Deudney is a more extreme can-wejust-not-ist, but there are other voices suggesting a high level of prudence. For instance, Dr. Linda Billings, a consultant specializing in astrobiology and planetary defense, wants “collective peaceful existence on Spaceship Earth” before we seriously contemplate space expansion. Drs. Carl Sagan and Steven J. Ostro published a paper in 1994 titled “Dangers of Asteroid Deflection,” noting that a humanity advanced enough to save itself from asteroid impact is a humanity advanced enough to deflect an asteroid into itself. We would add to all this the concerns we’ve expressed about creating an immoral society, especially in the context of human reproduction and economics. Deudney himself points out that in a world of easy access to doomsday weapons, it takes only one society gone autocratically evil to create a nightmare scenario. If some aspects of space-settlement actively increase the likelihood of this outcome, the point becomes even more worrisome. Space geeks often cite a quote by science fiction author Larry Niven: “The dinosaurs became extinct because they didn’t have a space program. And if we become extinct because we don’t have a space program, it’ll serve us right!” But as Deudney notes, giant asteroids are rare. Humans haven’t been around that long, while the dinosaurs had a good long run. “Given these possibilities, perhaps the reason the dinosaurs lasted for nearly two hundred million years is because they did not have a space program.”

— City on Mars di Kelly Weinersmith, Zach Weinersmith (Page 377)