Carl Edward Sagan

Carl Edward Sagan , 1934-96, American astronomer and popularizer of science, b. New York City. Early in his career he investigated radio emissions from Venus and concluded that the cause was a surface temperature of c.900°F (500°C) and crushing atmospheric pressure. He also studied color variations on Mars' surface, concluding that they were not seasonal changes as most believed but shifts in surface dust caused by windstorms. Both conclusions were substantially confirmed years later by space probes. Sagan is best known, however, for his research on the possibilities of extraterrestrial life (see exobiology ), including experimental demonstration of the production of amino acids from basic chemicals by radiation. A professor of astronomy and space sciences at Cornell Univ. after 1968, he was involved with numerous NASA planetary space probes and was the creator and host of the 1980 public television science series Cosmos. His publications include The Dragons of Eden (1977; Pulitzer); a novel, Contact (1985); with Richard Turco, A Path Where No Man Thought (1990), on nuclear winter ; with Ann Druyan, Shadows of Forgotten Ancestors (1992); Pale Blue Dot (1994); and The Demon-Haunted World (1995).

Bibliography: See biographies by K. Davidson (1999) and W. Poundstone (1999).

Sagan, CarlEdward (1934–96)Americanastronomer. In the early 1960s he showed that a greenhouse effect should be operating on Venus, and calculated its surface temperature to be 500–800 K. He repeated H. C.Urey and S. L. Miller's experiment of irradiating a gas mixture resembling the Earth's primordial atmosphere, and found among the products many organic chemicals that are essential to life.