NASA's Cassini spacecraft just crashed into Saturn - here are the 5 biggest discoveries from the historic mission

NASA's Cassini spacecraft plunged into Saturn's atmosphere on September 15, marking an end to its mission to study the ringed planet and its many, mysterious moons. The spacecraft spent 13 years orbiting Saturn and its moons. During that time, Cassini uncovered many mysteries about the neighborhood. Here are the five biggest mysteries form the mission.