Terraforming the Moon?

[Aethon]

I'm loath to enter a thread where PB666 has posted because he knows everything, but in 1974 Richard R. Vondrak wrote an interesting paper for the journal Nature.  Unfortunately It lies behind a paywall.

http://www.nature.com/nature/journal/v248/n5450/abs/248657a0.html

 

"Vondrak calculates that if the atmosphere of the Moon was increased to a mass of at least 100,000 tons it would be driven into a “long-lived state“ which would drastically reduce losses to the solar wind. According to him:

If one wanted intentionally to create an artificial lunar atmosphere, gases can be obtained by heating or vaporization of the lunar soil. Approximately 25 megawatts are needed to produce 1 kg/sec of oxygen by soil vaporization. [Another] efficient mechanism for gas generation is subsurface mining with nuclear explosives. A 1-kiloton nuclear device will form a cavern approximately 40 meters in diameter from which 10⁷ kg of oxygen can be recovered.⁶⁵⁶

To produce a breathable “shirtsleeve“ atmosphere, about 10¹⁸ kilograms of O₂ must be pumped into the lunar environment. This should require a total energy expenditure of about 10²⁴ joules. Again, both mass and energy figures lie within the budget of an ambitious mature Type I civilization."

 

http://www.xenology.info/Xeno/19.2.1.htm

[PB666]

2 hours ago, Aethon said:

I'm loath to enter a thread where PB666 has posted because he knows everything, but in 1974 Richard R. Vondrak wrote an interesting paper for the journal Nature.  Unfortunately It lies behind a paywall.

http://www.nature.com/nature/journal/v248/n5450/abs/248657a0.html

 

"Vondrak calculates that if the atmosphere of the Moon was increased to a mass of at least 100,000 tons it would be driven into a “long-lived state“ which would drastically reduce losses to the solar wind. According to him:

If one wanted intentionally to create an artificial lunar atmosphere, gases can be obtained by heating or vaporization of the lunar soil. Approximately 25 megawatts are needed to produce 1 kg/sec of oxygen by soil vaporization. [Another] efficient mechanism for gas generation is subsurface mining with nuclear explosives. A 1-kiloton nuclear device will form a cavern approximately 40 meters in diameter from which 10⁷ kg of oxygen can be recovered.⁶⁵⁶

To produce a breathable “shirtsleeve“ atmosphere, about 10¹⁸ kilograms of O₂ must be pumped into the lunar environment. This should require a total energy expenditure of about 10²⁴ joules. Again, both mass and energy figures lie within the budget of an ambitious mature Type I civilization."

 

http://www.xenology.info/Xeno/19.2.1.htm

This comes from the guy who thinks sentient life are a dime a dozen in our galaxy.. Nature, unfortunately has no credentials with me. Some of the worst examples of bad science were published in nature. If you want life to exist around every corner you will tend to see it, the facts however speak for themselves. I don't like bad guesses. 

[cantab]

Well let's try and put some numbers on it.

Main source: sci.esa.int/science-e/www/object/doc.cfm?fobjectid=50647

Crunching the equations for Jeans escape:

Assuming oxygen molecules at 300 Kelvin, the expected conditions at the surface.

v₀ = 390 m/s

v_esc = 2380 m/s for the Moon

For oxygen atoms in the exosphere v₀ is more like 1000 m/s as per the source.

The exponential term in the Jean's escape formula is thus:

~10^-16 at the surface.

~10^-3 in the hypothetical exosphere.

Unfortunately it ends up very sensitive to the assumed exosphere temperature, so it's hard to make solid conclusions. But nonetheless we can continue. The terraformed Moon is not going to throw off its entire atmosphere in one big lump, but it will 'boil away' from the exosphere.

Working out the rate of escape per particle per second, essentially the chance of a particle flying free, for our assumed exosphere I get

p = 6.5

If I've got everything right, this seems to be pretty much saying that the lunar exosphere will stream off continuously, no atom will hang around for more than a fraction of a second. But then again, the exosphere is normally only a small part of the atmosphere as a whole. And shouldn't this evaporation process in a sense cool the remaining atmosphere.

Here's where I admit my logic gets very wooly. I'm going to compare to Earth. I know the thermosphere is 0.00002 times the total mass of the atmosphere. The exosphere will be even less, but I can't find a good figure. But suppose I use that thermosphere amount, then I'm expecting our Moon to lose a fraction 10^-4 of its total atmosphere ever second. And that suggests the whole thing will run off in less than a day.

