Scientists have discovered the world’s oldest known meteorite impact crater. Located in Western Australia, the crater has been dated to about 3.5 billion years ago, at a time when these almost literally Earth-shattering events should have been occurring regularly.
The crater was discovered by geologists at Curtin University and the Geological Survey of Western Australia in the Pilbara region of northwestern Australia. While it’s hard to see directly as a classic crater shape, due to its age, the team found it through other evidence – namely “shatter cones,” geological features that form only when exposed to extreme pressures, like meteorite impacts or underground nuclear explosions.
The newly discovered crater is estimated to be at least 100 km (62 miles) wide, which suggests the original object that crashed into Earth was traveling at more than 36,000 km/h (22,000 mph), and would have caused destruction on a global scale. The impact appears to have occurred 3.47 billion years ago.
“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,” said Professor Tim Johnson, co-lead author of the study.
That former recordholder is the Yarrabubba impact structure, located roughly 800 km (500 miles) south of the new champion. Most intriguingly, the newest (and oldest) crater dates back to a very tumultuous time in Earth’s history.
For the first two billion years of its life, Earth was regularly pummeled by huge space rocks, including an absolutely mammoth collision with a Mars-sized body that gave birth to the Moon about 4.5 billion years ago. The problem is, there aren’t many craters from that long ago, because plate tectonics, erosion and other processes have wiped away the evidence.
The Moon, meanwhile, still bears many large scars from this period, because its surface is far less active.
“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.”
The researchers say that impacts of this magnitude could have had dramatic effects on the planet, steering its evolution in ways that are still apparent today.
“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 Chris Kirkland, co-lead author of the study. “It may have even contributed to the formation of cratons, which are large, stable landmasses that became the foundation of continents.”
The research was published in the journal Nature Communications.
Source: Curtin University
