Terraforming the Moon?

[daniel l.]

How would the Moon be fully Terraformed? How would the habitability be maintained in the long run? And what effect would it have on Earth? Also what would the exotic environment of a Terraformed Moon be like?

[hms_warrior]

uhm....imho the gravity is to low to keep a breathable atmosphere in place. Sooooo ... not at all? You want to live on the moon, go whit subsurface-complexes/dome-cities.

[kerbiloid]

Just now, hms_warrior said:

imho the gravity is to low to keep a breathable atmosphere in place

We can dip out its inner meat, leaving its crust, then spinning it fast.
This gives a hollow Moon with normal gravity on its inner surface near equator and a gravitationally stable breathable atmosphere inside.
Linear speed on the outer equator would exceed the escape speed, of course, but it's no problem if we make an outer iron belt from its former iron core.

[Bill Phil]

How would the moon be terraformed? Hmm... Very carefully and expensively. You'll need nitrogen and oxygen, and you'll have to change the geology of the Moon. You need dirt, sand, and so on. You might want to speed it up to give it a 24 hour day, but doing that might cause the Earth to migrate outwards as well...

Gravity isn't much of an issue. Titan has a thick atmosphere, and it's only a few times the mass of our moon. But it is much colder. The atmosphere and the biosphere will likely need maintenance over the centuries.

As for the environment... I don't know.

[KerikBalm]

It can't be terraformed.

As to the suggestion about hollowing it out and spinning it up... it would just fly apart. At best you would mine material from the moon and construct an o neil cylinder with the material

[Bill Phil]

25 minutes ago, KerikBalm said:

It can't be terraformed.

It can be. Again, you need certain things, and then terraforming is possible. The low gravity is a non issue, neither is the lack of a magnetic field (although I'm not sure if Earth's surrounds it or not). But it won't be habitable while it's being terraformed.

[KerikBalm]

Just asserting that its possible doesn't make it possible.

https://en.wikipedia.org/wiki/Atmospheric_escape

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In a quantity of gas, the average velocity of a molecule is determined by temperature, but the velocities of individual molecules change as they collide with one another, gaining and losing kinetic energy. The variation in kinetic energy among the molecules is described by the Maxwell distribution. The kinetic energy and mass of a molecule determine its velocity by Ekin=12mv2{\displaystyle E_{\mathit {kin}}={\frac {1}{2}}mv^{2}}.

...

hydrogen escapes from an atmosphere more easily than carbon dioxide. Also, if the planet has a higher mass, the escape velocity is greater, and fewer particles will escape. This is why the gas giant planets still retain significant amounts of hydrogen and helium, which have largely escaped from Earth's atmosphere. ... A distant body has a cooler atmosphere, with a range of lower velocities, and less chance of escape. This helps Titan, which is small compared to Earth but further from the Sun, retain its atmosphere.

Titan's surface temperature is 93K. A terraformed world would have a surface temperature of at least 273K so that water is not forzen at 1 atmosphere. The average velocity of the gas molecules would thus be 71% higher. Meanwhile the Monn has an escape velocity 10% lower. There will also be sputtering from the solar wind, photo disassociation from light splitting gas molecules, etc.

To get 1 atmosphere of pressure, you'll need 6 times the mass of air per unit surface area, due to the moons gravity being 1/6th of earth's. But wait... its not the surface temperature that matters, its the temperature of the upper layers of the atmosphere - where the mean free path is about equal to the scale height... which happens around the base of the exosphere.

In this case, the temperature is basically just a product of proximity to the sun. On earth is about 1000 K, and Titans would probably be 1/81th of that, because it receives 1/81 the energy from the sun's light... average velocity would be about 9 times lower.

9 times lower particle velocity plus 11% higher escape velocity = you can't use titan as an argument for Earth's moon being able to hold on to an atmosphere.

