Frosch discusses NASA's planetary exploration program, beginning with past and present reconnaissance efforts. the next step will be systematic, more comprehensive exploration, and finally intensive study. Summing up what's been learned so far via this program, the diversity of the planets is their most impressive single feature. Frosch talks about future plans, including Voyagers I and II, Galileo, humans in space, and an extraterrestrial machine that could use solar energy and local materials to build a replica of itself in space.