Living Underground on Mars – The 9 Drilling Challenges

Living underground on Mars may be the only survival option. However, this presents tunnel drilling challenges, which are often undiscussed.

But why do we even need to live underground on Mars?

  • Deadly Sun radiation
  • Blistering cold weather
  • Blinding dust storms

Tunnels, similar to subways on Earth, would become our Martian homes. In this analysis, I will discuss the tunneling challenges using my experience as an engineer, specifically for an edge case mission using a mega drill.

First, let’s set the stage by discussing the challenges Mars presents in more detail. Also, why Elon Musk and many others have set their sights on this red planet as a destination.

Why Mars is the best planet for colonization?

Look at the following list of reasons, which make Mars the least hostile place in our solar system:

  • Gravity: It has a moderate gravity (3.711 m/s2) like on Earth (9.807 m/s2). Mars has roughly 38% of Earth’s gravity, making it easier to launch a spacecraft from Mars than from Earth.
  • Water: It has liquid water under its surface.
  • Atmosphere: It lacks an Earth-like atmosphere, but it still has a thin one. On the flip side, it doesn’t have a crushing atmosphere like Venus.
  • Temperature: Temperatures aren’t extreme, even though the average temperature is -81°F.
  • Distance: the shortest distance from Earth to Mars is 33.9 million miles. Cosmic distance-wise, it’s not far.
  • Martian day: a Martian day is nearly the same as an Earth day. One Martian day is roughly 24 hours and 37 minutes.

The following is a closer one-on-one comparison between Mars and Earth:

Comparison metricsEarthMars
Diameter7,917.5 miles4,212.3 miles
Average distance from Sun93 million miles142 million miles
Mass (10^24 kg)5.970.639
Surface pressure101.3 kPa0.5 - 1 kPa
Year length 365.25 days687 days
Length of day23 hours 56 minutes24 hours 37 minutes
Temperature range-88°C to 58°C-140°C to 30°C
Temperature average13.9°C-62.7°C
Surface gravity2.66 times that of Mars0.375 that of Earth
Surface pressure1 bar0.006 to 0.007 bar
Max sunlight1370 W/(m^2)590 W/(m^2)
Radiation0.62 rads/year8 rads/year

Why living on Mars is a challenge?

Mars true color
The true color of Mars (Photo Credit: European Space Agency)

Mars’ thin atmosphere results in a surface pressure, which is less than 1% of that found on Earth.

One option to address this matter is to build an atmosphere. For example, by sublimating the frozen carbon dioxide on the planet. This would lead to the release of 12-14 millibars of CO2. Thus, tripling Mars’ atmosphere from 6 to around 20 millibars. Still a far stretch from Earth’s atmosphere of 1,013 millibars at sea level.

To matters worse, Mars’ thin atmosphere is 95% carbon dioxide. The below table breaks down the atmosphere content of Earth versus Mars.

Atmospheric CompositionEarthMars
Carbon Dioxide0.03%95%

Clearly, humans can’t breathe Martian air. We need a greater abundance of nitrogen and oxygen.

Mars’ magnetosphere

Mars doesn’t have a magnetosphere, the protective shield, which deflects harmful solar activity.

For example, charged particles from solar winds strike Earth almost daily. Without our magnetosphere, these particles would strip Earth’s ozone layer over time, leaving us exposed to dangerous UV radiation. Life, as we know it today, wouldn’t exist on Earth without our magnetosphere.

For the most part, Earth’s magnetosphere does a great job protecting us. Of course, as long as we’re not hit by a powerful Coronal Mass Ejection (CME).

On Mars though, we’ll find ourselves exposed to the following deadly elements:

  • Higher levels of radiation
  • Solar flare blasts
  • CMEs

Living underground on Mars – the drilling challenges

tunnel boring machine
Tunnel boring machine (Photo Credit:

According to Mars one, we’ll need 16 feet of Martian soil to cover the tunnels. This would provide the same protection found in Earth’s Atmosphere.

My view on tunnel drilling on Mars

Drilling using Tunel Boring Machines (TBM) is the primary approach to building tunnels on Earth. But, they come with a large number of often undiscussed problems.

Now, I’ve been a part of large engineering projects for drilling underground water tunnels. The tunnels ranged in diameter from 10 feet to 40 feet. While parts of these tunnels required traveling 150-plus feet below grade for the drilling.

I saw how quickly the drilling turned into an endless stream of problems. Even with constant overwatch over the machinery.

In other words, drilling is a huge headache on Earth. I can’t imagine what it’d be like 33.9 million miles away in a hostile environment.

To better explain, I’m going to go over the 9 drilling issues I expect to see on Mars.

#1 Drill repairs and replacement parts for a TBM

Drill-cutting bits need constant replacement. It’s like a regular drill you need to replace after too much usage.

Sometimes this means removing the entire drill from under the ground. This happens when other problems come up in the replacement process.

To top it off, it’s common for these mega drills to break down and get stuck.

Even worse, TBM crews need to go underground and rescue these drills when they get stuck. Now, who’s going to rescue a drill that’s far down underground in Martian soil?

We can’t send autonomous mega drills to Mars and expect them to work remotely.

