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Terraforming Mars» Forums » General

Subject: Martian Pressure rss

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Andy Daglish
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Solar wind removes about 100g of Martian atmospheric gas a second, which is why average atmospheric pressure on Mars is 6 millibars or 600 pascals, of mostly carbon dioxide [Earth pressure is one bar, or 1000 millibars, or 100,000 pascals]. Two interesting effects at this pressure are that water freezes [ie. becomes solid] at slightly less than zero centigrade, BUT it never becomes liquid, at any temperature. As ice heats up at 6mB it sublimates straight to gas, and vice versa as the temperature falls. Water first begins to appear at 6.1 mB pressure, but only between 0-2 degrees C, above which temp it boils away as a gas. As pressure increases, the temperature range of liquid water expands. Clearly at 1000 mB the range is 0-100C.

Martian gravity is a third of that of Earth, so a pocket of gas on Mars would weight three times as much on Earth, and exert three times the pressure; or, to get 1 bar of pressure on Mars, you need three times as much Earth-type atmospheric gas, or gas which is three times denser, or a combination of the two. In Terraforming Mars, the 1% oxygen box represents 10mB of Earthen pressure, which is 3-4 mB of pressure on Mars. At some point we might start to worry about explosive concentrations, combined with fine dust [explosive in itself due to the very high surface area to volume ratio, of tiny dust particles], with Martian lightning as a very effective source of ignition. Ka-Boom.

An expansion might address overall Martian atmospheric pressure.

Card 015 Equatorial Magnetizer is a tad disingenuous since this would be the very first terraforming step taken, to prevent that 100g a second loss. I doubt it would require "superconducting wires", as only a very weak artificial magnetosphere would be required to deflect solar wind. Card 007 Martian Rails seems to be the same thing: a planet-encompassing rail-ring could double as the necessary gaussing ring, as well as a planetary electricity conduit. It may be these monorails that the very first martian construction robots install, apart from the power station that makes them go, obviously, transmitting its power down the rail already built. How fast can mid-21st century extra-planetary robots set things up?

Beaming energy through the Martian atmosphere, especially high energy radiations such as ultra-violet, will promote chemical reactions which may impart escape velocity to the lighter molecular products. Asteroidal, lunar or cometary penetrations of the atmosphere would knock away large amounts of gas. A comet of many square miles moving at 14,000 miles a second would impact with an energy so great that it would probably destroy everything nearby or at least dump vast amount of ejecta on it, as well as into the atmosphere. It would be best to do this sort of thing first, if at all, and then wait to measure the effects.

PS: Beagle 2 landed as far from the Terraforming Mars map as it possibly could.

PPS: I thought on Ganymede Jupiter would cover three-quarters of the sky, though that may be a 1950s estimate. And therefore wrong! Radiations from the giant planet would however fry everything nearby, so heavy shielding would be required.
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Örjan Almén
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Meaning what? What does this mean in the context of the game?
 
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Donny Behne
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aforandy wrote:
Solar wind removes about 100g of Martian atmospheric gas a second, which is why average atmospheric pressure on Mars is 6 millibars or 600 pascals, of mostly carbon dioxide [Earth pressure is one bar, or 1000 millibars, or 100,000 pascals]. Two interesting effects at this pressure are that water freezes [ie. becomes solid] at slightly less than zero centigrade, BUT it never becomes liquid, at any temperature. As ice heats up at 6mB it sublimates straight to gas, and vice versa as the temperature falls. Water first begins to appear at 6.1 mB pressure, but only between 0-2 degrees C, above which temp it boils away as a gas. As pressure increases, the temperature range of liquid water expands. Clearly at 1000 mB the range is 0-100C.

Martian gravity is a third of that of Earth, so a pocket of gas on Mars would weight three times as much on Earth, and exert three times the pressure; or, to get 1 bar of pressure on Mars, you need three times as much Earth-type atmospheric gas, or gas which is three times denser, or a combination of the two. In Terraforming Mars, the 1% oxygen box represents 10mB of Earthen pressure, which is 3-4 mB of pressure on Mars. At some point we might start to worry about explosive concentrations, combined with fine dust [explosive in itself due to the very high surface area to volume ratio, of tiny dust particles], with Martian lightning as a very effective source of ignition. Ka-Boom.

