SCIENTISTS IN AUSTRALIA have found evidence of a huge asteroid that struck the Earth early in its life.
The asteroid is the second-oldest known to have hit the Earth and one of the biggest, with an impact larger than anything humans have experienced.
Tiny glass beads called spherules, which formed from vapourised material from the asteroid impact, have been found in seafloor sediments in northwestern Australia. They date from 3.46 billion years ago.
Dr Andrew Glikson from the Australian National University (ANU) said the impact would have “triggered earthquakes orders of magnitude greater than terrestrial earthquakes” and “huge tsunamis and would have made cliffs crumble”.
Glikson said the asteroid would have been 20 to 30 kilometres wide and would have created a crater hundreds of kilometres wide, while material from the impact would have spread worldwide.
About 3.8 to 3.9 billion years ago the moon was struck by numerous asteroids, which formed the craters that are still visible from Earth.
‘The tip of the iceberg’
“Exactly where this asteroid struck the earth remains a mystery,” Glikson said.
Any craters from this time on Earth’s surface have been obliterated by volcanic activity and tectonic movements.
Glikson and Dr Arthur Hickman from Geological Survey of Western Australia found the glass beads in a drill core from the Marble Bar, in some of the oldest known sediments on Earth.
The sediment layer, which was originally on the ocean floor, was preserved between two volcanic layers. This allowed for the very precise dating of its origin.
This is just the tip of the iceberg. We’ve only found evidence for 17 impacts older than 2.5 billion years, but there could have been hundreds.
“Asteroid strikes this big result in major tectonic shifts and extensive magma flows. They could have significantly affected the way the Earth evolved,” Glikson said.
The research has been published in the journal Precambrian Research.
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