Earth`s mantle survived collision that created Moon

Some portions of the Earth`s mantle were formed when the planet was much smaller than it is now.

Last Updated: Feb 18, 2012, 18:12 PM IST

Washington: Latest findings have shown that some portions of the Earth`s mantle were formed when the planet was much smaller than it is now.

Some of this early-formed mantle survived Earth’s turbulent formation, including a collision with another planet-sized body that many scientists believe led to the creation of the Moon, found a team of geochemists from the University of Maryland.

“It is believed that Earth grew to its current size by collisions of bodies of increasing size, over what may have been as much as tens of millions of years, yet our results suggest that some portions of the Earth formed within 10 to 20 million years of the creation of the Solar System and that parts of the planet created during this early stage of construction remained distinct within the mantle until at least 2.8 billion years ago,” said UMD Professor of Geology Richard Walker, who led the research team.
Before this finding, scientific consensus held that the internal heat of the early Earth, in part generated by a massive impact between the proto-Earth and a planetoid approximately half its size, would have led to vigorous mixing and perhaps even complete melting of the Earth.

This, in turn, would have homogenized the early mantle, making it unlikely that any vestiges of the earliest-period of Earth history could be preserved and identified in volcanic rocks that erupted onto the surface more than one and a half billion years after Earth formed.

However, the Maryland team examined volcanic rocks that flourished in the first half of Earth’s history, called komatiites, and found that these have a different type of composition than what they, or anyone, would have, expected.

Their findings were just published in the journal Science.

ANI