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This work is the third in a series on point mascon lunar gravity models. Point mascon models are computationally-efficient replacements for the standard spherical harmonics gravity models used in astrodynamics applications. Weighted cubed-sphere mascon gravity models are introduced as runtime-efficient alternatives to the spherical harmonics representation that do not impose the extreme memory costs imposed by other interpolated gravity modeling schemes. Localized models for the lunar gravity field are generated using sets of point-mass potentials and referenced to a cubed-sphere grid. Adjacent localized point mascon gravity models are combined using Junkins weighting functions to form a smooth global model. Three demonstration models are generated that reproduce the GRGM1200A lunar gravity model with equivalent fidelity to degree 70, 300, and 550 spherical harmonics truncation levels. The weighted cubed-sphere models are benchmarked for runtime and memory cost against the standard spherical harmonics models and two recently-introduced types of globally-defined mascon models. The benchmarking results show that the weighted cubed-sphere mascon models enable significant runtime improvements with reasonable memory costs, especially when using OpenMP parallelization. Comparing acceleration runtime with spherical harmonics, the degree 300 equivalent weighted cubed-sphere model shows up to a 30-fold speedup with an 89 megabyte memory footprint and the degree 550 equivalent model shows up to a 90-fold speedup with a 170 megabyte memory footprint. Order of magnitude speedups are demonstrated without parallelization. The runtime models and driver code are available online. [ABSTRACT FROM AUTHOR]

Silicic lithologies on planetary surfaces indicate magmatic evolutionary processes in their interiors. The Wolf crater complex within Mare Nubium on the Moon is one such silicic construct associated with a high thorium anomaly. This study integrates morphological, compositional, chronological and gravity anomaly analyses of high‐resolution data from various lunar missions to establish this construct as a silicic volcanic caldera. Lobate flows with steeply sloping fronts indicate that the crater rims comprise high‐viscosity silicic lavas, while the structurally controlled inner crater walls suggest caldera collapse triggered by magma depletion. In the crater rims, low Christiansen Feature position values reaffirm the presence of silicic lithologies, consistent with the low gravity anomaly signature beneath the complex, while spectroscopic data reveal low mafic mineral abundances and negligible hydration features. Chronological analyses yield silicic volcanism ages coeval with surrounding mare basalts (3.8–3.6 Ga), while intra‐caldera basalts have 2.36–2.02 Ga ages, indicating prolonged magmatism in this region. Melting of suitable crustal protoliths like alkali gabbronorite/monzogabbro/troctolite by basaltic underplating is inferred to have generated silicic magmas that formed the Wolf volcanic complex, instead of basaltic magma fractionation or silicate‐liquid immiscibility processes. Large impacts during the Late Heavy Bombardment may have enhanced partial melting of the mantle and created crustal fractures that facilitated the ascent of viscous silicic melts through the lunar crust. Contemporaneous existence of suitable protoliths and adequate crustal pathways for magma ascent may have controlled silicic volcanism on the Moon, and can explain the sporadic occurrence and overlapping ages of the lunar silicic constructs. Plain Language Summary: Understanding how evolved silica‐rich rocks formed on the Moon can shed light on the magmatic differentiation and thermal evolution of the lunar mantle. Here, we study one such silicic region called the Wolf crater complex on the lunar nearside using compositional and morphological evidence from high‐resolution images and remotely sensed data. Spectroscopic and gravity studies confirm that the rocks have a silicic composition but with negligible water content. The complex is characterized as a silicic volcanic crater/caldera that was later filled with basalt. Formation of the volcano and its collapse to form the caldera were controlled by pre‐existing structures. Ages calculated by crater‐counting methods suggest that magmatic activity persisted in this region for ∼2 billion years. These apparently dry silicic melts could not have been derived by fractionation or unmixing of basaltic magmas. Instead, large impacts in the region may have thinned the crust, enhancing partial melting of the underlying mantle and facilitating basaltic underplating of the crust. Melting of appropriate protoliths (alkali gabbronorite/monzogabbro/troctolite), where present in the underplated crust, may generate viscous silicic melts whose ascent is then facilitated by impact‐generated fractures. This model explains why lunar silicic constructs are rare and have ages broadly synchronous with the Late Heavy Bombardment. Key Points: The Wolf crater complex is a volcanic caldera where silicic volcanism occurred between ∼3.6–3.7 Ga, followed by mafic volcanism till ∼2.02 GaStructural trends imposed by regional pre‐existing fracture systems facilitated both melt eruption and caldera collapseNear anhydrous melting of appropriate crustal protoliths caused by basaltic underplating generated the silicic melts [ABSTRACT FROM AUTHOR]

