[meteorite-list] meteorites from Earth Aw: Scientists Reconstruct Ancient, Massive Impact
From: Thomas Kurtz <Thomas.Kurtz_at_meteoritecentral.com>
Date: Thu, 10 Apr 2014 16:15:13 +0200 Message-ID: <trinity-4e949a3a-d8ab-438f-be2f-36fc44e9aaa4-1397139313608_at_3capp-gmx-bs54> The question is: Which achondrites have creation ages of 3.23 billion to 3.47 billion years ? Perhaps we have material from this event among our collections. Some material might still be flying in the solar system, even 3 billion years later. Regards, Thomas Kurtz Weil der Stadt, Germany > Gesendet: Donnerstag, 10. April 2014 um 01:05 Uhr > Von: "Ron Baalke" <baalke at zagami.jpl.nasa.gov> > An: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com> > Betreff: [meteorite-list] Scientists Reconstruct Ancient, Massive Impact > > > > http://news.agu.org/press-release/scientists-reconstruct-ancient-impact-that-dwarfs-dinosaur-extinction-blast/ > > Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast > American Geophysical Union > Press Release > 9 April 2014 > > WASHINGTON, D.C. - Picture this: A massive asteroid almost as wide as > Rhode Island and about three to five times larger than the rock thought > to have wiped out the dinosaurs slams into Earth. The collision punches > a crater into the planet's crust that's nearly 500 kilometers (about 300 > miles) across: greater than the distance from Washington, D.C. to New > York City, and up to two and a half times larger in diameter than the > hole formed by the dinosaur-killing asteroid. Seismic waves bigger than > any recorded earthquakes shake the planet for about half an hour at any > one location - about six times longer than the huge earthquake that struck > Japan three years ago. The impact also sets off tsunamis many times deeper > than the one that followed the Japanese quake. > > Although scientists had previously hypothesized enormous ancient impacts, > much greater than the one that may have eliminated the dinosaurs 65 million > years ago, now a new study reveals the power and scale of a cataclysmic > event some 3.26 billion years ago which is thought to have created geological > features found in a South African region known as the Barberton greenstone > belt. The research has been accepted for publication in Geochemistry, > Geophysics, Geosystems, a journal of the American Geophysical Union. > > The huge impactor - between 37 and 58 kilometers (23 to 36 miles) wide > - collided with the planet at 20 kilometers per second (12 miles per second). > The jolt, bigger than a 10.8 magnitude earthquake, propelled seismic waves > hundreds of kilometers through the Earth, breaking rocks and setting off > other large earthquakes. Tsunamis thousands of meters deep - far bigger > than recent tsunamis generated by earthquakes - swept across the oceans > that covered most of the Earth at that time. > > "We knew it was big, but we didn't know how big," Donald Lowe, a geologist > at Stanford University and a co-author of the study, said of the asteroid. > > [Graphic] > A graphical representation of the size of the asteroid thought to have > killed the dinosaurs, and the crater it created, compared to an asteroid > thought to have hit the Earth 3.26 billion years ago and the size of the > crater it may have generated. A new study reveals the power and scale > of the event some 3.26 billion years ago which scientists think created > geological features found in a South African region known as the Barberton > greenstone belt. > Credit: American Geophysical Union > > Lowe, who discovered telltale rock formations in the Barberton greenstone > a decade ago, thought their structure smacked of an asteroid impact. The > new research models for the first time how big the asteroid was and the > effect it had on the planet, including the possible initiation of a more > modern plate tectonic system that is seen in the region, according to > Lowe. > > The study marks the first time scientists have mapped in this way an impact > that occurred more than 3 billion years ago, Lowe added, and is likely > one of the first times anyone has modeled any impact that occurred during > this period of the Earth's evolution. > > The impact would have been catastrophic to the surface environment. The > smaller, dino-killing asteroid crash is estimated to have released more > than a billion times more energy than the bombs that destroyed Hiroshima > and Nagasaki. The more ancient hit now coming to light would have released > much more energy, experts said. > > The sky would have become red hot, the atmosphere would have been filled > with dust and the tops of oceans would have boiled, the researchers said. > The impact sent vaporized rock into the atmosphere, which encircled the > globe and condensed into liquid droplets before solidifying and falling > to the surface, according