Sazuna/UAT_keywords huggingface dataset:
Ramparts around Lakes on Titan Impact Winds and Methane Evaporation. Understanding the lake–atmosphere interactions on Titan is crucial to answering some of Titan's long-standing scientific questions, such as the unexpectedly high methane abundance close to the surface, or the "magic islands" that appear on one of the seas. Here we focus on specific lakes called Sharp-Edged Depressions, which are surrounded by high-elevation terrains called ramparts with unique structural and spectral properties. We aim at understanding how topography and surface properties around the lakes affect air–surface interactions. To study the effect of ramparts, we utilize the mtWRF model configured in 2D. We model a variety of lake morphologies: those surrounded by hills (300 m high, 30 km wide), those with no surrounding topography, and those at the bottom of a depression. To encapsulate the effects of surface properties, we vary the surface roughness, albedo, and thermal inertia. We also consider the effect of varying the background wind and the season. Our model indicates that the addition of topography creates weaker winds over the lake (≈ ‑30%) and reduces the quantity of methane evaporated (≈ ‑10%) compared to the no-topography case. However, topography results in deeper vertical transport of methane and deepens the marine layer (from a few meters to ≈ 50 m). Higher roughness (from 0.4 to 40 cm) of the ramparts tends to decrease the wind speed (≈ ‑50%) and reduces the horizontal extension of the lake breeze (≈ ‑20%). Albedo and thermal inertia variations have a negligible effect. Seasons have a strong effect on the evaporation of methane, with evaporation rates nearly 3 times higher in summer than in winter.

Keywords: Surface processes, Ocean-atmosphere interactions, Titan, Planetary atmospheres, Atmospheric dynamics, Land-atmosphere interactions
Meteoroid Streams Sculpt the Inner Zodiacal Cloud. The abundance of dust encountered by Parker Solar Probe in the inner zodiacal cloud exhibits persistent variability of ∼50% on timescales of its ∼100 day orbits. Spatial variations in the zodiacal cloud of ∼105 km, comparable to meteoroid stream cross sections, can be related to temporal variations of ∼100 days that evolve via Poynting–Robertson drag. Such density modulations manifest as only a few percent variation in line-of-sight integrated brightness, making them challenging to detect via remote imaging. We discuss multiple possible source mechanisms for this variability and propose that the presence of dense meteoroid streams that intersect and collide with the zodiacal cloud can produce the observed small-scale density modulations. Cometary disruptions may be prominent in producing these streams that collisionally interact with the zodiacal cloud.

Keywords: Zodiacal cloud
Thermal Inertia Controls on Titan's Surface Temperature and Planetary Boundary Layer Structure. Understanding Titan's planetary boundary layer (PBL)—the lowest region of the atmosphere influenced by surface conditions—remains challenging due to Titan's thick atmosphere and limited observations. Previous modeling studies have also produced inconsistent estimates of surface temperature variability, a critical determinant of PBL behavior, often without clear explanations grounded in surface energy balance. Here, we develop a theoretical framework and apply a three-dimensional dry general circulation model to investigate how surface thermal inertia influences surface energy balance and temperature variability across diurnal and seasonal timescales. At diurnal timescales, lower thermal inertia surfaces experience larger temperature fluctuations and enhanced daytime sensible heat fluxes due to less efficient subsurface heat conduction. In contrast, at seasonal timescales, surface temperature variations show weak sensitivity to thermal inertia, as atmospheric damping tends to dominate over subsurface conduction. The PBL depth ranges from a few hundred meters to 1000 m on diurnal timescales, while seasonal maxima reach 2000 m, supporting the interpretation from a previous study that the Huygens probe captured the two PBL structures. Simulated seasonal winds at the Huygens landing site successfully reproduce key observed features, including near-surface retrograde winds and meridional wind reversals within the lowest few kilometers, consistent with Titan's cross-equatorial Hadley circulation. Simulations for the planned Dragonfly landing site predict shallower thermal PBLs with smaller fluctuation amplitudes, while maintaining similar wind patterns. This work establishes a physically grounded framework for understanding Titan's surface temperature and boundary layer variability, and offers a unified explanation of Titan's PBL behavior that provides improved guidance for future missions.

