Astronomer Carl Sagan’s curiosity about NASA’s Galileo spacecraft trajectory led to a paper that changed how scientists approached the search for life on other planets. The Galileo probe, which was first launched in 1989 and became the first to orbit Jupiter, was originally meant to be sent on a faster path using a liquid-fueled rocket. However, due to the Challenger disaster, Galileo was released more gently and slingshotted around Venus and Earth for gravitational boosts. Sagan convinced NASA to point Galileo’s instruments at Earth, resulting in the discovery of oxygen and methane in Earth’s atmosphere, as well as signs of vegetation and engineered radio transmissions. This approach later influenced the search for life on other planets, as scientists now use Earth as a template. The search for extraterrestrial life has gained significance with the discovery of exoplanets, and the upcoming James Webb Space Telescope holds the potential for revolutionary findings. However, scientists must exercise caution and gather extraordinary evidence when interpreting biosignatures on other planets, as there are non-biological explanations for certain gases like methane and oxygen. The process of building evidence and reaching a true discovery of life beyond Earth can take years or even decades, and assumptions about extraterrestrial
https://www.nature.com/articles/d41586-023-03230-z