Shift

I guess you could give the Moon an atmosphere of Xenon, which is an ok buffer gas, and then you could walk around without a pressure suit with your own O2 supply... but I don't think even that graph is right because its considering surface temperature rather than the temperature of the upper atmosphere - and that relationship is not fixed depending on greenhouse gas layers, albedo, etc... none of which really effect the temperature in the upper atmosphere where the gas is actually being lost.

Edited July 19, 2016 by KerikBalm

[magnemoe]

Closest you could get would be to put an dome over some of the large craters. The pressure inside could do most of the supporting. 

 

[Bill Phil]

@KerikBalm

Just asserting that it isn't possible doesn't make it so, either.

No one's saying that it's going to stay terraformed forever. The atmosphere will escape over time, but not all at once. If you dump a large enough amount, it'll stay there for a long while on the human scale. Geologically not very long, but adding more atmosphere over time would be required maintenance. So, it can be terraformed. And if we had the resources, and the crazyness, we could build a sphere around the Moon to help hold the atmosphere.

I'm saying that if you say gravity is the problem, there's Titan to prove that gravity isn't the issue. It has less surface gravity than the Moon and has an atmosphere thicker than Earth. But it's a lot colder there, so the atmosphere is less likely to escape than on the Moon.

Temperature is not heat energy. It's a measure of heat energy. But, temperature is also based on the amount of matter, the volume, the pressure, and other factors. In Earth's upper atmosphere, the temperature varies. The average for space is a few Kelvin, but it obviously gets hotter the closer to a star you get. Up at the Karman Line, the temperature is close to 200 Kelvin, and it's likely going to be similar on the Moon's Karman Line, down here it's obviously higher than 273. Average velocity of Oxygen molecules at 200K is way less than Earth escape velocity, and still less than Lunar escape velocity. But that's only average, there are variations in speed, so there will be a rate of escape.

[KerikBalm]

1 minute ago, Bill Phil said:

@KerikBalm

Just asserting that it isn't possible doesn't make it so, either.

Well, as you can see, I've provided a lot of justification for why its not. You haven't argued for why it is.

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No one's saying that it's going to stay terraformed forever. The atmosphere will escape over time, but not all at once. If you dump a large enough amount, it'll stay there for a long while on the human scale.

Given the estimates for mars are only on the thousands of years, and the moon has a significantly lower escape velocity with significantly higher exposure to radiation (uv and particle)... it won't last long at all. Mars' first atmosphere lasted longer due to natural "maintenance" but volcanic outgassing... which it no longer has, nor does the moon.

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Geologically not very long, but adding more atmosphere over time would be required maintenance. So, it can be terraformed. And if we had the resources, and the crazyness, we could build a sphere around the Moon to help hold the atmosphere.

Adding more atmosphere... constantly... every few decades... it would be enormously wasteful given that you need 6x the mass of air per unit surface area. Also considering the dV to get to the Moon vs Mars, why the heck would you do this?

Adding a glass dome would make this work at first glance, I suppose... but now you've got to deal with meteors, and presumably spacecraft... it seems unworkable. Do your spacecraft launch and land from the surface of the dome? how tall do you build the dome? given that the structural requirements will go up to the power of 2 as you make it higher, but you presumably want it high enough to allow clouds and precipitation and a water cycle..

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I'm saying that if you say gravity is the problem, there's Titan to prove that gravity isn't the issue. It has less surface gravity than the Moon and has an atmosphere thicker than Earth. But it's a lot colder there, so the atmosphere is less likely to escape than on the Moon.

Gravity is an issue and titan proves nothing. Terraforming requires a minimum temperature. That temperature requires a minimum escape velocity, which requires a certain gravity. Titan is below the minimum temperature and thus proves nothing about terraforming.

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Temperature is not heat energy. It's a measure of heat energy. But, temperature is also based on the amount of matter, the volume, the pressure, and other factors.

Temperature is not based on pressure. It is not based on the amount of matter, nor volume. It correlated with average velocity of the gas molecules, which is what is imporant.

