Scientists believe they have solved the mystery regarding the origin Egyptian desert glass, fragments of which have been found scattered across the Sahara.
Glass forms naturally when molten material cools so quickly that the molecules can’t settle into an ordered structure such as a crystal.
Yellow desert glass in Egypt has been found in ancient jewellery, including a scarab carved from the material which features in pectoral jewellery buried beside the pharaoh Tutankhamun.
Mysteriously the glass is scattered across tens of square kilometres of the Sahara in Egypt and Libya.
Scientists have now established that this glass was created by a meteorite impact rather than the airburst of a meteor which exploded in the atmosphere.
The work published in the journal Geology, by researchers from Curtin University in Australia, examined tiny grains of zircon found in samples of the glass, which formed 29 million years ago.
It shows how the canary yellow glass had traces of an extremely rare mineral called reidite which only forms during meteorite impacts.
The study’s lead author Dr Aaron Cavosie said: “It has been a topic of ongoing debate as to whether the glass formed during meteorite impact, or during an airburst.
“Both meteorite impacts and airbursts can cause melting, however, only meteorite impacts create shock waves that form high-pressure minerals, so finding evidence of former reidite confirms it was created as the result of a meteorite impact.”
Dr Cavosie explained that the airburst hypothesis gained a lot of traction after an airburst over the Russian region of Chelyabinsk in 2013.
Although it never collided with the surface of the Earth, the Chelyabinsk meteor strike in 2013 injured hundreds of people when it exploded.
It briefly outshone the sun and inflicted severe burns on observers below, as well as smashing windows and rattling buildings.
“Previous models suggested that desert glass represented a large, 100-megaton class airburst, but our results show this is not the case,” Dr Cavosie said.
“Meteorite impacts are catastrophic events, but they are not common. Airbursts happen more frequently, but we now know not to expect a desert glass-forming event in the near future, which is cause for some comfort.”