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Shock experiments are widely used to understand the mechanical and electronic properties of matter under extreme conditions. However, after shock loading to a Hugoniot state, a clear description of the post-shock thermal state and its impacts on materials is still lacking. We used diffraction patterns from 100-fs x-ray pulses to investigate the temperature evolution of laser-shocked Al–Zr metal film composites at time delays ranging from 5 to 75 ns driven by a 120-ps short-pulse laser. We found significant heating of both Al and Zr after shock release, which can be attributed to heat generated by inelastic deformation. A conventional hydrodynamic model that employs (i) typical descriptions of Al and Zr mechanical strength and (ii) elevated strength responses (which might be attributed to an unknown strain rate dependence) did not fully account for the measured temperature increase, which suggests that other strength-related mechanisms (such as fine-scale void growth) could play an important role in thermal responses under shock wave loading/unloading cycles. Our results suggest that a significant portion of the total shock energy delivered by lasers becomes heat due to defect-facilitated plastic work, leaving less converted to kinetic energy. This heating effect may be common in laser-shocked experiments but has not been well acknowledged. High post-shock temperatures may induce phase transformation of materials during shock release. Another implication for the study is the preservability of magnetic records from planetary surfaces that have a shock history from frequent impact events. [ABSTRACT FROM AUTHOR]

The circumstellar liquid-water habitable zone guides our search for potentially inhabited exoplanets but remains observationally untested. We show that the inner edge of the habitable zone can now be mapped among exoplanets using their lack of surface water, which, unlike the presence of water, can be unambiguously revealed by atmospheric sulfur species. Using coupled climate-chemistry modeling, we find that the observability of sulfur gases on exoplanets depends critically on the ultraviolet (UV) flux of their host star, a property with wide variation: Most M-dwarfs have a low UV flux and thereby allow the detection of sulfur gases as a tracer of dry planetary surfaces; however, the UV flux of Trappist-1 may be too high for sulfur to disambiguate uninhabitable from habitable surfaces on any of its planets. We generalize this result to show how a population-level search for sulfur chemistry on M-dwarf planets can be used to empirically define the habitable zone in the near future. [ABSTRACT FROM AUTHOR]

Small organic molecules are essential building blocks of our universe, from cosmic dust to planetary surfaces to life. Compared to their well-known gaseous and liquid forms that have been extensively studied, small organic molecules in the form of ice at low temperatures receive much less attention. Here, we show that supercooled small-molecule droplets can be drawn into highly uniform amorphous ice microfibers with lengths up to 5 cm and diameters down to 200 nm. In the experimental test, these fiber-like ices manifest excellent mechanical flexibilities with elastic strain up to 3.3%. Meanwhile, they can guide light with loss down to 0.025 dB/cm that approaches the material absorption limit and offer high optical nonlinearity for low-threshold supercontinuum generation. Notable temperature-dependent Young's modulus and icing-induced refractive-index increase are also found. These results may open a promising category of low-temperature materials for both scientific research and technological applications. [ABSTRACT FROM AUTHOR]

Meteoritic impacts on planetary surfaces deliver a significant amount of energy that can produce prebiotic organic compounds such as cyanides, which may be a key step to the formation of biomolecules. To study the chemical processes of impact-induced organic synthesis, we simulated the physicochemical processes of hypervelocity impacts (HVI) in experiments with both high-speed 13C60+ projectiles and laser ablation. In the first approach, a 13C60+ beam was accelerated to collide with ammonium nitrate (NH4NO3) to reproduce the shock process and plume generation of meteoritic impacts on nitrogen-rich planetary surfaces. In a complementary investigation, a high-power laser was focused on a mixture of calcium carbonate (CaCO3) and either ammonium chloride (NH4Cl) or sodium nitrate (NaNO3) to induce atomization and enable the study of molecular recombination in the postimpact plume. Additionally, isotopically spiked starting material, namely, Ca13CO3, 15NH4Cl, Na15NO3, and 15NH415NO3, was also employed to disambiguate the source of prebiotic molecule production in the resulting recombination plume. Both experiments independently demonstrated the formation of CN− ions as recombination products, with characteristic mass peak shifts corresponding to the isotopic labeling of the starting material. Yield curves generated from the laser experiments using varying ratios of calcite and NH4Cl or NaNO3 indicate that nitrate enables more efficient production of CN− than ammonium. Thermodynamic software modeling of the laser ablation plume confirmed and further elucidated the experimental yield results, producing good agreement of modeled CN− yield with observed yield curves. These models indicate that the reduction of atomic N from incomplete NH4− atomization during the ablation pulse may have contributed to the lower CN− yield from the ammonia source relative to the nitrate source. The results of these experiments demonstrated that CN−, and by proxy, hydrogen cyanide, and other organic precursor molecules could have formed from carbonate deposits, a previously under-appreciated source of organic carbon for impact-induced organic synthesis. These results have implications for the formation of life during meteoritic bombardment on early Earth as well as for other carbonate-bearing planetary bodies such as Mars and Ceres. [ABSTRACT FROM AUTHOR]

Planetary rover autonomous localization is paramount for a planetary surface exploration mission. However, existing methods demonstrate limited localization accuracy, mostly due to the unstructured texture characterization of planetary surface. In response, this study presents a novel Neural Radiance Field (NeRF) driven visual odometry correction method that allows for high-precision 6-DoF rover pose estimation and local map pruning. First, an innovative image saliency evaluation approach, combining binarization and feature detection, is introduced to meticulously select landmarks that are conducive to rover re-localization. Subsequently, we conduct 3D reconstruction and rendering of the chosen landmarks based on a-priori knowledge of planetary surface images and their Neural Radiance Field (NeRF) models. High-precision odometry correction is achieved through the optimization of photometric loss between NeRF rending images and real images. Simultaneously, the odometry correction mechanism is employed in an autonomous manner to refine the NeRF model of the corresponding landmark, leading to an improved local map and gradually enhanced rover localization accuracy. Numerical simulation and experiment trials are carried out to evaluate the performance of the proposed method, results of which demonstrate state-of-the-art rover re-localization accuracy and local map pruning. • We design a landmark-aware autonomous odometry correction and map pruning method for planetary rovers. • We propose for the first time the deployment of neural radiance field technology and its application in the field of robotics for planetary exploration missions. • We demonstrate the proposed method achieves the state-of-the-art re-localization accuracy through extensive simulations and experiments. [ABSTRACT FROM AUTHOR]

During the final metres of the powered descent of Apollo 11, astronauts Neil Armstrong and Buzz Aldrin lost sight of the lunar surface. As the retro-rockets fired towards the lunar dust – or regolith – to decelerate the spacecraft, soil erosion occurred and the blowing dust led to severe visual obstruction. After a successful landing, the presence of dust continued to impact the mission with adverse effects including respiratory problems and difficulty in performing tasks due to clogging of mechanisms, amongst others. As these effects were observed in subsequent missions, the "dust problem" was identified as one of the main challenges of extra-terrestrial surface exploration. In this work, the focus is placed on dust dispersal, which arises from the interaction between a rocket exhaust flow – or plume – and the planetary surface. Termed plume-surface interactions (PSI), this field of study encompasses the complex phenomena caused by the erosion and lofting of regolith particles. These particles, which are ejected at high-speeds, can lead to damage to the spacecraft hardware or a reduction in functionality. Moreover, plumes redirected back towards the landers can induce destabilising loads prior to touch-down, risking the safety of the landing. To achieve a sustained presence on the Moon, as planned by NASA's Artemis programme, it is essential that PSI are well understood and mitigating measures are put in place, particularly if spacecraft are to land in the vicinity of lunar habitats. Although experimental work began in the 1960s and mission PSI were first recorded in 1969, a fundamental understanding of this phenomena has not yet been achieved. In this paper, a compendium of experimental PSI is presented, identifying the main challenges associated with the design of tests, stating important lessons learnt and the shortcomings of available experimental data and findings. Lastly, recommendations for future experimental work are presented. [Display omitted] • Critical review of plume-surface interactions experimental work. • Retro-propulsive rocket plumes erosion on Lunar and Martian surfaces. • Erosion mechanisms on planetary surfaces. • The challenges and risks of plume-surface interactions. • Evaluation of diagnostic techniques for PSI. [ABSTRACT FROM AUTHOR]

