Imagining Elon Musk's Million-Person Mars Colony The greatest thought experiment of all time Chapter 22 by Marshall Brain

[Quick Overview - This book introduces a new economic system that aims to eliminate all of the poverty, inequality, hunger, slums and so on found on Earth today. This new system is introduced as a thought experiment within the context of the million-person Mars colony recently announced by Elon Musk. This new system will radically improve the quality of life for the vast majority of humans living on planet Earth today.]

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[Feedback and suggestions on any part of this book are greatly appreciated. Contact information is here.]

Chapter 22 How much land will the Mars colony need?



Let's imagine that we really are going to build a one-million-person colony on Mars, just like Elon Musk has proposed. As described in Chapter 13 and Chapter 20, this colony will need to be independent and self-contained. Even if planet Earth were to be destroyed, the Mars colony needs to be able to survive on its own. Given this context, in this chapter the question we will explore is this: How much land does this colony need on Mars? And the corollary question then follows: If we are going to build a complete-duplicate experimental city on Earth to make sure that such a city is possible on Mars, how big will the experimental city on Earth need to be?

First we should ask: How many people will live in the Mars colony? Elon Musk has indicated that one million people is the number, but is this number correct? The colony on Mars will need to be able to produce/manufacture all of the goods we take for granted on Earth today: microprocessors and other chips, laptops, tablets, smart phones, consoles, TVs, appliances, vehicles (and everything associated with vehicles like body panels, tires, windshields, seats, wiring harnesses, motors, batteries, electronics, etc.), farm equipment, pharmaceuticals, medical devices, medical imaging, etc. And then all of the super mundane stuff like toilet paper, aluminum foil, plastic wrap, tape, diapers, etc.

Is one million people enough people to pull all of this off? After reading Chapter 13, it may not be. Duplicating all of the technology on Earth is a big undertaking. Maybe the Mars colony actually needs two million people in order to have all of the knowledge, experience and hands needed to replicate modern civilization. Keep in mind that we need enough people (engineers, scientists, researchers, technicians, machinists, machine operators, factory workers, etc.), along with the necessary redundancy of knowledge, along with the educational load of training up all of their replacements... This is going to be a very large group of people if we plan to duplicate all of the manufacturing capabilities on Earth.

But for the sake of this chapter, let's assume that one million people is the right number. And let's assume that we are going to run at a steady-state population of one million (see Chapter 19 for details on population maintenance or growth). So we ask: How much land will a million-person Mars colony take, whether we build it on Mars, or build its prototype on Earth to prove things out?

Let's take it step by step...

Housing

We discussed housing in Chapter 7 and then again in Chapter 20. The amount of space needed for housing really depends on how we choose to house people. In suburbia on Earth, we might give everyone a quarter-acre of land for a house that nominally holds 4 people. This is 16 people per acre, and then less once we account for roads. In Chapter 20 we hypothesized that everyone could live in tiny houses at a rate of 30 or 50 people per acre. At 25 people per acre, we are talking about 40,000 acres, or 62 square miles.

On the other hand, in Chapter 7 we saw that, by building large, tall buildings, we could fit everyone onto much tinier amounts of land. Four, or two, or even one square miles could be sufficient to house the whole population, depending on how much square footage each person is given for housing.

So there is a range. At its most spread out, maybe 100 square miles are necessary for housing one million people on Mars. This option also maximizes the infrastructure costs for things like water, sewer, electricity, Internet, transportation, and so on. This is a very expensive way to house people. On the other end of the spectrum, at its most compact, the Mars colony takes one square mile to house one million people, and perhaps everyone gets cabin fever. We really will not know until we run the experiments on Earth. Let's pick somewhere in the middle for now, and assume we will house everyone in 50 square miles.

Recreation

How much space should we dedicate to parks and similar places of recreation? Presumably people on Mars would like to take a walk, take a hike, play some softball, etc.

Central Park in New York City is one model to follow. Central Park is interesting because it has several different regions. In the southern part of the park, things tend to be manicured. In the northern part, things are more foresty and wild. Central Park receives about 40 million visitors a year and consumes 1.4 square miles of land.

