Dinosaurs were wiped out by an asteroid the size of the Isle of Wight that hit the Earth with the explosive power of a billion atom bombs, scientists have concluded.
A new report from 41 international experts discounts an alternative theory that volcanic eruptions ended the reptiles' 160 million-year reign.
The scientists reviewed 20 years' worth of evidence in search of a definitive answer to the mystery of what happened to life on Earth around 65 million years ago.
More than half of all species on the planet, including the dinosaurs, flying pterosaurs, and large marine reptiles, vanished in the Cretaceous-Tertiary (KT) mass-extinction.
The leading theory has been a large asteroid impact off the coast of Mexico. But some scientists have argued that a series of volcanic super-eruptions in India may have really been to blame for the dinosaurs' demise. The eruptions spewed 1,100,000 cubic kilometres of lava across the Deccan Traps - a large volcanic region of west-central India - over a period of 1.5 million years.
It has been claimed that volcanic gas and debris could have led to atmospheric cooling and acid rain on a global scale. But the new review has come out strongly in favour of the extinction being caused by a nuclear-scale asteroid impact.
The giant space rock, measuring around 15 kilometres across, slammed into the Earth at Chicxulub, off the Yucatan peninsular.
Dr Gareth Collins, one of the scientists from the Department of Earth Science and Engineering at Imperial College London, said: "The asteroid was about the size of the Isle of Wight and hit Earth 20 times faster than a speeding bullet. The explosion of hot rock and gas would have looked like a huge ball of fire on the horizon, grilling any living creature in the immediate vicinity that couldn't find shelter.
"Ironically, while this hellish day signalled the end of the 160 million year reign of the dinosaurs, it turned out to be a great day for mammals, who had lived in the shadow of the dinosaurs prior to this event. The KT extinction was a pivotal moment in Earth's history, which ultimately paved the way for humans to become the dominant species on Earth."
The asteroid hit with a force one billion times greater than the power of the atom bomb dropped on Hiroshima at the end of the Second World War. It would have caused fire storms and earthquakes, and blasted material high into the atmosphere, blocking out the Sun to trigger a "nuclear winter" that would have killed off much of the Earth's life in a matter of days.