The Comet Interceptor mission, a joint program between ESA and JAXA, aims to perform in-situ plasma measurements during a high-speed cometary flyby. This study is based on the Time-of-Flight (TOF) ion analyzer onboard the mission's spacecraft, designed to characterize cometary plasma environments. In such environments, a major challenge for plasma composition analysis is the rich abundance of diverse molecular ion species that share nearly identical or very close mass-to-charge ratios (). Conventional frameworks fail to uniquely determine individual ion abundances because a single detection pathway provides incomplete information: utilizing only the Linear Electric Field (LEF) pathway yields only elemental trends, while the Straight-Through (ST) pathway fails to distinguish different species at the same nominal mass. To overcome this limitation, we develop a novel inversion framework that integrates both LEF and ST detection pathways to retrieve individual cometary ion number densities via a weighted non-negative least-squares optimization. To resolve severe degeneracies where different ion compositions produce nearly identical spectral profiles, the framework incorporates two key physical constraints: energy-dependent mass separation arising from the nearly uniform velocities of low-energy cometary ions entering the instrument under high-speed flyby conditions, and species-dependent charge-exchange probabilities during carbon-foil transmission in the ST pathway. Validation using simulated environments based on comet 67P/Churyumov–Gerasimenko demonstrates that the proposed method achieves stable, reproducible estimation of all 17 considered ion species. Furthermore, additional test cases under alternative conditions confirm the framework’s high flexibility and resilience against unpredictable target characteristics, providing a robust methodology for future multi-pathway TOF mass spectrometers.
Martian gullies are geologically recent landforms that may form either through liquid-water activity and/or through processes involving CO2 ice. We investigated the mechanisms responsible for the formation or modification of these features by focusing on the active site of Sisyphi Cavi (68°S, 1°E), located outside the typical latitude range of gully presence. Using CRISM and OMEGA infrared data, we characterized the composition and physical state of seasonal surface ices to test the relevance of H2O and CO2 ice driven mechanisms. Our analysis shows that H2O ice is not detected as an independent surface deposit, although it may be present as minor inclusions within the CO2 ice layer. In particular, during the final phase of CO2 ice sublimation in late spring, no H2O ice signature is observed. In the area, faint spectral signatures of sulfate salts are observed, but their distribution and amount do not suggest any direct link with gully activity. Available observations during early and mid-spring reveal that CO2 ice is translucent during these times, suggesting that it likely remains in this state through most of the ice season. However, a temporal mismatch between dark spot formation - indicative of CO2 geysers through translucent ice - and gully modification (respectively occurring late winter to early spring, and mid to late spring) exists. This does not suggest a systematic link between both processes. Overall, the available observations provide no evidence that liquid water contributes to present-day gully activity at Sisyphi Cavi, while offering no support either for the hypothesis that gully modifications are mainly driven by the formation of CO2 geysers. Gully modifications at Sisyphi Cavi, observed during the late sublimation stages of CO2 ice, may be rather more appropriately explained by CO2-ice-based fluidization or avalanche processes.
Laser-induced breakdown spectroscopy (LIBS) is increasingly paired with Raman spectroscopy in planetary exploration to provide complementary elemental and mineralogical constraints. LIBS, however, can modify the target via shock and thermal effects, potentially biasing subsequent Raman identifications. We quantify LIBS-induced alteration halos in two terrestrial planetary analogs: (i) an ophiolite-derived ijolite–peridotite containing silicates, oxides, sulfides, and carbon-bearing microdomains; and (ii) a plagioclase-rich basaltic lava with carbonate-bearing domains. Using a 1064 nm Nd:YAG LIBS system operated at three pulse-energy settings (5%, 10%, 20%; energies at target reported in Methods), we map crater morphology and halo extent by optical microscopy and SEM-EDS, and characterize phase/texture changes by micro-Raman spectroscopy and AFM topography. Increasing pulse energy enlarges the optically visible disturbed zone (hundreds of micrometers to >1 mm in carbonate-rich heterogeneities) and produces nanoscale redeposition (up to ∼2 μm relief) consistent with melt ejection and condensation near crater rims. Raman spectra within halos show strengthened hematite signatures relative to outside-halo controls and increased carbon structural disorder in carbon-bearing microdomains. In localized high-energy shots, Raman bands consistent with high-pressure garnet components are observed in restricted micro-areas and are reported as majorite-like signatures pending independent structural confirmation. These results demonstrate that LIBS can generate modified zones at scales relevant to rover operations, motivating conservative sequencing and spatial offsets in sequential LIBS–Raman workflows and supporting mission calibration strategies that explicitly account for LIBS-induced alteration when interpreting mineralogy in situ.
