Scientists have discovered what they claim is the oldest, largest meteorite crater on Earth, likely formed some three billion years ago. Found in the town of Maniitsog in Greenland, this crater currently measures a huge impact zone of roughly 62 miles (about 100 kilometers) from one side to another.
Danish researcher Adam Garde, who found the crate, said it was likely more than 500 kilometers wide before it eroded, which would make it the biggest and oldest crater ever discovered on Earth. According to calculations, the crater was caused by a 30-kilometer wide meteorite so massive that if it hits Earth today, it would wipe out all higher life, Garde told OurAmazingPlanet.
The land has been eroded down to roughly 25 kilometers below the original surface in the three billion years since the impact. The effects of the great shock wave and heat, however, penetrated deep into the Earth and are still visible today, said Garde, who is a researcher at the Geological Survey of Denmark and Greenland.
While conducting research on Greenland's geology, Garde noticed some strange features that didn't make sense, and in September 2009 the researcher came up with the bold explanation of an impact from a meteorite. Over the years, Garde and his team collected several samples, and now Garde is "100 percent positive" it is a crater.
First of all, the researcher found widespread crushed rocks in a circular shape that appeared to be the result of shock waves following a massive impact. Second, the scientists found deposits of a melted mineral called K-feldspar, or potassium-feldspar. These deposits could have been liquefied only at extremely high heat such as that caused by a meteorite's crash-landing.
Moreover, Garde also found evidence of weathering by hot water. According to the researcher, this may have been caused by the ocean rushing into the crater after it struck the area. A shallow ocean may have covered that area at the time, but even if it didn't, it would still have rushed in. "The crater from a meteorite that big would have caused the sea to rush in," said Garde.
Before this crater was discovered in Greenland, the Vredefort crater in South Africa was thought to be the oldest crater on Earth, estimated to be some two billion years old. The Vredefort crater is also the largest crater that remains visible, measuring 186 miles (300 kilometers) in width. According to scientists, there likely were many more craters formed about three-four billion years ago, as the Earth lacked a protective atmosphere.
