Australian researchers have stumbled on proof of a massive asteroid colliding with Earth during our planet's early life.
The impact – deemed bigger than anything experienced by humans – produced tiny glass beads known as spherules, which formed from vaporized matter. These beads were recently discovered in northwestern Australia.
“The impact would have triggered earthquakes orders of magnitude greater than terrestrial earthquakes, it would have caused huge tsunamis and would have made cliffs crumble,” said study author and Australian National University professor Andrew Glikson, adding that asteroid impact material also would have spread around the world.
The spherules were detected in seafloor sediments dating back 3.46 billion years. Glikson and Arthur Hickman from the Geological Survey of Western Australia found them in a Marble Bar drill core, in some of Earth’s oldest known sediments.
Highly precise dating was made possible by two volcanic layers sandwiching the sediment layer, originally situated on the ocean floor. Additional testing saw that the elements in the samples – including nickel, platinum and chromium – matched those found in asteroids.
The involved asteroid, apart from being the second oldest known, is among the largest to hit the planet, at an estimated 20 to 30 kilometers (12 to 19 miles) across and likely creating a crater spanning hundreds of kilometers wide.
About 3.9 billion years earlier, before the collision of the said asteroid, the moon was already hit by numerous ones that produced craters dubbed as mare. These are still seen from Earth today.
According to Glikson, it remains unknown specifically where the asteroid hit the planet. Craters from that time on the planetary surface have since been wiped out by volcanic motion and tectonic movements.
He added, however, that this is only “the tip of the iceberg,” as there could be hundreds more while scientists have only found proof of 17 impacts older than 2.5 billion years.
Asteroid impacts of this magnitude are believed to lead to significant tectonic shifts as well as massive magma flows, and probably had a substantial effect on Earth’s evolution.
The findings were discussed in the Precambrian Research journal.
Researchers from Dublin in Ireland also recently tested the alternative asteroid crater theory by analyzing a relatively younger asteroid crater: the Sudbury impact crater located in Ontario, Canada.
They proposed that contrary to previously thought, zircon crystals – the oldest rock pieces on the planet – may have been formed in the impact craters left by ancient asteroids.