Sagan was central to the discovery of the high surface temperatures of the planet Venus. In the early 1960s, no one knew for certain the basic conditions of Venus' surface and Sagan listed the possibilities in a report later depicted for popularization in a Time-Life book, Planets—his own view was that the planet was dry and very hot, as opposed to the balmy paradise others had imagined. He had investigated radio emissions from Venus and concluded that there was a surface temperature of 500 °C (900 °F). As a visiting scientist to NASA's Jet Propulsion Laboratory, he contributed to the first Mariner missions to Venus, working on the design and management of the project. Mariner 2 confirmed his views on the conditions of Venus in 1962.
Sagan was among the first to hypothesize that Saturn's moon Titan and Jupiter's moon Europa may possess oceans, a subsurface ocean, as in the case of Europa, or lakes, thus making the hypothesized water ocean on Europa potentially habitable for life. Europa's subsurface ocean was later indirectly confirmed by the spacecraft Galileo. Sagan also helped solve the mystery of the reddish haze seen on Titan, revealing that it is composed of complex organic molecules constantly raining down to the moon's surface.
He furthered insights regarding the atmospheres of Venus and Jupiter as well as seasonal changes on Mars. Sagan established that the atmosphere of Venus is extremely hot and dense with crushing pressures. He also perceived global warming as a growing, man-made danger and likened it to the natural development of Venus into a hot, life-hostile planet through greenhouse gases. Sagan and his Cornell colleague Edwin Ernest Salpeter speculated about life in Jupiter's clouds, given the planet's dense atmospheric composition rich in organic molecules. He studied the observed color variations on Mars’ surface, concluding that they were not seasonal or vegetation changes as most believed, but shifts in surface dust caused by windstorms.
Sagan is best known, however, for his research on the possibilities of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation.
He is also the 1994 recipient of the Public Welfare Medal, the highest award of the National Academy of Sciences for "distinguished contributions in the application of science to the public welfare."
Sagan was a proponent of the search for extraterrestrial life. He urged the scientific community to listen with radio telescopes for signals from intelligent extraterrestrial lifeforms. So persuasive was he that by 1982, he was able to get a petition advocating SETI published in the journal Science, signed by 70 scientists, including seven Nobel Prize winners. This was a tremendous turnaround in the respectability of this controversial field. Sagan also helped Dr. Frank Drake write the Arecibo message, a radio message beamed into space from the Arecibo radio telescope on November , 1974, aimed at informing extraterrestrials about Earth.
Sagan was chief technology officer of the professional planetary research journal, Icarus for twelve years. He co-founded the Planetary Society, the largest space-interest group in the world, with over 1,000,000 members in more than 149 countries, and was a member of the SETI Institute Board of Trustees. Sagan served as Chairman of the Division for Planetary Science of the American Astronomical Society, as President of the Planetology Section of the American Geophysical Union, and as Chairman of the Astronomy Section of the American Association for the Advancement of Science.
At the height of the Cold War, Sagan became involved in public awareness efforts for the effects of nuclear war when a mathematical climate model suggested that a substantial nuclear exchange could upset the delicate balance of life on Earth. He was the last of five authors — the "S" of the "TTAPS" report as the research paper came to be known. He eventually co-authored the scientific paper hypothesising a global nuclear winter following nuclear war. He also co-authored the book A Path Where No Man Thought: Nuclear Winter and the End of the Arms Race, a comprehensive examination of the phenomenon of nuclear winter.
Sagan predicted on ABC's Nightline in 1991 that smoky oil fires in Kuwait set by Saddam Hussein s army during the first Gulf War would cause an ecological disaster and send black clouds into the atmosphere resulting in global cooling. Retired atmospheric physicist and climate change skeptic Fred Singer dismissed Sagan's prediction as nonsense, predicting that the smoke would dissipate in a matter of days.
In his book The Demon-Haunted World, Sagan gave a list of errors he had made, including his predictions about the effects of the Kuwaiti oil fires, as an example of how science is tentative, a self-correcting process.
Pale Blue Dot: A Vision of the Human Future in Space
In a tour of our solar system, galaxy and beyond, Cornell astronomer Sagan meshes a history of astronomical discovery, a cogent brief for space exploration and an overview of life-from its origins in the oceans to humanity's first emergence to a projected future where humans "terraform" and settle other planets and asteroids, Earth having long been swallowed by the sun. Maintaining that such relocation is inevitable, the author further argues that planetary science is of practical utility, fostering an interdisciplinary approach to looming environmental catastrophes such as "nuclear winter" (lethal cooling of Earth after a nuclear war, a widely accepted prediction first calculated by Sagan in 1982). His exploration of our place in the universe is illustrated with photographs, relief maps and paintings, including high-resolution images made by Voyager 1 and 2, as well as photos taken by the Galileo spacecraft, the Hubble Space Telescope and satellites orbiting Earth, which show our planet as a pale blue dot. A worthy sequel to Sagan's Cosmos. Author tour.
Copyright 1994 Reed Business Information, Inc. --This text refers to an out of print or unavailable edition of this title.
Sagan's great appeal as a popular-science writer, beyond his prodigious knowledge, is his optimism and sense of wonder. A visualizer and a visionary, he fires our imagination and turns science into high drama. After writing about our origins in Shadows of Forgotten Ancestors (1992), Sagan turns his attention to outer space and takes up where Cosmos left off 14 years ago. An astonishing amount of information was amassed during that productive era, and Sagan, of course, is up on all of it. A passionate and eloquent advocate of space exploration, he believes that the urge to wander, and the need for a frontier, is intrinsic to our nature, and that this trait is linked to our survival as a species. Throughout this beautifully illustrated, revelatory, and compelling volume, Sagan returns again and again to our need for journeys and quests as well as our unending curiosity about our place in the universe. Such philosophical musings are interwoven with precise and enthusiastic accounts of the triumphs of interplanetary exploration, from the Apollo moon landings to the spectacular findings of robotic missions, especially the Voyager spacecraft. Sagan describes one exciting discovery after another regarding the four giants--Jupiter, Saturn, Uranus, and Neptune--and their many moons, mysterious and exquisite rings, and volatile atmospheres. He argues, convincingly, that planetary exploration is of immense value. It not only teaches us about our celestial neighbors, but helps us understand and protect Earth. Yes, we have seemingly insurmountable problems on this pale blue dot, but we have always reached for the stars, and we mustn't stop now.