You may be thinking of PV=nRT.. but 300K gas is 300K gas whether its at 5 atmospheres or 0.5 atmospheres. The ideal gas laws describe how a gas will act when you change one parameter... but again, Nitrogen at 300 K will have a certain average velocity whether you have 5 kilos of it, or 5000, whether its at 0.1 atmosphere, or 10 atmospheres.

The only thing relevant to this discussion is the molecular weight of the gas... but as we're talking terraforming, those gases are already more or less fixed. It needs to be able to retain water vapor, nitrogen gas, O2, and carbon dioxide, and it needs to have them at a certain temperature - or its not terraformed.

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In Earth's upper atmosphere, the temperature varies. The average for space is a few Kelvin, but it obviously gets hotter the closer to a star you get. Up at the Karman Line, the temperature is close to 200 Kelvin, and it's likely going to be similar on the Moon's Karman Line, down here it's obviously higher than 273. Average velocity of Oxygen molecules at 200K is way less than Earth escape velocity, and still less than Lunar escape velocity. But that's only average, there are variations in speed, so there will be a rate of escape.

blah bla blah, none of that is relevant.

The Karman line is not relevant here.

https://en.wikipedia.org/wiki/Exosphere#Lower_boundary

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at this position the mean free path of a molecule is equal to one pressure scale height.

^ the above is what is relevant for atmospheric escape. Go back and read the link on atmospheric escape from my previous post. What is relevant is at the base of the exosphere, which is in the 1000K region of earth's atmosphere... although it gets much hotter during the day, of course (over 2500 K... those molecules would all be gone from the moon, or Titan)

[PB666]

We are arguing about this because? Moon, terraform, no.

[FungusForge]

Even if we could, because of magical technologies probably, making the moon heavy enough to support an atmosphere, and have a comfortable surface gravity of 9.8 m/s would massively screw with tides, and possibly orbits. This means you'd either have to move the Moon, or build even more magical countermeasures to prevent the Moon's heavier gravity from having any significant effect, which upon a single malfunction, would have catastrophic, possibly even apocalyptic effects on Earth.

As for the suggestion of hollowing the Moon and spinning it; even if it didn't vaporize from the forces involved, that'd only provide Earth gravity to the equator, as you moved towards the poles, gravity would gradually decrease. You'd be better off building a giant ring to spin around the Moon. Same effect, but you can still use elevators to get to the surface, and as a bonus, use the spinning to chuck craft away from the Moon.

[p1t1o]

Finding several thousand billion tons of atmosphere from somewhere is hard enough...you want to...hollow it out and spin it? Before it immediately collapses and without it immediately flying apart like it was made of jelly? Is this before or after we deconstruct Jupiter to build a Dyson Sphere?

Edited July 19, 2016 by p1t1o

[Kraken1]

My sort of take on terraforming the moon is a bit odd perhaps. The domes are nice, but yeah you would need to make the glass pretty dang thick, and then there's the problem of maintenance on the glass. You can't just *poof* the glass and fix it. However, you might just need 2 very large layers of glass (oh... probably 10 feet on each.) seperated by a human sized or larger space. That's mostly so you don't have to worry about the top layer breaking and then everyone  dying. We're not exactly worried about gravity instability for the dome are we? The holes made from larger meteorites are gonna be there because there's no (notable) atmosphere to slow it down (Unless we do this atmosphere thing you guys talk about) and if there IS an atmosphere, it's not gonna be an issue for spaceflight. We would already be mining the moon for its resources, and assuming we find the right things there, we can make rocket fuel. Not to mention that by the time we're able to terraform the moon, I'm sure we have better alternatives to current rocket fuel, or it's just really REALLY advanced engines we're using. Also, lunar space elevators. That's your dome fix. Considering how a lunar space elevator is waaay easier than a earth space elevator, yeah it's a pretty good idea. Problem being that does sort of limit the choices for the dome locations to around the equator. (Unless of course we figure out how to adjust in the higher latitudes.) That would all probably be a mostly temporary sort of thing until terraforming REALLY takes place. I mean it would be an expensive place to terraform if you don't give the moon some mass so it can keep an atmosphere.      Speaking of which, wouldn't asteroids be easier to use for terraforming further away from earth? I'm not entirely sure plopping asteroids on the lunar surface is going to be enough to make notable mass changes, but it's that or hauling a lot of rocks up conventionally.

