The world’s oldest asteroid strike in Western Australia may have triggered a global thaw

Reported today on The Guardian For the full article visit: https://www.theguardian.com/science/2020/jan/22/the-worlds-oldest-asteroid-strike-in-western-australia-may-have-triggered-a-global-thaw The world's oldest asteroid strike in Western Australia may have triggered a global thaw A new study showing the 70km-wide Yarrabubba crater dates impact to 2.29bn years ago The world's oldest remaining asteroid crater is at a place called Yarrabubba, south-east of the town of Meekatharra in Western Australia. Our new study puts a precise age on the cataclysmic impact – showing Yarrabubba is the oldest known crater and dating it at the right time to trigger the end of an ancient glacial period and the warming of the entire planet. What we found at Yarrabubba Yarrrabubba holds the eroded remnants of a crater 70km wide that was first described in 2003, based on minerals at the site that showed unique signs of impact. But its true age was not known. We studied tiny "impact-shocked" crystals found at the site, which show the crater formed 2.229bn years ago (give or take five million years). This new, precise date establishes Yarrabubba as the oldest recognised impact structure on Earth. It is some 200m years older than the next oldest, the Vredefort impact in South Africa. More intriguing, the geological record shows the Earth had glacial ice before the time of the impact – but afterwards, ice disappeared for hundreds of millions of years. Was the Yarrabubba impact a trigger for global climate change? How to date an asteroid hit An asteroid strike is one of the most violent geologic events. In an instant, Earth's crust is squeezed to unimaginable pressures, before exploding and ejecting carnage across the landscape. Large impacts leave behind scars the size of a small city. The basin formed by an impact will partly fill with molten and pulverised rock from the Earth and from the asteroid itself. The edge of the crater forms a r