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Current models of chemical evolution during star and planetary formation rely on the presence of dust grains to act as a third body. However, they generally ignore the reactivity of the dust grains themselves. Dust grains present in the protoplanetary phase will evolve as the Solar system forms and, after protoplanets have appeared, they will be constantly delivered to their surfaces in the form of large aggregates or meteorites. Chondritic meteorites are mostly unaltered samples of the dust present in the first stages of the Solar system formation, which still arrive nowadays to the surface of Earth and allow us to study the properties of the materials forming the early Solar system. These materials contain, amongst others, transition metals that can potentially act as catalysts, as well as other phases that can potentially react in different astrophysical conditions, such as FeS. In this work, we present the reactivity of chondritic meteorites under H |$_{2}$| -rich atmospheres, particularly towards the reduction of FeS for the formation of H |$_{2}$| S and metallic Fe during the early phases of the planetary formation. We present the obtained results on the reaction rates and the percentage of FeS available to react in the materials. Additionally, we include a computational study of the reaction mechanism and the energetics. Finally, we discuss the implications of an early formation of H |$_{2}$| S in planetary surfaces. [ABSTRACT FROM AUTHOR]

Dielectric constant for the earth and planetary surfaces has been estimated using reflection coefficients in the past. A recent trend is to use model-based decomposition for dielectric constant retrieval from polarimetric synthetic aperture radar (polSAR) data. We examine the reported literature in this regard and propose a unique dielectric constant estimation (UDCE) algorithm using three-component decomposition technique. In UDCE, the dielectric constant is obtained directly from one of the elements of the measured coherency matrix in a single step. The dielectric constant estimate from the UDCE is independent of the volume scattering model when single-bounce or double-bounce scattering is dominant. This avoids error propagation from overestimation of volume scattering to the copolarization ratios, and in turn, to the dielectric constant, inherent in reported algorithms that use model-based decomposition. Consequently, a unique solution is obtained. We also demonstrate that the solution from the UDCE is unaffected by using a higher-order model-based decomposition. We evaluate the performance of the proposed UDCE algorithm over three Apollo 12, Apollo 15, and Apollo 17 landing sites on the lunar surface using Chandrayaan- 2 dual-frequency synthetic aperture radar (DFSAR) datasets. An excellent convergence rate for dielectric constant estimation is maintained over all three test sites. Using the proposed UDCE algorithm, the dielectric constant maps are produced for the lunar surface using full polSAR data for the first time. We observe that the generated dielectric constant maps capture all the ground truth features, previously unseen with such clarity. [ABSTRACT FROM AUTHOR]

Oxidative weathering is a major source of bio-essential micronutrients on Earth today; however, this flux would have been muted on the early Earth or on Mars, where atmospheric O2(g) levels were very low. Here, we explore the hypothesis that nitrogen oxides generated by lightning in an anoxic atmosphere could have elevated pyrite oxidation levels under otherwise anoxic conditions. We performed spark discharge experiments in the presence of pyrite powder and three different gas mixtures, including 80% N2(g) with 20% CO2(g), 95% N2(g) with 5% CO2(g), and modern air. Experiments were run for 30 min, and we tracked the production of NO(g), dissolved nitrate and nitrite, pH, dissolved sulfate, and total dissolved iron. Our results reveal increasing production of nitrogen oxides with increasing CO2(g) and O2(g) levels, which is consistent with previous studies. Dissolved iron and sulfate also increase, indicating that the nitrogen oxides are able to oxidize pyrite abiotically. Extrapolating these data to global conditions suggests that this mechanism was probably insignificant on a global scale on the early Earth; however, in thunderstorm-prone areas, such as in the modern tropics where lightning rates may locally be over 10 times above the global average, lightning could have rivalled abiotic pyrite oxidation by Archean O2 levels. The lightning contribution would have been highest during time periods with elevated CO2(g), which makes it a potentially important contributor to local release of sulphur, iron, and bio-essential micronutrients on prebiotic land surfaces or on other planets with anoxic CO2-rich atmospheres. [ABSTRACT FROM AUTHOR]

Based on the successful landings of landing modules (LM) on the surface and the introduction of aerostat probes (AP) into the air, the feasibility of exploring Venus by an AP drifting in the cloud layer of its atmosphere using short-term descents and landings on its surface has been substantiated. Mathematical modeling was performed to confirm the feasibility of short-term AP drops with a scientific package (SP) in a thermostatted compartment for sampling soil, aerosols and gases and remote sensing (RS) in various regions remote from each other near the surface of the planet Venus for their analysis during a long drift at the height of the cloud layer. Using the example of individual SP devices for geochemical and geophysical studies of Venusian rocks, the scenario and capabilities of AP are shown, which significantly expand both the range of scientific tasks to be solved and the capabilities of the scientific equipment itself. [ABSTRACT FROM AUTHOR]

To sustainably live on and explore the lunar and other planetary surfaces, in situ regolith will need to be used for resource extraction and infrastructure development. To evaluate and ensure such safety and efficiency of excavation operations in variable, site-specific regolith terranes with given equipment designs, reliable computational models are necessary. The work here evaluates the accuracy and reliability of a standard, well-established excavation force prediction model using published data from a previous planetary excavation experimental study and establishes efficiency metrics for force reduced excavation as a proof-of-concept. It is shown that the established excavation force prediction model is not able to simulate planetary excavation mechanics sufficiently and hence more advanced models of lunar and planetary excavation are needed to enable safer, faster, and more economical resource acquisition hardware development. The case study of the efficiency metrics being applied to the published data shows informative trends that can be used in future excavation hardware and tool path optimizations. These are recommended for use in future planetary excavation modeling and planning workflows. • Current models of excavation mechanics are not sufficient for lunar and planetary excavation analyses. • Extraterrestrial regolith excavation modeling requires reliability not given by current state-of-the-art models. • Metrics of force reduced (e.g., percussive) excavation efficiency have been established, allowing optimization of hardware. [ABSTRACT FROM AUTHOR]

The planetary construction is necessary for long-term scientific deep space exploration and resource utilization in the future. The planetary robotic assembly control is a key technology that must be broken through in future planetary surface construction. The paper focuses on the most representative dual peg-in–hole assembly, which has sufficiently complex contact interaction, wide range of applications and good method portability. To address the challenges brought by the unstructured planetary environment and the features of the construction tasks, the paper proposes an end-to-end deep reinforcement learning and control method with multimodal perception for planetary robotic assembly tasks. A staged reward function based on the visual virtual target point for policy learning is designed. The effectiveness and feasibility of the proposed control method have been verified through simulation experiments and ground real robot experiments. It provides a feasible control method of robotic operations for future planetary surface construction. [ABSTRACT FROM AUTHOR]

Simple Summary: Any species that does not experience certain harmful conditions for an extended period can lose the corresponding protective mechanisms. The search for the organisms with such losses in unusual environments is important to decipher these mechanisms and better understand evolution. Global climate change influences aquatic ecosystems in multiple ways, including shifting water transparency. The latter determines how deep solar ultraviolet can penetrate waterbodies and which species are favored by the change since ultraviolet is lethal for many organisms. Thus, understanding the effects of ultraviolet is important for the management of aquatic ecosystems. Protection against ultraviolet is energetically costly and is known to be reduced in organisms dwelling in dark environments, but most studied species are marine. Lake Baikal is the only freshwater reservoir, where animals adapted to dark deep-water zones in parallel with oceanic counterparts, which makes them unique objects to study parallel evolution. Here, we show that scavenger amphipods (shrimp-like crustaceans) inhabiting different parts of the Baikal deep-water zone partially lost their ultraviolet protection proportionally to preferred depths. Their ultraviolet tolerance was found to be related to the concentration of ultraviolet-screening compounds such as carotenoids. Solar ultraviolet (UV) is among the most important ecological factors shaping the composition of biota on the planet's surface, including the upper layers of waterbodies. Inhabitants of dark environments recently evolving from surface organisms provide natural opportunities to study the evolutionary losses of UV adaptation mechanisms and better understand how those mechanisms function at the biochemical level. The ancient Lake Baikal is the only freshwater reservoir where deep-water fauna emerged, and its diverse endemic amphipods (Amphipoda, Crustacea) now inhabit the whole range from highly transparent littoral to dark depths of over 1600 m, which makes them a convenient model to study UV adaptation. With 10-day-long laboratory exposures, we show that adults of deep-water Baikal amphipods Ommatogammarus flavus and O. albinus indeed have high sensitivity to environmentally relevant UV levels in contrast to littoral species Eulimnogammarus cyaneus and E. verrucosus. The UV intolerance was more pronounced in deeper-dwelling O. albinus and was partially explainable by lower levels of carotenoids and carotenoid-binding proteins. Signs of oxidative stress were not found but UV-B specifically seemingly led to the accumulation of toxic compounds. Overall, the obtained results demonstrate that UV is an important factor limiting the distribution of deep-water amphipods into the littoral zone of Lake Baikal. [ABSTRACT FROM AUTHOR]