Tesserae on Venus, the planet's oldest geological units, record complex tectonic and magmatic histories. This study focuses on the tessera terrain of the northeastern central region of Ovda Regio (∼800,000 km2), where we mapped lineaments (interpreted mainly as grabens, fissures and fractures) using full-resolution Magellan SAR imagery at a 1:500,000 scale. We identify 26 distinct lineaments systems — 10 radiating, 12 circumferential, and 4 linear — that are interpreted as the surface expression of underlying mafic dyke swarms linked to mantle plume activity. We interpret the cross-cutting relationships to reveal the following sequence of events: (1) arrival of a mantle plume (∼250 km radius); (2) emplacement of a radiating dyke swarm and triple junction rifting; (3) volcanic flooding of central and rifted regions; (4) a ∼300 km shift to the south of the centre of magmatic activity, marked by a second radiating swarm and second centre of triple junction rifting; and (5) emplacement of coronae and radiating swarms localized along thinned crust in the rifts. Our analysis supports the interpretation that tesserae record two major geological phases. The first “Tessera Formation” phase, possibly extending back to ∼4 Ga, involved tectonic deformation and lateral accretion of crustal blocks. The second “Post-Tessera Formation” phase is characterized by magmatic and tectonic activity in the absence of significant erosion, including dyke swarm emplacement and rifting associated with mantle plumes.
Planetary radar sounding data includes echoes from surfaces that can produce both coherent and incoherent energy. Approaches to analyzing or modeling these echoes can differ based on the balance of coherent and incoherent energy assumed in the analysis or model. Recent developments in sounder simulators have provided planetary radar scientists with the ability to model returns from simulator facets that are coherent, incoherent, or a combination of the two. There has, however, been little assessment of the relative importance of incoherent energy in the subset of echoes that are strong enough to be detected. The key question is not simply whether incoherent energy exists in the radar return, but whether the incoherent component is strong enough to rise above the noise floor in realistic mission scenarios. To address that question, we perform link-budget calculations that capture the differential geometric spreading losses experienced by the coherent and incoherent energy components and find that, for nearly all planetary radar sounding scenarios, the incoherent portion of echoes contributes little or no detectable energy. By contrast, we find that echoes from very small coherent local surface facets are often robustly detectable. This raises the possibility that analysis and simulation approaches focused on the coherent portion of echoes may be the most appropriate for simulation or analysis of planetary sounding data. It also highlights the opportunity for statistical approaches built on assumptions about detectable incoherent energy to be reformulated around the contributions of coherent facets alone.
Mercury’s surface is covered by regolith produced by meteoritic bombardment, recording the planet’s impact and geological history. In this study, we assess the regolith thickness of the Borealis Planitia region (-72°E, 66°N), within two hermean terrain types: the smooth plains and the older intercrater plains. The regolith thickness is estimated using the highest resolution imagery available from MESSENGER’s Mercury Dual Imaging System Narrow Angle Camera (MDIS NAC) and the small crater morphology method. A total of 3,546 craters (< 400 m in diameter) presenting a specific morphology (i.e., central mound, flat-bottomed or concentric) were identified and characterized. In addition, 855 bowl-shaped craters (BSC) are mapped and their depth, derived from a depth-to-diameter law, is used to estimate a lower boundary of the regolith thickness, as BSC form solely in regolith. The estimated regolith thickness is highly variable laterally within the two units, with, on average, thicker regolith in the smooth plains (median: 4.6 m) and a thinner regolith in the intercrater plains (3.7 m). No correlation between regolith thickness and surface age can be established, highlighting a possible difference in the bedrock properties of the two units. The hermean regolith is generally thicker than on the Moon, as expected, because the higher impact energy due to the Sun’s proximity leads to more regolith production. While our study provides one of the first estimates of regolith thickness in Mercury’s volcanic units, further quantitative analyses of the hermean regolith thickness at a global scale are needed for comparison and assessment of the physical structure of Mercury’s surface, especially in the absence of in situ data.
In this paper, characteristic ultraviolet absorption spectra are presented for benzoic acid, phthalic acid, and mellitic acid in transparent hexagonal water ice solutions at temperatures between 273 K and 78 K. In addition, the liquid solution spectra at 292 K have also been included. The temperature range of our study covers some of the average temperatures that have been found in the polar regions of Mars, the icy moons of Jupiter (Europa, Ganymede, and Callisto), and Saturn (Enceladus). Average Surface temperatures for Enceladus are from 85 K at the equator and south pole to as low as 65 K in the north pole and other areas, for Europa temperatures range from as high as approximately 140 K at the equator to as low as approximately 50 K at the poles, and for Mars from 293 K at noon at the equator, and as low of about 120 K at the poles. The experimental results presented in this paper could serve as a UV absorption database for comparison and identification of organic molecules for future space missions where water ice is expected to be found.
