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Getty Images<\/span><\/div>\n<\/div>\n<\/figure>\nThe huge asteroid that hit Earth and wiped out the dinosaurs 66 million years ago was not alone, scientists have confirmed.<\/p>\n
A second, smaller space rock smashed into the sea off the coast of West Africa creating a large crater during the same era.<\/p>\n
It would have been a \u201ccatastrophic event\u201d, the scientists say, causing a tsunami at least 800m high to tear across the Atlantic ocean.<\/p>\n
Dr Uisdean Nicholson from Heriot-Watt University first found the Nadir crater in 2022, but a cloud of uncertainty hung over how it was really formed.<\/p>\n<\/div>\n
Now Dr Nicholson and his colleagues are sure that the 9km depression was caused by an asteroid hurtling into the seabed.<\/p>\n
They cannot date the event exactly, or say whether it came before or after the asteroid which left the 180km-wide Chicxulub crater in Mexico. That one ended the reign of the dinosaurs. <\/p>\n
But they say the smaller rock also came at the end of the Cretaceous period when they went extinct. As it crashed into Earth’s atmosphere, it would have formed a fireball.<\/p>\n
\u201cImagine the asteroid was hitting Glasgow and you\u2019re in Edinburgh, around 50 km away. The fireball would be about 24 times the size of the Sun in the sky – enough to set trees and plants on fire in Edinburgh,\u201d Dr Nicholson says.<\/p>\n<\/div>\n An extremely loud air blast would have followed, before seismic shaking about the size of a magnitude 7 earthquake.<\/p>\n Huge amounts of water probably left the seabed, and later cascaded back down creating unique imprints on the floor.<\/p>\n It is unusual for such large asteroids to crash out of our solar system on course for our planet within a short time of each other.<\/p>\n But the researchers don\u2019t know why two hit Earth close together.<\/p>\n<\/div>\n The asteroid that created the Nadir crater measured around 450-500m wide, and scientists think it hit Earth at about 72,000km\/h.<\/p>\n The nearest humans have come to this scale of event was the Tunguska event in 1908 when a 50-metre asteroid exploded in the skies above Siberia.<\/p>\n The Nadir asteroid was about the size of Bennu, which is currently the most hazardous object orbiting near Earth.<\/p>\n Scientists say the most probable date that Bennu could hit Earth is 24 September 2182, according to Nasa. But it is still just a probability of 1 in 2,700.<\/p>\n There has never been an asteroid impact of this size in human history, and scientists normally have to study eroded craters on Earth or images of craters on other planets.<\/p>\n To further understand the Nadir crater, Dr Nicholson and team analysed high-resolution 3D data from a geophysical company called TGS.<\/p>\n Most craters are eroded but this one was well-preserved, meaning the scientists could look further into the rock levels.<\/p>\n \u201cThis is the first time that we’ve ever been able to see inside an impact crater like this – it\u2019s really exciting,\u201d says Dr Nicholson, adding there are just 20 marine craters in the world but none have been studied in detail like this.<\/p>\n The findings are reported in Nature Communications Earth & Environment.<\/p>\n<\/div>\n<\/div>\n![](\"https:\/\/www.bbc.com\/bbcx\/grey-placeholder.png\")
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