[meteorite-list] meteorites from Earth Aw: Scientists Reconstruct Ancient, Massive Impact

From: Graham Ensor <graham.ensor_at_meteoritecentral.com>
Date: Thu, 10 Apr 2014 18:21:30 +0100
Message-ID: <CAJkn+kZjt1F2QO--WHN+sa+6vCiXkYfQ7vfxp01EuaoyHfQsLA_at_mail.gmail.com>

Interesting thought Thomas....what does NWA 5400 date at...that sits
on the Terrestrial fractionation line?

Any further work been done on that or it's pairings?


On Thu, Apr 10, 2014 at 3:15 PM, Thomas Kurtz <Thomas.Kurtz at gmx.de> wrote:
> 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
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Received on Thu 10 Apr 2014 01:21:30 PM PDT

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