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result(s) for
"Earth (Planet) Experiments."
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All about Earth : exploring the planet with science projects
\"Step-by-step instructions for activities pertaining to Earth, including its rotation in space, seasons, gravity, and matter\"-- Provided by publisher.
Book
2-D numerical experiments of thermal convection of highly viscous fluids under strong adiabatic compression: implications on mantle convection of super-Earths with various sizes
We conduct a series of numerical experiments of thermal convection of compressible fluids with temperature-dependent viscosity, in order to study how the adiabatic compression and model geometries affect the mantle convection on super-Earths. A two-dimensional basally heated convection is considered under the truncated anelastic liquid approximation (TALA), either in a rectangular box or in a cylindrical annulus. We varied the magnitude of adiabatic heating and the Rayleigh number as well as the depth profile of thermodynamic properties (thermal expansivity and reference density) in accordance with the planetary sizes. From our calculations by varying the planetary sizes up to 10 times the Earth’s mass, we confirmed that the adiabatic compression affects the thermal convection more strongly for larger planets. The activity of hot plumes originating from the core–mantle boundary is significantly suppressed in the terrestrial planets whose mass is larger than the Earth’s by a factor of about 3 regardless of the model geometries. We also developed scaling relationships between the vigor of thermal convection and the planetary mass by appropriately incorporating the effect of adiabatic compression into those of Boussinesq (or incompressible) cases. Our scaling relationships suggest that the stress level in the top cold thermal boundary layers is almost independent of the planetary mass, which may further imply that the emergence of plate tectonics is not likely to be enhanced for massive terrestrial planets whose composition is similar to the Earth’s.
Graphical Abstract
Journal Article
Living Earth : exploring life on Earth with science projects
\"Illustrated instructions for experiments pertaining to life on Earth, including photosynthesis, bacteria, minerals, and fossils\"-- Provided by publisher.
Book
Ancient Stratified Thermochemical Piles Due To High Intrinsic Viscosity
The two Large Low Velocity Provinces (LLVPs) in the lowermost Earth mantle are thought to affect large‐scale heat and material transport, governing mantle evolution. LLVPs have been interpreted as thermochemical piles of recycled oceanic crust (ROC) and/or other dense rock types. However, the role of ROC intrinsic viscosity in pile formation and related effects on mantle evolution remain poorly understood. Using mantle convection models, we show that, while ROC intrinsic density controls pile formation, intrinsic viscosity determines whether piles are internally convecting or stratified. Only high‐viscosity, stratified piles can preserve material over several billions of years. Pile stratification is therefore required to reconcile geochemical evidence for the survival of ancient reservoirs. Compositionally layered piles are also consistent with geophysical observations that point to vertical gradients in LLVP properties. As mineral physics constraints point to low‐viscosity ROC, our results suggest that LLVPs may be partly formed by early basal‐magma‐ocean cumulates. Plain Language Summary Earthquake‐produced vibrations travel long distances inside the Earth, but slow down when they cross two large blobs that lie thousands of kilometers below Africa and the Pacific Ocean. The nature of these anomalies is controversial, but it is thought that the crust, the outermost rocky peel that is continuously formed on the Earth's surface, may penetrate the planet's interior, sink and accumulate to form large piles. We employ a specialized code that is widely used to simulate movements of masses inside rocky planets over billions of years, including the process of crust formation and accumulation. We experiment with how dense and soft/strong (i.e., easy/hard to deform) this sunken crust is, relative to the surroundings. We investigate how these largely unknown properties affect pile formation and find that crustal strength has a marginal role compared to its density. However, only high strength makes piles layered and able to store ancient material, consistent with current observations. As recent laboratory experiments point to a soft crust, our results suggest that the piles observed today mainly contain “primitive” material that settled in the deep Earth during the very early stages of our planet's formation, instead of crust. Key Points Intrinsic viscosity of deep‐sunken oceanic crust does not affect its segregation and accumulation into piles High‐viscosity piles are stratified and able to store Archean‐age materials Large low velocity provinces may not be mainly formed of low‐viscosity oceanic crust
Journal Article
Liquid planet : exploring water on Earth with science projects
\"Illustrated instructions for experiments pertaining to water on Earth, including the water cylce, evaporation, transpiration, and precipitation\"-- Provided by publisher.