An expansion might address overall Martian atmospheric pressure.

Card 015 Equatorial Magnetizer is a tad disingenuous since this would be the very first terraforming step taken, to prevent that 100g a second loss. I doubt it would require "superconducting wires", as only a very weak artificial magnetosphere would be required to deflect solar wind. Card 007 Martian Rails seems to be the same thing: a planet-encompassing rail-ring could double as the necessary gaussing ring, as well as a planetary electricity conduit. It may be these monorails that the very first martian construction robots install, apart from the power station that makes them go, obviously, transmitting its power down the rail already built. How fast can mid-21st century extra-planetary robots set things up?

Beaming energy through the Martian atmosphere, especially high energy radiations such as ultra-violet, will promote chemical reactions which may impart escape velocity to the lighter molecular products. Asteroidal, lunar or cometary penetrations of the atmosphere would knock away large amounts of gas. A comet of many square miles moving at 14,000 miles a second would impact with an energy so great that it would probably destroy everything nearby or at least dump vast amount of ejecta on it, as well as into the atmosphere. It would be best to do this sort of thing first, if at all, and then wait to measure the effects.

PS: Beagle 2 landed as far from the Terraforming Mars map as it possibly could.

PPS: I thought on Ganymede Jupiter would cover three-quarters of the sky, though that may be a 1950s estimate. And therefore wrong! Radiations from the giant planet would however fry everything nearby, so heavy shielding would be required.


This is awesome. I love stuff like this, thanks!
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Jeremy DuCharme

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I haven't played many games yet, but my last one I got a card, release of inert gasses. Basically building up atmospheric density, it gave a straight bonus to my terraforming rating.
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Matthieu Fontaines
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That's the kind of things I love in this game... all the scientific chat around
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Jacob Fryxelius
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aforandy wrote:
Solar wind removes about 100g of Martian atmospheric gas a second, which is why average atmospheric pressure on Mars is 6 millibars or 600 pascals, of mostly carbon dioxide [Earth pressure is one bar, or 1000 millibars, or 100,000 pascals]. Two interesting effects at this pressure are that water freezes [ie. becomes solid] at slightly less than zero centigrade, BUT it never becomes liquid, at any temperature. As ice heats up at 6mB it sublimates straight to gas, and vice versa as the temperature falls. Water first begins to appear at 6.1 mB pressure, but only between 0-2 degrees C, above which temp it boils away as a gas. As pressure increases, the temperature range of liquid water expands. Clearly at 1000 mB the range is 0-100C.

Martian gravity is a third of that of Earth, so a pocket of gas on Mars would weight three times as much on Earth, and exert three times the pressure; or, to get 1 bar of pressure on Mars, you need three times as much Earth-type atmospheric gas, or gas which is three times denser, or a combination of the two. In Terraforming Mars, the 1% oxygen box represents 10mB of Earthen pressure, which is 3-4 mB of pressure on Mars. At some point we might start to worry about explosive concentrations, combined with fine dust [explosive in itself due to the very high surface area to volume ratio, of tiny dust particles], with Martian lightning as a very effective source of ignition. Ka-Boom.

An expansion might address overall Martian atmospheric pressure.

Card 015 Equatorial Magnetizer is a tad disingenuous since this would be the very first terraforming step taken, to prevent that 100g a second loss. I doubt it would require "superconducting wires", as only a very weak artificial magnetosphere would be required to deflect solar wind. Card 007 Martian Rails seems to be the same thing: a planet-encompassing rail-ring could double as the necessary gaussing ring, as well as a planetary electricity conduit. It may be these monorails that the very first martian construction robots install, apart from the power station that makes them go, obviously, transmitting its power down the rail already built. How fast can mid-21st century extra-planetary robots set things up?

Beaming energy through the Martian atmosphere, especially high energy radiations such as ultra-violet, will promote chemical reactions which may impart escape velocity to the lighter molecular products. Asteroidal, lunar or cometary penetrations of the atmosphere would knock away large amounts of gas. A comet of many square miles moving at 14,000 miles a second would impact with an energy so great that it would probably destroy everything nearby or at least dump vast amount of ejecta on it, as well as into the atmosphere. It would be best to do this sort of thing first, if at all, and then wait to measure the effects.

