Oldest Impact Structure on Earth Identified

Zircon grain
An image of a zircon grain showing exceptional recrystallization texture due to the impact. Image credit: Timmons Erickson

A study led by Timmons Erickson of Jacobs/NASA Johnson Space Center has identified Yarrabubba, a 70-kilometer-diameter crater in Western Australia, as the oldest impact structure on Earth. Rock samples from Yarrabubba contain minerals that were recrystallized due to shock from the impact. Radiometric dating was used to determine that the shocked minerals are approximately 2.229 billion years old, which indicates that the Yarrabubba crater formed more than 200 million years before the oldest previously identified crater. This age coincides with the depositional ages of widespread glacial deposits, which form when glaciers melt. Simulations conducted by Erickson and colleagues show that a Yarrabubba-sized impact into a glacier would have released enough water vapor to alter the global climate early in the Proterozoic era. READ MORE