The word ''terraforming'' conjures up many exotic images and p- hapsevenwildemotions, butatitscoreitencapsulatestheideathat worldscanbechangedbydirecthumanaction.Theultimateaimof terraforming is to alter a hostile planetary environment into one that is Earth-like, and eventually upon the surface of the new and vibrant world that you or I could walk freely about and explore. It is not entirely clear that this high goal of terraforming can ever be achieved,...