[meteorite-list] Another Killer Crater Found -- Last Month

From: Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Sun Jun 4 21:07:58 2006
Message-ID: <007101c68839$a9c45e90$6402a8c0_at_Dell>

I'm convinced enough to "worry".
There's a something out there with Earth's name on it. I just can't see the
date from here!
----- Original Message -----
From: "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>
To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
Sent: Sunday, June 04, 2006 12:24 AM
Subject: [meteorite-list] Another Killer Crater Found -- Last Month


> Hi,
>
> Also, less than a month ago, there was a similar "proof"
> that the Bedout High, off the coast of north-western Australia,
> was a crater remnant, with impact melts, breccias, and an Ar/Ar
> date of 250.1 mya. Nobody much liked it, either...
> http://news.bbc.co.uk/1/hi/sci/tech/3707023.stm
> The announcement was made by Dr Luann Becker, of the
> University of California, Santa Barbara. The Bedout High is
> a seabed feature.
> Jay Melosh, of the University of Arizona in Tucson, commented:
> "This thing just rings off alarm bells in my mind. If it is an impact
> it's the most darn peculiar one I've ever seen."
> In some cases, there's no suspect at all. In others, there's
> just way too many suspects.
>
>
> Sterling K. Webb
> ----------------------------------------------------------------
> ----- Original Message -----
>> From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov>
>> To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com>
>> Sent: Friday, June 02, 2006 11:37 AM
>> Subject: [meteorite-list] Big Bang in Antarctica - Killer Crater Found
>> UnderIce
>>> http://researchnews.osu.edu/archive/erthboom.htm
>>>
>>> BIG BANG IN ANTARCTICA -- KILLER CRATER FOUND UNDER ICE
>>> Ohio State Research News
>>> June 1, 2006
>>>
>>> Ancient mega-catastrophe paved way for the dinosaurs, spawned Australian
>>> continent
>>>
>>> COLUMBUS, Ohio -- Planetary scientists have found evidence of a meteor
>>> impact much larger and earlier than the one that killed the dinosaurs --
>>> an impact that they believe caused the biggest mass extinction in
>>> Earth's history.
>>>
>>> The 300-mile-wide crater lies hidden more than a mile beneath the East
>>> Antarctic Ice Sheet. And the gravity measurements that reveal its
>>> existence suggest that it could date back about 250 million years -- the
>>> time of the Permian-Triassic extinction, when almost all animal life on
>>> Earth died out.
>>>
>>> Its size and location -- in the Wilkes Land region of East Antarctica,
>>> south of Australia -- also suggest that it could have begun the breakup
>>> of the Gondwana supercontinent by creating the tectonic rift that pushed
>>> Australia northward.
>>>
>>> Scientists believe that the Permian-Triassic extinction paved the way
>>> for the dinosaurs to rise to prominence. The Wilkes Land crater is more
>>> than twice the size of the Chicxulub crater in the Yucatan
>>> peninsula, which marks the impact that may have ultimately killed the
>>> dinosaurs 65 million years ago. The Chicxulub meteor is thought to have
>>> been 6 miles wide, while the Wilkes Land meteor could have been up to 30
>>> miles wide -- four or five times wider.
>>>
>>> "This Wilkes Land impact is much bigger than the impact that killed the
>>> dinosaurs, and probably would have caused catastrophic damage at the
>>> time," said Ralph von Frese, a professor of geological sciences at Ohio
>>> State University.
>>>
>>> He and Laramie Potts, a postdoctoral researcher in geological sciences,
>>> led the team that discovered the crater. They collaborated with other
>>> Ohio State and NASA scientists, as well as international partners from
>>> Russia and Korea. They reported their preliminary results in a recent
>>> poster session at the American Geophysical Union Joint Assembly meeting
>>> in Baltimore.
>>>
>>> The scientists used gravity fluctuations measured by NASA's GRACE
>>> satellites to peer beneath Antarctica's icy surface, and found a
>>> 200-mile-wide plug of mantle material -- a mass concentration, or
>>> "mascon" in geological parlance -- that had risen up into the Earth's
>>> crust.
>>>
>>> Mascons are the planetary equivalent of a bump on the head. They form
>>> where large objects slam into a planet's surface. Upon impact, the