Introduction: Space is a unique environment characterized by isolation from community life and exposure to circadian misalignment, microgravity, and space radiation. These multiple differences from those experienced on the earth may cause systemic and local tissue stress. Autonomic nerves, including sympathetic and parasympathetic nerves, regulate functions in multiple organs. Saliva is secreted from the salivary gland, which is regulated by autonomic nerves, and plays several important roles in the oral cavity and digestive processes. The balance of the autonomic nervous system in the seromucous glands, such as the submandibular glands, precisely controls serous and mucous saliva. Psychological stress, radiation damage, and other triggers can cause an imbalance in salivary secretion systems. A previous study reported that amylase is a stress marker in behavioral medicine and space flight crews; however, the detailed mechanisms underlying amylase regulation in the space environment are still unknown. Methods: In this study, we aimed to elucidate how lunar gravity (1/6 g) changes mRNA expression patterns in the salivary gland. Using a multiple artificial gravity research system during space flight in the International Space Station, we studied the effects of two different gravitational levels, lunar and Earth gravity, on the submandibular glands of mice. All mice survived, returned to Earth from space, and their submandibular glands were collected 2 days after landing. Results: We found that lunar gravity induced the expression of the salivary amylase gene Amy1; however, no increase in Aqp5 and Ano1, which regulate water secretion, was observed. In addition, genes involved in the exocrine system, such as vesicle-associated membrane protein 8 (Vamp8) and small G proteins, including Rap1 and Rab families, were upregulated under lunar gravity. Conclusion: These results imply that lunar gravity upregulates salivary amylase secretion via Rap/Rab signaling and exocytosis via Vamp8. Our study highlights Amy1 as a potential candidate marker for stress regulation in salivary glands in the lunar gravity environment. [ABSTRACT FROM AUTHOR]

The research on particle size classification in lunar microgravity has gradually attracted the attention of scholars. Based on the discrete element method (DEM), this work proposes a double-layer auxiliary screening vibrating screen in the form of intermediate feeding, and takes the screening efficiency and screening time as the evaluation indicators. Firstly, the Helmholtz-Maxwell coil is used to simulate the force of particles under lunar microgravity, which verifies the reliability of the numerical simulation of particles under lunar microgravity based on the discrete element method. Then, the influence of the parameters of each screen on the comprehensive performance of screening was analyzed by a single-factor experiment. Finally, based on the BP (Back Propagation) neural network optimized by genetic algorithm, the evaluation model of screen parameters and screen performance is established, and the multi-objective genetic algorithm is used to optimize the screen parameters combination scheme with excellent performance. An efficient comprehensive model of screening is provided to improve the screening performance and the design of the screen machine under lunar microgravity. [ABSTRACT FROM AUTHOR]

The cone penetration test (CPT) has shown great potential in coming lunar in-situ resource utilization and base construction missions. To investigate the effect of lunar low gravity and special regolith characteristics, a series of miniature cone penetration tests were conducted under lunar gravity, after which the penetration responses and mechanism were analyzed. Properties of the lunar regolith were reproduced by the CUMT-1 simulant, which shows good consistency with the lunar regolith in mineralogy, particle morphology, grain gradation, and mechanical behaviour. Lunar gravity was simulated through the recently developed geotechnical magnetic-similitude-gravity model testing (GMMT) method. The results show that the increase in gravity leads to a nonlinear increase of the penetration resistance, which is more significant at low relative density and is weakened by increasing assemble density and particle irregularity. The evolution of cone index gradient and normalized penetration resistance at lunar gravity was further analyzed, which shows a good agreement with the in-situ results performed by Lunokhod and Apollo missions. Finally, a back prediction of internal friction angle suggests that the gravity-induced stress level promotes an increase in internal friction angle, but the gravity-induced stress gradient suppresses this trend. [ABSTRACT FROM AUTHOR]

The paper presents the main results of our study on the influence of the physiological effects of simulated lunar gravity on cardiorespiratory responses to exercise in humans. Twelve healthy male volunteers aged 19–31 years (M ± SD: 22.5 ± 4.0 years) took part in the study. They were under 14-day head-up bed rest (HUBR) at +9.6° angle relative to the horizon as a model of the physiological effects of lunar gravity. Cardiopulmonary exercise testing (CPET) was performed 7 days before the onset of HUBR and on the next day after the end of the experimental exposure. A three-stage cycle ergometer test with 5-min steps at 125, 150, and 175 W was used as a CPET protocol. Exposure of the subjects to simulated lunar gravity reduced their tolerance to physical load. This was indicated by more pronounced changes for such parameters of the cardiorespiratory system as heart rate, minute ventilation of the lungs, ventilatory equivalents for oxygen and carbon dioxide, as well as a less pronounced increase in oxygen consumption and oxygen pulse during CPET after 14 days of exposure to HUBR. [ABSTRACT FROM AUTHOR]

In the future, when humans build their bases on terrestrial planets and their moons, caves will be the safest place for inhabitation. Large holes, believed to be cave entrances, have been discovered on the Moon, along with small features called "impact melt pits." In the Gravity Recovery and Interior Laboratory (GRAIL) gravity model, which is expressed in spherical harmonics (SH), it is difficult to express the gravity anomaly created by a small empty space below the surface. Nevertheless, we propose that a cave network, akin to an anthill, exists under the impact melt pits discovered on the Moon. This is because we think it is natural to apply a network created by Earth's small caves to the Moon. We obtained accurate Bouguer gravity measurements by calculating regional crustal density using localized admittance of the study area and detected weak gravity (mass deficit) information. By increasing the degrees and order of SH at regular intervals, we estimated the change in gravity at a specific position at high degrees and order, thereby extracting shallow depth information. To validate our method, we compared our results with those of existing studies that analyzed the previously known Marius Hills Hole (MHH) area. The analysis of seven regions in our study area revealed a mass deficit in some impact melt pits in four lunar regions (Copernicus, King, Stevinus, and Tycho). We propose that there is a cave network in this region, indicated by the gravitation reduction in the impact melt pits region. Our results can be useful for the selection of landing sites for future in situ explorations of lunar caves. [ABSTRACT FROM AUTHOR]

