Taking off your helmet and breathing on Mars is the ultimate science fiction fantasy, but terraforming has become a rigorously modeled engineering problem. This episode traces the idea from Jack Williamson's 1942 story Collision Orbit through Carl Sagan's 1961 Venus paper, Richard Cathcart's campaign to get the word into the Oxford English Dictionary, Robert Haynes's concept of ecopoiesis, and NASA's 1976 Planetary Ecosynthesis study.

We lay out the recipe for life, including liquid water, thermodynamic disequilibrium, and the CHONPS elements, then examine why Mars lost its atmosphere after its core cooled and how Andy Tomaswick proposes to restore it by slamming thermonuclear-propelled Kuiper Belt comets into the poles. We explain why Sagan's algae plan for Venus would have created a planet-sized oxygen bomb, why hauling hydrogen from Uran ...