[p1t1o]

Another alternative - build a swarm of standalone orbital colonies utilising the entire mass of the moon, ringing planet Earth. Still kinda falls in the category of "terraforming" but just a bit more...granular. No problem with asteroids due to distributed hardware. Only one or two colonies would be in peril at a time and they could be moved out of the way. No problem with atmosphere as there is plenty of oxygen in the moon to supply the billions of habitats with enough breathing gas. Gravity not a problem as now each colony is individually small enough to be spun up without requiring exotic materials to hold them together.

[PB666]

You don't build domes.

You drill into the moon and you make underground caverns possibly a kilometer under ground. Having about 10 airlocks between the ground and surface. Your underground habitat is going to be completely lit by LEDs for the horticulture and lighting of choice for everything else.

Glass domes are not the answer, there is no way to convect the heat away and radiation is very slow, the moon is lit for 15 days on one side and then 15 days of darkness. Therefore sunlight is as about as useful for horticulture as a screen door on a submarine. So you allow the solar panels to take the brunt of the insolation. In addition glass does not kick out enough of the cosmic radiation to protect the astronauts, note that leaded glass is only useful for gamma type radiation, its ineffective against cosmic radiation, in that respect you need thickness as well as nuclear densities.

So we can just forget about all of these 1920's to 1960's, buck rodgers in the 21st century plans.

Next you need a airconditioning and heating system. Start by have a suntracker, several reflectors that face the sun and the radiators that track the perpendicular.
Next you need a really good batteries or a bank of NTGs or someday fusion. Alternatively you could have your outpost on the poles. However having looked at the inclination of moons rotation relative to the earth moon orbital plane about the sun, there will also have periods were there is no sunlight.

We haven't yet talked about sustainability, this is a whole nother issue.

This is not lost in space stuff, you don't get in your all glass family station wagon and go wandering about the moon, not unless you want your kids children to look like thalidomide babies.

 

Think about the problems first

15 days of sunlight 15 days off
At peak surface temperatures are 100s of degrees above earths average, at the minimum they are hundreds of degrees below.
Surface pressure is zero.
Convection is zero.
Radiation along the perpendicular is going to be about 10% at nomimal temperature that of insolance radiation.
Cosmic radiation comes during solar storms and from all directions in space, for a colony a supernova within 100 light years would be catastrophic. There is no surface defense.
The wavelengths of the sun, unfiltered except through glass are relatively harmful to plants, plants only use about 20 to 30 percent of the energy from the sun, the rest inhibits growth, so all light needs to be filtered or reproduce for maximal efficiency.
The moon does not rotate along the orbital plane of the sun.

These are the problems that have to be solved, they cannot be short-cutted or hand waved away. You have to deal with the survival problems first, then you can think about things like sustainability and growth.

 

 

[daniel l.]

Just for a note. With maintenance a substantial lunar atmosphere could be created and maintained. And the atmosphere could be created through Comet impacts or Thermonuclear detonations.

[Bill Phil]

6 hours ago, KerikBalm said:

Well, as you can see, I've provided a lot of justification for why its not. You haven't argued for why it is.

Given the estimates for mars are only on the thousands of years, and the moon has a significantly lower escape velocity with significantly higher exposure to radiation (uv and particle)... it won't last long at all. Mars' first atmosphere lasted longer due to natural "maintenance" but volcanic outgassing... which it no longer has, nor does the moon.

Adding more atmosphere... constantly... every few decades... it would be enormously wasteful given that you need 6x the mass of air per unit surface area. Also considering the dV to get to the Moon vs Mars, why the heck would you do this?

