Evidence of the United Kingdom’s oldest asteroid hit has been found in the northwest of Scotland, with researchers saying that the one-kilometre-wide rock likely landed around 1.2 billion years ago.
In a new publication in the Journal of the Geological Society, scientists at Oxford University and University of Aberdeen describe how the investigation began with the finding of “strange green blobs” in the rock formation called the Stac Fada member in the Scottish Highlands. While initially thought to be the leftovers of volcanic eruptions, the materials were found to contain quartz crystals most likely formed through the impact of a giant meteorite thought to have crashed into the earth at a speed of about 65,000 km per hour and creating a crater about 13 to 14 km wide and three km deep.
Researchers were then tasked with figuring out just where the meteorite hit. Using three different techniques to model the scatter of dust and debris that would have been raised through the collision, they pinpointed the location to Enard Bay in the Minch Basin between Scotland and the Outer Hebrides.
“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,” said study author and Oxford geochemist Ken Amor to the BBC . “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,” Amor said.
Meteorite strikes of that magnitude only occur once every 100,000 years, with the Enard Bay strike coming at a time when life on Planet Earth was still restricted to the oceans. But the underwater crater formed by the event has long since been covered over by sediment, says Amor.
“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,” says Armor. “It was purely by chance this one landed in an ancient rift valley where fresh sediment quickly covered the debris to preserve it.”