Planetary and Space Science最新文献

Few laboratory studies have investigated the vapor pressures of the volatiles that may be present as ices in the outer solar system; even fewer studies have investigated these species at the temperatures and pressures suitable to the surfaces of icy bodies in the Saturnian and Uranian systems (<100 K, <10⁻⁹ bar). This study adds to the work of Grundy et al. (2024) in extending the known equilibrium vapor pressures of outer solar system ices through laboratory investigations at very low temperatures. Our experiments with ammonia and oxygen ices provide new thermodynamic models for these species’ respective enthalpies of sublimation. We find that ammonia ice, and to a lesser degree oxygen ice, are stable at higher temperatures than extrapolations in previous literature have predicted. Our results show that these ices should be retained over longer periods of time than previous extrapolations would predict, and a greater amount of these solids is required to support observation in exospheres of airless bodies in the outer solar system.

The Virginid meteoroid streams produce a series of meteor showers active annually during February–May. A certain parent comet is not found but a related association of some showers with near-Earth asteroids was previously established and a cometary origin of these asteroids was suggested. We performed a new search for NEAs belonging to the Virginid asteroid–meteoroid complex. On the base of calculation of orbital evolution of a sample of NEAs and determination of theoretical features of related showers a search for observable active showers close to theoretically predicted ones was carried out. As a result, the predicted showers of 27 NEAs were identified with the showers of the Virginid complex. Revealed association points to a cometary nature of NEAs that are moving within the stream and may be considered as extinct fragments of a larger comet-progenitor of the Virginid asteroid–meteoroid complex.

Investigating the relationship between thermal inertia (TI) and aerosol optical depth (AOD) is significant in giving insights into the seasonality of dust deposition and lifting phenomenon. The present study focuses on establishing a relationship of AOD with TI and different particle sizes over different Martian seasons. Two different Martian landforms (exposed rock and sand dunes) have been used to establish these relationships. TI layer was generated using THEMIS nighttime images for different seasons, whereas Curiosity Rover measured AOD values and Mars Climate database (MCD) visible column dust optical depth were used to derive rover equivalent AOD. An inverse relation was observed between AOD and TI for exposed rock and sand dune regions for all the seasons with low to moderate coefficient of determination (R²⁾. A similar inverse trend was observed between rover equivalent AOD and particle size with R² values ranging from 0.8 in the case of sand dunes (winter) to 0.93 in exposed rock (autumn). The results were further compared within the AOD obtained from orbiter image (HRSC) derived using Shadow method for spring season (Shaheen et al., 2022). The same inverse relation was found within TI having good R² values of 0.61 for exposed rock and 0.76 for the sand dunes. Error estimation using Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Normalized Mean Square Error (NMSE), Fractional Bias (FB), Index of agreement errors was carried out for TI vs. AOD and particle size vs. AOD. Excellent statistical significance was obtained for AOD and particle size, in the case of sand dunes it was 0.96 for autumn and 0.99 in case of exposed rock for spring season, respectively.

We apply a previously developed procedure to characterize galactic cosmic rays (GCRs) at 0.7 A.U. with engineering data coming from the Venus Express mission. The engineering parameters are the Error Detection and Correction EDAC cumulative counters, used for detection and correction of memory errors induced by highly energetic particles. It has already been demonstrated that the slope of this counter measures GCR fluxes using data from Mars Express (1.5 A.U.) and Rosetta (up to 4 A.U.) data. Here, we reproduce these methods using Venus Express EDAC data in order to understand the behavior of GCRs closer to the Sun. We again witness the anti-correlation of EDAC slope with the solar activity and further investigate this procedure. The resulting time-lag between maximum sunspot number and minimum GCRs intensity at Venus is close to one day instead of the expected several months. This work represents one of the first characterization of galactic cosmic rays at small distances to the Sun over a long period of time and further cements the value of using EDAC counters as scientific information.

This study investigated the behaviour of a lunar mare crystalline analog dissolved in molten LiF–NaF at 800 °C for the in situ production of metals as a part of In Situ Resource Utilization (ISRU) research. Molten fluorides have the capability to dissolve metallic oxides, and the Hall-Héroult process uses this kind of media to produce Al from Al₂O₃.The first step was to compare the individual solubility of the main oxides composing the mare lunar soil (SiO₂, Al₂O₃, Fe₂O₃, and MgO) with the solubility of the crystalline analog using Inductively Coupled Plasma – Atomic Emission Spectroscopy (ICP-AES). The species concentration added jointly are lower than the concentration of the same species added separately. Nonetheless, this study showed that LiF–NaF can be used to dissolve the analog with a maximum solubility of 3.9 wt% at 800 °C. Cyclic voltammograms were also used to verify the electroactivity of all oxide species in LiF–NaF, wherein all the main oxides are electroactive except SiO₂ and TiO₂. Then electrolyses on different cathodic substrates were performed at different conditions and the obtained cathodic products were analysed with a scanning electron microscope (SEM) coupled with an energy dispersive spectroscopy (EDS). Despite the non-electroactivity of SiO₂ and TiO₂, they were extracted in an alloyed form through Under Potential Deposition (UPD). Metallic deposition of other metals such as aluminium and titanium was achieved on carbon electrode. Finally, a synthetic mixture made of the different oxide species with the same chemical composition as the simulant, was investigated as a viable substitute for lunar mare soil. Its electrochemical behaviour was identical to the crystalline lunar simulant showing that our original process based on oxides dissolution is not influenced by the amorphous/crystalline state of the raw material.

the outputs of LiF–NaF molten process are not critically influenced by the physical state of the lunar regolith.

