ScienceScience fiction has speculated about humanity’s inevitable expansion into the Solar System for over a century. Until recently, this had been a far-off dream, but today reality is swiftly catching up with the dream. We are not only poised to return to the MoonMoon in the 2020s, but also to send humans to MarsMars during the following decade. Meanwhile, private space ventures are planning to conduct mining operations on asteroids, and build hotels in space and bases on the MoonMoon. Our species is finally ready to expand beyond the safety of Earth, but we will fail if our aspirations are limited to overcoming only engineering and human health challenges.