1. A Kobe University researcher has confirmed that an asteroid that struck Jupiter's moon Ganymede was about 20 times larger than the one that ended the age of the dinosaurs on Earth. 2. The impact caused Ganymede's axis to shift and left clear traces in the solar system. 3. The asteroid is estimated to have had a diameter of around 300 kilometers, creating a transient crater between 1,400 and 1,600 kilometers in diameter.