William McGuire Bryson OBE HonFRS is an Anglo-American author of books on travel, the English language, science, and other non-fiction topics. Born in the United States, he has been a resident of Britain for most of his adult life, returning to the United States between 1995 and 2003. He served as the chancellor of Durham University from 2005 to 2011.
Robert Zubrin is an American aerospace engineer and author, best known for his advocacy of the manned exploration of Mars. He and his colleague at Martin Marietta, David Baker, were the driving force behind Mars Direct, a proposal intended to produce significant reductions in the cost and complexity of such a mission. The key idea was to use the Martian atmosphere to produce oxygen, water, and rocket propellant for the surface stay and return journey. A modified version of the plan was subsequently adopted by NASA as their "design reference mission". He questions the delay and cost-to-benefit ratio of first establishing a base or outpost on an asteroid or another Project Apollo-like return to the Moon, as neither would be able to provide all of its own oxygen, water, or energy; these resources are producible on Mars, and he expects people would be there thereafter.