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Digging 8km under the lowest point on Mars will get us Mount Everest conditions for air pressure.

I was thinking of two ways of doing said title: enter image description here

  1. Nuclear powered bulldozers working around the clock to clear away dirt on a low point on Mars such as https://en.wikipedia.org/wiki/Hellas_Planitia or a place with similar elevation preferably near the poles where there is lots of ice to feed the colony with rocket fuel, water and oxygen and even more CO2 gas. The lower gravity of Mars should allow us to build bigger dozers that has more mass and can accommodate a submarine style reactor.

  2. Drop a hydrogen bomb down an 8km shaft to create a cavity and then clear away the sides to make it accessible as a gradual slope like a crater. Maybe a second bomb to do the clearing of the sides or nuclear powered dozers in option one above.

Would this be a practical means of starting a colony? We have experience with underground nuclear testing and we know that it can create cavities, maybe we don't even need to clear the sides and live in the cavity like a steep tear drop shape: https://en.wikipedia.org/wiki/Under...a/File:Nuclear_explosion_craters_schema_1.png https://en.wikipedia.org/wiki/Underground_nuclear_weapons_testing#:~:text=The extreme heat and pressure,cracked, and irreversibly strained rock.

There's a whole science in making a nuclear crater, why can't we use it on Mars to get air pressure?

Then we can not worry about decompression when we build. We can just carry scuba tanks with Oxygen and Nitrogen and breathe through a regulator.

If we use H bomb instead of pure Fission Bomb there should be less radioactivity problems.

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  • $\begingroup$ I don't think 8 km will be enough to get Mount Everest air pressure, see this related question: space.stackexchange.com/questions/32503/… It will be more like +30 km ! $\endgroup$
    – Cornelis
    Commented Dec 14, 2022 at 15:43
  • $\begingroup$ The third way: Redirect asteroids to hit the same crater over and over, until you have the depth you want. It will be a gigantic hole, as the sides will over time collapse to their angle of repose, so to maintain the depth needed, the hole will be very large around. But theoretically possible. Best to do this before you try to colonize the planet, as these huge collisions would be be globe-spanning events. For added points, you could choose asteroids that add to the volatile budget of the planet and help warm it and add atmosphere. $\endgroup$
    – Dan Hanson
    Commented Dec 14, 2022 at 21:41
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    $\begingroup$ 8km from the lowest areas of Mars will indeed be enough because those are are already -7km. Another 8km down the negative number line will take you to -15km, that will get you 30,500 Pa. I love the idea of redirecting asteroids. It's tough to decide which would be easier to do today, nuke it or smash it. If we choose sites close to poles we can melt ice to use liquid water as drilling lubricant and also supply the bottom of the new crater within the crater with water for a new lake that will not evaoporate away. $\endgroup$
    – David Ong
    Commented Dec 15, 2022 at 7:39
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    $\begingroup$ I think if you want to create a "natural" pocket of pressurized atmosphere on Mars, a simpler approach would be finding an already deep lava-tube, sealing the ends, and then pumping in exterior atmosphere. Depending on how the subsurface temperatures are, it might be possible to create a "shirtsleeves" environment this way, although people would need to be using O2 masks when "outside". $\endgroup$
    – Dragongeek
    Commented Dec 15, 2022 at 16:18
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    $\begingroup$ What about noctis Labyrinthus or Valles Marineras? you could dig your settlements into the bottom, in the shade, and store things that need cooling in the sides. Are you looking for passive pressure out of necessity or simplicity? Think about it this way: If you dig into the sides of Valles Marinaris you have a lot of rock above you that can help sustain pressurization. Mars isn't a great target for this because of it's low atmo pressure, whereas Titan already has 1.4something atmos and the moons of the gas giants have pressure-rich oceans. Weird comment I know! Great question though! $\endgroup$
    – AnarchoEngineer
    Commented Dec 16, 2022 at 6:54

3 Answers 3

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Bulldozers are only useful in moving loose rock. At depths approaching 8 km the rock will be intact and will require prior blasting. This would require a fleet of drilling rigs and explosive rigs to drill and blast the area of interest prior to removal of the rock.

Secondly, bulldozers may not be the most efficient way to remove the rock. Mechanical shovels and trucks would most likely be a better option, or even a system of mechanical shovels and conveyor belts.

Digging a hole 8 km deep is going to produce a lot of muck that needs to be deposited somewhere. The stability of the resulting rock dumps will also need to be considered.

Using thermonuclear explosives would work, but most likely more than one will be required and creation of the hole would most likely require more than one pass and more than one shaft.

Establishing the shaft for the nuclear explosive would also present its own problems.

From a technical perspective, all these options are possible but the main problem will be getting the heavy ground moving equipment on Mars. Sending stuff from Earth and assembling it on Mars will be costly. Similarly establishing mines, metallurgical plants and fabrication works for all manner of equipment on Mars will be likewise be costly, time consuming and require a prior colony working on Mars' surface.

