Washington, Feb 4 (ANI): A scientist has found evidence which indicates that pieces of a giant asteroid or comet that broke apart over Earth may have crashed off Australia about 1,500 years ago.
Satellite measurements of the Gulf of Carpentaria revealed tiny changes in sea level that are signs of impact craters on the seabed below, according to new research by marine geophysicist Dallas Abbott.
Based on the satellite data, one crater should be about 11 miles (18 kilometers) wide, while the other should be 7.4 miles (12 kilometers) wide.
For years, Abbott, of Columbia University's Lamont-Doherty Earth Observatory, has argued that V-shaped sand dunes along the gulf coast are evidence of a tsunami triggered by an impact.
"These dunes are like arrows that point toward their source," Abbott told National Geographic News.
In this case, the dunes converge on a single point in the gulf-the same spot where Abbott found the two sea-surface depressions.
The new work is the latest among several clues linking a major impact event to an episode of global cooling that affected crop harvests from A.D. 536 to 545, according to Abbott.
According to the theory, material thrown high into the atmosphere by the Carpentaria strike probably triggered the cooling, which has been pinpointed in tree-ring data from Asia and Europe.
"What's more, around the same time the Roman Empire was falling apart in Europe, Aborigines in Australia may have witnessed and recorded the double impact," she said.
Based on the new research, Abbott thinks the two craters were made by an object that split into pieces as it approached Earth.
"To make a pair of craters this big in the seafloor's soft sediments, the original object must have been about 2,000 feet (600 meters) across before it broke up," she said.
"Core samples from the region back up the case for such an impact," Abbott added.
Previous research had found that the samples contain smooth, magnetic spherules, which were probably created when the object's explosive landing melted material and blasted it into the sky.
Furthermore, a 2004 research suggested that the circa-A.D. 500 global cooling event might have been caused by dust from an impact of approximately the size Abbott has now calculated for Carpentaria.
According to Abbott and colleagues, several climate events during the Holocene epoch-11,500 years ago to the present-were actually triggered by impacts, and therefore such large impacts are more common than currently believed. (ANI)