PS: Beagle 2 landed as far from the Terraforming Mars map as it possibly could.

PPS: I thought on Ganymede Jupiter would cover three-quarters of the sky, though that may be a 1950s estimate. And therefore wrong! Radiations from the giant planet would however fry everything nearby, so heavy shielding would be required.

I love this post! Ah, to discuss some science!

For sure, the pressure needs to be built, and it will require more gas than it would on Earth because of the low gravity. The 14% goal in Terraforming Mars refers to a breathable concentration and would be 14*10mB ON MARS. At this concentration, the atmosphere is far from dangerous to fires, even less so than Earth's atmosphere, because of the lower concentration. Tha fact that Mars will have a higher ratio of oxygen is moot because the difference is that on Mars you'd have 'vacuum' instead of nitrogen, and neither of these can feed fires.

But, there sure needs to be higher air pressure than just that coming from the oxygen. That's why we have the cards Release Inert Gases, Imported Nitrogen, and Nitrite-Reducing Bacteria in the game. Still, there is no need to reach 1000mB. I think about half might be barely enough.

The Equatorial Magnetizer does indeed need superconductors, since only a direct current can create a stable magnetic field able to deflect ionized particles. And direct current loses lots of energy on longer distances (that's why we have alternating current instead). Furthermore, I believe you'd need a really (like REALLY) large current to create a global magnetic field. Especially if is is to function as protection for the atmosphere, which needs to be an even thicker layer than that of Earth in order to have enough pressure at the surface.

On the other hand, I think atmospheric loss is a minor problem because it works on so large time-scales; we'll have time to figure it our and replenish the atmosphere as we go.

That asteroids should be handled with care is something I agree with, but it's very hard to convince my CEO. He can only see the beautiful headlines:
'Incoming! Millions watched as the meteor drew a smoky line down into the southern hills where a dubious corporation is rumored to grow experimental fungi. The explosion was followed by a loud cheer!'.

Cheers!
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Scott Muldoon (silentdibs)
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orjanalmen wrote:
Meaning what? What does this mean in the context of the game?

Welcome to The Andy Daglish Show. First time guest?
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Chaddyboy
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What the hell is this, some kind of Phil Eklund game?

His games are really cool, BTW.
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Andy Daglish
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orjanalmen wrote:
What does this mean in the context of the game?

Credibility.
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Andy Daglish
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Fryxen wrote:
For sure, the pressure needs to be built, and it will require more gas than it would on Earth because of the low gravity. The 14% goal in Terraforming Mars refers to a breathable concentration and would be 14*10mB ON MARS.
Isn't this equivalent to 40% oxygen on Earth?

Quote:
At this concentration, the atmosphere is far from dangerous to fires, even less so than Earth's atmosphere, because of the lower concentration.
It would help if we were talking about partial pressures. 14% on Earth is enough to combust paper.

Quote:
Tha fact that Mars will have a higher ratio of oxygen is moot because the difference is that on Mars you'd have 'vacuum' instead of nitrogen, and neither of these can feed fires.
The vacuum won't absorb energy, so more of it will be available to propogate the reaction.

Quote:
But, there sure needs to be higher air pressure than just that coming from the oxygen. That's why we have the cards Release Inert Gases, Imported Nitrogen, and Nitrite-Reducing Bacteria in the game. Still, there is no need to reach 1000mB. I think about half might be barely enough.
I think the partial pressures would have to be monitored.

Quote:
The Equatorial Magnetizer does indeed need superconductors, since only a direct current can create a stable magnetic field able to deflect ionized particles. And direct current loses lots of energy on longer distances (that's why we have alternating current instead). Furthermore, I believe you'd need a really (like REALLY) large current to create a global magnetic field. Especially if is is to function as protection for the atmosphere, which needs to be an even thicker layer than that of Earth in order to have enough pressure at the surface.
Electron magnetic moments are thousands of times stronger than those of the solar particles, so the electric current would not have to be large. But obviously an equatorial ring would be [large]. Superconduction is fine so long as that property doesn't require a lot of energy to maintain. Very low resistance might work. The extra thickness of the atmosphere won't be significant compared to the distances at which the artificial magnetosphere would deflect particles. Also a thick atmosphere would tend to absorb them.

