Mysterious Egyptian Glass Formed by Meteorite Strike, Study Says

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The glass deposits have been found in desert locations separated by tens of kilometers, suggesting a massive event.

But scientists have found no signs of an impact crater in the area.

"Usually from an impact like this, we should have a crater at least a kilometer [0.6 mile] across," Osinski said.

The absence of a crater, the scientists believe, suggests that the large space rock may have disintegrated upon entering Earth's atmosphere.

What happened may have been similar to the so-called Tunguska event, in which an asteroid exploded miles above the Earth's surface in a remote area of Siberia in 1908. That explosion felled an estimated 60 million trees over 830 square miles (2,150 square kilometers).

(See an interactive feature on asteroids.)

"There was no hole in the ground at Tunguska either," said Albert Haldemann, a planetary scientist at the Jet Propulsion Laboratory in Pasadena, California, who has been using radar to scour the Egyptian desert for impact signs.

"In an air burst like that, contents of the explosion continue to travel downward … providing a gas pulse across the [Earth's] surface that could vitrify sediments," Haldemann explained.

Life-Forms Killed

Scientists know much more about what happens when meteorites hit hard rock than when they impact sand and sedimentary rock, as would have been the case in the Egyptian desert.

At the time, there was a large lake in the area, the researchers say.

"If there was an impact at the surface and it happened to hit the lake, it wouldn't be surprising if the [crater] was filled in," Haldemann said.

"Did the event boil the entire lake away, or did it just cause a really big wave to go across the lake? Maybe we can figure that out from the sediments."

Kleindienst, the anthropologist, has been excavating at the site for more than 20 years as part of the Dakhla Oasis project.

(Her research has been partially funded by the National Geographic Committee for Research and Exploration. The committee and National Geographic News are both divisions of the National Geographic Society.)

Kleindienst has obtained a large amount of evidence, including spears and scrapers, to show that humans continually inhabited this region of Egypt's Western Desert during the Middle Stone Age, from about 200,000 to 30,000 years ago.

She has even found glass in lake sediments with archaeological evidence of human habitation in the soil layers below and above it.

"There is no reason to suspect that humans were not there at the time that this catastrophe happened," she said.

The meteorite research has important implications for understanding the environmental and human history at the time, Kleindienst added.

"Calculations at Meteor Crater [in Arizona] give some idea of what the effect of a [relatively small] impact would be," she said.

"Life forms are killed or seriously injured for many tens of kilometers away from the impact.

"If this event happened during a humid period, the area might have been ecologically repopulated fairly quickly from surrounding areas," she added.

"But if it happened during a dry period, it might have taken a considerable period for life to be re-established in the oasis region."

Haldemann, who is also the deputy project scientist on NASA's Mars Exploration Rover project, says the meteorite strike underlines the interconnectedness between Earth and the rest of the solar system.

"We already know the environment of the whole Earth is tied together," he said.

"What we've been learning more and more in the last 20 years or so is that we're also tied to the solar system as a whole over longer time periods and that this interaction tends to be punctuated by these catastrophic events.

"Here we have evidence in the [Early Stone Age] records that this kind of thing can really happen to us."

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