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Christopher D. K. Herd - One of the best experts on this subject based on the ideXlab platform.
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Basalts as Probes of Planetary Interior Redox State
Reviews in Mineralogy and Geochemistry, 2008Co-Authors: Christopher D. K. HerdAbstract:Whether the redox state, quantified as oxygen fugacity, recorded in a Planetary basalt is an accurate representation of the redox state of the Planetary Interior from which it was derived through partial melting, ascent, eruption and emplacement is a fundamental question in Planetary geology. In the absence of mantle xenoliths in samples from the Moon, Mars and differentiated asteroids, the basalt-mantle source relationship must be extrapolated from what is known about the Earth in order to probe the redox state of these Planetary Interiors. A review of current knowledge regarding the basalt-mantle source relationship for the Earth provides insights into the advantages and pitfalls of determining mantle redox state. The range of currently available oxybarometers, including thermodynamic models based on ferrous-ferric mineral equilibria and multivalent cation analysis are surveyed and their limitations presented. The result is a basis for the informed interpretation of the oxygen fugacity of Planetary basalts, and new insights into the role of C-H-O volatiles in the terrestrial planets.
Marius Millot - One of the best experts on this subject based on the ideXlab platform.
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Experimental evidence for superionic water ice using shock compression
Nature Physics, 2018Co-Authors: Marius Millot, Raymond Jeanloz, Sebastien Hamel, J. Ryan Rygg, Peter M. Celliers, Gilbert W. Collins, Federica Coppari, Dayne E. Fratanduono, Damian C. Swift, Jon H. EggertAbstract:Although predicted to occur in Planetary Interiors, superionic water ice has proved elusive to identify experimentally. Laser-driven shock-compression experiments on water ice VII now verify its existence. In stark contrast to common ice, I _h, water ice at Planetary Interior conditions has been predicted to become superionic with fast-diffusing (that is, liquid-like) hydrogen ions moving within a solid lattice of oxygen. Likely to constitute a large fraction of icy giant planets, this extraordinary phase has not been observed in the laboratory. Here, we report laser-driven shock-compression experiments on water ice VII. Using time-resolved optical pyrometry and laser velocimetry measurements as well as supporting density functional theory–molecular dynamics (DFT-MD) simulations, we document the shock equation of state of H_2O to unprecedented extreme conditions and unravel thermodynamic signatures showing that ice melts near 5,000 K at 190 GPa. Optical reflectivity and absorption measurements also demonstrate the low electronic conductivity of ice, which, combined with previous measurements of the total electrical conductivity under reverberating shock compression, provides experimental evidence for superionic conduction in water ice at Planetary Interior conditions, verifying a 30-year-old prediction.
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Shock compression of stishovite and melting of silica at Planetary Interior conditions
Science (New York N.Y.), 2015Co-Authors: Marius Millot, Peter M. Celliers, Natalia Dubrovinskaia, Ana Cernok, Stephan Blaha, Leonid Dubrovinsky, Dave Braun, Gilbert Collins, Jon Eggert, Raymond JeanlozAbstract:Deep inside planets, extreme density, pressure, and temperature strongly modify the properties of the constituent materials. In particular, how much heat solids can sustain before melting under pressure is key to determining a planet’s internal structure and evolution. We report laser-driven shock experiments on fused silica, α-quartz, and stishovite yielding equation-of-state and electronic conductivity data at unprecedented conditions and showing that the melting temperature of SiO 2 rises to 8300 K at a pressure of 500 gigapascals, comparable to the core-mantle boundary conditions for a 5–Earth mass super-Earth. We show that mantle silicates and core metal have comparable melting temperatures above 500 to 700 gigapascals, which could favor long-lived magma oceans for large terrestrial planets with implications for Planetary magnetic-field generation in silicate magma layers deep inside such planets.
Raymond Jeanloz - One of the best experts on this subject based on the ideXlab platform.
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Experimental evidence for superionic water ice using shock compression
Nature Physics, 2018Co-Authors: Marius Millot, Raymond Jeanloz, Sebastien Hamel, J. Ryan Rygg, Peter M. Celliers, Gilbert W. Collins, Federica Coppari, Dayne E. Fratanduono, Damian C. Swift, Jon H. EggertAbstract:Although predicted to occur in Planetary Interiors, superionic water ice has proved elusive to identify experimentally. Laser-driven shock-compression experiments on water ice VII now verify its existence. In stark contrast to common ice, I _h, water ice at Planetary Interior conditions has been predicted to become superionic with fast-diffusing (that is, liquid-like) hydrogen ions moving within a solid lattice of oxygen. Likely to constitute a large fraction of icy giant planets, this extraordinary phase has not been observed in the laboratory. Here, we report laser-driven shock-compression experiments on water ice VII. Using time-resolved optical pyrometry and laser velocimetry measurements as well as supporting density functional theory–molecular dynamics (DFT-MD) simulations, we document the shock equation of state of H_2O to unprecedented extreme conditions and unravel thermodynamic signatures showing that ice melts near 5,000 K at 190 GPa. Optical reflectivity and absorption measurements also demonstrate the low electronic conductivity of ice, which, combined with previous measurements of the total electrical conductivity under reverberating shock compression, provides experimental evidence for superionic conduction in water ice at Planetary Interior conditions, verifying a 30-year-old prediction.
