The world's oldest known impact crater has been identified in the Pilbara, which is a part of Western Australia, according to new research reported in Nature Communications. The crater was made about 3.5 billion years ago by a meteorite. In this work, researchers went to a site in the Pilbara called the North Pole Dome to analyze its rock layers, and determined that a major meteorite struck there long ago.
These findings may change how scientists perceive and understand the origin of life on Earth. “Before our discovery, the oldest impact crater was 2.2 billion years old, so this is by far the oldest known crater ever found on Earth,” noted corresponding study author Professor Tim Johnson of Curtin University.
Johnson noted that this discovery has challenged assumptions about the ancient history of Earth.
Rock formations known as shatter cones, which are only created by the extreme pressure of a meteorite impact, were the key to this discovery. A meteorite generated these shatter cones when it hit at about 36,000 kilometers per hour (22.369 miles per hour). This impact made a crater that was about 100 kilometers (62 miles) wide, and likely sent debris into the atmosphere that then traveled around the world.
“We know large impacts were common in the early solar system from looking at the Moon,” said Johnson. “Until now, the absence of any truly ancient craters means they are largely ignored by geologists. 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.”
“Uncovering this impact and finding more from the same time period could explain a lot about how life may have got started, as impact craters created environments friendly to microbial life such as hot water pools,” added first study author Professor Chris Kirkland, also of Curtin University.
“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 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. It may have even contributed to the formation of cratons, which are large, stable landmasses that became the foundation of continents,” said Kirkland.
Sources: Curtin University, Nature Communications