Hollows on Mercury are small (hundreds of meters ‐ few kilometers), shallow (tens of meters), irregular depressions typically found in clusters, often associated with impact craters, and likely formed by the loss of volatile materials. While their exact formation process remains debated, various hypotheses suggest sublimation or space weathering. In this study, we analyzed the global distribution of hollows, exploring their spatial patterns and relationships with key geological features. Our findings challenge the idea that hollows arise from a single volatile‐rich surface layer, suggesting instead that volatiles are dispersed throughout the crust. Hollows show no correlation with specific geological units or elevations, indicating no singular volatile source. Moreover, the transitory nature of hollows is suggested as they are rare in older, degraded craters but common in younger ones or older craters with deep‐seated features, hinting at a link to the reworking of materials through impacts or volcano‐tectonic activity. Plain Language Summary: Mercury's surface is widely covered with hollows, that is, small, localized, shallow depressions found on the surface of the planet and often linked to impact craters. We studied the global distribution of hollows and connections with other geological features. We found no evidence for a single layer of volatile materials driving their formation and instead volatiles seem to be scattered throughout the entirety of the exposed crust. Hollows do not seem to have strong ties to specific geological formations or elevation ranges, indicating a complex and/or non unified origin. They also seem to form and disappear quickly, being rare or absent in older, worn‐down craters compared to younger ones. Interestingly, they are more common in fresh craters or older ones with younger pits and tectonic features which suggests that they form when existing materials are disturbed by impacts or volcanic and tectonic activity. This suggests a dynamic relationship between Mercury's surface processes and the formation of these intriguing features. Key Points: We renewed the global database of hollow fields adding 41 new observations for a total of 476Hollows formation is not linked to a singular widespread source layer due to a lack of correlation with specific units or depth rangesHollows are short‐lived features which preferentially form in fresh craters or older craters that are disturbed by reworking [ABSTRACT FROM AUTHOR]

Planetary rovers may become stuck due to the soft terrain on Mars and other planetary surface. The escape entrapment control strategy is of great significance for planetary rover traversing loosely consolidated granular terrain. After analyzing the performance of the published quadrupedal rotary sequence gait, a "sweeping‐spinning" gait was proposed to improve escape entrapment capability. And the forward distance of planetary rovers with "sweeping‐spinning" gait was modeled as a function of six control parameters. An online optimization escape entrapment strategy for planetary rover was proposed based on the Bayesian Optimization algorithm. Single‐factor experiments were conducted to investigate the effect of each control parameter on forward distance, and determine the parameter ranges. The average forward distance with randomly selected control parameters is 89.64 cm, while that is 136.93 cm with Bayesian optimized control parameters, which verifies the effectiveness of the escape entrapment strategy. Moreover, compared with the trajectory of a planetary rover prototype with the published quadrupedal rotary sequence gait, the trajectory of a planetary rover prototype with "sweeping‐spinning" gait is more accurate. Furthermore, the online estimated equivalent terrain mechanical parameters can be used to determine the running state of the planetary rover prototype, which was verified using experiments. [ABSTRACT FROM AUTHOR]

The formation of complex craters requires some form of transient weakening of target rocks. Acoustic fluidization is one proposed mechanism applied in many numerical simulations of large crater formation. In a companion paper, we describe implementing the Melosh model of acoustic fluidization in the iSALE shock physics code. Here, we explore the effect of Melosh model parameters on crater collapse and determine the range of parameters that reproduce observed crater depth‐to‐diameter trends on the Earth and Moon. Target viscosity in the Melosh model is proportional to the vibrational wavelength, λ $\lambda $, and the longevity of acoustic vibrations is ∝λQ $\propto \lambda Q$ (Q $Q$—quality factor). Our simulations show that λ $\lambda $ affects the size of the fluidized region, its fluidity, and the magnitude of the vibrations, producing a variety of crater collapse styles. The size of the fluidized region is strongly affected by the Q $Q$. The regeneration factor, e $e$, controls the amount of (re)generated acoustic energy and its localization. We find that a decrease in e $e$ leads to less crater collapse and that there are trade‐offs between e $e$ and Q $Q$. This trade‐off contributes to the more realistic Q $Q$ values than those used in the Block model. The diffusion of vibrations in regions with high stress and strain is controlled by the scattering term, ξ $\xi $. Compared to the Block model, the Melosh model results in a shallower zone of weakening in complex craters and enhanced strain localization around the crater rim. The parameter set that produces best depth‐diameter trends is λ $\lambda $ = 0.2× ${\times} $impactor radius, Q $Q$ = 10–50, e $e$ = 0.025–0.1, and ξ $\xi $ = 10–105 ${10}^{5}$m2s−1 ${\mathrm{m}}^{2}{\mathrm{s}}^{-1}$. Plain Language Summary: Impact craters are the most common geological features on planetary surfaces. As craters get larger in diameter, they express more complex morphology. Complex crater morphology results from target rocks behaving fluidly upon hypervelocity impact. The rocks behave as fluids because of the temporary reduction in strength, which results from vibrations that remain in the target after the passage of the shock wave. These vibrations cause pressure fluctuations and reduce the rock's strength. This concept is called acoustic fluidization. Here, we explore how vibrations' wavelength, dissipation, scattering, and (re)generation affect crater collapse. Our models show a larger subsurface deformation variety, which the previous simplified model lacked. We determine bounds for each explored parameter, show trade‐offs between them, and their success in reproducing depth‐to‐diameter trends on Earth and the Moon. Key Points: We explore the parameters of the Melosh model of acoustic fluidization (full model) and their effect on crater collapseWe find that the final crater size is a product of the trade‐off between the quality (Q) $(Q)$ and regeneration (e) $(e)$ factors and that vibrational wavelength, λ $\lambda $,affects the style of crater collapseConsidering the full model of acoustic fluidization produces a variety of subsurface deformation in the complex craters lacking in the hitherto applied models [ABSTRACT FROM AUTHOR]

As the limiting element in the development of living systems, it is crucial to understand the history of phosphorus (P), from its stellar origins to its arrival on planetary surfaces. A key component in this cycle is understanding the forms of P delivered to the presolar nebula and their subsequent evolution on planetary bodies, including meteorites. Here, we report on the P distribution in the Bishunpur (LL3.15), Queen Alexandra Range (QUE) 97008 (L3.05), and Allan Hills (ALHA) 77307 (CO3.0) chondrites to determine its origins and secondary processing in the solar protoplanetary disk and on meteorite parent bodies using a coordinated analytical approach. In support of the microstructural characterization, we used density functional theory (DFT) to calculate the Gibbs free energy of the Fe 3 P – Ni 3 P binary under non-ideal mixing conditions in its entire range of composition and temperature space and performed equilibrium condensation modeling. We identified 106 P-bearing regions in these petrologic type-3 chondrites and find that the major P-bearing minerals are schreibersite ((Fe, Ni) 3 P) and merrillite (Ca 9 NaMg(PO 4) 7). Bishunpur predominately contains merrillite, which occurs in rims on chondrules and as hopper crystals. QUE 97008 primarily contains merrillite in association with metal and sulfides. Microstructural evaluation of merrillite in Bishunpur suggests igneous origins within the chondrule-forming region, whereas merrillite in QUE 97008 formed via condensation. In comparison, the dominant P-bearing phase in ALHA 77307 is P-bearing metal, including two Ni-rich schreibersite grains that are composed of 45 and 52.5 at.% Ni, far higher than predicted by equilibrium condensation. The equilibrium thermodynamic model, including our newly described non-ideal schreibersite solid solution, predicts the formation of a miscibility gap where (Fe 0.63 , Ni 0.37) 3 P and Ni 3 P form via nebular condensation. We therefore suggest that Ni-rich schreibersite formed through non-equilibrium condensation. [ABSTRACT FROM AUTHOR]

Liquid-water oceans likely underlie the ice shells of Europa and Enceladus, but ocean properties are challenging to measure due to the overlying ice. Here, we consider gravity-driven flow of the ice shells of icy satellites and relate this to ocean freeze and melt rates. We employ a first-principles approach applicable to conductive ice shells in a Cartesian geometry. We derive a scaling law under which ocean freeze/melt rates can be estimated from shell-thickness measurements. Under a steady-state assumption, ocean freeze/melt rates can be inferred from measurements of ice thickness, given a basal viscosity. Depending on a characteristic thickness scale and basal viscosity, characteristic freeze/melt rates range from around O(10 |$^{-1}$|⁠) to O(10 |$^{-5}$|⁠) mm/yr. Our scaling is validated with ice-penetrating radar measurements of ice thickness and modelled snow accumulation for Roosevelt Island, Antarctica. Our model, coupled with observations of shell thickness, could help estimate the magnitudes of ocean freeze/melt rates on icy satellites. [ABSTRACT FROM AUTHOR]

