Gravity Signal Research Articles

Gravimetry and hydrologic data to constrain the hydrodynamics of a karstic area: The Škocjan Caves study case

In this paper we employ a combination of gravity and hydrologic data to constrain a hydraulic model of the Škocjan Caves, an allogenic dominated karstic system in Slovenia. The gravity time-series recorded by a spring-based gravimeter, are carefully analyzed to remove tidal and non-tidal effects and unveil the local hydrologic contribution, which is influenced by the temporary accumulation of water in the cave system during the flood events of the Reka river.We make use of a combined analysis of three large flood events with peak river discharge of about 200, 230 and 300 m3/s, that caused significant water level and gravity variations sensed by the pressure transducer and by the gravimeter. By the integration of hydraulic modelling we study the different coupled gravimetric-hydrologic responses to these flood events: we show that, depending on the peak discharge and duration of the event, different flow conditions are present in the cave system. In addition to the information provided by the pressure transducer, the gravimeter is sensitive to the flow dynamics in a different sector of the cave due to the choice of its location; this configuration helps to better constrain the hydraulic model.Moreover, we find that the autogenic recharge by percolating water can significantly affect the gravity time-series and must be considered in related models. By inclusion of both the hydraulic model outcomes and of the modelling of the autogenic recharge, we are able to better explain the gravity transients during the two smaller magnitude events. In particular, during such events the autogenic contribution produces a transient gravity signal, which is about 4 times larger than the allogenic one, while during the largest flood the allogenic contribution drastically overcomes the autogenic effect by a factor 20.By discussing this case, we prove the potential of terrestrial gravity observation to depict the hydro-dynamics of these complex karstic systems as well as the potential of gravimetry to remotely monitor these storage units.

Transcriptional regulation of MdPIN7 by MdARF19 during gravity-induced formation of adventitious root GSA in self-rooted apple stock

Self-rooted apple stock is widely used for apple production. However, the shallowness of the adventitious roots in self-rooted apple stock leads to poor performance in the barren orchards of China. This is because of the considerable difference in the development of a gravitropic set-point angle (GSA) between self-rooted apple stock and seedling rootstock. Therefore, it is crucial to study the molecular mechanism of adventitious root GSA in self-rooted apple stock for breeding self-rooted and deep-rooted apple rootstock cultivars. An apple auxin response factor MdARF19 functioned to establish the adventitious root GSA of self-rooted apple stock in response to gravity and auxin signals. MdARF19 bound directly to the MdPIN7 promoter, activating its transcriptional expression and thus regulating the formation of the adventitious root GSA in 12-2 self-rooted apple stock. However, MdARF19 influenced the expression of auxin efflux carriers (MdPIN3 and MdPIN10) and the establishment of adventitious root GSA of self-rooted apple stock in response to gravity signals by direct activation of MdFLP. Our findings provide new information on the transcriptional regulation of MdPIN7 by auxin response factor MdARF19 in the regulation of the adventitious root GSA of self-rooted apple stock in response to gravity and auxin signals.

Constraining the Structure under Lunar Impact Basins with Gravity

The lunar gravity field is used to estimate and constrain the depth of mass anomalies under 19 major lunar impact basins. We use radial gravitational spectra, consisting of accelerations computed either per spherical harmonic degree or cumulatively, at surface locations to obtain the distribution of the gravity signal with spherical harmonic degree and, by implication, to the likely depth below the surface. The results provide estimates for the maximum likely depths of the primary component to the mass anomalies under 19 basins. We find that the maximum depths of the primary source of mascon gravity on the lunar nearside are deeper than the depths for those on the farside when South Pole–Aitken (SPA) is excluded. All basin mass anomalies on the lunar nearside are in the mantle. The maximum depth of the primary source of the mass anomalies is <80 km, with the exception of SPA, whose dominant mass signature lies at a maximum depth of >200 km beneath the surface. The upper 20 km under all basins is largely devoid of anomalies, reflecting predominantly mixing and relaxation associated with impact melt combined with ejecta fallback, as well as homogenization associated with post-basin formation impact bombardment. Except for SPA, all basin anomalies merge with the deep interior at ∼150 km or below, indicating the depth penetration of disruption of the density structure of the lunar interior associated with impact bombardment.

