Carl Sagan was an American astronomer, astrophysicist, and science communicator, known for his work in popularizing science. He played a significant role in the NASA missions to Mars and was instrumental in the search for extraterrestrial life. Sagan authored several books, including the famous "Cosmos," which was also adapted into a popular television series. Sagan was a strong advocate for scientific skepticism and critical thinking. He founded the Planetary Society, an organization dedicated to promoting space exploration. His ability to explain complex scientific concepts in an accessible manner has inspired generations to appreciate the wonders of the universe and the importance of scientific inquiry.