Photo courtesy of NASA
Though no longer visible, the Chicxulub Crater is one of the most infamous holes in Earth's prehistoric past. It was created approximately 65 million years ago when an asteroid measuring 6 to 9 miles (10 to 15 kilometers) across collided with the Earth at what is now the northern tip of the Yucatan Peninsula. The energy released upon impact was a billion times more explosive than the atomic bombs dropped over Nagasaki and Hiroshima, causing a cloud of superheated gas, ash, dust and pulverized rock to be thrown into the atmosphere. The cloud ultimately enveloped the planet, and as tiny droplets of superheated rock condensed in the atmosphere, glass rained down across the Earth's surface. The resulting crater -- which is now buried under several miles of limestone and is mostly underwater -- is 112 miles (180 kilometers) wide and is surrounded by a circular fault some 150 miles (240 kilometers) across [source: Rincon].
Scientists believe that the asteroid responsible for this incredible hole was also responsible for the extinction of the dinosaurs. The asteroid, which struck the Earth at a speed 20 times that of a bullet, killed instantly any creature in the immediate vicinity. The real devastation, however, resulted from the cloud of dust it kicked up, which blocked the sun for weeks or even months. This event caused winterlike conditions across the globe and wiped out half of the world's species. Today, all that remains of the impact crater is geologic evidence deep beneath the Earth's surface and a faint ring visible from outer space.