Huge crater in Australia may be the oldest impact structure on Earth
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- Chris Kirkland at Curtin University first proposed in 2025 that the North Pole Dome crater (Miralga impact structure) could be up to 100 km wide and 3.47 billion years old, based on correlations with surrounding dated rock layers.
- Kirkland's team has now directly dated recrystallized zircons within shatter cones and apatite from the impact's hydrothermal system using uranium-lead decay, with both mineral clocks returning ages of approximately 3.02 billion years.
- If the date holds, the crater would be the oldest impact structure on Earth—more than 1.2 billion years older than the Yarrabubba crater and the only known impact from the Archaean aeon, when the planet was a global water world.
- Aaron Cavosie, also at Curtin, argues the impact must be younger than 2.77 billion years, pointing to shatter cones that appear in rocks of that age in the area.
- Alec Brenner at Yale agrees with Cavosie, saying the supposedly younger rocks are "straightforwardly correlated to nearby rocks that have been dated."
- Kirkland counters that his new date rests on direct geochemistry of impact-affected minerals, while the critics' younger estimate relies on "long-distance correlation of undated rocks, largely from satellite-based mapping."
Why it matters: If the 3.02-billion-year date survives continued challenge from Cavosie and Brenner, Earth's oldest confirmed impact crater moves back by more than a billion years and yields the only Archaean-era impact on record, reshaping models of early Earth bombardment history during a time when the entire planet was covered by an inhospitable global ocean.
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