Keywords: Surface variability, Planetary surfaces, Planetary boundary layers, Planetary atmospheres, Titan
On the Origin of Silicic Magmas on the Moon. The origins of lunar silicic magmas are not well understood. While clast to grain sizes of silicic materials have been returned, none of the Apollo missions visited a silicic target. Despite the availability of a wealth of remote data sets, their low spectral resolution has limited our ability to constrain the bulk composition of lunar silicic volcanic landforms and their pressure–temperature–composition (P–T–X) evolution. Here we test two proposed formation mechanisms for the formation of silicic melts using rhyolite-MELTS models. Models of crustal melting show that only 10%–20% partial melting of two likely starting compositions produces melts with &gt;60 wt% SiO2 and &lt;3 wt% total alkali compared to &gt;65 wt% SiO2 and &gt;5 wt% for returned samples. Alternatively, models of fractional crystallization of KREEP basalt residual liquids can produce silicic melt compositions with &gt;68 wt% SiO2 and &gt;7 wt% total alkali, consistent with returned silicic samples. Furthermore, thorium partitioning calculations show that the fractionated silicic melts contain &gt;60 ppm thorium, consistent with returned samples. We argue that fractional crystallization of KREEP basaltic magmas at shallow depths along a relatively high geotherm at low fO2 is the most likely formation mechanism for lunar silicic magmas.

Keywords: Theoretical models, The Moon, Lunar composition, Volcanism
The Ongoing Decline in Activity of Comet 103P/Hartley 2. We report photometric observations of Comet 103P/Hartley 2 during its 2023 apparition. Our campaign, conducted from August through 2023 December, combined data from a global network of citizen astronomers coordinated by Unistellar and the Association Française d'Astronomie. Photometry was derived using an automated pipeline for eVscope observations in partnership with the SETI Institute and aperture photometry via AstroLab Stellar. We find that the comet's peak reduced brightness, measured at  Gmin=10.24±0.47 , continues a long-term fading trend since 1991. The decline in activity follows a per-apparition minimum magnitude increase of  ΔGmin=0.59±0.11  mag, corresponding to a ∼42% reduction in brightness each return. This trend implies that the comet's active fraction has declined by approximately an order of magnitude since 1991 and may indicate that Hartley 2 is no longer hyperactive by definition. The fading is consistent with progressive volatile depletion rather than orbital effects. These results offer insight into the evolutionary processes shaping Jupiter-family comets.

Keywords: Observational astronomy, Comets
Prediction of Sulfate Hazes in the Lower Venus Atmosphere. We study the amount, size distribution, and material composition of submicron aerosol particles in the lower Venus atmosphere &lt;50 km. Our GGchem phase-equilibrium model predicts metal-chloride and metal-fluoride molecules to be present in the gas over the Venus surface in trace concentrations &lt;2 × 10‑12, in particular FeCl2, NaCl, KCl, and SiF4. Using an improved version of the DiffuDrift model developed by P. Woitke et al., we find that these molecules deposit to form solid potassium sulfate K2SO4, sodium sulfate Na2SO4, and pyrite FeS2 above about 15.5, 9.5, and 2.4 km, respectively. These heights coincide well with the three potential haze layers found in the Pioneer Venus Large Probe neutral mass spectrometer data by R. Mogul et al. The particles with radius &lt;0.3 μm can be dredged up from the ground to reach the sulfuric acid cloud base from below by diffusion. The particle density decreases from ∼5000 cm‑3 at ground level to ∼100 cm‑3 at a height of 45 km. Particles larger than about 1 μm are found to stay more confined to the ground, limited to about &lt;10 km, indicating that the larger, so-called mode 3 particles, if they exist, cannot originate from the surface. All particles are expected to be coated by a thin layer of FeS2, Na2SO4, and K2SO4. We have included the repelling effect of particle charges on the coagulation, without which the model would predict much too steep gradients close to the surface, which is inconsistent with the measured opacities. Our models suggest that the particles must have at least 100 negative charges per micron of particle radius at ground level, and &gt;50 μm‑1 at a height of 45 km.

