Brian O'Leary (1940-2011) was an American astronomer and author, born in Boston and died in Vilcabamba, Ecuador. Holding a PhD in astronomy from the University of California, Berkeley (1967) with a thesis on the surface of Mars, he was selected in August 1967 for NASA's sixth astronaut group (the second intake of scientist-astronauts) with a view to a possible crewed mission to Mars. He resigned as early as 1968 for lack of any prospect of a flight, and drew on the experience for The Making of an Ex-Astronaut (1970). He went on to teach astronomy and planetary science at Cornell, Berkeley, Hampshire College and Princeton, and served on the science teams of the Mariner probes. In the last decades of his life he devoted himself to heterodox research on consciousness and "new energy".