Terraforming Other Planets?

[modest]

I prefer the term 'high atmospheric air-burst' compared to 'hitting it with comets', as I'm hoping there are already settlements there by this time. But otherwise I think we're on the same page.

 

(Unless they really can come up with a membrane!:P)

 

Yeah, I think we're on the same page.

 

I wonder how much carbon dioxide is in the typical comet. From that we could figure out how much comet mass would be initially needed to get the surface pressure up to a level where water would be liquid on the surface.

 

The water in a comet I don't think would initially help start an atmosphere because it would stay frozen on mars.

 

~modest

[Eclipse Now]

@ Moon:

we can open them up a bit. But check this out: underground cities are everywhere!

 

Underground city - Wikipedia, the free encyclopedia

 

They don't all have to look like malls. With Fred Hapgood's real estate equations in mind, and the sheer speed of giant Tunnel Boring Machines (TBM's), we can carve out big enough parks and forests and ecosystems to grow food. We can concentrate light from above to something our Earth plants like, or simply use nukes to provide grow-light power. And the materials are all there.:moon:

 

But hey: if some corporation came up with a game plan for Jovian settlements, I'm happy either way.:P

[belovelife]

67P/Churyumov-Gerasimenko

say for instance we could attach a rocket to this comet when it is far away from the sun,

and have enough time to Ignight the motor and give enough deltaV

to change it's orbit to be cought in the gravity of mars

when where and how big of a rocket would we need

 

( orbiter would probly help )

[Moontanman]

Yeah, I think we're on the same page.

 

I wonder how much carbon dioxide is in the typical comet. From that we could figure out how much comet mass would be initially needed to get the surface pressure up to a level where water would be liquid on the surface.

 

The water in a comet I don't think would initially help start an atmosphere because it would stay frozen on mars.

 

~modest

 

Close as i can find on short order....

 

Comet Coma

 

 

Scientists learned much about comets by studying Comet Halley as it passed near Earth in 1986. Five spacecraft flew past the comet and gathered information about its appearance and chemical composition. Several probes flew close enough to study the nucleus, which is normally concealed by the comet coma. The spacecraft found a roughly potato-shaped nucleus measuring about15 kilometers long. The nucleus contains equal amounts of ice and dust. About 80 percent of the ice is water ice, and frozen carbon monoxide makes up another 15 percent. Much of the remainder is frozen carbon dioxide, methane, and ammonia. Scientists believe that other comets are chemically similar.

 

and what are you going to do with all that water?

[belovelife]

?

[Turtle]

...

I wonder how much carbon dioxide is in the typical comet. From that we could figure out how much comet mass would be initially needed to get the surface pressure up to a level where water would be liquid on the surface.

 

The water in a comet I don't think would initially help start an atmosphere because it would stay frozen on mars.

 

~modest

 

since it's terra-forming we're after, i supect we want a fair amount of nitrogen as well. moreover, wouldn't we want to look for a balance of gases similar to earth? :P

 

as to the comet ice added, it can & will sublimate into the atmosphere. this was actually seen & recorded recently using the phoenix lander. Phoenix Mars Mission

[modest]

as to the comet ice added, it can & will sublimate into the atmosphere. this was actually seen & recorded recently using the phoenix lander. Phoenix Mars Mission

 

Good call. I was just intuitively guessing that the environment would be too cold and low pressure for water vapor. Bad guess :P

 

Close as i can find on short order....

 

Comet Coma

 

Scientists learned much about comets by studying Comet Halley as it passed near Earth in 1986. Five spacecraft flew past the comet and gathered information about its appearance and chemical composition. Several probes flew close enough to study the nucleus, which is normally concealed by the comet coma. The spacecraft found a roughly potato-shaped nucleus measuring about15 kilometers long. The nucleus contains equal amounts of ice and dust. About 80 percent of the ice is water ice, and frozen carbon monoxide makes up another 15 percent. Much of the remainder is frozen carbon dioxide, methane, and ammonia. Scientists believe that other comets are chemically similar.

