A team of Australian scientists from Curtin University uncovered the world's oldest known meteorite impact site—a 3.47 billion-year-old crater in the remote Pilbara region of Western Australia. The discovery pushes back the record for the oldest known impact on Earth by more than a billion years.
The researchers identified the crater, dubbed the North Pole Crater, about 40 kilometers west of Marble Bar. The team discovered distinctive rock formations known as shatter cones, which are only formed under the intense pressure of a meteorite impact and are considered unambiguous evidence of such an event.
"The tremendous amount of energy from this impact could have played a role in shaping early Earth's crust by pushing one part of the Earth's crust under another, or by forcing magma to rise from deep within the Earth's mantle toward the surface," said Professor Tim Johnson. The impact is estimated to have occurred at a speed of about 36,000 kilometers per hour, resulting in a crater over 100 kilometers wide. The colossal collision would have ejected debris into the atmosphere and around the globe, indicating a worldwide impact event.
"Uncovering this impact and finding more from the same time period could explain a lot about how life may have gotten started, as impact craters created environments friendly to microbial life such as hot water pools," said Professor Chris Kirkland, a co-lead author of the study, according to Popular Science.
Before this discovery, the title of Earth's oldest known impact site belonged to the 2.2-billion-year-old Yarrabubba crater, also located in Western Australia. The new finding predates it by more than a billion years. Johnson pointed out that the lack of any ancient craters on Earth led geologists to largely overlook their significance.
"Observing the Moon, we know that large impacts were common in the primordial Solar System," he stated, according to The Independent. The scarcity of ancient impact sites on Earth is largely due to billions of years of erosion and the subduction of primary crust into the planet's mantle. However, the East Pilbara Terrane, where the North Pole Crater was found, is a near-pristine fragment of ancient cratonic crust that has allowed scientists to better understand Earth's early history.
The study, published in the journal Nature provides fresh insights into the role that cosmic impacts might have played in shaping the planet.
"Finding direct evidence for Archaean impacts, such as craters or impact structures, is important for better constraining the Archaean impact flux," the Nature article states. The researchers believe that the immense energy released by such an impact event may have triggered geological processes like crust recycling and magma movement, contributing to the formation of Earth's crust and possibly the continents themselves.
"It also radically refines our understanding of crust formation—the tremendous amount of energy from this impact could have played a role in shaping early Earth's crust," noted Kirkland. The craters left behind by these ancient impacts might have been the places where life on Earth began.
The existence of this ancient crater suggests that Earth was previously hit by huge impacts that we may not know about, and researchers believe there may be more hidden craters waiting to be found. "Large impacts were far more common in the early Solar System, but until now, evidence of these ancient craters was missing from Earth's geological record," stated Johnson, according to Popular Science.
The team plans to continue their research in the area, hoping to uncover more evidence of ancient impacts. "This study provides a crucial piece of the puzzle of Earth's impact history and suggests there may be many other ancient craters that could be discovered over time," said Johnson.
The article was written with the assistance of a news analysis system.