>>> denser mantle layer bounces up into the overlying crust, which holds it
>>> in place beneath the crater.
>>>
>>> When the scientists overlaid their gravity image with airborne radar
>>> images of the ground beneath the ice, they found the mascon perfectly
>>> centered inside a circular ridge some 300 miles wide -- a crater easily
>>> large enough to hold the state of Ohio.
>>>
>>> Taken alone, the ridge structure wouldn't prove anything. But to von
>>> Frese, the addition of the mascon means "impact." Years of studying
>>> similar impacts on the moon have honed his ability to find them.
>>>
>>> "If I saw this same mascon signal on the moon, I'd expect to see a
>>> crater around it," he said. "And when we looked at the ice-probing
>>> airborne radar, there it was."
>>>
>>> "There are at least 20 impact craters this size or larger on the moon,
>>> so it is not surprising to find one here," he continued. "The active
>>> geology of the Earth likely scrubbed its surface clean of many more."
>>>
>>> He and Potts admitted that such signals are open to interpretation. Even
>>> with radar and gravity measurements, scientists are only just beginning
>>> to understand what's happening inside the planet. Still, von Frese said
>>> that the circumstances of the radar and mascon signals support their
>>> interpretation.
>>>
>>> "We compared two completely different data sets taken under different
>>> conditions, and they matched up," he said.
>>>
>>> To estimate when the impact took place, the scientists took a clue from
>>> the fact that the mascon is still visible.
>>>
>>> "On the moon, you can look at craters, and the mascons are still there,"
>>> von Frese said. "But on Earth, it's unusual to find mascons, because the
>>> planet is geologically active. The interior eventually recovers and the
>>> mascon goes away." He cited the very large and much older Vredefort
>>> crater in South Africa that must have once had a mascon, but no evidence
>>> of it can be seen now.
>>>
>>> "Based on what we know about the geologic history of the region, this
>>> Wilkes Land mascon formed recently by geologic standards -- probably
>>> about 250 million years ago," he said. "In another half a billion years,
>>> the Wilkes Land mascon will probably disappear, too."
>>>
>>> Approximately 100 million years ago, Australia split from the ancient
>>> Gondwana supercontinent and began drifting north, pushed away by the
>>> expansion of a rift valley into the eastern Indian Ocean. The rift cuts
>>> directly through the crater, so the impact may have helped the rift to
>>> form, von Frese said.
>>>
>>> But the more immediate effects of the impact would have devastated life
>>> on Earth.
>>>
>>> "All the environmental changes that would have resulted from the impact
>>> would have created a highly caustic environment that was really hard to
>>> endure. So it makes sense that a lot of life went extinct at that time,"
>>> he said.
>>>
>>> He and Potts would like to go to Antarctica to confirm the finding. The
>>> best evidence would come from the rocks within the crater. Since the
>>> cost of drilling through more than a mile of ice to reach these rocks
>>> directly is prohibitive, they want to hunt for them at the base of the
>>> ice along the coast where the ice streams are pushing scoured rock into
>>> the sea. Airborne gravity and magnetic surveys would also be very useful
>>> for testing their interpretation of the satellite data, they said.
>>>
>>> NSF funded this work. Collaborators included Stuart Wells and Orlando
>>> Hernandez, graduate students in geological sciences at Ohio State;
>>> Luis Gaya-Piqu?and Hyung Rae Kim, both of NASA's Goddard Space
>>> Flight Center; Alexander Golynsky of the All-Russia Research Institute
>>> for Geology and Mineral Resources of the World Ocean; and Jeong Woo Kim
>>> and Jong Sun Hwang, both of Sejong University in Korea.
>>>
>>> #
>>>
>>> Contact: Ralph von Frese, (614) 292-5635; Von-frese.3_at_osu.edu
>>>
>>> Laramie Potts, (614) 292-7365; Potts.3_at_osu.edu
>>>
>>> Written by Pam Frost Gorder, (614) 292-9475; Gorder.1_at_osu.edu
>>>
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>>>
>>
>>
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Received on Sun 04 Jun 2006 08:47:46 PM PDT