Geologists have discovered the earliest evidence of a meteoroid collision with Earth: tiny fragments of melted rock that showered down on our planet 3.48 billion years ago.
, the scientists concluded that the spherules, which they drilled up from a group of volcanic and sedimentary rocks called the Dresser Formation of the Pilbara Craton in Western Australia, are"the oldest evidence of a potential bolide impact in the geologic record ofUntil now, the oldest evidence of meteoroid impacts were 3.47 billion-year-old spherules, also from Pilbara Craton, and 3.45 billion-year-old fragments found in Kaapvaal Craton, in South Africa.
"This new research documents ejecta in slightly older rocks, which have an age of 3.48 billion years old ," Chris Yakymchuk, a geologist at the University of Waterloo in Canada who was not involved in the research, told Space.com's sister publication Live Science in an email. The results appear robust, he said, but access to the entire dataset would be necessary to confirm their significance.
The scientists discovered the spherules in 2019 in cores of sedimentary rock and dated them using isotopes, versions of the same chemical element that have different masses due to the numbers of neutrons in their nuclei."This is a robust and reliable dating technique," Yakymchuk said."We have a good idea of their age based on isotope dating of the mineral zircon."
The team concluded that the spherules were almost certainly of alien origin due to their chemical composition. They detected platinum group elements like iridium in much higher amounts than normally found in terrestrial rocks, as well as minerals called nickel-chromium spinels and isotopes of osmium within the range typical for most meteorites.
Evidence of meteoroid collisions with Earth is difficult to find and often controversial. Plate tectonics and erosion wear down the planet's crust and can erase traces of ancient strikes, such as impact craters. A
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