Adopting normalized full gradient method for regional‐scale gravity modelling: A case study for Northwestern Iran

AbstractThe normalized full gradient was developed to determine anomalous bodies, such as oil and gas fields or simple geological structures studies. We believe that even in complicated geology, normalized full gradient is practical. We introduce data preprocessing and use step‐by‐step simple‐to‐complicated synthetic tests to develop previous researchers’ ideas for regional‐scale gravity modelling. One of the most important steps of the normalized full gradient is the determination of the N optimum value. We found that prevalent methods such as the standard spectral or maxima method are feasible in simple structures only. So, we have suggested the imaging criteria routine for complicated cases. We trace maximum normalized full gradient responses to detect the normalized full gradient responses at the increasing harmonic numbers as the transition of the extensive part of the anomaly to the sharp part of that. With imaging criteria for the determination of N optimum values, the complicated synthetic test results show the success of the normalized full gradient to understand complicated gravity signals. In the real case, we have studied the Northwestern Iran normalized full gradient model of the Bouguer ground gravity data beneath the seismic profile and prepared a P receiver function depth section to uncover the geometry of the Moho boundary and important interfaces in the crust. We suggest the inferred synthetic model from the Bouguer ground gravity anomaly and P receiver function depth section to normalized full gradient trustworthy test in real cases. According to the synthetic test results, we understand the frame of the normalized full gradient responses in the semi‐real case and truthful responses in the real case. Along with this, we study the second ground gravity profile of Northwestern Iran in a good resolution to uncover the deeper structures. The real case results show the possibility of Moho offset and thinning lithosphere beneath the North Tabriz Fault lithospheric boundary, the possible source of Sahand volcanic centre at the west side of the Moho offset beneath North Tabriz Fault, the deep root of the Sabalan volcanic centre in the lower crust and the lithospheric and asthenospheric wedge with the density contrast beneath Sahand–Sabalan volcanic centres. One of the most important results of our study is the lithosphere–asthenosphere boundary offset and stepped Moho possibility beneath the Talesh Mts next to the South Caspian Basin boundary.

Fast large-scale gravity modeling using a high-order compact cascadic multigrid strategy

A new high-order compact (HOC) cascadic multigrid (MG) strategy is developed for modeling large-scale complex gravity problems on nonuniform rectilinear grids. First, the governing 3D Poisson’s gravitational potential equation is discretized by a novel HOC difference scheme, which allows for Robin boundary conditions to further reduce the computational domain. Then, the resulting asymmetric linear system of equations is solved by a generalized extrapolation cascadic MG (gEXCMG) method augmented with a novel MG prolongation operator. The quartic interpolation and completed Richardson extrapolation assist this MG prolongation operator to produce a good initial guess for the biconjugate gradient stabilized smoother. Two synthetic and SEG/EAGE salt models are examined to verify the presented approach. Results indicate that our algorithm can efficiently and accurately produce the gravity signals for complex geologic models. Moreover, the comparisons with the state-of-the-art algebraic MG solvers demonstrate that our gEXCMG solver offers substantially better efficiency with significantly less memory consumption. Therefore, our newly developed method has the potential for serving as a forward engine in large-scale gravity inversions.

Decades of subsidence followed by rapid uplift: Insights from microgravity data at Askja Volcano, Iceland

In August 2021, Askja volcano in Iceland returned to the spotlight after a sudden onset of rapid uplift followed decades of continuous subsidence. In this study the extended record of microgravity data from Askja between 1988 to 2017 is revisited, and new microgravity data from 2021 and 2022 are introduced, which were collected after the uplift had started. Askja caldera had been steadily subsiding since at least 1984 and was characterised by a net decrease in microgravity, potentially signalling the contraction of its magma chamber or eviction of magma either laterally or to deeper levels. The microgravity data indicate that despite ongoing subsidence between 2017 and early 2021, a significant gravity increase can be detected in the center of the caldera between 2017 and August 2021. This increase may be introduced during – or leading up to – the period of uplift. The new microgravity data also indicate that during the period of 40 cm uplift after August 2021 to fall 2022, gravity changes approach the free-air gradient, suggesting subsurface density decreases as a driving process. This process may relate to the vesiculation of magma previously emplaced in the volcano roots, a change in the hydrothermal system, or replacement of dense basaltic magma with less dense rhyolitic magma, or a combination of these processes. However, uncertainties for this period are elevated and may obscure a gravity signal expected from additional mass accumulation. The timing and high uncertainties of some campaigns make it challenging to be conclusive on the driving process behind the uplift, but future microgravity campaigns could help solve the ambiguity. The study also provides a description of potential pitfalls in microgravity campaigns and recommendations on how the reliability of microgravity data can be improved.

