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13 March 2014 11:08 am ,
Vol. 343 ,
In the shadow of the crisis in Crimea, Ukrainian legislators are weighing a pair of science and education bills that...
Researchers dependent on government funding would face a flat future under the White House's $3.9 trillion budget...
Reservoirs of cells that harbor HIV DNA woven into human chromosomes have become the bane of researchers trying to cure...
Geochemists have now incorporated in their models some details of the way naturally acidic rainwater dissolves rock...
Schizophrenia is a devastating mental disorder that afflicts about 1% of the world's population at one time or another...
Surface tension is a force to be reckoned with, especially if you are small. It enables a water strider to skate along...
- 13 March 2014 11:08 am , Vol. 343 , #6176
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ScienceShot: Big Smash, Dead Dinos
7 February 2013 2:00 pm
Evidence that the impact of a kilometers-wide asteroid ravaged Earth's ecosystems and wiped out the dinosaurs millions of years ago is now stronger than ever. Using a high-resolution dating technique that measures the ratios of two argon isotopes, researchers analyzed 14 samples of material that had been flung from the impact site just north of the Yucatán Peninsula. Those dates, when combined with similar analyses reported previously, pin down the event—dubbed the Chicxulub impact after a small Mexican village closest to the offshore impact site—to approximately 66,038,000 years ago. And argon-argon dating of volcanic ash samples unearthed in Montana (image) from a bed of coal lying just a few centimeters above the iridium-rich layer deemed to contain fallout from the asteroid impact—and just 5 cm above rocks containing large amounts of dino-era pollen—suggests that mass extinctions occurred about 66,043,000 years ago. Considering the statistical errors in the two analyses, the impact and the dino die-offs may have occurred at the same time, or they may have occurred no more than 32,000 years apart, the researchers report online today in Science. Regardless, the team says, the new results certainly knock a hole in the notion that the mass extinctions, including the dinosaurs, occurred as much as 300,000 years before the asteroid impact, which some other researchers have contended for decades.
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