Interestingly, this article appeared today -
Earths Oldest Asteroid Impact Found in Australia
Researchers reported on Tuesday in Nature Communications that they have pinpointed it, in Western Australia. It was caused by an impact more than 2.2 billion years ago.
The Yarrabubba impact structure, about a days drive northeast of Perth, isnt much to look at today. The original crater, believed to have been roughly 40 miles in diameter, is long gone.
Theres no topography that rises up, said Aaron Cavosie, a planetary scientist at Curtin University in Perth and a member of the research team.
Thats because the combined effects of wind, rain, glaciation and plate tectonics have scoured several miles off the surface of the planet, effectively erasing the crater. The extent of erosion suggests that the impact structure is very, very old.
In 2014, Dr. Erickson collected roughly 200 pounds of granitic rocks from Yarrabubba. Back in the laboratory, he and his colleagues placed the rocks in water and added 120,000 volts of electricity. That jolt broke the rocks into sand-size grains. The scientists were looking for grains of zircon and monazite, tough minerals that survive for billions of years and, crucially, incorporate uranium and thorium atoms into their crystalline structure.
Uranium and thorium decay, in a steady dribble over billions of years, into lead. But the searing temperatures of an impact thousands of degrees Fahrenheit cause zircon and monazite to recrystallize, a process that drives out lead.
https://www.msn.com/en-au/news/tech...found-in-australia/ar-BBZbxCQ?ocid=spartanntp