Like other solar system bodies, the Earth too has been subject to numerous collisions with objects in space. Most of these collisions took place in the solar system’s earlier days, and have become more sporadic in later ages. Moreover, on Earth, evidence of these collisions has been slowly destroyed or hidden by geological and weathering processes. (Unlike, for example, the Moon, where evidence of collisions is preserved in the airless and geologically quiet conditions of the lunar surface.)
Now, geologists examining the land under southwestern Greenland have uncovered evidence of what seems to be the oldest and largest impact structure on Earth. While there is no obvious sign of the ancient collision on the surface, evidence for the meteor has been gathered from the coincidence of odd geological features in the region and underground signs of impact.
They hypothesis that a meteor impact occurred in the area was first raised by scientist Adam Garde of the Geological Survey of Denmark and Greenland in 2009. Garde had been examining the occurrence of nickel and platinum in the Maniitsoq region of Greenand. Knowing that mineral and metal concentrations have been associated with impact structures, Garde realized that an ancient impact could explain many of the area’s geological features. After sharing the idea with colleagues, and conducting subsequent studies, researchers are now confident that an impact is the best explanation for the evidence they have found in the area.
The researchers suggest that the impact occurred approximately three billion years ago when an object about 30 kilometers in diameter struck the sea, according to calculations by Boris Ivanov of the Institute of Planetary Science at the Russian Academy of Science. The resulting impact crater would be about 500 to 600 km in diameter. The researchers note that there is evidence of superheated fluid altering rocks in the area, which would be consistent with a massive impact at sea.
The researchers note that studying such impacts help scientists understand both the past and the future. Geological features, including some associated with valuable resources, are sometimes found in conjunction with impact geology. In addition, understanding such impacts sheds light not only on the formation and history of our own planet, but also on the environment of the early solar system. Finally, as long as future impacts remain a potential threat to the planet, learning as much as we can about previous ones is imperative.
The findings are reported in the journal Earth and Planetary Science Letters.