If you think Earth is dying and you want to save humanity, you either have to transfer a huge population to Mars—possibly on the order of hundreds of millions—in a short period, or you have to have unimaginably developed robotic technology. Although it’s hard to predict the future, it seems to us that if we’re so good at robotics and ecology that we can build a permanent bubble world for 1 million people on a distant oceanless planet, well, surely we can clean some carbon dioxide out of the air on Earth.
