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There is a paucity of evidence preserved in the rock record regarding Earth's earliest enriched crust and its complementary depleted mantle during the Hadean. In recent years, vestiges of these early reservoirs have been inferred by examination of Hf isotope systematics compiled from zircons. The Singhbhum craton of Eastern India, for example, preserves only the existence of an enriched (εHf <0) crustal reservoir during the Hadean-Eoarchean, with the notable absence of a depleted mantle reservoir signature (εHf >0) until ca. 3.5 Ga. Here we report a new Sm-Nd isochron for the Lower Lava greenstones of the western Iron Ore Group from the Singhbhum craton, confirming a 3.42 ± 0.14 Ga crystallization age with an initial εNd of +5.7 ± 2.5. This is the highest positive εNd value derived from an isochron of this age. We infer that this depleted mantle source is a vestige complementary to the primary crust following planetary differentiation. Furthermore, we present U-Pb zircon ages for a 3.39 ± 0.02 Ga tuff that lies stratigraphically above the Lower Lava and <30 cm below an extensive conformable banded iron formation (BIF). This age implies that the western Iron Ore Group's BIF is the largest economic-grade iron formation of its Paleoarchean age, suggesting that free atmospheric oxygen existed as more than just whiffs at this time. [ABSTRACT FROM AUTHOR]

Triaxial deformation is a general feature of continental tectonics, but its controls and the systematics of associated fault networks remain poorly understood. We present triaxial analog experiments mimicking crustal thinning resulting from distributed longitudinal extension and lateral shortening. Contemporary longitudinal extension and lateral shortening are related by the principal horizontal strain ratio (PHSR). We investigate the effect of crustal geometry, rheology and strain rate on deformation localization, faulting regime and pattern, and PHSR in brittle and brittle‐viscous crustal‐scale models. We find that in brittle models the fault networks reflect the basal boundary condition and fault‐density scales inversely with brittle layer thickness. In brittle‐viscous models, as strain rate (ė) decreases, (a) Three fault patterns emerge: conjugate sets of strike‐slip faults (ė > 3 × 10−4 s−1, PHSR > 0.31), sets of parallel oblique normal faults (ė = 0.3–3 × 10−4 s−1, PHSR = 0.15–0.25), horst‐and‐graben system (ė < 0.3 × 10−4 s−1, PHSR < 0.1). (b) The strain localization increases systematically and gradually. We interpret the strain rate dependent of faulting regimes to be controlled by vertical coupling between the model upper mantle and model upper crust resulting in spontaneous permutation of principal stress axes. Rate‐dependency of strain localization can be related to mechanical coupling between the upper and lower crust. We identify the following parameters controlling triaxial tectonic deformation: upper crustal thickness and friction coefficient, lower crustal thickness and viscosity, as well as strain rate. We test our models and predictions against natural prototypes (Tibet, Anatolia, Apennines, and Basin and Range Province) thus providing new perspectives on triaxial deformation. Key Points: We conduct analog models where basal forces induce distributed deformation of continental tectonics under a triaxial deformation fieldStrain rate controls the strain localization and faulting regime via mechanical coupling between model upper crust, lower crust and mantleWe identify crustal geometry and rheology as factors controlling triaxial tectonics [ABSTRACT FROM AUTHOR]

Most of the Martian crust formed prior to ∼4 Ga, but the magmatic processes responsible for finalizing the structure and composition of the ancient crust remain enigmatic. Impacts can produce large volumes of melt under a wide range of melting pressures, temperatures, and degrees of melting. Hellas, Argyre, Isidis, and Utopia basins date to around 4 Ga, demonstrating that basin‐scale impacts helped to place the finishing touches on an already established crust. In this work, we focus on the ascent and intrusion of impact partial melts generated at mantle depths and the consequences for the petrology and structure of the Martian crust. Specifically, we show that the majority of impact partial melts are buoyant, favoring ascent to the surface or to neutral buoyancy levels in the crust, where magmas solidify as intrusive rocks. The composition of these polybaric melts overlaps with some ancient Martian igneous materials. We propose that the process of ascent of deep‐seated impact partial melts and intrusion at shallower levels may have contributed to the observed crustal stratification and ancient petrologic diversity on Mars. Plain Language Summary: When large asteroids collide with planets, they can cause melting of that planet's crust and mantle. This process of impact melting was likely more common when the solar system was young. In this work, we focus on partial melting during impacts on early Mars. We combine results from the modeling of impacts and magmas. Because we find that melts are less dense than their surroundings, they are likely to rise toward the surface of Mars. Based on their density, we predict that a large fraction of these magmas will freeze at the base of the Martian crust or within the crust, forming layers with distinct compositions that can be compared with rocks examined by Mars rovers and with seismic data from the InSight lander. Key Points: Impact partial melts are a volumetrically substantial counterpart to high‐degree meltsDeep‐seated impact partial melts are buoyant relative to surrounding mantle and crustal rocksAscent of ancient impact melts to neutral buoyancy levels in the Martian crust contributed to crustal layering and compositional diversity [ABSTRACT FROM AUTHOR]

Understanding the chemical composition of our planet's crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro‐ and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome‐dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling‐atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world. Key Points: Globally, the most bioavailable elements (Ca, Mg, and K) are amongst the most abundant in the crust, but N is more abundant than predictedBioavailability was controlled by soil pH, organic matter content, texture, plant cover, and climate, and altered by global changeElements were highly spatially correlated (coupled), and coupling was predictable by the atomic properties of elements, particularly mass [ABSTRACT FROM AUTHOR]

Numerical calculations of two component cellular convection with a lighter component diffusing down from the top are a simple model of the convection of rocky planets with a crust. The crust either is mixed down, floats along the top as blobs (continents separated by ocean basins), or forms layers. The calculations are for very viscous fluid with density variations from temperature and the lighter component representing the crust. If variations are approximately the same size, the lighter component collects along the top into H‐shaped blobs/clusters that have a flat midsection with two lobes on each end. Elevations are calculated for a free upper surface and the shape resembles continent and ocean floor topography with level interiors and thickening (mountains) at the edges produced by sinking at the margins. Between each pair of clusters, thermal and concentration boundary layers resemble ocean basins with spreading centers. Convection is unsteady but introducing internal decay of the lighter concentration produces steady flow. Internal heating produces similar results along with periodic drifting and merging of blobs like some geological cycles. The fact that these features arise without phase changes or viscosity variation implies that blobs of continent‐like crust might be widely found on rocky planets. Plain Language Summary: A simple numerical model of fluid flow has circulation cells driven by buoyancy. The cells are propelled by convection cells like mantle convection. Along the top, a model of a crust with lower density accumulates into a row of shapes. These resemble continents separated by ocean basins. Each accumulation is shaped like a wide capital letter H with a middle plateau and thickening (like mountains) at both ends. Cold, dense surface fluid plunges down next to each end like ocean trenches and subduction zones. These accumulations extend above the fluid surface because of their low density. Midway between each pair of these accumulations, hot fluid rises from the bottom and spreads out. The surface is depressed like ocean basins although the center is slightly elevated like mid‐ocean ridges. Forming these features from flow of a single constant viscosity fluid has not been previously done so the dynamics are discussed. Key Points: Convection cells with lighter fluid diffusing down from the top produce shapes like continents and ocean basins for certain parametersAdding internal heating produces cycles of splitting, drifting, and merging like the Wilson cycleThe calculations are simple and include two diffusivities for temperature and composition. A MATLAB code is included [ABSTRACT FROM AUTHOR]

