Research published last week in Science suggested that the makeup of the Earth's lower mantle, which makes up the largest part of the Earth by volume, is significantly different than previously thought.
The work, performed at the Advanced Photon Source at the U.S. Department of Energy’s Argonne National Laboratory, will have a significant impact on our understanding of the lower mantle, scientists said. Understanding the composition of the mantle is essential to seismology, the study of earthquakes and movement below the Earth's surface, and should shed light on unexplained seismic phenomena observed there.
We live atop the thinnest layer of the Earth: the crust. Below is the mantle (red), outer core (orange), and finally inner core (yellow-white). The lower portion of the mantle is the largest layer – stretching from 400 to 1,800 miles below the surface. Research at Argonne’s Advanced Photon Source recently suggested the makeup of the lower mantle is significantly different from what was previously thought. Image by Johan Swanepoel/Shutterstock. Click to enlarge.
Though humans haven't yet managed to drill further than seven and a half miles into the Earth, we've built a comprehensive picture of what's beneath our feet through calculations and limited observation. We all live atop the crust, the thin outer layer; just beneath is the mantle, outer core and finally inner core.
The lower portion of the mantle is the largest layer — stretching from 400 to 1,800 miles below the surface — and gives off the most heat. Until now, the entire lower mantle was thought to be composed of the same mineral throughout: ferromagnesian silicate, arranged in a type of structure called perovskite.
The pressure and heat of the lower mantle is intense — more than 3,500° Fahrenheit. Materials may have very different properties at these conditions; structures may exist there that would collapse at the surface.
To simulate these conditions, researchers use special facilities at the Advanced Photon Source, where they shine high-powered lasers to heat up the sample inside a pressure cell made of a pair of diamonds. Then they aim powerful beams of X-rays at the sample, which hit and scatter in all directions. By gathering the scatter data, scientists can reconstruct how the atoms in the sample were arranged.
The team found that at conditions that exist below about 1,200 miles underground, the ferromagnesian silicate perovskite actually breaks into two separate phases. One contains nearly no iron, while the other is full of iron. The iron-rich phase, called the H-phase, is much more stable under these conditions.
"We still don't fully understand the chemistry of the H-phase," said lead author and Carnegie Institution of Washington scientist Li Zhang. "But this finding indicates that all geodynamic models need to be reconsidered to take the H-phase into account. And there could be even more unidentified phases down there in the lower mantle as well, waiting to be identified."
The facilities at Argonne’s Advanced Photon Source were key to the findings, said Carnegie scientist Yue Meng, also an author on the paper. "Recent technological advances at our beamline allowed us to create the conditions to simulate these intense temperatures and pressures and probe the changes in chemistry and structure of the sample in situ," she said.
"What distinguished this work was the exceptional attention to detail in every aspect of the research — it demonstrates a new level for high-pressure research," Meng added.
The paper, "Disproportionation of (Mg,Fe)SiO3 perovskite in Earth’s deep lower mantle," was published in Science. Other Argonne coauthors were Wenjun Liu and Ruqing Xu.
The work was performed at the High Pressure Collaborative Access Team (HPCAT) beamline, which is run by the Geophysical Laboratory at the Carnegie Institution of Washington. Wenge Yang and Lin Wang from the APS-Carnegie Institution's High Pressure Synergetic Consortium (HPSynC) also contributed to the paper.
The research was supported by the National Science Foundation and performed at the HPCAT beamline of the Advanced Photon Source, which is supported by the U.S. Department of Energy's Office of Basic Energy Sciences, the National Nuclear Security Administration and the National Science Foundation. Portions of this work were performed at GeoSoilEnviroCARS at the APS, run by the University of Chicago and supported by the National Science Foundation and the DOE; at 34ID-E beamline; and at Shanghai Synchrotron Radiation Facility. The Advanced Photon Source is supported by DOE's Office of Basic Energy Sciences.
The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy's Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit the user facilities directory.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
Tona Kunz | Eurek Alert!
Oceans may be large, overlooked source of hydrogen gas
21.07.2016 | Duke University
Groundwater discharge to upper Colorado River Basin varies in response to drought
21.07.2016 | US Geological Survey
Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.
Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...
Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases
Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...
Scaffolding and specialised workers help with the delivery – Heidelberg biochemists gain new insights into biogenesis
A type of scaffolding on which specialised workers ply their trade helps in the manufacturing process of the two subunits from which the ribosome – the protein...
Scientists at the Helmholtz Zentrum München have developed a new mass spectrometry imaging method which, for the first time, makes it possible to analyze hundreds of metabolites in fixed tissue samples. Their findings, published in the journal Nature Protocols, explain the new access to metabolic information, which will offer previously unexploited potential for tissue-based research and molecular diagnostics.
In biomedical research, working with tissue samples is indispensable because it permits insights into the biological reality of patients, for example, in...
Chemists at the University of Basel have succeeded in using computer simulations to elucidate transient structures in proteins. In the journal Angewandte Chemie, the researchers set out how computer simulations of details at the atomic level can be used to understand proteins’ modes of action.
Using computational chemistry, it is possible to characterize the motion of individual atoms of a molecule. Today, the latest simulation techniques allow...
15.07.2016 | Event News
15.07.2016 | Event News
11.07.2016 | Event News
22.07.2016 | Information Technology
22.07.2016 | Physics and Astronomy
22.07.2016 | Life Sciences