A synthesis of geochemical constraints on the inventory of light elements in the core of Mars

Icarus ◽  
2018 ◽  
Vol 315 ◽  
pp. 69-78 ◽  
Author(s):  
Edgar S. Steenstra ◽  
Wim van Westrenen
Keyword(s):  
Light Elements ◽  
The Core ◽  
Geochemical Constraints

Inefficient compaction in small planetary cores -- application to the Moon

2021 ◽  
Author(s):  
Marine Lasbleis
Keyword(s):  
Magnetic Field ◽  
Latent Heat ◽  
Energy Budget ◽  
Inner Core ◽  
Light Elements ◽  
The Moon ◽  
Small Bodies ◽  
Typical Size ◽  
The Core ◽  
Planetary Cores

<div> <p>Growth of the solid inner core is generally considered to power the Earth's present geodynamo. Cristallisation of a solid central inner core has also been proposed to drive the lunar dynamo and to generate a magnetic field in smaller bodies. In a previous work, we estimated the compaction of planetary cores for different scenarios of growth (with or without supercooling) and different sizes of the inner core. Our main results indicated that small inner cores are unlikely to compact efficiently the liquid trapped during the first steps of the growth.</p> <p>This is especially true for small bodies for which the typical size of the core is similar to the compaction length. The light elements are thus trapped during the cristallisation, reducing the release of latent heat and of light elements. We present here a model to include the effect of an inefficient compaction in the energy budget of a planetary core and investigate the implications for the dynamo evolution in small bodies. We apply this model for the evolution of the core of the Moon. </p> </div>

Metal-silicate fractionation in the deep magma ocean and light elements in the core

2006 ◽  
Vol 70 (18) ◽  
pp. A455
Author(s):  
E. Ohtani ◽  
T. Sakai ◽  
T. Kawazoe ◽  
T. Kondo
Keyword(s):  
Light Elements ◽  
Magma Ocean ◽  
The Core ◽  
Metal Silicate

scholarly journals Constraints on Earth’s inner core composition inferred from measurements of the sound velocity of hcp-iron in extreme conditions

2016 ◽  
Vol 2 (2) ◽  
pp. e1500802 ◽  
Author(s):  
Tatsuya Sakamaki ◽  
Eiji Ohtani ◽  
Hiroshi Fukui ◽  
Seiji Kamada ◽  
Suguru Takahashi ◽  
...  
Keyword(s):  
Sound Velocity ◽  
Inner Core ◽  
Earth Model ◽  
Light Elements ◽  
Earth’S Core ◽  
Heated Sample ◽  
Earth's Core ◽  
The Core ◽  
Core Composition ◽  
Earth’S Inner Core

Hexagonal close-packed iron (hcp-Fe) is a main component of Earth’s inner core. The difference in density between hcp-Fe and the inner core in the Preliminary Reference Earth Model (PREM) shows a density deficit, which implies an existence of light elements in the core. Sound velocities then provide an important constraint on the amount and kind of light elements in the core. Although seismological observations provide density–sound velocity data of Earth’s core, there are few measurements in controlled laboratory conditions for comparison. We report the compressional sound velocity (VP) of hcp-Fe up to 163 GPa and 3000 K using inelastic x-ray scattering from a laser-heated sample in a diamond anvil cell. We propose a new high-temperature Birch’s law for hcp-Fe, which gives us the VP of pure hcp-Fe up to core conditions. We find that Earth’s inner core has a 4 to 5% smaller density and a 4 to 10% smaller VP than hcp-Fe. Our results demonstrate that components other than Fe in Earth’s core are required to explain Earth’s core density and velocity deficits compared to hcp-Fe. Assuming that the temperature effects on iron alloys are the same as those on hcp-Fe, we narrow down light elements in the inner core in terms of the velocity deficit. Hydrogen is a good candidate; thus, Earth’s core may be a hidden hydrogen reservoir. Silicon and sulfur are also possible candidates and could show good agreement with PREM if we consider the presence of some melt in the inner core, anelasticity, and/or a premelting effect.

Geochemical Constraints on the Early Thermal History of the Earth

1989 ◽  
Vol 44 (10) ◽  
pp. 883-890 ◽  
Author(s):  
Michael J. Drake
Keyword(s):  
Upper Mantle ◽  
Partition Coefficients ◽  
Current Theory ◽  
Gravitational Potential Energy ◽  
The Moon ◽  
The Core ◽  
The Earth ◽  
History Of ◽  
Geochemical Constraints ◽  
Origin Of The Moon