We identify two ultra-cool (⁠|${T_\mathrm{eff}}\lt 4000$|  K) metal-polluted (DZ) white dwarfs WD J2147−4035 and WD J1922+0233 as the coolest and second coolest DZ stars known to date with |${T_\mathrm{eff}}\approx 3050$|  K and |${T_\mathrm{eff}}\approx 3340$|  K, respectively. Strong atmospheric collision-induced absorption (CIA) causes the suppression of red optical and infrared flux in WD J1922+0233, resulting in an unusually blue colour given its low temperature. WD J2147−4035 has moderate infrared CIA yet has the reddest optical colours known for a DZ white dwarf. Microphysics improvements to the non-ideal effects and CIA opacities in our model atmosphere code yields reasonable solutions to observations of these ultra-cool stars. WD J2147−4035 has a cooling age of over 10 Gyr which is the largest known for a DZ white dwarf, whereas WD J1922+0233 is slightly younger with a cooling age of 9 Gyr. Galactic kinematics calculations from precise Gaia EDR3 astrometry reveal these ultra-cool DZ stars as likely members of the Galactic disc thus they could be pivotal objects in future studies constraining an upper age limit for the disc of the Milky Way. We present intermediate-resolution spectroscopy for both objects, which provides the first spectroscopic observations of WD J2147−4035. Detections of sodium and potassium are made in both white dwarfs, in addition to calcium in WD J1922+0233 and lithium in WD J2147−4035. We identify the magnetic nature of WD J2147−4035 from Zeeman splitting in the lithium line and also make a tentative detection of carbon, so we classify this star as DZQH. WD J1922+0233 likely accreted planetary crust debris, while the debris composition that polluted WD J2147−4035 remains unconstrained. [ABSTRACT FROM AUTHOR]

Liquid water is a critical component of habitability. However, the production and stability of surficial liquid water can be challenging on planets outside the Habitable Zone and devoid of adequate greenhouse warming. On such cold, icy exo-Earths, basal melting of regional/global ice sheets by geothermal heat provides an alternative means of forming liquid water. Here, we model the thermophysical evolution of ice sheets to ascertain the geophysical conditions that allow liquid water to be produced and maintained at temperatures above the pressure-controlled freezing point of water ice on exo-Earths. We show that even with a modest, Moon-like geothermal heat flow, subglacial oceans of liquid water can form at the base of and within the ice sheets on exo-Earths. Furthermore, subglacial oceans may persist on exo-Earths for a prolonged period due to the billion-year half-lives of heat-producing elements responsible for geothermal heat. These subglacial oceans, often in contact with the planet's crust and shielded from the high energy radiation of their parent star by thick ice layers, may provide habitable conditions for an extended period. Liquid water is key for life as we know it. Here, the authors show even with a modest geothermal heat flow, subglacial oceans of liquid water can form at the base of and within the ice sheets on exo-Earths, which may provide habitable conditions for an extended period. [ABSTRACT FROM AUTHOR]

Mars early crust is more complex than homogenously basaltic with evolved magmatism evidenced by intermediate and felsic igneous rocks found in various locations in the southern hemisphere and martian meteorites. Geophysical constraints argue against a dense thick basaltic crust in the southern hemisphere, rather consistent with a buried light crust (<3,100 kg m−3), possibly evolved, underneath a basaltic surface. One of the oldest crustal components accessible at the surface of Mars, Terra Cimmeria/Sirenum (TSC), presents geochemical anomalies potentially suggesting an evolved crustal component at depth. Using visible/near infrared spectroscopy, we identify nine excavated feldspar‐rich locations in this region, and thermal infrared data suggest a silica concentration corresponding to intermediate compositions. The low density of such terrains compared to basalts supports that TSC crustal component is evolved. Early crusts of planetary bodies in the solar system were thus not restricted to basaltic compositions, and evolved crusts might have been widespread. Plain Language Summary: Despite basaltic terrains widely observed at the surface of Mars, recent missions and a martian meteorite evidenced evolved magmatism (SiO2 > 53 wt.%), highlighting a heterogeneous crust on Mars. Geophysical and seismic constraints suggest the presence of buried evolved crustal components with low density compared to basalts, below subsequent basaltic lava flows. We investigate one of the most ancient region accessible at the surface of Mars using visible/near infrared and thermal infrared spectroscopy to verify that hypothesis. Nine feldspar‐rich terrains excavated by impact, fractures, and erosion are detected with evolved compositions. One of the oldest crustal component on Mars thus presents an evolved crust underneath the surface, in agreement with geophysical/seismic data. Hence, planetary bodies early crusts are not systematically basaltic as generally thought, but could be evolved too as inferred from several rare evolved meteorites (e.g., Erg Chech 002). Key Points: Nine feldspar‐rich regions of intermediate silica compositions were identified in Terra Sirenum/Cimmeria (TSC)The feldspar‐rich terrains are excavated crustal materials supporting a pre‐Noachian evolved crust at TSCAn early evolved crust on Mars suggests that early crusts in the solar system were not restricted to basaltic [ABSTRACT FROM AUTHOR]

Eucrites exhibit a range of igneous and metamorphic textures and geochemistries that can be used to study the evolution of early planetary differentiation and crust formation in the solar system. We integrated petrologic/textural observations, in-situ geochemical analyses, and thermodynamic modeling to explore the petrogenesis of Elephant Moraine (EET) 90020, an unbrecciated meteorite. We identified microdomains that record relatively high metamorphic temperatures and concluded that diffusion processes likely modified EET 90020 during and/or after peak thermal conditions. There is little evidence that partial melting caused the distribution of minor and trace elements within or among the microdomains. Trace element linear transect measurements within the microdomains imply that phosphate minerals strongly controlled trace element distributions throughout the sample. The discrepancy between the observed metamorphic textures, major element chemistry, and the trace element distributions is a consequence of differing chemical mobility. Multiple processes are influencing geochemistry within a single sample which has implications for the development of petrogenetic models that seek to reconcile the differences observed between eucrite geochemical groups. [ABSTRACT FROM AUTHOR]

Erg Chech (EC) 002 is a meteorite with andesitic composition, potentially recording the lava crystallization and crust formation of its parent body. Nucleosynthetic Cr isotope composition (ε54Cr = −0.35 ± 0.06) for EC 002 suggests a non-carbonaceous region of the Solar system, and possibly represents the crustal composition of the brachinite parent body. The 53Mn-to-53Cr decay system shows it crystallized at 4566.6 ± 0.6 Ma, i.e. 0.7 ± 0.6 Ma after Solar system formation (only considering the cogenetic matrix fractions with similar ε54Cr values). This age represents the earliest recorded evidence for planetary melting and volcanism in the Solar system, suggesting that the planetary crust formation occurred very early, only within the first few hundred thousand years of Solar system history. However, the 53Mn–53Cr age does not overlap with 26Al–26Mg dating results, which might indicate that non-carbonaceous achondrites have lower initial 26Al/27Al than the canonical value defined by refractory inclusions in carbonaceous chondrites. [ABSTRACT FROM AUTHOR]

