h a l f b a k e r yWhat's a nice idea like yours doing in a place like this?
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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.
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]
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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. |
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Moderately-sized fusion devices would be the quickest and most economic method; nothing fancy, maybe a megaton or so. |
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//nothing fancy, maybe a
megaton or so// |
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An excellent idea, as evidenced by Chernobyl the radiation
should have little effect on the plants we want to grow. |
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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. |
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Plus the radiation may not have fallen enough by the time
we want to move in. |
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But the nuclear option may be unnecessary of course. |
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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. |
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+ 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. |
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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. |
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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). |
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But there might be some interesting insights derived from
the observation. |
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Beside, I just like jiggering with stuff to see what happens
:) |
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But don't people who live under ground get blisters on their
faces? Every sci-fi film I've seen shows that. |
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Plus they wear hooded robes and don't smile. |
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S'not underground though is it, just a very big hole, open to
the sky. |
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So smiling & wearing of traditional flimsy Martian garb
a'la E.R.B. is probably allowed, if inadvisable. |
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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. |
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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. |
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So you don't need a spacesuit, just an oxygen mask. |
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You probably 'could' walk around in your birthday suit if
you really wanted to (oxygen mask notwithstanding). |
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Accept you'll probably get frostbite & 'sunburn' (very thin
atmosphere & no protective magnetic field) all at the
same time. |
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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. |
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It might even be quite warm down there. |
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All good points, but then you don't get any light, the plants
won't like it. |
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Solar panels on the surface, lights at the bottom of the shaft. |
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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. |
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One snag: any O2 produced by the plants will tend to rise and
leak away. |
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The O2 was never the point, oxygen masks remember ;) |
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Yes, but if it weren't for the density thing, O2 would build up
in the pit as a bonus. |
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But you still wouldn't be able to breath it, because of the lack
of density thing. |
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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. |
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(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.) |
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Hang on. I thought you were proposing not digging the hole
as deep on the assumption O2 will hang
around with
less density ;p |
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//but if it weren't for the density thing, O2 would build up in
the pit as a bonus// |
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I think you forgot where we were in the conversation :) |
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OK, perhaps a little clarification is in order. |
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(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. |
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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. |
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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. |
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Yes, that will be the anoxia impinging on cognitive function. |
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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. |
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You are Jeremy Corbyn, and we claim our five Euro. |
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//an unpressurised (because it wouldn't need to be)
envelope// Alas, not quite. |
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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. |
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//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// |
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I knew there was a reason I didn't trust the big dome. |
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Those small 'home-domes' won't need pressurising beyond
what's needed to make them stiff & stand up. |
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//we claim our five Euro// |
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Congratulations! we've left it in the usual place, behind
the water pipes, third cubicle of
the Gent's at Mornington Crescent Underground. |
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Best hurry if you want to beat Sturton. |
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We left a cudgel behind the pipes in the fifth cubicle in
case you do. |
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// 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.// |
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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. |
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//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. |
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//Yeah I know// umm... <sigh> |
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Okay, it'd be more like 3/4 than 2/3, but the point is... |
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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. |
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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. |
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//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// |
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Asimov suggested asteroid harvesting many decades ago. |
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// a piece of kitchen plastic wrap // |
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... and your food will stay fresher for longer, too. |
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Doorstep deliveries of milk? |
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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. |
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But it will be quite useable for a long time; just re-hydrate it when needed. |
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//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.// |
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The pressure on both sides of the lid is going to be the same, since you've built it like that. |
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Damn. Now I don't know which answer is right. |
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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. |
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But then again water (or polystyrene foam) isn't
compressible. So maybe not. |
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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. |
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//need a fairly strong lid to stop it floating up and out.// |
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Saran Wrap, sealed in the vaunted Saran Wrap fashion. For better visualization, a thin glass plate. Or waxed cardboard. |
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Wind gusts notwithstanding. |
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I've never actually seen any actually vaunting of Saran Wrap. |
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Self-vaunted... "touted". |
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Ah, well, if you'd said "touted" we could have saved all this
confusion. |
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[throws some toys out of his pram] |
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We might not be able to get a thicker atmosphere
on Mars by digging holes after all. |
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The extant natural holes already
there may be about as deep as we can get [linky]. |
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//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? |
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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. |
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If it ever existed there of course. |
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// looking for stuff (like life) at the bottoms of those natural low points? // |
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On your planet, the lowest points are televised political debates, and there's obviously no intelligent life there - only primitive slime-moulds ... |
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