A climate model is developed for Earth climate history simulations or snapshots of possible conditions on Earthlike exoplanets. It includes estimates for shortwave and longwave optical thickness based on data from Venus, Earth, and Mars; expressions for atmospheric shortwave absorption and surface convective heat loss; climate feedbacks due to water vapor, ice-albedo, clouds, and lapse rate; and a new model for planetary and surface albedo which takes account of surface cover, Rayleigh scattering, and differing wavelength fractions due to primary spectral class. While somewhat complex, it is still orders of magnitude faster than full-spectrum methods or radiative-convective convergence. The model can be modified for use with tidally locked planets, and is here applied to Proxima Centauri b as an example.

With the mission's completion, India became only the fourth nation in history to successfully perform a soft landing on the Moon and the first nation to land a spacecraft close to the lunar south pole. The purpose of the article is to present a comprehensive review of the Chandrayaan-3 mission (a sequel operation to Chandrayaan-2) to demonstrate complete capabilities in secure lunar landing and exploration on the Moon's surface. It is equipped with a Vikram lander and Pragyan rover. An in-depth review is carried out to discuss the findings of the Chandrayaan-3 mission. The goals of Chandrayaan-3's mission are: (a) to show a safe and soft landing on the surface of the Moon; (b) to showcase roving lunar rover technology; and (c) to carry out in-situ scientific research. The goals are achieved through the lander payloads, which include the Langmuir Probe (LP), Chandra's Surface Thermophysical Experiment (ChaSTE), Instrument for Lunar Seismic Activity (ILSA), and Chandra's Surface Thermophysical Experiment (ChaSTE) to measure thermal conductivity and temperature. For lunar laser-ranging investigations, the space agency NASA has provided a passive Laser Retroreflector Array. The Alpha Particle X-ray Spectrometer (APXS) and the Laser Induced Breakdown Spectroscope (LIBS) are rover payloads that were used to determine the elemental composition close to the landing site. The mission goals are highly accomplished with the successful hop experiment of Vikram on the Chandrayaan-3 mission! As ordered, it raised itself to a height of around 40 cm, turned on its engines, and then made a safe landing between 30 and 40 cm away. To put an end to the controversy, the study finishes with highlights on (a) the significant area of the southernmost polar region of the Moon with latitudes ranging from 60 to 90°S and (b) Shiv Shakti point (coordinates 69.373°S 32.319°E).

We use a customized radiative transfer model to show that sharp ($\sim$10 m resolution) images of the Venus surface can be achieved at night in spectral windows free of CO${}_2$ absorption found between 1.0 and $1.2\mu m$ using a camera at 47 km altitude, just below the planet’s optically thick clouds. This is in spite of the Rayleigh scattering by the dense but still semi-transparent lower atmosphere, and the potential for underlying hazes beneath the clouds. The thermal radiation transmitted directly to the camera forms images of spatially varying surface emissivity and/or temperature at the native sensor resolution, platform stability permitting and under reasonable seeing conditions. Near-isotropic Rayleigh scattering dominates in the $1.0\mu m$ window. Combined with near-Lambertian reflections off the base of the cloud layer, the diffuse light field builds up a background radiance from surface emission averaged spatially out to several 10s of km, i.e., beyond the camera’s field-of-view. At the longer wavelengths (1.1 and $1.18\mu m$ windows), the sub-cloud atmosphere itself partially absorbs (hence less direct light), and therefore weakly emits (hence more background light), but the rapidly decreasing Rayleigh scattering compensates and contrast is maintained. In all cases, we demonstrate that the directly-transmitted surface-leaving radiance from the native sensor resolution element ($\sim$10 m) is a significant fraction of the total radiance, and thus can be detected above the background light. Extending down to the 0.85 and $0.90\mu m$ spectral windows, there is less direct and more background due to the enhanced Rayleigh scattering, but the resulting reduction in contrast can be mitigated by co-adding the $\sim$10 m pixels. This technological advance will open a new era in Venusian geology by enabling discrimination between different surface materials at fine scales. Moreover, potentially active volcanism on our sister planet may be revealed by surface spots that are much hotter than their surroundings.

The surface of Mars preserves a variety of structural and geomorphic features such as wrinkle ridges, graben, lobate scarps, impact basins, paleochannels etc., which owe their origin to endogenic processes of deformation as well as meteorite impacts. Graben, which form in extensional stress regimes, are one of the most common structural features identified on these planetary bodies. Many graben are observed in the Margaritifer Terra, a Noachian (4.1 Ga to 3.7 Ga) highland terrain in the southern hemisphere of Mars; but a detailed structural study of these graben have not been carried out so far. The diverse geomorphology of these graben such as their orientation, planform and disposition make the region interesting for structural geological studies. With an aim to unveil the causes behind the formation of these graben, detailed morphometric analyses, estimation of maximum displacement of the faults, and extension across them (ranging between ∼0.3 and ∼0.8 km), as well as age estimation (minimum ∼1 Ga to maximum ∼3.8 Ga) and correlation with the stratigraphic units are carried out on eleven prominent graben in the Margaritifer Terra. The graben belong to two age clusters: 1) late Noachian–early Hesperian and 2) Amazonian. The age-depth correlation, proximity to chaos and floor-fractured craters, absence of any dominant geographic trend and presence of circular graben together indicate that the graben were formed due to dike emplacement in the area in two distinct phases separated by about 2 Ga. Older graben were formed above dike tops at greater depth (>50 km below the surface) while dikes below the younger graben reached shallower levels (∼4 km below the surface) below the surface. The intrusive activities are local to the Margaritifer Terra region and were possibly not caused by Tharsis and Valles Marineris related deformation.