https://www.scientificamerican.com/article/scientists-spot-giant-crater-hidden-under-greenlands-ice/ > Earth hides its scars well; the planet has endured countless millennia of eruptions and collisions, but scientists are still stumbling upon the evidence of all that geologic drama. > Now, one such team has announced that it spotted a scar hidden below Greenland’s ice, a giant crater nearly 20 miles (31 kilometers) wide. The researchers said a giant iron meteorite likely created the mark by slamming into Earth sometime in the past 3 million years.