Study: Dinosaurs Died Within Hours After Asteroid Hit Earth 65 Million Years AgoAccording to new research led by a University of Colorado at Boulder geophysicist, a giant asteroid that hit the coast of Mexico 65 million years ago probably incinerated all the large dinosaurs that were alive at the time in only a few hours, and only those organisms already sheltered in burrows or in water were left alive... The "heat pulse" caused by re-entering ejected matter would have reached around the globe, igniting fires and burning up all terrestrial organisms not sheltered in burrows or in water, he said... "The kinetic energy of the ejected matter would have dissipated as heat in the upper atmosphere during re-entry, enough heat to make the normally blue sky turn red-hot for hours," said Robertson. Scientists have speculated for more than a decade that the entire surface of the Earth below would have been baked by the equivalent of a global oven set on broil.
CU-Boulder
May 24, 2004
'Quick' demise for the dinosaursSujoy Mukhopadhyay and colleagues studied sedimentary rocks that mark the so-called K-T boundary, the line of separation between the zones of geological time referred to as the Cretaceous period and the Tertiary sub-era. It is at this K-T boundary, timed at about 65 million years ago, that 70% of all life, including the dinosaurs, suddenly disappears from the fossil record... Mukhopadhyay's US-Italian team believe they can now measure the length of this dark period in Earth history. They analysed the amount of helium-3 in the rocks of the K-T boundary. Levels of this type, or isotope, of the element reflect the amount of interplanetary dust that settles on Earth and, properly calibrated, can be used as a tool to time the rate at which rocks are laid down... The research suggests the K-T boundary was deposited in about 10,000 years. He said the short period lent support to the theory that the dinosaurs were wiped out in a sudden, catastrophic event such as the impact of an extraterrestrial body. The constant rate of accumulation of helium-3 also indicates that the impactor was not part of a comet shower or bombardment. "Comets are dusty objects and if you have several comets coming into the inner Solar System, you will increase the dust flux to the Earth," Mukhopadhyay said. "If you increase the dust flux, you increase the helium-3 flux. And so if you don't see an increase in the helium-3 in these sediments, it rules out a large number of comets coming in."
by BBC News Online's Jonathan Amos
Thursday, March 8, 2001