!

?

I really don't know if this assessment is accurate. If it is, it suggests that there's no hope of maintaining a lunar atmosphere, not even with constant gas input. But I'm sceptical of such a result. It ends up so so sensitive to the atmospheric temperature and density profiles, and that's one thing when you're considering known atmospheres, quite another when you're trying to assess what a terraformed Moon would have.

[cantab]

Update: So there's a much more sensible way to put an upper limit on the Moon's rate of atmosphere loss: Conservation of energy.

The Moon receives about 10¹⁶ W of power from the Sun. (Solar constant times Moon's cross-sectional area).

To warm 1 kilo of oxygen gas from ~300 to ~1000K takes around 10⁶ J of energy.

Therefore solar irradiance limits the Moon to losing around 10¹⁰ kg of gas per second. There just isn't the heat available to go faster.

Now if our terraformed Moon has an atmosphere like Earth's scaled according to its surface area, that's around 10¹⁷ kg. Which means it can't escape quicker than 10¹⁰ seconds.

And that's 300 years.

That's still worryingly quick, but it's far far slower than my previous idea of an escape in a few hours! And this lets me conclude that if you have the technology and resources to go from nothing to an Earthlike lunar atmosphere within a few decades, or maybe even one or two centuries, you certainly have the capability to keep it 'topped up' even in the face of atmospheric escape.

On the other hand, if your terraforming ideas are going to take millennia, they may not have a hope.

Edited July 20, 2016 by cantab

[kerbiloid]

Btw, an oxygen atmosphere is not much breathable, unless you're going to breed lunar scorpions 10 meters long herded by teethless shepherds..
Humans also need Nitro to breathe and Hydro to drink. So, you must deliver an ocean of hydrazine to there.

[daniel l.]

1 hour ago, kerbiloid said:

Btw, an oxygen atmosphere is not much breathable, unless you're going to breed lunar scorpions 10 meters long herded by teethless shepherds..
Humans also need Nitro to breathe and Hydro to drink. So, you must deliver an ocean of hydrazine to there.

Of course, The Water could be provided by comets (Same as the atmosphere.) And the Nitrogen could perhaps be carried over from Titan by massive balloon ships that would lightly graze the Atmosphere and take in as much Nitrogen as possible before heading back to the Moon using Solar sails and gravity assists where it can eject the gas into the Lunar Atmosphere.

2 hours ago, PB666 said:

This comes from the guy who thinks sentient life are a dime a dozen in our galaxy.. Nature, unfortunately has no credentials with me. Some of the worst examples of bad science were published in nature. If you want life to exist around every corner you will tend to see it, the facts however speak for themselves. I don't like bad guesses. 

Honestly i dont think someones personal optimism should discredit him in any way, We have no means of proving that Aliens arent super common, IMHO sentient life is extremely rare, Perhaps only one or two per every galaxy cluster. But maybe why we dont hear them on the radio is that they use different undiscovered forms of communication, Perhaps quantum entanglement. 

1 hour ago, cantab said:

Well let's try and put some numbers on it.

Main source: sci.esa.int/science-e/www/object/doc.cfm?fobjectid=50647

Crunching the equations for Jeans escape:

Assuming oxygen molecules at 300 Kelvin, the expected conditions at the surface.

v₀ = 390 m/s

v_esc = 2380 m/s for the Moon

For oxygen atoms in the exosphere v₀ is more like 1000 m/s as per the source.

The exponential term in the Jean's escape formula is thus:

~10^-16 at the surface.

~10^-3 in the hypothetical exosphere.

Unfortunately it ends up very sensitive to the assumed exosphere temperature, so it's hard to make solid conclusions. But nonetheless we can continue. The terraformed Moon is not going to throw off its entire atmosphere in one big lump, but it will 'boil away' from the exosphere.

Working out the rate of escape per particle per second, essentially the chance of a particle flying free, for our assumed exosphere I get

p = 6.5

If I've got everything right, this seems to be pretty much saying that the lunar exosphere will stream off continuously, no atom will hang around for more than a fraction of a second. But then again, the exosphere is normally only a small part of the atmosphere as a whole. And shouldn't this evaporation process in a sense cool the remaining atmosphere.

Here's where I admit my logic gets very wooly. I'm going to compare to Earth. I know the thermosphere is 0.00002 times the total mass of the atmosphere. The exosphere will be even less, but I can't find a good figure. But suppose I use that thermosphere amount, then I'm expecting our Moon to lose a fraction 10^-4 of its total atmosphere ever second. And that suggests the whole thing will run off in less than a day.

