Over the years Earth has been hit by numerous asteroids and comets, all of which have left their mark behind. At present, it's sometimes hard to tell where these ancient impacts occurred, and even harder to determine when they happened.
Now, a team of geologists has confirmed that they've discovered the world's oldest impact crater — by a long shot.
Located in the outback of Western Australia, the Yarrabubba impact crater is 2.2-billion-years-old and is 70-kilometers-wide (43 miles).
The findings were published in the journal Nature Communications on Tuesday.
The crater has been known for 20 years
To be exact, the Yarrabbuba crater is 2.229-billion-years-old. This makes it 210 million years older than the 200-kilometer-wide (120 miles) Vredefort Dome in South Africa, and 380-million-years older than the 180-kilometer-wide (112 miles) Sudbury impact structure in Ontario, Canada.
The Yarrabubba crater was formed roughly 2.2 billion years ago, which makes it about 200 million years older than any other known crater. https://t.co/GHUbannvKq— VICE (@VICE) January 22, 2020
Timmons Erickson from the NASA Johnson Space Center and the Curtin University in Australia, and also the first author of the study, explained that the asteroid that created the Yarrabubba crater would have hit a massive ice sheet that was there at the time.
The Yarrabubba crater was already known to scientists, however, its age hadn't yet been determined. Because of its old age, a steady accumulation of geological matters covered the crater, and the fact that it's located in an extremely remote area meant that the crater was mostly left alone until now.
“It’s kind of like cleaning house… #recrystallisation is a bond-breaking process that kicks out the pre-existing lead and thus resets the clock.” - Dr. @AaronCavosie on how researchers calculated the age of the #YarrabubbaCrater. Read via @nytimes: https://t.co/tWiVNC1HOj— Curtin University (@CurtinUni) January 22, 2020
In order to date the structure, Erickson and his colleagues analyzed shocked minerals from the base of the crater. They specifically focused on zircon and monazite that had been crystallized by the shock of the impact — hence the term "shocked minerals."
Erickson explained that "Because their crystal structure can incorporate uranium—but not lead—when they crystallize, and uranium will decay to lead at a known rate, we can use the ratios of the uranium and lead isotopes to determine their age."
This is how the team discovered the crater's age.
2.229 billion years = the age of the Yarrabubba meteor crater ☄️ in Australia, making it the oldest currently known! A team led by a @NASA_Johnson scientist determined the age by searching for rocks that showed signs of being subjected to a meteor strike: https://t.co/EiK7pUO3ki pic.twitter.com/wgOJvOTYqa— NASA (@NASA) January 21, 2020