Introduction: Space is a unique environment characterized by isolation from community life and exposure to circadian misalignment, microgravity, and space radiation. These multiple differences from those experienced on the earth may cause systemic and local tissue stress. Autonomic nerves, including sympathetic and parasympathetic nerves, regulate functions in multiple organs. Saliva is secreted from the salivary gland, which is regulated by autonomic nerves, and plays several important roles in the oral cavity and digestive processes. The balance of the autonomic nervous system in the seromucous glands, such as the submandibular glands, precisely controls serous and mucous saliva. Psychological stress, radiation damage, and other triggers can cause an imbalance in salivary secretion systems. A previous study reported that amylase is a stress marker in behavioral medicine and space flight crews; however, the detailed mechanisms underlying amylase regulation in the space environment are still unknown. Methods: In this study, we aimed to elucidate how lunar gravity (1/6  g ) changes mRNA expression patterns in the salivary gland. Using a multiple artificial gravity research system during space flight in the International Space Station, we studied the effects of two different gravitational levels, lunar and Earth gravity, on the submandibular glands of mice. All mice survived, returned to Earth from space, and their submandibular glands were collected 2 days after landing. Results: We found that lunar gravity induced the expression of the salivary amylase gene Amy1 ; however, no increase in Aqp5 and Ano1 , which regulate water secretion, was observed. In addition, genes involved in the exocrine system, such as vesicle-associated membrane protein 8 ( Vamp8 ) and small G proteins, including Rap1 and Rab families, were upregulated under lunar gravity. Conclusion: These results imply that lunar gravity upregulates salivary amylase secretion via Rap / Rab signaling and exocytosis via Vamp8 . Our study highlights Amy1 as a potential candidate marker for stress regulation in salivary glands in the lunar gravity environment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Ouchi, Kono, Satou, Kurashima, Yamaguchi, Kimura and Shibukawa.)

We present a method to determine local gravity fields for the Moon using Gravity Recovery and Interior Laboratory (GRAIL) data. We express gravity as gridded gravity anomalies on a sphere, and we estimate adjustments to a background global start model expressed in spherical harmonics. We processed GRAIL Ka‐band range‐rate data with a short‐arc approach, using only data over the area of interest. We determine our gravity solutions using neighbor smoothing constraints. We divided the entire Moon into 12 regions and 2 polar caps, with a resolution of 0.15°×0.15° (which is equivalent to degree and order 1199 in spherical harmonics), and determined the optimal smoothing parameter for each area by comparing localized correlations between gravity and topography for each solution set. Our selected areas share nodes with surrounding areas and they are overlapping. To mitigate boundary effects, we patch the solutions together by symmetrically omitting the boundary parts of overlapping solutions. Our new solution has been iterated, and it has improved correlations with topography when compared to a fully iterated global model. Our method requires fewer resources, and can easily handle regionally varying resolution or constraints. The smooth model describes small‐scale features clearly, and can be used in local studies of the structure of the lunar crust. Plain Language Summary: The gravity field of a planet depends on the density distribution in its interior, and as such, improved knowledge of the gravity field can help in determining the interior structure of the planet. Here, we have analyzed the data from the Gravity Recovery and Interior Laboratory (GRAIL) mission to make local maps of the Moon's gravity field. Standard analysis of GRAIL data has focused on determining global models of the Moon's gravity field, partly because the tools of geophysics that are used to study the Moon's interior make use of such models, which are expressed in what are called spherical harmonics. However, if the data coverage is varying geographically, spherical harmonics are more difficult to determine precisely. We have applied a local method that can more readily handle variations in data coverage. We divided the Moon into 14 separate regions, and determined the optimal solution for each. We evaluated each solution by comparing it with the Moon's topography. GRAIL found that gravity and topography are highly correlated on the Moon, which we will leverage to independently evaluate our solution. We then patched together our separate maps into one global map. Our new model has improved correlations with topography when compared with a standard global model, but it takes fewer computational resources to make. Together with the easy way to handle geographically varying data coverage, this makes our method and model a good alternative to standard models. Our new model is smooth and has a resolution of 0.15°×0.15° (which is 4.5 km by 4.5 km at the equator) and can be used to study the structure of the Moon's crust at small scales. Key Points: We determine 14 local gravity field solutions covering the entire Moon using GRAIL intersatellite range‐rate dataWe patch the local solutions into a global map, which shows no seams, minimizing boundary effectsOur solution has improved correlations between gravity and topography compared to standard global solutions, with less computational effort [ABSTRACT FROM AUTHOR]

Abstract We present a method to determine local gravity fields for the Moon using Gravity Recovery and Interior Laboratory (GRAIL) data. We express gravity as gridded gravity anomalies on a sphere, and we estimate adjustments to a background global start model expressed in spherical harmonics. We processed GRAIL Ka‐band range‐rate data with a short‐arc approach, using only data over the area of interest. We determine our gravity solutions using neighbor smoothing constraints. We divided the entire Moon into 12 regions and 2 polar caps, with a resolution of 0.15°×0.15° (which is equivalent to degree and order 1199 in spherical harmonics), and determined the optimal smoothing parameter for each area by comparing localized correlations between gravity and topography for each solution set. Our selected areas share nodes with surrounding areas and they are overlapping. To mitigate boundary effects, we patch the solutions together by symmetrically omitting the boundary parts of overlapping solutions. Our new solution has been iterated, and it has improved correlations with topography when compared to a fully iterated global model. Our method requires fewer resources, and can easily handle regionally varying resolution or constraints. The smooth model describes small‐scale features clearly, and can be used in local studies of the structure of the lunar crust.

