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Making a little bit of Mars slightly more habitable

Dig a big hole.
  (+3, -1)
(+3, -1)
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Atmospheric pressure increases the deeper you go & the highest growing plants on Earth have been found at a height of 6 km.

Which got me thinking..

Apparently something like a depth of 40 km should give us roughly the same pressure on Mars as 6km above sea level on Earth so all we have to do is dig a big hole..

The Hellas Planitia is already 7 km deep so that gives us a bit of a head start.

Everyone bring a spade we'll have this done in no time.

Skewed, Dec 02 2018

World’s highest plants discovered growing 6km above sea level https://www.newscie...km-above-sea-level/
[Skewed, Dec 02 2018]

Asteroid_20Orbital_20Decay_20Harvesting [pertinax, Sep 16 2019]

On The Other Hand Forget_20Mars_2c_20Let_27s_20Do_20Titan
Forget Mars, Let's Do Titan [Skewed, Sep 20 2019]

What's the deepest we can dig on Mars? https://space.stack...on-mars/40154#40154
The Hellas Planitia (as is) may be about as deep as we can get. [Skewed, Nov 29 2019]

[link]






       There are plenty of bits of your own planet that could do with making a bit more habitable before you go to the trouble and expense of hauling a bucket-and-spade mob to Mars ... Slough and Basingstoke are obvious candidates.   

       Moderately-sized fusion devices would be the quickest and most economic method; nothing fancy, maybe a megaton or so.
8th of 7, Dec 02 2018
  

       Yes, there as well.
8th of 7, Dec 02 2018
  

       //nothing fancy, maybe a megaton or so//   

       An excellent idea, as evidenced by Chernobyl the radiation should have little effect on the plants we want to grow.   

       On the other hand the main reason for that may well be that many of their life cycles are so short, under the frigid conditions on Mars, as in the arctic, we can expect far slower growth leading to much longer life cycles.   

       Plus the radiation may not have fallen enough by the time we want to move in.   

       But the nuclear option may be unnecessary of course.   

       Small craft might be sent out to the asteroid belt to strap onto a suitable asteroid & nudge it into a trajectory to bring it down where we want on Mars, maybe accelerate it by slingshot around a suitable planet, at those velocities it should do the job without assistance from fussionables.
Skewed, Sep 15 2019
  

       + for anything about Mars, however seems a lot easier to just create little bubbles on the surface and pressurize them. And by little bubbles I mean big bubbles the size of cities. Or more likely just pressurized buildings.
doctorremulac3, Sep 15 2019
  

       True I suppose, but a really big hole might give us somewhere we can introduce a few extant plants & organisms & watch as they (hopefully) adapt, with luck a few will begin to colonise higher points along the crater wall.   

       I'm not sure that they'll be any help in thickening the atmosphere (gas exchange is after all just that, exchange, it doesn't add significantly to atmospheric density as far as I know).   

       But there might be some interesting insights derived from the observation.   

       Beside, I just like jiggering with stuff to see what happens :)
Skewed, Sep 15 2019
  

       But don't people who live under ground get blisters on their faces? Every sci-fi film I've seen shows that.   

       Plus they wear hooded robes and don't smile.
doctorremulac3, Sep 15 2019
  

       S'not underground though is it, just a very big hole, open to the sky.   

       So smiling & wearing of traditional flimsy Martian garb a'la E.R.B. is probably allowed, if inadvisable.
Skewed, Sep 15 2019
  

       OK, so that solves the creepy robe problem and blisters. Plus the whole dour mood thing. Martians would need to be upbeat to face the challenges and blisters, frowns and robes wouldn't cut it. Plus the whole asphyxiation thing from wearing a rob instead of a spacesuit.
doctorremulac3, Sep 15 2019
  

       Well part of the point of the big hole is that at the bottom the air pressure will be roughly equivalent to 6 km above sea level on earth.   

       So you don't need a spacesuit, just an oxygen mask.   

       You probably 'could' walk around in your birthday suit if you really wanted to (oxygen mask notwithstanding).   

       Accept you'll probably get frostbite & 'sunburn' (very thin atmosphere & no protective magnetic field) all at the same time.
Skewed, Sep 15 2019
  

       If the "hole" is more of a shaft, like a mine shaft, then there won't be much risk if sunburn, and the other effects of a thin atmosphere and no magnetic field will also be mitigated.   