As our moon is subject to lethal doses of solar wind, I suspect Mars might be also. Really all life needs to be underground, at first.

Quote:
On the other hand, I think atmospheric loss is a minor problem because it works on so large time-scales; we'll have time to figure it our and replenish the atmosphere as we go.
Its about 30,000 tons a year, so a slight problem initially, given the smaller volume of Mars.

Quote:
That asteroids should be handled with care is something I agree with, but it's very hard to convince my CEO. He can only see the beautiful headlines:
'Incoming! Millions watched as the meteor drew a smoky line down into the southern hills where a dubious corporation is rumored to grow experimental fungi. The explosion was followed by a loud cheer!'.
"Oh dear, thats torn it" says Sir Cuthbert Snodgrass, Astronomer Royal, as he watches newly-oxygenated Mars gradually turn sooty black behind orange-brown advancing edges.

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Ken Chaney

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Thanks for the science, Andy!

I too was troubled by the O2 gauge going to "14%" but then managed to convince myself that it was measuring the O2 partial pressure relative to One Earth atmosphere, rather than the molecular composition of the Martian atmosphere. I've managed to not be troubled about it any more, but very much appreciate the exposition of the subtle problem presented that may get into people's thinking.

I'm unclear on how vacuum coupled with O2 quenches combustion. The classic model is: fuel + heat + oxidizer = fire.
If you have fuel + heat + vacuum, you get no fire, but the idea that O2 + very little else is "mostly vacuum" doesn't work ... vacuum is nothing, but the presence of the O2 makes it not vacuum.
Having very little O2 and lots of other stuff (N2) means no fire, too, because the lots of N2 will absorb the heat from the small amount of O2 that is reacting to generate the heat ... so there is not enough energy to propagate the reactions (although some reactions require very little heat to start ... so ya gotta be careful!)

So, too much non-reacting stuff will quench a fire, vacuum will deprive it of oxidizer, but fuel, O2, and heat together ... let's be careful out there!
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Jacob Fryxelius
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Thanks for the answer, Andy!
In TM, 14% O2 is the same partial pressure of O2 as 14% O2 on Earth, i.e. 140 mB. To achieve that, you'll need a thicker layer of gas than on Earth, but on the relatively smaller surface area. This is what the human body needs to function, what will get you enough oxygen into the blood stream. It does not describe the composition of the Martian atmosphere or the composition of an Earth atmosphere with 14% O2 placed on Mars.
14% is enough to combust paper, I agree. Just like on Earth. We want that. What we don't want is an atmosphere where a spark will ignite a fire regularly.
Your point about nitrogen absorbing energy and therefore quenching the fire is very real of course (hadn't really thought about that). But you still have oxygen molecules that can absorb and spread the heat although I agree that it would be a much less efficient energy absorption than in Earth's atmosphere.
The spread out oxygen (14% compared to 21%) is also a factor, making any combustion slower, to some degree offsetting the decreased absorption from nitrogen (Fun fact: In Swedish, 'nitrogen' is called 'kväve' which means 'suffocation'.).
On the other hand, as we already agree on, the martian atmosphere needs to have a substantial amount of nitrogen and other inert gases to get a tolerable atmospheric pressure. This will help with the fire problem.
The fine dust particles might also be a problem, so we'd need ways to bind the dust (soils, oceans etc.) so it can't react with an oxygenated atmosphere. I never heard of sand starms causing fires on Earth though.

Since the magnetic field decreases with the quare of the distance, I'm not sure your assessment is correct on the large distances we are talking about (global scales). For sure, the maintainance on superconduction has to be relatively cheap for it to work.

Absorption by the atmosphere is also good protection, but isn't that also part of the problem - energizing the upper molecules enough to give some of them escape velocity? If that energy comes from entering atoms though, it might still be mass-balanced...

