UFO'S of UAP'S, ASTRONOMIE, RUIMTEVAART, ARCHEOLOGIE, OUDHEIDKUNDE, SF-SNUFJES EN ANDERE ESOTERISCHE WETENSCHAPPEN

The surfaces of the Moon, Mercury, and Mars are easily visible and are littered with impact craters. Earth has been subjected to the same bombardment, but geological activity and weathering have eliminated most of the craters. The ones that remain are mostly only faint outlines or remnants. However, researchers in Australia have succeeded in finding what they think is the oldest impact crater on Earth.

Their research, "A Paleoarchaean impact crater in the Pilbara Craton, Western Australia," is published in Nature Communications. The lead authors are Christopher Kirkland and Professor Tim Johnson, both from Curtin University in Australia. The Pilbara Craton is one of only two pristine Archaean sections of crust and is the subject of much geological research.

Impactors were more common in the distant past, especially large ones. In the Paleoarchaean era, which spans from about 3.6 to 3.2 billion years ago, the Solar System was much more chaotic than it is now. There were more asteroids and debris in orbit around the Sun, and more of them crashed into the planets and the Moon. Earth didn't escape this fate, and ancient impacts affected how the continents formed, shaped the environment, helped make Earth habitable, and affected the overall conditions of the planet.

"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," Professor Johnson said.

"We know large impacts were common in the early solar system from looking at the Moon. Until now, the absence of any truly ancient craters means they are largely ignored by geologists," said Johnson. "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 crater was excavated by a meteorite striking Earth at more than 36,000 km/h. The crater is more than 100 km wide, and the powerful impact would've affected the entire globe with flying debris. At the time, the only life was microbial and constrained to water.

The impact could have had a long-lasting effect on the Earth, helping shape the planet into what it is today. There's an ongoing scientific discussion about ancient impacts and their effect on the planet's crust. Some think these giant impacts could have initiated deep mantle plumes and subduction zones.

There's some evidence that giant impacts could've created mantle plumes and subduction zones.

Image Credit: Koppers et al. 2025. Mantle plumes and their role in Earth processes. Nat Rev Earth Environ. https://doi.org/10.1038/s43017-021-00168-6

Some scientists go even further and wonder if these large impacts could be responsible for Earth's continents.

"The role of meteorite impacts in the origin, modification, and destruction of crust during the first two billion years of Earth history (4.5–2.5 billion years ago; Ga) is disputed," the authors write. "Whereas some argue for a relatively minor contribution overall, others have proposed that individual giant impactors (>10–50 km diameter) can initiate subduction zones and deep mantle plumes, arguably triggering a chain of events that formed cratons, the ancient nuclei of the continents."

Cratons are the large, stable parts of Earth's crust and upper mantle, known as the lithosphere. As the continents moved around, sometimes merging and sometimes rifting, cratons survived. Scientists call them the 'seeds' of continents.

Many scientists think that Earth's ancient rocks formed above mantle plumes. Others think that the oldest rocks formed because of plate tectonics. In both cases, the formation is driven by heat from the planet's interior. However, Johnson and his colleagues are pursuing a different idea.

In a 2022 paper, Johnson and fellow researchers proposed that the heat necessary to form cratons and continents came from an otherworldly source: impacts. Impactors many kilometres in diameter could've delivered the heat. "Giant impacts provide a mechanism for fracturing the crust and establishing prolonged hydrothermal alteration by interaction with the globally extensive ocean," they wrote. Massive mantle melting from the impact would've created a thick nucleus that eventually formed a continent, they explained.

They were talking specifically about Australia's Pilbara Craton, the "best-preserved Archaean (4.0–2.5 billion years ago (Ga)) continental remnant."

Based on that, Kirkland, Johnson, and their fellow researchers knew where to look for evidence. While much of the evidence they had was microscopic, like zircon crystals and spherules, they wanted something more visible to convince other geologists. They knew what the evidence would look like: shatter cones. Shatter cones are rare and form in only two situations: in bedrock under impact craters or nuclear explosions. In both cases, there's an extremely powerful shock.

As Johnson explains in The Conversation, they went to the Pilbara for two weeks of fieldwork in 2021. Remarkably, they found shatter cones on the first day.

This image shows some of the shatter cones the researchers found in the study region.

Credit: Tim Johnson, Curtin University

"Our observations showed that above the layer with the shatter cones was a thick layer of basalt with no evidence of impact shock. This meant the impact had to be the same age as the Antarctic Member rocks, which we know are 3.5 billion years old," Johnson and his colleagues wrote in The Conversation.

This schematic shows the geological layers in the study area, the Antarctic Creek Member. "We speculate that the carbonate breccias represent the lithified and hydrothermally-altered products of impact-related deposits," the authors explain.

Image Credit: Kirkland et al. 2025

The Antarctic Member is a complex, mostly metasedimentary layer located in the central East Pilbara Terrane in Western Australia. This type of rock is first formed from solidified sediments. Then, it is buried under subsequent rock layers and subjected to heat and intense pressure, turning it into a metamorphic rock. Since the layers above it are unshocked, the researchers can date the impact.

This map from the published research shows the region's geology in detail. The study area is marked with a red star. The dashed lines are where spherules have been found in the region.

Image Credit: Kirkland et al. 2025

These findings are clear evidence of ancient impacts, which scientists were almost certain must have occurred just as they did on other Solar System bodies. They also offer evidence that ancient impacts formed cratons and, hence, led to the formation of continents. However, it's too soon to conclude that this is how things happened. It needs more research. This discovery will also likely drive further investigation into other ancient terranes on Earth for evidence of shatter cones.

Ancient impacts could have shaped our planet beyond geology. Some research shows that these ancient impacts could have given life an initial nudge. Their impacts provided long-lasting heat in the form of systems of hydrothermal vents. This allowed hot water to interact with rock, which could've created environments rich in chemistry and minerals. Scientists think these elements are critical for the emergence of life.

“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," Professor 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," Kirkland added.

"It may have even contributed to the formation of cratons, which are large, stable landmasses that became the foundation of continents," he concluded.