Mercury's surface undergoes large temperature gradients between day and night, which repeats periodically over the same longitudes due to its 3:2 spin‐orbit resonance. This effect combined with the orbit's eccentricity, creates hot and cold geographic longitudes. The planet is covered with a highly porous regolith, allowing exospheric atoms to diffuse in depth. By using a 1‐D diffusion model, we studied the subsurface precipitation of gas over the cold and hot longitudes to understand gas retention. This work identifies the cold longitudes as favorable regions to form subsurface reservoirs closer to the surface. Moreover, subsurface reservoirs of adsorbates increase two to three times faster over cold longitudes than over hot longitudes, depending on the surface binding energy distribution of the atoms. We suggest that this result may be related to the observation that Mercury's sodium exosphere persists at later local times over the cold pole. Plain Language Summary: The surface of Mercury experience large temperature differences between day and night, and this repeatedly occurs over the same geographic positions as an orbit of the planet around the Sun lasts exactly one and half Mercury day. Additionally, Mercury's orbit is highly elliptic, causing the planet‐Sun distance to vary. This creates cold and hot geographic longitudes on the planet surface. Mercury's surface is porous and covered with very fine grains which allows gas to diffuse through it. By using a one dimensional model, we study how gases can penetrate Mercury's surface depending on the geographic position. We identify that colder regions are favorable to the formation of shallow gas reservoirs, which grow two to three times faster than over the hottest regions, depending on the gas‐surface interactions. This result may be related to the higher measurements of sodium over the cold geographic longitudes of Mercury, which last through each local afternoon. Key Points: Subsurface diffusion of sodium forms shallow reservoir in the first meter of regolith, which is denser at the cold longitudesGreater surface binding energies increase the amount of sodium retained in the regolith per synodic cycleConvergence of the sodium accumulation should happen on timescales of billions of years, which could lead to the saturation of the regolith [ABSTRACT FROM AUTHOR]

Mercury has a large loss cone difference in its two hemispheres due to the northward shifted magnetic dipole. The precipitation difference of energetic electrons in both hemispheres is poorly understood. We show that the northern precipitation is 2.5‐times higher than for a symmetric loss cone due to the effects of the enhanced whistler instability at the southern hemisphere with the larger loss cone. Simulations including nonlinear pitch angle scattering by the whistler‐mode waves show rapid (tens of milliseconds) electron flux modulation related to the wave subpacket structures by repeated interactions within a discrete wave element. The difference in the nonlinear whistler instability in the two hemispheres should enhance the electron precipitation, which, along with the direct impact effects of solar wind, contributes to Mercury's surface–magnetosphere coupling. Electrons hitting the planet's surface may be a possible factor in the formation of water through the formation of hydroxyl groups. Plain Language Summary: Mercury, the first planet from the Sun, has north–south asymmetric magnetic fields due to the northward shifted magnetic dipole from the planet's center. Computer simulations of plasma waves and electrons, taking into account Mercury's magnetic dipole offset, show that the northward precipitation of electrons is 2.5‐times higher than in the case of no magnetic dipole offset, which is the case like the Earth. This difference in electron precipitation fraction arises from a difference in the characteristics of wave growth due to the spatial characteristics of the planet's magnetic field, because plasma waves can efficiently push trapped electrons in Mercury's magnetosphere toward the planet's surface. This study contributes to the understanding of the electron precipitation fraction on Mercury and may help to estimate the production of water ice through the formation of hydroxyl groups not only by the direct impact of solar wind but also by the electron precipitation caused by plasma waves. Key Points: Whistler‐driven electrons at Mercury are simulated, as the electron precipitation on the planet surface may contribute to water productionFor an asymmetric (southward wider) loss cone, the northward precipitation fraction is 2.5‐times higher than for a symmetric loss coneRapid (tens of milliseconds) electron flux modulations can be observed as a signature of repeated interactions with wave subpackets [ABSTRACT FROM AUTHOR]

Thiophene and two derivatives (2-methylthiophene and 3-methylthiophene) have been detected on the surface of Mars with the Sample Analysis at Mars instrument suite onboard NASA's Curiosity rover. Thiophene could serve as a secondary chemical biosignature since the secondary biosynthesis of thiophene is considered an important production pathway. However, it is critical to understand the abiotic formation and destruction of thiophene and its derivatives since these pathways could affect the molecules' stabilities on planetary surfaces over geological timescales. Here, we present the radiolytic destruction kinetics of thiophene, 2-methylthiophene, and 3-methylthiophene as single-component ices and when diluted in water ice at low temperatures. Using infrared spectroscopy, we determined the destruction rate constants and extrapolated our radiolytic half-lives to the surface of Mars, assuming the measured and modeled surface dose rates. We found that our rate constants strongly depend on temperature and presence of water ice. Based on our determined radiolytic half-life for thiophene under conditions most similar to those of thiophene groups in Martian macromolecules, we expect thiophene to be stable on the surface for significantly longer than the Martian surface exposure age of sites in Gale crater where thiophenes have been detected. [ABSTRACT FROM AUTHOR]

As part of MIT's work with the Resources Exploration and Science of OUR Cosmic Environment (RESOURCE) project, in collaboration with NASA Ames and the Solar System Exploration Research Virtual Institute, we investigated the scientific and operational utility of a virtual reality (VR) environment for local, small-scale (<5 m) geological analysis in Lunar and planetary surface exploration missions. A user study was conducted where users explored real environments from Svalbard, Norway, represented in both VR and desktop applications, with the environments mirroring three field sites exhibiting geologic features found on both Earth and Mars. The study aimed to achieve four main objectives: 1) to evaluate if VR improves users' sense of scale, 2) to assess if VR facilitates easier identification of patterns and continuous features, 3) to determine if VR provides a more intuitive method for geological contextualization, and 4) to investigate if VR reduces workload during site exploration. The study, approved by MIT's Institutional Review Board, involved three stages: user training, testing without tools, and geological surveying with tools and fact sheets. Metrics included sense of scale improvement, ease of pattern identification, intuitive geological contextualization, and workload reduction, assessed through questionnaires and the NASA Task Load Index (NASA-TLX). Twenty subjects participated, with tasks randomized across VR and desktop applications. Drone-collected photogrammetry, and environmental data (temperature, humidity and pressure) were collected in Svalbard, Norway, from three distinct geological sites near Longyearbyen. Each site included a water-indicating feature and variation in scale from sub-centimeter to multi-meter. Our comparative study revealed that the VR application provided users with a better sense of scale, improved ability to contextualize geological features, and reduced workload compared to the desktop application. However, while the VR environment enhanced geological contextualization, it showed no significant improvement in the identification of high-level features. We discuss influencing factors for these results and implications for future VR development in geological exploration and astronaut training. • Lessons learned in developing virtual environments for planetary surface exploration and astronaut training. • Field expedition to Svalbard, Norway to collect 3D imagery and environmental sensor data of Mars-relevant geology. • Development of a virtual environment for geological surface exploration of a planetary surface. • User study comparing virtual reality to a desktop application for geological exploration and astronaut training. • Demonstration of improved capabilities using virtual reality for space exploration as a geological field training tool. [ABSTRACT FROM AUTHOR]

In order to improve the effects of predictive maintenance for wind turbine drive chain, the accurate diagnosis of the initial failure of planetary wheel system is particularly important. In this study, for the extraction and analysis of planetary wheel system fault features, fast spectral kurtosis and envelope demodulation methods were used to explore effective fault diagnosis pathways. The key fault features were successfully extracted by fast spectral kurtosis analysis and envelope demodulation of the vibration signal. The analysis results show that the changes of frequency components at different time points reveal the development process of the fault,that is, the fault gradually evolves from the initial characteristics of the gear ring to the characteristics of the planetary wheel, and finally leads to the spalling of the tooth surface of a planetary wheel. In this process, the obvious changes in the localized fault characteristic frequency of the toothed ring and the planetary carrier rotation frequency components provide important clues for the fault development. Based on the evolution of the failure characteristics, an early warning is proposed to be carried out on the 34th day before the failure occurs, namely, an increase in the distribution of the planetary wheel rotation frequency components. Accordingly, timely maintenance measures can be taken to prevent further deterioration of the failure. In summary, this study provides an effective method for early fault diagnosis of planetary wheel systems and theoretical support for fault early warning. [ABSTRACT FROM AUTHOR]