Looking forward to your answers!
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Matt Smith
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This thread made for wonderful lunch-time reading. Many thanks to the contributors!
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Isaac Fryxelius
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aforandy wrote:
PPS: I thought on Ganymede Jupiter would cover three-quarters of the sky, though that may be a 1950s estimate. And therefore wrong! Radiations from the giant planet would however fry everything nearby, so heavy shielding would be required.

Well, the perceived size of Jupiter is very much relative - do you see it through a wide angle lens or a zoom? It would probably look much smaller on any photo compared to how you would perceive it in reality. Anyhow, classic artist Ludek Pesek, reknowned for his accuracy, paintied Jupiter about this size from Ganymede.
PS: for more drama, check the size of Jupiter from Io mining industries...
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Matthieu Fontaines
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Speaking of magnetic fields generation.
The magnetiser is set at the equator, where most plants, cities and animals are also set.

Given the inverse square law, magnetic field near the surface will be very intense.
At least it would surely cause problems to electronics and mobile network
At worst, it would cause to DNA the same problems it tries to avoid via solar wind deflection...

I did not made computations on this one, what do other terraforming fans think about it?
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Andy Daglish
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Fryxen wrote:
Thanks for the answer, Andy!
In TM, 14% O2 is the same partial pressure of O2 as 14% O2 on Earth, i.e. 140 mB. To achieve that, you'll need a thicker layer of gas than on Earth, but on the relatively smaller surface area.

Planetary surface area plays no role.

Quote:
This is what the human body needs to function, what will get you enough oxygen into the blood stream.

'Survive unconscious/in a coma' is closer to the situation most slim, athletic muscle-bound Geeks would exhibit.

Quote:
It does not describe the composition of the Martian atmosphere or the composition of an Earth atmosphere with 14% O2 placed on Mars.

This is a confusing statement, and I think the choice of percentage points of oxygen, each representing an increment of 140mB partial pressure O2, was likely to lead to difficulty of comprehension. As a partial pressure of oxygen is entirely independent of the presence [or absence] of other gases which may be at any pressures, its rather meaningless unless we know total atmospheric pressure. Actually I think this metric should have been included in the game. Decompression sickness problems begin to emerge as pressure falls from standard terrestrial 1000mB down past 750mb, so 140mB oxygen won't influence this much.
Quote:

14% is enough to combust paper, I agree. Just like on Earth. We want that. What we don't want is an atmosphere where a spark will ignite a fire regularly. Your point about nitrogen absorbing energy and therefore quenching the fire is very real of course (hadn't really thought about that). But you still have oxygen molecules that can absorb and spread the heat although I agree that it would be a much less efficient energy absorption than in Earth's atmosphere.
The spread out oxygen (14% compared to 21%) is also a factor, making any combustion slower, to some degree offsetting the decreased absorption from nitrogen (Fun fact: In Swedish, 'nitrogen' is called 'kväve' which means 'suffocation'.).

This depends on temperature, oxygen concentration [ie. how many more volumes of energy-absorbing gases there are to quench its fiery tendencies], and the nature of the fuel.

Quote:
On the other hand, as we already agree on, the martian atmosphere needs to have a substantial amount of nitrogen and other inert gases to get a tolerable atmospheric pressure. This will help with the fire problem.


Pressure fluctuations would be problematic, as humans are sensitive to very minor changes.

Volume Mars = 28442 cubic kilometres
Earth Atmosphere = 480 kilometres thick
500mB artificial Martian atmosphere thickness = 720km
Mars diameter 6790 kilometers.
Mars artificial atmosphere volume = 31458 km cubed - 28442 = 3016 km cubed.
Earth atmosphere volume = 4189 km cubed.
Earth atmosphere weighs 5 trillion tons under Earth gravity.
Mars atmosphere weighs 3.6 trillion tons under Earth gravity, or 1.2 trillion tons under Mars gravity.

Quote:
The fine dust particles might also be a problem, so we'd need ways to bind the dust (soils, oceans etc.) so it can't react with an oxygenated atmosphere. I never heard of sand starms causing fires on Earth though.

