Larger than the planet Mercury and tidally locked to Jupiter, Ganymede is covered in concentric grooves on its far side. Scientists have long believed that these grooves were caused by a massive impact. Now, new research from Kobe University has confirmed this hypothesis and revealed the scale of the event.
The study found that an asteroid, roughly 20 times larger than the one that wiped out the dinosaurs, struck Ganymede 4 billion years ago. This colossal impact created a crater hundreds of kilometers wide and tilted the moon’s axis. The researchers used computer simulations to determine the size of the impactor and the extent of the damage it caused.