Cell polarity linked to gravity sensing is generated by LZY translocation from statoliths to the plasma membrane.

Organisms have evolved under gravitational force, and many sense the direction of gravity by means of statoliths in specialized cells. In flowering plants, starch-accumulating plastids, known as amyloplasts, act as statoliths to facilitate downstream gravitropism. The gravity-sensing mechanism has long been considered a mechanosensing process by which amyloplasts transmit forces to intracellular structures, but the molecular mechanism underlying this has not been elucidated. We show here that LAZY1-LIKE (LZY) family proteins involved in statocyte gravity signaling associate with amyloplasts and the proximal plasma membrane. This results in polar localization according to the direction of gravity. We propose a gravity-sensing mechanism by which LZY translocation to the plasma membrane signals the direction of gravity by transmitting information on the position of amyloplasts.

EFFECT OF DNA METHYLATION ON GRAVISENSITIVITY OF MOSSES

Gravity is a constant environmental factor in plant growth and development. Real or simulated microgravity causes stress responses in plants, in which DNA methylation is involved. We investigated the effect of the DNA methylation inhibitor 5-azacytidine (5-aza) on the perception and transduction of the gravity signal into gravitropism and on the peroxidase isoenzyme spectra in Physcomitrium patens (Hedw.) Mitt. protonemata under conditions of altered gravity, as well as on Polytrichum arcticum Sw. ex. Brid. phenotype branching and variability of gravitropic angles of lateral branches. The influence of DNA methylation on the perception and realization of the gravity signal was determined. DNA demethylation in the 5-aza presence decreased the gravisensitivity of stolons — less at the stage of perception and more during gravity signal transduction. An analysis of gravitropism under the inhibiton of DNA methylation showed the signal preservation in cell memory regardless of the stage of gravistimulation. However, cell memory about a signal was shorter at the perception stage and longer at the transduction stage, that affects a rate of the gravitropic growth recovery. The different effect of DNA methylation on gravi-induction is considered as an epigenetically regulated process that modifies morphological differences in mosses’ tropismunder under real microgravity in space flight and simulated microgravity on earth. Resistance to microgravity depends on intensity of cell wall metabolism. Peroxidase activity plays an important role in the biogenesis and mechanical stability of the cell wall. It was shown that the changes in the expression of peroxidase genes and enzyme isoforms in the P. patens protonemata may be a result of DNA demethylation. Epigenetic polymorphism of peroxidase under microgravity is regarded as a probable factor of individual resistance of plant organisms.

Detection of time variable gravity signals using terrestrial clock networks

The relativistic redshift between two earth-bound clocks can be interpreted in terms of gravity potential variation between the clock locations. A clock with a fractional frequency uncertainty of 10-18 is sensitive to a gravity potential variation of 0.1 m2/s2 or a height difference of 1 cm. Case studies for four regions affected by different mass change processes - Himalaya, Amazon, Greenland, and Fennoscandia - have been carried out. As the clocks rest on the deformable Earth’s surface, clock observations do not only include potential variations due to mass changes but also associated variations due to the vertical deformation of the land. For the simulations, vertical displacements were derived from real GNSS (Global Navigation Satellite Systems) measurements, and mass variations were computed from GRACE (Gravity Recovery And Climate Experiment) solutions. In the Himalayan region, seasonal variations with a maximum range of -0.20.2 m2/s2 were obtained. There, early and long-lasting precipitation patterns in North-East India and the gradual spreading towards the West can be observed by a dedicated clock network. For the Amazon region, seasonal variations with a maximum range of -0.50.5 m2/s2 observed by clocks also reveals the Amazon’s seasonal properties of annual rainfall variability at the North and South of the equator. The rainy season in the North of the equator is during the summer season from June to August, but from November to April in the South of the equator. The long-term trend of the ice mass loss in Greenland between 2004 and 2015 causes signals of potential variations of 1 m2/s2 that again can clearly be observed by clock measurements. Especially, the higher rates of mass variations in the west and south parts of Greenland can well be observed. The land uplift pattern of Fennoscandia due to the GIA (Glacial Isostatic Adjustment) can also be detected using optical clocks, however, the vertical deformations dominate the signal and not the mass changes. These examples illustrate that terrestrial clock networks can be used in the future as a modern tool for detecting various time-variable gravity signals for understanding the regional/local patterns of the variations and for providing complementary information to other geodetic techniques.