Abstract Orbit determination of probes visiting Solar System bodies is currently the main source of our knowledge about their internal structure, inferred from the estimate of their gravity field and rotational state. Nongravitational forces acting on the spacecraft need to be accurately included in the dynamical modeling (either explicitly or in the form of empirical parameters) not to degrade the solution and its geophysical interpretation. In this study, we present our recovery of NASA GRAIL orbits and our lunar gravity field solutions up to degree and order 350. We propose a systematic approach to select an optimal parametrization with empirical accelerations and pseudo‐stochastic pulses, by checking their impact against orbit overlaps or, in the case of GRAIL, the very precise inter‐satellite link. We discuss how parametrization choices may differ depending on whether the goal is limited to orbit reconstruction or if it also includes the solution of gravity field coefficients. We validate our setup for planetary geodesy by iterating extended lunar gravity field solutions from pre‐GRAIL gravity fields, and we discuss the impact of empirical parametrization on the interpretation of gravity solutions and of their error bars.

Orbit determination of probes visiting Solar System bodies is currently the main source of our knowledge about their internal structure, inferred from the estimate of their gravity field and rotational state. Nongravitational forces acting on the spacecraft need to be accurately included in the dynamical modeling (either explicitly or in the form of empirical parameters) not to degrade the solution and its geophysical interpretation. In this study, we present our recovery of NASA GRAIL orbits and our lunar gravity field solutions up to degree and order 350. We propose a systematic approach to select an optimal parametrization with empirical accelerations and pseudo‐stochastic pulses, by checking their impact against orbit overlaps or, in the case of GRAIL, the very precise inter‐satellite link. We discuss how parametrization choices may differ depending on whether the goal is limited to orbit reconstruction or if it also includes the solution of gravity field coefficients. We validate our setup for planetary geodesy by iterating extended lunar gravity field solutions from pre‐GRAIL gravity fields, and we discuss the impact of empirical parametrization on the interpretation of gravity solutions and of their error bars. Plain Language Summary: We analyze the orbits of the twin GRAIL probes orbiting the Moon in 2012 to determine the lunar gravity field. The frequency shift of radio signals exchanged between GRAIL and Earth antennas, as well as an ultra‐precise inter‐satellite radio link, allow for an accurate determination of the absolute and relative spacecraft trajectories. As these trajectories mainly depend on the internal mass distribution of the Moon, their accurate knowledge provides important information about lunar gravity and internal structure. However, nongravitational forces acting on the probes, for example, caused by radiation from the Sun or the Moon, have to be modeled as well. An explicit modeling of these forces requires an accurate knowledge of spacecraft geometry and optical properties, which are often poorly known. Additional accelerations can be estimated from the data to absorb the effect of nongravitational forces and improve both orbit and gravity field determination. We propose a systematic approach to configure such estimated accelerations when dealing with the recovery of planetary probes' orbits and gravity fields, while also discussing collateral effects of employing them. Based on these findings we also present our independent solution of GRAIL orbits and the lunar gravity field, with a spatial resolution of 31 km. Key Points: We present a systematic approach to assess and select the optimal empirical parametrization for an orbit and gravity field recovery processWe provide an independent solution for the Moon's gravity field up to d/o 350 based on GRAIL Doppler and Ka‐Band Range Rate dataWe describe the planetary extension of the Bernese GNSS Software and its application to planetary geodesy [ABSTRACT FROM AUTHOR]

In the future, when humans build their bases on terrestrial planets and their moons, caves will be the safest place for inhabitation. Large holes, believed to be cave entrances, have been discovered on the Moon, along with small features called “impact melt pits.” In the Gravity Recovery and Interior Laboratory (GRAIL) gravity model, which is expressed in spherical harmonics (SH), it is difficult to express the gravity anomaly created by a small empty space below the surface. Nevertheless, we propose that a cave network, akin to an anthill, exists under the impact melt pits discovered on the Moon. This is because we think it is natural to apply a network created by Earth’s small caves to the Moon. We obtained accurate Bouguer gravity measurements by calculating regional crustal density using localized admittance of the study area and detected weak gravity (mass deficit) information. By increasing the degrees and order of SH at regular intervals, we estimated the change in gravity at a specific position at high degrees and order, thereby extracting shallow depth information. To validate our method, we compared our results with those of existing studies that analyzed the previously known Marius Hills Hole (MHH) area. The analysis of seven regions in our study area revealed a mass deficit in some impact melt pits in four lunar regions (Copernicus, King, Stevinus, and Tycho). We propose that there is a cave network in this region, indicated by the gravitation reduction in the impact melt pits region. Our results can be useful for the selection of landing sites for future in situ explorations of lunar caves.

