An asteroid struck Australia 11 million years ago and no crater has ever been found

The Australian desert has housed mysterious glass blobs for centuries. Now scientists have found that they are proof of a meteorite impact 11 million years ago. Geoscientist Anna Musolino of Aix-Marseille University in France and her team studied these pieces of glass found in South Australia, also known as ananguites. They were surprised to learn that they were formed because of a giant asteroid impact. The biggest mystery is that there is no crater when the event must have been so powerful that it should have left mineral traces that persist in detectable quantities for millions of years, ScienceAlert reported. "These glasses are unique to Australia and have recorded an ancient impact event we did not even know about," geochronologist and geochemist Fred Jourdan of Curtin University in Australia said. The findings have been published in Earth & Planetary Science Letters.

"They formed when an asteroid slammed into Earth, melting surface rock and scattering debris for thousands of kilometres," he added, calling them tiny time capsules that hide a major event. Such a collision would have been massive, yet there is no crater, Fred said. Earlier, the Australasian strewnfield, which includes this particular part of the desert, was believed to have been a result of a giant meteorite impact somewhere in Southeast Asia around 788,000 years ago. These tiny glass beads are traditionally called tektites. In Australia, they are known as australites and are found in abundance. In 1969, scientists Dean Chapman and Leroy Scheiber of NASA analysed 530 australites and found that eight of them did not match the rest in mineral composition.

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Some glass beads in Australian desert formed in a separate asteroid impact

The finding raised doubts that they must have found from another impact. However, there was no other proof, and it died down. Now, Musolino decided to take another look to understand what could be the reason. These beads were denser, with higher magnetic susceptibility, different bubble patterns, and different ratios of trace elements. They scanned the australite collection at the South Australian Museum to find the odd beads that matched the profile. Their analysis proved that they were formed from a different impact on a different part of the crust from the Australasian strewnfield impact.

Argon dating on two of the six samples showed that the newly identified ananguites are 11 million years old, way older than the tektites that were formed 788,000 years ago. The absence of a crater deepens the mystery, which they believe likely vanished due to "intense weathering and the aridification of central Australia that started around 33 million years ago."