This isn't a happy story, but it's the science story we're most grateful for of all. In September, after 13 years in orbit around Saturn and its moons, the Cassini spacecraft bid us adieu and plunged to a fiery demise. It is impossible to even know the breadth of scientific knowledge this single space robot imparted to us, as scientists will continue poring over the mission's data for years to come. But we already know for certain that the spacecraft has radically altered our understanding of Saturn, the solar system, and the hunt for life on icy moons. RIP, buddy.