Good luck trying to get a mega drill unstuck without hands-on human help.

#2 The electrical power demand of a TBM

TBMs need megawatts of power to operate.

The TBM projects I’m involved in have huge power requirements. The power requirements range from around 2 megawatts to 8 megawatts each.

For a less than 100-mile tunnel run, we designed many substations at various intervals. The substations have power transformers connected to the power grid at 115,000 volts.

These transformers have ratings between 30 to 40 MVA. Some are much larger as they feed 5,000 HP plus-sized pumps to remove underground water.

On Mars, I doubt we’ll find water where we’re drilling. So we wouldn’t need massive pumps with supporting infrastructure.

Regardless, where would power for the mega drills come from on Mars? The only option I see is to bring nuclear reactors from Earth.

#3 The speed of drilling with a TBM

Mega drills are slow. Very slow.

They drill around 15 miles per year give or take. It depends on the geological conditions underground.

Also, in how well the crew maintains the TBM and supporting equipment.

In bad conditions, TBMs don’t operate consistently. I’d say 50% of the time the drills aren’t in operation.

All in all, the reduced running time is due to the following factors:

  • Ground conditions with soil and rock
  • Removing muck
  • Fixing electrical problems
  • Inflow problems from underground water
  • Replacing and fixing drill parts due to wear and tear
  • Repairing the drill’s infrastructure
  • Waiting on orders over critical parts
  • Safety issues

One of the projects I’m involved in has a decade-plus-long timeline for less than a 100-mile tunnel run. On Mars, we don’t have this luxury of time.

We need to work fast to get below the Martian surface due to radiation exposure.

Staying on the Martian surface for weeks could cause irreversible problems. Plus, unprotected electronic devices could fail from too much radiation.

Even more, every day could bring new problems we never planned for. I can’t emphasize enough how important speed is.

To illustrate project timelines, let’s go over some of Robbins’ epic tunneling projects. They’re one of the industry leaders in tunneling.

ProjectLocationTunnel diameterTunnel lengthProject timeline
Túnel Emisor Poniente (TEP) IIMexico City, Mexico28.5 feet3.6 miles5 months
Grosvenor Decline Tunnel Queensland, Australia26 feet1.1 miles3 months
Pinglu TunnelShanxi Province, China15.7 feet15.8 miles4 years 2 month
The Niagara Tunnel ProjectQueenston, Ontario, Canada47.5 feet6.5 miles4 years 8 months
Boston Harbor ProjectBoston, Massachusetts, USA26.5 feet9.4 miles4 years 2 months
The Manapouri Hydroelectric ProjectLake Manapouri, New Zealand33 feet6 miles2 years 9 months

Several things to keep in mind:

  • Number of TBMs: some projects have many TBMs working together. This is not an option on Mars, even though it’s a huge time saver. It’s a huge challenge to get one mega drill to Mars, let alone two or more.
  • Prep time: these large projects need years of prep time. You don’t just say you want a tunnel and start drilling tomorrow. The Robbins’ project timelines only include drill times.
  • Challenges: you could easily triple the timeline for these Robbins’ projects. For example, if a drill hits something unexpected, work will slow to a snail’s pace.

#4 The physical size of a TBM

tunnel boring machines
Photo Credit: Brisbane City Council

These drills are not only huge but very heavy. Sure, we don’t need to drill a 50-foot-diameter tunnel on Mars.

But even still, let’s assume a 10-foot diameter tunnel. The drill will still be very heavy.

We don’t have any rockets that can get something this large safely to Mars. Including all the required infrastructure.

The large TBMs are over 1 million pounds in weight. And they’re 400 feet in length with all their trailing gear.

Then there’s the size of all the supporting infrastructure. A 30 MVA 115,000 to 12,000 volts transformer weighs around 75,000 pounds.

To put things into perspective, the NASA Mars Curiosity Rover weighed 1,982 pounds.

Important Note: it’s preferred to send preassembled equipment to Mars. This will make life easier for Martian workers. Plus, it’s much easier to troubleshoot assembly on Earth than on Mars. 

#5 Removing excavated soil from the drilled tunnel

We need to remove the cut ground from inside the tunnel. We bring the dirt and rock to the surface and transport it away.

On Earth, we take the grated soil away using large rail cars. Then we typically recycle it in some way.

On Mars, this part of the work would be an engineering challenge.

To illustrate, let’s look at the Purple Line Extension Transit Project in Los Angles. It’s two 21-foot diameter tunnels 9.1 miles long.

At the end of this project, the TBMs will cut 495,000 cubic yards of soil. That’s equal to 2.3 million bathtubs filled with dirt!

Important Note: The excavated ground is typically mixed with certain compounds. This makes the removal of the cut soil easier. 

So, the 495,000 cubic yards of cut soil, becomes 650,000 cubic yards of removed soil. This doesn’t make the work any easier on Mars though.

#6 Geological drilling challenges

On Earth, a contractor always has a plan of action to cover all possible issues. On Mars, this isn’t possible.

Mars is an unknown land to us.

Below are 4 geology conditions on Earth that can become huge problems on Mars.

