Planets and moons during the early Solar System were pelleted by asteroids a lot more than they are today. We can see the evidence of these impacts on the Moon, but the geological traces on our planet have been erased by erosion and plate tectonics. Despite these challenges, researchers have found evidence of an impact crater from 3.5 billion years ago.
The new crater is located in Western Australia’s Pilbara Craton, a place that has some of the oldest exposed rocks in the world. This place has allowed scientists to better understand the ancient history of our planet. The previous oldest crater record holder is also in Western Australia, the Yarrabubba crater.
“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,” study co-lead Professor Tim Johnson, from Curtin University, said in a statement.
The rocks suggested that a space rock impacted the ground at 36,000 kilometers an hour (22,370 miles per hour), leaving behind a crater 100 kilometers (61 miles) across. This would be enough to spread debris around the globe.
“We know large impacts were common in the early Solar System from looking at the Moon,” Professor Johnson said. “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.”
The rocks in Pilbara Craton provided evidence for the impact.
Image Credit: Curtin University
The team found shatter cones. These are peculiar rock formations that can only form under intense pressure. This kind of pressure can only be delivered by the catastrophic impact of outer space. In 2023, in the same region, a different team found evidence of impact spherules, suggesting meteorite impacts of similar age. The discovery of the crater provides fresh insights into the role that cosmic impacts might have played in the ancient Earth.
“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,” co-lead author Professor Chris Kirkland said.
“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.”
A paper describing this discovery is published in the journal Nature Communications.
