(Press-News.org) Washington, D.C.—Breaking research news from a team of scientists led by Carnegie's Ho-kwang "Dave" Mao reveals that the composition of the Earth's lower mantle may be significantly different than previously thought. These results are to be published by Science.
The lower mantle comprises 55 percent of the planet by volume and extends from 670 and 2900 kilometers in depth, as defined by the so-called transition zone (top) and the core-mantle boundary (below). Pressures in the lower mantle start at 237,000 times atmospheric pressure (24 gigapascals) and reach 1.3 million times atmospheric pressure (136 gigapascals) at the core-mantle boundary.
The prevailing theory has been that the majority of the lower mantle is made up of a single ferromagnesian silicate mineral, commonly called perovskite (Mg,Fe)SiO3) defined through its chemistry and structure. It was thought that perovskite didn't change structure over the enormous range of pressures and temperatures spanning the lower mantle.
Recent experiments that simulate the conditions of the lower mantle using laser-heated diamond anvil cells, at pressures between 938,000 and 997,000 times atmospheric pressure (95 and 101 gigapascals) and temperatures between 3,500 and 3,860 degrees Fahrenheit (2,200 and 2,400 Kelvin), now reveal that iron bearing perovskite is, in fact, unstable in the lower mantle.
The team finds that the mineral disassociates into two phases one a magnesium silicate perovskite missing iron, which is represented by the Fe portion of the chemical formula, and a new mineral, that is iron-rich and hexagonal in structure, called the H-phase. Experiments confirm that this iron-rich H-phase is more stable than iron bearing perovskite, much to everyone's surprise. This means it is likely a prevalent and previously unknown species in the lower mantle. This may change our understanding of the deep Earth.
"We still don't fully understand the chemistry of the H-phase," said lead author Li Zhang, also of Carnegie. "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."
INFORMATION:
The research is supported by National Science Foundation (NSF) grants EAR-0911492, EAR-1119504, EAR-1141929, and EAR-1345112. This work was performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT operations are supported by the U.S. Department of Energy-Basic Energy Sciences-National Nuclear Security Administration (DOE-NNSA) under Award DE-NA0001974 and DOE-Basic Energy Sciences (BES) under Award DE-FG02-99ER45775, with partial instrumentation funding by NSF. HPSynC is supported as part of EFree, an Energy Frontier Research Center funded by DOE-BES under grant DE-SC0001057. Portions of this work were performed at GeoSoilEnviroCARS (sector 13), APS, supported by the NSF-Earth Sciences (EAR-1128799) and DOE-GeoSciences (DE-FG02-94ER14466), at 34ID-E beamline, APS, and at 15U1, Shanghai Synchrotron Radiation Facility. Use of the APS facility was supported by DOE- BES under contract DE-AC02-06CH11357. This work was also partially supported by the Materials Research and Engineering Center program of the NSF under award DMR-0819885. Part of this work was carried out in the Characterization Facility of the University of Minnesota.
The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Lower mantle chemistry breakthrough
2014-05-22
ELSE PRESS RELEASES FROM THIS DATE:
Deep earth recycling of the oceanic floor
2014-05-22
Scientists from the Magma and Volcanoes Laboratory (CNRS/IRD/Université Blaise Pascal) and the European Synchrotron, the ESRF, have recreated the extreme conditions 600 to 2900 km below the Earth's surface to investigate the melting of basalt in the oceanic tectonic plates. They exposed microscopic pieces of rock to these extreme pressures and temperatures while simultaneously studying their structure with the ESRF's extremely powerful X-ray beam. The results show that basalt produced on the ocean floor has a melting temperature lower than the peridotite which forms the ...
Delegating the dirty work is a key to evolution
2014-05-22
EAST LANSING, Mich. — We have hundreds of types of cells in our bodies – everything from red blood cells to hair follicles to neurons. But why can't most of them create offspring for us?
New research at Michigan State University suggests that separating germ cells – sperm and eggs –from somatic cells – all other cells – preserves the genetic building blocks while allowing organisms to flourish in a somewhat hazardous environment.
The results, which appear in the current issue of PLOS Biology, show that having somatic cells do the organism's dirty work helps explain ...
