New simulations show that Jupiter's massive moon Ganymede was knocked off its axis when it was struck by a roughly 90-mile-wide asteroid around 4 billion years ago. The colossal collision was likely one of the biggest asteroid impacts the solar system has ever seen.

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,