NASA's Gravity Recovery and Interior Laboratory (GRAIL) spacecraft revealed the crust of the Moon is highly porous, with ~4% porosity at 20 km deep. The deep lying porosity discovered by GRAIL has been difficult to explain, with most current models only able to explain high porosity near the lunar surface (first few kilometers) or inside complex craters. Using hydrocode routines we simulated fracturing and generation of porosity by large impacts in lunar, martian, and Earth crust. Our simulations indicate impacts that produce 100–1000 km scale basins alone are capable of producing all observed porosity within the lunar crust. Simulations under the higher surface gravity of Mars and Earth suggest basin forming impacts can be a primary source of porosity and fracturing of ancient planetary crusts. Thus, we show that impacts could have supported widespread crustal fluid circulation, with important implications for subsurface habitable environments on early Earth and Mars. Large impacts can create deep lying porosity far away from the crater. This result explains GRAIL's findings and suggests impacts could support widespread fluid circulation, which has implications for habitable environments on early Earth and Mars. [ABSTRACT FROM AUTHOR]

As odd as it may seem at first glance, minerals, it is what we are all about...or nearly. Although life on Earth is carbon-based, several other elements present in the planet's crust are involved in and often indispensable for functioning of living organisms. Many ions are essential, and others show supportive and accessory qualities. They are operative in the skin, supporting specific processes related to the particular situation of this organ at the interface with the environment. Skin bioenergetics, redox balance, epidermal barrier function, and dermal remodeling are amongst crucial activities guided by or taking advantage of mineral elements. Skin regenerative processes and skin ageing can be positively impacted by adequate accessibility, distribution, and balance of inorganic ions. [ABSTRACT FROM AUTHOR]

The polar motion of Mars is defined as the movement of the rotation axis with respect to a body-fixed frame tied to the crust of the planet. It is composed of forced motion at annual and sub-annual frequencies caused by the seasonal mass redistribution, formation of the polar ice caps and angular momentum variations of the atmosphere, and of the free mode called the Chandler wobble. Radio-tracking data from landers offers the most suitable means to measure the rotation of Mars, including its polar motion. The latter, however, has not yet been achieved using lander data alone. In this study, we assess the uncertainties associated with Mars polar motion estimation using Direct-To-Earth Doppler, range and Same-Beam Interferometry (SBI) observables between multiple landers on the surface of Mars. We evaluate the improvement enabled by combining data from multiple landers with respect to one-lander scenarios, and identify the optimal mission architectures for polar motion estimation by considering the influence of respective mission parameters on the estimation uncertainty. In particular, we consider the effects of absolute and relative locations of the landers and of mission scheduling. We re-evaluate the possibility of estimating the polar motion using data from landers in proximity to the equator, and apply our considerations to simulated data consistent in number and accuracy with that collected by past Martian missions. We notice and explain a strong longitude dependence of the formal errors when the polar motion parameters are estimated concurrently with the seasonal spin variation parameters, making it impossible to properly determine all components of polar motion with a single lander regardless of its location. However, the use of two or more landers in optimal locations with respect to each other eliminates those limitations. We evaluate the influence of latitudinal and longitudinal separation on polar motion determination in such cases. In particular, we are able to determine polar motion well even in cases where the longitudes of the two landers make determination from each single lander impossible. • Lander data is necessary for the determination of seasonal Mars polar motion terms. • Determining polar motion using radiometric data from a single lander is not possible. • Doppler data from two landers in optimal locations enables polar motion determination. • Combining Doppler and SBI improves precision, mitigates shortcomings of each. [ABSTRACT FROM AUTHOR]

The availability of thermodynamic data for geologically relevant phases has made practical the calculation of stable phase relations throughout the mantle and crust of terrestrial planets. GeoPS (http://www.geops.org) is a program designed for this purpose in which both input and output are done through an intuitive graphical user interface. GeoPS provides a wide range of phase equilibrium calculations based on a novel Gibbs energy minimization algorithm. The algorithm provides for exceptionally robust and computationally efficient solution to the phase equilibrium problem by successive alternation between a linear programming step to identify stable phase compositions and a non‐linear programming step to refine the compositions estimated during the linear programming. Applications include calculation of various types of phase diagrams and path‐dependent phase fractionation. By combining an easy‐to‐use graphical user interface with a robust and efficient solver, GeoPS makes phase equilibrium modelling accessible to researchers and students with minimal training and provides a powerful tool for understanding natural phase relations and for planning experimental work. [ABSTRACT FROM AUTHOR]

Fault evolution in oblique and orthogonal rift systems in the brittle upper crust of the Rukwa rift basin was simulated using scaled sandbox modelling by varying the angle between the rift axis and the extension direction, α, through 45° and 90°, over a 10 cm displacement. The 45° oblique model exhibits a half-graben architecture bounded by a planar fault, intra-rift faults and a conjugate fault in some vertical sections. The map view of the model's basin trends in the NW-SE direction, and is comparable with the Rukwa rift basin orientation. The 90° oblique model forms a basin structure which is orthogonal to the extension direction of the model in aerial photos. Its linear fault remains orthogonal to the extension direction, while the flexural side of the model segments into sinuous normal faults. Planar to slightly curved intra-rift faults are observed in vertical sections. The half-grabens have similar geometries in vertical sections for both models, while intra-rift faults elongate in vertical sections. The results of the oblique model are similar to natural examples of rift fault systems like the Rukwa rift. The fault geometries of the sandbox models can serve as examples for recognizing fault styles in oblique rift systems. [ABSTRACT FROM AUTHOR]

Deep space exploration technology is an important development direction for scientific exploration. The penetrator method has been proposed as an inexpensive method of studying planetary bodies. The basic principle of this method is that the detection equipment carried by the high-speed penetrator hits a planetary body at a high speed and is buried up to several meters below the surface to carry out detection work. During the frictional collision process with the planets crust, the instantaneous acceleration peaks of the scientific payload (electronic instrumentation) are large. Shock protection of these payloads is necessary to improve their survival and mission success. In this paper, with the goal of improving the survival rate of scientific loads inside a penetrator, a penetrator with a multilayer energy-absorbing structure is developed, in which cushioning protection measures, such as an aluminum foam-filled corrugated tube(AFFT) structure, polyurethane rubber, and epoxy resin potting, are applied to the penetrator. Since the analysis of this process is a highly nonlinear problem, a numerical modeling method is the main approach in this paper. The LS-DYNA software platform was used to simulate the penetrators penetration process on a moon soil medium. The results obtained using empirical formulas and theoretical derivations were compared with the results of numerical analysis to ensure the accuracy of the penetration simulation model. The finite element model of the penetrator was then verified and modified by conducting shock response spectral experiments and shock simulations. The results showed that the spacer scheme had a positive effect on the impact isolation and energy absorption. In addition, this scheme provides an important reference for the design of the penetrator prototype to guarantee the success of subsequent ground rocket sled experiments. • The buffering and energy absorption characteristics of the proposed AFFT structure are analyzed applied to the penetrator. • Through numerical simulation of the penetration process, the initial velocity satisfying the penetration depth was obtained. • The impact response spectrum test and simulation analysis of the penetrator prototype have verified the numerical model. [ABSTRACT FROM AUTHOR]

