Scientists analyzing a mysterious pebble from Egypt have made a startling find: it's the nucleus of a comet.
The discovery is not only the first comet fragment ever found on Earth, it's also the first piece of definitive evidence that a comet ever struck Earth.
"Comets always visit our skies — they're these dirty snowballs of ice mixed with dust — but never before in history has material from a comet ever been found on Earth," says professor David Block of Wits University.
The international team of researchers began their research by studying a black pebble, nicknamed "Hypatia" after a well-known female mathematician from Alexandria, found by an Egyptian geologist years earlier. They soon realized the pebble was actually a remnant of a comet that had entered the Earth's atmosphere 28 million years ago in the skies above Egypt.
The comet then exploded and flash-heated the sand to a scorching 3,600 degrees Fahrenheit, creating a large amount of yellow silica glass and tiny diamonds over 2,300 square miles of the Sahara desert.
"Diamonds are produced from carbon bearing material. Normally they form deep in the earth, where the pressure is high, but you can also generate very high pressure with shock. Part of the comet impacted and the shock of the impact produced the diamonds," says professor Jan Kramers from the University of Johannesburg.
Comet samples are extremely valuable to scientists, who can only really obtain them from carbon samples in Antarctica and from the atmosphere. The Hypatia pebble offers experts a unique new viewpoint on Earth's history and the opportunity to search for more comet bits.
You can read the full published study detailing the findings in the journal Earth and Planetary Science Letters.