Scientists investigate possibility of ancient meteor striking near Canada
New data shakes up controversial theory about a big climate shift
A new scientific theory posits that a meteor or comet impact near Quebec tossed hot melted rock along North America's Atlantic Coast about 12,900 years ago. The new research shakes up a controversial theory about a big climate shift called the Younger Dryas, when Earth abruptly swung into a glacial period 12,900 years ago.
The spherules from sites in North America and Europe, thought to be evidence of Younger Dryas comet impacts, the researchers have since discovered, didn't come from outer space.
Researchers say that at the time of the impact, the region was covered by a continental ice sheet, much like Antarctica and Greenland are today.
"We have provided evidence for an impact on top of the ice sheet," study co-author Mukul Sharma, a geochemist at Dartmouth College in Hanover says.
This shakes up the conventional wisdom about a big climate shift called the Younger Dryas, when Earth abruptly swung into a glacial period 12,900 years ago. The cooling had been previously attributed to a sudden shutdown in Northern Atlantic Ocean currents, which were the result of a big glacial lake flood out the St. Lawrence or Mackenzie Rivers.
Scientists in 2007 suggested that comet or meteor impacts or atmospheric fireballs triggered the Younger Dryas, though no crater of the right age has ever been found.
Sharma and his colleagues, analyzing the tiny particles from New Jersey and Pennsylvania, say they have never been accurately dated. The particles could be several thousands years older than the widespread glacial event.
"We are assuming they are Younger Dryas, but [dating] is one of the things that should be done better," Sharma says.
And geochemical tracers in the molten rock show it can't be traced back to a recently discovered impact crater near Quebec called Corossal crater, thought to be Younger Dryas-age.
The spherules from sites in North America and Europe, thought to be evidence of Younger Dryas comet impacts, the researchers have since discovered, didn't come from outer space. Sharma and his colleagues measured osmium isotopes in the melted rock and their surrounding sediment. Meteorites usually carry much more osmium than Earth rocks. But none of the spherules were extraterrestrial, Sharma said.
"Clearly these things were produced in an impact fireball, but we didn't find any evidence of meteorites," Sharma said.
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