A recent study suggests the North Pole Dome crater in Western Australia formed from an asteroid strike about 3 billion years ago, potentially making it the oldest known impact structure on Earth. However, other scientists have challenged this proposed age.
The North Pole Dome crater, also called the Miralga impact structure, was initially identified in 2025 by Chris Kirkland of Curtin University and his team. They estimated its width could reach up to 100 kilometres.
The researchers identified a rock layer with cone-shaped shatter cones, structures created only by intense impacts like asteroid collisions. Although their first analysis did not date the rock directly, correlations with surrounding dated layers led them to propose an age of 3.47 billion years.
This would exceed the age of the Yarrabubba crater by more than 1.2 billion years, currently considered the oldest reliably dated impact site. It would also represent the sole known impact from the Archaean period, when Earth was largely an inhospitable water-covered world.
A separate group led by Aaron Cavosie, also from Curtin University, disputed the 3.47-billion-year estimate. Their analysis indicated the impact occurred no earlier than 2.77 billion years ago.
Kirkland’s team has since dated recrystallised minerals containing shatter cones at the site. They examined zircons that reformed due to the impact’s force and measured the decay of uranium to lead, obtaining an age of roughly 3.02 billion years. Apatite minerals formed in the impact’s hydrothermal system yielded the same date.
Kirkland argues that no other geological processes, such as mountain building, account for the observed mineral changes around that time. Cavosie acknowledges the revised age but maintains the impact must postdate 2.77 billion years based on shatter cones in younger rocks. Alec Brenner of Yale University supports this view, noting correlations with dated nearby formations.
Kirkland emphasises that direct dating of minerals within the shocked rocks provides stronger evidence than distant correlations, supporting a 3-billion-year-old impact as the oldest known on the planet.
