London: A new study has suggested that the asteroid impact that ended the age of dinosaurs 65 million years ago didn't incinerate life on our planet's surface, but just broiled it.
The impact of a 10-kilometre asteroid is blamed for the extinction of the dinosaurs and most other species on the planet.
Early computer models showed that more than half of the debris blasted into space by the impact would fall into the atmosphere within eight hours.
The models predicted the rain of shock-heated debris would radiate heat as intensely as an oven set to "broil" (260 degree Celsius) for at least 20 minutes, and perhaps a couple of hours.
Intense heating for that long would heat wood to its ignition temperature, causing global wildfires.
Yet some species survived, and the global layer of impact debris doesn't contain as much soot as would be expected from burning the world's forests, raising questions about the extent of post-impact wildfires.
According to a report in New Scientist, to explain the discrepancy, Tamara Goldin of the University of Vienna and Jay Melosh of Purdue University in Indiana studied how ejecta falling through the atmosphere might affect heat transfer from the top of the atmosphere to the ground.
Earlier models considered only how atmospheric greenhouse gases would absorb heat.
The study reveals that the first debris to re-enter the atmosphere just a few minutes after the impact helped protect the surface from the debris that followed.
"The actual ejecta themselves were getting in the way of the thermal radiation [in the atmosphere] and shielding the Earth," Goldin told New Scientist.
As a result, the surface felt the full heat from the sky for only a few minutes.
As more particles drifted down, they blocked more and more of the heat from above, preventing the world's forests from igniting.
"With the short pulse (of intense heat), it''s really hard to get ignition" far from the impact site, according to Goldin.
Surface life would have been broiled, but not burnt to a crisp.
Animals that were able to take refuge underground or in the water were likely able to survive the short period of intense heat, explaining why not all life was killed. (ANI)
ANI
First Published: Wednesday, December 09, 2009, 10:30