Tue, Jun 11, 2019 - Page 6 News List

Ancient asteroid crater located off coast of Scotland

DEEP IMPACT:A space object about 1.6km wide believed to have crashed into Earth about 1.2 billion years ago created a 19km-wide crater, a study shows

The Guardian

The location of an ancient impact crater made by the biggest asteroid ever to hit Britain has been traced to a spot under the sea between mainland Scotland and the Outer Hebrides.

Researchers at Oxford and Aberdeen universities found signs of the violent collision in Scotland on a field trip in 2008, but have only now pinpointed where the asteroid came down.

Tests on rocks near Ullapool in northwest Scotland revealed that an object about 1.6km wide had crashed into a spot in the Minch, a strait that separates the mainland and northern Inner Hebrides from Lewis and Harris, about 10km west of the village of Lochinver.

The 61,115kph collision, which thumped a 19km-wide crater into the ground, happened 1.2 billion 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 200m-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).

Previous researchers speculated that the distinctive red sandstone had come from a volcano, but Amor realized that “strange green blobs” in the rock resembled features of an impact crater that underlies the town of Nordlingen near the Danube in western Bavaria.

Amor took samples of the SFM back to Oxford and found strong evidence of an asteroid strike: quartz crystals that had been deformed by the shock of an impact.

He also found high levels of platinum and palladium, metals that are enriched in meteorites, the name given to space rocks that survive their fiery passage through the atmosphere to reach Earth’s surface.

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 backward to the point of impact.

Details of the work appear in the Journal of the Geological Society.

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