Abstract Theories of the formation of the Earth strongly suggest that the Earth should have been substantially molten during and immediately after accretion. Estimates of the composition of the upper mantle indicate that many elements are present in chondritic ratios. Experimental measurements of element partition coefficients show that segregation of perovskite, majorite garnet, or olivine would fractionate the ratios of these elements away from chondritic values. The implication of these geochemical observations is that the Earth did not undergo extensive fractionation during and immediately following accretion. One possibility is that the Earth did not become substantially molten. Alternatively, if the Earth was indeed substantially molten, then it is possible that minerals were entrained in magma and were unable to segregate. In the former case, the accretional process must have delivered gravitational potential energy more slowly than current theory predicts, and an origin of the Moon in a giant impact would be unlikely. In the latter case, the high Mg/Si ratio in the upper mantle of the Earth relative to most classes of chondrites would be intrinsic to the silicate portion of the Earth. Unless significant amounts of Si exist in the core, the high Mg/Si ratio is a bulk planetary property, implying that the accretional process did not mix material between 1 AU and 2-4 AU.

scholarly journals Light elements in the core: Effects of impurities on the phase diagram of iron

2008 ◽  
Vol 35 (5) ◽  
Author(s):  
Alexander S. Côté ◽  
Lidunka Vočadlo ◽  
John P. Brodholt
Keyword(s):  
Phase Diagram ◽  
Light Elements ◽  
The Core

Exoplanetary magnetic fields as a tool for future interior characterization

2020 ◽  
Author(s):  
Irene Bonati ◽  
Marine Lasbleis ◽  
Lena Noack
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Magnetic Fields ◽  
Iron Content ◽  
Inner Core ◽  
Outer Core ◽  
Magnetic Activity ◽  
Light Elements ◽  
The Core ◽  
The Magnetic Field

<p>Most planets located within the solar system display evidence of past and/or current magnetic activity. Magnetic fields of rocky bodies are thought to be driven by thermo-chemical convection taking place in an electrically conducting fluid in their deep interior (the liquid outer core for Earth), and are thus evidence of strong internal dynamics. Furthermore, magnetism is thought to play a crucial role for the development and the long-term stability of habitable surface conditions, as it shields the upper atmosphere from mass loss induced by stellar winds and extreme space weather events.<span class="Apple-converted-space"> </span></p> <p>The discovery of a large number of rocky exoplanets motivates the search and the study of magnetic fields beyond the solar system. While current observations are limited to providing the planetary radius and minimum mass, future missions aimed at the exploration of exoplanetary atmospheres will open up new avenues for the inversion of interior properties starting from atmospheric parameters. Such a goal requires knowledge of the planetary cores and the development of exoplanetary magnetic fields, as well as their influence on atmospheric evolution and its interaction with the surrounding stellar wind.<span class="Apple-converted-space"> </span></p> <p>The aim of the current study is to identify trends and parameter(s) controlling the core evolution and magnetic field sustainment in super-Earths. To do this we investigate the evolution of the cores of planets having different masses (0.8-2 Earth masses) and iron inventories (bulk iron content and mantle iron number). Starting out from the internal temperature profile after the complete solidification of a global magma ocean (Noack and Lasbleis, 2020), we determine the size and the structure of the core, and model its thermal and magnetic evolution during the subsequent 5 billion years. By taking into account the energy release resulting from the growth of a solid inner core, we compute the thermal and compositional buoyancy fluxes, as well as the generated magnetic field strengths and lifetimes.<span class="Apple-converted-space"> </span></p> <p>Our findings show that while the planetary mass is not a controlling parameter, both the bulk iron content and the mantle iron number strongly influence inner core growth and the lifetime of the magnetic field. Iron-rich planets having a high mantle iron number tend to start out and end up with solid inner cores that are substantially larger than iron-poor bodies, sometimes even reaching up to the radius of the outer core and thus shutting down magnetic activity. We therefore find that there is a “sweet spot” for longer-lasting magnetic fields, located at intermediate bulk iron contents and low mantle iron numbers. <span class="Apple-converted-space"> </span></p> <p>We also varied the content of light elements in the core and found that the addition of a small fraction of light elements helps keeping the magnetic field active for longer, even at high bulk iron contents. Field strengths can reach up to several times the one of Earth, even though such a signal might still be too weak to be detected by current radio telescopes. Nevertheless, the development of new observation techniques and the multiple future missions devoted to atmospheric exploration will provide useful insights on the presence and frequency of planetary magnetic fields.</p>

What face familiarity feelings say about the lateralization of specific entities within the core system

2019 ◽  
Vol 42 ◽  
Author(s):  
Guido Gainotti
Keyword(s):  
Temporal Lobe ◽  
Memory System ◽  
Core System ◽  
The Core ◽  
Memory Traces ◽  
Specific Memory ◽  
Target Article ◽  
Temporal Structures ◽  
The Right

Abstract The target article carefully describes the memory system, centered on the temporal lobe that builds specific memory traces. It does not, however, mention the laterality effects that exist within this system. This commentary briefly surveys evidence showing that clear asymmetries exist within the temporal lobe structures subserving the core system and that the right temporal structures mainly underpin face familiarity feelings.

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