Credit: Image design by Tim Warchocki. Images courtesy of NASA (Earth) and Tim Warchocki (asteroid and stars).
Credit: Space Studies Board/National Research Council

 

 

The roughly 44 mile (70 kilometers) in diameter Yarrabubba impact structure in Western Australia has been radiometric age dated to 2.2 billion years old, making it Earth’s oldest recognized asteroid impact structure.

That determination extends the terrestrial cratering record back greater than 200 million years.

Research led by Timmons Erickson from NASA Johnson Space Center and Curtin University in Australia, along with his colleagues, has been published in Nature Communications.

Extraterrestrial bombardment

In an introduction to their research, the team explains that extraterrestrial bombardment flux is speculated to have had major consequences for the development of Earth’s surface environment. “However, the terrestrial impact record is fragmentary, principally due to tectonics and erosion and is progressively erased into the geologic past when, conversely, the bombardment rate was larger than today,” they note.

Map of the Yarrabubba impact structure and sample localities.
Credit: Erickson, et al.

Yarrabubba is a recognized impact structure located within the Murchison Domain of the Archaean granite—greenstone Yilgarn Craton of Western Australia. The research paper notes that no circular crater remains at Yarrabubba; “however, the structure has an elliptical aeromagnetic anomaly consisting of an even, low total magnetic intensity domain.”

The roughly 12 mile (20 kilometer) diameter magnetic anomaly has been interpreted to represent the remnant of the deeply buried central uplift of the structure, which is consistent with an original crater diameter of 44 miles (70 kilometers), they report.

Time of impact

These results establish Yarrabubba as the oldest preserved impact structure on Earth.

Furthermore, Erickson and colleagues suggest the 4.3 mile (7 kilometer) wide asteroid that shaped the Yarrabubba impact site could have been covered by a continental ice sheet at the time of impact.

The slam-bang result was spewing water vapor into the atmosphere and potentially warming Earth’s climate on a global basis. The research team applied numerical simulations to tease out the possible effects that a Yarrabubba-sized impact may have had on climactic conditions.

In their paper, the scientists say the findings “prompts further consideration of the ability of meteorite impacts to trigger climate change.”

To read the full paper – “Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognized meteorite impact structure” – go to:

https://www.nature.com/articles/s41467-019-13985-7#Sec1

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