Washington, Jan 24 : Three-dimensional seismic images of a crater believed to be formed when an asteroid stuck the Earth 65 million years ago, causing the extinction of dinosaurs, suggest that the object landed in deeper water, leading to a bigger splash than previously assumed.
The 3D images are of the Chicxulub crater, a mostly submerged and buried impact crater on the Mexico coast, which was formed when an asteroid struck on the coast of the Yucatan Peninsula.
Most scientists agree the impact played a major role in the "KT Extinction Event" that caused the extinction of most life on Earth, including the dinosaurs.
According to Sean Gulick, a research scientist at the Institute for Geophysics at The University of Texas and principal investigator for the project, the new images reveal the asteroid landed in deeper water than previously assumed and therefore released about 6.5 times more water vapor into the atmosphere.
The impact site also contained sulfur-rich sediments called evaporites, which would have reacted with water vapor to produce sulfate aerosols.
According to Gulick, an increase in the atmospheric concentration of the compounds could have made the impact deadlier in two ways: by altering climate and by generating acid rain.
Though earlier studies had suggested both effects might result from the impact, it was to a lesser degree.
"The greater amount of water vapor and consequent potential increase in sulfate aerosols needs to be taken into account for models of extinction mechanisms," said Gulick.
An increase in acid rain might help explain why reef and surface dwelling ocean creatures were affected along with large vertebrates on land and in the sea. As it fell on the water, acid rain could have turned the oceans more acidic. There is some evidence that marine organisms more resistant to a range of pH survived while those more sensitive did not.
According to the report, the mass extinction event was probably not caused by just one mechanism, but rather a combination of environmental changes acting on different time scales, in different locations.
For example, many large land animals might have been baked to death within hours or days of the impact as ejected material fell from the sky, heating the atmosphere and setting off firestorms.
More gradual changes in climate and acidity might have had a larger impact in the oceans.