Beginning more than a hundred years ago, science fiction writers, early filmmakers, and, later, serious scientists explored the possibilities of human beings expanding beyond Earth to dwell in the Solar System.
Whether on the Moon, on Mars, in hollowed-out asteroids, or in constructed space stations, the dream of our species breaking free from this wet rock on which we evolved has been a source of fascination.
We're getting closer now to having the technological capability to make the attempt. Some would argue, in fact, that we could have had thriving colonies on the Moon for decades now, had the US and the USSR not cut back on their space programs in the 1970s.
But the Moon is one thing, and Mars is another. The Moon, obviously, is much closer and easier to reach. The problem is that it has no atmosphere, very little water ice (probably), and not much to offer in the way of quality of life.
Mars, by contrast, does have a thin atmosphere, apparently quite a bit of water ice, and possibly organic soil. It even has seasons. There's potential there to make another planet into something Earth-like, a place where humans can feel somewhat at home.
On the other hand, the big problem with Mars is that it is so far away. Even during its closest approach to Earth (opposition), which occurs about every two years, reaching Mars in a spacecraft takes at least six months. Such a voyage could be quite perilous for astronauts, being exposed to solar radiation, cosmic rays, meteors, and more. If something goes wrong, help is very, very far away.
So, maybe the answer is not to send astronauts first. Instead, send an army of machines specially designed to withstand the rigors that might disable humans. Indeed, some scientists propose sending hordes of insect-like robots to do the job:
“Small robots that are able to work together could explore the planet. We now know there is water and dust so all they would need is some sort of glue to start building structures, such as homes for human scientists,” says Marc Szymanski, a robotics researcher at the University of Karlsruhe in Germany.
Szymanski is part of a team of European researchers developing tiny autonomous robots that can co-operate to perform different tasks, much like termites, ants or bees forage collaboratively for food, build nests and work together for the greater good of the colony.
Of course, for those of us keeping up with the rapid pace of research in advanced nanotechnology, the idea of building all those robots on Earth and then sending them all the way to Mars doesn't make much sense.
Why not just send a nanofactory to Mars and program it to make whatever machines are needed? Those machines could be small and cooperative -- ant-like -- or they could be larger -- tractor-like -- or some of each. And because the nanofactory would be general-purpose, it could be re-programmed from Earth to make whatever new designs might be desired, including more advanced generations of nanofactories.
It is possible that some unmanned construction missions to Mars might be attempted before nanofactories have been fully developed. In that case, perhaps a future version of RepRap might be of use, but we think that true detailed exploration of our Solar System and building of comfortable off-Earth communities for human beings will await the achievement of molecular manufacturing.