MarkWhittington writes: Dr. Louis Friedman, one of the co-founders of the Planetary Society, is coming out with a new book, "Human Spaceflight: From Mars to the Stars," an excerpt of which was published in Scientific America. Friedman revives and revises a version of the humans vs. robots controversy that has roiled through aerospace circles for decades. Unlike previous advocates of restricting space travel to robots, such as Robert Park and the late James Van Allen, Friedman admits that humans are going to Mars to settle. But there, human space travel will end. Only robots will ever venture further.