Earlier this summer, researchers in Greenland documented possibly the oldest and largest meteorite crater ever found on Earth. The crater, estimated to be 3 billion years old, currently measures about 62 miles (100 km) across. But the researchers believe its width before erosion was likely more than 310 miles (500 km) — much bigger than the largest visible crater, the 2-billion-year-old Vredefort crater in South Africa, which measures 186 miles (300 km) across.