Unexpected new findings by a University of Maryland team of geochemists show that some portions of the Earth’s mantle formed when the planet was much smaller than it is now, and that 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.

Prior to 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.