This study presents a strategy to produce artificial rocks, or simulants, designed to replicate boulders observed on the surface of asteroid Ryugu. The simulants are composed of a dust mixture with bulk composition and grain size distribution based on the analysis of particles returned from Ryugu by the Hayabusa2 mission. Two production methods, freeze-drying and dry-compression, were established to generate simulants with porosities between 45% and 80%. Five key parameters were used to characterise the simulants and to compare them with Ryugu particles: the bulk composition of the dust mixture, the size and shape distribution of the individual components, the simulant microstructure, i.e. the internal distribution of material and void spaces, and the interaction between the grains within the simulant. These parameters were assessed using scanning electron microscopy, laser diffraction, helium gas pycnometry, and micro-tomographic analysis. Even though some discrepancies in composition and grain size distribution remain, these can be addressed in future updates of the simulant dust mixture. It was generally found that freeze-dried simulants capture the microstructure and grain interactions of Ryugu particles better than the dry-compressed simulants. In a next step, thermal and mechanical properties of the simulants will be measured to support the interpretation of remote sensing observations of Ryugu’s surface.
Venusian lava flows display morphological and geochemical characteristics distinct from terrestrial basalts, yet their mineralogical composition remains poorly constrained. A key unresolved factor is the role of oxygen fugacity (fO2) in controlling mineral assemblages and residual melt evolution under Venus surface conditions. Here, we integrate high-temperature petrological experiments with thermodynamic modeling to quantify the effect of fO2 on the crystallization of Venus-like basalts. Experiments performed on a Krafla basalt analog under a CO2-rich, Venus-like atmosphere define a liquidus temperature below 1214 °C, used as the starting point for anhydrous crystallization modeling from 200 MPa down to 1024 °C across a redox range of QFM −3 to QFM +3. Results show that oxygen fugacity exerts a primary control on both melt composition and mineralogy. Increasing fO2 produces residual melts enriched in SiO2 and Fe2O3 and depleted in FeO, accompanied by systematic changes in phase stability. Pyroxene remains the dominant phase but decreases in mode with increasing fO2, whereas plagioclase is relatively insensitive to fO2. Ilmenite and apatite are stabilized under more oxidizing conditions, while magnetite is absent across the modeled ranges in temperatures and fO2. Comparison with normative mineralogy from Soviet Venus missions shows broad agreement for major phases, supporting the robustness of the models. These results provide quantitative constraints on how redox conditions influence surface mineralogy, improving the interpretation of orbital spectral and radar observations of Venus.
The emerging field of astrometallurgy is set to play a crucial role in enabling metal production on the Moon. This paper focuses on Fe-Si alloy production from the lunar regolith using carbothermal reduction. Thermodynamic modelling was conducted to understand the effects of varying carbon, temperature, and pressure on the regolith reduction. Modelling results predict that ideal parameters for the extraction of liquid Fe-Si alloys from lunar regolith under terrestrial conditions are 2 wt% carbon at 1600°C. Modelling results also predict that higher reduction temperature leads to increased impurities such as Ti, P and Mn in the Fe-Si alloy. Effects of varying carbon content on the composition and viscosity of the slag are also discussed. Thermodynamic modelling under lunar vacuum conditions (3 × 10−15 bar) predicted that Fe-Si alloy forms as solid phases below 650°C, while Fe and Si transition to the gas phase at higher temperatures. The thermodynamic prediction results under terrestrial conditions were verified through experiments. The Fe-Si alloy produced from regolith reduction with 2 wt% carbon resulted in easy slag-metal separation, and the Fe-Si alloy contained about 7 to 8 wt% Si with about 1 wt% P. At 4 wt% carbon, Si content in the Fe-Si increased to 15 wt% and the alloy contained about 1 to 2 wt% P. With the further rise in carbon to 6 and 8 wt%, Ti formed an intermetallic Ti-rich phase with Si and Fe. These findings support the viability of extracting Fe-Si alloy from lunar regolith through carbothermal reduction.