Keywords: Dust composition, Atmospheric clouds, Surface composition, Planetary atmospheres, Venus, Atmospheric composition
Thermocompositional Layers and Jupiter's Gravity, Magnetic Field, and Supersolar Heavy Elements. Juno mission observations of Jupiter's gravity, magnetism, and richly structured atmospheric flow point to complex interior structures. Traditional models of Jupiter's interior, with one or two convecting layers and a compact core, do not plausibly satisfy the Juno gravity observations. This has opened the door to a new generation of interior models, a diversity of which satisfy the gravity data, that include nonadiabatic layering and dilute cores. In addition to nonuniqueness, Juno magnetic field observations indicating a deep dynamo, previous Galileo mission observations of atmospheric supersolar heavy-element abundances, and uncertainty regarding the prevalence of double-diffusive convection challenge the understanding of Jupiter's structure and dynamics. Here I show, using thermodynamics, previous equation-of-state-derived radial properties, and Theory of Figures to seventh order that a new Jovian interior model with a dynamo below two thermocompositional layers satisfies the Juno and Galileo observations. Invoking marginal stability, which follows from considering slowly evolving composition, reduces nonuniqueness by constraining the location of model layer boundaries. The inner, compositionally stable layer is marginally stable to semiconvection and bounded above by an outer convective zone. The outer, thermally stable, atmospheric layer is marginally stable to fingering instability and supports an inverse Z-gradient. This preferred interior model is implemented as the background state for a dynamo simulation. The magnetic and flow fields and the gravity harmonic contributions that arise from zonal flow are comparable to those of Jupiter.

Keywords: Gravitational fields, Solar system gas giant planets, Jupiter, Magnetic fields, Planetary interior, Planetary dynamics, Chemical thermodynamics
Enceladus's Tidal Heating: A Simple Approach. Saturn's moon Enceladus has a global ocean that is covered by an ice shell. The moon's eccentric orbit forces the shell to librate, which distorts the shell and thereby generates heat. The resulting tidal heating prevents the ocean from freezing, and likely drives the moon into a limit cycle, as shown in the companion paper Goldreich et al. Here we derive the tidal heating rate needed for that study. We adopt a novel approach based on energy minimization. Our derivation is thus considerably simpler than previous ones, as is the final expression for the heating rate. We also account for what happens near libration resonance. Although we focus on Enceladus, our approach may be extended to other bodies that have a similar three-layer structure, such as Europa and Titan.

Keywords: Enceladus
Extreme Forward Scattering Observed in Disk-averaged Near-infrared Phase Curves of Titan. Titan, with its thick and hazy atmosphere, is a key world in our solar system for understanding light scattering processes. NASA's Cassini mission monitored Titan between 2004 and 2017, where the derived data set includes a large number of whole disk observations. Once spatially integrated, these whole disk observations reveal Titan's phase-dependent brightness, which can serve as an analog for how hazy worlds might appear around other stars. To explore Titan's phase curve, we present a pipeline for whole disk Titan observations acquired by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) spanning 0.9–5.1 μm. Application of the pipeline finds over 4400 quality spatially and spectrally resolved data cubes that were then integrated over Titan's disk to yield phase curves spanning 2°–165° in phase angle. Spectra at near-full phase provide a useful approximation for Titan's geometric albedo, thus extending the spectral coverage of previous work. Crescent phase brightness enhancements in the Cassini/VIMS phase curves are often more extreme than analogous results seen at optical wavelengths, which can be explained by atmospheric transparency and haze scattering processes. These results provide validation opportunities for exoplanet-focused spectral models and also shed light on how extreme aerosol forward scattering could influence exoplanet observations and interpretations.

Keywords: Atmospheric effects, Planetary atmospheres, Titan
Deuterated Water Ice on the Satellites of Saturn. The deuterium-to-hydrogen ratio in water ice in a planetary body carries important information on the history of water processing and delivery in the protostellar nebula. For a giant planet satellite, the D/H ratio is also affected by the processes and temperatures of the circumplanetary or circumstellar environment in which the satellites formed. Here we present robust JWST spectroscopic detections of the 4.14 μm O–D stretch absorption line (analogous to the 3 μm water O–H stretch) on the midsized Saturnian satellites and use these detections to infer a D/H ratio on each satellite. Within the limitations of the technique, we find that all of the satellites are consistent with having a D/H ratio of about 1.5× Vienna Standard Mean Ocean Water (VSMOW), which is about an order of magnitude higher than the value of the atmosphere of Saturn. A much higher previously reported D/H ratio for Phoebe is ruled out at the 10σ level, and a 3σ upper limit of 2.3× VSMOW is obtained. The elevated D/H ratios demonstrate that the solid planetesimals and pebbles that built the satellites never sublimed and reequilibrated with the gaseous circumplanetary disk. The similarity of the D/H measurements across all satellites suggest that the D/H ratio of water ice in the vicinity of Saturn at the time of satellite formation was also approximately 1.5× VSMOW.

