Nickel clue to 'dinosaur killer' asteroid

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http://www.bbc.com/news/science-environment-38299804

Nickel clue to 'dinosaur killer' asteroid

By Jonathan Amos
BBC Science Correspondent, San Francisco

1 hour ago

From the section Science & Environment

Scientists say they have a clue that may enable them to find traces of the asteroid that wiped out the dinosaurs in the very crater it made on impact. This pointer takes the form of a nickel signature in the rocks of the crater that is now buried under ocean sediments in the Gulf of Mexico.

An international team has just drilled into the 200km-wide depression. It hopes the investigation can help explain why the event 66 million years ago was so catastrophic. Seventy-five percent of all life, not just the dinosaurs, went extinct.

The UK-US led team gave an update on its research here at the Fall Meeting of the American Geophysical Union in San Francisco. The group is currently running all manner of lab tests on the hundreds of metres of core pulled up from under the Gulf in April and May.

One tantalising revelation is that the scientists observe a big nickel spike in the sediments immediately above what has become known as Chicxulub Crater. This is an important marker that could lead on to the discovery of asteroid material itself. The presumed 14km-wide space object would have been vaporised in the impact. But some portion of it would have condensed into small spherules in the sky to then rain back down on the bowl.

It should be stressed that the nickel is not in itself an identification of asteroid material. To have real confidence, the scientists would prefer to see the element iridium. This is extremely rare on Earth but is frequently associated with meteorites.

Iridium is apparent in the geological layers around the globe that mark the dinosaur-killing event at the end of the Cretaceous Period, but to find it in the actual crater would be an exciting observation. It could result in further insights on the nature of the asteroid that smashed into Earth. One theory is that its metals could have made the environment toxic for many lifeforms.
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