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  • $\begingroup$ Can it be like the Kola Borehole? The gravity is weaker on Mars will that make drilling easier? en.wikipedia.org/wiki/Kola_Superdeep_Borehole $\endgroup$
    – David Ong
    Commented Dec 14, 2022 at 14:11
  • $\begingroup$ The only advantage that Mars' lower gravity will have in drilling holes in the ground will be that if air is used to flush the drill cutting from the hole either lower air pressure can be used, or for the same air pressure it will be easier to flush the hole. Many people mention the Kola super deep hole as an example what could be done. I have a few issues with this. In general, yes a hole drilled in a similar manner as the Kola super deep hole would be possible, if the right type of rig & drill steels were on Mars. Any such hole would be curved. Drilling a dead straight vertical hole ... $\endgroup$
    – Fred
    Commented Dec 14, 2022 at 18:25
  • $\begingroup$ ... for 8 km is going to be exceedingly difficult to do. Allowances will have to be made for that. Any nuclear bomb used will be of a certain size. The drilled hole will have to be slightly larger than the maximum cross sectional dimension of the bomb. The Kolar super deep hole was only 23 cm in diameter. A hole for a nuclear charge will need to have a larger diameter. Also, in drilling long length holes in the ground, they usually start out with a large diameter & the hole diameter decreases with depth. This is due to two things: wear on the drilling bit, the weight of the drilling steel ... $\endgroup$
    – Fred
    Commented Dec 14, 2022 at 18:31
  • $\begingroup$ ... as it gets longer with depth & the limited torque capacity of the drilling rig. A drill steel 8 km in length is a lot of steel, with a significant mass which needs to be rotated & pressure applied at the drilling end of the steel. $\endgroup$
    – Fred
    Commented Dec 14, 2022 at 18:35
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    $\begingroup$ Note drilling mud is not just "mud" a range of chemical additives are needed. No doubt such a hole could eventually be bored at great cost, but a habitat at 8km deep would provide precious few benefits and have enormous costs and disadvantages. So yes you can dig for pressure on Mars, but it would be carbon dioxide pressure not air pressure. And the idea of digging so deep would be completely impractical and provide no real benefit.. $\endgroup$
    – Slarty
    Commented Dec 15, 2022 at 21:41
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We've been down variants of this before:

How deep a valley or trench would be needed on Mars to provide the same atmospheric pressure as 6 km above sea level on Earth?

Eventually you reach the point the rock flows back into your hole--you'll reach this before you can have an Earth-normal atmosphere. You could get Everest type pressures, but if you want to live in that you'll need a high oxygen environment. Ask the Apollo 1 crew how good an idea that is.

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  • $\begingroup$ incorrect edit, rolled back $\endgroup$
    – uhoh
    Commented Dec 15, 2022 at 23:12
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I don't think that the superdeep borehole drill would be a practical proposition. The big problem with drilling at depth is friction which increases with depth and I suspect friction would not be dependant on gravity, vast amounts of drilling "mud" would also be required, and whilst doable it would be a royal pain on Mars as additives/lubricants are required. At 8km depth the rock pressure would probably be sufficient to cause the bomb blast cavity ceiling to collapse.

It would be far far easier to build a colony in tunnels at say 500m down. The overburden would easily be sufficient to restrain atmospheric pressure and radiation would be eliminated. The advantage of drilling 8000m or more down is somewhat limited as some form or airlock would still be required.

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  • $\begingroup$ WHY ON MARS WOULD YOU NEED AN AIRLOCK? When you reach 8km you reach Everest conditions, you don't need an airlock, the weight of the air above would guarantee the pressure. $\endgroup$
    – David Ong
    Commented Dec 15, 2022 at 7:20
  • $\begingroup$ We could use the liquid water from the poles to supply the fluid necessary to make the mud, that's why I suggested sites close to the poles. Also we could use a fission reactor to power the drill. $\endgroup$
    – David Ong
    Commented Dec 15, 2022 at 7:32
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    $\begingroup$ You need an airlock to prevent the 95% carbon dioxide in the Martian atmosphere getting into your habitat. If you just pump a bunch of oxygen into the hole, it will escape because it's less dense. $\endgroup$
    – Cadence
    Commented Dec 15, 2022 at 19:33
  • $\begingroup$ Cadence has the right answer to why an airlock would be required. Because even when you reach Everest conditions of pressure there is no weight of "air" above you, there is an equivalent weight of carbon dioxide instead. And if you open the habitat door the carbon dioxide will flood in and oxygen/nitrogen will flood out by diffusion and gas circulation killing everybody. You could try the same experiment with any gases. A house sized container of chlorine at atmospheric pressure connected directly to your back door would also be deadly without an airlock. $\endgroup$
    – Slarty
    Commented Dec 15, 2022 at 21:29
  • $\begingroup$ @DavidOng you would need an airlock because Martian soil is toxic as well as micro-particulate. breathing it would kill you. You also don't want it on your skin or in your habitat. Same problem on the moon. the sand you're used to on earth is massive per particle compared to martian or lunar soil and thus could enter pores and degrade lungs too quickly to even begin to deal with it for an extended period. you could trap this with water into a sludge I guess but I don't see that being particularly effective or economical $\endgroup$
    – AnarchoEngineer
    Commented Dec 16, 2022 at 7:00

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