In 2008, a team of researchers discovered signs of a huge asteroid collision in the Stac Fada deposit on the coast of the Scottish Highlands. The rocks there contained high levels of chemicals found in meteorites, along with quartz crystals that appeared to have been subjected to intense pressures, leading the scientists to conclude that they had found the outer debris of an ancient extraterrestrial impact. And now, as Passant Rabie reports for Space, researchers believe the have pinpointed the spot where the asteroid hit.
Writing in the Journal of the Geological Society, scientists from the University of Oxford and the University of Exeter write that the impact crater may lie between nine and 12 miles off the coast, in a strait known as the Minch, which separates the mainland from the Outer Hebrides. Today, the spot is buried beneath water and rocks, rendering it inaccessible. So the team plotted the possible center of the crater by studying factors like the alignment of magnetic particles and the distribution of debris that was thrown outwards at the time of the collision.
“If you imagine debris flowing out in a big cloud across the landscape, hugging the ground, eventually that material slows down and comes to rest,” lead study author Kenneth Amor tells the BBC’s Jonathan Amos. “But it’s the stuff out in front that stops first while the stuff behind is still pushing forward and it overlaps what’s in front.
“That’s what we see and it gives us a strong directional indicator that we can trace backwards.”
The meteorite, which stretched between 0.6 and 1.2 miles wide, is believed to have slammed into Earth 1.2 billion years ago, a time when most life on the planet was confined to the oceans and the region now known as Scotland was a semi-arid environment located near the equator. The study authors estimate that the crater resulting from the impact spans between approximately 8 to 8.7 miles in length, with a depth of around 1.9 miles. It is, according to Oxford, “the biggest ever meteorite collision” discovered in the U.K.
Experts think that meteorite strikes were relatively common billions of years ago, as Earth and other planets were pelted with debris left over from the formation of the solar system. But Amor says the new research marks an “exciting discovery,” because impact craters typically erode over time.
“It was purely by chance,” Amor notes, “[that] this one landed in an ancient rift valley where fresh sediment quickly covered the debris to preserve it.”
Now that scientists have honed in on the crater’s possible location, they hope to conduct targeted, 3D geophysical surveys of the Minch Basin. Because such investigations will have to happen offshore, they won’t come cheap. But high-resolution surveys could help the research team get a better sense of the dimensions of the crater, and might even have important implications for other celestial bodies.
“Impact craters on Earth are exceedingly rare,” Amor tells Gizmodo’s George Dvorsky. “The better we can understand how they formed the better we can understand observations on the rocky planets and moons of the solar system.”