LONDON, June 10 (Xinhua) -- Scientists at the University of Oxford said Monday they believe they have discovered the site of the biggest meteorite impact ever to hit the British Isles.
Evidence for the 1.2 billion-year-old meteorite strike was first discovered in 2008 near Ullapool in the north west of Scotland, by scientists from Oxford and Aberdeen Universities.
The thickness and extent of the debris deposit they found suggested the impact crater, made by a meteorite estimated at 1 km wide, was close to the coast, but until now its precise location remained a mystery.
Ken Amor from the Department of Earth Sciences at Oxford University outlined their work in a paper published in Journal of the Geological Society, explaining how they have identified the crater location 15-20 km west of a remote part of the Scottish coastline. It is buried beneath both water and younger rocks in what is known as the Minch Basin.
"The material excavated during a giant meteorite impact is rarely preserved on Earth, because it is rapidly eroded, so this is a really exciting discovery. It was purely by chance this one landed in an ancient rift valley where fresh sediment quickly covered the debris to preserve it," Amor said.
According to him, the next step will be a detailed geophysical survey in the target area of the Minch Basin.
Using a combination of field observations, the distribution of broken rock fragments known as basement clasts and the alignment of magnetic particles, the team was able to gauge the direction the meteorite material took at several locations, and plotted the likely source of the crater.
"It would have been quite a spectacle when this large meteorite struck a barren landscape, spreading dust and rock debris over a wide area," Amor added.
Scientists believe the Earth and other planets may have suffered a higher rate of meteorite impacts in the distant past, as they collided with debris left over from the formation of the early solar system.
"There is a possibility that a similar event will happen in the future given the number of asteroid and comet fragments floating around in the solar system. Much smaller impacts, where the meteorite is only a few meters across are thought to be relatively common perhaps occurring about once every 25 years on average," said the report of Amor and his team, speculating about future strikes, added:
It is thought that collisions with an object about 1 km, as in the case of the Scotland strike, across occur between once every 100,000 years to once every 1 million years -- but estimates vary.
"One of the reasons for this is that our terrestrial record of large impacts is poorly known because craters are obliterated by erosion, burial and plate tectonics," the report said.