The news these days is full of excitement about Evon Musk’s goal of setting up a colony on Mars. Everybody thinks it’s a great idea. Everybody is wrong.
An extremely hostile environment
People don’t seem to recognize just how hostile the Martian environment is. Let’s compare a Martian colony with the closest comparable station on earth: the permanent station at the South Pole.
The average temperature on Mars is about -70ºF; the average temperature at the South Pole is -55ºF. Mars is colder than the South Pole.
There is no breathable air on Mars. The colonists must be provided with a steady supply of oxygen. It would not be practical to extract the microscopic amounts of oxygen from the Martian atmosphere. It is possible to convert the carbon dioxide exhaled by the colonists (and resident in the Martian atmosphere) to oxygen, but the energy requirements of this process are enormous.
The USA maintains a scientific station at the South Pole. It houses about 150 people during the summer, and about 50 during the winter. I was unable to find any data on their logistic requirements, but I did learn that the base is supplied by C-130s, which carry about 20 tons of cargo and make a number of supply runs each year during the summer. Let’s assume that the South Pole station requires about 100 tons of material per year. A station on Mars would not have so many people, so let’s say that it would require only ten tons of supplies per year.
First, there is of course the difficulty of getting stuff to Mars — not just people but all the truck they need to survive. We’re talking hundreds of tons of stuff just for the pioneers. No single vessel can possibly carry all the stuff they’ll need. They’ll need some sort of housing, and that housing can’t be flimsy — it must be strong enough to withstand the occasional dust storms. Fortunately, the Martian atmosphere is thin enough that wind won’t have the punch that terrestrial wind packs. That scene in “The Martian” in which the astronaut is literally blown away by the wind is scientifically absurd. Nevertheless, they’ll need housing with strong solid walls.
Next, they’ll need a big energy source, something that can provide them with heat and light for years. Yes, they could use solar photocells, but let’s not forget that the sunlight on Mars is less than half the strength of sunlight on Earth. They would need acres and acres of photocells to sustain the colony. And once again, those solar cells would have be to able to withstand the windstorms. Add hundreds more tons of weight to the budget.
There might be subsurface ice on Mars that could be melted to make water, but they can’t plan on that. They’ll have to recycle every drop of water. The recycling process will be energy-intensive. Add more solar cells, and more weight. And of course they’ll need to bring along a substantial supply of water just to start. More weight.
Food? Sure, they could grow their own, but the energy cost of doing so would be humongous. Remember, any growing plants would need to be kept warm and well-lit. On the plus side, growing plants absorb carbon dioxide and release oxygen, so they would reduce the need for an oxygen recycling plant. Still, a Martian garden will require a LOT of energy. Some quick research found that greenhouses in New York require about 150 KW-hr per square foot for both heating and light. We’d probably need several thousand square feet of greenhouse area to grow enough food to sustain our colonists — which means that we’ll need something like 500 MW-hr of energy per year, or a steady supply of about 60 KW. The best solar cells generate about 20W/ft^2, which means that we’ll need at least 6,000 square feet of photocells just to generate enough energy to feed the greenhouse. But wait! That assumes that the sun shines all the time from directly overhead. The best we can attain in practice will require about 20,000 square feet of solar cells. That’s a square about 140 feet on a side. And then, of course, there are the batteries — and more weight!
The Mars Rover missions carrying the rovers Spirit and Opportunity used Delta II Heavy launch vehicles, which were able to deliver about one ton of payload to Mars. Mr. Musk’s plans include a rocket perhaps ten times more powerful. If the colony required a thousand tons of cargo just to get started, Mr. Musk would need a hundred launches for startup, followed by ten more launches every year. That’s just to sustain a colony with perhaps a dozen colonists. As the size of the colony grew, it would require more and more resupply missions each year.
Mr. Musk’s stated goal is to provide an alternative abode should we screw up the earth. In order to be self-sustaining, a Martian colony would need to be able to manufacture everything it needs. This would require a vast industrial plant and at least a billion people to do all the work. Every task they undertake would be much more difficult than the same task on earth. People working outside would be wearing bulky space suits and would be at great risk of death should accidents occur. They could not use anything with an internal combustion engine. No bulldozers. No trucks. No aircraft of any kind. Every activity outside the structures would have to be carefully planned and executed. Even simple tasks undertaken inside the structures would have to be planned to take into account oxygen consumption, pollution effects, space requirements, and just about everything else.
Here’s one way of assessing the difficulties. Suppose that we could transport EVERYTHING on earth — all the people, all the buildings, all the equipment, all the factories, everything that we now use to sustain our civilization. Suppose that we plunk all of this stuff down on Mars. All that stuff would need humongous amounts of additional stuff to be usable: oxygen supplies, heating, housing, and so forth. It would operate less efficiently than it now does on earth. Which means that we couldn’t sustain ourselves even with everything we now have.
A Martian colony will never work.