life so we really don't need more than that.

I seem to remember a long discussion about C02 quantity to keep Mars warm and if i remember right it was 70mb.
If we do the math on 70mb as 15% of the total atmosphere, we would need way to much total bar pressure for C02 to work as the main greenhouse gas.
If we have C02 as more than 15% of the total atmosphere it probably won't support life.

I figure something like this will work for all the gas percentage needs of animal and plant life and to keep Mars warm.

1% - 15% C02
50% - 60% 02
30% - 40% N2
1%- 5% Other. (Some can be methane or other super greenhouse gasses to decrease C02 needs and lower final bar pressure needs)

Working out the total bar pressure for each gas would require the heating totals for Mars of C02/methane/super greenhouse gas.

If we replace most of the C02 warming with super greenhouse gasses we could also lower 02, N2 and C02 needs, we make a much thinner atmosphere that stays warm.
Methane or other super greenhouse gasses will require much lower final bar pressures to do the same job as 15% of a C02 atmosphere would.
It would require much less time and much less work than having to create a nearly 500mb atmosphere to keep 02 and C02 in life levels, the import of large quantities of filler gas and to have C02 keep Mars warm.

We still need to import N2 in a lower bar pressure Mars just as a filler gas, but with much lower bar pressure needs for warmth the N2 quantity needed would be much smaller.
We would be just importing enough to balance the other gasses.

At first glance this minimal Mars atmosphere topic seems simple but it is quite complex infact.

JoshNH4H · 2008-02-29 15:24:40

how much do current estimates say are in the poles/ clathrates? (CO2) besides, every millibar of nitrogen we want is nitorgen that we have to put in the atmosphere by economic-type output. The more CO2 the better. How warm would mars be at 80 mb? 90?

nickname · 2008-02-29 17:07:26

jumpboy11j,

Going just on memory here because i can't find the original posts.
I believe 70mb of C02 just warms Mars enough to keep Mars at 0c or just at melt point as an average temperature.

Not sure what temperature Mars would be at 90mb of just C02 but i would guess maybe 5c something like that.

From the reading i have done on clathrates on Mars in the last while recent opinion seems to think most of it is just h20, just some C02, trace amounts of methane N2 etc.

As for clathrates totals on Mars, if it's mostly frozen H20 we will be well below 70mb of C02.
This isn't a big issue other than having to replace that total of greenhouse heating with other gasses.

I agree total on the N2 import on Mars, everything we can do to lower the needs of a filler gas would be welcomed on Mars.

I think the best thing we can do is make Mars a lower pressure world that stays warm with no more than 15% of the final gas being C02.
Whatever that pressure is it should be safe for most forms of life and have the ability to absorb most of the UV in the atmosphere.

The N2 import burden of a thicker atmosphere i think kills the idea of a 300 or 400 or 500mb atmosphere.
We should probably aim for maybe 150mb total atmosphere that requires only 45 mb of N2 import. (still a lot)

SpaceNut · 2008-02-29 23:15:57

Back last year there was a mining acident and in that was a descision of what was a breathable atmospher for survival.

"Normal oxygen is 21 percent," he said. "Once you get down to 15 percent you start having effects, and at 7 1/2 percent, it would not support life very long."

Of course we all know that Earth has these details

Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor.

What are the effects of lower air pressure?

It is essential to control the levels of oxygen and carbon dioxide as an excess of either of them can produce unfavourable results. For example when the partial pressure of oxygen is as low as 13.75kPa, virtually everyone will experience altitude sickness including shortness of breath, headaches, insomnia, impaired ability to concentrate or perform complex tasks, and sometimes nausea and vomiting. The physiological effects of high levels of carbon dioxide include increased respiration rate, heart rate, and blood flow to the brain; hearing losses; mental depression; headaches; dizziness; nausea and ultimately unconsciousness.

How do we react to to much CO2?

"Carbon Dioxide (CO2) is the body's regulator of the breathing function. It is normally present in the air at a concentration of 0.03% by volume. Any increase above this level will cause accelerated breathing and heart rate. A concentration of 10% can cause respiratory paralysis and death within a few minutes.

Terraformer · 2008-03-01 05:43:53

Any graphs showing the effects of higher CO2 on breathing?

nickname · 2008-03-01 06:45:15

SpaceNut,

15% C02 only in a 150mb atmosphere with 55% O2.
As we lower the bar pressure we can sneak up C02 levels that would be toxic on Earth.

It's an even worse formula for C02 than you would expect on Earth.
2% C02 is getting close to what most forms of life can tolerate all the time on Earth, 5% for short terms.

I think 15% C02 is pushing right on an absolute maximum for Mars with 150mb.
10% or less would be much better.

I don't think we have any chance of C02 15mb or even 22.5mb getting or keeping Mars warm.
Think we are stuck with not only having to import N2 as buffer gas, but we will have to import or create maybe 2mb of super greenhouse gasses for warming.

I've tried to keep the mb pressure as low as i can to keep importation of N2 down as small as possible.
Each 100mb increase of atmospheric pressure total for Mars equals 30 mb of N2 import.
I think 150 mb pressure and most of life would adapt to it.

150mb pressure also has a different boil point of water, i don't think it would come into play on Mars but something to keep in mind before we get to 150mb.

No reason we couldn't continue to import N2 even after the 150 mb pressure is reached.
Adding more of N2 beyond 150mb wont alter the makeup of the atmosphere in any adverse way, so we could keep adding N2 until it's at earthlike levels as a permanent project.

noosfractal · 2008-03-01 09:26:58

Sorry I'm new here. Do you have a previous post discussing the effects of blood acidosis (CO2 poising).
I've have the ID that anything above 1000 partspermillion of CO2 in the atmosphere mixture will have serious health effects if breathed over a lifetherm

Here you go dunwich ...

http://newmars.com/forums/viewtopic.php?p=105214#105214

... it is just a little earlier in this thread.

The post is by Midoshi

http://newmars.com/forums/search.php?se … or=Midoshi

dunwich · 2008-03-01 13:37:04

Here you go dunwich ...

thx noosfractal that's real interesting.

Perhaps a insignificant quistion but Mars today has a 95%CO2 3%N2 atmosphere, Venus has a 96.5%CO2 and 3.5%N2 atmosphere.
With the exeptation of density their pretty much the same. Is there some little rule in this or yust coincidense?

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