The Case for Future Gravity Science Investigations at Saturn with a Planetary Orbiter

The next phase in the robotic exploration of the Saturnian system will target unresolved questions about the gas giant’s atmosphere, interior, magnetosphere, and rings that were left open by investigations on board the Cassini mission. Among these, we find gravity science objectives, which relate mainly to explaining the origin of the large wind-induced gravity signal and reconciling existing incongruities regarding the internal density distribution. Here we attempt to identify which future observations may yield additional information about Saturn’s internal mechanisms. We report on the results of precise numerical simulations of a gravity science experiment carried out with a planetary orbiter in the 2040s and characterized by varying periapsis altitude over the 1 bar planetary surface. The goal is to identify achievable measurement requirements that can advance the current understanding of Saturn’s interior and atmospheric dynamics. We find that inclined, elliptical orbits with low-altitude closest approaches over the northern hemisphere can improve the present determination of the gravity field coefficients by up to 1 order of magnitude, provided that at least a dozen pericenters are devoted to gravity science. Furthermore, if future observations are combined with the available Cassini Grand Finale data in the southern hemisphere, a significant improvement in terms of maximum measurable gravity field degree is observed.

Hydrological and volcano-related gravity signals at Mt. Somma–Vesuvius from ∼20 yr of time-lapse gravity monitoring: implications for volcano quiescence

SUMMARY We report on about 20 yr of relative gravity measurements, acquired on Mt. Somma–Vesuvius volcano in order to investigate the hydrological and volcano-tectonic processes controlling the present-day activity of the volcano. The retrieved long-term field of time gravity change (2003–2022) shows a pattern essentially related to the subsidence, which have affected the central part of the volcano, as detected by the permanent GNSS network and InSAR data. After reducing the observations for the effect of vertical deformation, no significant residuals are found, indicating no significant mass accumulation or loss within the volcanic system. In the north-western sector of the study area, at the border of the volcano edifice, however, significant residual positive gravity changes are detected which are associated to ground-water rebound after years of intense exploitation of the aquifers. On the seasonal timescale, we find that stations within the caldera rim are affected by the seasonal hydrological effects, while the gravity stations at the base of the Vesuvius show a less clear correlation. Furthermore, within the caldera rim a multiyear gravity transient is detected with an increase phase lasting about 4 yr followed by a slower decrease phase. Analysis of rain data seem to exclude a hydrological origin, hence, we hypothesize a deeper source related to the geothermal activity, which can be present even if the volcano is in a quiescent state. We infer the depth and volume of the source by inverting the spatial pattern of the gravity field at the peak of the transient. A volume of fluids of 9.5 × 107 m3 with density of 1000 kg m−3 at 2.3 km depth is capable to fit reasonably well the observations. To explain the gravity transient, simple synthetic models are produced, that simulate the ascent of fluids from a deep reservoir up to the depth of 2.3 km and a successive diffusion within the carbonate aquifer hosting the geothermal system. The whole process appears to not significantly affect the seismicity rate and the deformation of the volcano. This study demonstrates the importance of a 4-D gravity monitoring of a volcano to understand its complex gravity signals that cover different spatial and temporal scales. Discriminating the different contributions that mix up in the observed gravity changes, in particular those due to hydrologic/anthropogenic activities form those due to the geothermal dynamics, is fundamental for a complete and reliable evaluation of the volcano state.