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Shock compression of stishovite and melting of silica at Planetary Interior conditions
Science (New York N.Y.), 2015Co-Authors: Marius Millot, Peter M. Celliers, Natalia Dubrovinskaia, Ana Cernok, Stephan Blaha, Leonid Dubrovinsky, Dave Braun, Gilbert Collins, Jon Eggert, Raymond JeanlozAbstract:Deep inside planets, extreme density, pressure, and temperature strongly modify the properties of the constituent materials. In particular, how much heat solids can sustain before melting under pressure is key to determining a planet’s internal structure and evolution. We report laser-driven shock experiments on fused silica, α-quartz, and stishovite yielding equation-of-state and electronic conductivity data at unprecedented conditions and showing that the melting temperature of SiO 2 rises to 8300 K at a pressure of 500 gigapascals, comparable to the core-mantle boundary conditions for a 5–Earth mass super-Earth. We show that mantle silicates and core metal have comparable melting temperatures above 500 to 700 gigapascals, which could favor long-lived magma oceans for large terrestrial planets with implications for Planetary magnetic-field generation in silicate magma layers deep inside such planets.
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Hot action at the core-mantle boundary
Eos Transactions American Geophysical Union, 1994Co-Authors: Raymond Jeanloz, Barbara RomanowiczAbstract:Recent discoveries about the Earth's most prominent internal feature, the core-mantle boundary, were revealed at a workshop just held at the University of California at Berkeley. The latest seismological evidence points to the interface between the mantle and core being among the most dynamically active regions of the Planetary Interior. Though distant, at 2890 km depth, the core-mantle boundary is significant: the contrasts in properties across this interface exceed even those between air and rock at the Earth's surface. Processes at the core's boundary influence the rotation and magnetic field of our planet and play an important role in the cycle of mantle convection that drives plate tectonics. In the interest of reviewing recent findings and coordinating future research, a workshop on Structure of the Core-Mantle Boundary and DH Region was held from September 10 to 11. Such workshops are among the activities sponsored by the new Cooperative Studies of the Earth's Deep Interior (CSEDI) initiative at the National Science Foundation.
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thermoelasticity of perovskite an emerging consensus
Eos Transactions American Geophysical Union, 1994Co-Authors: Raymond Jeanloz, Russell J HemleyAbstract:The current status of how well the thermoelastic properties of (Mg,Fe)SiO3 perovskite are known was addressed at a Special Session and Panel Discussion during the Fall 1993 AGU Meeting. Interest in the topic stems from the fact that silicate perovskite is the predominant mineral phase of the Earth's lower mantle, a region comprising over 60 (atomic) percent of the planet. Consequently, the properties of silicate perovskite largely control the evolution and state of the Planetary Interior. The view emerging from the discussion was that after 10 years of intense study, the thermal and elastic properties of silicate perovskite are finally coming into focus. Indeed, the bulk modulus of (Mg,Fe)Si03 perovskite is now among the best determined of any mineral's. In addition, this is perhaps the only material for which the thermal expansion coefficient has been directly measured at lower-mantle conditions of pressure and temperature. A number of other properties of silicate perovskites—some of which were discussed peripherally in the Special Session—are the subject of ongoing research and remain to be established. In contrast, there seems to be a growing consensus regarding several key thermoelastic properties that are vital for understanding the Earth's deep Interior.
Paul C Hess - One of the best experts on this subject based on the ideXlab platform.
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chemical dieferentiation of a convecting Planetary Interior consequences for a one plate planet such as venus
Geophysical Research Letters, 1992Co-Authors: E M Parmentier, Paul C HessAbstract:Partial melting to generate the crust of a planet creates compostionally buoyant residual mantle. In the absence of mantle flow associated with plate tectonics, this buoyant, refractory layer may collect at the top of the mantle with important implications for the evolution of the Interior and surface. In this study models of the thermal and chemical evolution of a Planetary Interior demonstrate the possible consequences of a chemically buoyant depleted mantle layer. As the depleted layer thickens the melting temperature at the top of the underlying convecting mantle also increases and the degree of partial melting of mantle added to the depleted layer decreases. As less depleted mantle with less positive compositional buoyancy is added, negative thermal buoyancy of the layer eventually exceeds its positive compositional buoyancy. The depleted layer then sinks into and mixes with the convecting Interior. The top of the convecting mantle then moves to a shallower depth, larger degrees of melting resume, and a new depleted layer accumulates. This accumulation and instability of the depleted layer occurs repeatedly over a substantial portion of the planet's evolution with a period of 300–500 Myr. On Venus the population of impacts craters is indistinguishable from a random distribution over the surface and give a surface age of about 500 Myr. We speculate that the mechanism described above may explain this episodic global resurfacing of Venus.
Stein B. Jacobsen - One of the best experts on this subject based on the ideXlab platform.
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Variational Principle for Planetary Interiors
The Astrophysical Journal, 2016Co-Authors: Li Zeng, Stein B. JacobsenAbstract:In the past few years, the number of confirmed planets has grown above 2000. It is clear that they represent a diversity of structures not seen in our own solar system. In addition to very detailed Interior modeling, it is valuable to have a simple analytical framework for describing Planetary structures. Variational principle is a fundamental principle in physics, entailing that a physical system follows the trajectory which minimizes its action. It is alternative to the differential equation formulation of a physical system. Applying this principle to Planetary Interior can beautifully summarize the set of differential equations into one, which provides us some insight into the problem. From it, a universal mass-radius relation, an estimate of error propagation from equation of state to mass-radius relation, and a form of virial theorem applicable to Planetary Interiors are derived.