Jun
04
2006

Largest killer asteroid crater found


Meteor Crater near Winslow, AZ: This crater formed when a meteor collided with Earth about 50,000 years ago. It is approximately 3/4 mile in diameter and 650 feet deep.
Courtesy Mark Ryan

A 300 mile wide crater (bigger than Ohio) has been detected beneath a half-mile of ice in Anartica. This crater is twice as big as the one thought to have killed the dinosaurs. Reseachers believe the impact may have broken up the Gondwana supercontinent, pushing what is now Australia northward.

Two separate data sets were combined to understand more about this impact. Radar to detect a crater, and gravity measurements to detect a mass concentration, or "mascon" in the same place. When a large mass slams into the earth, there is a rebound of mantle material up into the earth's crust creating a bump or mascon..

"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." Ralph von Frese, a professor of geological sciences at Ohio State University

The Permian-Triassic extinction about 250 million years ago, when almost all animal life on Earth died out, may have resulted from this impact.

Not all scientists agree, however

Scientists contacted by news@nature.com say they are sceptical, as no signs of such an enormous impact have been found in other, well-studied areas of Antarctica. Jane Francis, a geologist at the University of Leeds says, "That sequence has been worked on before, and no one has found evidence to support a massive impact like this," Paul Wignall, a palaeontologist at the University of Leeds, UK, who studies mass-extinction events says that few scientists will be convinced by the hypothesis until the team can precisely date their crater directly, and find rocks there that have been altered by the searing heat of the explosion.

Most think that the extinction started when a vast volcanic eruption released huge amounts of gas, including sulphur dioxide and carbon dioxide, into the atmosphere, causing acid rain and greenhouse warming. Von Frese notes that the explanations aren't mutually exclusive: the shockwaves from a huge impact could have travelled through the planet to trigger the eruptions in Siberia, delivering a devastating combination of disasters.

Too much ice covers the putative crater for a drilling expedition. But Von Frese hopes to make a research trip to Antarctica to look for rocks at the base of the ice sheet along the continent's coast that could attest to an impact.

Sources:
NatureNews
physorg
space
BBCnews
Yahoo news

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Your Comments, Thoughts, Questions, Ideas

mdr's picture
mdr says:

Some scientists don’t agree with this interpretation of the data. According to Ian Dalziel, a geologist at the University of Texas in Austin, the apparent mascon could have been formed from normal geological processes. He also said that gravity anomalies like this aren’t uncommon. Other scientists point to the lack of other evidence of an impact. A crater this size – if it is a crater – would require the object of impact to have been about 50 kilometers (30 miles) across! The collision blast from an object this size would have severely altered surrounding rock, but no evidence of this has been detected. More info can be found here.

posted on Sun, 06/04/2006 - 9:52pm
ARTiFactor's picture
ARTiFactor says:

Thank you for the link. News@nature.com is a wonderful source for science news. Watching scientists debate which reality should be accepted shows us how science works. I have updated the post above to represent the other side of the debate.

posted on Mon, 06/05/2006 - 9:31am
Charlottecristin's picture

What I think after reading this and links provided here is - All Mountains are part of the huge and massive craters or asteroids from outer space but question arises why earth has atmosphere, why human can’t live without oxygen, why life exists here only.
So many questions like thins which i explore Internet but can’t find the exact solution but thanks for the geological department, scientists, mining and drilling industry which are working to explore the earth actual existence.

posted on Thu, 05/23/2013 - 11:14pm

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