Book
The formation of Jupiter’s diluted core by a giant impact
The Juno mission
1
has provided an accurate determination of Jupiter’s gravitational field
2
, which has been used to obtain information about the planet’s composition and internal structure. Several models of Jupiter’s structure that fit the probe’s data suggest that the planet has a diluted core, with a total heavy-element mass ranging from ten to a few tens of Earth masses (about 5 to 15 per cent of the Jovian mass), and that heavy elements (elements other than hydrogen and helium) are distributed within a region extending to nearly half of Jupiter’s radius
3
,
4
. Planet-formation models indicate that most heavy elements are accreted during the early stages of a planet's formation to create a relatively compact core
5
–
7
and that almost no solids are accreted during subsequent runaway gas accretion
8
–
10
. Jupiter’s diluted core, combined with its possible high heavy-element enrichment, thus challenges standard planet-formation theory. A possible explanation is erosion of the initially compact heavy-element core, but the efficiency of such erosion is uncertain and depends on both the immiscibility of heavy materials in metallic hydrogen and on convective mixing as the planet evolves
11
,
12
. Another mechanism that can explain this structure is planetesimal enrichment and vaporization
13
–
15
during the formation process, although relevant models typically cannot produce an extended diluted core. Here we show that a sufficiently energetic head-on collision (giant impact) between a large planetary embryo and the proto-Jupiter could have shattered its primordial compact core and mixed the heavy elements with the inner envelope. Models of such a scenario lead to an internal structure that is consistent with a diluted core, persisting over billions of years. We suggest that collisions were common in the young Solar system and that a similar event may have also occurred for Saturn, contributing to the structural differences between Jupiter and Saturn
16
–
18
.
An energetic head-on collision between a large impactor and the proto-Jupiter with a primordial compact core could have mixed the heavy elements within the deep interior, leading to a ‘diluted’ core for Jupiter.
Journal Article
Dynamic planet : exploring changes on Earth with science projects
\"Illustrated instructions for experiments pertaining to changes on Earth, including plate tectonics, erosion, the greenhouse effect, and glaciers\"-- Provided by publisher.
Book
The Effect of Nitrogen on the Dihedral Angle Between Fe−Ni Melt and Ringwoodite: Implications for the Nitrogen Deficit in the Bulk Silicate Earth
Nitrogen (N) is extremely depleted in the bulk silicate Earth (BSE). However, whether the silicate magma ocean was as N‐poor as the present‐day BSE is unknown. We performed multi‐anvil experiments at 20 GPa and 1,673−2,073 K to determine the dihedral angle of Fe−Ni−N alloy melt in ringwoodite matrix to investigate whether percolation of Fe‐rich alloy melt in the solid mantle can explain N depletion in the BSE. The dihedral angles ranged from 112° to 137°, surpassing the wetting boundary. Our experiments suggest that N removal from the mantle by percolation of Fe‐rich alloy melt to the Earth's core is unlikely. Therefore, besides N loss to space during planetesimal and planetary differentiation, as well as its segregation into the Earth core, the stranded Fe‐rich metal in the deep mantle could be a hidden N reservoir, contributing to the anomalous depletion of N in the observable BSE. Plain Language Summary Understanding how and when the present‐day inventory of nitrogen (N) in the bulk silicate Earth (BSE) was established is important to gain insights into Earth's habitability. A key question remains as to why N is strongly depleted in the BSE than carbon and hydrogen. Efficient segregation of N into the metallic core in the final stage of Earth's formation is postulated to be one of the primary causes behind this depletion. However, it is not clear whether the silicate magma ocean (MO) was as depleted in N as the present‐day BSE due to the uncertainties in the degree of metal‐silicate equilibration during the final stages of Earth's formation. Post‐MO crystallization, Fe−Ni alloy precipitated in the reduced mantle owing to the disproportionation of ferrous iron. We used high‐pressure experiments to examine whether this Fe−Ni alloy melt can trap the excess N and percolate through the solid mantle to the core. Our experiments show that the percolation of Fe−Ni−N melt is unlikely owing to its dihedral angle in silicate phases being larger than the wetting boundary. Instead, the Fe−Ni−N alloy stranded in the mantle can be a hidden N reservoir and the present‐day BSE may not be as N‐depleted as predicted. Key Points Dihedral angles of Fe‐Ni‐N melt in ringwoodite matrix ranged from 112° to 137°, surpassing the wetting boundary Percolation of Fe−Ni−N melt through the solid mantle cannot explain N depletion in the bulk silicate Earth Fe−Ni−N alloy can be a hidden N reservoir in the mantle if excess N was present in the Earth's mantle post core‐mantle differentiation
