A scar 180 kilometers wide
About 66 million years ago, an asteroid between 10 and 15 kilometers in diameter struck the shallow seas of the Yucatán Peninsula. The impact released energy equivalent to 100 trillion tons of TNT, creating a crater roughly 180-200 kilometers wide and initially 30 kilometers deep. This structure, now buried under hundreds of meters of sediment, is the Chicxulub crater, the only well-preserved crater of its size on Earth. Its main feature is a mountainous inner "peak ring," a structure common in large craters on the Moon and Venus but unique on our planet.
The formation of this peak ring was a process of unimaginable violence. The initial impact created a transient cavity, vaporizing rock and sending a plume of material into the atmosphere. The deep crust, subjected to immense pressure, rebounded upwards, momentarily forming a central peak taller than Mount Everest. This peak then collapsed outwards, creating the circular ring of mountains about 80-90 kilometers in diameter. The entire sequence, from impact to the final formation of the peak ring, took only a few minutes.
Drilling into ground zero
The peak ring remained a geophysical anomaly until 2016, when International Ocean Discovery Program (IODP) Expedition 364 used a liftboat, the L/B Myrtle, to drill into it from the Gulf of Mexico. Scientists drilled through 505 meters of seafloor and sediment to retrieve 835 meters of core samples from the peak ring itself. Scientists wanted to understand how solid rock could behave so fluidly to form such a structure.
The core samples provided a direct look at the crater's foundation: shocked granite. This granite, normally located deep within the Earth's crust, had been thrust upward by the impact. The extreme vibrations of the event caused a phenomenon known as "acoustic fluidization," where the shattered rock fragments behaved like a dense liquid for several minutes, allowing the peak ring to form. The recovered granite was highly porous and far less dense than typical granite, confirming the dynamic collapse models that scientists had proposed. The samples also recorded the mass extinction that followed. The cores lacked sulfur-bearing minerals, which were likely vaporized on impact, sending vast quantities of sun-blocking aerosols into the stratosphere and triggering a global winter.