The terrestrial planetary bodies display a wide variety of surface expressions and histories of volcanic and tectonic, and magnetic activity, even those planets with apparently similar dominant modes of heat transport (e.g., conductive on Mercury, the Moon, and Mars). Each body also experienced differentiation in its earliest evolution, which may have led to density‐stabilized layering in its mantle and a heterogenous distribution of heat‐producing elements (HPE). We explore the hypothesis that mantle structure exerts an important control on the occurrence and timing of geological processes such as volcanism and tectonism. We numerically investigate the behavior of an idealized model of a planetary body where HPE are assumed to be sequestered in a stabilized layer at the top or bottom of the mantle. We find that the mantle structure alters the patterns of heat flow at the boundaries of major heat reservoirs: The mantle and core. This modulates the way in which heat production influences geological processes. In the model, the mantle structure is a dominant control on the relative timing of fundamental processes such as volcanism, magnetic field generation, and expansion/contraction, the record of which may be observable on planetary body surfaces. We suggest that Mercury exhibits characteristics of shallow sequestration of HPE and that Mars exhibits characteristics of deep sequestration. Plain Language Summary: The surfaces of Mercury, the Moon, and Mars record information about the history of volcanism, global expansion and contraction, and magnetic field generation experienced by each body. These three bodies also underwent differentiation shortly after they formed, possibly resulting in distinct layers within their mantles as well as preferential sequestration of the radioactive heat‐producing elements (HPE) primarily in one layer. We delve into the hypothesis this layering plays a pivotal role in determining when geological processes such as volcanic eruptions and global expansion and contraction can occur. We use numerical models to simulate heat transport processes in a simplified planet with the HPE sequestered in a stabilized layer either at the top or the bottom of the mantle. We find that layering in the mantle and sequestration of HPE change the way that a planet's mantle exchanges heat with the planet's core and the surface, influencing the relative timing of volcanic activity, global tectonics, and magnetic field generation, all of which can leave observable imprints on planetary surfaces. We propose that Mercury's geological history is consistent with HPE locked into a layer at the top of its mantle, whereas the geological history of Mars is consistent with a deeper distribution. Key Points: The distribution of heat‐producing elements (HPE) within a planetary mantle controls the relative timing of volcanism, tectonism, and magnetismThe geological histories of the Moon and Mars are consistent with deep sequestration of HPEThe geological history of Mercury alternatively suggests shallow sequestration of HPE [ABSTRACT FROM AUTHOR]

Crater counting is a widely applied methodology for dating large areas of planetary surfaces, but is difficult to apply the method to constrain the durations of stratigraphic unconformities. Unconformities with exhumed craters are thought to indicate long hiatuses that can only be indirectly dated through stratigraphic relationships with other surfaces with uniform exposure ages. On Mars, sedimentary deposits with prominent unconformities with exhumed craters are found in layered deposits in the Arabia Terra region as well as Gale crater within Mount Sharp. In this work, we present a Linear Crater Counting methodology and apply it to constrain these unconformities observed in Arabia Terra and in Mount Sharp. The method applies a linear sampling domain correction to conventional two‐dimensional crater size frequency distributions and Bayesian Poisson process statistics in order to constrain the likely durations of these unconformities. We found that unconformities in Arabia Terra were on the order of 0.1–1 Gyr in length and that the unconformity preserved at Mount Sharp is at least 0.2 Gyr in length given estimates of the ages of the host craters. Hiatuses of these lengths constrain the age of the overlying deposits to be Late Hesperian or Amazonian in age. Two utility plots are also provided, along with the derivation, for researchers to apply this method to dating arbitrary geologic contacts on Mars and to adapt it to other bodies. Plain Language Summary: The crater counting method is a widely used method to date planetary surfaces. Crater counting works by comparing the number of craters in an area to the expected number of craters that should be observed for that area using a model of how many craters form and their expected size through time. On Mars, geologic contacts of sedimentary deposits with exhumed craters are seen in Arabia Terra and in Gale crater in Mount Sharp. Craters exhumed in these geologic contacts are thought to indicate long gaps in time between the formation dates of the upper and lower rock layers. However, dating these time gaps directly is not possible with conventional crater counting. To solve this problem, we developed a new linear crater counting method which describes the likely number of craters for a given age that could be found along a line on the surface of Mars. We apply this method to the geologic contacts seen in Arabia Terra and in Gale crater, and find that the time gaps are hundreds of millions of years in length to over a billion years in length. Our results confirm predictions that these deposits are geologically younger than previously thought. Key Points: We describe a novel linear crater counting method to date stratigraphic unconformities using partially exhumed craters along unit boundariesWe found that layered deposits in Arabia Terra and the Upper mound unit in Gale crater could be Amazonian in Age from applying our methodOur methodology can be applied broadly to better understand chronostratigraphy across the solar system [ABSTRACT FROM AUTHOR]

Vegetation can modify the planetary surface albedo via the Charney mechanism, as plants are usually darker than the bare surface of the continents. We updated ESTM (Earth-like surface temperature model) to incorporate the presence, distribution and evolution of two dynamically competing vegetation types that resemble grasslands and trees (the latter in the double stages of life: adults and seedlings). The newly developed model was applied to estimate how the climate-vegetation system reaches equilibrium across different rocky planetary configurations, and to assess its impact on temperature and habitability. With respect to a world with bare granite continents, the effect of vegetation-albedo feedback is to increase the average surface temperature. Since grasses and trees exhibit different albedos, they affect temperature to different degrees. The ultimate impact on climate depends on the outcome of the competition between these vegetation types. The change in albedo due to vegetation extends the habitable zone and enhances the overall planetary habitability beyond its traditional outer edge. This effect is especially relevant for planets that have a larger extension of continents than Earth. For Earth, the semimajor axis d  = 1.04 au represents the turning point where vegetation enhances habitability from h  = 0.0 to 0.485 (in the grass-dominance case), to h  = 0.584 (in the case of coexistence between grasses and trees), and to h  = 0.612 (in the tree-dominance case). This illustrates the transition from a snowball state to a planet with intermediate habitability at the outer edge of the circumstellar habitability zone. [ABSTRACT FROM AUTHOR]

Surface albedo is an important parameter in radiative-transfer simulations of the Earth's system as it is fundamental for correctly calculating the energy budget of the planet. The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites continuously monitor daily and yearly changes in reflection at the planetary surface. The MODIS Surface Reflectance Black-Sky Albedo dataset (version 6.1 of MCD43D) provides detailed albedo maps for seven spectral bands in the visible and near-infrared range. These albedo maps allow us to classify different Lambertian surface types and their seasonal and yearly variability and change, albeit only into seven spectral bands. However, a complete set of albedo maps covering the entire wavelength range is required to simulate radiance spectra and correctly retrieve atmospheric and cloud properties from remote sensing observations of the Earth. We use a principal component analysis (PCA) regression algorithm to generate hyperspectral albedo maps of the Earth. By combining different datasets containing laboratory measurements of hyperspectral reflectance for various dry soils, vegetation surfaces, and mixtures of both, we reconstruct albedo maps across the entire wavelength range from 400 to 2500 nm. The PCA method is trained with a 10-year average of MODIS data for each day of the year. We obtain hyperspectral albedo maps with a spatial resolution of 0.05° in latitude and longitude, a spectral resolution of 10 nm, and a temporal resolution of 1 d (day). Using the hyperspectral albedo maps, we estimate the spectral profiles of different land surfaces, such as forests, deserts, cities, and icy surfaces, and study their seasonal variability. These albedo maps will enable us to refine calculations of the Earth's energy budget and its seasonal variability and improve climate simulations. [ABSTRACT FROM AUTHOR]

Oceanic stratocumulus decks of clouds are among the largest contributors to the Earth's radiation budget, covering around a fifth of the planet's surface and reflecting a large part of the incoming solar radiation. Unfortunately, these clouds are not well represented in modern climate models, resulting in one of the leading causes of uncertainty in climate change projections. This contribution analyses this issue from a novel perspective and sheds light on the mechanisms behind the misrepresentation and resolution dependence of these large clouds. The analysis is based on realistic week‐long simulations performed over a 563×563 km 2 oceanic domain. Four horizontal resolutions, between 4.4 and 0.55 km, are employed, resulting in a timely investigation, especially in light of the high resolutions employed by present and near‐future climate projections. Results show that the liquid cloud water, the main contributor to the simulated grid‐scale clouds, decreases with a power‐law decay as the resolution increases, whereas the water vapour, responsible for subgrid‐scale clouds, is much less affected by the grid spacing. The leading cause is identified as an imbalance between the rates of change of the advection and turbulence parametrisation terms. In order to verify this observation and provide a possible mitigation to the issue, a second set of simulations is performed where the turbulence parametrisation is tuned. The strategy proves to be successful, confirming the hypotheses and resulting not only in a resolution‐independent radiation budget but also cloud coverage. [ABSTRACT FROM AUTHOR]