 

 

since it's terra-forming we're after, i supect we want a fair amount of nitrogen as well. moreover, wouldn't we want to look for a balance of gases similar to earth? :moon:

 

I think any estimation is going to have an absurd amount of uncertainty, but let's see...

 

I think putting all of earth's atmosphere directly on Mars would end up with about the same surface pressure. Because of the smaller surface area the mass above a barometer would be 3 times greater, but the acceleration of gravity is only approx. 1/3 of earth—the two factors canceling out.

 

So, we might guess that we need to put half of the mass of earth's atmosphere (2.5 x 10¹⁸ kg) on mars to get a good and sustainable pressure with liquid water.

 

MM's source has the comet's nucleus containing 50% water ice, carbon monoxide, carbon dioxide, methane, and ammonia. According to wiki, the nucleus of an average comet is about 15 km across with a density of 0.6 g/cm³. So... we might guess that the average comet has about 10^13 kg of gas that would add to the atmosphere of a planet when airbursted.

 

2.5 x 10¹⁸ kg / 10¹³ kg = 250 000

 

So, we might need to hit mars with about 250,000 averaged-sized comets to get the terraforming process started. That said, if we raised the pressure a little, there's no telling how much of the frozen gasses currently on Mars' surface might evaporate helping along the process. It might be significantly less than 250,000 comets. Or, a good amount of the gasses in a comet might stay frozen on the surface of mars making much more than 250,000 necessary.

 

I really don't have the knowledge to say for sure.

 

~modest

 

EDIT: also, I'm ignoring temperature which might be the most important factor of all. Raising the temp quick could evaporate a lot of the solid stuff currently on Mars' surface.

[TheBigDog]

I think that the 250,000 might be a bit high, but after a couple hundred I think it is a moot point.

 

Mars already has an atmosphere of 2.5*10^16 kilograms. 95% CO2. If you presume that the thickness of the atmosphere needs to approximate Earth's (100 km) then the volume of Mars atmosphere would be 1.1*10^10 cubic meters, or 28.7% of the earth's atmospheric volume. That makes it closer to 125,000 comets minus the existing atmosphere and whatever gas comes out of the planet. Call it 75,000 to 100,000 comets. Of course this is assuming that 100% of each comet is trapped at atmosphere and that the impacting process of the large comets does not wreck whatever life we have established part way through the process. Would you want to live on a planet that had a city plan of being hit by tens of thousands of comets?

 

This is why I keep going back to the fact that we need to begin with a better candidate. Mars has too many things going against it. Primarily that we are about 3 billion years late.

 

Bill

[Turtle]

I prefer the term 'high atmospheric air-burst' compared to 'hitting it with comets', as I'm hoping there are already settlements there by this time. But otherwise I think we're on the same page.

 

(Unless they really can come up with a membrane!:eek_big:)

 

the reason we have air burst events on earth is because we have a sufficiently dense atmosphere. i suspect the current atmosphere on mars is too thin to cause an air burst, so you get impacts to the surface until the atmosphere is sufficiently dense. while this will add gasses, it will also kick up a lot of dust and the planet would actually cool until the dust fell out. :hyper: :eek: :eek: :doh:

 

on delivering energy to the surface i suggest solar arrays beaming electricity down as microwaves. :P :moon:

[modest]

Of course this is assuming that 100% of each comet is trapped at atmosphere and that the impacting process of the large comets does not wreck whatever life we have established part way through the process.

 

the reason we have air burst events on earth is because we have a sufficiently dense atmosphere. i suspect the current atmosphere on mars is too thin to cause an air burst, so you get impacts to the surface until the atmosphere is sufficiently dense. while this will add gasses, it will also kick up a lot of dust and the planet would actually cool until the dust fell out. :P :moon: :hyper: :eek:

 

Perhaps we could detonate the comets while they are on final approach to the planet. photodissociating the elements in the comet wouldn't be a bad outcome either. There doesn't appear (from Moontanman's source) to be any N₂ ice in a comet. But, I'm sure there is a lot of nitrogen in the rock part. If the nuke were strong enough to photodissociate that rock then the atmosphere might gain a good portion of the comet's nitrogen as a gas... :eek_big:

 

~modest

 

EDIT: I should have said "Perhaps we could detonate each comet..." to avoid the impression that I mean detonating all of them at once.

