Oxygen to the core

An international collaboration including researchers from Lawrence Livermore National Laboratory has discovered that the Earth’s core formed under more oxidizing condition’s than previously proposed.

Through of series of laser-heated diamond anvil cell experiments at high pressure (350,000 to 700,000 atmospheres of pressure) and temperatures (5,120 to 7,460 degrees Fahrenheit), the team demonstrated that the depletion of siderophile (also known as “iron loving”) elements can be produced by core formation under more oxidizing conditions than earlier predictions.

“We found that planet accretion (growth) under oxidizing conditions is similar to those of the most common meteorites,” said LLNL geophysicist Rick Ryerson.

The research appears in the Jan. 10 edition of Science Express.

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.

As core formation and accretion are closely linked, constraining the process of core formation allows researchers to place limits on the range of materials that formed our planet, and determine whether the composition of those materials changed with time. (Was accretion heterogeneous or homogeneous?)

“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,” Ryerson said.

The experiments demonstrated that a slight reduction of such siderphile elements as vanadium (V) and chromium (Cr) and moderate depletion of nickel (Ni) and cobalt (Co) can be produced during core formation, allowing for oxygen to play a more prominent role.

Planetary core formation is one of the final stages of the dust-to-meteorite-to-planet formation continuum. Meteorites are the raw materials for planetary formation and core formation is a process that leads to chemical differentiation of the planet. But meteorite formation and core formation are very different processes, driven by different heat sources and occurring in very different pressure and temperature ranges.

“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,” Ryerson said.

The earth’s magnetic field is generated in the core, and protects the Earth from the solar wind and associated erosion of the atmosphere. 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.

“By characterizing the chemical interactions that accompany separation of core-forming melts from the silicate magma ocean, we can hope to provide additional constraints on the nature of light elements in the present-day core and its melting/freezing behavior,” Ryerson said.

Seismic fabric coming on the market

Walls are 'papered' with long lengths of seismic fabric and then plastered. In case of emergency, the seismic fabric holds the debris and keeps escape routes free from obstruction. -  Photo: M. Urban/KIT
Walls are ‘papered’ with long lengths of seismic fabric and then plastered. In case of emergency, the seismic fabric holds the debris and keeps escape routes free from obstruction. – Photo: M. Urban/KIT

In the case of earthquakes, only seconds may remain for a safe escape from buildings. Debris falling down and obstructing the escape routes may even aggravate the situation. A product developed at Karlsruhe Institute of Technology (KIT) extends the time for saving lives by reinforcing walls and keeping off the debris. An innovative building material manufacturer now has launched the mature innovation on the market.

“The market launch has turned our lab idea into a concrete innovation,” rejoice the developers of the new reinforcing earthquake fabric. For several years, Lothar Stempniewski and Moritz Urban have investigated possibilities of low-cost retroactive securing and reinforcement of earthquake-prone walls of older buildings. They invented a glass fiber plastic fabric with four fiber directions. By means of an appropriate plaster, this special seismic fabric is applied onto the respective facings. Together with Dr. Günther Kast GmbH & Co. KG, a manufacturer of technical tissues, the high-tech tissue was developed to maturity. Under the brand name “Sisma Calce”, the Italian building material manufacturer Röfix, a subsidiary company of the German Fixit Group, now has included seismic fabric and a proper plaster in its product range.

Thanks to the reinforcement, collapsing of walls due to earthquakes can be delayed and, in the ideal case, be avoided completely. “Particularly in the case of short and moderate earthquakes, mostly not much more additional tensile strength is needed to avoid a collapse of the building,” explains Urban. The simplicity of that “prophylactic dressing” allows to apply it easily during renovation together with insulation. “In the case of a catastrophe,” Stempniewski adds, “much can be achieved if only we succeed in reinforcing and protecting critical infrastructures such as hospitals, schools, or rest homes.”

The high stiffness and considerable tensile strength of the glass fibers in the quasi plaster-integrated fabric allow walls to better reduce higher tensile stresses during earthquakes and avoid that punctual damage occurs and develops into cracks. Should the fibers rupture in spite of their strength during a heavy earthquake, the elastic polypropylene fibers will hold the broken wall segments together and keep them off the escape routes. The two developers are sure that “the reinforcing earthquake fabric gives occupants more time to escape buildings.” Under advantageous conditions, the walls may even stay intact and houses could be repaired after the earthquake.” The stabilizing deformation behavior contributes to a better reduction of the energy introduced into the walls through the horizontal forces of the earthquake’s acceleration forces.

In cooperation with Bayer MaterialScience AG, MAPEI S.p.A., and Dr. Günther Kast GmbH & Co. KG, the introduction of an adhesive seismic fabric for indoor use is currently being prepared. Besides researching into systems for masoned walls, the team around Stempniewski intends to investigate into reasonable solutions for concrete buildings. “The challenge in the case of concrete is the higher force that must be absorbed. We thus test new materials such as carbon fibers. In doing so, we at the same time lay the foundations for future innovations to be developed by KIT.” In total, Karlsruhe Institute of Technology already holds approximately 2000 patents in numerous research areas.