Washington, Jul 1 (IANS): The world's oldest meteorite crater - a giant impact zone more than 100 km wide - has been found in Greenland, scientists say.
Researchers think it was formed three billion years ago by a meteorite 30 km wide, which, if it hit Earth today, would wipe out all higher life, the Christian Science Monitor reported.
The crater was "discovered" by scientist Adam Garde as he pored over maps showing nickel and platinum abundance in West Greenland.
Garde, a senior research scientist with the Geological Survey of Denmark and Greenland, saw a both simple and extreme explanation for several strange geological features in this region: an impact from a meteorite that may have contained valuable metals.
A research team following up on Garde's research collected samples in 2011 that support his hypothesis, and the results were published in the journal Earth and Planetary Science Letters, the Monitor said.
"The process was rather like a Sherlock Holmes story," said science team member Iain McDonald of Cardiff University's School of Earth and Ocean Science in a statement.
"We eliminated the impossible in terms of any conventional terrestrial processes, and were left with a giant impact as the only explanation for all of the facts."
In the three billion years that have elapsed since the impact, the land has been eroded down to about 25 km below the original surface, and has lately also been carved and excavated by the Greenland ice sheet.
All external parts of the impact structure have thus long gone, but the effects of the intense impact shock wave penetrated deep into the interior of the Earth and these remain visible today, according to the study.
About 180 impact craters have been discovered on Earth, and nearly one third of them contain significant minerals deposits like precious metals.
Before this discovery, the oldest crater was thought to be two billion years old, and 300 km, located in South Africa, according to Monitor Friday.
Scientists suspect that there were many more craters formed around three billion to four billion years ago when Earth lacked a protective atmosphere, although the vast majority of these have been destroyed by erosion, plate tectonics and other processes.