Scientists have confirmed the age of the oldest known asteroid impact crater on Earth, revealing that a huge space rock struck our planet about 3 billion years ago.
The discovery helps researchers better understand the violent events that shaped the young Earth during its early history.
The research was carried out by a team from Curtin University and the Geological Survey of Western Australia.
They studied the North Pole Dome in the Pilbara region of Western Australia, an area that has long been thought to contain the remains of an ancient asteroid impact. For many years, however, scientists could not determine exactly when the impact happened.
The new study, published in the journal Geology, used advanced techniques to measure the age of tiny minerals inside the damaged rocks.
These methods allowed researchers to identify the most accurate date yet for the impact.
Lead researcher Professor Chris Kirkland explained that the asteroid strike left behind what he described as a “mineral clock.” Certain minerals were changed by the intense heat and pressure created when the asteroid crashed into Earth.
By studying these minerals, scientists could work out when the impact took place.
One of the most important minerals was zircon, which is extremely small but incredibly tough. Zircon crystals can survive for billions of years and often preserve valuable information about Earth’s history. At North Pole Dome, the researchers found unusual zircon crystals with strange branching shapes. They believe these crystals were damaged and partly rebuilt by the enormous heat generated during the asteroid impact.
When the team measured the age of these zircons, they found they were about 3 billion years old.
To make sure the result was correct, the scientists also studied another mineral called apatite. This mineral formed later as hot fluids flowed through cracks in the rocks after the impact. Remarkably, apatite gave the same age as the zircon crystals.
Professor Kirkland said the agreement between two completely different minerals gives the team strong confidence that they have correctly identified the timing of a single, major asteroid impact.
The discovery makes North Pole Dome the oldest confirmed impact crater on Earth and the only known impact crater from the Archean Eon, a period when Earth’s earliest continents were beginning to form and life was still in its earliest stages.
Finding evidence of such ancient impacts is extremely difficult. Over billions of years, rocks are changed by heat, pressure, erosion and underground fluids, which can erase many of the original signs of an impact. In this case, researchers were able to separate the evidence of the asteroid strike from the many geological changes that happened afterward.
The finding pushes Earth’s known impact record further back in time than ever before. Scientists hope it will provide valuable clues about how frequent asteroid impacts influenced the formation of the planet’s surface, early continents and possibly even the conditions that eventually allowed life to develop.
Researchers say discoveries like this highlight the importance of Western Australia’s ancient rocks, which continue to reveal remarkable chapters from Earth’s earliest history.
