Read the passage below carefully and then answer the question.
(from DiscoveryEd)
(Carl) Sagan was born in New York City and studied at the University of Chicago, where he received a Ph. D. (1960) in astronomy and astrophysics.
Sagan's research was directed toward evidence of life in outer space. He also studied the origins of organisms with the geneticists Hermann J. Muller and
Joshua Lederberg. Sagan had a large share in establishing exobiology, the search for extraterrestrial life, as a scientific discipline.
After serving as assistant professor of astronomy at Harvard University and astrophysicist at the Smithsonian Astrophysical Observatory (1962–68),
Sagan became director of the Laboratory for Planetary Studies at Comell University. He co-founded the Planetary Society (1980) and served as its
president. He worked on many space-exploration projects for the National Aeronautics and Space Administration (NASA) and through his frequent
television appearances became one of the nation's best-known science educators. Besides numerous scientific publications, Sagan wrote several popular
science books, including The Dragons of Eden: Speculations on the Evolution of Human Intelligence (1977), winner of the 1978 Pulitzer Prize for general
nonfiction; Broca's Brain: Reflections on the Romance of Science (1979); Cosmos (1980), written to accompany the television series of the same name,
which he co-produced and narrated; and Comet (1985), with his wife Ann Druyan (1949-). He also wrote a best-selling novel, Contact (1985). Repeatedly
honored by NASA, he also received the Public Welfare Medal of the National Academy of Sciences in 1994
What sentence below best describes the main idea of this passage?