Journal Article
Water in the Earth’s Interior: Distribution and Origin
The concentration and distribution of water in the Earth has influenced its evolution throughout its history. Even at the trace levels contained in the planet’s deep interior (mantle and core), water affects Earth’s thermal, deformational, melting, electrical and seismic properties, that control differentiation, plate tectonics and volcanism. These in turn influenced the development of Earth’s atmosphere, oceans, and life. In addition to the ubiquitous presence of water in the hydrosphere, most of Earth’s “water” actually occurs as trace amounts of hydrogen incorporated in the rock-forming silicate minerals that constitute the planet’s crust and mantle, and may also be stored in the metallic core. The heterogeneous distribution of water in the Earth is the result of early planetary differentiation into crust, mantle and core, followed by remixing of lithosphere into the mantle after plate-tectonics started. The Earth’s total water content is estimated at
18
−
15
+
81
times the equivalent mass of the oceans (or a concentration of
3900
−
3300
+
32700
ppm
weight H
2
O). Uncertainties in this estimate arise primarily from the less-well-known concentrations for the lower mantle and core, since samples for water analyses are only available from the crust, the upper mantle and very rarely from the mantle transition zone (410–670 km depth). For the lower mantle (670–2900 km) and core (2900–4500 km), the estimates rely on laboratory experiments and indirect geophysical techniques (electrical conductivity and seismology).
The Earth’s accretion likely started relatively dry because it mainly acquired material from the inner part of the proto-planetary disk, where temperatures were too high for the formation and accretion of water ice. Combined evidence from several radionuclide systems (Pd-Ag, Mn-Cr, Rb-Sr, U-Pb) suggests that water was not incorporated in the Earth in significant quantities until the planet had grown to
∼
60
–
90
%
of its current size, while core formation was still on-going. Dynamic models of planet formation provide additional evidence for water delivery to the Earth during the same period by water-rich planetesimals originating from the asteroid belt and possibly beyond. This early delivered water may have been partly lost during giant impacts, including the Moon forming event: magma oceans can form in their aftermath, degas and be followed by atmospheric loss. More water may have been delivered and/or lost after core formation during late accretion of extraterrestrial material (“late-veneer”). Stable isotopes of hydrogen, carbon, nitrogen and some noble gases in Earth’s materials show similar compositions to those in carbonaceous chondrites, implying a common origin for their water, and only allowing for minor water inputs from comets.
Journal Article
Rayleigh–Taylor instability in impact cratering experiments
When a liquid drop strikes a deep pool of a target liquid, an impact crater opens while the liquid of the drop decelerates and spreads on the surface of the crater. When the density of the drop is larger than the target liquid, we observe mushroom-shaped instabilities growing at the interface between the two liquids. We interpret this instability as a spherical Rayleigh–Taylor instability due to the deceleration of the interface, which exceeds the ambient gravity. We investigate experimentally the effect of the density contrast and the impact Froude number, which measures the importance of the impactor kinetic energy to gravitational energy, on the instability and the resulting mixing layer. Using backlighting and planar laser-induced fluorescence methods, we obtain the position of the air–liquid interface, an estimate of the instability wavelength, and the thickness of the mixing layer. We derive a model for the evolution of the crater radius from an energy conservation. We then show that the observed dynamics of the mixing layer results from a competition between the geometrical expansion of the crater, which tends to thin the layer, and entrainment related to the instability, which increases the layer thickness. The mixing caused by this instability has geophysical implications for the impacts that formed terrestrial planets. Extrapolating our scalings to planets, we estimate the mass of silicates that equilibrates with the metallic core of the impacting bodies.
Journal Article