Quaternary unconsolidated sediments are pronouncedly widespread features on the planetary surface, documenting significant geological signals of earth surface processes, climate change and biogeochemical cycles. The extensive unconsolidated deposits play a vital role in natural hazards and Anthropogenic activities, especially in alpine regions where massive unconsolidated materials are produced. However, the spatial distribution and total volume of unconsolidated sediments across the Yarlung Tsangpo River Basin (YTRB) remain largely unknown due to the limitation of traditional field surveys and on‐site measurements as well as the complex landscape in the remote area. This study presents the datasets for the systematic distribution and spatial accumulation of unconsolidated sediments across the Yarlung Tsangpo River Basin, southern Tibet. Combining remotely sensed data with numerous field investigations, an integrated method based on image processing and kriging interpolation‐pixel integration was performed to semi‐automatically classify and quantify the unconsolidated sediments. Eleven categories of sediments were mapped and their total accumulation is estimated at approximately 4.97 × 1011 t. Ultimately, 17 groups of classification and thickness maps were derived, revealing the distribution and volume of unconsolidated and Quaternary sediments. The datasets fill the gaps in comprehensive investigations of unconsolidated sediments for YTRB, and provide a fundamental database to support the scientific understanding of potential linkages between the distribution of unconsolidated sediments with environmental changes and human activities. [ABSTRACT FROM AUTHOR]

We explore the ability of an unmagnetized planet to retain an atmosphere as a function of its radius. We use a particle-in-cell hybrid code to simulate the global plasma interaction of unmagnetized terrestrial planets at 1 au under average solar wind conditions. We vary the radius of the planet |$(R_\mathrm{ p})$| from Mars-sized (⁠|$3390 \ \mathrm{km}$|⁠) to super-Earth-sized (⁠|$9390 \ \mathrm{km}$|⁠). We inject hydrogen and oxygen ion outflows from the ionosphere and quantify how the ion escape, recirculation, solar wind deposition, and net atmospheric mass flux vary as a function of planetary radius. We find that as the radius and the corresponding ionospheric outflow rate are varied, the fraction of outflowing |$\mathrm{ H^+}$| that escapes remains at |$15.5\pm 1.0{{\ \rm per\, cent}}$|⁠ , while the rest recirculates back towards the planet. The fraction of produced |$\mathrm{ O^+}$| that escapes from a Mars-sized planet is |$27\pm 1{{\ \rm per\, cent}}$|⁠ , and decreases to |$7\pm 1{{\ \rm per\, cent}}$| for super-Earth, suggesting that smaller planets are less able to retain heavy ions. We find, however, that larger planets have lower solar wind deposition fractions because their bow shocks are at greater distances from the surface of the planet. The ionospheric outflow rate at which mass deposition is equal to mass escape is found to be proportional to |$R_\mathrm{ p}^2$|⁠. Lastly, we propose that the bulk gyration of the solar wind at the induced magnetosphere can lead to differential escape trajectories of light and heavy ions. [ABSTRACT FROM AUTHOR]

The world's oceans cover more than 70 per cent of the planet's surface and contain 97 per cent of the water on planet Earth. Saltwater connects with freshwater with the outflow of every river and creek or from the drift of thunderstorms across islands to form new oceans. With a shared theme of water, recent projects are discussed as case studies for their focus on ecosystem awareness, cultural knowledge, arts and science and working collaboratively. Water is an essential element and connector of ecosystems, species and spirituality – of life. The ability of water to change forms from liquid to solid to gas offers insights into acknowledging that changeability and adaptability are core to species survival on the planet Earth. It is proposed that by respecting the knowledge that is embedded in the element of water that greater wisdom can be shared which can benefit all life on this planet. With this aspiration in mind, the term OneWater is used to explore the relational aspect of water to consider its connective quality, between watersheds and species. This concept is used to shift views of anthropogenic impacts and embrace a fuller recognition of Indigenous knowledge systems and the role they play in evolving our understanding of the OneWater. [ABSTRACT FROM AUTHOR]

Laboratory measurements of reflectance spectra of rocks and minerals at multiple viewing geometries are important for interpreting spacecraft data of planetary surfaces. However, efficiently acquiring such measurements is challenging, as it requires a custom goniometer that can accommodate multiple, bulky samples beneath a movable light source and detector. Most spectrogoniometric laboratory work to date has focused on mineral mixtures and particulates, yet it is also critical to characterize natural rock surfaces to understand the influence of texture and alteration. We designed the Three‐Axis N‐sample Automated Goniometer for Evaluating Reflectance (TANAGER) specifically to rapidly acquire spectra of natural rock surfaces across the full scattering hemisphere. TANAGER has its light source and the spectrometer's fiber optic mounted on rotating and tilting arcs, with a rotating azimuth stage and six‐position sample tray, all of which are fully motorized and integrated with a Malvern PanAnalytical ASD FieldSpec4 Hi‐Res reflectance spectrometer. Using well‐characterized color calibration targets, we have validated the accuracy and repeatability of TANAGER spectra. We also confirm that the system introduces no discernible noise or artifacts. All design schematics and control software for TANAGER are open‐source and available for use and modification by the larger scientific community. Plain Language Summary: To interpret spacecraft data sets of planetary surfaces, it is important to have similar data sets of rocks and minerals from Earth for comparison. Reflectance spectroscopy is a common technique in planetary science, and spacecraft make spectral reflectance measurements at multiple viewing geometries (with different positions of the sun relative to the planet's surface); therefore, it is important for laboratory spectral reflectance measurements to use multiple viewing geometries as well. However, such measurements are difficult, as they require custom instrumentation (a "goniometer") to control the angles of the light source and spectrometer detector. Most goniometers are designed for measuring small quantities of grains and particulates, but we have designed a new goniometer specifically for measuring the surfaces of bulky, natural rocks: the Three‐Axis N‐sample Automated Goniometer for Evaluating Reflectance (TANAGER). Using motorized, rotating and tilting arcs, TANAGER allows us to rapidly acquire reflectance spectra for multiple samples across a full range of viewing geometries. We have validated the accuracy and repeatability of TANAGER data, and we confirm that the system introduces no discernible noise or artifacts. All design schematics and control software for TANAGER are open‐source and available for use and modification by the larger scientific community. Key Points: Three‐Axis N‐sample Automated Goniometer for Evaluating Reflectance (TANAGER) is an automated goniometer designed to rapidly acquire reflectance spectra of rock surfaces across the full scattering hemisphereWe validated the accuracy and repeatability of TANAGER spectra and confirm that the system introduces no discernible noise or artifactsTANAGER's design schematics and control software are open‐source and available for use and modification by the scientific community [ABSTRACT FROM AUTHOR]

Mercury's exosphere is an important target for understanding the dynamics of coupled systems in space environments, tenuous planetary atmospheres, and planetary surfaces. Magnesium (Mg) is especially crucial for establishing methods for estimating the surface chemical composition distribution through observations of the exosphere because its distribution in the exosphere and on the surface is strongly correlated. However, owing to its low radiance, the Hermean Mg exosphere has only been detected by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft. Thus, we have few observation data for areas other than low latitude regions in addition to few detection cases of short‐term or sporadic fluctuations, resulting in a poor understanding of ejection and transportation mechanisms of the Mg exosphere. In this study, we analyzed the distribution of the Hermean Mg exosphere by the Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS) onboard the Mercury Planetary Orbiter of the BepiColombo mission during its second and third Mercury swing‐bys (MSBs). First, we constructed a calibration method including background subtraction and calibration using stellar observations. Mg light curves at two true anomaly angles were obtained, which were in agreement with the Chamberlain model and a three‐dimensional numerical calculation. Comparing the Mg and calcium (Ca) radiances obtained by PHEBUS during the MSBs, the exospheric Mg atoms have a lower energy than the exospheric Ca atoms. This is consistent with the lower energy necessary for producing the Mg atoms produced by molecular photodissociation than for Ca atoms. Plain Language Summary: The tenuous atmosphere of Mercury helps us to understand how space environments, thin planetary atmospheres, and planetary surfaces interact. Magnesium is particularly important because its presence in Mercury's atmosphere can tell us a lot about the planetary surface composition. However, studying the magnesium atmosphere in Mercury is challenging because of its poor visibility. In this study, we used a new ultraviolet spectrometer installed on the BepiColombo spacecraft. Analyzing solar light scattered by magnesium atoms when the spacecraft was close to Mercury, we derived distributions of Mercury's magnesium atmosphere, which are aligned well with theoretical models. Furthermore, we compared the energies of magnesium and calcium in the atmosphere, both of which were measured by the same instrument. We found that magnesium has a lower energy than calcium in Mercury's atmosphere, which is consistent with our understanding that less energy is necessary for magnesium than calcium to break apart their original molecules in photodissociation. This study also demonstrates how to improve the quality of data obtained from the BepiColombo spacecraft. Key Points: We established the calibration and background subtraction methods of the FUV channel of BepiColombo MPO/PHEBUSWe analyzed the swing‐by data and successfully obtained Mg exosphere distributions consistent with two theoretical modelsThe lower energy of the Mg exosphere than that of Ca reflects the lower energy required for photodissociation from their parent molecules [ABSTRACT FROM AUTHOR]

