To Terraform or not to Terraform?

[ScholasticSpastic]

Remember, I said 60 fathoms. 360 feet down. It would not be a pleasant experience if one did get inside that balloon.

I think we agree. I was just pointing out that there'd still be volume. Just not useful volume.

[Gawdzilla Sama]

Remember, I said 60 fathoms. 360 feet down. It would not be a pleasant experience if one did get inside that balloon.

I think we agree. I was just pointing out that there'd still be volume. Just not useful volume.

Yep. Hotshot tried that trick off Puerto Rico one time. We were watching with cameras as the balloon tried to reach a size where a diver could fit inside it. Didn't work. We went back to bells at that point.

[Clinton Huxley]

The thing about balloons as habitats is that some joker would try to twist them vaguely into the shape of a poodle or giraffe and who wants to live in a poodle?

[Gawdzilla Sama]

The thing about balloons as habitats is that some joker would try to twist them vaguely into the shape of a poodle or giraffe and who wants to live in a poodle?

Or Paris Hilton's faux dog.

[Clinton Huxley]

The thing about balloons as habitats is that some joker would try to twist them vaguely into the shape of a poodle or giraffe and who wants to live in a poodle?

Or Paris Hilton's faux dog.

A Martian nano-bacterium couldn't fit inside that thing.

[mistermack]

What you're ignoring is that the atmospheric pressure on Mars is extremely low.
And the pull of gravity is much less than on Earth.
A balloon submerged in water on Mars with 1 bar pressure inside it would behave very differently to one on Earth.

1 bar on Earth wouldn't blow up a balloon at all, even at sea surface level.
On Mars 1 bar could probably inflate a balloon ten fathoms deep or more.

At that sort of depth, the inside pressure would be exactly equal to the outside pressure, making leaks and damage less likely. Also, there would be protection from radiation and solid particle damage. Degradation due to UV would be less.
And leaks could be easily identified and repaired.

[Gawdzilla Sama]

What you're ignoring is that the atmospheric pressure on Mars is extremely low.
And the pull of gravity is much less than on Earth.
A balloon submerged in water on Mars with 1 bar pressure inside it would behave very differently to one on Earth.

1 bar on Earth wouldn't blow up a balloon at all, even at sea surface level.
On Mars 1 bar could probably inflate a balloon ten fathoms deep or more.

At that sort of depth, the inside pressure would be exactly equal to the outside pressure, making leaks and damage less likely. Also, there would be protection from radiation and solid particle damage. Degradation due to UV would be less.
And leaks could be easily identified and repaired.

Why the FUCK do you want to live underwater on Mars? Please, just the once, make sense.

[ScholasticSpastic]

What you're ignoring is that the atmospheric pressure on Mars is extremely low.
And the pull of gravity is much less than on Earth.
A balloon submerged in water on Mars with 1 bar pressure inside it would behave very differently to one on Earth.

A balloon submerged in water on Mars should be expected to behave very similarly to a balloon submerged in water on Earth due to one very important fact:

The pressure on a submerged item is due to the pressure exerted by the water column plus the pressure exerted by the atmosphere above it. Ten meters of water will exert one atmosphere of pressure in addition to whatever the atmospheric pressure is for every one gravity of acceleration no matter what world we find ourselves on. Thus we should expect 30 meters of depth on Mars to be roughly equivalent in pressure to 10 meters of depth on Earth.

1 bar on Earth wouldn't blow up a balloon at all, even at sea surface level.
On Mars 1 bar could probably inflate a balloon ten fathoms deep or more.

A balloon ten fathoms deep on Mars (approx. 18 meters, to use a less annoying system of measure) would experience ~2/3 atm pressure from the water above it, plus a negligible pressure contribution from the atmosphere. So you are correct, having done the math, that the pressure exerted by ten fathoms of water on Mars would be less than 1 atm and that a balloon under 1 bar of pressure at that depth should be expected to inflate- it would contain an internal pressure 30% greater than external pressure.

At that sort of depth, the inside pressure would be exactly equal to the outside pressure, making leaks and damage less likely.

This is not correct. Internal pressure would be ~30% greater than external pressure and it would be necessary to reinforce the structure.

Also, there would be protection from radiation and solid particle damage. Degradation due to UV would be less.
And leaks could be easily identified and repaired.

One glaring deficiency in this plan is the scarcity of accessible water on Mars. We can obtain equivalent protection from radiation and solid particles by burying a structure under Martian dirt and rocks- which are substantially more accessible than water.

[mistermack]

What you're ignoring is that the atmospheric pressure on Mars is extremely low.
And the pull of gravity is much less than on Earth.
A balloon submerged in water on Mars with 1 bar pressure inside it would behave very differently to one on Earth.

1 bar on Earth wouldn't blow up a balloon at all, even at sea surface level.
On Mars 1 bar could probably inflate a balloon ten fathoms deep or more.

At that sort of depth, the inside pressure would be exactly equal to the outside pressure, making leaks and damage less likely. Also, there would be protection from radiation and solid particle damage. Degradation due to UV would be less.
And leaks could be easily identified and repaired.

Why the FUCK do you want to live underwater on Mars? Please, just the once, make sense.