!

?

I really don't know if this assessment is accurate. If it is, it suggests that there's no hope of maintaining a lunar atmosphere, not even with constant gas input. But I'm sceptical of such a result. It ends up so so sensitive to the atmospheric temperature and density profiles, and that's one thing when you're considering known atmospheres, quite another when you're trying to assess what a terraformed Moon would have.

 

1 hour ago, cantab said:

Update: So there's a much more sensible way to put an upper limit on the Moon's rate of atmosphere loss: Conservation of energy.

The Moon receives about 10¹⁶ W of power from the Sun. (Solar constant times Moon's cross-sectional area).

To warm 1 kilo of oxygen gas from ~300 to ~1000K takes around 10⁶ J of energy.

Therefore solar irradiance limits the Moon to losing around 10¹⁰ kg of gas per second. There just isn't the heat available to go faster.

Now if our terraformed Moon has an atmosphere like Earth's scaled according to its surface area, that's around 10¹⁷ kg. Which means it can't escape quicker than 10¹⁰ seconds.

And that's 300 years.

That's still worryingly quick, but it's far far slower than my previous idea of an escape in a few hours! And this lets me conclude that if you have the technology and resources to go from nothing to an Earthlike lunar atmosphere within a few decades, or maybe even one or two centuries, you certainly have the capability to keep it 'topped up' even in the face of atmospheric escape.

On the other hand, if your terraforming ideas are going to take millennia, they may not have a hope.

Wow that must have a lot of math there  Thank you for showing so much interest in this thread to do this.  

And as for the 300 years... Hmmm... What if the moon could be given a magnetic field. Would that affect it at all?

[Aethon]

43 minutes ago, daniel l. said:

"Honestly i dont think someones personal optimism should discredit him in any way, We have no means of proving that Aliens arent super common, IMHO sentient life is extremely rare "

I don't know what Pb666 is babbling about.  I've never claimed that 'sentient life is a dime a dozen'.  Just ignore anything he says.  

Back to the topic. 

[daniel l.]

Just now, Aethon said:

I don't know what Pb666 is babbling about.  I've never claimed that 'sentient life is a dime a dozen'.  Just ignore anything he says.  

Back to the topic. 

I think he was referring to the guy who wrote that paper.

[kerbiloid]

54 minutes ago, daniel l. said:

The Water could be provided by comets (Same as the atmosphere.)

Comets consist mostly of oxygen (H2O, CO2) and fly with near-escape speed. So, this means they should spend ~12 km/s to move the iceberg to the Earth orbit and then throw out 95% of its mass because they already have enough oxygen and rocks on the Moon.
It's easier just to deliver hydrogen from the Earth.

The same with nitrogen from Titan. You can calculate total dV to put a nitrogen tank onto:
1) Titan escape
2) Saturn escape
3) Earth transfer
4) near-Earth parabola-circle reorbit
And you realize that it's easier to launch the Nitro from the Earth.

So, they must deliver either ammonia or hydrazine from the Earth. The former is easier to make, the latter is easier to deliver and store.
As every launch means thousand tonnes of burnt fuel and they need to store the delivered substance, hydrazine is more relevant choice.

Edited July 20, 2016 by kerbiloid

[Green Baron]

8 hours ago, Aethon said:

I'm loath to enter a thread where PB666 has posted because he knows everything, but in 1974 Richard R. Vondrak wrote an interesting paper for the journal Nature.  Unfortunately It lies behind a paywall.

http://www.nature.com/nature/journal/v248/n5450/abs/248657a0.html

 

"Vondrak calculates that if the atmosphere of the Moon was increased to a mass of at least 100,000 tons it would be driven into a “long-lived state“ which would drastically reduce losses to the solar wind. According to him:

If one wanted intentionally to create an artificial lunar atmosphere, gases can be obtained by heating or vaporization of the lunar soil. Approximately 25 megawatts are needed to produce 1 kg/sec of oxygen by soil vaporization. [Another] efficient mechanism for gas generation is subsurface mining with nuclear explosives. A 1-kiloton nuclear device will form a cavern approximately 40 meters in diameter from which 10⁷ kg of oxygen can be recovered.⁶⁵⁶

To produce a breathable “shirtsleeve“ atmosphere, about 10¹⁸ kilograms of O₂ must be pumped into the lunar environment. This should require a total energy expenditure of about 10²⁴ joules. Again, both mass and energy figures lie within the budget of an ambitious mature Type I civilization."

