Scientists have uncovered the first definitive proof of a comet exploding in the Earth's atmosphere millions of years ago, destroying everything in its path.

The study, set for publication in Earth and Planetary Science Letters, was triggered by the presence of a black pebble uncovered by an Egyptian geologist years ago in an area of silica glass. After a range of tests, the scientists concluded that the object represented the "very first known hand specimen" originating from a comet nucleus, the press release on the study explains.

According to the researchers, the comet entered above Egypt roughly 28 million years ago. As it exploded, it heated up the sand beneath it to roughly 2,000 degrees Celsius, causing a mass amount of yellow silica glass to form -- a glass that lies scattered over a 6,000 square kilometer area in the Sahara.

The study could help unlock new insights not only into the early years of the planet, but of the solar system as well, the international team of researchers report.

"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," David Block of Wits University said in a statement.

In the past, the only material found originating from comets came in the form of microscopic dust particles in the upper atmosphere and the occasional carbon-rich dust in the Antarctic ice. Billions of dollars have been spent, the study authors report, to secure miniscule amounts of the extraplanetary remains.

"NASA and ESA (European Space Agency) spend billions of dollars collecting a few micrograms of comet material and bringing it back to Earth, and now we've got a radical new approach of studying this material, without spending billions of dollars collecting it," said Jan Kramers, a researcher from the University of Johannesburg.

According to the scientist, the identification of the specimen as a comet fragment was one of the defining moments of his career.

"It's a typical scientific euphoria when you eliminate all other options and come to the realisation of what it must be," he said.

The pebble, named "Hypatia" after the female mathematician, astronomer and philosopher of Alexandria, is now at the center of an international research program.

"Comets contain the very secrets to unlocking the formation of our solar system and this discovery gives us an unprecedented opportunity to study comet material first hand," Block said.