The lunar surface contains a wide variety of topographic shapes and features, each with different distributions and scales, and any analysis technique to objectively measure roughness must respect these qualities. Coarse‐graining is a naturally scale‐dependent filtering technique that preserves scale‐dependent symmetries and produces coarse elevation maps that gradually erase the smaller features from the original topography. In this study of the lunar surface, we present two surface variability metrics obtained from coarse‐graining lunar topography: fine elevation and coarse curvature. Both metrics are isotropic, deterministic, slope‐independent, and coordinate‐agnostic. Fine (detrended) elevation is acquired by subtracting the coarse elevation from the original topography and contains features that are smaller than the coarse‐graining length‐scale. Coarse curvature is the Laplacian of coarsened topography, and naturally quantifies the curvature at any scale and indicates whether a location is elevated or depressed relative to its neighborhood at that scale. We find that highlands and maria have distinct roughness characteristics at all length‐scales. Our topographic spectra reveal four scale‐breaks that mark characteristic shifts in surface roughness: 100, 300, 1,000, and 4,000 km. Comparing fine elevation distributions between maria and highlands, we show that maria fine elevation is biased toward smaller‐magnitude elevations and that the maria–highland discrepancies are more pronounced at larger length‐scales. We also provide local examples of selected regions to demonstrate that these metrics can successfully distinguish geological features of different length‐scales. Plain Language Summary: Planetary surface roughness is inherently scale‐dependent: a seemingly smooth surface can look rough if you zoom in enough. The converse can also hold: small‐scale rough features can look smooth if you zoom out enough. Therefore, it is important to have a way to measure surface roughness that accounts for variations in how "zoomed in" we are looking. In this work we use coarse‐graining, an approach that effectively blurs the lunar surface, allowing us to vary the "zoom" level as we are measuring surface variability. We present two ways of measuring the scale‐dependent variability of the lunar surface: coarse curvature (measures how curved the blurred surface is) and fine elevation (looks at everything that was removed by the blurring, and measures how much those smaller features contributed to the topography). Using our approach, we are able to incrementally change what is considered "small" and measure how the perception of the lunar surface changes as we are gradually zooming out of it. Our results highlight the dichotomy in roughness between the lunar maria and highlands. We also identify four key length‐scales where the roughness changes qualitatively, suggesting a change in the underlying physical processes that contribute to different kinds of roughness. Key Points: Two novel metrics for surface variability display distinct characteristics for highlands, maria, and various geological featuresTopographic spectra spanning 1–5,000 km identify four roughness characteristic changes that correlate with known crater distributionsFrequencies of fine elevation highlight and contrast scale‐ and terrain‐dependent behaviors between mare and highlands regions [ABSTRACT FROM AUTHOR]

Context. Space weathering alters the surfaces of airless celestial bodies, thereby modifying their spectra significantly. Olivine plays a crucial role in responding to space weathering on silicate planets. However, the spectral variations that occur in olivine with varying iron content as a result of space weathering conditions remain unclear. Aims. We aim to systematically characterize the spectral variability of surface iron-rich olivine in the space weathering environments of Phobos and the Moon. Methods. We conducted nanosecond pulsed laser irradiation experiments on a set of synthetic Fe-rich olivine (Fa29, Fa50, Fa71, and Fa100). The energy levels were simulated for Phobos and the Moon. We analyzed the available near-infrared (NIR) spectroscopy. Results. We find that olivine with higher Fe content undergoes stronger weathering under the same irradiation energy, shifting absorption centers around 1.08 µm and 1.35 µm to longer wavelengths. When comparing the high energy and low frequency, spectral changes are more pronounced at low energy and high frequency. The olivine with the same iron content exhibits a more noticeable shift around 1.08 µm under various irradiation levels, while the band center around 1.35 µm remains stable. Conclusions. When the same amount of radiation energy is received, changes in the spectrum are more noticeable at low energy and high impact frequency than at high energy and low impact frequency. The absorption position at ~1.35 µm is a good indicator of the Mg# value of space-weathered olivine. [ABSTRACT FROM AUTHOR]

The diversity of underground fauna is often associated with the presence of karst areas, which have extensive underground cavities and connecting channels. Non-karst areas, however, make up a larger portion of the planet' surface, and our understanding of the distribution and dispersal abilities of underground fauna in these areas currently remains limited. During a recent study of the diversity of stygobiotic crustaceans in the mountain streams of the Kurai Mountain Range (Altai, Russia), a small-sized species of crangonyctid amphipod, Palearcticarellus pusillus (Crustacea, Amphipoda, Crangonyctidae) was found in high-altitude springs. This species has been previously known only from deep-water habitats in Lake Teletskoye, and molecular genetic analysis revealed that these amphipods maintain genetic connections between the springs and bottom lake habitats. We assume that individuals of this certainly stygobiotic species fall to the bottom of the lake as a result of leaching from tectonic faults connecting these habitats and are not permanent inhabitants of the lake bottom. This hypothesis also suggests that the very small body size of these animals may be related to the narrow crevices and pores of the tectonic faults, rather than neoteny, as it has been previously suggested. The estimated divergence time calculation has also revealed that P. pusillus obviously diverged from its sister species, Palearcticarellus mikhaili from valley springs in Kurai Steppe, ~5 Ma, at the beginning of the Pliocene, possibly due to the uplifting of the Kurai Mountain Range. Subsequent speciation occurred as a result of secondary tectonic activity and changes in groundwater flow, likely during the Pleistocene, approximately 2.7-0.7 Ma. Populations that were isolated for a long time continue to live near mountain springs in the study area. [ABSTRACT FROM AUTHOR]

Impact craters are a unique tool not only for inferring ages of planetary surfaces and examining geological processes, but also for exploring subsurface properties. We use ejecta blankets as proxies to obtain insights into the subsurface characteristics and the vertical stratification of Ganymede's icy crust. We investigated 36 prominent ray and halo craters using images acquired during the Voyager, Galileo, and Juno spacecraft missions. These craters exhibit diverse characteristics, including dark rays, bright rays, or their combination, in both continuous and discontinuous patterns as well as dark and bright halos. Dark halo craters (DHCs) have the smallest radial extents of their dark ejecta deposits, while dark ray craters (DRCs) have the largest. DRCs in dark terrain suggest a thickness of less than ∼2 km based on their excavation depths. DRCs and DHCs craters located in light terrain (LT) reveal significant heterogeneity in the uppermost portions of icy crust at various locations. DRCs and DHCs in the LT require the presence of at least one layer of dark material. This is the case if the LT is formed by tectonic rifting and graben formation. In contrast, if the LT is formed by tectonic spreading, bright halo and ray craters are expected to form. Key Points: We utilized ray and halo craters on Ganymede to determine the vertical stratigraphy of its icy crustThe excavation depths of dark ray craters in Ganymede's dark terrain suggest kilometer thick dark terrain layersThe ejecta facies of impact craters allow to narrow down the tectonic regime of crustal extension (rifting or spreading) [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]

Impact craters are crucial for our understanding of planetary resources, geological ages, and the history of evolution. We designed a novel pseudo-spectral spatial feature extraction and enhanced fusion (PSEF) method with the YOLO network to address the problems encountered during the detection of the numerous and densely distributed meter-sized impact craters on the lunar surface. The illumination incidence edge features, isotropic edge features, and eigen frequency features are extracted by Sobel filtering, LoG filtering, and frequency domain bandpass filtering, respectively. Then, the PSEF images are created by pseudo-spectral spatial techniques to preserve additional details from the original DOM data. Moreover, we conducted experiments using the DES method to optimize the post-processing parameters of the models, thereby determining the parameter ranges for practical deployment. Compared with the Basal model, the PSEF model exhibited superior performance, as indicated by multiple measurement metrics, including the precision, recall, F1-score, mAP, and robustness, etc. Additionally, a statistical analysis of the error metrics of the predicted bounding boxes shows that the PSEF model performance is excellent in predicting the size, shape, and location of impact craters. These advancements offer a more accurate and consistent method to detect the meter-sized craters on planetary surfaces, providing crucial support for the exploration and study of celestial bodies in our solar system. [ABSTRACT FROM AUTHOR]

