?Did giant meteorites hit the Earth around the year 500
A 600-meter-wide space object shattered into two pieces, which hit Earth off northern Australia, causing global cooling, according to a controversial theory.
Pieces of a giant asteroid or comet that shattered above Earth may have crashed into the sea off Australia around 1,500 years ago, according to a scientist who has found evidence of the possible presence of impact craters.
Satellite measurements of the Gulf of Carpentaria have revealed tiny changes in sea level that are signs of impact craters on the seabed below, according to new research by marine geophysicist Dallas Abbott.
Based on satellite data, one of the craters is expected to be about 18 kilometers wide, while the other is expected to be 12 kilometers wide.
For years, Abbott of Columbia University's Lamont-Doherty Earth Observatory has argued that V-shaped sand dunes along the Gulf Coast are evidence of a tsunami triggered by a impact.
"These dunes are like arrows pointing to their source," Abbott said. In this case, the dunes converge at a single point in the gulf, where Abbott found the two sea surface depressions.
The new work is the latest in evidence that links a major impact to an episode of global cooling that affected crops between 536 and 545 AD, Abbott says.
According to this theory, materials thrown into the atmosphere by the Carpentaria impact likely triggered the cooling, which was evidenced in tree ring data from Asia and Europe.
Moreover, around the same time the Roman Empire was collapsing in Europe, Australian Aborigines may have witnessed the double impact and recorded it, she added.
ABORIGINAL WITNESSES
Based on this new research, Ms Abbott believes the two craters were formed by an object that shattered into pieces as it approached Earth.
To create two craters of this size in the soft sediments of the ocean floor, the original object had to be 600 meters in diameter before shattering, she explained.
Cores taken from the area support the hypothesis of such an impact, Ms Abbott added. Previous research had revealed that the samples contained smooth, magnetic spherules, which were likely created when the object's explosive landing melted materials and hurled them into the sky.
Additionally, a 2004 paper in the journal Astronomy and Geophysics suggested that the planetary cooling that occurred around AD 500 may have been caused by dust from an impact roughly the size of the one Abbott calculated for Carpentaria. .
It's even possible the impact had eyewitnesses: Aboriginal rock art in the area appears to have recorded the event, although researchers who examined this art declined to discuss specifics until their paper was published. .
Nevertheless, Duane Hamacher, a PhD student at Macquarie University in Sydney who has not been involved in rock art work, recently demonstrated that Aboriginal stories can be used to locate meteorite craters.
“Many examples of flaming stars falling from the sky and striking the earth, causing death and destruction, are found in Aboriginal dreams [spiritual folk stories] across Australia,” Hamacher wrote on his blog.
“The descriptions seem to indicate that the events were observed and not simply 'made up'. »
In findings yet to be published, Hamacher used a collection of Aboriginal accounts, along with images in Google Earth, to locate a 280m impact crater in Palm Valley, Australia's Northern Territory.
?METEOR RAINS
But some experts are skeptical of Abbott's findings, which were presented last December at a meeting of the American Geophysical Union in San Francisco.
One potential problem is the presence of two separate craters at the Gulf of Carpentaria site, said physicist Mark Boslough of Sandia National Laboratories in Albuquerque, New Mexico.
According to him, if a large impactor had broken apart on its final approach to Earth, the fragments would have been very, very close together when they landed: "It will essentially behave as one piece, creating a single crater,” Boslough said.
Also, he added, Abbott and other members of an informal association called the Holocene Impact Working Group are finding evidence of more impacts than astronomers believe possible.
Abbott and his colleagues argue that several climatic events that occurred in the Holocene epoch - 11,500 years ago until today - were actually triggered by impacts, and therefore these large impacts are more frequent. than we currently believe.
Boslough and other experts, meanwhile, cataloged asteroids and other bodies that cross Earth's orbit and calculated how often space rocks are expected to hit the planet.
“We have a pretty good idea of their number and the frequency of impacts, and the abundances based on [the number of craters claimed by the working group] are several orders of magnitude higher than what astronomers observe,” said said Boslough.
“It's hard enough to imagine where these things might have come from that astronomers don't see them. »
Instead, the craters found by the task force are more likely to have volcanic origins, impact skeptics conclude.
Abbott acknowledges that his case for Carpentaria is not 100% proven. But overall, she says, "I think we're close to being able to demonstrate that there have been a lot of impacts over the past 10,000 years." »
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