Is Oxygen's Role In Core Formation Underestimated?
January 11, 2013

More Oxidizing Conditions Present During Formation Of Earth’s Core

redOrbit Staff & Wire Reports - Your Universe Online

The Earth´s core formed under more oxidizing conditions than previously believed, claims a new study published in Thursday´s edition of the journal Science Express.

Lawrence Livermore National Laboratory (LLNL) geophysicist Rick Ryerson and an international team of colleagues made the discovery following a series of laser-heated diamond anvil cell experiments at high pressure (350,000 to 700,000 atmospheres) and temperatures (5,120 to 7,460 degrees Fahrenheit).

Through their experiments, Ryerson´s team was able to demonstrate that the depletion of iron-loving or “siderophile” elements could be produced by core formation under more oxidizing conditions than past predictions had reported. They discovered that planet accretion or growth under these conditions was similar in nature to that of most common meteorites, officials from the laboratory said in a recent statement.

“While scientists know that the Earth accreted from some mixture of meteoritic material, there is no simple way to quantify precisely the proportions of these various materials. The new research defines how various materials may have been distributed and transported in the early solar system,” they explained.

Due to the close link between core formation and accretion, constraining the former process allowed Ryerson and colleagues from the from the Université Pierre et Marie Curie (UPMC) and the Institut de Physique du Globe de Paris (IPGP) to limit the range of materials that formed the Earth, as well as determine whether or not they changed throughout the years.

Their experiments demonstrated that core formation could slightly reduce siderphile elements such as vanadium and chromium, and well as moderately deplete nickel and cobalt. That discovery allows for oxygen to play a greater role in the formation of the planet´s core.

"A model in which a relatively oxidized Earth is progressively reduced by oxygen transfer to the core-forming metal is capable of reconciling both the need for light elements in the core and the concentration of siderophile elements in the silicate mantle, and suggests that oxygen is an important constituent in the core," the LLNL geophysicist said. "Our ability to match the siderophile element signature under more oxidizing conditions allows us to accrete the Earth from more common, oxidized meteoritic materials, such as carbonaceous and ordinary chondrites.”

“The earth's magnetic field is generated in the core, and protects the Earth from the solar wind and associated erosion of the atmosphere,” the laboratory added. “While the inner core of the Earth is solid, the outer core is still liquid. The ability to preserve a liquid outer core and the associated magnetic field are dependent on the composition of the core and the concentration of light elements that may reduce the melting temperature.”