to the researchers. > > The impact may have been one of dozens of huge asteroids that scientists > think hit the Earth during the tail end of the Late Heavy Bombardment > period, a major period of impacts that occurred early in the Earth's history > - around 3 billion to 4 billion years ago. > > Many of the sites where these asteroids landed were destroyed by erosion, > movement of the Earth's crust and other forces as the Earth evolved, but > geologists have found a handful of areas in South Africa, and Western > Australia that still harbor evidence of these impacts that occurred between > 3.23 billion and 3.47 billion years ago. The study's co-authors think > the asteroid hit the Earth thousands of kilometers away from the Barberton > Greenstone Belt, although they can't pinpoint the exact location. > > "We can't go to the impact sites. In order to better understand how big > it was and its effect we need studies like this,' said Lowe. Scientists > must use the geological evidence of these impacts to piece together what > happened to the Earth during this time, he said. > > The study's findings have important implications for understanding the > early Earth and how the planet formed. The impact may have disrupted the > Earth's crust and the tectonic regime that characterized the early planet, > leading to the start of a more modern plate tectonic system, according > to the paper's co-authors. > > The pummeling the planet endured was 'much larger than any ordinary earthquake," > said Norman Sleep, a physicist at Stanford University and co-author of > the study. He used physics, models, and knowledge about the formations > in the Barberton greenstone belt, other earthquakes and other asteroid > impact sites on the Earth and the moon to calculate the strength and duration > of the shaking that the asteroid produced. Using this information, Sleep > recreated how waves traveled from the impact site to the Barberton greenstone > belt and caused the geological formations. > > The geological evidence found in the Barberton that the paper investigates > indicates that the asteroid was "far larger than anything in the last > billion years," said Jay Melosh, a professor at Purdue University in West > Lafayette, Indiana, who was not involved in the research. > > The Barberton greenstone belt is an area 100 kilometers (62 miles) long > and 60 kilometers (37 miles) wide that sits east of Johannesburg near > the border with Swaziland. It contains some of the oldest rocks on the > planet. > > The model provides evidence for the rock formations and crustal fractures > that scientists have discovered in the Barberton greenstone belt, said > Frank Kyte, a geologist at UCLA who was not involved in the study. > > "This is providing significant support for the idea that the impact may > have been responsible for this major shift in tectonics," he said. > > Reconstructing the asteroid's impact could also help scientists better > understand the conditions under which early life on the planet evolved, > the paper's authors said. Along with altering the Earth itself, the environmental > changes triggered by the impact may have wiped out many microscopic organisms > living on the developing planet, allowing other organisms to evolve, they > said. > > "We are trying to understand the forces that shaped our planet early in > its evolution and the environments in which life evolved," Lowe said. > > Notes for Journalists > > Journalists and public information officers (PIOs) of educational and > scientific institutions who have registered with AGU can download a PDF > copy of this article by clicking on this link: > http://onlinelibrary.wiley.com/doi/10.1002/2014GC005229/abstract > > Or, you may order a copy of the final paper by emailing your request to > Nanci Bompey at nbompey at agu.org. Please provide your name, the name of > your publication, and your phone number. > > Neither the paper nor this press release is under embargo. > > Title > "Physics of crustal fracturing and chert dike formation triggered by asteroid > impact, ~3.26 Ga, Barberton greenstone belt, South Africa" > > Authors: > Norman H. Sleep: Department of Geophysics, Stanford University, Stanford, > CA, USA; > > Donald R. Lowe: Department of Geological and Environmental Sciences, Stanford > University, Stanford, CA, USA. > > Contact information for the authors: > Norman Sleep: +1 (650) 723-0882, norm at stanford.edu > > AGU Contact: > Nanci Bompey > +1 (202) 777-7524 > nbompey at agu.org > > ______________________________________________ > > Visit the Archives at http://www.meteorite-list-archives.com > Meteorite-list mailing list > Meteorite-list at meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list > Received on Thu 10 Apr 2014 10:15:13 AM PDT |
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