If we assume that we 10X Central Park, so everyone can visit a park every day, we would have far more park space than the average American, but it only consumes 14 square miles.

Retail

Think about where you are living right now. Chances are that your housing in intermixed in a residential area that includes a lot of other stuff: retail stores, restaurants, gas stations, etc., along with all of their parking lots. Crossroads Plaza is typical:

This stuff can take up a lot of space. If the housing is taking up 50 square miles, it is easy to imagine another 10 square miles for retail and restaurants. But it really depends. What if the Mars colony has no need for retail space because everything comes via Internet shopping? And presumably Mars will handle all transportation publicly, as described in Chapter 14, which eliminates all parking lots.

Farming

Chapter 4 and 5 hypothesized normal dirt farming for staples like wheat and potatoes, and then advanced greenhouses for vegetables. On Mars, the assumption is that the controlled environment allows three growing seasons per year, so we would need less land than on Earth, where there is usually only one growing season per year.

If we stick with this plan, and assume that there is a wide variety of foods available for everyone, then perhaps we need a quarter of an acre per colonist. This means 250,000 acres, or 390 square miles, of farmland.

One thing that could change this estimate is meat. Meat animals consume a great deal of food to produce meat, and the number varies by the animal:

The efficiency with which various animals convert grain into protein varies widely. With cattle in feedlots, it takes roughly 7 kilograms of grain to produce a 1-kilogram gain in live weight. For pork, the figure is close to 4 kilograms of grain per kilogram of weight gain, for poultry it is just over 2, and for herbivorous species of farmed fish (such as carp, tilapia, and catfish), it is less than 2. [ref]

The point is that if Mars colonists want to eat meat, they need to grow more grain to do it. Or they need to give animals space to graze, which requires even more land. In the case of beef, the conversion rate is quite inefficient. Assuming we stick with chickens, then the need for land in the farming sector might head toward 500 square miles.

Electricty

Chances are that the Mars colony will get its power from solar panels. Nuclear power is the other option, but who knows what people will think about that.

If we assume solar, we can calculate the energy needs of the colony and determine the amount of land, just like we did in Chapter 17. It goes something like this:

Assume the colony needs 20 kilowatt-hours of electricity per person per day. This takes into account all usage – both home and industrial.

Solar radiation on Mars is weaker than on Earth, so assume 590 watts/square meter [ref]

Assume solar panels with 20% efficiency [ref]

Assume 4 hours of sunlight per day.

Assume that there is some spacing between panels for maintenance. So a square meter of solar panel actually consumes 2 square meters of land.

[If we were to create a similar facility on Earth, it would need about 20 square miles because sunlight is stronger on Earth.]

Industrial

The Mars colony is going to have a lot of factories because of everything the colony needs to manufacture. And factories can tend to be large. For example, here is Hyundai plant in Alabama:

The factory itself is about 40 acres under roof. Between the factory, the test track, the storage lot, and other parking lots, the whole facility consumes perhaps 1,000 acres, or almost 2 square miles.

Lest you think that is unusual, Lauma Fabrics makes fabric and lingerie. The factory by itself is almost 30 acres:

Given the number of products and factories we will have on Mars, let's assume about 100 square miles for factory space.

Forest

Will Mars colonists have any desire to buy wood products? To build wood houses? To make paper from wood? If so, then Mars needs forest land.

Just for the sake of the calculation, assume that Mars wanted to produce wooden houses. The number of trees to build a house:

Assume the house if 2,600 square feet.

Two stories, with 1,300 square feet per floor.

Ceiling height is 8 feet.

The entire structure is constructed of wood: frame, floors, roof, siding.

One 8-foot long 2x6 (used for studs) is assumed to be 8 board feet of lumber. One 8-foot long 2x12 (used for joists) is assumed to be 16 board feet of lumber. Siding, shingles and floor boards are assumed to be one inch thick wooden planks.

