Glass found in the Egyptian desert was created by a meteorite impact around 29 million years ago, unravelling a riddle almost a century in the making.
Researchers believe that the origin of the so-called Libyan Desert Glass scattered across the Saharan desert in Egypt and Libya formed when an asteroid exploded in the Earth’s atmosphere.
Glass forms naturally when molten material cools so quickly that the molecules can’t settle into an ordered structure, like a crystal.
The glass has been found in ancient jewellery, including a scarab carved from the material which features in pectoral jewellery buried beside Tutankhamun.
Previous studies have claimed that the tiny greenish-yellow fragments were caused by an atmospheric air burst when asteroids, or Near Earth Objects, explode and shoot particles through the Earth’s atmosphere.
They say that the resulting airblast would have washed over the Egyptian desert, dumping vast amounts of heat into the sand.
The researchers, from Curtin University in Australia, examined the tiny grains of the mineral zircon in samples of the glass, which is found over several thousand square kilometres in western Egypt.
Zircons in the glass preserved evidence of the former presence of a high-pressure mineral named reidite, which only forms during a meteorite impact.
‘It has been a topic of ongoing debate as to whether the glass formed during meteorite impact, or during an airburst,’ said Aaron Cavosie, from Curtin University, who led the study.
‘Both meteorite impacts and airbursts can cause melting, however, only meteorite impacts create shock waves that form high-pressure minerals.’
Mr Cavosie said that finding evidence of former reidite confirms it was created as the result of a meteorite impact.
The idea that the glass may have formed during a large atmospheric airburst gained popularity after a dramatic airburst over Russia in 2013.
The airburst caused extensive property damage and injury to humans but did not cause surface materials to melt.
‘Previous models suggested that Libyan desert glass represented a large, 100-megatonnes (Mt) class airburst, but our results show this is not the case,’ Mr Cavosie said.
‘Meteorite impacts are catastrophic events, but they are not common.
‘Airbursts happen more frequently, but we now know not to expect a Libyan desert glass-forming event in the near future, which is cause for some comfort,’ he said.
The findings could help scientists understand the possible threat posed by potential asteroid strikes.
The findings were published in the journal Geology.