The third stage of the Saturn IV rocket used in the five Apollo missions made craters on the Moon ∼30 m in diameter. Their initial impact conditions were known, so they can be considered controlled impacts. Here, we used the iSALE‐2D shock physics code to numerically simulate the formation of these craters, and to calculate the vertical component of seismic moment (∼4 × 1010 Nm) and seismic efficiency (∼10−6) associated with these impacts. The irregular booster shape likely caused the irregular crater morphology observed. To investigate this, we modeled six projectile geometries, with footprint area between 3 and 105 m2, keeping the mass and velocity of the impactor constant. We showed that the crater depth and diameter decreased as the footprint area increased. The central mound observed in lunar impact sites could be a result of layering of the target and/or low density of the projectile. Understanding seismic signatures from impact events is important for planetary seismology. Calculating seismic parameters and validating them against controlled experiments in a planetary setting will help us understand the seismic data received, not only from the Moon, but also from the InSight Mission on Mars and future seismic missions. Plain Language Summary: Observations of meteoroid strikes on the Moon, including artificial impacts made by the Saturn boosters from the Apollo missions, present valuable information for connecting impact conditions with seismic properties of the lunar and planetary crusts. These artificial impacts on the Moon were made by irregularly shaped spacecraft with low density. We numerically simulated these artificial impacts, using several different projectile geometries in order to represent the spacecraft's low density and shape. We found that the projectile representation affected the crater size. We calculated the amount of energy transferred into seismic waves and seismic moment created in these impacts to be consistent with previous studies. These parameters did not change with different projectile representations, but were affected by the material properties of the impact site. The aim is to use the results from the controlled lunar impacts to help understand the seismic signatures of impacts on Mars. Key Points: Numerical impact simulations of the Apollo rocket stage drop on the MoonProjectile geometry affects cratering process, cratering efficiency, and momentum transferEstimates of the seismic moment and seismic efficiency in these impacts [ABSTRACT FROM AUTHOR]

Fractionation effects related to evaporation and condensation had a major impact on the current elemental and isotopic composition of the Solar System. Although isotopic fractionation of moderately volatile elements has been observed in tektites due to impact heating, the exact nature of the processes taking place during hypervelocity impacts remains poorly understood. By studying Fe in microtektites, here we show that impact events do not simply lead to melting, melt expulsion and evaporation, but involve a convoluted sequence of processes including condensation, variable degrees of mixing between isotopically distinct reservoirs and ablative evaporation during atmospheric re-entry. Hypervelocity impacts can as such not only generate isotopically heavy, but also isotopically light ejecta, with δ56/54Fe spanning over nearly 5‰ and likely even larger variations for more volatile elements. The mechanisms demonstrated here for terrestrial impact ejecta modify our understanding of the effects of impact processing on the isotopic evolution of planetary crusts. Fe isotopic composition of the distal ejecta of a terrestrial impact crater records both evaporation and condensation, refining the nature of the isotopic fractionation taking place during hypervelocity impacts in the Solar System. [ABSTRACT FROM AUTHOR]

Isostasy explains why observed gravity anomalies are generally much weaker than what is expected from topography alone, and why planetary crusts can support high topography without breaking up. On Earth, it is used to subtract from gravity anomalies the contribution of nearly compensated surface topography. On icy moons and dwarf planets, it constrains the compensation depth which is identified with the thickness of the rigid layer above a soft layer or a global subsurface ocean. Classical isostasy, however, is not self-consistent, neglects internal stresses and geoid contributions to topographical support, and yields ambiguous predictions of geoid anomalies. Isostasy should instead be defined either by minimizing deviatoric elastic stresses within the silicate crust or icy shell, or by studying the dynamic response of the body in the long-time limit. In this paper, I implement the first option by formulating Airy isostatic equilibrium as the linear response of an elastic shell to a combination of surface and internal loads. Isostatic ratios are defined in terms of deviatoric Love numbers which quantify deviations with respect to a fluid state. The Love number approach separates the physics of isostasy from the technicalities of elastic-gravitational spherical deformations, and provides flexibility in the choice of the interior structure. Since elastic isostasy is invariant under a global rescaling of the shell shear modulus, it can be defined in the fluid shell limit, which is simpler and reveals the deep connection with the asymptotic state of dynamic isostasy. If the shell is homogeneous, minimum stress isostasy is dual to a variant of elastic isostasy called zero deflection isostasy, which is less physical but simpler to compute. Each isostatic model is combined with general boundary conditions applied at the surface and bottom of the shell, resulting in one-parameter isostatic families. At long wavelength, the thin shell limit is a good approximation, in which case the influence of boundary conditions disappears as all isostatic families members yield the same isostatic ratios. At short wavelength, topography is supported by shallow stresses so that Airy isostasy becomes similar to either pure top loading or pure bottom loading. The isostatic ratios of incompressible bodies with three homogeneous layers are given in analytical form in the text and in complementary software. [ABSTRACT FROM AUTHOR]

Flux ropes are a magnetic field phenomenon characterized by a filament of twisted, helical magnetic field around an axial core. They form in the Martian ionosphere via three distinct mechanisms: Boundary wave instabilities (BWI), external reconnection (ER) between the interplanetary magnetic field and the crustal anomalies, and internal reconnection (IR) of the crustal anomalies themselves. We have identified 121 magnetic flux ropes (FR) from 1900 orbits using plasma and magnetic field measurements measured by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, and separate FR into categories based on formation mechanism by analyzing electron signatures. We find evidence for flux ropes formed via BWI, ER, and IR mechanisms which comprise 9%, 34%, and 57% of our data‐set, respectively. FR formed via different mechanisms exhibit differences in location and force‐free radius, indicating the formation mechanism of a FR impacts their influence on the Martian plasma environment. Plain Language Summary: Mars possess localized magnetic fields that are frozen into the crust of the planet and protrude out into space. On the dayside of Mars, the crustal fields interact with the charged particles and magnetic field lines that are emanating away from the Sun known as the solar wind. The processes involved in this interaction create the Martian "magnetosphere," and can have a variety of implications on the evolution of the Martian atmosphere. One by‐product of this interaction is a "magnetic flux rope," (FR) which is a twisted filament of magnetic flux and plasma. FR shows evidence for the reconfiguration of magnetic field lines within the magnetosphere, and lead to atmospheric loss at Mars. Using data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we analyze 121 events in which the spacecraft encountered a FR along its orbit around Mars. This is the first study to show evidence for Martian FR having been formed via three distinct formation mechanisms. FR formed via different mechanisms exhibit differences in geographic location and size, indicating the formation mechanism of a FR impacts their influence on the Martian magnetospheric and atmospheric environment. Key Points: Flux ropes form at Mars via three distinct processes: Boundary wave instabilities, external reconnection, and internal reconnectionAcross 1,900 orbits, we identify and analyze 121 magnetic flux ropes (FR) within the ionosphere of Mars using observations from Mars Atmosphere and Volatile EvolutioNUsing electron and magnetic field observations, we separate the FR into three categories based on formation mechanism [ABSTRACT FROM AUTHOR]

