In 1994, Sagan wrote “Pale Blue Dot,” another science book about the solar system and man’s place in it.

Sagan also became a leading authority on the possibility of life existing on other planets. Sagan went on offer other theories that would be proven true: There might be liquid on the surface of Saturn’s moon Titan, that Jupiter’s moon, Europa, might have entire oceans on its surface and that the shifting coloration of the surface of Mars was caused not by vegetation but by shifting dust pushed around by enormous windstorms. Data from NASA’s first Venus probe, Mariner 2 in 1962, confirmed Sagan’s theory. He argued Venus, covered with heavy clouds, was warmed by a “greenhouse effect” and had a surface temperature of about 900° fahrenheit. Sagan began consulting with NASA in the early 1960s as an expert on planetary sciences.

The project would remain secret until it was revealed by a Sagan biographer in 1999. The Air Force would call off the project in 1959, convinced the public would not react well to such a show of force. The Air Force hoped the detonation would be visible from Earth – a visible demonstration of U.S. Sagan reiterates his position on extraterrestrial life - that the magnitude of the universe permits the existence of thousands of alien civilizations, but no credible evidence exists to demonstrate that such life has ever visited earth.NASA hoped such a detonation might lead to more understanding about the geology of the moon. The book covers a broad range of topics, comprising Sagan's reflections on anthropological, cosmological, biological, historical, and astronomical matters from antiquity to contemporary times. The book also discusses the underlying premises of science by providing biographical anecdotes about many prominent scientists throughout history, placing their contributions into the broader context of the development of modern science. Cosmos traces the origins of knowledge and the scientific method, mixing science and philosophy, and speculates to the future of science. In the book, Sagan explores 15 billion years of cosmic evolution and the development of science and civilization.

Cosmos has 13 heavily illustrated chapters, corresponding to the 13 episodes of the Cosmos television series.

Cosmos by Carl Sagan