Galilean Moons Of Jupiter. One dark, clear January night in 1610, Galileo Galilei climbed to the roof of his house in Padua. He looked up at the sky that was speckled with the flickering fires of a multitude of starry objects, and then aimed his small, primitive "spyglass"--which was really one of the first telescopes--up at that star-blasted sky above his home. Over the course of several such starlit, clear winter nights, Galileo discovered the four large Galilean moons that circle around the largest planet in our Sun's family, the enormous, gaseous world, Jupiter. This intriguing quartet of moons--Io, Europa, Ganymede, and Callisto--were named for four of the numerous mythic lovers of the King of the Roman gods.
Titan is certainly an exotic, fascinating, frigid oddball, that bears an eerie resemblance to the primordial Earth before life emerged and evolved on our planet (prebiotic). In fact, Titan is the only moon in our entire Solar System with a substantial atmosphere. It is also the only known world--other than Earth--where stable bodies of surface liquid exist.
"Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search for habitable worlds beyond Earth," commented Dr. Linda Spilker in the April 13, 2017 NASA Press Release. Dr. Spilker is Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.