chicxulub

The asteroid that ended the Cretaceous period 66 million years ago released energy equivalent to roughly 100 million megatons of TNT — more than a billion times the bomb dropped on Hiroshima. That is not a metaphor. Scientists have calculated this from the crater geometry, the global debris layer, and the seismic signature preserved in rock. Understanding how energy scales from a hand grenade to a world-altering asteroid impact requires only arithmetic — and it reveals why some explosions leave no survivors within thousands of kilometers.

Sixty-six million years ago, a rock roughly 12 kilometers wide hit the Yucatán Peninsula at 20 kilometers per second, releasing energy equivalent to roughly one billion Hiroshima bombs. Within hours, wildfires swept continents. Within months, the sky went dark. Within a few thousand years, three-quarters of all species on Earth were gone — including every non-avian dinosaur.

Sixty-six million years ago, a six-mile-wide asteroid changed everything. But what if it had missed? Would mammals exist? Would humans? Here's what the science of evolution suggests.

Asteroid impacts have shaped Earth's history — including the extinction of dinosaurs. Here's what would happen if one hit tomorrow, and the science of how we're trying to prevent it.