The lunar mascon basins are characterized by high gravity anomalies and thin crust. Study of the density structure beneath the mascon basins can help to understand the origin of these gravity anomalies and infer their formation and evolution. We propose an efficient forward gravity method based on the 3‐D Gauss‐Legendre quadrature (GLQ) and Fast Fourier Transforms combined with the adaptive discretization strategy to ensure high accuracy. The numerical example demonstrates that computational efficiency is increased by about three orders of magnitude compared to the traditional 3D GLQ method. We employ this forward method in a 3‐D inversion of the gravity data derived from the lunar gravity model GL1500E. The inverted results show prominent high‐density structures (namely, mascons) representing significant mantle uplift and thinned crust beneath most impact basins. Marked low‐density rings surround the mascons. Most of the corresponding low‐density anomalies extend from the near‐surface to the Moho, indicating a thick, low‐density crust. Our density model is consistent with the formation processes of mascons that an impact causes collapse of the transient crater and then the shocked mantle drives mantle flow. The low‐density rings surrounding the mascons may stem from the crust thickening following an impact and extensive fracturing of the crustal column. Plain Language Summary: Mascons (i.e., mass concentration) have been found beneath most of the lunar impact basins. Knowledge of their density distribution is vital for understanding of their structure and evolution. The mass excesses in some impact basins extend from the base of the lunar crust to about 60 km depth and correspond to a density anomaly of up to 400 kg/m3. These mass concentrations are usually surrounded by a ring of low‐density crust. These features are consistent with the hypothesis that the mascons were formed after an asteroid impact and the upwelling mantle material filling the impact crater. This high‐density material produces the mass excess under the impact basins, while the broken crustal material forms the thick low‐density crust around the mascons. Key Points: A highly efficient forward modeling method for gravity calculations is proposed and used in inversionProminent high‐density structures represent significant mantle uplift and thinned crust beneath most of the impact basinsNegative density anomalies around the mascons form outer rings which may be associated with crustal thickening [ABSTRACT FROM AUTHOR]

The article offers information on artificial language in the strict sense of the word in Czech literature. Topics discussed include parody of the poetic language of the nineteenth-century Lumír school; using plentiful poetic and archaic expressions; the magical properties of lunar gravitation; Moon language, encumbered by lexical archaisms, archaisms concerning inflection and poetisms; and also mentions about the compilation of neologisms.

We present our latest high‐resolution lunar gravity field model of degree and order 1200 in spherical harmonics using Gravity Recovery and Interior Laboratory (GRAIL) data. In addition to a model with the standard spectral Kaula regularization constraint, we determine models by applying a constraint based on topography called rank‐minus‐one (RM1). The new models using this RM1 constraint have high correlations with topography over the entire degree range by design. The RM1 models allow the determination of apparent crustal densities at all spatial scales (called effective density) covered by the model, whereas the Kaula‐constrained model can only be used globally up to spherical harmonic degree 700. We find that the effective density spectrum has a smaller slope for the high degrees when compared to the medium degrees. We interpret this as indicative of a global average surface density, as opposed to an ever‐decreasing effective density as one approaches the surface. We use the RM1 models to derive maps of lateral and vertical density variations in the lunar crust. These models allow us to increase the resolution of this analysis compared to previous studies, by increasing the degree range over which to fit theoretical models of vertical density variations, and by decreasing the size of the spherical caps used in a localized analysis. Several regions on the Moon, such as South Pole‐Aitken and Mare Orientale, are distinct from their surroundings in terms of surface densities. The RM1 models are especially valuable in (localized) spectral studies of the structure of the lunar crust. Plain Language Summary: The Gravity Recovery and Interior Laboratory (GRAIL) mission was designed to investigate the Moon's interior structure and advance the knowledge of its history of heat flow by mapping the Moon's variations in its gravity field to high precision. We present new models of the Moon's gravity field (with a resolution of 4.5 km by 4.5 km at the Moon's equator), where we have used information of the Moon's topography. With such models, we can investigate the structure of the crust at all spatial scales, whereas standard models can only be used globally up to lower resolution (on average, 8 km by 8 km at the most). We find indications for a global average surface density, and we present maps of the lateral and vertical density structure of the Moon. Several regions, such as South Pole‐Aitken and Mare Orientale, stand out as having different surface densities from their surroundings. Owing to their high resolution and improved correlations with topography, our models will be especially useful in local studies of the structure of the Moon's crust. Key Points: We apply a special constraint based on topography to determine a high‐resolution lunar gravity field modelOur new model has high correlations with topography over its entire degree rangeWe derive maps for the vertical and lateral density structure of the Moon's crust at high resolution [ABSTRACT FROM AUTHOR]

Owing to different gravities, the same manned lunar rover shows different acceleration properties on the earth and the moon; therefore, it is of great significance for astronauts to be trained on the earth under the condition of the acceleration properties found on the moon. In this article, a novel acceleration imitation method focused on a single wheel is proposed to obtain equivalent acceleration when using the same acceleration driver input under different gravities, and the acceleration imitation algorithm is derived based on a mechanical model of a special metal wheel with a mesh surface. To reduce the complexity and improve the real-time properties of the algorithm, a fitting function for the imitation torque ratio is proposed to adjust the relationship between the acceleration driver input and the driving torque of the wheel. Finally, experiments were conducted to verify the acceleration imitation algorithm, and the results revealed that the wheel with an imitation torque ratio could effectively approximate on the earth the same acceleration experienced by a single wheel of a manned lunar rover on the moon, given equivalent acceleration driver inputs. [ABSTRACT FROM AUTHOR]

The short- and long-term postural effects on the forced expiratory tracheal noise time were studied in a sample of 12 subjects. In contrast to the spirometric parameters, the tracheal forced expiratory noise time does not respond to a short-term change in the body posture from sitting and standing positions to the lying position, as well as to 14-day-long orthostatic hypokinesia in a lying position with a body angle of +9.6°. However, significant multidirectional individual dynamics of the tracheal forced expiratory noise time was observed in all subjects during long-term orthostatic hypokinesia, whereas the spirometric parameters had a dominant growth response. It is assumed that the estimation of the forced expiratory tracheal noise time during long-term orthostatic hypokinesia in lunar gravity simulation may provide useful data in addition to spirometry when assessing the individual lung function dynamics. The dynamics of acoustic parameters, as well as spirometric parameters, during long-term postural effects can be considered as adaptive changes. [ABSTRACT FROM AUTHOR]