Geoid model determination for the Hellenic area “Hellas Geoid 2023”

The latest geoid model "HELLAS GEOID 2023" (HG2023) derived by the Hellenic Military Geographical Service is the most comprehensive model for the entire Hellenic area. Long-term gravity data, orthometric and geometric heights, seabed topography and a high-resolution digital terrain model were implemented in the calculations. Data evaluation and their accuracy estimation were of major importance to ascertain compatibility among data sources. In this study, data from neighboring countries were used as they were essential for the completeness of the model developed. The technique remove–compute–restore was adopted for the separation of the gravity signal in the heterogeneous data utilizing EIGEN 6C4 (full degree and order 2190), since the global geodynamic model was found to fit best in the Greek region. Mean gravity residual contribution to the local geoid model was calculated using Stokes' theorem in the frequency domain and implementing the Fourier transform using the Wang and Core modification. The final surface of the resulting gravimetric geoid was adapted to the existing height system of the State utilizing the Least Squares Collocation method by fitting points of known orthometric and geometric heights, distributed throughout Greece. The external accuracy of the estimated geoid model was estimated at the level of 6 cm.

Geodetic/gravimetric evidence for mass loss in the subsidence area of Bandung, Indonesia

Land subsidence monitoring in Bandung, Indonesia, was initiated in the 2000 s. However, the monitoring has been limited to geometric observations only, which may restrict the further physical interpretation of the cause of the subsidence. In this study, we combine geometric and gravity observation methods to monitor surface subsidence in Bandung. 63 Synthetic Aperture Radar (SAR) images from Sentinel-1A covering the period of 2014–2020 were used to estimate the mean surface geometric changes. For the gravity observations, a hybrid gravity configuration that incorporates absolute (2008–2014) and relative (2011–2016) gravity observations were used to estimate the gravity changes. We estimated geometric changes of up to − 160 mm/yr, indicating rapid subsidence in the greater Bandung area. We obtained gravity changes ranging between − 56.7 and 40.1 μGal/yr. Upon subtracting the deformation-induced gravity field from the observed field, we produced a residual gravity field that was presumed to be dominated by the groundwater signal, which was then investigated further. We found that the gravity-derived groundwater signal was mainly negative, indicating subsurface mass loss. We further compared the signal with the modeled gravity effect from deep groundwater observations (1996–2008). The median difference between the observed and modeled groundwater gravity signal was estimated to be 2.8 ± 18.0 μGal/yr or equivalent to 0.08 ± 0.55 m/yr in terms of water height if we set the integration cap and groundwater depth to 1.4 km and 150 m, respectively. The discrepancy can be attributed to modeling (simple geohydrological assumption) and measurement (different observation periods and noise) factors. Nevertheless, both measurements indicate that the mass is decreasing due to groundwater depletion, demonstrating the potential of geometric-gravimetric observations to infer sub-surface mass loss.

Continuous Gravity Observations at Mt. Somma-Vesuvius with a gPhoneX Gravimeter: In-Depth Instrumental Response Characterization and Tidal Model

We report on the results of about 9 months of gravimetric recordings acquired at Mt. Somma-Vesuvius (SV) volcano (Southern Italy) with the new generation relative gravimeter gPhoneX#116 (gPh#116), which is a gravimeter specifically designed for continuous gravity recording. We also present the outcomes of an intercomparison experiment of the gPhone#116 conducted at the J9 gravity observatory in Strasbourg (France). In this intercomparison, we were able to check the scale factor of the meter with a high degree of precision by means of an intercomparison with 2 superconducting gravimeters (SGs) and a FG5-type absolute ballistic gravimeter. Multiple calibration approaches allowed us to validate the manufacturer's original calibration constants to a level of 1% accuracy and 0.1% precision. Moreover, we carried out a comparative study of the noise level of the gPh#116 with respect to the SGs and other spring meters routinely used in both prospecting and time-lapse gravimetry. It turns out that gPh#116 exhibits lower levels at hourly time-scales than other compared spring gravimeters (Graviton, gPhone#054, Scintrex-CG5). It was also possible to carry out a detailed study of the instrumental drift, a crucial topic for reliable monitoring of the long-term gravity variations in active volcanic areas. In fact, a challenge in time-lapse gravimetry is the proper separation of the instrumental variations from real gravity changes eventually attributable to recharge or drainage processes of magma or fluids in the feeding systems of active volcanoes. A negative finding coming out from the intercomparison is that, even when applying the tilt correction, the gravimetric residuals obtained with the gPh#116 are an order of magnitude larger and quite inconsistent with those obtained with co-located superconducting gravimeters. We guess this problem could be overcome by installing the gravimeter on an auto-levelling platform. From the analysis of the gravity records, a reliable tidal gravity model was derived, which we believe will help to improve the accuracy of volcano monitoring, as it will allow appropriate correction of tidal effects for both relative and absolute gravity measurements acquired in the area. Two further interesting elements arose from our study: (1) a peculiar cavity effect of the SV underground laboratory that seems to influence the tilt change; (2) the small residual gravity signals are time correlated with the rainfall peaks and are compatible with gravity decreases induced by increases in soil moisture above the gravimeter.

