A 100 kilometer-wide crater has been found in Greenland. The 3 billion year old impact crater - the result of a massive asteroid or comet impact - was found near the Maniitsoq region of West Greenland. The image above is an artist's interpretation of how a large meteorite impact into the sea might have looked in the first second of the impacting. The Maniitsoq crater is a billion years older than the previously oldest known crater on Earth. The Vredefort crater
in South Africa is estimated to be 2 billion years in age.
The crater was discovered by a team of scientists from Cardiff, the Geological Survey of Denmark and Greenland (GEUS) in Copenhagen, Lund University in Sweden and the Institute of Planetary Science in Moscow.
Dr Iain McDonald of Cardiff University's School of Earth and Ocean Sciences, says, "This single discovery means that we can study the effects of cratering on the Earth nearly a billion years further back in time than was possible before."
The researchers say finding the evidence of the impact crater was difficult because there is no obvious bowl-shaped crater left to find. Over the 3 billion years since the impact, the land has been eroded down to expose deeper crust 25 km below the original surface. All external parts of the impact structure have been removed. However, the effects of the intense impact shock wave penetrated deep into the crust - far deeper than at any other known crater - and these remain visible.
Dr. McDonald says, "The process was rather like a Sherlock Holmes story. 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."
The black circle on the map below shows the location of the meteorite impact structure near the town Maniitsoq in Greenland.
The first scientific paper documenting the discovery has been published here
in the journal Earth and Planetary Science Letters
Image: Carsten Egestal Thuesen, GEUS