A colossal asteroid slammed into Jupiter's largest moon Ganymede with so much power it dramatically and permanently reoriented the moon roughly 4 billion years ago, new research suggests. Scientists say the pivotal impact also significantly influenced the geological and internal evolution of the moon, which is larger than Mercury.
Computer simulations by planetary scientist Naoyuki Hirata of Japan's Kobe University predict the asteroid must have been about 186 miles (300 kilometers) wide, or 20 times bigger than the fateful one that wiped out the dinosaurs from the face of our planet about 66 million years ago.
