Australian National University scientists have discovered a crater of at least 50 kilometers in diameter under the Timor Sea near to Australia, created by a giant asteroid which collided with the Earth some 35 million years ago, the university website said.
"The minimum size of the Mount Ashmore dome, which represents elastic rebound doming of the Earth crust triggered by the impact, is 50 kilometres at the base, but the full size of the impact crater - not yet defined - may be significantly larger," said Dr. Andrew Glikson of the Planetary Science Institute and the School of Archaeology and Anthropology at ANU.
The Australian Journal of Earth Sciences said the period 35 million years ago was considered a time of heavy extraterrestrial bombardment and the university said the findings could suggest a connection between the bombardment and the sharp fall in global temperatures that lead to the formation of the Antarctic ice sheet.
"Round the same time as the Mount Ashmore impact, a 100-kilometer-wide asteroid impact structure formed in Siberia, and another measuring 85 km in diameter in Chesapeake Bay, off Virginia, in the United States," Glikson said. "Likewise a large field of tektites, molten rock fragments splashed by impact, fell over northeast America. This defined a major impact cluster across the planet."
"This impact cluster hit Earth about 1 million years before the Drake Passage, the ocean gap between Antarctica and South America, opened up," he said. "The opening of the Drake Passage allowed continuous circulation of the circum-Antarctic ocean current, isolating the Antarctic continent and allowing the onset of its large ice sheet, which acts as a 'thermostat' for the Earth's climate."
MOSCOW, May 20 (RIA Novosti)
