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A gigantic meteorite, as much as one kilometer wide, struck off the coast of Scotland and left a crater 15 to 20 kilometers in size.

Luckily, that happened 1.2 billion years old and was only even discovered in 2008 near Ullapool, NW Scotland but now its precise location is no longer a mystery.

In a paper published today in Journal of the Geological Society, a team led by Dr Ken Amor from the Department of Earth Sciences at Oxford University, show how they have identified the crater location buried beneath both water and younger rocks in the Minch Basin.

The material excavated during a giant meteorite impact is rarely preserved on Earth, because it is rapidly eroded. This one landed in an ancient rift valley where fresh sediment quickly covered the debris to preserve it. And the wait to be found again began.

1.2 billion years ago most of life on Earth was still in the oceans and there were no plants on the land. At that time Scotland would have been quite close to the equator and in a semi-arid environment. The landscape would have looked a bit like Mars when it had water at the surface.

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.

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.

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.

Dr Ken Amor said, "The next step will be a detailed geophysical survey in our target area of the Minch Basin."

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