SYDNEY � Australian scientists have discovered a crater deep beneath the Timor Sea made during a heavy meteor storm which may have altered the Earth's climate, the lead researcher said Thursday.

Australian National University archaeologist Andrew Glikson said seismic activity led experts to the Mount Ashmore 1B site, and a study of fragments showed a large meteorite hit just before the Earth's temperatures plunged.

"The identification of microstructural and chemical features in drill fragments taken from the Mount Ashmore drill hole revealed evidence of a significant impact," Glikson said, adding it was at least 50 kilometres (31 miles) wide and about 35 million years old.

A meteorite 100 kilometres wide hit Siberia at the same time, along with an 85 km one in Chesapeake Bay, off the US coast of Virginia, followed by a large field of molten rock fragments over northeast America, he said.

"This defined a major impact cluster across the planet," said Glikson.

Glikson said the findings, published in the latest issue of the Australian Journal of Earth Sciences, could suggest a link between the impacts and a sharp fall in global temperatures which preceded the formation of the Antarctic ice sheet.

"This impact cluster hit Earth about one million years before the Drake Passage, the ocean gap between Antarctica and South America, opened up ... (which) 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," he added.