An asteroid struck the ocean’s continental shelf near the modern-day Mexican town of Chicxulub some 66 million years ago. The collision energy was 3 × 1023 J, which is equivalent to about 5 billion Hiroshima-sized atomic bomb explosions. Within seconds, the impact excavated a hole more than 20 km deep into Earth’s surface and threw bedrock and sediment into the upper atmosphere.
As impact ejecta fell back to Earth, the heat from their reentry generated a global pulse of thermal radiation similar to the conditions of an oven set on broil for about one hour. The thermal radiant flux and hot falling ejecta ignited widespread forest fires. The resulting soot blocked sunlight for several years, and the ensuing frigid surface temperatures led to widespread plant die-offs and the demise of a vast array of animals. Approximately 75% of species, most famously the non-avian dinosaurs, went extinct shortly after impact....
