> The energy source itself presents issues. If you need a $50 billion fusion reactor that takes 20 years to build and a thousand people to maintain then that's

> The energy source itself presents issues. If you need a $50 billion fusion reactor that takes 20 years to build and a thousand people to maintain then that's a problem to bootstrap on Mars. ITER is a research facility, not a practical reactor. We have new (relatively) high temperature superconductors that are much better than what was state of the art when ITER was originally designed, meaning we ought to be able to build much smaller and cheaper reactors going forward once the basic technology is worked out. The MIT ARC and SPARC reactors are an example. > If you're living underground anyway, why are you living on Mars instead of the Moon? Mars has air that be used to manufacture rocket fuel. It has closer to Earth-standard gravity. The temperature swings are less dramatic. Water is more abundant. It's closer to the asteroid belt, which means it functions as the local gas station and resupply depot for asteroid mining. It has close to an Earth-normal day/night cycle. Basically, it's a much more hospitable environment for humans than the moon. The main thing the moon has going for it is that it's far quicker and easier to get there from Earth.