Chromium is a serious heavy metal (HM) and its concentration in plant-soil interface is soaring due to anthropogenic activities, unregulated disposals, and lack of efficient treatments. High concentration of Cr is toxic to ecosystems and human health. Cr stress also diminishes the plant performance by changing the plant's vegetative and reproductive development that ultimately affects sustainable crop production. Silicon (Si) is the second-most prevalent element in the crust of the planet, and has demonstrated a remarkable potential to minimize the HM toxicity. Amending soils with Si mitigates adverse effects of Cr by improving plant physiological, biochemical, and molecular functioning and ensuring better Cr immobilization, compartmentation, and co-precipitation. However, there is no comprehensive review on the role of Si to mitigate Cr toxicity in plants. Thus, in this present review; the discussion has been carried on; 1) the source of Cr, 2) underlying mechanisms of Cr uptake by plants, 3) how Si affects the plant functioning to reduce Cr toxicity, 4) how Si can cause immobilization, compartmentation, and co-precipitation 5) strategies to improve Si accumulation in plants to counter Cr toxicity. We also discussed the knowledge gaps and future research needs. The present review reports up-to-date knowledge about the role of Si to mitigate Cr toxicity and it will help to get better crop productivity in Cr-contaminated soils. The findings of the current review will educate the readers on Si functions in reducing Cr toxicity and will offer new ideas to develop Cr tolerance in plants through the use of Si. • Cr as a heavy metal accumulates indiscriminately in plant-soil interface. • Cr induces ionic, osmotic and oxidative stress in plants. • Si acts as a potential signaling inorganic elicitor in plants. • Si shows a potential trade-off with other molecules to impart stress tolerance. • The review highlights current knowledge of Si to mitigate Cr phyto-toxicity to get enhanced crop productivity. [ABSTRACT FROM AUTHOR]

Mercury's crustal magnetic field map includes anomalies that are related to impact craters. Mercury's surface has a low iron abundance, but it is likely that some impactors brought magnetic carriers able to register the planet's magnetic field that was present during impact. Anomalies associated with the relatively young Rustaveli and Stieglitz craters are asymmetric with respect to the crater center. We analyze the location of the magnetic anomalies and the impact crater morphologies to understand whether there is any correlation. We investigate the geological framework of these two craters to constrain the overall impact dynamics. In both cases, magnetic anomalies correlate well with the location of impact melt and the inferred impact direction. Both impact angles were probably 40°–45°, with preferential distribution of the melt downrange. Inversion dipoles suggest that the impact melt located downrange encompasses some magnetized material, which is hence likely responsible for the detected magnetic anomalies. Plain Language Summary: We observe strong crustal magnetic field imprints near two recent craters on Mercury. We know that the crust of rocky planets may include magnetic elements like iron that can record the local magnetic field under certain circumstances. However, Mercury's crust is known to be remarkably poor in iron. In this study, we want to find out whether these observed magnetic imprints near craters happened by chance or if it can be explained by the impactors bringing iron to Mercury's surface. We make a joint‐study of two different scientific areas: Geology and geophysics. Via the geological study, we found an uneven distribution of "impact melt," which is material flung out of the crater in molten form during the impact that made the crater. Via the geophysical study, we found evidence that magnetized material correlates with the position of those pools that are found in the downrange direction of the impact. In conclusion, this study supports the hypothesis that iron was brought on Mercury by the impactors. Key Points: Stieglitz and Rustaveli are two young impact craters on Mercury associated with overlapping crustal magnetic anomaliesThe magnetic anomalies are asymmetrical with respect to each crater's center and correlate well with the location of impact meltThe impact melt located downrange contains impactor magnetic‐carriers that recorded the magnetic field of Mercury at the time of quenching [ABSTRACT FROM AUTHOR]

The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal–sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond. [ABSTRACT FROM AUTHOR]

Accurately quantifying the composition of continental crust on Hadean and Archean Earth is critical to our understanding of the physiography, tectonics, and climate of our planet at the dawn of life. One longstanding paradigm involves the growth of a relatively mafic planetary crust over the first 1 to 2 billion years of Earth history, implying a lack of modern plate tectonics and a paucity of subaerial crust, and consequently lacking an efficient mechanism to regulate climate. Others have proposed a more uniformitarian view in which Archean and Hadean continents were only slightly more mafic than at present. Apart from complications in assessing early crustal composition introduced by crustal preservation and sampling biases, effects such as the secular cooling of Earth's mantle and the biologically driven oxidation of Earth's atmosphere have not been fully investigated.We find that the former complicates efforts to infer crustal silica from compatible or incompatible element abundances, while the latter undermines estimates of crustal silica content inferred from terrigenous sediments. Accounting for these complications, we find that the data are most parsimoniously explained by a model with nearly constant crustal silica since at least the early Archean. [ABSTRACT FROM AUTHOR]

Planetary crusts undergo viscous closure of pores at depth; if the thickness of this porous layer can be measured, constraints on crustal thermal evolution can be derived. We apply a pore closure model developed for the Moon to Mars and take into account the geological processes that may alter the depth of this transition region. If the 8–11 km deep discontinuity in seismic wave speed detected by the InSight lander marks the base of the porous layer, the heat flux at the time the porosity was created must have exceed 60 mW m−2, probably indicating a time prior to 4 Ga. Plain Language Summary: On long timescales, and with enough heat or pressure, rocks in the crust of a planet can flow. This viscous deformation allows the empty pore spaces in a rock to close up. The history of the temperature at depth plays an important role in how deep one may expect porosity to exist. One can use a computational model to calculate the thickness of this porous layer as a function of the crust's thermal history. If the InSight Mars lander detects the thickness of such a porous layer, we can estimate the necessary temperature structure of the Martian crust and when porosity in the crust was generated. From a potential measurement of this porous layer at around 10 km thick, we predict the last significant pore formation event to have occurred at least 4 Gyr before present. Key Points: The depth of porosity in Mars's crust depends most on the maximum heat flux after pore generationA seismic discontinuity at a depth of 8–11 km, as suggested by InSight, could be interpreted as the depth of porosity in the crustIf pores closed at 8–11 km depth, it indicates pores formed prior to 4 Ga when heat flow was at least 60 mW m−2 [ABSTRACT FROM AUTHOR]

Zircon microcrystals are found in many planetary crustal rocks and nanoscale research on grains from well-characterized impact environments on Earth provide a baseline for reconstructing extreme shock and thermal histories elsewhere. However, using zircon to date large impact events can be challenging given that shock-related isotopic re-setting of U–Pb ratios, when measured at micrometre scale, is often incomplete and difficult to interpret as the underlying Pb migration mechanisms are unclear. To better understand shocked zircon U–Pb systematics, we performed atom probe tomography and electron microscopy with the previous SIMS analyses of two shock metamorphosed Mesoarchean zircon grains from deep (≥ 15 km) beneath the centre of the 2.020 Ga giant Vredefort impact structure. We find evidence of two types of impact-related nanoscale Pb mobility. In one grain, clustering has produced ~ 10 nm diameter bodies of radiogenic Pb, unsupported by U and co-located with Al, with an average 207Pb/206Pb ratio of ~ 0.50 (n = 4); the value extant in the grain at the time of impact. Conversely, nearby nanodomains exhibit randomly distributed radiogenic Pb, U and Al and yield 206Pb/238U dates consistent with 100% loss of pre-impact radiogenic Pb atoms during shock metamorphic processes. Notably, domains with multiple Pb clusters occur within micrometres of domains that experienced 100% Pb loss, precluding a uniform radial pattern of thermally-driven Pb diffusion at the grain scale. These cases of broadly coeval clustering and outward Pb mobility during geologically instantaneous shock metamorphism point to unusually rapid, multi-path diffusion processes within sub-micrometre volumes which, when averaged, yield normally discordant U–Pb dates. The isolation of spatially variable styles of Pb retention and loss at nanoscale amidst classical grain-scale shock microstructures shows promise for recognizing and resolving bombardment histories in planetary crusts using zircon. [ABSTRACT FROM AUTHOR]

