IAU Symposium 269 celebrates the 400th anniversary of Galileo Galilei's discovery of the Medicean Moons, Jupiter's four largest satellites, exploring the impact his findings have had on science and the humanities. Galileo's instrumental discovery and his belief that the planets and moons in our Solar System could be habitable worlds encouraged a deeper understanding of our place in the Universe. Today, ongoing space missions to Jupiter's moons, our own Moon, Mars, Saturn, and Enceladus, reveal our continued fascination with the possibilities of alien life, but this time with a focus on...