Signatures of Quantum Gravity in the Gravitational Self-Interaction of Photons.

We propose relativistic tests of quantum gravity using the gravitational self-interaction of photons in a cavity. We demonstrate that this interaction results in a number of quantum gravitational signatures in the quantum state of the light that cannot be reproduced by any classical theory of gravity. We rigorously assess these effects using quantum parameter estimation theory and discuss simple measurement schemes that optimally extract their signatures. Crucially, the proposed tests are free of QED photon-photon scattering, are sensitive to the spin of the mediating gravitons, and can probe the locality of the gravitational interaction. These protocols provide a new avenue for studying the quantum nature of gravity in a relativistic setting.

The Impact of New Accelerometer Transplant Data (ACH) on GRACE Follow‐On Along‐Orbit Inter‐Satellite Laser Ranging Observations and Monthly Time‐Variable Gravity and Mascon Solutions

AbstractGRACE‐D accelerometer data show significant bias jumps since one month after the launch of the GRACE Follow‐On (GRACE‐FO) satellites in May 2018, making them inapplicable for correcting GRACE‐FO products for non‐gravitational accelerations. The GRACE‐FO Science Data System (SDS) compensated this issue by transplanting the GRACE‐C accelerometer data toward that of GRACE‐D. Recently, GRACE‐FO SDS implemented an updated transplant method, used in the latest release of GRACE‐FO data. Here, we examine the impact of updated accelerometer transplant data (ACH) on GRACE‐FO measurements at all levels: (a) Level‐1B inter‐satellite laser ranging residuals measured along satellite orbit, (b) Level‐2 time‐variable gravity solutions from all SDS centers (JPL, CSR, and GFZ), and (c) Level‐3 mascon solutions. We show that inter‐satellite laser ranging residuals are modified at low frequencies below 1 mHz, affecting the along‐orbit analysis of large‐scale time‐variable gravity signals. When mapped into monthly Level‐2 spherical harmonic coefficients of geopotential, the low‐frequency change in inter‐satellite ranging residuals leads to substantial improvement of coefficients associated with resonant orders (i.e., 15, 30, 45, etc.) and C30. We also present an improved SLR‐derived C30 which significantly improves the agreement with updated GRACE‐FO C30 at seasonal and interannual timescales. Moreover, we demonstrate the noise reduction in mass change estimates from new GRACE‐FO Level‐2 data over oceans, Greenland, and Antarctica for all SDS solutions. GRACE‐FO mascon solutions show a moderate change in the updated release. Our comprehensive analyses demonstrate high‐quality estimates of non‐gravitational accelerations by the updated transplant method, resulting in more accurate GRACE‐FO time‐variable gravity and mass change observations.

Remaining non-isostatic effects in isostatic-gravimetric Moho determination—is it needed?

SUMMARY For long time the study of the Moho discontinuity (or Moho) has been a crucial topic in inferring the dynamics of the Earth's interior, and with profitable result it is mapped by seismic data, but due to the heterogeneous distribution of such data the quality varies over the world. Nevertheless, with the advent of satellite gravity missions, it is today possible to recover the Moho constituents (i.e. Moho depth; MD and Moho density contrast; MDC) via gravity observations based on isostatic models. Prior to using gravity observations for this application it must be stripped due to the gravitational contributions of known anomalous crustal density structures, mainly density variations of oceans, glacial ice sheets and sediment basins (i.e. stripping gravity corrections). In addition, the gravity signals related mainly with masses below the crust must also be removed. The main purpose of this study is to estimate the significance of removing also remaining non-isostatic effects (RNIEs) on gravity, that is, gravity effects that remain after the stripping corrections. This is carried out by using CRUST19 seismic crustal model and employing Vening Meinesz–Moritz (VMM) gravimetric-isostatic model in recovering the Moho constituents on a global scale to a resolution of 1° × 1°. To reach this goal, we present a new model, named MHUU22, formed by the SGGUGM2 gravitational field, Earth2014 topography, CRUST1.0 and CRUST19 seismic crustal models. Particularly, this study has its main emphasis on the RNIEs on gravity and Moho constituents to find out if we can modify the stripping gravity corrections by a specific correction of the RNIEs. The numerical results illustrate that the RMS differences between MHUU22 MD and the seismic model CRUST1.0 and least-squares combined model MOHV21 are reduced by 33 and 41 per cent by applying the NIEs, and the RMS differences between MHUU22 MDC and the seismic model CRUST1.0 and least-squares combined model MDC21 are reduced by 41 and 23 per cent when the above strategy for removing the RNIEs is applied. Hence, our study demonstrates that the specific correction for the RNIEs on gravity disturbance is significant, resulting in remarkable improvements in MHUU22, which more clearly visualize several crustal structures.