Sheath folds recognized on kilometer scale are rare and only described in salt tectonics in seismic data. Here, we present mega‐sheath folds spectacularly imaged in a 3‐D seismic survey in the seismic basement flooring the hyperextended Liwan subbasin in the northern margin of the South China Sea. The sheath folds show eye structures delimited by anastomosing discontinuities. The axial planes of the sheath folds are subparallel to a rift‐related, extensional detachment surface separating hyperextended seismic basement from the syn‐rift sedimentary sequence. The sheath folds as well as the anastomosing discontinuities formed during hyperextension by ductile shearing of the forearc inherited and prestructured metasediments. The ductile shearing eventually resulted in the metasediments derived from midcrust unroofed at the footwall of an extension detachment fault. The discovery of mega‐sheath folds and ductile deformation within the basement conflicts with the general assumption that hyperextended domains are in the brittle field. The new seismic observations show the importance of forearc inherited, prestructured anisotropic basement controlling the crustal rheology during hyperextension. Plain Language Summary: A wealth of research has established the classic crustal model with a strong brittle upper crust and a weak ductile lower crust. The styles of deformation depend on rheological and mechanical properties of the materials and generally exhibit brittle faulting in the upper crust and ductile flow in the lower crust, respectively. However, remarkable changes in the crustal rheology and mechanics can occur in strongly inherited, complex geological settings, which up to date have not been well established. In this study, we present and discuss the occurrence of mappable sheath folds generated under high ductile shear strain in metasediments in the basement, and we decipher the questions of when, how, and in what conditions these structures formed. Our results demonstrate that these mega‐sheath folds formed within a forearc inherited anisotropic basement, and the rocks are derived from midcrustal levels. During hyperextension, they were unroofed in the footwall of a major extensional detachment. Ductile deformation and shearing became responsible for the extreme thinning of the crust. Key Points: Sheath folds in seismic basement flooring the Liwan subbasin developed weak, forearc inherited anisotropic metasedimentsMetasediments derived from midcrust levels were unroofed in the footwall of an extensional detachment fault during hyperextensionCombination of a pure shear and a simple shear regime accounts for the extreme thinning of the crust underneath the Liwan subbasin [ABSTRACT FROM AUTHOR]

High-speed penetrators carrying detection equipment impact planetary bodies at high speeds, and they are therefore buried at depths of up to several meters beneath the surface. During the friction and collision with the crust of the planet, the acceleration of the scientific instrumentation is significantly large. The vibration protection structure for scientific instrumentation is necessary for the reduction of the peak value of the acceleration response and the improvement of the survival rate. In this study, a penetrator with a multilayered energy absorbing structure was developed to improve the survival rate of the penetrator, of which the foam-filled thin-walled structure (FTS) was applied to the penetrating vibration-damping structure. The penetration process of the penetrator into the planetary medium was simulated using the LS-DYNA software platform. The results obtained using empirical formulas and theoretical derivations were compared with the results of the numerical analysis. The reliability of the penetrator limit element model was then verified by conducting an impulse response experiment and simulation. The results suggest that FTS has a positive influence on the isolation impact and energy absorption. Moreover, the vibration isolation effects of nine different FTSs were evaluated with respect to the following six factors: impact isolation efficiency, load efficiency, peak of acceleration, peak impact force, total energy absorption, and specific energy absorption. Furthermore, the design of the damping structure provides an indispensable solution for penetrator detection. [ABSTRACT FROM AUTHOR]

Extensional plate boundaries are segmented by offsets that transfer extension between the ends of adjacent portions of the rift by linkage zones ranging in width from a few tens of kilometers to several hundreds of kilometers. However, the kinematics of linkage zones is poorly constrained as direct observations are difficult to make. Here we combine InSAR, seismicity, and structural geology data from the Afar rift to show that an active linkage zone currently connects the two offset Erta Ale and Tat Ali segments. The overall right‐lateral shear between the segments is accommodated primarily by oblique left‐lateral slip along faults subparallel to the rift segments but an active conjugate fault system with right‐lateral slip is also present. Our results provide the first direct observational evidence that offset rift segments during continental breakup can be linked by a shear zone composed of a conjugate set of oblique slip faults. Key Points: Observations of crustal deformation in the linkage zone between two rift segments in northern Afar, EthiopiaInSAR, seismic, and structural data show oblique slip along faults subparallel to the rift segmentsEvidences of left‐lateral oblique shear within a right‐lateral transfer zone caused by rift segment linkage [ABSTRACT FROM AUTHOR]

• Thermal conductivity and diffusivity of olivine were measured simultaneously by pulse heating method under high pressure. • Fe has a non-linear effect on thermal conductivity of olivine. • Forsterite has a more than twice higher thermal conductivity than other compositions at room temperature. • Polycrystalline olivine shows smaller pressure and temperature dependence than single crystal. • Temperature and iron content largely influence the cooling history of rocky planets. The influence of Fe concentration on heat transport properties of olivine was investigated to understand the cooling history of rocky planets such as Mercury, Mars and asteroids. Thermal conductivity (λ) and thermal diffusivity (κ) were measured simultaneously for olivine polycrystal with different Fe contents (Fo, Fo 90 , Fo 70 , Fo 50 , Fo 31 and Fo 0) up to 10 GPa and 1100 K by a pulse heating method. With increasing Fe in olivine, thermal conductivity of olivine first decreases and then slightly increases. The minimum λ was found to be at composition near Fo 31 ; the absolute λ value of Fo 31 is about 65% lower than that of Fo. Small amounts of Fe in olivine can strongly reduce the thermal conductivity at low temperature; λ value of Fo 90 is about 50% of Fo at room temperature. Thermal conductivities of polycrystalline olivine have smaller absolute values and weaker pressure and temperature dependences, compared with those of natural single crystal olivine determined by previous studies. Heat capacity of Fo 70 and Fo 50 calculated from λ and κ is independent of pressure and is controlled by nearly constant thermal expansion coefficient with increasing temperature. Smaller λ of olivine aggregate with high Fe content would produce a warmer mantle and, in turn, possibly a thicker crust in the Fe-rich Mars, while heat in the Fe-poor Mercury can escape faster than the other terrestrial planets. Olivine-dominant asteroids with high Fe concentration could have longer cooling history and lower thermal inertia on the surface. [ABSTRACT FROM AUTHOR]

Thin, laterally continuous ultramylonites within kilometer‐scale ductile shear zones may control middle to lower crustal strength where deformation is localized. Interconnected phyllosilicate networks are commonly suggested to be the weakest geometry a shear zone can reach, yet fine‐grained polyphase mixtures are commonly found in the cores of high‐strain zones. We study a continental strike‐slip shear zone which deformed granulite facies quartzofeldspathic migmatitic gneisses at retrograde amphibolite to greenschist facies conditions. A brittle feldspar framework and interconnected phyllosilicate networks control the strength of the lower strain protomylonites and mylonites, respectively, whereas the ultramylonites comprise a fine‐grained mixture of the host rock minerals. The localization of strain in ultramylonites demonstrates how fine‐grained polyphase mixtures can be weaker than, and supersede, interconnected phyllosilicate networks with increasing shear strain. This contradicts the common assumption that interconnected layers of phyllosilicates is the weakest state a shear zone can reach. Plain Language Summary: Rocks in Earth's upper crust are brittle, causing tectonic movements on fault planes to occur as earthquakes. With increasing depth, temperature and pressure increase and cause the rock to flow rather than fracture. Based on field and seismological studies, we know that deformation in the deeper crust still occur in localized zones, known as "shear zones," but we do not have a good understanding of the strength of these zones and consequently of the strength of the crust. A long‐held view is that shear zones are weakest when made up of sheet‐like minerals allowing deformation to occur like a deck of cards pushed from its side. We found, however, that the weakest cores of shear zones can surpass this form of weakness and consist of a fine‐grained mixture of several minerals with a range of strengths. We hypothesize that this mixture is weaker than any of its components by themselves. Key Points: Decreasing grain size with increasing strain creates favorable conditions for grain size sensitive creep in midcrustal shear zonesWith increasing strain, interconnected phyllosilicate networks can break down and be supplanted by weaker fine‐grained polyphase mixturesGrain size sensitive creep in fine‐grained polyphase mixtures may govern the rheology of the middle to lower continental crust [ABSTRACT FROM AUTHOR]