       It might even be quite warm down there.
8th of 7, Sep 15 2019
  

       All good points, but then you don't get any light, the plants won't like it.
Skewed, Sep 15 2019
  

       Solar panels on the surface, lights at the bottom of the shaft.   

       On the other hand, there's not that much to see 40km undergound, so you'll want a pretty good elevator for trips to the surface.   

       One snag: any O2 produced by the plants will tend to rise and leak away.
MaxwellBuchanan, Sep 15 2019
  

       The O2 was never the point, oxygen masks remember ;)
Skewed, Sep 15 2019
  

       Yes, but if it weren't for the density thing, O2 would build up in the pit as a bonus.
MaxwellBuchanan, Sep 15 2019
  

       But you still wouldn't be able to breath it, because of the lack of density thing.
Skewed, Sep 15 2019
  

       Hang on. I thought you said ambient pressure was about equal to 6km earth altitude? That's less than the height of everest. Climbers _without_ supplemental oxygen can cope with that altitude. If you had a 100% O2 atmosphere at that pressure, even old farts like you and me would be OK.   

       (By definition, if oxygen masks worked, which they would, then a 100% O2 atmosphere would work just as well; masks don't increase overall pressure.)
MaxwellBuchanan, Sep 15 2019
  

       Hang on. I thought you were proposing not digging the hole as deep on the assumption O2 will hang around with less density ;p   

       //but if it weren't for the density thing, O2 would build up in the pit as a bonus//   

       I think you forgot where we were in the conversation :)
Skewed, Sep 15 2019
  

       OK, perhaps a little clarification is in order.   

       (1) A deep enough hole will give you pressure equivalent to 6000m altitude on Earth.
(2) At this pressure, humans can just about manage with 20% oxygen and would have no problems with 100% oxygen, whether supplied by a non-pressurized face mask, or as an atmosphere. Alas, Mars' atmosphere is mostly CO2
(3) Plants make oxygen.
(4) Sadly, oxygen is less dense than CO2, and therefore any O2 made by plants at the bottom of the hole will tend to rise out of the hole.
MaxwellBuchanan, Sep 15 2019
  

       Gotcha : an unpressurised (because it wouldn't need to be) envelope over the top of the pit? once you've filled it with O2 you'll probably notice the effects of a leak & go looking for it before you lost enough to be fatal, you can put the oxygen masks back on anyway if need be while you patch it & refill with O2.   

       But I think I'd rather stick to oxygen masks & small O2 filled envelopes around your homes on the floor of the hole than trust a structure that big.
Skewed, Sep 15 2019
  

       Yes, that will be the anoxia impinging on cognitive function.   

       So, you're at the bottom of a deep dark hole in the ground that you dug yourself, with no way out, and slowly suffocating.   

       You are Jeremy Corbyn, and we claim our five Euro.
8th of 7, Sep 15 2019
  

       //an unpressurised (because it wouldn't need to be) envelope// Alas, not quite.   

       The pit will be filled with a gas that is about 2/3rds as dense as the general atmosphere of Mars. Therefore, the envelope would need to withstand a considerable pressure. Consider, if you will, a helium balloon in the form of a vertical cylinder, carrying its maximum payload. The weight of the payload is essentially hanging from the circular top of the cylinder.
MaxwellBuchanan, Sep 15 2019
  

       //Alas, not quit//   

       //I'd rather stick to oxygen masks & small O2 filled envelopes around your homes on the floor of the hole than trust a structure that big//   

       I knew there was a reason I didn't trust the big dome.   

       Those small 'home-domes' won't need pressurising beyond what's needed to make them stiff & stand up.
Skewed, Sep 15 2019
  

       //we claim our five Euro//   

       Congratulations! we've left it in the usual place, behind the water pipes, third cubicle of the Gent's at Mornington Crescent Underground.   

       Best hurry if you want to beat Sturton.   

       We left a cudgel behind the pipes in the fifth cubicle in case you do.
Skewed, Sep 15 2019
  

       // The pit will be filled with a gas that is about 2/3rds as dense as the general atmosphere of Mars. Therefore, the envelope would need to withstand a considerable pressure.//   

       umm...
FlyingToaster, Sep 15 2019
  

       Yeah I know, the density is irrelevant because it's held down by the atmosphere above (that's why we dug it), the lift might not be though (Mars is super rich in CO2 & he was talking about a 100% O2 mix in the pit so I guessed he just misspoke) & I prefer the little domes on the floor of the pit anyway so I didn't see the point in getting into it.
Skewed, Sep 15 2019
  

       //Solar panels on the surface, lights at the bottom of the shaft.//
sp. "Heliostats on the rim reflecting light directly into the hole". No need to faff around with converting to electricity & back again.
neutrinos_shadow, Sep 15 2019
  

       //Yeah I know// umm... <sigh>   

       Okay, it'd be more like 3/4 than 2/3, but the point is...   