[Eclipse Now]

How stuff works says there might be 3 main strategies:

* Large orbital mirrors that will reflect sunlight and heat the Mars surface.

* Greenhouse gas-producing factories to trap solar radiation.+++

* Smashing ammonia-heavy asteroids into the planet to raise the greenhouse gas level.

 

+++ Doable in 8 centuries

 

"That depends," says Marinova, "on how fast we make the gases." According to rough calculations, "if you had 100 factories, each having the energy of a nuclear reactor, working for 100 years, you could warm Mars six to eight degrees." At that rate, to increase the average Martian temperature to the melting point of water -- it's about minus 55 degrees Celsius now -- would take about eight centuries. Actually, it wouldn't take quite that long, Marinova points out, because her calculation doesn't include the feedback effect of the CO2 that would be released as Mars got steadily warmer. "Devising more efficient artificial super-greenhouse gases will also make it faster," Marinova adds.

- Terraforming Mars

 

 

The greenhouse gases could be NF3 (17,200 times greater than Co2) or SF6 (22,800 times greater than Co2), depending on which was cheaper and which materials were more abundant on Mars for easier manufacturing.

 

The idea of actually SMASHING ammonia asteroids into Mars are interesting BUT it will slow down colonisation of the planet.

 

Space scientist Christopher McKay and Robert Zubrin, author of The Case For Mars, have also proposed a more extreme method for greenhousing Mars. They believe that hurling large, icy asteroids containing ammonia at the red planet would produce tons of greenhouse gases and water. For this to be done, nuclear thermal rocket engines would have to be somehow attached to asteroids from the outer solar system. The rockets would move the asteroids at about 4 kilometers per second, for a period of about 10 years, before the rockets would shut off and allow the 10-billion-ton asteroids to glide, unpowered, toward Mars. Energy released upon impact would be about 130 million megawatts of power. That's enough energy to power Earth for a decade.

 

If it is possible to smash an asteroid of such enormous size into Mars, the energy of one impact would raise the temperature of the planet by 3 degrees Celsius. The sudden raise in temperature would melt about a trillion tons of water, which is enough water to form a lake, with a depth of one meter, that could cover an area larger than the state of Connecticut. Several of these missions over 50 years would create a temperate climate and enough water to cover 25 percent of the planet's surface. However, the bombardment by asteroids, each releasing energy equivalent to 70,000 one-megaton hydrogen bombs, would delay human settlement of the planet for centuries.

 

So because smashing a series of huge comets into Mars would prevent colonisation for quite some centuries, I for one am against it. Air-burst or bust I say! We'll use the asteroids for atmospheric mass, not so much the heat which can come from super-greenhouse gases and space mirrors & magnifiers. If we get the colony established first they can help by running the greenhouse gas factories! It's THEIR world after all! They are there and can conduct all manner of scientific experiments for us to enjoy: such as growing a lichen across the poles which could change the albedo, absorb more heat, and hopefully release some Co2 into the atmosphere.

 

Kim Stanley Robinson had various means of adding heat.

 

They used a giant 'iris' of space mirrors to add more heat onto Mars, a smaller iris flying through the high atmosphere which acted like a magnifying glass and concentrated the suns rays down to a width of about 1km, which basically vaporised a deep channel across the planet, adding volatiles from the soil into the atmosphere. And all comets were detonated high in the atmosphere to air-burst for safety.

 

KSR assumed a fairly high level of water and frozen Co2 at the Martian poles, which also helped increase feedback loops as the planet started to warm.

 

They also had some whacky stuff going on, such as a factory just pumping out cheap wind turbines that turned the wind into heat! Some corporations even started letting off underground nukes to cook up the surface a bit!

 

Water on Mars is doable in 8 centuries through the greenhouse gas effect: but I'm guessing far less with a mix of space mirrors and other technologies if we REALLY got serious! :P

[modest]

How stuff works says there might be 3 main strategies:

* Large orbital mirrors that will reflect sunlight and heat the Mars surface.

