Scientists think the time has come for a full geophysical survey of The Minch, to see if the Scottish strait is hiding an ancient meteorite crater.
The idea that such a structure lies between the Western Isles and mainland Scotland was first raised back in 2008. They found evidence on the Highlands coast for the rocky debris that would have been produced by a giant impact. Now, the team from Oxford and Exeter universities believes it can pinpoint where the space object fell to Earth Tests on rocks near Ullapool in north-west Scotland revealed that an object about a mile wide had crashed into a spot in the Minch, a strait that separates the mainland and northern Inner Hebrides from Lewis and Harris, six miles west of the village of Lochinver. The 38,000 mph collision, which thumped a 12-mile-wide crater into the ground, happened 1.2bn years ago, when most life on Earth was still in the oceans and plants had yet to take root on land. At the time, what is now Scotland was a semi-arid land that lay close to the equator.
“The impact would have sent huge roiling clouds of dust and gas at several hundred degrees in all directions from the impact site,” said Ken Amor, an Oxford researcher who led the latest study. What is left of the crater is submerged in 200-metre-deep water and covered in sediment. The first hints of the impact came more than a decade ago when Amor was helping undergraduates on a geology field trip in the Scottish Highlands. On the last day, the scientists stopped in Stoer, a small village, to inspect an unusual rock formation known as the Stac Fada member (SFM). Having confirmed that an asteroid had come down near Stoer, Amor’s team set about finding the impact crater. Using three independent techniques that drew on the scatter of dust and rocks thrown up by the impact, and the orientation of tiny magnetic grains blasted into the sky, the researchers traced backwards to the point of impact. It is unclear how common such impacts are because craters are wiped from Earth’s surface by erosion, burial and plate tectonics. However, asteroids of the size of the one that hit the Minch are thought to strike between once every 100,000 years and once every 1m years. While the impact would have been dramatic, sending a mushroom cloud and fireball high into the sky, it was minor compared with the spectacular strike in Mexico’s Yucatán peninsula 66m years ago, when a space rock estimated at six to 50 miles wide put an end to the reign of the dinosaurs.