       <dramatic silence>   

       There is no lift. You could fill the pit full of hydrogen under an atmosphere of sulfur hexafluoride and - as long as you have the opening covered with a piece of kitchen plastic wrap or summat - there is no push upwards.
FlyingToaster, Sep 16 2019
  

       O2 is lighter than CO2, a 40 km column of gas lighter than CO2 in a 95% CO2 atmosphere, it's not exactly inconceivable there might be 'some' lift.
Skewed, Sep 16 2019
  

       //Small craft might be sent out to the asteroid belt to strap onto a suitable asteroid & nudge it into a trajectory to bring it down where we want on Mars//   

       Ahem; see link.
pertinax, Sep 16 2019
  

       Asimov suggested asteroid harvesting many decades ago.   

       // a piece of kitchen plastic wrap //   

       ... and your food will stay fresher for longer, too.
8th of 7, Sep 16 2019
  

       Doorstep deliveries of milk?
not_morrison_rm, Sep 16 2019
  

       Not as a liquid ... unless it's in a pressure vessel, any water left at the top of the hole (i.e. your "doorstep") will rapidly boil away, leaving you with dried milk.   

       But it will be quite useable for a long time; just re-hydrate it when needed.
8th of 7, Sep 16 2019
  

       //O2 is lighter than CO2, a 40 km column of gas lighter than CO2 in a 95% CO2 atmosphere, it's not exactly inconceivable there might be 'some' lift.//   

       The pressure on both sides of the lid is going to be the same, since you've built it like that.
FlyingToaster, Sep 21 2019
  

       Damn. Now I don't know which answer is right.   

       OK, imagine a tank full of water (Mars' atmosphere), and we make a well at the bottom of the tank and insert a cylinder of polystyrene foam. The foam wants to float up out of the hole, so it'll need a strong lid on the hole to hold it there.   

       But then again water (or polystyrene foam) isn't compressible. So maybe not.   

       But then again again, a balloon (not significantly overfilled - i.e. at whatever the local atmospheric pressure was) of oxygen would float in Mars' atmosphere; you'd need to expend work in order to drag it downward. So I'm sticking with my first answer, which is that a column of oxygen in a well will need a fairly strong lid to stop it floating up and out.
MaxwellBuchanan, Sep 21 2019
  

       //need a fairly strong lid to stop it floating up and out.//   

       Saran Wrap, sealed in the vaunted Saran Wrap fashion. For better visualization, a thin glass plate. Or waxed cardboard.   

       Wind gusts notwithstanding.
FlyingToaster, Sep 21 2019
  

       I've never actually seen any actually vaunting of Saran Wrap.
MaxwellBuchanan, Sep 21 2019
  

       Self-vaunted... "touted".
FlyingToaster, Sep 21 2019
  

       Ah, well, if you'd said "touted" we could have saved all this confusion.
MaxwellBuchanan, Sep 21 2019
  

       Bugger!   

       [throws some toys out of his pram]   

       We might not be able to get a thicker atmosphere on Mars by digging holes after all.   

       The extant natural holes already there may be about as deep as we can get [linky].
Skewed, Nov 29 2019
  

       //The extant natural holes already there may be about as deep as we can get // You say that as if it's a bad thing. But shirley that just means that we ought to be looking for stuff (like life) at the bottoms of those natural low points?
MaxwellBuchanan, Nov 30 2019
  

       The lowest of them only reach a little more than 7 km down & have atmosphere around one 29th as thick as at the top of Mount Everest, far below the Armstrong limit .. but yes, the deepest equatorial craters we can find is where we really should be looking for evidence of life, the warmest climate with the most recently thick enough for liquid water atmosphere, the spots it's most likely to have clung on longest.   

       If it ever existed there of course.
Skewed, Nov 30 2019
  

       // looking for stuff (like life) at the bottoms of those natural low points? //   

       On your planet, the lowest points are televised political debates, and there's obviously no intelligent life there - only primitive slime-moulds ...
8th of 7, Nov 30 2019
  
      
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