The H‐κ method (Zhu & Kanamori, 2000, https://doi.org/10.1029/1999JB900322) has been widely used to estimate the crustal thickness (H) and the ratio of P to S velocities (VP/VS ratio, κ) with receiver functions. However, in regions where the crustal structure is complicated, the method may produce biased results, arising particularly from dipping Moho and/or crustal anisotropy. H‐κ stacking in case of azimuthal or radial anisotropy with flat Moho has been proposed but not for cases with plunging anisotropy and dipping Moho. Here we propose a generalized H‐κ method called H‐κ‐c, which corrects for these effects first before stacking. We consider rather general cases, including plunging anisotropy and dipping interfaces of multiple layers, and use harmonic functions to correct for arrival time variations of Ps and its crustal multiples with back azimuth (θ). Systematic synthetic tests show that the arrival time variations can be well fitted by cosθ and cos2θ functions even for very complex crustal structures. Correcting for the back azimuthal variations significantly enhances H‐κ stacking. We verify the feasibility of the H‐κ‐c method by applying it to 40 permanent stations in various geological setting across the Mainland China. The results show clear improvement after the harmonic corrections, with clearer multiples and stronger stacking energy, as well as more reliable H‐κ values. Large differences in H (up to 5.0 km) and κ (up to 0.09) between the new and traditional methods occur mostly in mountainous regions, where the crustal structure tends to be more complex. We caution in particular about systematic bias when the traditional method is used in the presence of dipping interfaces. The modified method is simple and applicable anywhere in the world. Plain Language Summary: Crustal thickness and crustal VP/VS ratio are important parameters for regional geology and tectonics. We propose a method that corrects for the effect of crustal anisotropy and dipping interface on receiver functions, which results in more reliable estimation of crustal thickness and VP/VS ratio. Synthetic tests and application to real data suggest that this method is powerful and widely applicable. Key Points: We propose a generalized H‐κ method with harmonic corrections on Ps and its crustal multiples in receiver functions (H‐κ‐c method)Correcting for the azimuthal variation of arrival times can significantly enhance the H‐κ stacking and obtain more robust resultsApplication of the method to real data shows clear improvement with large differences in H and κ mostly in mountainous regions [ABSTRACT FROM AUTHOR]

Gravimetric methods are expected to play a decisive role in geophysical modeling of the regional crustal structure applied to geoneutrino studies. GIGJ (GOCE Inversion for Geoneutrinos at JUNO) is a 3‐D numerical model constituted by ~46 × 103 voxels of 50 × 50 × 0.1 km, built by inverting GOCE (Gravity field and steady‐state Ocean Circulation Explorer) gravimetric data over the 6° × 4° area centered at the JUNO (Jiangmen Underground Neutrino Observatory) experiment, currently under construction in the Guangdong Province (China). The a priori modeling is based on the adoption of deep seismic sounding profiles, receiver functions, teleseismic P wave velocity models, and Moho depth maps, according to their own accuracy and spatial resolution. The inversion method allowed for integrating GOCE data with the a priori information and some regularization conditions through a Bayesian approach and a stochastic optimization. GIGJ fits the highly accurate and homogeneously distributed GOCE gravity data with a ~1 mGal standard deviation of the residuals, compatible with the observation accuracy. GIGJ provides a site‐specific subdivision of the crustal layers masses, of which uncertainties include estimation errors, associated to the gravimetric solution, and systematic uncertainties, related to the adoption of a fixed sedimentary layer. A consequence of this local rearrangement of the crustal layer thicknesses is a ~21% reduction and a ~24% increase of the middle and lower crust geoneutrino signal, respectively. The geophysical uncertainties of geoneutrino signals at JUNO produced by unitary uranium and thorium abundances distributed in the upper, middle, and lower crust are reduced by 77%, 55%, and 78%, respectively. The numerical model is available at this site (http://www.fe.infn.it/radioactivity/GIGJ). Key Points: A gravity‐based 3‐D crustal model beneath the Guangdong province (China) was built to predict the geoneutrino signal at the JUNO experimentThe adopted Bayesian method allows for fitting gravimetric observations integrating local prior distribution with regularization conditionsGIGJ fitted GOCE gravity data with a ~1 mGal standard deviation of the residuals, compatible with the observation accuracy [ABSTRACT FROM AUTHOR]

We analyse noise characteristics of spatial and temporal correlation of 260 continuous GPS sites from Crustal Movement Observation Network of China (CMONOC). These data sets were mainly collected between 2010 and 2016, with an average of 6 yr of position time-series. In the functional analysis, a clear regional dependence of seasonal movements has been observed and other significant periodic signals are detected nearby the GPS draconitic period and its harmonics. The distribution of these periodic signals shows a spatial correlation, along with non-negligible local inconsistencies. In the stochastic analysis, impacts of the periodicities on the noise assessment have been investigated and Maximum likelihood estimation is used to study noise properties for deseasonalized residual time-series having the seasonal signals removed and filtered residual time-series having other periodic signals removed further. We demonstrate that for both solutions, the flicker noise is thought to be the dominant time-correlated noise and velocity uncertainties may be underestimated 8–10 times if assuming a pure white noise. Ignoring the periodicities could bias the estimation of noise amplitude, spectral index and velocity uncertainty. After removing the periodic signals, the median flicker noise magnitude shows an average of ∼10 per cent reductions and the noise process shifts closer towards white noise. A correlation between the index variations and RMS variations has been observed, indicating that the index varies more significantly for sites with more periodic signals removed. Besides, the spectral index in the vertical component has a better spatial correlation than that in the horizontal and the spatial distribution of the index of deseasonalized solutions seems to correlate well with the amplitudes of seasonal signals, probably implying common sources of spatial variations of these characteristics. Furthermore, analyses of intersite correlations indicate that the correlation induced from the periodic signals displays a similar pattern to the deseasonalized solutions, confirming that the period pattern is spatially correlated and can induce time-series correlations. Finally, the stochastic processes of the common mode noise are predominantly featured by spatially correlated flicker and white noise over a wide range, consistent with previous results. [ABSTRACT FROM AUTHOR]