Impact melts are created when an impactor strikes the surface of a rocky body with sufficient velocity to melt target material. Radiogenic isotope studies can be conducted on impact melts to determine the timing of impact melting events, which can in turn be used to calibrate the lunar geochronology. The latter is currently calibrated with Apollo samples ranging between 3.92 and 3.15 Ga (Nectarian and Imbrian), and 0.80-0.002 Ga (Copernican), with Chang’E−5 samples of intermediate age (Eratosthenian, 2.03 ± 0.004 Ga). Acquiring additional impact melt samples of known provenance would allow to better calibrate the lunar geochronology and is of high scientific interest for future robotic and human missions. We conducted a survey of 655 fresh impact craters located between 70° and 90°S in the search for impact melt deposits using Mini-RF data and Lunar Reconnaissance Orbiter Camera images. We identified impact melt deposits associated with 9 fresh craters between ∼70°S and 83°S, including De Forest and Zeeman Y (Upper Imbrian) and others likely Eratosthenian or Copernican. Four impact melt deposits have the highest scientific value and somewhat favorable accessibility, making them potential candidates for sampling. The flow around 10-1-035462 offers an opportunity to sample young material and Orientale basin deposits. The flow around Schomberger A offers an opportunity to sample Copernican material. Impact melt ponds around Zeeman Y and within De Forest have the highest iron abundance values. They could potentially allow to sample lower crustal or mantle material and date SPA.
A significant number of the major celestial bodies in the Solar System are characterized by high percentages of ice in their surface composition. Previous works have shown how the rheological behavior of ice-rock mixtures under different pressure, gravity and temperature conditions can be studied based on the morphologies of landslides. It has long been known that terrestrial landslides that occur on frozen surfaces show very low apparent friction, calculated as the aspect ratio between the fall height of the landslide and its horizontal movement. A possible mechanism to explain this low friction and consequently high mobility is the presence of a temporary meltwater layer at the interface between the debris and the impacted ground. This paper examines landslides on different planetary bodies of the Solar System composed of ice in varying amounts, from the ones containing ice only in the rock pores, to nearly completely icy mass flows. A mechanical-thermodynamic model of ice melting at the base of these landslides is investigated. Lubrication is explicitly introduced as a consequence of frictional melting of ice, which is found to be very sensitive to the gravity field, the topographic profile, and the temperature of the bodies. Results explain the decrease in friction coefficient, while the volume effect is seen to occur with more efficacy for bodies with high gravity and is absent for the very low-gravity comet 67/P. The results indicate the importance of initial temperature, ice content and especially gravity in ice lubrication dynamics of icy landslides in the different planetary bodies.
Magnetic field fluctuations in the Jupiter dusk magnetosheath during the Cassini crossing in 2000-2001 are studied in this work. The properties of the turbulence in this magnetosheath interval are compared with those observed during a background solar wind interval using wavelet, Fourier, kurtosis and multifractal techniques. It was found that the variance of the magnetic field is much higher in the magnetosheath than in the solar wind by factors of 6 to 36 times. The kurtosis parameter was enhanced and larger than 3.0 for the BT and BN components in the magnetosheath, contrasted to the solar wind, which showed a sub-Gaussian behaviour. The multifractal spectrum showed a quasi Gaussian behaviour for the solar wind magnetic field and the occurrence of tails in the magnetic field distributions for the magnetosheath interval. The wavelet analysis showed that there are comparable periods of about 5 to 15 h in the magnetosheath and in the solar wind but these periods are intermittent or present local occurrences in the magnetosheath while they are more continuously observed in the solar wind. Finally, the Fourier power spectrum results showed higher spectral power for the magnetosheath magnetic field components, a power break at 3 mHz for the magnetosheath and solar wind data, with higher power indices in the high frequency portion of the spectra for the magnetosheath (absolute spectral indices varying from 2.3 to 2.7 at high frequencies) than for the solar wind (power index about 2.1). These results show quantitatively that the plasma turbulence is higher in the jovian magnetosheath than in the background upstream solar wind, due to the fact that as the continuous solar wind is compressed and heated at the bow shock, it becomes disrupted and turbulent.
We present simulations of lunar exospheric neon (20Ne) that include diurnal variations of the surface temperature measured by the Diviner radiometer onboard the Lunar Reconnaissance Orbiter (LRO). The Diviner-based model predicts a different exospheric density than the models based on analytical and empirical expressions of the surface temperature. The discrepancy is most evident in craters with a high abundance of rocks, which at night radiate more heat compared to the surrounding areas. We focus on Tycho, Tsiolkovskiy, and Giordano Bruno. For Tycho, the most prominent of these, the expected local depletion in exospheric density can be as great as similar to 18%, up to an altitude of similar to 20 km. This deviation could be detectable by a mass spectrometer orbiting the Moon at a few tens of kilometers of altitude. We compare the modeled exospheric densities with data from the Neutral Mass Spectrometer (NMS) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE). The Diviner-based model and the model based on the empirical formula of the surface temperature demonstrate superior agreement with the data, compared to the model based on analytical expression of the surface temperature. The radial profiles of exospheric 20Ne density at several lunar phases, latitudes, and local time show a common altitude (90-100 km) above which the exospheric density is greater on the dayside compared to the nightside, opposite to what is observed at lower altitudes. We find that charge exchange with solar wind protons is a negligible loss process for lunar exospheric 20Ne.