They are all oxides of silica so won't burn, but you might get silicosis.
Quote:

Since the magnetic field decreases with the quare of the distance, I'm not sure your assessment is correct on the large distances we are talking about (global scales). For sure, the maintainance on superconduction has to be relatively cheap for it to work.

The ring would also be of global scale.

Quote:
Absorption by the atmosphere is also good protection, but isn't that also part of the problem - energizing the upper molecules enough to give some of them escape velocity? If that energy comes from entering atoms though, it might still be mass-balanced...


The trouble is you won't know what all these atomic particles are doing to each other or to the planet's surface.

Living under liquid water might give useful pressure. Complex climate control would be required.
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Jacob Fryxelius
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The surface area is only of importance when considering how much gas (tons) is needded for the total atmosphere. Quite a lot, as you so elegantly showed.

The O2 scale in TM denotes the same partial pressure that our percentage scale does for the Earth's atmopshere, which means that each percent represents 10 mB, for a total of 1000 mB for a full Earth atmosphere. The reason for using this scale is for players to have something useful to compare it to ('We have 20% on Earth, so 14% may be enough, although it'd be quite thin'), that is still relevant for living creatures. Of course, atmospheric pressure on Mars is not the same thing although also important.

On Earth, the highest city (50.000 inhabitants) is La Riconada in Peru, at 5100 meters above sea level. That has an atmospheric pressure of about 550 mB, which corresponds to around 110 mB partial pressure of oxygen. This is even lower than the 140 mB goal in TM.
Several large cities are above 3000 m (700 mB total, 140 mB oxygen), which corresponds to the goal in TM.

Quick search:
https://en.wikipedia.org/wiki/List_of_highest_cities_in_the_...
https://en.wikipedia.org/wiki/List_of_highest_large_cities
https://en.wikipedia.org/wiki/Atmospheric_pressure

Millions of people live in those cities, so I see no insurmountable problem in the goals of TM, provided that the oxygen is complemented with nitrogen to some degree to get the pressure up.

Decompression sickness is associated with sudden changes in pressure, not with living in a certain pressure. We're talking about generations here.

The reach of a magnetic field is not dependent on the ring size, but on the electric current. The ring would be global, yes, but it would still be located near the surface, whereas the magnetic field needs to protect the upper atmosphere hundreds of kilometers straight up from the ring (s). I think you'd need a really really strong current or other modifications in order for it to work. As he said, the magnetic field on the ground would be very strong, so maybe have the cables buried deep, or elevated on kilometer-high masts?

Anyway, I agree that a full treatment of terraforming should include total atmospheric pressure. It should probably also include magnetic field and a few other parameters as well.
On the other hand, I wanted to make a game that wasn't too cluttered down in details while still covering the essentials. I hope players agree with me that we made a reasonable compromise.

p.s. Living under liquid water might increase the risk of drowning...
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Ken Chaney

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Fryxen wrote:
Decompression sickness is associated with sudden changes in pressure, not with living in a certain pressure. We're talking about generations here.

The reach of a magnetic field is not dependent on the ring size, but on the electric current.


Yup on the decompression or "the bends." If you have high pressure (compared with standard atmosphere) air (basically 80% Nitrogen, 20% Oxygen) in your lungs, some of the nitrogen gets dissolved in your blood. If you drop the pressure you are under quickly (ascending from a deep dive for example) that dissolved nitrogen will no longer be dissolved in your blood, but become gas again - still in your blood stream. Painful and can be deadly!

The magnetic field strength due to a current ring will be dependent on the current, but the extent (size) of the field will scale with the size of the ring. While the strength of a field falls off quickly when considering a tiny segment of wire with a current in it or when moving away from a long straight wire, for a planetary scale ring you need to consider the whole thing. In fancy terms, you have to integrate the Biot-Savart law over the entire ring. Now the ring segments that are not too close to a particular point hundreds of kilometers above the planet surface will only make a TINY contribution due to each meter of current carrying ring, but there are a heck of a lot of those meters to add up. The result is that the field will extend effectively on the scale of the ring.
There is a nice picture/animation at http://demonstrations.wolfram.com/MagneticFieldOfACurrentLoo...
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Andy Daglish
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Fryxen wrote:
Millions of people live in those cities, so I see no insurmountable problem in the goals of TM, provided that the oxygen is complemented with nitrogen to some degree to get the pressure up.
They are genetically/phenotypically different. I'm not sure what happens when they go to sea level.

