Nickel clue to 'dinosaur killer' asteroiddglg/Web/Claeys/pdf_media/News I Dec 15 - BBC -...
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ADVERTISEM Science & Environment 13 December 2016 Science & Environment Nickel clue to 'dinosaur killer' asteroid By Jonathan Amos BBC Science Correspondent, San Francisco Artwork: The asteroid impact removed 75% of all life on the planet 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. SPL News Sport Weather Shop Earth Travel
Transcript of Nickel clue to 'dinosaur killer' asteroiddglg/Web/Claeys/pdf_media/News I Dec 15 - BBC -...
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Science & Environment
13 December 2016 Science & Environment
Nickel clue to 'dinosaur killer' asteroidBy Jonathan AmosBBC Science Correspondent, San Francisco
Artwork: The asteroid impact removed 75% of all life on the planet
Scientists say they have a clue that may enable them to find traces of the asteroid thatwiped out the dinosaurs in the very crater it made on impact.
SPL
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This pointer takes the form of a nickel signature in the rocks of the crater that is now buriedunder 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 socatastrophic.
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 AmericanGeophysical Union in San Francisco.
The group is currently running all manner of lab tests on the hundreds of metres of core pulledup from under the Gulf in April and May.
One tantalising revelation is that the scientists observe a big nickel spike in the sedimentsimmediately above what has become known as Chicxulub Crater.
This is an important marker that could lead on to the discovery of asteroid material itself.
This animation illustrates the movement of rock in the impact (half of crater)
The presumed 14km-wide space object would have been vaporised in the impact. But someportion of it would have condensed into small spherules in the sky to then rain back down on thebowl.
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 eventat the end of the Cretaceous Period, but to find it in the actual crater would be an excitingobservation. It could result in further insights on the nature of the asteroid that smashed intoEarth. One theory is that its metals could have made the environment toxic for many lifeforms.
Philippe Claeys: "Four labs are independently chasing the iridium signal"
Four labs are currently testing for the presence of iridium. Prof Philippe Claeys from the FreeUniversity in Brussels says finding the Nickel is a very good sign.
"Nickel behaves chemically in a way that is very similar to iridium; it loves to make strongchemical bonds with iron, just like iridium," he told BBC News.
"So we treat nickel as what we call a proxy for an elevated concentration of iridium. If we seehigh nickel, it's very likely that we're going to have high iridium."
Chicxulub Crater - The impact that changed life on Earth
Today the outer rim (white arc) of the crater lies under Mexico's Yucatan Peninsula
A 14km-wide object dug a hole in the crust 100km across and 30km deep
This bowl then collapsed, leaving a crater 200km across and a few km deep
Its central zone rebounded and relaxed, producing an inner "peak ring"
The project team drilled its rock samples from this inner zone
Today, much of the crater is offshore, buried under 600m of sediments
On land, it is covered by limestone deposits, but its outline is visible
It is evident in an arc of famous sinkholes referred to as cenotes
NASA
Mexico's famous sinkholes (cenotes) have formed in weakened limestone overlying the crater
The project to drill into Chicxulub Crater was conducted by the European Consortium for OceanResearch Drilling (ECORD) as part of the International Ocean Discovery Program (IODP). Theexpedition was also supported by the International Continental Scientific Drilling Program(ICDP).
Rock was recovered from more than 1,300m below the modern seafloor in the Gulf of Mexico.
What has thrilled the team is the quality and abundance of material now in the labs.
"Why this is a jackpot core is because we have an expanded section. We have an amount ofmaterial that turns into a resolution that allows us to ask lots of questions," said Prof SeanGulick, the co-chief scientist from the University of Texas at Austin, US.
"For example, if we do see iridium especially in dust, it's not just a tracer for the impactor, itcould also tell us something about when this material left the atmosphere and things (the likelydark sky conditions following the impact) started clearing up."
Prof Tim Bralower from Pennsylvania State University is studying the core rocks for the fossils oftiny organisms that lived in the seawater above the crater - from the immediate aftermath of theimpact to millions of years hence.
What sort of species are present and how they change up through the sediments should tell himsomething about how long it took for "normal conditions" to return.
"It's unusual to see such a beautiful record of recovery in this exact location where the mass
MAX ALEXANDER/B612/ASTEROID DAY
extinction originated. Basically, 'ground zero'," he said.
[email protected] and follow me on Twitter: @BBCAmos
Share this story About sharing
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