Born in 1934 in New York City, Carl Edward Sagan earned his bachelor's and doctoral degrees from the University of Chicago. He conducted research and lectured at the University of California in Berkeley and Harvard University. In 1970, he became the David Duncan Professor of Astronomy and Space Science at Cornell University in Ithaca, New York. He died in 1996 at age 62, having established himself as an insightful researcher, but in particular as arguably the greatest popularizer of astronomy of the twentieth century. For his signal achievements in bringing astronomy into the popular limelight, Sagan was honored with the American Astronomical Society's Annenberg Prize in 1992.

Throughout his career, Sagan's work centered on studying planetary atmospheres, especially the conditions on Earth that gave birth to early life forms. In this area, Sagan made his greatest contributions to science.

Sagan began his research, however, on the surface and atmosphere of Venus. In the...