Australia’s Ancient Giant Crater: Possible Oldest Impact Structure on Earth

According to mineral dating techniques, a colossal crater in Western Australia was formed by an asteroid impact approximately 3 billion years ago. This discovery potentially marks the crater as the oldest impact site on Earth, although its age has been contested by some researchers.

Known as the Arctic Dome Crater or the Miralga Impact Structure, this feature was first documented by Chris Kirkland in 2025 at Curtin University in Perth. His team estimated the crater’s diameter could reach up to 100 kilometers.

Kirkland and his colleagues found a unique layer of rock featuring cone-shaped formations known as shatter cones, typically created by significant impacts like asteroid collisions. While their initial research did not directly date this rock layer, correlations with age-dated rocks in adjacent layers led them to propose an age of 3.47 billion years.

This proposed age surpasses the Yarrababa Crater’s age by over 1.2 billion years, establishing it as the oldest known impact site on Earth. Furthermore, it stands out as the only recognized impact structure from the Archean Era, a time when Earth predominantly existed as a vast ocean.

However, a competing analysis from another research team led by Aaron Cavosie at Curtin University disputes this 3.47 billion-year timeline, claiming that their findings suggest the impact occurred around 2.77 billion years ago.

In a new development, Kirkland and his team assert that they have accurately dated recrystallized minerals, including detrital cones at the crater site. Kirkland states, “We’ve now examined the rock to identify minerals that directly correspond to impacts, rather than relying solely on correlations.”

Utilizing the decay rate of uranium to lead, the researchers dated zircon within the shatter cone formed by the asteroid’s impact. They also dated apatite minerals believed to have developed in hydrothermal systems activated by impact-induced heat.

Both the apatite and zircon dated at approximately 3.02 billion years, providing strong evidence of intense hydrothermal activity in the rock around 3 billion years ago. Kirkland notes, “This indicates that hot water infiltrated the rock long ago, showcasing an unusual heating and recrystallization process.”

Kirkland emphasized that other geological processes, such as mountain building or localized metamorphism, cannot adequately explain the mineral changes observed in the shocked rocks. He states, “The only process strongly correlated with these mineralogical transformations is an impact.” He concludes, “The current evidence strongly supports a 3 billion-year-old impact, potentially marking this as the oldest impact crater on Earth.”

Kavosie appreciates the new adjustments to the crater’s age, arguing, however, that Kirkland’s team continues to overstate its age. “We are grateful that they have revised their previous claim of a 3.5 billion-year impact, but believe they still lack a convincing case for the 3.02 billion-year hypothesis,” he adds, “This is how science progressively edges closer to the truth.”

Kavosie asserts that younger rocks, dating back only 2.77 billion years, exhibit shatter cones, indicating that the impact must have occurred after this point.

Alec Brenner, a Yale University professor and participant in the opposing study, concurs with Cavosie, stating the rocks must be younger than 2.77 billion years. “The new research disregards this finding based on the premise that these rocks are undated, yet they are directly linked to dated nearby rocks,” Brenner explains.

The key distinction, according to Kirkland, is that his team has calculated the ages of minerals within the impacted rock. “The argument for a younger age relies on a long-range correlation of undated rocks through satellite mapping, rather than on direct geochemical evidence or geochronology,” he states. “We now possess two mineral clocks of the same age sourced from the impact rock itself, emphasizing the importance of direct dating.”