Flat Mars Settlement

MarsDog · 2005-11-07 13:14:55

Atmospheric pressure on Mars is equivalent to around 32 KM up on Earth.

http://apollo.lsc.vsc.edu/classes/met13 … s_vert.gif

Gravitational acceleration
Earth 9.75 m/s^2
Mars 3.71 m/s^2

If Mars had same surface pressure then the altitude would be;
(9.75 m/s^2)/(3.71 m/s^2) * 32 = 84 KM

To flatten Mars to a depth of 100 KM it would produce a flat circle of D=1636 Km

depth = 100 km
diameterof Mars=6800 km
A^2=B^2+C^2

Solve for radius of flat area.

A=3400 B=3400-100 C=(3400^2-3300^2)^.5 = 818 km (diameter of flat area 1636 km)

Things would roll and flow towards the center.
There would be a lake surrounded by the atmosphere.

The flat area would have a noticeable equivalent slope of 1/8
(at the rim)

noosfractal · 2005-11-07 14:37:03

To flatten Mars to a depth of 100 KM it would produce a flat circle of D=1636 Km

Well, there are a couple of challenges with this one.

The first is that you would have to move 1.3 trillion cubic kilometers of rock. If you could move a million tons per second out of the area, it would take 250 billion years. Even if you could vaporize a trillion tons per second, it would still take 250 thousand years.

I think you would have to hit Mars with something like the Earth's moon to make the flat area - but that might knock Mars out of its current orbit. And if you could do that, you probably just want to add to Mars' mass to give it more gravity.

Maybe you could melt the surface with a giant laser, but I think you'd evaporate the atmosphere long before you got your 1600 km lake of molten rock.

Also, if you actually achieved the modification without disturbing the atmosphere, I don't think the atmospheric pressure distribution would be spherical anymore - so you still might not get 1 bar of pressure at the center of the flat area.

We might want to try something a little more modest
_

MarsDog · 2005-11-07 19:57:50

http://mathforum.org/dr.math/faq/formul … phere.html

$spherecap.gif$

V = (Pi/6)(3r1^2+h^2)h =105,629,350 cubic km
(r1=818km h=100km)

Or using alternate = 105,766,952 cubic km
(R=3400km h=100km)

If one cubic km moved per second: divide by 3600 sec/hour and 8765 hour/year
gives only 3.34 Earth years (1.78 Mars years)

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The lake and atmosphere would be spherical cap, since attracted to center of gravity.
Different radius, of course. (like 2 asteroids orbiting their center of gravity)

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Limiting is available energy to move the rock.
And the robots do do the work.

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I wonder if you could dig to the metallic core of Mars ?
On Earth you can only go so deep before the rock starts to flake off the walls.

Dook · 2005-11-07 21:53:31

What would the point be in doing this?

MarsDog · 2005-11-07 22:16:01

http://www.space.com/scienceastronomy/m … 30213.html
Mars Ice is Mostly Water: Good for Biologists, Bad for Terraformers

Scarce fluid resources would automatically collect at one central point:
Reducing exposure to solar wind and increasing escape velocity.
The super greenhouse gasses could rain out near the edges and flow back in.
The central lake would be a good thermal sink, the vacation destination for Martians ?

Become an ecosystem, the magnet of development for the greatest Martian city.
You could walk from rainforest paradise (mirror assisted) to the cold of today's Mars.

Building a 10 km high circular mountain range would further trap the moisture, and other gasses, provide space for mirrors and solar cells, perhaps hydroelectric power from the rivers flowing back.

idiom · 2005-11-08 02:20:11

Planets have a deep desire to be spherical. If you modify it by much the rock will flow back into a ball.

I don't know what scale that would occur at though...

MarsDog · 2005-11-08 05:12:33

I looked pit mine and retaining wall design concepts.
Depends on rock characteristics.

One guess, to start from is slope of pouring sand.
Get water on it and problems. Rock fall is around 1.5 to 1

In this case, effective slope is 1/8 at the edge decreasing to 0 at the center.
With lot of pressure ice flows as in a glacier. With rock, what are the parameters ?

How deep at what slope can you dig into rock ?

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If you can go 100 km on Mars it would be around 1 Atmosphere
On the Moon 6*32 = 192 km plus ?

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With limited gasses, deep would allow terraforming of a small part of the planet.
In addition provide protection for those dwelling inside the sloping walls from nearby gamma ray extinction blasts. A nearby stellar explosion would severely disturb Earth's atmosphere. The bottom dwellers on Mars might get lucky.

karov · 2005-11-08 12:32:36

Niven`s Canyon you are talking about.

MarsDog · 2005-11-08 15:15:17

I see lot of science fiction by Niven. Anyone know what his canyon approximations were ?