* Greenhouse gas-producing factories to trap solar radiation.+++

* Smashing ammonia-heavy asteroids into the planet to raise the greenhouse gas level.

 

+++ Doable in 8 centuries

 

"That depends," says Marinova, "on how fast we make the gases." According to rough calculations, "if you had 100 factories, each having the energy of a nuclear reactor, working for 100 years, you could warm Mars six to eight degrees." At that rate, to increase the average Martian temperature to the melting point of water -- it's about minus 55 degrees Celsius now -- would take about eight centuries. Actually, it wouldn't take quite that long, Marinova points out, because her calculation doesn't include the feedback effect of the CO2 that would be released as Mars got steadily warmer. "Devising more efficient artificial super-greenhouse gases will also make it faster," Marinova adds.

- Terraforming Mars

 

I don't quite understand their reasoning. From reading that, I'm left with the impression that warming the martian surface would create an environment where liquid water is possible, but that isn't the case. The main problem for terraforming Mars (it seems to me) is that the pressure is too low. Mars might currently be where I've drawn the green line on water's phase diagram here,

If we raised the temperature then water would go from a solid to a gas. So, no matter how much we heated the planet we wouldn't get where we need to be until the pressure is at or above point A which looks like about 0.7 atmospheres of pressure. I was assuming that roughly half of the mass of earth's atmosphere would get it to that pressure.

 

~modest

[modest]

Nevermind, the triple point of water is .006 atmospheres. :doh: That is about Mars' atmospheric pressure now.

 

All of my reasoning about raising the pressure has been one massive brain fart that came from misreading the diagram above and not thinking about it critically

 

~modest

[Eclipse Now]

Dude, you're doing better than me. I know that water at lower pressures tends to boil: but when it does so I couldn't tell you. What's the "triple point" of water? Is that a way of saying the point where it can remain a liquid at certain atmosphere's of pressure?

 

It would be sad to lose water as an atmospheric gas because we need water to be water on the planet, but surely that would also help add both mass and greenhouse effect to the atmosphere?

[modest]

Dude, you're doing better than me.

 

Thank you for saying. I am more than a little embarrassed [gulp]

 

I know that water at lower pressures tends to boil: but when it does so I couldn't tell you. What's the "triple point" of water? Is that a way of saying the point where it can remain a liquid at certain atmosphere's of pressure?

 

You can think of the triple point as the pressure above which liquid water is possible. It is, for water, 0.006 atmospheres of pressure. If water were in an environment with less pressure then that then it would sublimate directly from a solid (ice) into a gas (water vapor) as you warm it up. I was thinking that this would be a problem for mars because I was thinking that the triple point was higher than it really is. That is to say, I was thinking that we would have to significantly increase the surface pressure in order to get liquid water at any temperature.

 

Here is a good concise description of a phase diagram: Pressure-Temperature (P-T) Diagram

 

It would be sad to lose water as an atmospheric gas because we need water to be water on the planet, but surely that would also help add both mass and greenhouse effect to the atmosphere?

 

Yeah. Raising the temperature would at the very least sublimate the frozen CO₂ and ice water which would raise the temp through greenhouse effects and the pressure, so the feedback effects could be rather large.

 

The big question with Mars in my mind is if there is enough water on the planet to make seas where we could grow something that makes oxygen. If not then comets might still be a workable solution.

 

~modest

[Eclipse Now]

It really is frustrating not knowing the amount of water on Mars. A colony there might be able to provide various scouting missions surveying for water. I wonder how much water Mars would require to generate a proper hydrological cycle? How deep would the oceans have to be to generate the right oceanic life cycles? How various plankton would survive on the lower light levels? Dang but for a 'fountain of youth': I'd love to see whether this ever played out!

[Moontanman]

All this is fascinating, air bursts of comets, melting the frozen gasses of Mars but.... what are you going to do with all the water in the comets? Most of the mass is water, for every pound of CO2 in the comet you have several pounds of water, then there is the Carbon monoxide (more than CO2 BTW) and the ammonia and methane. Sounds like a very long term project to me, hundreds of thousands of years possibly? Even after the comet bombardment has ended ;)