The house is 36 feet square. Taking rough estimates and rounding everything up:

432 studs (4,000 board feet) for all the walls interior and exterior

6,000 feet of 2x12 joists (12,000 board feet) (first floor, second floor, attic and pitched roof)

4,000 square feet of floor boards (attic has a floor)

4,000 square feet of boards for roof sheathing and shingles (accounts for roof pitch)

5,000 square feet of boards for wall sheathing and siding

A modern house would not be built this way. Sheathing and floors would be plywood or OSB. Even the floor joists might be OSB or laminated I-beams. Siding might be vinyl and the roof made of asphalt shingles. In this case, the amount of wood would be half of this estimate, or 15,000 board feet.

A mature pine tree (35 years old) is 15 inches in diameter and 72 feet long. It contains 500 board feet of lumber. If we let it grow 7 more years, it contains about twice that. So if we use trees that are 42 years old, we need 15 trees to build a house. Since we are assuming that houses are replaced every 15 years, and a stand of trees takes 45 years to grow (rounding 42 up to 45 years), we need 45 trees per stand to build a house (assuming no wood at all is recycled when a house is torn down) over the course of 45 years.

A stand might start with 500 trees per acre and get thinned down to 250 that are harvested at age 45. That means that each acre of trees yields approximately 5 houses worth of trees (250 / 45 ~= 5 houses per acre. There are 250,000 houses in the Mars colony, so we need 50,000 acres, or 78 square miles of trees, growing in the Mars colony to handle housing construction.

If we round this up to 100 square miles of forest, there would be two advantages: 1) There would be plenty of wood on Mars, and 2) people who don't like crowds would have a place to go when they need a break.

Adding it all up

If we add all of this up, here is the total land needed for a one million person Mars colony:

Housing: 50 square miles

Recreation: 15 square miles

Retail: 10 square miles

Agriculture: 500 square miles

Solar panels: 34 square miles

Industrial: 100 square miles

Forest: 100 square miles

Mines?

How big is 810 square miles? One way to think about it: It is a piece of land that is 28.5 miles x 28.5 miles. If you prefer round numbers, it is a square that is 30 x 30 miles. How big is that? If you look at the state of Rhode Island on a map, it is a little bigger, at 1,212 square miles:

In other words, if Rhode Island were shaped like a square, Rhode Island would be 35 miles x 35 miles. Imagine putting nearly the entire state of Rhode Island under a dome, or burying the whole state underground. This is the scale we are talking about when we think about a one-million-person colony on Mars.

If we want to minimize the land consumed, we could go with much more compact housing, saving 45 square miles. We could eliminate meat, saving 110 square miles or so. We could eliminate the forest and save 100 square miles. Maybe compress a few other things. Now the colony can fit in 500 square miles.

One million people fitting in 500 square miles means 2,000 people per square mile. One million people fitting in 1,000 square miles is 1,000 people per square mile.

There are not any places on Earth where a nation is completely independent in terms of food production, energy production, industrial production, etc. But if we want to compare the density of the Mars colony with different places on Earth, a page like this is helpful. Several island nations on Earth like Puerto Rico, Bermuda and Taiwan have population densities similar to the Mars colony.



Puerto Rico has 3.4 million people living on 3,515 square miles , or roughly 1,000 people per square mile.

If we were to create an experimental city on Earth to run a complete simulation of the Mars colony, then we need a little less land for solar panels. On Mars, the sun's energy delivers about 590 watts per square meter. On Earth it is about 1,000 watts per square meter because Earth is closer to the sun than Mars.

This analysis certainly prompts some thought. For example, putting 500 or 1,000 square miles of land under a dome and then keeping the air inside the dome at the correct temperature, humidity, pressure and O2 + CO2 concentrations is a huge challenge. Just the production of 1,000 square miles of glass or plastic would be a big deal. Then the framing members to hold 1,000 square miles of glass/plastic panels. Then the sealing system to prevent air leaks. Then the air handlers and conditioners... It gives you some sense of the magnitude of this Mars project that Elon Musk is proposing.

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[Feedback and suggestions on any part of this book are greatly appreciated. Contact information is here.]



You may also enjoy this in-depth interview, "Marshall Brain on Singularity 1on1: We're approaching humanity’s make or break period":

On the coming Singularity and Artificial Intelligence:

A Conversation with Marshall Brain from MIRI on Vimeo.