In ice, a crevase can only be so deep because the ice flows under pressere.
That is a steep vertical drop. However, over long distances the height can buid up.
At a height and maximum slope ice flows.

For rock pebbles (talus slope) the slope is around 1.5 to 1
On Mars, with less gravity how would the slope be affected ?
The talus slope slowly creeps. At what slope is the creep negligible ?

Keeping maximum slope, can the iron core of Mars be exposed ?

=================================================

Equatorial Mars ring of 100 km depression would be another interesting concept,
The scarce fluids, right where you need it.

SpaceNut · 2005-11-08 20:52:09

Do a stepped wall pit making each open area slightly small the deeper you go.

MarsDog · 2005-11-09 03:22:24

Do a stepped wall pit making each open area slightly small the deeper you go.

You are right, in that maximum depth before slope failure is not a flattened surface.
The experienced slope changes from 1/8 at the rim to 0 in the middle.

Keeping slope at 1/8 experienced constant, a curve dipping toward the middle results.
Would have to integrate to solve for depth reached.

Lot of links on slope failure, the compared slopes on Mercury, Moon and Mars are all different. Even on Earth not well understood. More complicated than I thought.

karov · 2005-11-09 03:40:05

The "slope failure" problem, resembels to me to the "tether failure" but reversed.

We tappering of the tethers - as opposed to the slope steepnes. Similar curves, but in the one case we have compression force, in the tethers -- tension.

In case of "slopes" depends on the compression strenght of the piled material.

Good leading point could be the limit of rounding of the astronomical bodies -- it is about 700 km dimaeter for rock.

MarsDog · 2005-11-13 16:20:00

More complicated than I thought.

Looks like the limitation is the Brittle-Ductile Transition Zone.
Under heat and pressure, the rock slowly flows.
On Earth up to 50 KM deep. On cooler, lower G Mars, may be lot thicker.
The 100 KM depth on Mars may be reachable.

If you tried a supersized strip mine on Mars, piling the rock on the other side.
Rock moved to the other side would be cold and stronger, a deeper Brittle-Ductile Transition. The excavated hole would be warmer, perhaps a good source of thermal energy.

I wonder the result.

karov · 2005-11-14 13:56:54

Deja view???

http://www.newmars.com/forums/viewtopic.php?t=369

I think again that it will come much cheaper to erect inflatable gasbag walls a-la-paul-birch, than to excavate millions of km3 of rock!

chat · 2005-11-14 15:54:44

MarsDog,

1 mid sized impact on mars will move it all at once.
The slope should be similar to Arizona crater.

MarsDog · 2005-11-14 19:20:59

Brittle-Ductile Transition Zone limits the depth of an excavation.
At a certain pressure and temperature rock slowly flows.
That is why you can only drill so deep.

The slope evens out to equal erosion between different layers.

You cannot impact Mars and get a deep hole,
because the high temperature will cause the rock to flow.

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Crevase in a glacier is only so deep because ice flows beyond a certain pressure.
Rock is similar, but at greater depths.

Have not figured out to apply creep of rocks to Mars
http://www.google.com/search?client=ope … 8&oe=utf-8

chat · 2005-11-14 19:28:43

MarsDog,

On Earth yes.
On Mars ?

Look around the solar system for deep impacts on cold objects and the way they respond.

Mars after all is a cold body now.

MarsDog · 2005-11-14 21:16:24

How cold Mars is not known:
http://sci.esa.int/science-e/www/object … ctid=31028

Core size, temperature and composition also not known.

Even on the Moon craters get filled in by lava flow and rock rebound.

Looks like will have to wait for seismic rovers for better guesses.

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Bacteria found 12 km underground
http://www.science-frontiers.com/sf090/sf090g08.htm

But how good does it taste ?

chat · 2005-11-15 07:04:11

MarsDog,

Just didn't want you to give up on your idea to quick .
A small amount of teraforming goes a long way on mars in a canyon, so the idea has lots of merit to it.
The scale is probably a bit big, but the general idea of the thicker atmosphere in lower elevations is a good one.

A mid sized impact on mars would probably leave a hole 3 times as deep as on earth, best guess for a colder object.
The impact material ejected would probably change mars more than the hole it leaves behind.
I agree we know so little about Mars that its all guesswork.

MarsDog · 2005-11-15 14:05:24

If you had a very slow impact. An asteroid, made of lead,
in the shape of a thick pie plate, to keep the Martian crust from filling back in.
Floating on top, there would be a great depression caused by the difference of densities.

Or another idea, using giant hydraulic jacks to seperate the Grand Canyon. Utill the hot plastic rock below is exposed. High temperature alloys and extreme cooling would determine the depth. And the cooler would provide geothermal energy. Efficiency 1-T2/T1

http://oak.cats.ohiou.edu/~piccard/phys … arnot.html

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