Researchers identify key mechanism in metabolic pathway that fuels cancers
2014-05-22
DALLAS – May 22, 2014 – In a breakthrough discovery at the Children's Medical Center Research Institute at UT Southwestern (CRI), a research team led by Ralph DeBerardinis, M.D., Ph.D., has taken a significant step in cracking the code of an atypical metabolic pathway that allows certain cancerous tumors to thrive, providing a possible roadmap for defeating such cancers.
Published in Cell Reports, and following up on Dr. DeBerardinis' landmark finding in 2011, this most recent discovery identifies the triggering mechanism that plays a key role in causing a series of ...
Signals found that recruit host animals' cells, enabling breast cancer metastasis
2014-05-22
Working with mice, Johns Hopkins researchers report they have identified chemical signals that certain breast cancers use to recruit two types of normal cells needed for the cancers' spread. A description of the findings appears in the online early May edition of the Proceedings of the National Academy of Sciences.
"Blocking one of these cell-recruiting signals in a mouse's tumor made it much less likely to metastasize or spread," says Gregg Semenza, M.D., Ph.D., a professor and director of the Vascular Biology Program in the Johns Hopkins University School of Medicine's ...
Despite economic blows, infant health has improved among US poor
2014-05-22
Despite worsening economic conditions for those at the bottom, infant health has steadily improved among the most disadvantaged Americans, according to a review published in Science by Princeton University's Woodrow Wilson School of Public and International Affairs.
The researchers cite programs and policies like Medicaid, the Supplemental Feeding Program for Women, Infants, and Children (WIC) and the Food Stamp program – now known as Supplemental Nutrition Assistance Program (SNAP) – as the driving forces behind such marked improvements.
"We've long known that the ...
Two NASA Satellites see System 92b headed north in Bay of Bengal
2014-05-22
VIDEO:
In this TRMM 3-D simulated flyby of System 92B from May 21, some powerful convective storm tops were reaching heights of almost 17 km (about 10.5 miles).
Click here for more information.
NASA's Aqua and TRMM satellites captured radar and infrared data on developing tropical low pressure area System 92B as it now makes it way north through the Bay of Bengal.
On May 22 at 00:51 UTC, NASA and the Japan Aerospace Exploration Agency's Tropical Rainfall Measuring Mission (TRMM) ...
Antibiotic crisis needs united global response, experts say
2014-05-22
Growing resistance to antibiotics and other drugs demands a coordinated global response on the same scale as efforts to address climate change, experts say.
Without an international commitment to tackle the issue, the world faces a future in which simple infections that have been treatable for decades become deadly diseases, they warn.
Resistance to antibiotics to tackle bacterial infections and antimicrobial drugs used to treat parasites, viruses and fungi is spreading at an alarming rate. Treatment for many infectious diseases is now reliant on just one or two drugs.
Professor ...
Not all diamonds are forever
2014-05-22
Images taken by Rice University scientists show that some diamonds are not forever.
The Rice researchers behind a new study that explains the creation of nanodiamonds in treated coal also show that some microscopic diamonds only last seconds before fading back into less-structured forms of carbon under the impact of an electron beam.
The research by Rice chemist Ed Billups and his colleagues appears in the American Chemical Society's Journal of Physical Chemistry Letters.
Billups and Yanqiu Sun, a former postdoctoral researcher in his lab, witnessed the interesting ...
EuroPCR 2014 examines vascular response and long-term safety of bioresorbable scaffolds
2014-05-22
22 May 2014, Paris, France: At EuroPCR 2014 yesterday, experts discussed the development in evidence for bioresorbable vascular scaffolds, which represent an era of vascular restoration in interventional cardiology. The available data were analysed and participants heard that bioresorbable fixed strut vascular scaffolds are associated with increased acute thrombogenicity due to flow disturbances. This means that patients who are implanted with these devices need to receive ongoing dual antiplatelet therapy. The panellists also pointed out that endothelialisation is further ...
RaDAR guides proteins into the nucleus
2014-05-22
May 22, 2014, New York, NY – A Ludwig Cancer Research study has identified a novel pathway by which proteins are actively and specifically shuttled into the nucleus of a cell. Published online today in Cell, the finding captures a precise molecular barcode that flags proteins for such import and describes the biochemical interaction that drives this critically important process. The discovery could help illuminate the molecular dysfunction that underpins a broad array of ailments, ranging from autoimmune diseases to cancers.
Although small proteins can diffuse passively ...