Abstract The twin satellite mission Gravity Recovery and Interior Laboratory (GRAIL) aims to recover the lunar gravity field by means of Ka-band ranging observations. In order to exploit the potential of the inter-satellite range variations, absolute position information of the two probes is required. Hitherto, the Graz lunar gravity field models (GrazLGM) relied on the official science orbit products provided by NASA. In this contribution, we present for the first time a completely independent Graz Lunar Gravity Model based on Primary Mission data. The models are resolved up to spherical harmonic degree and order 420. The orbits of the two probes are determined using variational equations following a batch least squares differential adjustment process implemented in the in-house developed software package ORCA (Orbit Re-Construction Application). These orbits are based on S-band radiometric tracking data collected by the Deep Space Network (DSN) and are used for the independent GRAIL gravity field recovery. To reveal a highly accurate lunar gravity field, an integral equation approach using short orbital arcs is adopted to process the Ka-band data, where no regularization or Kaula constraint is applied. The correlation of gravity with lunar topography as well as the Bouguer spectrum of our solutions is comparable to the models officially released by the GRAIL Science Team. [ABSTRACT FROM AUTHOR]

The article discusses oxygen deficiency in the moon's crust. The lunar crust shows evidence of a multitude of reduction processes that led to oxygen deficiency. The author states that the intensity of the sun's radiation and the impregnation of the solids by low-energy protons may have caused hydrogen to combine with oxygen of the silicates to form water, only to escape into the vacuum of space later on. Evidences collected by lunar investigation teams seems to show that considerable melting has occurred early and abruptly, and then subsided quickly.

Scale modelling should be a very useful strategy for the design of lunar structures. Preventing structural damages in the lunar environment is crucial and scale models are helpful to achieve this aim. The size of these models must be scaled to take into account the different gravitational levels. Since the lunar gravity acceleration is about one-sixth of the terrestrial one, it follows that the models on Earth will be very smaller than the prototype to be realized on the Moon. This strategy will represent an opportunity for engineers working on lunar structure design, provided that the errors, both computational and experimental, related to the change of scale are quantified, allowing reliable extension of the physical scale modelling results to the prototype. In this work, a three-dimensional finite element analysis of walls retaining lunar regolith backfill is described and discussed, in order to provide preliminary results, which can guide a future experimental investigation based on physical scale-modelling. In particular, computational errors related to the scale effects are assessed, with respect to a virtual prototype of the lunar geotechnical structure, and compared with errors from other sources of discrepancy, like the adopted constitutive model, the variability of the geotechnical parameters and the calculation section used in the 3D analysis. The results seem to suggest the soundness of this strategy of modelling and are likely to encourage new research, both numerical and experimental, supporting the structure serviceability assessment. [ABSTRACT FROM AUTHOR]

Some large impact basins on the Moon are covered with younger basalts, making it hard to determine their age by crater counting. Evans et al. (2018, https://doi.org/10.1029/2017JE005421) use Gravity Recovery and Interior Laboratory gravity data to identify buried craters larger than 90 km and construct a relative chronology for the impact basins. This relative chronology is broadly consistent with the degree to which the basins have relaxed: Older basins tend to be more relaxed. Pre‐Nectarian basins are likely saturated, so the roughly constant measured crater density does not require a brief formation interval. Some of the results of Evans et al. (2018) are at odds with other determinations; for example, they suggest that Imbrium could be older than Crisium, and Serenitatis as young as Imbrium. Plain Language Summary: To tell the age of an impact basin on the Moon, you count the number of craters. But some basins are flooded by later lavas, making crater counting difficult. Evans et al. (2018) identify buried craters by looking for small changes in the Moon's gravity. This allows them to decide how old each impact basin is. The older basins are also generally shallower. This is because the older basins formed when the Moon was hotter and the lunar rocks were able to flow and partly fill the basin in. Key Points: Evans et al. (2018) use gravity data to identify buried craters within large basinsThey reinterpret the relative ages of lunar basins using these observationsThe relative ages correlate quite well with the degree of basin relaxation [ABSTRACT FROM AUTHOR]

