Crater drilling sheds light on dinosaur-killing asteroid strike

Researcher  Sean Gulick, of the University of Texas, discusses a massive asteroid strike in...
Researcher Sean Gulick, of the University of Texas, discusses a massive asteroid strike in Mexico 66 million years ago. Photo: Gregor Richardson
Scientists who recently drilled into a huge impact crater in Mexico have learned much more about a huge asteroid strike which wiped out most of the dinosaurs, 66 million years ago.

Research Prof Sean Gulick, of the Institute of Geophysics, at the University of Texas, outlined many of the research findings in a talk, titled "Life and Death by Impact: Drilling for Clues", at the University of Otago geology department this week.

Successful drilling into the crater on the Yucatan Peninsula,  undertaken through the International Ocean Discovery Programme, had deepened scientific understanding of impact craters, he said.

The Mexican impact had produced the 200km-wide Chicxulub crater, and, by some estimates, "drove the extinction of 75% of life on Earth" in genus terms, "including all non-avian dinosaurs",  Prof Gulick said.

If the asteroid had struck only 30 seconds earlier or later, it would have landed relatively safely in the ocean, rather than on land.

Scientists say that under these scenarios, dinosaurs probably would have survived.

The asteroid had struck in a "very unfortunate place", Prof Gulick said.

The rocks where the asteroid landed were rich in sulphur, and an estimated 100 billion tonnes of sulphates were thrown into the atmosphere.

This amount of dust was enough to cool the planet for a decade and to "wipe out most life".

Most dinosaurs  died but smaller mammals — and ultimately humans — were later able to thrive, he said.

The asteroid impact had led to the most recent of the earth’s five major extinction events, and its wide-ranging effects showed "the pretty impressive use of the reset button", in evolutionary terms.

It was "amazing" that scientists had obtained "the complete record" of geological layers after the big impact, showing how some forms of life had later developed, he said.

john.gibb@odt.co.nz

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