Adding a glass dome would make this work at first glance, I suppose... but now you've got to deal with meteors, and presumably spacecraft... it seems unworkable. Do your spacecraft launch and land from the surface of the dome? how tall do you build the dome? given that the structural requirements will go up to the power of 2 as you make it higher, but you presumably want it high enough to allow clouds and precipitation and a water cycle..

Gravity is an issue and titan proves nothing. Terraforming requires a minimum temperature. That temperature requires a minimum escape velocity, which requires a certain gravity. Titan is below the minimum temperature and thus proves nothing about terraforming.

Temperature is not based on pressure. It is not based on the amount of matter, nor volume. It correlated with average velocity of the gas molecules, which is what is imporant.

You may be thinking of PV=nRT.. but 300K gas is 300K gas whether its at 5 atmospheres or 0.5 atmospheres. The ideal gas laws describe how a gas will act when you change one parameter... but again, Nitrogen at 300 K will have a certain average velocity whether you have 5 kilos of it, or 5000, whether its at 0.1 atmosphere, or 10 atmospheres.

The only thing relevant to this discussion is the molecular weight of the gas... but as we're talking terraforming, those gases are already more or less fixed. It needs to be able to retain water vapor, nitrogen gas, O2, and carbon dioxide, and it needs to have them at a certain temperature - or its not terraformed.

blah bla blah, none of that is relevant.

The Karman line is not relevant here.

https://en.wikipedia.org/wiki/Exosphere#Lower_boundary

^ the above is what is relevant for atmospheric escape. Go back and read the link on atmospheric escape from my previous post. What is relevant is at the base of the exosphere, which is in the 1000K region of earth's atmosphere... although it gets much hotter during the day, of course (over 2500 K... those molecules would all be gone from the moon, or Titan)

 

I have argued for why it is, while you have pointed out something that I already accounted for.

Mars's escape velocity is only a few km/s higher than the Moon's. And you've made the point that there would have to be a higher mass of atmosphere to get the right pressure. That would also take much longer to dissipate.

Adding more atmosphere constantly every half a century or so. Maybe much longer.

Adding a sphere around the Moon would be crazy, as I already said, but it would prevent the atmosphere from leaving. Of course, now you've got a lot of engineering hurdles.

Gravity is NOT the issue. Titan proves exactly that. Distance from the sun/temperature is the issue.

Temperature has a lot to do with pressure. Plenty of relationships have been found and are well documented. It also has to do with mass, specific heat and whatnot.

A lot of that IS relevant. Most of the atmosphere (that matters) is below the Karman line. There will be more mass than on Earth below the Karman line when on the Moon.

https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Pressure_and_thickness

According to the article, over 99.99997% is below the Karman line. 90% is below 16 km. Now, that's here on Earth, not the Moon, but the deviation won't likely be over 1%.

Let's assume we lose all of the atmosphere outside the Karman line every day. That's a loss rate of 0.00003% per day. 99.99997% remains per day. 0.9999997 times our atmo's mass is left every day. Relative to the initial value, after one year, 365 days, 0.99989 remains. After 3650 days (ten years), 0.9989 remains. After 36500 days (one hundred years), 0.9891 remains. 98.91 % of our atmosphere is still there after a century. And we're losing everything that's above the Karman line, where the temperature is extremely high as you've pointed out.

And I have read the link you provided.

So, it is doable, and it'll stay there for a while. It'll need lots of maintenance, though.

Now, with all that, I'm an O'neill Cylinder guy. Planets/moons aren't all that good. And it's insane to Terraform the Moon. But it can be done.

[PB666]

1 hour ago, daniel l. said:

Just for a note. With maintenance a substantial lunar atmosphere could be created and maintained. And the atmosphere could be created through Comet impacts or Thermonuclear detonations.

The moon has been struck many times by comets, it has no atmosphere. Thermonuclear detonations will neither create an atmosphere.

 

[KerikBalm]

14 minutes ago, Bill Phil said:

Mars's escape velocity is only a few km/s higher than the Moon's.

