Oldest Australian impact crater debate hinges on dates

North Pole – A giant 3-billion-year-old asteroid impact in Western Australia could be Earth’s oldest, but another research team says it’s younger. The dispute now centers on whether minerals inside the shocked rocks truly record the impact age—or whether earlier conclusion

A huge crater in Western Australia, known as the North Pole Dome crater and also called the Miralga impact structure, is back at the center of a battle over Earth’s deep past: how old its asteroid strike really was.

The crater was created by an asteroid impact about 3 billion years ago, according to a mineral-dating technique reported this year. If that timing holds, it would make the North Pole Dome crater the oldest impact crater on Earth—but other researchers say the age still doesn’t add up.

The story starts with Chris Kirkland of Curtin University in Perth. Australia. who first described the North Pole Dome crater. along with colleagues. in 2025. In their initial work, Kirkland and his team estimated the crater could be up to 100 kilometres wide. They identified a layer of rock containing cone-shaped features called shatter cones—structures that form only after a high-impact event such as an asteroid strike.

In that first study, the team did not directly date the shocked rock itself. Instead. they proposed an impact age of 3.47 billion years by correlating the undated shatter-cone-bearing layer with rocks above and below that were already dated. That estimate. if correct. would have pushed the impact more than 1.2 billion years older than the Yarrabubba crater in the south of Western Australia. which is regarded as the oldest reliably dated asteroid-strike crater on Earth.

It would also have made the North Pole Dome crater the only known impact from the Archaean aeon—an era when the entire planet was a giant but inhospitable water world.

But another team, including Aaron Cavosie at Curtin University, strongly contested that 3.47-billion-year date. After analyzing rocks from the area, Cavosie and his colleagues argued that the impact took place no earlier than 2.77 billion years ago.

Kirkland’s response has been a shift from inference to direct measurement. In the new work, Kirkland and his colleagues say they successfully dated recrystallised minerals at the crater site that contain shatter cones.

“We have now actually looked inside the rocks and tried to find minerals that directly responded to impact in the rock itself, rather than making correlations,” Kirkland said.

To do that, the team used the rate of uranium decaying into lead to date zircons within the shatter cones. The zircons, the researchers argue, recrystallised as a result of the force of the asteroid strike.

They also dated apatite. a mineral they say would have formed in the hydrothermal system created by heat from the impact. Both the apatite and the zircons returned dates of around 3.02 billion years old, Kirkland reported. That. he said. points to “very hot water percolating through the rocks 3 billion years ago” and to a “really unusual heating and recrystallisation process.”.

Kirkland argues that no other known process—such as mountain building or regional metamorphism—could easily explain the mineral changes inside the shocked rocks at about 3.02 billion years ago. He said there is no evidence the area was heated or deformed by those processes at that time.

“The only process really that we can link to these mineralogical changes is an impact,” Kirkland said. “So that means the best evidence now is a 3-billion-year-old impact, and that by far is the oldest impact crater on the planet.”

For Cavosie, the most urgent relief is that the age has moved away from the earlier highball estimate. He welcomed the fact that the crater’s age has been revised significantly, but he still believes Kirkland’s team is overestimating how far back the impact goes.

“While I’m relieved these authors have backed off their 2025 ‘3.5-billion-year impact’ hypothesis, I don’t think they’ve presented a compelling case for a [3.02-billion-year] impact either,” Cavosie said. “The slow march of science towards the truth thus continues.”

Cavosie points to what he sees as shatter cones in younger rocks that date to 2.77 billion years old. If those features really are that young, he argues, the impact must have happened after that date.

Alec Brenner at Yale University—who was also part of the group that critiqued the original study—made a similar argument. Brenner agreed with Cavosie that the rocks must be younger than 2.77 billion years. He said the new study dismisses the observation by arguing that these rocks “have not been dated. ” but that the cones are “straightforwardly correlated to nearby rocks that have been dated.”.

Kirkland counters with a key methodological difference: whether the age depends on long-distance correlation of undated rocks or on direct dating of minerals inside the shocked material.

“The younger age argument still depends on long-distance correlation of undated rocks. largely from satellite-based mapping rather than direct geochemistry or geochronology. ” Kirkland said. “We now have two mineral clocks from the impact rocks themselves giving the same age. That is why direct dating matters.”.

The debate. for now. is tightly focused on what happens inside the rock during a shock event—and whether those minerals preserve the clock that researchers need. In a field where Earth’s oldest events are measured in billions of years. the difference between 3.02 and 2.77 billion years is not a rounding error. It is the line between calling the North Pole Dome crater the oldest impact crater on the planet—and calling that claim premature.

North Pole Dome crater Miralga impact structure shatter cones asteroid impact Curtin University Chris Kirkland Aaron Cavosie uranium-lead dating zircons apatite Earth’s oldest impact crater Archaean aeon