Asteroid Bigger than the Dino-Killer Knocked the Solar System’s Largest Moon Sideways

The asteroid collision that killed the dinosaurs 65 million years ago may have been a major cosmic crack-up, but it was nothing compared to a bigger impact that occurred roughly four billion years earlier, between an incoming rock and Jupiter’s moon Ganymede. That’s the conclusion of a new study in Scientific Reports, suggesting that the distant world was knocked completely sideways by the long-ago bombardment.

Ganymede is one of the most complex of Jupiter’s nearly 100 moons—and indeed...