Earth's outer core deprived of oxygen: study


The composition of the Earth's core remains a mystery. Scientists know that the liquid outer core consists mainly of iron, but it is believed that small amounts of some other elements are present as well. Oxygen is the most abundant element in the planet, so it is not unreasonable to expect oxygen might be one of the dominant "light elements" in the core. However, new research from a team including Carnegie's Yingwei Fei shows that oxygen does not have a major presence in the outer core. This has major implications for our understanding of the period when the Earth formed through the accretion of dust and clumps of matter. Their work is published Nov. 24 in Nature.

According to current models, in addition to large amounts of iron, the Earth's liquid outer core contains small amounts of so-called light elements, possibly sulfur, oxygen, silicon, carbon, or hydrogen. In this research, Fei, from Carnegie's Geophysical Laboratory, worked with Chinese colleagues, including lead author Haijun Huang from China's Wuhan University of Technology, now a visiting scientist at Carnegie. The team provides new experimental data that narrow down the identity of the light elements present in Earth's outer core.

With increasing depth inside the Earth, the pressure and heat also increase. As a result, materials act differently than they do on the surface. At Earth's center are a liquid outer core and a solid inner core. The light elements are thought to play an important role in driving the of the liquid outer core, which generates the Earth's .

Scientists know the variations in density and speed of sound as a function of depth in the core from seismic observations, but to date it has been difficult to measure these properties in proposed iron alloys at core pressures and temperatures in the laboratory.

"We can't sample the core directly, so we have to learn about it through improved combined with modeling and ," Fei said.

High-speed impacts can generate shock waves that raise the temperature and pressure of materials simultaneously, leading to melting of materials at pressures corresponding to those in the outer core. The team carried out shock-wave experiments on core materials, mixtures of iron, sulfur, and oxygen. They shocked these materials to the liquid state and measured their density and traveling through them under conditions directly comparable to those of the liquid outer core.

By comparing their data with observations, they conclude that oxygen cannot be a major light element component of the Earth's outer core, because experiments on oxygen-rich materials do not align with geophysical observations. This supports recent models of core differentiation in early Earth under more 'reduced' (less oxidized) environments, leading to a core that is poor in oxygen.

"The research revealed a powerful way to decipher the identity of the light elements in the core. Further research should focus on the potential presence of elements such as silicon in the ," Fei said.

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Citation: Earth's outer core deprived of oxygen: study (2011, November 23) retrieved 17 October 2019 from
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Nov 23, 2011
The composition of the Earth's core remains a mystery.

Not to those who grasped - from experimental studies of meteorites, the Earth, the Moon and the Sun - that these objects accreted from poorly mixed debris of a supernova that produced our elements and gave birth to the Solar System about five billion years (5 Gyr) ago.

The data has been accumulating since 1960, but I suggest that readers start with this recent paper [1] and then work back through the reference.

1. "Neutron Repulsion", The
APEIRON Journal, in press (2011)

With kind regards,
Oliver K. Manuel

Nov 23, 2011
ROFLMFAO! Really? This is not "science".

Nov 23, 2011
Earth's core accreted from iron meteorites, composed of supernova debris that was produced close to the pulsar core.

Reed this 1981 paper and other earlier papers cited there:

"The noble gas record of the terrestrial planets",
Geochemical Journal 15, 247-267 (1981)

Nov 23, 2011
Yingwei Fei shows that oxygen does not have a major presence in the outer core

That IS expected.

Two of the world's best known geochemists - Turekian at Yale University and Vinogradov in Moscow - published papers in the 1960s and 1970s concluding terrestrial planets like Earth accreted in layers, beginning with their cores.

The Solar System formed directly from supernova debris, layered like the onion skins of a pre-supernova star:

Inner layers of major species near the SN core:

Pulsar/N,Fe/S/Si/ etc . . . .

Therefore S (sulfur) is the most likely light element in the Earth's liquid outer core and metallic Fe,Ni is dominant in the rigid inner core.

Troilite (Fe,NiS) - a common inclusion in diverse [1,2] meteorites - melts at lower temperatures than metallic (Fe,Ni).



Nov 24, 2011
At extreme pressures reactions may proceed in the unexpected direction due to formation of a denser phase being a lower energy state. So for example, perhaps Fe metal and Fe2O3 has a lower volume than FeO and therefore would be favourable at higher pressures. Turning olivine into solid oxygen seems pretty unlikely, but you would need to know the density of all the possible components at different pressures and the energy needed to chemically convert. Another way to approach the problem would be to look at the partial pressure of oxygen over hot mantle material at the temperature of the base of the mantle. And then compare how liquid iron dissolves oxygen at that pressure. The same could be repeated for each possible material that could move across the core mantle boundary, including sulfur, inert gases, nitrogen, or water.

We need to model tectonic processes that happen at the core boundary to get an idea of the rate of exchange of material near that boundary.

Nov 24, 2011
I love how omatumr tries to link everything ou there to his rediculouse fantasy that the sun is made out of iron!!! Guess its understandable that he wants to create a legacy considering he will soon be in jail.

Nov 24, 2011
Omatumr is annoying senile copy&paste spammer, but the idea, earth mantle was enriched with iron from meteorites isn't silly at all. After all, recently I read the speculation, the water of oceans comes from comets - so why not some iron? Of course it doesn't prove, the Sun is powered with neutron repulsion or something similar.

The question is, if its relevant to Earth core, which is much more deeper. The impacts cannot migrate so deep, until whole Earth mantle isn't molten and circulating wildly. If it would be molten, then we are talking about very early stage of Earth formation from planetesimals, when the heavier elements migrated to the center of Earth first.

Nov 24, 2011
Earth's core deprived of oxygen, . . .

. . . and iron meteorites are deprived of oxygen, because . . .

Light elements are destroyed by fusion in the e-process that makes Fe and Ni near the pulsar core of a supernova.

See: "Strange xenon, extinct super-heavy elements, and
the solar neutrino puzzle", Science 195, 208-209 (1977)

Nov 24, 2011
Sub; Earth Core-Earth region-Environment
Plasma Regulated Electromagnetic Phenomena in Magnetic Field Environment. Science needs to digest Dimensional comprehension.
Safe Earth Planet and life Support-means Wisdom should prevail in advance.

Nov 26, 2011
Oliver Manuel's recent efforts to plaster and other public news sites with his theories and personal URLs are a bit puzzling, as scientists have a variety of publications available to communicate directly to each other in. My best guess is that he is desperately trying to prop up his legacy in light of his arrest in his university office on 7 charges of rape and sodomy based on allegations by 4 of his own children. The charges have been reduced to one count of felony attempted sodomy, not necessarily because of his innocence, but because of the statute of limitations. One can only guess how the recent charges and decades of family strife have affected his ability to reason rationally and to remain objective while defending his unpopular theories.


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