Free Astronomy Magazine September-October 2018

39 I n science fiction novels and movies, the problem of overpopulation of the Earth is raised from time to time, and the solution typically proposed is the transfer of the pop- ulation surplus to space bases and colonies built in Earth orbit or on other planetary bodies. In reality, solutions of this type would be technologically possible, but they certainly would not solve the problem. In- deed, only an irrelevant fraction of the Earth’s population could be transferred: thousands of people if we want to be realistic; millions of people if we want to be visionaries. Unfortunately, there is already a clear population surplus in some regions compared to the dis- tributions of available resources: starvation, mass migrations and wars are witness to this. The UN predicts that in 2050, the human population will number almost 10 billion, 33% more than today. In 2100, the forecasts indicate an optimistic 11-12 billion. If these predicted values turn out to be correct, there will be about 4 bil- lion more people than today, and it is unlikely that, in the absence of sufficient resources on Earth, those people can be transferred elsewhere. For almost fifty years, actual humans have not traveled more than 500 km from the surface of our planet, and every few years we delude ourselves with the notion that someone may soon succeed in setting foot on Mars. How can we seri- ously think that in the coming decades we will solve the problem of overpopu- lation by transferring, who knows how and who knows where, a non-negligible part of humankind?For large numbers of settlers, circumscribed extraterrestrial envi- ronments are not enough − we will need an entire planet, and we do not know of another immediately habitable one nearby. SEPTEMBER-OCTOBER 2018 PLANETOLOGY I n the background, an artist’s image of an early Mars, when the planet was very similar to Earth. [Created for the MAVEN mission by the Lunar and Planetary Institute]