1) Hard abrasive rocks

No matter how strong cutters are, they’ll wear over time. If we’re dealing with hard abrasive rocks, the cutters will damage even faster.

Who knows what type of rock we’ll find below Martian soil?

I doubt we’ll be lucky and only drill through soft soil. This means we’ll need to replace the cutters often.

2) Blocky rock, sand, and clay

These materials and shapes can cause a cutter to get stuck. To counter these types of materials, the drill crew does half strokes with half resets.

This allows the crew to pull back if there’s too much torque build-up. This slows the drilling work, but it beats trying to remove a giant drill from a stuck position.

3) Loose running ground made of a lot of clay

Drilling through this type of material can cause a collapse above the drill.

The ground above the tunnel can fall trapping the drill. Even more, a large cavity can form above the tunnel where the collapse happened.

This cavity can extend 40-plus feet high above the tunnel. Of course, the cavity height depends on how far you drill underground.

To remove the fallen material, engineers sometimes build bypass tunnels. This requires a human presence and a lot of engineering equipment.

4) Underground water

Almost all water on Mars exists as ice found near the poles. This is what we think.

One problem on Earth is the inflow of water in the tunneling area.

Water can flood a tunnel causing huge project delays. Plus, it can damage parts of a TBM.

So, before drilling, operators need to pump out the water in the work area.

As I mentioned already, for one of our large drilling projects, we designed a couple of 5,000-plus HP pumps. Not only are these pumps large, but their required infrastructure is extensive.

#7 Infrastructure required to support TBM operation

It’s not just the one drill we need to take to Mars. These other following parts we need to take too:

  • Electrical equipment like transformers and nuclear reactors
  • Extra parts for the TBM
  • Cranes to lift the heavy equipment
  • Hydraulic jacking systems
  • Laser-guided equipment for guiding the drill
  • Pre-cast concrete segments for the tunnel’s outer wall

My point is, drilling is a huge effort. You need a lot of equipment with many people working closely together.

Important Note: Mars has little to no atmosphere as we learned. So, this makes landing heavy objects on Mars even more difficult.

On Earth, our atmosphere reduces the falling speed of objects. On Mars, the atmosphere does nothing for you.

#8 Building a tunnel’s outer shell

As we bore through the ground, we need to install pre-cast concrete panels. These panels create a tunnel’s outer shell, providing structural support.

In some instances, the panels break or don’t properly get placed.

More important is the analysis before the drilling. We need to complete a field investigation with a geological analysis.

This will help with the design of the concrete segments. The concrete segments need to withstand the following tunneling loads:

  • Above-ground soil weight
  • Falling rocks
  • Water pressure
  • Earthquakes
  • Thrust forces from construction conditions
  • Inside tunnel traffic from usage

On Earth, this analysis can take years. On Mars, we don’t have this luxury of time. Even worse, Mars is a foreign land filled with unknowns.

We don’t want failed construction after wasting trillions of dollars and countless years.

What’s more, the process of creating precast concrete panels is time-consuming. The panels are heavy too.

#9 Human team support for a TBM

A TBM normally has a team of 10 to 15 people supporting the drilling at any given time.

Machines alone can’t do the drilling at this scale on Mars. We need humans on Mars to assist with the drilling.

The drilling will need constant hands-on problem-solving.

While keeping in mind, drilling is intense and difficult even on Earth. The difficulties include:

  • 24-hour drilling work schedule
  • Extreme loud noise
  • Mountains of dust
  • Low visibility
  • Fatigue
  • Dangers of working with heavy equipment underground

On Earth, we take many safety measures. Also, we have the best hospitals nearby.

But this luxury doesn’t exist on Mars. Any help from Earth would take at least 6 to 8 months to arrive.

In short, if you get hurt on Mars, you’re more than likely on your own.

Alternatives to digging manmade tunnels on Mars

We don’t have the tech to drill into Mars’ surface today using a TBM. We do, but it’s not practical in any way to make it happen.

But, we don’t need to abandon the idea of living underground on Mars. Other options exist, such as:

  • Sealing off natural caves.
  • Digging into lava tubes to use as shelter. Lava flows create these amazing empty tunnels.

Of course, we need to first find these caves and lava tubes.

But when we do, this approach will reduce the amount of digging we need to do. What’s more, if we pressurize the caves or tubes, we can create livable environments like on Earth.

Even more, we can heat up these underground areas. Obviously much easier said than done. But nothing will be easy when it comes to living underground on Mars.

The goal of living underground on Mars

The challenges of terraforming Mars are huge. I’m not talking about landing several humans on the red planet.

Rather, full-blown colonization.

It’s very difficult to wrap your head around this mission. Partly because our tech isn’t advanced enough to pull this off.

Frankly, taking a TBM to Mars is a horrible idea today. I’m sure in the future we’ll have the ability to colonize Mars without huge tunnels.

Ironically though, humans started living in caves. Then after thousands of years of evolution, we’re planning to go back to cave living.

What are your thoughts on living underground on Mars? What are the biggest challenges of terraforming Mars you foresee? Do you think we should drill our own tunnels in martian soil?

Featured Image Photo Credit: European Space Agency


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