Overestimation of threat from 100 Mt–class airbursts? High-pressure evidence from zircon in Libyan Desert Glass

Clearing up the origins of Saharan glass

30 April 2020

Shockwaves from a comet strike may have created a mysterious glass found only in the Great Sand Sea of Egypt.

Libyan Desert Glass formed nearly 30 million years ago under high temperatures that some believe were generated by a meteorite exploding at the Earth’s atmosphere — an event known as an airburst.

By using electron microscopy to analyse the structure of zircon grains in Libyan Desert Glass samples, a team that included researchers from Curtin University could estimate the pressures and temperatures that created the mineral.

The orientation of the crystals in the zircon provided evidence that it contained reidite, a rare mineral associated with meteorite impacts as it forms under a sudden immense pressure, such as a massive shock. This suggests the glass is not the product of an airburst, but of a comet striking the Earth.

Understanding how such glasses of disputed origin emerged can help inform government policies on, and planned responses to, hazards from near-Earth objects.

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References

1. Geology 47, 609–612 (2019). doi: 10.1130/G45974.1