"only a few km/sec" hahahah. 5.0 km/sec vs 2.4 km/sec. Its *more than double* while receiving less than half the energy from the sun

 

14 minutes ago, Bill Phil said:

Gravity is NOT the issue. Titan proves exactly that. Distance from the sun/temperature is the issue.

Gravity at a certain temperature is the issue. You could move Saturn to Earth's orbit, and it would still keep its atmosphere. Move titan to earth's orbit, and that atmosphere will be gone in short order. The combination is the issue - except in this case with the moon, the distance from the sun is fixed... the difference between earth(with a substantial atmosphere) and the moon (with no atmosphere) is not distance from the sun, its mass/gravity/escape velocity. That is *exactly* the relevant issue here.

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Temperature has a lot to do with pressure. Plenty of relationships have been found and are well documented. It also has to do with mass, specific heat and whatnot.

All the relationships (like PV=nRT) are not relevant here. What is relevant is the velocity of a gas molecule. That depends only on temperature and molecular weight. Pressure has nothing to do with it. As we're talking about a terraformed atmosphere, the MWs of the gases are fixed. The only variable is temperature. Everything else you bring up is a distraction to get away from the relevant parameters because when you actually look at the physics, your argument falls apart.

 

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A lot of that IS relevant. Most of the atmosphere (that matters) is below the Karman line. There will be more mass than on Earth below the Karman line when on the Moon.

https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Pressure_and_thickness

According to the article, over 99.99997% is below the Karman line. 90% is below 16 km. Now, that's here on Earth, not the Moon, but the deviation won't likely be over 1%.

Let's assume we lose all of the atmosphere outside the Karman line every day.

Lose it every day? how about every second? If the average gas molecule is traveling above escape velocity, and doesn't colide with anything else to lose KE/velocity, then its gone in seconds... and when its leaving, its not going to be stopping stuff below it from leaving, which leaves too.... and so on until the gas temperature is low enough to be below escape velocity... everything above that starts escaping almost instantly... then its a matter of how fast the lower layers heat up as the recently escaped upper layers did... and thats not long given the low thermal inertia of a diffuse gas, and the sun pumping more than 1.35 kW into every square meter.

So... lets say you lose it every second, not every day... now thats 3600 seconds per hour, 24 hours per day... this estimate is 86,400x higher than your estimate.

Now that 0.00003% per day becomes 2.592% per day... the atmosphere doesn't last long at all in that case... not even a year. Of course, I'm using all the mass below the Karman line as if its above escape velocity, but we need to look at just the thermosphere and above... but the outlook isn't much better.

Your maintenence isn't even going to be a yearly affair... its going to be monthly...that atmosphere will be gone in short order.

 

 

 

[Green Baron]

 

Ehmm, guys & gals, you are aware that "terraforming" is totally and utterly fiction. I mean, every thought is allowed of course and i have read last century's sf authors as well (liked particularly Stanislaw Lem), but it seems to me that the borders between reality and fantasy sometimes get a little blurry, or am i mistaken ?

Really, i mean no offense ... call me a spoilsport ... just sayin' ... everything's allowed ... just go ahead ... don't even ignore me :-)

 

[PB666]

2 hours ago, KerikBalm said:

"only a few km/sec" hahahah. 5.0 km/sec vs 2.4 km/sec. Its *more than double* while receiving less than half the energy from the sun

AND Mars has already lost most of its atmosphere. 3 strikes and he's out.

Edited July 19, 2016 by PB666

[daniel l.]

2 hours ago, PB666 said:

The moon has been struck many times by comets, it has no atmosphere. Thermonuclear detonations will neither create an atmosphere.

 

I also said maintain. Those impacts were long enough ago that any atmosphere would have decayed by now.

[KerikBalm]

Yea, the impacts were more than a year ago...

And impacts from comets are likely to blow off more atmosphere than they'd deposit... they certainly would now.

[daniel l.]

Just now, KerikBalm said:

Yea, the impacts were more than a year ago...

And impacts from comets are likely to blow off more atmosphere than they'd deposit... they certainly would now.

Mostly small impacts at a speed that would blow away any added atmosphere.