 

http://www.xenology.info/Xeno/19.2.1.htm

Some scientists would give an arm to have an accepted nature paper.

But "Letters to Nature" do not go through the review process like normal papers and do not cover accepted scientific facts or doctrines taught at universities, they can be more in the "what if we" or "how could we" category. Given that 1973 was still under the impression of the Apollo program and nuclear power was kind of a golden calf you'd probably find more suggestions like this. It's a play of thoughts like the Drake-formula (which Vondrak explicitly refers to).

So if i read that with some critic thoughts in mind it comes to me that it's a nice try to get space into the public (nature has a broad coverage), the own name out and later on wave with it to a politician to ask for money.

;-)

 

Edited July 20, 2016 by Green Baron

[KerikBalm]

yea, non peer reviewed letter from 1974...

Lets not forget that the journal "science" which has a similar impact factor and reputation to nature, posted that terrible arsenic life paper just because it came from NASA - and it turned out to be complete garbage.

Quote

Wow that must have a lot of math there  Thank you for showing so much interest in this thread to do this.  

And as for the 300 years... Hmmm... What if the moon could be given a magnetic field. Would that affect it at all?

No. A magnetic field traps charged particles. It helps hold on to "water"... or rather the hydrogen from water. Water gets broken down into oxygen and hydrogen ions in the upper atmosphere. Hydrogen would escape really really easily - but because its charged, it gets deflected back to earth, and retained. Mars and Venus have lost susbstantial amounts of water this way.

His estimate is only accounting for loss of neutral gas molecules due to simple heat. A magnetic field doesn't affect this at all.

Thus his 300 year estimate is too high (but its a good approximation).

Solar wind will sputter off the upper atmosphere faster. Gas decomposition due to UV light in the upper atmosphere will cause the atmosphere to be lost faster.

We need much more math, but i think we also have to consider the rate of loss for lower temperatures. ie the gas loss when the temperature is lower.

Furthermore, he's assuming O2, which has a relatively high MW of 32. If the moon were to be terraformed, we'd need water vapor as well... its not going to be terraformed if there's no water on it. Uh oh... water has a MW of 18... its going to escape much faster (and its not linear with MW). Water vapor wouldn't last nearly as long as O2... and then you've got the already mentioned problem of photodessication which will split that water, and that hydrogen is going to escape really really easily.

A terraforemd atmosphere would also require N2 so that life can fix nitrogen from the atmosphere - MW of 28.

But wait... there's more!

Again, since we're assuming an Earth like atmosphere, we should look at the composition of Earths atmosphere. The upper levels of the thermosphere and the exosphere have atomic oxygen, not molecular oxygen - MW: 16 - that's not going to stick around long.

https://en.wikipedia.org/wiki/Allotropes_of_oxygen#Atomic_oxygen

Quote

Atomic oxygen, denoted O(3P), O(3P) or O((3)P),[1] is very reactive, as the single atoms of oxygen tend to quickly bond with nearby molecules; on Earth's surface it does not exist naturally for very long, though in outer space, the presence of plenty of ultraviolet radiation results in a low Earth orbit atmosphere in which 96% of the oxygen occurs in atomic form.

So... that estimate he gave is likely way too high. And you're going to need to top it off long before it reaches essentially zero.

Maybe it won't be a monthly affair... but it will probably be at least as common as presidential elections.

Thats a massive amount of maintainence...

Edited July 20, 2016 by KerikBalm

[Green Baron]

Water from comets hitting a body with only a thin atmosphere and low gravity (like mars) would just boil off and dissipate into space. Water on these bodies can only exist as ice and/or covered by something or encased in minerals to prevent dissipation. Btw., on earth water from comets did (probably) only contribute a small part of the surface water (those tiny little tell tale isotopes you know ... :-)), most of it did and could still come from OH-molecules in minerals. That could(!) imply: you need heavy volcanism over a few hundred million years to create an ocean and plate tectonics to maintain it. Yes, you read right, plate tectonics are an important factor in creating and maintaining our biosphere.

It's not like "just add water and oxygen, heat it a while and stir a bit" and voila, the tenants can move in. Getting processes to run in celestial body sizes is, to say the least, impractical and needs energies to create and maintain on a scale that we can only imagine.

 

Edited July 20, 2016 by Green Baron