Scientists find ‘smoking gun’ evidence of world’s oldest meteorite strike in Western Australia

The well-preserved rock formations in the North Pole Dome crater in the Pilbara region of Western Australia offer ‘a rare glimpse of the violent processes that shaped the early Earth’. Photograph: Curtin University View image in fullscreen The well-preserved rock formations in the North Pole Dome crater in the Pilbara region of Western Australia offer ‘a rare glimpse of the violent processes that shaped the early Earth’. Photograph: Curtin University Scientists find ‘smoking gun’ evidence of world’s oldest meteorite strike in Western Australia Curtin University researchers use innovative techniques to date three-billion-year-old impact crater in Pilbara region A meteorite that struck Earth three billion years ago left behind a “smoking gun” – evidence of the world’s oldest impact crater in a remote part of Australia. Ancient rocks in Western Australia’s Pilbara region record the event, which occurred during the Archean eon, a period 4 to 2.5 billion years ago, when tectonic plates were beginning to form and early life emerging. To establish a precise date, Curtin University scientists analysed the age of rare geological features, called shatter cones, in an area known as the North Pole Dome crater, publishing their findings in Geology journal. Prof Chris Kirkland, a geologist from Curtin’s Timescales of Minerals Systems Group and lead author of the paper, said the well-preserved rock formations were an extremely rare and globally significant archive of geological time, offering “a rare glimpse of the violent processes that shaped the early Earth”. The world’s oldest asteroid strike in Western Australia may have triggered a global thaw Read more “There’s very few places that are these deep time capsules that let us peer into the formative processes on our planet. That’s why they’re quite special.” The findings revealed the North Pole Dome crater to be older than Yarrabubba , another crater in Western Australia, previously considered the oldest at 2.2 billion years old. View image in fullscreen Rare geological features were found in the Pilbara. Photograph: Chris Kirkland/Curtin University The researchers used two separate methods to determine when the meteorite strike occurred. First they analysed the age of “little lightning bolts” of zircon embedded in the basalt rock. Tiny zircon grains were recrystallised in the intense heat of the meteorite strike, forking into unusual skeletal patterns generally only found in impact craters on the moon. The age of these zircon crystals was measured using an Australian-designed instrument called the Sensitive High-Resolution Ion MicroProbe, determining that the shape-changing shock occurred about 3 billion years ago. Separately, scientists analysed the age of apatite – a calcium phosphate mineral which grew in rock fractures created by heat and hot fluids after the impact – with similar conclusions. View image in fullscreen Prof Chris Kirkland, a geologist from Curtin University’s Timescales of Minerals Syste