London, Jun 29 (IANS): Geo-scientists have stumbled upon a vast, 100 km-wide crater in Greenland resulting from a massive asteroid hit a billion years before any other known collision on Earth.

The spectacular craters on the Moon formed from impacts with asteroids and comets between three and four billion years ago.

The early Earth, with its far greater gravitational mass, must have experienced even more collisions at this time - but the evidence has been eroded away or been covered by younger rocks, the journal Earth and Planetary Science Letters reported.

The previously oldest known crater on Earth formed two billion years ago and the chances of finding an even older impact were thought to be, literally, astronomically low.

Now, a team of scientists from the Geological Survey of Denmark and Greenland (GEUS) in Copenhagen, Cardiff University in Wales, Lund University in Sweden and the Institute of Planetary Science in Moscow have discovered the remains of a giant three billion year old impact near the Maniitsoq region of West Greenland.

"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," according to Iain McDonald of Cardiff's School of Earth and Ocean Sciences, who was part of the team.

Finding the evidence was made all the harder because there is no obvious bowl-shaped crater left to find. Over the three billion years since the impact, the land has been eroded down to expose deeper crust 25 km below the original surface.

Only around 180 impact craters have ever been discovered on Earth and around 30 percent contain important natural resources of minerals or oil and gas.