The oldest impact crater on the planet was just discovered in Australia.

We discovered the oldest met stone impact crater on Earth in the heart of the Pilbara region of Western Australia. The crater was formed over 3.5 billion years ago and is the oldest for over 1 billion years. Our findings are published today on Nature Communications.

Strangely enough, the crater is exactly where we wanted it, and its discovery supports the theory of the birth of the first continent of Earth.

The first rock

The oldest rock on Earth formed over 3 billion years ago and is located in the core of most modern continents. However, geologists cannot yet agree on how or why they were formed.

Nevertheless, there is an agreement that these early continents are important to many chemical and biological processes on Earth.

Many geologists believe that these ancient rocks form on hot feathers rising above the Earth’s molten metal core, like the wax of a lava lamp. Others maintain what is formed by modern Earth-like plate-structure processes where rocks collide and push each other.

These two scenarios are very different, but both are driven by the loss of heat from within our planet.

We think about it quite differently.

A few years ago, we published a paper suggesting that the energy needed to create a Pilbara continent came from outside the Earth in the form of one or more collisions with metstones of many kilometers in diameter.

As the impact exploded a vast amount of material and melted the surrounding rocks, the mantle below produced thick “blobs” of volcanic material that had evolved into the continental crust.

Our evidence then lies in the chemical composition of small crystals of mineral zircon for the size of the grains of sand. But to persuade other geologists, they needed more persuasive evidence, preferably something that people could see without the need for a microscope.

So, in May 2021 we began a long drive north from Perth for a two-week fieldwork in Pilbara. There, I met with my partner at the Western Australia Geological Survey (GSWA) in search of the crater. But where should I start?

The beginning of a coincidence

Our first target was a rare layer of rock known as members of Antarctic Creek, harvested on the side of a dome about 20km in diameter. The Antarctic Creek members are only about 20 meters thick and consist primarily of sedimentary rocks sandwiched between several kilometres of dark basaltic lava.

However, bulbs are also included. This is a species formed from molten rocks thrown during the impact. But these drops may have traveled all over the globe, perhaps from the currently destroyed crater.

After consulting with GSWA maps and aerial photographs, we found an area to begin our search along the dusty track in the center of the Pilbara. We parked off-road vehicles, followed separate roads across the outcrop, and agreed to meet in an hour later, discussing what we found and taking a bite, if we wanted more than expected.

Surprisingly, when we got back in the car, we all thought we had found the same thing: crushed cones.

The crushed cone is a beautiful, delicate branched structure that is different from badminton shuttlecocks. They are the only characteristic of impact visible to the naked eye, and can only be formed in nature following the impact of metstones.

Within an hour of search, we found exactly what we were looking for. We literally opened the 4WD door and stepped into the floor of a huge, ancient impact crater.

Annoyed, I had to take some photos and grab some samples and then move to another site, but decided to go back as soon as possible. Most importantly, you need to know how old the crushed cone is. Have you discovered the oldest known crater on the planet?

It turns out we had.

Go back there

With several laboratory studies under our belt, we returned to the site in May 2024 to examine the 10-day evidence in more detail.

Grinding cones are everywhere, developed in most of Antarctica Creek’s members, and tracked them for hundreds of meters on the gentle hills of Pilbara.

Our observations showed that there was no evidence of impact shock over the layer of ground cone, and a thick layer of basalt. This meant that this influence had to be the same age as Antarctica member rock. I know this was 3.5 billion years ago.

We were old and had the oldest impact crater record on the planet. Perhaps our idea of ​​the ultimate origin of the continent was not so upset.

Serendipity is amazing. As far as we know, except for the traditional owners of Nyamal, no geologist has looked at these wonderful features since they were formed.

Like others before us, we argued that we played a fundamental role in the geological history of our planet, as we obviously had on the moons of our craters, and on the moons, and asteroids. Now we and others have the opportunity to test these ideas based on difficult evidence.

Who knows the number of ancient craters undiscovered in the ancient cores of other continents? Finding and studying them will change our understanding of the role of early Earth and the enormous influences not only in the formation of the land where we all live, but in the origins of life itself.

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