Diagram shows a 3-D reconstruction of the submerged Shiva crater (~500 km diameter) off the coast of Mumbai in India.
Credit: Sankar Chaterjee
PORTLAND, OREGON: Move aside Chicxulub; an even bigger asteroid impact in the Shiva basin, off the coast of India, may have been ground zero for the dinosaurs, a team of U.S. and Indian scientists say in a guaranteed-to-be-controversial finding.
The huge depression, around 500 km across, appears to be the largest, multi-ringed impact crater in the world, according to Sankar Chatterjee, a geoscientist at Texas Tech University in Lubbock, who presented his research at the Geological Society of America's annual meeting in Portland, USA, today.
Earth's biggest impact
"If we are right, this is the largest crater known on our planet… a bolide of this size, perhaps 40 km in diameter creates its own tectonics," he said. "It may have been the one to kill the dinosaurs."
The Chicxulub crater, an impact site beneath the Yucatan Peninsula in Mexico, was caused by an asteroid 8 to 10 km in diameter. This impactor is commonly believed to have caused a mass extinction at the end of Cretaceous Period, 65 million years ago, which wiped out the dinosaurs.
But now Chatterjee and Naresh Mehrotra, a palaeobotonist at the Birbal Sahni Institute of Palaeobotany in Lucknow, India, believe otherwise.
Shocked quartz
Chatterjee called Shiva a geophysical anomaly, adding that there are telltale markers in and around the crater that suggest the basin could be an impact site.
One is the presence of pseudotachylite, a glassy rock which is formed in the process of impact melting. Another telltale, Chatterjee said, is a high level of iridium, an element found in meteorites, but rare on Earth.
"Around the crater, you have lots of igneous complexes," said Chatterjee. "All are highly rich in iridium. We think these are fluid ejecta formed by impact."
Shocked quartz was also found in the Shiva basin, Chatterjee said, which is common in impact craters and difficult to create by other means. Even volcanoes can't generate the kind of pressure needed to form shocked quartz. This asteroid, according to Chatterjee, appears to have been nearly 40 km in diameter - three times the size of the one believed to have killed the dinosaurs.
be real
Wow!!! Now we have found another crater that "may" be caused by the asteroid or comet or something else that allegedly wiped out the dinosaurs. Why do scientists always say that what they have found is "the one" that caused it? Answer: because they don't really know. Who knows some time next year they may find another one, and guess what, that one will then be "the one" that may have done it.
'scientists'
Yes l guess they have to 'talk-up' their discovery,otherwise people may not hear them and their funding goes down the tube.