Because of significant challenges posed by space exploration missions, experiments in simulation chambers could shed light on certain planetary processes of interest to support mission design and mission data interpretation, as well as for testing science payloads for missions. Here we present our planetary environment simulation system built at Washington University in St. Louis. The system includes a two-layer vacuum baking chamber for sample preparation and a vacuum reaction chamber (upgraded planetary environment and analysis chamber, PEACh) featuring controllable temperature, pressure, and gas composition. The upgraded PEACh can simulate water-rock interaction via a water injection port, and it can simulate space weathering by using an energetic electron impact (EEI) accessory. In addition, this vacuum reaction chamber is equipped with in-situ monitoring probes, including Raman spectroscopy and plasma spectroscopy, as well as a video camera. The whole system is mainly designed for simulating water-regolith interactions in the lunar polar regions, but it can also simulate other planetary environments, such as conditions at the martian surface.
The Perseverance rover explored a boulder field on Jezero western fan, where meter-scale boulders are enriched in either olivine or pyroxene, recording high-energy, episodic, and late-stage flood emplacement events from Jezero watershed. However, their composition diversity and alteration histories have remained poorly constrained. In this work, we integrate Mastcam-Z, SuperCam, SHERLOC, and PIXL data to further characterize their mineralogy and geochemistry from multiple perspectives, revealing two distinct assemblages and evolution pathways. Olivine-bearing boulders exhibit evidence of serpentinization, carbonation, and sulfation, indicative of deriving from olivine-carbonate units within or outside Jezero crater. In comparison, pyroxene-bearing boulders record hydration to smectite, phosphate transformations, sulfation, and subsequent surface weathering, suggesting that they could be derived from the Noachian basement of Jezero watershed. Two types of boulders underwent different lithification and limited alteration before being emplaced by late-stage floods to the western fan. These results reveal new constraints on the geological and hydrological history of Jezero watershed, providing key insights into early lithification and alteration processes, crustal composition, and the preservation of its paleoenvironmental records.
In this research, we examine the role of parallel velocity shear in triggering electrostatic electron cyclotron harmonic (ECH) waves within Jupiter's inner magnetosphere. This mechanism is proposed as a complementary process to established drivers like temperature anisotropy. Using a kinetic model with a Maxwellian electron distribution, we derive the electrostatic dispersion equation incorporating parallel shear and compute linear growth rates based on key factors such as shear scale length, Perpendicular by Parallel Temperature Ratio, electron-to-ion temperature ratio, wave propagation angle, and magnetic latitude. The spatial variation of the background magnetic field is represented using a latitude-dependent dipolar magnetic field model appropriate for Jupiter’s inner magnetosphere. Our analysis reveals that intensified shear significantly boosts instability growth, with maximum rates at wavenumbers on the order of the electron gyroradius. The instability is highly responsive to near-perpendicular wave directions, moderately influenced by thermal properties, and shows minimal variation with magnetic latitude. These outcomes underscore the importance of shear-induced ECH waves in processes like electron acceleration, pitch-angle diffusion, and auroral particle loss in Jupiter's fast-rotating magnetodisk, aligning with recent satellite data on electrostatic emissions.
The EAC-1A lunar mare simulant has been selected by the European Astronaut Center (EAC) for use in large quantities in the lunar simulation testbed of the LUNA analogue facility. The material is silty sand, as classified by sieving and laser diffraction analysis. Four batches of the material have been characterised in terms of particle size distribution and subsequently tested in a resonant-column device, employing several single-stage and multi-stage tests at different stress levels to determine the dynamic shear modulus and damping over a wide strain range. To facilitate application, equations have been derived for the stress dependence of the elastic shear modulus at small strains and the nonlinear response, characterised by a decrease in shear modulus and an increase in damping at larger strains. In terms of the shear wave velocity, the small-strain results can be used to infer the in-situ regolith state from seismic velocity records; findings for the nonlinear response are relevant to terramechanical applications.