The seismic speed and anisotropy are two methods frequently used to image the assembly inside the Earth. We study the crust assembly beneath the Biga Peninsula and the surrounding area in northwest Turkey using the accelerometer and broad-band recordings where short-to-medium period (5–20 s) Love–Rayleigh surface waves are utilized to extract the group-phase speed data (fundamental mode). Single-station and two-station techniques are engaged to understand the detected surface waves for the speed and anisotropy assemblies. The single-station group speeds are inverted in a tomographic approach to attain the 2-D group speed diagrams. The least-squares inversion procedure is utilized to find the speed–depth profiles (1-D) under each grid location. The 1-D results are cooperatively inferred to attain the 3-D appearance of the S -wave speeds below the measured region. This process is reiterated for Love and Rayleigh waves. Isotropic configuration is not sufficient to concurrently describe the present detected Love–Rayleigh surface waves. Vertical transverse isotropic crust assembly is found to better elucidate the detected data showing the Rayleigh–Love discrepancy. Complex arrangement of sills and dykes due to the widespread plutonic and volcanic activity in the region linked to the interaction between the Turkish plate and the African plate (northward subducting) is thought to depict the crust assembly deformations causing the detected long-wavelength vertical transverse isotropy. The mineral orientation within horizontal sills and vertical dykes following the magma flow, which is independent of seismic wavelength, adds to the detected anisotropy. The upper crust vertical transverse isotropy is mostly negative; that is, SV -wave is faster than SH -wave, which is assumed to be due to the existence of dykes. The middle-to-lower crust vertical transverse isotropy is commonly positive; that is, SH -wave is faster than SV -wave, which is assumed to be due to the existence of sills. The two-station analyses operating on cross-correlograms give analogous vertical transverse isotropic results to those of the single-station estimates. [ABSTRACT FROM AUTHOR]

We study the coupling of the force-free magnetosphere to the long-term internal evolution of a magnetar. We allow the relation between the poloidal and toroidal stream functions – that characterizes the magnetosphere – to evolve freely without constraining its particular form. We find that, on time-scales of the order of kyr, the energy stored in the magnetosphere gradually increases, as the toroidal region grows and the field lines expand outwards. This continues until a critical point is reached beyond which force-free solutions for the magnetosphere can no longer be constructed, likely leading to some large-scale magnetospheric reorganization. The energy budget available for such events can be as high as several |$10^{45}\,$| erg for fields of |$10^{14}\,$| G. Subsequently, starting from the new initial conditions, the evolution proceeds in a similar manner. The time-scale to reach the critical point scales inversely with the magnetic field amplitude. Allowing currents to pass through the last few metres below the surface, where the magnetic diffusivity is orders of magnitude larger than in the crust, should give rise to a considerable amount of energy deposition through Joule heating. We estimate that the effective surface temperature could increase locally from |${\sim } 0.1\,$| keV to |${\sim } 0.3\hbox{-}0.6\,$| keV, in good agreement with observations. Similarly, the power input from the interior into the magnetosphere could be as high as |$10^{35}\hbox{-}10^{36}\,$| erg s−1, which is consistent with peak luminosities observed during magnetar outbursts. Therefore, a detailed treatment of currents flowing through the envelope may be needed to explain the thermal properties of magnetars. [ABSTRACT FROM AUTHOR]

Diamond exploration focuses on geochemical analysis of indicator minerals that are more abundant than diamond itself. Among such indicators, low-Cr (Cr2O3 < 1 wt%) garnets from mantle eclogites are problematic since they overlap compositionally with many lower-crust-derived garnets also transported by kimberlite. Misclassification of these garnets may create "false positive" mantle signatures and possible misdirection of exploration efforts. Statistical solutions using major elements in low-Cr garnet (Hardman et al. in J Geochem Explor 186:24-35, 2018) provide improved error rates for the discrimination of low-Cr crustal and mantle garnets recovered from kimberlite. In this study we analysed a large suite of garnets (n = 571) from both crustal and mantle settings, already characterised for major elements, for a wide range of trace elements by laser ablation inductively-coupled plasma mass spectrometry and use these new data along with literature data (n = 169) to evaluate the effectiveness of adding trace elements to garnet-based diamond exploration programs. A new garnet classification scheme, initially using a major-element based filter, uses garnet Sr contents and Eu anomalies to help identify low-Cr garnets that are misclassified using major element methods. Combined with existing methods, our new trace element classifiers offer improvement in classification error rates for low-Cr, crustal and mantle garnets to as low as 4.7% for calibration data. [ABSTRACT FROM AUTHOR]

Abstract This study examines the mineral composition, the diversity of chemical composition along the contact area between the Morasko meteorite fragments (classified as iron meteorite, IAB group), the meteorite crust and the surrounding sediments originating from the young glacial relief of the Morasko Reservoir (N part of Poznan, western Poland). It has been shown that the grains are dominated by quartz and feldspars, which are associated with a ferric or ferric-carbonate matrix. The chemical composition of the matrix varies from high iron (over 98% by weight) and nickel (2–3% by weight) content in the meteorite contact area, to low iron content and nickel deficiency, with an oxygen increase in the outer zone about 2 mm from the meteorite. The microstructure of the contact zone is characterized by uneven cracks and deformations of the skeleton grains as well as sediment matrix. This paper for the first time shows the Morasko meteorite structure in reflected light, giving new perspectives in meteorite outer zone characteristic. Highlights • Diversity of contact area between the Morasko meteorite fragment (IAB) and its outer zone were examined. • The outer zone bears traces of surrounding sediment. • Successful application of reflected light in Morasko meteorite structure observations and characteristic. • Chemical composition of the contact zone reveals oxidation processes associated with weathering. • The contact zone underwent weathering processes in terrestrial conditionsresulted in hematite and goethite formation.. [ABSTRACT FROM AUTHOR]

Abstract Measurements of 189 continuous and 933 campaign-mode Global Positioning System (GPS) stations with 3–16 yr data spans over the Tibetan Plateau reveal contemporary three-dimensional (3-D) crustal deformation during 1999–2016. The Empirical Orthogonal Function method was used to characterize the spatial variations in the surface deformation with distinct seasonal oscillations at the GPS sites in five regions of the Tibetan Plateau. We find that these surface variations are highly correlated with the corresponding mass load signals observed by the Gravity Recovery and Climate Experiment (GRACE) mission. The improved GPS processing strategy used to determine the 3-D velocity field includes maximum likelihood estimation, removal of common mode errors from GPS time series using Principal Component Analysis (PCA), and power law plus white noise stochastic error modeling. We determined the rates of vertical crustal movement by removing GRACE-observed non-tectonic origin load deformation, 2002–2016. The corrected vertical crustal deformation shows that the Himalaya region is uplifting at an average rate of ∼1.7 mm yr−1, and that the northeastern Tibetan Plateau is uplifting at an average rate of ∼1.3 mm yr−1. In addition, the horizontal velocity relative to the stable Eurasian plate and its corresponding dilatation throughout the Tibetan Plateau suggest that tectonic shortening and crustal thickening is occurring at −90 to −80 nanostrain yr−1 in the southern Tibetan Plateau and −30 to −20 nanostrain yr−1 in the northeastern Tibetan Plateau, which could be related to the geologic shortening and elastic strain accumulation. The interior Tibetan Plateau exhibits crustal thinning and block movement along strike-slip faults. Eastward motion of the crust north of the Xianshuihe-Xiaojiang Fault system relative to crust to its south results in shear strain and reflects eastward escape of plastic crustal material in the southeastern Tibetan Plateau. Highlights • Spatial surface seasonal oscillations throughout Tibetan Plateau (TP) are derived. • A 3-D crustal deformation field in TP is established using GPS and GRACE data. • The strain patterns of TP are derived by combining GPS horizontal velocity field. • This study reveals the crust shortening and vertical tectonic deformation of TP. [ABSTRACT FROM AUTHOR]