In the modern world, most things are driven by economics. If something can make money, especially if its a lot of money, someone will make it happen.

And so it is with space exploration and colonization. The commercial opportunities are the most often quoted reason why humanity’s expansion into space is inevitable.

Think of all that space, that real estate, available on the Moon, the asteroids and on Mars. And all those resources buried under the surface.

The most often quoted precedent for mass colonisation of “new lands” is the settling of North America. America had vast empty spaces, huge supplies of coal, metal, timber and wild animals to support the countries development, and few local natives to hinder their expansion. The settlement of the country by the Europeans and its development over the next few centuries lead to the emergence of the greatest single industrial power in history.

So who’s to say it can’t happen again on, say, Mars?

Well, there are differences. In the Americas the new colonists could fairly soon live off the land, with food and lumber readily available. Mars will be dependent on Earth for generations for food in the short term, but in also the long term for complex tool and medicines, and minerals and metals that aren’t readily available on Mars.

America was able to export tobacco and grain back to Europe from fairly early on, giving a financial return to those who had paid for the transporting of the colonists. Mars will have nothing to offer that couldn’t be more cheaply and easily produced on Earth. The cost of sending metals mined on another planet home, for example, would be staggering (the one possible exception to this might be mining Helium 3 on the Moon. This is a isotope of Helium that would be essential to Fusion power plants, if we can ever get this amazing new form of power production working. There’s very little Helium 3 to be found on the Earth, but much more of it is on the surface of the Moon).

Some people argue that the divergence of cultures between Mars and Earth will throw up new and saleable cultural, artistic and technical innovations. This is a long shot. There is no precedent for this on Earth. Even for America the rate of technical innovation was due to the growing huge industrial base, not because of its geographical distance from Europe.

Colonizing Mars, or the Moon, will not be driven by profit from mining or industry.

Mining the asteroids is another oft quoted source of potential massive profits from space expansion. Companies like Planetary Resources and Deep Space Industries suggest there are trillions of dollars worth of rare metals in asteroids circling the sun in near Earth orbits, and certainly the prospects are exciting. But the technological challenges  and cost of mining asteroids and bringing the results back to Earth shouldn’t be underestimated.

But even if mining off planet were profitable, would it require a permanent space colony with thousands of colonists? All of this activity must surely be possible using just a few hardy engineers commanding an army of semi-autonomous robotic miners.

It’s been suggested that in the future mass industry will be developed in Earth orbit, to take advantage of the space available, the zero gravity environment, and imported metals mined from the asteroid belt.

This I just can’t see. If more room is needed for industry, there’s plenty on earth that’s more hospitable; even factories floating on the surface or under the sea would be easier to build and to service.

The only likely advantages of industry in zero gravity would be for producing specialist crystals and possible 3D printing human organs. We wouldn’t need massive orbital factories for these, and in any case, the bigger the space station the more they would generate more vibrations in their structures and defeat their own purposes.

Space tourism has some limited scope for feeding the expansion of the human kind. People will want to visit hotels in Earth orbit and travel to the moon once these things are possible, and even visit other places if the travel time were to be brought down from months to weeks. I could see the growth of a limited market here. But would the growth of America really have taken off if people just traveled across the Atlantic Ocean for three months, stayed for a fortnight, and had to come straight back again? Probably not.

So I’m sad to say, I don’t see the business case stacking up for any of these scenarios. If colonisation of the solar system is to happen, the profit motive will not be the main driver for it.