Innovative techniques are required for the in situ investigation of the surfaces of planetary bodies when landings are planned. Raman spectroscopy turned out as an excellent tool for fast mineralogical analyses on space missions. Contribution from a photoluminescence signal is not unexpected and is likely to be even more pronounced on celestial surfaces with a dilute or absent atmosphere exposed to strong space weathering, for example, micrometeorite bombardment. Such signals were found, for example, in Raman analysis of the probes from sample‐return missions. While photoluminescence is generally considered as an accompanying undesired product in the Raman spectral measurement, our studies show that some analytical information can be derived from this signal, and even more, due to the specific correlation of luminescence intensity with space weathering products. Therefore, we investigate the Raman spectra alteration of characteristic rock‐forming mineral mixtures (olivine, pyroxene and plagioclase) by micrometeorite bombardment, which is simulated by nanosecond‐pulse laser irradiation. The changes in the minerals are strongly dependent on the composition and structure. They range from disappearing changes in the minerals with simple chemistry and structure to complete amorphization of minerals with relatively low melting enthalpy. With Raman spectroscopy, we found out that the photoluminescence signals show resonant or anti‐resonant changes to specific mineral phases and amorphization. Furthermore, ablation‐induced iron nanoparticles of minerals containing Fe are detectable by Raman spectroscopy due to their alteration into iron oxides. Trapped volatiles in the matrices are analysed due to the formation of the compounds containing them. This broad spectrum of results indicating specific change phenomena due to space weathering can be effectively used for in situ Raman analysis in planetary missions. [ABSTRACT FROM AUTHOR]

It has been found that the intraday dynamics of body temperature in small mammal and bird species on the adjacent day are similar. Therefore, by focusing on the body temperature dynamics of the previous day, it is possible to predict with a high degree of accuracy the periods of increase and decrease in body temperature for the current day. This phenomenon was observed when animals were kept under natural illumination and under artificial illumination when the phase of the intrinsic circadian rhythm shifted by 1-2 h every day. When analyzing this phenomenon in birds, it has been shown that the best match for body temperature dynamics occurs when comparing adjacent days based on sidereal days (a period of 23 h and 56 min). Over time, after several days, the daily patterns of body temperature fluctuation take on a completely different form and frequency. These facts suggest a connection between ultradian rhythms and the rotation of the Earth around its axis, and consequently, the position of animals on the surface of the planet relative to space objects. [ABSTRACT FROM AUTHOR]

This review examines complexity science in the context of Heliophysics, describing it not as a discipline, but as a paradigm. In the context of Heliophysics, complexity science is the study of a star, interplanetary environment, magnetosphere, upper and terrestrial atmospheres, and planetary surface as interacting subsystems. Complexity science studies entities in a system (e.g., electrons in an atom, planets in a solar system, individuals in a society) and their interactions, and is the nature of what emerges from these interactions. It is a paradigm that employs systems approaches and is inherently multi- and cross-scale. Heliophysics processes span at least 15 orders of magnitude in space and another 15 in time, and its reaches go well beyond our own solar system and Earth's space environment to touch planetary, exoplanetary, and astrophysical domains. It is an uncommon domain within which to explore complexity science. After first outlining the dimensions of complexity science, the review proceeds in three epochal parts: 1) A pivotal year in the Complexity Heliophysics paradigm: 1996; 2) The transitional years that established foundations of the paradigm (1996-2010); and 3) The emergent literature largely beyond 2010. This review article excavates the lived and living history of complexity science in Heliophysics. It identifies five dimensions of complexity science, some enjoying much scholarship in Heliophysics, others that represent relative gaps in the existing research. The history reveals a grand challenge that confronts Heliophysics, as with most physical sciences, to understand the research intersection between fundamental science (e.g., complexity science) and applied science (e.g., artificial intelligence and machine learning (AI/ML)). A risk science framework is suggested as a way of formulating the grand scientific and societal challenges in a way that AI/ML and complexity science converge. The intention is to provide inspiration, help researchers think more coherently about ideas of complexity science in Heliophysics, and guide future research. It will be instructive to Heliophysics researchers, but also to any reader interested in or hoping to advance the frontier of systems and complexity science. [ABSTRACT FROM AUTHOR]

Bistatic radar experiments have been used to study surface characteristics of extra-terrestrial bodies in the Solar System, including the Moon, Venus, Mars, and Titan. This paper proposes a 3D model to characterize the scattered field of a gaussian rough surface on an extra-terrestrial body for an orbital bistatic radar configuration. Specifically, this model will investigate how the variability of surface roughness impacts the spectral broadening of the received signal using physical optics approximations and ray tracing on a surface model using a facet approach with Gaussian properties. A linear relationship between spectral broadening of the signal and surface roughness was found. This relationship is in line with results obtained by commonly used analytical models for bistatic radar on planetary surfaces. [ABSTRACT FROM AUTHOR]

The process of casing the wellbore in oil and gas drilling consumes a significant amount of time and economic resources. High-energy laser rock fracturing, as an efficient and cost-effective new approach, holds the potential to create a glass-like casing by irradiating the rocks as an alternative to traditional casing. The mechanism behind the vitrification of rocks using laser irradiation, a key factor in achieving glassified casings, remains to be studied. This paper, based on experiments involving scanning sandstone with a line laser, investigates the mechanism of rock vitrification using numerical simulations and X-ray diffractometers. The results demonstrate that the sandstone surface is transformed into glass after laser scanning, with multiple scans and the application of high-speed airflow helping to reduce the formation of bubbles and other phenomena. Furthermore, the speed of laser scanning showed a negative correlation with the laser ablation depth, glass thickness, temperature diffusion rate, and temperature gradient. Based on these findings, a groundbreaking method is proposed for creating high-quality glass by moving the laser to scan the rocks multiple times, offering insights for research into laser-manufactured wellbore casings. Furthermore, this approach holds promising prospects for enhancing and embellishing the exterior of structures and for in situ environmental modifications on planetary surfaces and beyond. [ABSTRACT FROM AUTHOR]

Remote sensing observations represent the primary means in the production of geologic maps of planetary surfaces. However, they do not provide the same level of detail as Earth's geologic maps, which rely also on field observations and laboratory analyses. Color‐derived basemaps can help to bridge this gap by highlighting peculiar surface and compositional properties. Here, we analyzed the spectral properties of the lunar Tsiolkovskiy crater through the definition of spectral units summarizing the information enclosed by a set of selected spectral parameters. We then performed a compositional analysis of the newly derived spectral units that helped us in discriminating the presence and relative abundance of the main mineralogical phases on the Moon. As a final step, we produced a geo‐stratigraphic map of the Tsiolkovskiy crater integrating in a single mapping product both morphologic, stratigraphic and compositional information. The basaltic infilling of the crater is distinguished by three spectral units associated with distinct effusive events presenting a different composition. On the central peak, plagioclase and olivine suggest the presence of Mg‐suite rocks from the lower crust. The continuous ejecta deposits are mostly characterized by impact melts and shocked materials rich in glass or agglutinates related to more mature terrains from which occasionally appear fresher anorthositic and gabbroic outcrops exposed by the inward sliding of the crater walls. Overall, the geo‐stratigraphic map allows inferring compositional variations associated with the different morpho‐stratigraphic units, which clarify and elaborate on the compositional heterogeneities within the lunar crust and the Tsiolkovskiy crater, and its geologic evolutionary history. Plain Language Summary: The main data used to produce geologic maps of planetary surfaces come from orbiting missions. However, geologic maps of Earth provide much more information, relying also on observations made on the field and analyses made in the laboratory. Color images derived from the combination and processing of spectral information can help to make planetary maps more comprehensive, similarly to the Earth's ones, by drawing attention to surface and compositional aspects. In this work, we performed a spectral and compositional study of the Tsiolkovskiy crater on the Moon which enabled us to distinguish the presence and relative quantity of the most common minerals constituting the lunar rocks. We also produced a geo‐stratigraphic map coupling the information about the surface textures and shapes, relative time of deposition, and composition. On the basaltic floor, we discriminated the presence of three different spectral characteristics correlated with a sequence of flooding events showing distinct properties and a central peak exhibiting rocks emerged from the lowest strata of the lunar crust. The continuous ejecta blanket, instead, is characterized by mature materials interspersed by fresher exposures of subsurface materials. To conclude, the new mapping product allows an in‐depth interpretation of the geologic evolution of the Tsiolkovskiy crater. Key Points: Production of a 10‐unit Spectral Units map conveying the spectral and compositional properties within the Tsiolkovskiy craterIntegration of geologic and spectral units to produce a more comprehensive mapping product, namely a geo‐stratigraphic mapElaboration on the geological and compositional evolution of our study area [ABSTRACT FROM AUTHOR]