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L

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RE: Kebira Crater
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Torrent BBC Horizon 2006 Tutankhamuns Fireball is available for download

BBC Horizon 2006 Tutankhamuns Fireball

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L

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The BBC Horizon programme puts forward a very persuading case that the Kebir crater was not the origin of the desert glass, rather it was formed by an airburst of a much smaller 100 metre sized asteroid.

The airburst generated temperatures similar to the sun, and blew a huge plume of gas out into space. The glass wasn't from a crater or it's ejecta, if a crater is formed at all , but from the fireball that blasted huge areas of the surface.

Attempting to blow up an incoming asteroid, Hollywood style, could well make things worse by increasing the number of devastating airbursts.”

Download Audio (3.8mb, wmv)

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Desert Glass Scarab
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In 1996 in the Egyptian Museum in Cairo, Italian mineralogist Vincenzo de Michele spotted an unusual yellow-green gem in the middle of one of Tutankhamun's necklaces.



The jewel was tested and found to be glass, but intriguingly it is older than the earliest Egyptian civilisation.
Working with Egyptian geologist Aly Barakat, they traced its origins to unexplained chunks of glass found scattered in the sand in a remote region of the Sahara Desert.
But the glass is itself a scientific enigma. How did it get to be there and who or what made it?
Thursday's BBC Horizon programme reports an extraordinary new theory linking Tutankhamun's gem with a meteor.

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Scientists believe they have solved the mystery surrounding a piece of rare natural glass at the centre of an elaborate necklace found among the treasures of Tutankhamun, the boy pharaoh.

They think a fragile meteorite broke up as it entered the atmosphere, producing a fireball with temperatures over 1,800C that turned the desert sand and rock into molten lava which became glass when it cooled.
Experts have puzzled over the origin of the yellow-green glass — carved into the shape of a scarab beetle — since it was excavated in 1922 from the tomb of the teenage king, who died about 1323BC. It is generally agreed that it came from an area called the Great Sand Sea but there has been uncertainty over how it was formed because there is no crater to back up the idea of a meteorite strike.
Now it is thought that the meteorite responsible was not intact but made up of loose rubble.
"A fireball moving quicker than a hurricane force would have meant a blast of air so hot it could melt all the sand and sandstone on the ground" - Mark Boslough, an expert on impact physics based at the Sandia National Laboratories in New Mexico.

He recreated the effect on his computer and found that an object about 390ft in diameter and travelling at 12.4 miles a second would indeed produce enough heat to melt sand and create glass without leaving a crater as it broke up in the atmosphere.
The theory forms the basis of a BBC2 television programme, King Tut’s Fireball, to be shown next month.
"It would have become a molten lake of bubbling liquid sand and as the sand cooled it would have formed glass which ended up in King Tutankhamun’s jewellery" - Mark Boslough.

The necklace holding the 1in oval glass piece is housed in the Egyptian Museum in Cairo. It was one of hundreds of items discovered by the British archaeologist Howard Carter in a tomb in the Valley of the Kings in Luxor.
In his diary Carter described the brightly coloured gem as “greenish yellow chalcedony”. However, in 1999 Italian geologists tested the chemical composition of the scarab and concluded it was not chalcedony but natural desert glass, which is found only in the Great Sand Sea 500 miles southwest of Cairo.
Many meteorite craters can be seen only from space, so satellite photography experts examined the area.

"If this glass is of meteoric origin then there should be a crater of that age. But we did not find a smoking gun for silica (glass) there" - Farouk El-Baz, director of the centre for remote sensing at Boston University .

Chunks of glass were discovered in 1932 by Patrick Clayton, a British surveyor operating in the desert with the Egyptian Geological Survey. "He ran into this funny area with this glistening stuff all over the place," said his son Peter this weekend.
Next year an exhibition will be held in London showing for the first time many of the pieces found by Carter.

Source

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Hum,
it seems that the sandstone impact site is the source of the Libyan desert glass, which has been dated to 28.5 million years ago.

“The terrain in which the crater resides is composed of 100 million year-old sandstone – the same material that lies under much of the eastern Sahara. The researchers hope that field investigations and samples of the host rock will help in determining the exact age of the crater and its surroundings.”

There was no other exposed sandstone in the area...

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Position Latitude 24.691773° Longitude 24.972456°

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Libyan Desert Silica Glass used as tools 130.000 - 40.000 years ago.



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Scientists have discovered a 31 kilometre diameter crater in the Saharan desert
the newfound crater was created by an impact of an asteroid roughly 1.2 kilometres wide. As yet the exact date of when it occurred has not been determined.
The crater was discovered in satellite images by Boston University researchers Farouk El-Baz and Eman Ghoneim. The crater has two rings and two river have cut through the formation.


A colour-composite image from a Landsat satellite shows the newfound Kebira Crater in the Western Desert of Egypt, at the border with Libya. The outer rim of the crater is about 31 kilometres in diameter, indicated by the dotted line.

El-Baz named the crater “Kebira,” which means “large” in Arabic and also relates to its location on the northern tip of the Gilf Kebir region in southwestern Egypt.
The impact that carved Kebira might have created an extensive field of yellow-green silica fragments, known as desert glass and found on the surface between the giant dunes of the Great Sand Sea in southwestern Egypt

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