Billions of years ago, something slammed into the dark side of the moon and carved out a very, very large hole. Stretching 1,550 miles (2,500 kilometers) wide and 8 miles (13 km) deep, the South Pole-Aitken basin... For decades, researchers have suspected that the gargantuan basin was created by a head-on collision with a very large, very fast meteor. Such an impact would have ripped the moon's crust apart and scattered chunks of lunar mantle across the crater's surface, providing a rare glimpse at what the moon is really made of. ... Now, however... After analyzing the minerals in six...