Australian researchers have discovered evidence of a massive asteroid that struck Earth in its infancy. The impact would have been larger than anything humans have ever experienced; the researchers believe the asteroid is the second oldest known to have hit Earth, and is also one of the largest.
The discovery was made after a team of geologists, led by Andrew Glikson of the Australian National University (ANU), found a collection of spherules, which are tiny glass beads that are formed from material vaporized in the extreme heat of an asteroid impact. Glikson explained in a statement:
“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.
“Material from the impact would have spread worldwide. These spherules were found in sea floor sediments that date from 3.46 billion years ago.”
The glass beads were found by Dr. Glikson and Dr. Arthur Hickman from Geological Survey of Western Australia, in a drill core from Marble Bar in north-western Australia. The ancient ocean sediments, dated to the middle of the Archean Eon — around 3.46 billion years ago, are some of the oldest known sediments on Earth.
Because the sediment layer was preserved between two volcanic layers it made the dating of its origin very precise. The spread of the spherules deposit also suggest that the asteroid would have been around 12 and 18 miles (20 to 30 kms) in diameter, which would have left a crater hundreds of kilometers wide.
This impact also corresponds when the moon was struck by various asteroids, which formed the craters known as mare, that are still visible from Earth today. However, where this newly discovered asteroid struck remains unknown, with Glikson explaining:
“Exactly where this asteroid struck the earth remains a mystery.
“Any craters from this time on Earth’s surface have been obliterated by volcanic activity and tectonic movements.”
For the last two decades Glikson has been searching for evidence of ancient impacts and had suspected that the glass beads had originated from an asteroid strike. When tested the beads contained levels of elements like platinum, nickel, and chromium, which matched those in asteroids.
So far Glikson has found 17 ancient impacts; however he believes there are likely to be hundreds yet to be discovered, their ancient signatures just waiting to be unearthed. Glikson said:
“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.”