Could we colonise another planet to save this one?

27 10 2015

© Auston Habershaw

Let’s do a little thought experiment, shall we? The late, great Douglas Adams wrote about a planet (Golgafrincham) that decided to ship all its undesirables (it was not made clear to them that they were in fact considered ‘undesirable’) to another planet to cut their population by a third. As it turns out, it wasn’t such a great idea.

This idea — shipping people to another planet — is a common theme in the sci-fi genre when there is an impending disaster, such as the planet becoming unsustainable, too many humans over-consuming, or because some great natural calamity is about to occur. Many think Mars is the most likely possible place to get the first sustainable human colony going, but it’s going to be a logistical nightmare to put together even a small colony.

Could moving to a planet like Mars stem the inexorable increase in the human population and save planet Earth? Not likely, and here’s why.

Let’s throw caution to the wind and make some outlandish assumptions just to make this point even stronger.

Suppose that Mars is entirely habitable in the same way as Earth, and that it has the same land:ocean ratio (29:71). Mars’ surface area is about 144,798,500 km2, or 0.284 of Earth’s. Even though many argue that we’re already way, way over the Earth’s human carrying capacity, let’s also assume that Mars could sustain the same density of humans as the Earth has today, or 0.284 × 7.3 billion = 2,073,200,000 people.

Now suppose that the ten largest airlines (those that fly the most passenger miles) could fly to this type of Mars at the same rate they carry people around Earth. If they did nothing else, they could carry about 5,000 people to Mars annually. If they could fly 100 times faster (spaceship speed is about 100,000 km/hr), they could transport some half a million people a year. So our wonderful, compatible, fantasy Mars would reach its ~ 2 billion carrying capacity in well over 4000 years (assuming replacement-level colonisation and/or intrinsic growth and no increase in the Earth-Mars transport rate).

But if you take the median projections of the human population to 2050 (9.2 billion), we average a net 53 million more people on Earth every year. Compared to our maximum fantasy transport rate to our fantasy Mars of 500,000/year, this represents less than 1% of the increase in the number of people on Earth per year today.

In other words, even if we could go to a (non-existent) habitable planet at (fantastical) rates of travel, we wouldn’t even dent the rate of human population increase on Earth.

Time to think of another solution.

CJA Bradshaw



4 responses

27 10 2015

You have taken an interesting angle on the inter-planetary emigration but think you are missing the point in moving to Mars. Moving to Mars shouldn’t be seen as an alleviation of our footprint on Earth, instead, more of a safe-guard to the life that we decide to translocate/introduce. In this case it’s more of an eggs in multiple baskets situation as we know of so many existential threats both terrestrially and extra-terrestrially.


28 10 2015
Tim O'Connell

Concur on both points – I’ve yet to see anyone else pursue this interesting approach, and I like it. That said, people working on getting to Mars are not interested in saving Earth, they’re interested in saving Homo sapiens from what we’ve done to Earth.


27 10 2015
Garry Jolley-Rogers

I don’t know. The realist in me agrees whole heartedly and thinks your scenario is rather optimistic. Certainly those enthusiasts who think we can settle Mars are unrealistic. Yet, pessimism is so poisonous so dreaming is helpful.

While Malthus must rule as does entrophy eventually but not without a fight.


27 10 2015
Mike Gale

Well done. A little maths can go a long way.

A bigger question, should we allow ourselves to go off planet, based on what we’ve done to this one?


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