Well, it's a suggestion, up for discussion. That's all.
My points in it's favour are :
1) It's actually less alien. We have more experience of it.
2) It's less dangerous. If you equalise the internal pressure with external, leaks will lose air very slowly, and will be easy to detect.
A sudden loss of pressure would normally kill everyone, due to the bends, and asphyxiation, and rapid chilling.
Living under water would make a leak a slow manageable event, and as liquid water is a massive heat sink, it would ensure stable temperatures.
It might seem a bit drastic here on earth, but on an alien planet, I think it's actually safer and more predictable.

[Gawdzilla Sama]

You have taken Rube Goldberg to space. If we live in man-made caves we don't have to worry about them deflating. And humans have had more experience living in air than in water.

As for leaks, a hydrodynamics course might be in order. If you have an air/air interface, self-sealing is a lot simpler than in a air/water interface. Water is non-compressible. It exerts equal force in all directions (this is why depth charges work) and it will aggressively exploit a leak of any size.

[mistermack]

You have taken Rube Goldberg to space. If we live in man-made caves we don't have to worry about them deflating. And humans have had more experience living in air than in water.

As for leaks, a hydrodynamics course might be in order. If you have an air/air interface, self-sealing is a lot simpler than in a air/water interface. Water is non-compressible. It exerts equal force in all directions (this is why depth charges work) and it will aggressively exploit a leak of any size.

Well done. Almost 100% wrong.
You can't have an air/air interface on mars. It has no air. The surface pressure is less than 1% of one atmosphere. So effectively you have an air/vacuum interface, which is an explosive situation.
If you live in a cave, you would have to have a perfectly sealed lining, or you would still have the risk of sudden catastrophic escape of your air. And you would have the risk of a roof fall causing an air escape. And why is a cave any advantage over water? It's not like a cave on earth, where you can just walk out of the entrance.

And you say water will agressively exploit any leak. Nope. If the inside air pressure is higher than the water pressure, it's the air that will escape. If the water is at higher pressure, the water will come in. There must be a balance point, where very little will happen. You would choose your depth that gives a pressure where the air would very slowly escape. This would be easy to detect and track down.
The space station had a leak, and it was very very difficult to track down, and it threatened the mission, and the safety of the astronauts.

[Gawdzilla Sama]

Jesus fucking Christ. I'll explain all this shit to you when I have time. First I have to make sure the paint dries evenly. Until then,

[mistermack]

A balloon submerged in water on Mars should be expected to behave very similarly to a balloon submerged in water on Earth due to one very important fact:

You didn't read what I wrote. I said a balloon WITH ONE BAR PRESSURE INSIDE IT. It would be totally different on Earth, compared to Mars.
On Earth, it would not inflate. On Mars, it would explode at the surface, and would need to be submerged to considerable depth, before it stopped exploding.
As humans would have to live in a bubble of air, at 1 bar pressure, the problem would be similar. Very strong burst-proof well-sealed walls, or a depth of water.

This is not correct. Internal pressure would be ~30% greater than external pressure and it would be necessary to reinforce the structure.

Of course not. In the case you describe, you would simply go deeper. You would simply choose the depth that was ideal. ie, best balance of pressure, so minimum reinforcement required.

One glaring deficiency in this plan is the scarcity of accessible water on Mars. We can obtain equivalent protection from radiation and solid particles by burying a structure under Martian dirt and rocks- which are substantially more accessible than water.

There is actually a huge amount of water on Mars. It's frozen. It has to be there, to have laid down the sedimentary rocks that have been observed. You would just have to melt it, and insulate it. Or add antifreeze. Or both. But there is plenty there.

[mistermack]

Jesus fucking Christ. I'll explain all this shit to you when I have time. First I have to make sure the paint dries evenly. Until then,

That should keep your mind well occupied. Don't overdo it.

[ScholasticSpastic]

There is actually a huge amount of water on Mars. It's frozen. It has to be there, to have laid down the sedimentary rocks that have been observed. You would just have to melt it, and insulate it. Or add antifreeze. Or both. But there is plenty there.

The water which laid down observed sedimentary formations does not have to be there. Consider, as you've pointed out, the fact that Mars has considerably less gravity and negligible atmospheric pressure. Now apply these facts to the case of water in light of all we know about the chemistry of water.

The reduced gravity on Mars reduces any requisite escape velocity for gas particles to be lost to space. The negligible atmospheric pressure means that evaporation of liquid water and sublimation of water ice becomes far more likely on Mars than it is on Earth- even at Mars's frigid temperatures. Once in its vapor phase, water WILL be lost to space- just as Earth loses water to space. The key reason Earth has atmosphere (and lots of accessible water) and Mars essentially does not is that Earth is still tectonically active while Mars's volcanism is rather lackluster. In case you didn't know, to the best of what modern theory accounts for, atmospheres like ours come from volcanoes, followed by modification by biotic or abiotic surface factors.

This combination of factors: Reduced ability to retain free water and reduced ability to regenerate free water once it's lost; means that accessible water can reasonably be expected to be a scarce commodity on Mars.

I'm not saying it isn't possible to liberate enough water to submerge a human habitat. I'm saying that it's a rather stupid waste of our energy to try to do so. This same reduced atmospheric pressure you're claiming makes a submerged habitat a good idea will result in rapid and ongoing loss of the liberated water to the atmosphere and space via the processes of evaporation and sublimation. Thus we would not only have to apply massive amounts of energy to the initial liberation of water, we would face this energy cost as an ongoing drain on our Martian resources as we constantly had to replace lost water.