About 65 million years ago, a space rock six miles wide came hurtling towards Earth. When it hit, it bore a hole 18 miles deep, potentially smashing right through the crust and into the mantle, and leaving scars on this planet that remain to this day.
That’s the conclusion of a new study published in Science, part of an international research project that drilled cores of rock off the Mexican coast this year in an effort to uncover clues to the evolution of planets, and the extinction of all non-bird dinosaurs.
The study, led by Joanna Morgan of Imperial College London and Sean Gulick of the University of Texas at Austin, used rock samples from the Chicxulub crater to unlock the secrets of how asteroid and comet shape the planets they collide with.
The Chicxulub crater is the only one on Earth with a known peak ring, which is a circular formation of elevated material within the larger crater but offset from the center. These peak rings are familiar sights on rocky planetary bodies, including the moon, although on Earth they disappear relatively quickly through erosion and geological forces.
Core samples from Chicxulub’s peak ring, drilled from shallow ocean waters in the Gulf of Mexico, offer Earth-bound scientists a close look at where the material that formed these peaks came from.
There are differing theories about how peak rings form. In one model, the impactor drives deep into the planet, causing an upwelling of molten and solid rock, like the backsplash of a raindrop falling on water. This rises miles up overhead before collapsing and ultimately settling into an elevated ring of material that encircles the impact site. A less dramatic model shows the peak ring rising up like a splash around the center of the crater.
The researchers’ results show that the former is more likely, based on the composition of rocks sampled from the Chicxulub peak ring. This means that dinosaurs nearby would have been in for one hell of a volcanic show, at least until the blast of heat from the explosion got them.
If the Chicxulub asteroid carved a hole 18 miles deep, it could have seen a column of molten rock rise nine miles above Earth’s surface before collapsing under its weight. The air would have filled with fireballs, starting forest fires for thousands of miles around. Earthquakes, volcanoes, and tsunamis would have ensued, and when the planet fell quiet, the air would have been thick with enough ash and soot to blot out the sun.
It was, by any standard, a dark day for the planet, and up to 90 percent of all Earth’s species would ultimately go extinct in the aftermath. But, if you take the long view, it was also a moment of rebirth, when the stage was set for new species, and ultimately humans, to inherit the Earth.
The researchers plan to continue studying Chicxulub’s rocks, and answer how catastrophic impact events can open new spaces for the emergence of life, despite their enormous destructive power.
Rocks uplifted in the event ended up less dense and more porous, Gulick tells LiveScience. “When you get rocks with 10 percent more pore space, microbial life living below the surface may find new habitats on the surface. Our next area of research involves looking at whether ecosystems can get started by craters.”
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