Geochemists at the University of Maryland are studying a portion of the Earth's mantle that may have contributed to the formation of the Moon. The mantle is the rocky layer between the crust and the metallic core. This layer is believed to have been around since the Earth was a much smaller planet. It survived the turbulent formation of the Earth and collided with a large mass which many scientists say became the Moon.
Richard Walker, a professor of Geology and the leader of the research team, says, "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."
By analyzing radioactive isotopes, reseachers are able to determine the age of the rock and of certain internal processes. One of the five isotopes of tungsten, named isotope182-tungsten, can be formed from the radioactive decay of an unstable isotope, named 182-hafnium. 182-hafnium is no longer present today but it was around during the creation of the solar system. A 2.8 billion year old volcanic rock, komatiite, has been found to contain more amounts of isotope182-tungsten than normal.
"In itself this is not new but what is new and surprising is that a portion of the growing Earth developed the unusual chemical characteristics that could lead to the enrichment in 182-tungsten; that this portion survived the cataclysmic impact that created our moon; and that it remained distinct from the rest of the mantle until internal heat melted the mantle and transported some of this material to the surface 2.8 billion years ago, allowing us to sample it today." says Mathieu Touboul, a rsearch associate at the University of Maryland's Department of Geology.
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February 18, 2012