Saturday, March 04, 2006

Crater found in Gilf Kebir

Instead of a Saturday Trivia this week (none found), here's piece about a new crater found from satellite images in the far southwest of Egypt, at the north west tip of the Gilf Kebir: "The crater is about 19 miles (31 kilometers) wide, more than twice as big as the next largest Saharan crater known. It tterly dwarfs Meteor Crater in Arizona, which is about three-fourths of a mile (1.2 kilometers) in diameter. In fact, the newfound crater, in Egypt, was likely carved by a space rock that was itself roughly 0.75 miles wide in an event that would have been quite a shock, destroying everything for hundreds of miles. For comparison, the Chicxulub crater left by a dinosaur-killing asteroid 65 million years ago is estimated to be 100 to 150 miles (160 to 240 kilometers) wide." The crater has been named "Kebira" (large) by Egyptian geologist Farouk el-Baz.
To see a photograph of the crater, and for the rest of the article, see the above web page address. (The Planetary Society)
Another article on the same subject, on the The Planetary Society website points to suggestions that this may have been the source of the somewhat mysterious Libyan Glass that can be found in this are of the desert, and was used in prehistoric times for making tools of the sort usually made in stone: "Study of the glass has revealed the unmistakable isotopic signature of an asteroid impact, but the source crater has never been found -- until now. El-Baz says that the crater he discovered is 30 kilometers in diameter, large enough to be the source of the glass." There is a ground level photograph of a similar, but much smaller crater in the same general area.
A press release also contains more information: " The researchers also found evidence that Kebira suffered significant water and wind erosion which may have helped keep its features unrecognizable to others. 'The courses of two ancient rivers run through it from the east and west,' added Ghoneim. 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. Kebira's shape is reminiscent of the many double-ringed craters on the Moon, which Dr. El-Baz remembers from his years of work with the Apollo program. Because of this, he believes the crater will figure prominently in future research in comparative planetology. And, since its shape points to an origin of extraterrestrial impact, it will likely prove to be the event responsible for the extensive field of “Desert Glass” – yellow-green silica glass fragments found on the desert surface between the giant dunes of the Great Sand Sea in southwestern Egypt." See the press release on the above website.

A good photo can be found here:

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