First Evidence Found of a Comet Strike on Earth

Comets haven’t been observed entering Earth’s atmosphere (shown here: Hale-Bopp in 1997).

Saharan glass and a brooch belonging to King Tut provide the first evidence of a comet directly impacting Earth, a new study claims. The finding may help unlock some of the mysteries surrounding the birth of our solar system.

A brooch owned by Tutankhamun. Photograph courtesy Jon Bodsworth via University of the Witwatersrand

About 28 million years ago a comet exploded over Egypt, creating a 3600°F (2000°C) blast wave that spread out over the desert below. The fiery shockwave melted the sand, forming copious amounts of yellow silica glass scattered over 2,300 square miles (6,000 square kilometers) of the Sahara.

Polished into the shape of a scarab beetle, a large piece of this glass found its way into a brooch owned by the famed Egyptian boy king Tutankhamen.

“Because there is no sign of an impact crater, it has been a mystery as to what kind of celestial event actually could have caused this debris field, but a small, black stone found lying in the middle of the glass area caught our attention,” said study co-author David Block, an astronomer at Wits University in Johannesburg, South Africa.

Saharan Surprise

A tiny slice of the black pebble was put through isotopic analysis, which definitely ruled out that it came from a meteor. Instead, the analysis showed that the pebble possessed the unique chemical signature of a comet, measured in terms of elements such as argon and carbon.

“It was then basically a matter of running the movie backwards in time and predicting what temperatures were needed to create the conditions we find that make up the fragment today,” Block says. “So when I saw the result of the analyses, I was completely ecstatic to realize that such a piece of cosmic history has been found for the first time right on our doorstep.”

Read more at National Geographic

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