A new date for an ancient scar
A team studying the North Pole Dome impact structure in Western Australia says it has found fresh evidence that the crater was formed about 3.02 billion years ago. If that age holds up, the site would rank as the oldest known impact structure on Earth. But the finding does not settle the question. Other researchers have already challenged earlier age estimates for the crater, and the new result is likely to intensify rather than end the debate.
The structure, also called the Miralga impact structure, was first described by researchers led by Curtin University’s Chris Kirkland in 2025. The team estimated that the crater could be as much as 100 kilometers wide. The site drew immediate attention because it appears to preserve shatter cones, cone-shaped features that form only under the extreme pressures of a high-energy impact such as an asteroid strike. Those features are among the strongest field indicators that a crater was produced by an extraterrestrial collision rather than by volcanism or tectonic activity.
What has remained uncertain is not whether an impact happened, but when it happened. That timing matters because the age would determine whether North Pole Dome rewrites the history of known asteroid impacts on the early Earth.
Why the age matters
The current benchmark for the oldest reliably dated asteroid-impact crater is Yarrabubba, also in Western Australia. A much older confirmed date for North Pole Dome would push the record back by more than a billion years and place the event in the Archaean aeon, a period when Earth’s surface and atmosphere were radically different from those of today.
That makes the question scientifically important beyond the record-book aspect. Ancient impacts are tied to how the early crust evolved, how hydrothermal systems formed, and how surface environments may have been altered by repeated bombardment. A dated impact structure from around 3 billion years ago would offer rare direct evidence from a part of Earth history that is only patchily preserved in the geologic record.
The original estimate for North Pole Dome was even older. Kirkland’s group had proposed an age of about 3.47 billion years based on correlations between the impact-bearing rock layer and dated layers above and below it. That interpretation, however, did not come from directly dating the impacted rock itself. Critics argued that indirect correlations were not enough to support so extraordinary a claim.
What the new study says
According to the new work described in the source report, the researchers moved beyond stratigraphic correlation and analyzed minerals from the crater rocks themselves. Kirkland said the team examined minerals that directly responded to the impact event rather than relying only on surrounding rock layers.
The approach focused on two mineral systems. First, the researchers dated zircons found within rocks containing shatter cones. Those zircons are said to have recrystallized under the force of the impact. Second, they dated apatite associated with the hydrothermal system generated by the heat of the collision. In both cases, the uranium-lead dating results reportedly clustered around 3.02 billion years.
That convergence is the core of the new argument. If both the impact-affected zircon and the heat-related apatite point to the same general period, the researchers contend that they are seeing the direct imprint of the collision and its aftermath. In other words, the new date is presented not as a rough contextual estimate but as an age recorded in minerals altered by the event itself.
The result is younger than the team’s earlier 3.47 billion-year proposal, but it would still make North Pole Dome older than Yarrabubba and potentially the oldest impact crater yet identified on Earth.
Why the finding remains disputed
The scientific disagreement did not start with this latest result. Another team that includes Curtin University researcher Aaron Cavosie had already argued that the impact could not be older than 2.77 billion years, based on its own analysis of rocks from the area. That critique directly challenged the earlier 3.47 billion-year interpretation and raised a broader concern: whether the mineral ages being recovered truly date the impact, or instead reflect later geological processes overprinting the rocks.
That issue is common in deep-time geology. Extremely old terrains have often been reheated, fractured, chemically altered, and deformed multiple times. Minerals can preserve pieces of those events, and separating one event from another is technically difficult. A date measured in or near an impact structure is not automatically the age of the impact itself. Researchers have to show that the dated minerals were reset or formed because of the collision, not because of some later thermal or hydrothermal episode.
The new work attempts to answer that problem by focusing on minerals inside shatter-cone-bearing rocks and in the hydrothermal system linked to the impact. Even so, the broader community will likely want to see how robust those links are, how the grains were selected, and whether alternative explanations can be ruled out.
What comes next
For now, North Pole Dome stands as a candidate for the oldest known impact structure, not a settled champion. The new 3.02 billion-year age strengthens the case that the site records a very ancient collision, but the dispute over interpretation remains part of the story.
That is not unusual in high-stakes geochronology. Big revisions to Earth history rarely turn on a single field observation or one dating method alone. They become accepted through repetition, cross-checking, and sustained scrutiny from researchers who may be using different techniques and assumptions.
If follow-up work confirms the new age, North Pole Dome would become a critical site for understanding how asteroid impacts shaped the early planet. If it does not, the structure may still remain important as a rare preserved crater from the deep past, just not the oldest one on record.
Either way, the latest study has accomplished something significant: it has moved the argument from broad geological correlation toward direct mineral evidence from the crater rocks themselves. In a field where the oldest rocks have survived billions of years of change, that shift in method may prove as important as the headline age claim.
This article is based on reporting by New Scientist. Read the original article.
Originally published on newscientist.com