Based on Gravity Recovery and Interior Laboratory (GRAIL) observations and the Lunar Orbiter Laser Altimeter (LOLA) crater database, we constrain the spatial variations in the Moon's crustal porosity (ϕc) to a depth of several kilometers using the gravity anomalies of 4,864 midsized craters (those with a diameter of 20–100 km). For each crater, we estimated the local ϕc by quantifying the gravitational effects of impact‐induced porosity change and postimpact breccia infill. The crustal porosity model was uniquely determined assuming a global mean ϕc of 12%, although a trade‐off exists between the porosity of postimpact breccia infill and the (preimpact) crustal porosity that results in zero net porosity change underlying the crater floor. At this crustal porosity the effects of impact bulking and compaction compensate each other to yield zero crater residual Bouguer anomaly (RBA), when the effect of postimpact infill is excluded. For lower crustal porosities, bulking dominates to produce a negative RBA; for higher crustal porosities, compaction dominates to produce a positive RBA. Spatial kriging and statistical tests suggest lower‐than‐average ϕc in the western nearside maria and southern South Pole‐Aitken (SP‐A) basin, in contrast to higher‐than‐average values in the southwestern periphery of the nearside maria. Most of the large impact basins, presumably formed before the majority of the midsized craters we analyzed, show reduced porosities relative to their immediate surroundings. Plain Language Summary: Because the Moon lacks plate tectonics and surface erosion, its crustal structure has been preserved since the Late Heavy Bombardment ~3.9 billion years ago. The porosity structure of the lunar crust provides critical information on the early cratering history and the formation of major impact basins. Anomalously low crustal porosity implies the existence of relatively young volcanic deposits. In addition, the early porosity evolution of the Moon sheds lights on the origin of life as similar processing acting on the Earth created heat and pore space (as water conduits) to support life on Earth. This study uses 4,864 midsized craters as probes into the internal porosity structure of the lunar crust, which is one of the primary objectives of the Gravity Recovery and Interior Laboratory mission. For each midsized crater, we inverted the observed crater gravity signature for local crustal porosity. We then applied spatial statistical technique to map the regional‐scale variations in the crustal porosity and related the porosity variations with the major geologic units, including the nearside maria, highlands, South Pole‐Aitken basin, and other impact basins. This study shows that midsized craters are useful for detecting regional‐scale porosity structure that has long been established in the lunar evolution history. Key Points: Crater gravity anomalies are useful for constraining spatial variations in the crustal porosityWestern nearside maria and the southern South Pole‐Aitken (SP‐A) basin are associated with relatively low crustal porositySouthwestern periphery of the nearside maria and surroundings of most large impact basins show relatively high crustal porosity [ABSTRACT FROM AUTHOR]

Lunisat represents a next-generation microsatellite aimed at orbiting the Moon, and equipped with dispensers for the release of nanosatellites. This research is focused on the orbital dynamics of both the main microsatellite and the nanosatellites after release. Due to the irregular concentrations of mass in the Moon, low altitude, near-circular lunar orbits are affected by a considerable number of harmonics of the Moon gravitational field. Nonsingular equinoctial orbit elements are employed for orbit propagations, in conjunction with numerical averaging, which is a numerical technique that allows substantial computational improvements. The dynamical model considers a large number of harmonics of the lunar gravitational field, as well as the Earth and Sun perturbing influence as third bodies. Low-altitude lunar satellites turn out to impact the lunar surface after a few weeks or months. In case of an unsatisfactory lifetime, two simple orbit maintenance strategies are evaluated, together with the related propellant budget. Nanosatellites will be released from Lunisat by means of springs. The orbit of each nanosatellite depends on the release conditions, i.e. the relative velocity magnitude and direction. This work investigates the nanosatellite lifetimes as functions of these conditions. Lastly, minimum-time low-thrust transfers for reducing the orbit altitude are investigated, both for nanosatellite release and for the conclusive phase of the Lunisat mission, which finally terminates with the impact on the lunar surface. [ABSTRACT FROM AUTHOR]

It is known from observations of the gravitational field and figure of the Moon that its center of mass (COM) does not coincide with its geometric center, with the line connecting these two points deviating to the Southeast of the direction toward the center of the Earth. The deviation of the lunar COM to the South was explained earlier. Here, the deviation of the lunar COMto the East of the direction toward the Earth is considered. The theory of the optical libration of a satellite orbiting synchronously about a planet for an observer at the secondary (free) focus of the orbit is first refined. It is shown that the main axis of inertia of the satellite undergoes asymmetric, non-linear oscillations whose amplitude is proportional to the square of the orbital eccentricity. A mechanism for the evolution of the orbit has been developed, taking into account the preferred direction of the axis of inertia of the Moon toward the empty focus. Of two alternative scenarios—evolution of the lunar orbit with decreasing or increasing eccentricity—only the latter scenario is consistent with the observed eastward shift of the lunar COM. This mechanism predicts that the lunar orbit had a lower eccentricity in the past than it does today. This conclusion is consistent with the results of observations and also with the fact that the eccentricity of the Moon’s orbit is indeed currently increasing, indicating that it was lower in the past than its current value, e = 0.0549. It is shown by averaging themotion over a rapid variable that thismechanismfor the orbital evolution can explain about 18% of the currently known eastward shift of the lunar COM. The results obtained refine the theory of the tidal evolution of the Moon. [ABSTRACT FROM AUTHOR]

System of Observation of Daytime Asteroids (SODA) is a space mission project, intended to detect and monitor hazardous asteroids approaching the Earth from the Sun direction, namely from the daytime sky. In particular, the SODA mission aims to detect small celestial objects of size about 10 m, approaching the Earth from directions inaccessible to ground-based and near-Earth space-based telescopes, and to inform beforehand whenever a risk of collision with the Earth occurs. The system uses one or two spacecraft launched into the vicinity of the Lagrangian point L1 of the Sun-Earth system, about 1.5 million km from the Earth. This paper considers main aspects of trajectory design for the SODA project at its initial stage. Selection of an orbit about L1 point, transfer from the Earth and stationkeeping in the vicinity L1 are discussed. A launch scheme making use of a lunar gravity assist is proposed to achieve a desired configuration of the two spacecraft. [ABSTRACT FROM AUTHOR]

Low-thrust trajectories about planetary bodies characteristically span a high count of orbital revolutions. Directing the thrust vector over many revolutions presents a challenging optimization problem for any conventional strategy. This paper demonstrates the tractability of low-thrust trajectory optimization about planetary bodies by applying a Sundman transformation to change the independent variable of the spacecraft equations of motion to an orbit angle and performing the optimization with differential dynamic programming. Fuel-optimal geocentric transfers are computed with the transfer duration extended up to 2000 revolutions. The flexibility of the approach to higher fidelity dynamics is shown with Earth’s J2 perturbation and lunar gravity included for a 500 revolution transfer. [ABSTRACT FROM AUTHOR]