Constraining the Venus Interior Structure with Future VERITAS Measurements of the Gravitational Atmospheric Loading

The complex dynamics of the Venus atmosphere produces a periodic mass redistribution pattern that creates a time-variable modulation of the gravity field of Venus. This gravity signal depends on the net transport of mass across the globe and on the response of the solid body to the normal loading of its crust imparted by the atmosphere. In this work, we explore the possibility of measuring this phenomenon with VERITAS, a NASA Discovery-class mission. By simulating the gravity science experiment, we explore the possibility of measuring the response of Venus to the atmospheric loading, parametrized by the loading Love numbers (), and assess the dependence of these parameters on fundamental interior structure properties. Using the most recent models of Venus’ interior, we compute the Venus Love numbers in a compressible viscoelastic setting and compare them with the predicted uncertainty of the VERITAS measurements. We show that VERITAS will measure at the 4% level and that this measurement could possibly help to distinguish between different equally plausible interior structure models, especially allowing us to distinguish different rheological laws. We also show that a measurement campaign such as the VERITAS gravity science investigation has the potential of measuring not only at the loading forcing frequency, but also at the tidal frequency, ultimately providing a way to probe the response of the planet at different forcing periods.

Both whole-body rotation and visual flow induce cardiovascular autonomic response in human, but visual response is overridden by vestibular stimulation

While the influence of the vestibular and extra-vestibular gravity signals on the cardiovascular system has been demonstrated, there is little evidence that visual stimuli can trigger cardiovascular responses. Furthermore, there is no evidence of interaction between visual and vestibular signals in autonomic control, as would be expected since they are highly integrated. The present study explored the cardiovascular responses to vestibular and visual stimuli in normal subjects. We hypothesized that the visual stimuli would modify the cardiovascular response to vestibular stimulation, especially when the latter is ambiguous with respect to gravity. Off-Vertical-Axis-Rotation (OVAR) was used to stimulate vestibular and extra-vestibular receptors of gravity in 36 healthy young adults while virtual reality was used for visual stimulation. Arterial pressure (AP), respiratory rate and ECG were measured. The analysis accounted for the respiratory modulation of AP and heart rate (HR). Vestibular stimulation by OVAR was shown to modulate both mean arterial pressure (MAP) and HR, while the visual stimulation was significantly affecting HR modulation, but not MAP. Moreover, the specific visual effect was present only when the subjects were not in rotation. Therefore, visual stimulation is able to modulate the heart rate, but is overridden by vestibular stimulation due to real movement.

Emerging D massive graviton in graphene-like systems

Unlike the fundamental forces of the Standard Model the quantum effects of gravity are still experimentally inaccessible. Rather surprisingly quantum aspects of gravity, such as massive gravitons, can emerge in experiments with fractional quantum Hall liquids. These liquids are analytically intractable and thus offer limited insight into the mechanism that gives rise to quantum gravity effects. To thoroughly understand this mechanism we employ a graphene-like system and we modify it appropriately in order to realise simple -dimensional massive gravity model. More concretely, we employ -dimensional Dirac fermions, emerging in the continuous limit of a fermionic honeycomb lattice, coupled to massive gravitons, simulated by bosonic modes positioned at the links of the lattice. The quantum character of gravity can be determined directly by measuring the correlations on the bosonic atoms or by the interactions they effectively induce on the fermions. The similarity of our approach to current optical lattice configurations suggests that quantum signatures of gravity can be simulated in the laboratory in the near future, thus providing a platform to address question on the unification theories, cosmology or the physics of black holes.