Oldest meteorite crater found in Australia
Deep Aussie impact.
Despite Earth’s long history of getting smacked by space rocks, evidence of those collisions can be very hard to find; even the largest impact craters vanish over time due to erosion and tectonic activity, taking the best reminders of Earth’s past with them. Now, however, researchers in Western Australia believe they’ve found the single oldest impact crater ever detected, dating to roughly 2.2 billion years ago.
In a recent study, published in the journal Nature Communications, researchers studied a 70-kilometre impact site in the Australian Outback known as Yarrabubba. Today all that’s visible of the once-enormous crater is a small red hill at the area’s centre, known as Barlangi Hill. According to the researchers, the minerals inside that hill hold valuable information about the impact’s age.
“[Barlangi Hill] has been interpreted as an impact-generated melt rock,” the researchers wrote. That means its rocky innards hold mineral grains that were smashed, melted and eventually recrystallised by the ancient impact. Narrowing down the ages of those crystal inclusions, known as neoblasts, could reveal the date of the impact itself.
To do that, the study authors looked for neoblasts in a sample of grains containing two minerals, monazite and zircon, collected from Barlangi. Using a method called uranium-lead dating, which can reveal a mineral’s age based on how many uranium atoms have decayed into lead, the team determined that the crater was formed roughly 2.229 billion years ago, making it 200 million years older than any other known crater on Earth.