Summer 1994: Astronomers watched in awe as Comet Shoemaker–Levy 9 was torn apart by Jupiter’s gravity. What began as a single nucleus became a “string of pearls” — 21 fragments on a collision course. For days, one after another, they slammed into Jupiter with the force of thousands of nuclear bombs. It was the first time humanity witnessed a cosmic impact unfold in real time… a stark reminder of what could happen closer to home. | The Randall Carlson