Quote:
Decompression sickness is associated with sudden changes in pressure, not with living in a certain pressure. We're talking about generations here.
Its about dying at a low pressure, which will be felt across the generations.
http://nyti.ms/2fl1Oj8

Quote:
The reach of a magnetic field is not dependent on the ring size, but on the electric current.
Rather the magnetic properties of the number of electrons forming the current, which should greatly exceed solar wind particles at one point at Mars. The ring will deflect protons and helium nuclei particularly easily, due to the previously-mentioned large ratio of magnetic moment. Clearly, as particles approach Mars, field strength becomes exponentially greater.

Quote:
p.s. Living under liquid water might increase the risk of drowning...
not by game turn 50, as by then they've developed gills.

The trouble with terraforming seems to be that it aims at a single stable result out of very many possible states resulting from human modifications. If it was successful, it would indeed take generations, but the terraformers on the planet's surface all that time would be machines. Gradually introducing humans as surface conditions move in their direction seems unlikely, as life would be more amenable underground, where you could have lots of surfaces or levels. You could live on the largest asteroids, but not on their surfaces.
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Ken Chaney

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The nyti.ms link goes to an article about ions and human effects, not long term low pressure. Got another link? I'd like to find out about it! (By the way, thanks again for the science!)
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Andy Daglish
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http://forum.nasaspaceflight.com/index.php?topic=40137

Over time deep vein thrombosis would eliminate those with a predisposition. Low pressure means low humidity. The colonists would have to drink a lot of water.

I see terrestrial bacteria can't reproduce below -15C, and slowly at -10.
 
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Rus
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Awesome discussion, but I feel like we still have not closed on a few key questions:

1. What is the minimum oxygen partial pressure requirement for long-term survival of a human colony (without oxygen masks)?

Jacob's answer is ~0.14 atm (what he calls 14%), based on the highest altitude large cities on Earth, which seems exactly the right thing to do here to get a first-order answer, even if the inhabitants may have genes slightly better adapted to that environment than the rest of humans (those could be the ones that go to Mars!) Many adults have been to skiing resorts and other high altitude locations with 14%, it's not that bad.

2. What is the minimum atmospheric pressure requirement for a long-term survival of a human colony (assuming oxygen requirement is met)? [Edit: what I mean is the minimum atmospheric pressure for the human body not to die or get sick because of a low-pressure environment, assuming that it is decompressed slowly enough that decompression shock itself is not an issue.]

The answer seems to be at least 0.06 atm (https://en.wikipedia.org/wiki/Armstrong_limit), but probably not substantially more than that. So, it appears that if we have a pure oxygen atmosphere at 0.14atm, that should satisfy both requirements 1 and 2.

3. What is the minimum partial pressure of Nitrogen (and/or other inert gases), in order to avoid catastrophic global combustion of the atmosphere with 0.14atm partial pressure of oxygen?

I have not been able to find the answer to this question, or even confirm for sure that the answer has to be >0. Does anybody know?
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Matthieu Fontaines
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rbelikov wrote:

3. What is the minimum partial pressure of Nitrogen (and/or other inert gases), in order to avoid catastrophic global combustion of the atmosphere with 0.14atm partial pressure of oxygen?

I have not been able to find the answer to this question, or even confirm for sure that the answer has to be >0. Does anybody know?


These pages:
https://en.wikipedia.org/wiki/Limiting_oxygen_concentration
and
https://en.wikipedia.org/wiki/Flammability_limit

gives some info on the subject
sadly, I don't fully understand/ have time to understand it

Maybe just considering a 21% O2 concentration would be sufficient to have an earth type flammability... So 0,7 atm of Nitrogen?
 
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Gordon Stewart
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It seems like the game's theme is really overlooking the planetary scale
forces needed to create atmosphere-protecting magnetic fields as
briefly discussed here:

http://www.iflscience.com/space/without-magnetic-field-any-l...

 
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