World's Oldest Known Impact Crater

The first author of the new study, Timmons Erickson from NASA Johnson Space Centre and Curtin University in Australia, along with his colleagues, also presented evidence suggesting the 7-kilometre-wide asteroid that formed the Yarrabubba crater hit a massive ice sheet, sending tremendous amounts of water vapour into the atmosphere and potentially warming the climate around the globe.
The Yarrabubba crater was previously known to scientists, but the structure had not been dated with confidence due to several factors, such as its extreme age, the steady accumulation of overlaying geological materials, and its remote location in western Australia. Previous dating efforts were wide ranging, extending from 1.1 billion to 2.6 billion years old
To date the structure, Erickson and his colleagues analysed shocked minerals pulled from the base of the heavily eroded crater. Specifically, they looked at zircon and monazite that were recrystallised by the shock of the impact, hence the term “shocked minerals.”
“Zircon and monazite are two of the most commonly used uranium lead geologic clocks,” Erickson told Gizmodo in an email. “Because their crystal structure can incorporate uranium—but not lead—when they crystallise, 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.”