Spectrum-Röntgen-Gamma (SRG) is a space observatory designed to observe astrophysical objects in the X-ray range of the electromagnetic spectrum. SRG is planned to be launched in 2019 by a Proton-M launch vehicle with a DM3 upper stage. The spacecraft will be delivered to an orbit around the Sun-Earth collinear libration point L2 located at a distance of ~1.5 million km from the Earth. Although the SRG launch scheme has already been determined at present, in this paper we consider an alternative spacecraft transfer scenario using a lunar gravity-assist maneuver. The proposed scenario allows a oneimpulse transfer from a low Earth orbit to a small-amplitude orbit around the libration point to be performed while fulfilling the technical constraints and the scientific requirements of the mission. [ABSTRACT FROM AUTHOR]

We examine the influence of the lunar gravity model on the orbit determination (OD) of a lunar orbiter operating in a 100 km high, lunar polar orbit. Doppler and sequential range measurements by three Deep Space Network antennas and one Korea Deep Space Antenna were used. For measurement simulation and OD analysis, STK11 and ODTK6 were utilized. GLGM2, LP100K, LP150Q, GRAIL420A, and GRAIL660B were used for investigation of lunar gravity model selection effect. OD results were assessed by position and velocity uncertainties with error covariance and an external orbit comparison using simulated true orbit. The effect of the lunar gravity models on the long-term OD, degree and order level, measurement-acquisition condition, and lunar altitude was investigated. For efficiency verification, computational times for the five lunar gravity models were compared. Results showed that significant improvements to OD accuracy are observed by applying a GRAIL-based model; however, applying a full order and degree gravity modeling is not always the best strategy, owing to the computational burden. Consequently, we consider that OD using GRAIL660B with 70 × 70 degree and order is the most efficient strategy for mission preanalysis. This study provides useful guideline for KPLO OD analysis during nominal mission operation. [ABSTRACT FROM AUTHOR]

The European Space Agency has recently announced to progress from low Earth orbit missions on the International Space Station to other mission scenarios such as exploration of the Moon or Mars. Therefore, the Moon is considered to be the next likely target for European human space explorations. Compared to microgravity (μg), only very little is known about the physiological effects of exposure to partial gravity (μg < partial gravity

We obtain computational expressions for determining the generalized free fall acceleration at any point on the Earth surface depending on the terrestrial, solar, and lunar gravities, height above sea level, season, and diurnal time. The acceleration components due to the solar gravity and the Earth revolution around the Sun take sign-alternating values in the period of 24 hours. The greatest influence of the Sun on the free fall acceleration is in perihelion with the maximal diurnal amplitude of oscillations up to 55.34mGal, while the influence of the lunar gravity is negligible and takes sign-alternating values (up to 3-4mGal). We determine the maximum and minimum values of the acceleration on the Earth surface (983229.81 and 976073.25mGal) and also note the possibility of influence of accelerations due to centrifugal forces on the human organism. [ABSTRACT FROM AUTHOR]

Ballisticly connecting halo orbits to science orbits in the circular-restricted three-body problem is investigated. Two classes of terminal science orbits are considered: low-altitude, tight orbits that are deep in the gravity well of the secondary body, and high-altitude, loose orbits that are strongly perturbed by the gravity of the primary body. General analytic expressions are developed to provide a minimum bound on impulse cost in both the circular restricted and the Hill’s approximations. The equations are applied to a broad range of planetary moons, providing a mission design reference. Systematic grid search methods are developed to numerically find feasible transfers from halo orbits at Europa, confirming the analytical lower bound formulas. The two-impulse capture options in the case of Europa reveal a diverse set of potential solutions. Tight captures result in maneuver costs of 425–550 m/s while loose captures are found with costs as low as 30 m/s. The terminal orbits are verified to avoid escape or impact for at least 45 days. [ABSTRACT FROM AUTHOR]

In this paper, optimal two-impulse Earth-Moon transfers using the lunar gravity assist (LGA) are designed and investigated in the restricted four-body problem (RFBP) with the Sun, the Earth, and the Moon as primaries. Using the double LGA orbit as the initial guess, we propose an optimization method of the Earth-Moon transfer using the LGA in the RFBP. In our design process, the optimization problem in the RFBP is decomposed into several easier optimization subproblems in the easier models to reduce the difficulty of the optimization problem. Then, the optimal LGA transfers are displayed and analyzed. The results indicate that the LGA is an important technique in the Earth-Moon transfer design, which can efficiently save the fuel cost, but the LGA transfer duration must be larger than a period of the Earth-Moon system. [ABSTRACT FROM AUTHOR]

In this paper, transfers from the low Earth orbit (LEO) to libration point orbits using lunar gravity assist (LGA) are proposed and investigated in the Sun-Earth-Moon restricted four-body problem (RFBP). Using the patched LGA orbits as the initial guesses, we present a design method of LGA transfers to libration orbits in the RFBP. The design method is applicable to both prograde and retrograde lunar flyby. Based on the design method, 8 kinds of LGA transfers are obtained. Then, the performances of those LGA transfers, including fuel cost and duration time, are compared and discussed. The analysis results can guide us choose appropriate types of LGA transfers in libration point mission. Finally, LGA transfers are compared with direct transfers based on the Sun-Earth stable manifolds to display the effect of lunar flyby on the transfer. [ABSTRACT FROM AUTHOR]