Friday, April 9, 2021

Asteroid Dust

 From EarthSky:

In February 2021 scientists announced the discovery of asteroid dust in the Yucatan’s famous Chicxulub crater, which has been linked for years to the dinosaurs’ extinction 66 million years ago. The scientists examined rock cores taken from the crater. They found iridium, a telltale element – rare on Earth – but abundant in certain asteroids. In the 1980s, a spike in iridium found in geologic layers across Earth led to the hypothesis that an asteroid wiped out the dinosaurs. In the 1990s, scientists found Chicxulub crater, off the Yucatan Peninsula of Mexico, and heralded it as a possible impact site. Now, scientists have found iridium in portions of Chicxulub crater itself. That discovery “seals the deal,” these researchers said.

Sean Gulick of University of Texas at Austin co-led the 2016 expedition to the Chicxulub crater with Joanna Morgan of Imperial College London. The expedition extracted nearly 3,000 feet (914 meters) of rock cores from the crater under the seafloor. Analyses of these rock cores led to the iridium discovery. Gulick said:

We are now at the level of coincidence that geologically doesn’t happen without causation. It puts to bed any doubts that the iridium anomaly [in the geologic layer] is not related to the Chicxulub crater.

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