Keywords: Isotopic abundances, Ice spectroscopy, Saturnian satellites
Role of Natron in Delaying the Retreat of Buried Ice Tables on Ceres. (1) Ceres is the nearest ocean world to the Sun after Earth, and evidence of its extensive hydration is reflected in the wealth of data from the Dawn mission. The role that hydrated salts have played in the evolution of Ceres' near-surface hydrogen budget has not been well-understood. Examples of hydrated and dehydrated salts occur in many locations across Ceres, notably at Occator crater (∼90 km, ∼20°N), where additional hydrogen enhancement was detected during the final phase of the Dawn mission. The presence of hydrated salts in the regolith is expected to slow the retreat of the ice table. To model the effect of hydrated salts entrained in a retreating ice table, as may be the case for Ceres, we modify well-established models in which saturation vapor pressure and Knudsen diffusion play major governing roles in surface vapor mass flux. We use this modified model, with a variety of temperatures and salt contents, to constrain the delay in ice retreat time to decimeter depths, as would be relevant for nuclear spectroscopy instruments. We find that Ceres' equatorial annual average temperatures show delays in ice table retreat by a few to tens of million years, with variations due to salt content. Based on Occator's inferred age, hydrated salts are not likely to be primarily responsible for the hydrogen detected at that crater location compared to buried water ice. Ceres' current equatorial thermal regime is where the effect of salt dehydration matters the most in ice table retreat.

Keywords: Ice destruction, Planetary thermal histories, Ceres, Dwarf planets, Nuclear physics
Chemistry, Climate, and Transmission Spectra of TRAPPIST-1 e Explored with a Multimodel Sparse Sampled Ensemble. TRAPPIST-1 e is one of a few habitable zone exoplanets that is amenable to characterization in the near term. In this study our motivations are both scientific and technical. Our technical goal is to establish a multimodel sparse sampled ensemble approach for coherently exploring large unconstrained parameter spaces typical in exoplanet science. Our science goal is to determine relationships that connect observations to the underlying climate across a large parameter space of atmospheric compositions for TRAPPIST-1 e. We consider atmospheric compositions of N2, CO2, CH4, and H2O, with water clouds and photochemical hazes. We use a 1D photochemical model, a 3D climate model, and a transmission spectral model, filtered through a quasi‑Monte Carlo sparse sampling approach applied across atmospheric compositions. While clouds and hazes have significant effects on the transmission spectra, CO2 and CH4 can be potentially detected in ≤10 transits for certain compositional and climate states. Colder climates have better prospects for characterization, due to being relatively dry and having fewer clouds, permitting transmission observations to probe more deeply into their atmospheres. CH4 volume mixing ratios of ≥10‑3 trigger strong antigreenhouse cooling, where near-IR absorption simultaneously creates an inversion in the stratosphere and reduces the stellar radiation reaching the planet surface. In such cases, interpreting the disk-averaged emission and albedo at face value can yield misleading conclusions, as here low albedo and high thermal emission are associated with cold planets. Future work will use our sparse sampling approach to explore broader parameter spaces and other observationally amenable exoplanets.

Keywords: Computational methods, Planetary climates, Exoplanet atmospheres
The Lunar Instrumentation for Subsurface Thermal Exploration with Rapidity (LISTER) on Blue Ghost Mission 1 to Mare Crisium. I. Pneumatic Excavation of Regolith. The Lunar Instrumentation for Subsurface Thermal Exploration with Rapidity (LISTER) is the first robotically deployed subsurface thermal probe that actively excavates lunar regolith and makes scientific measurements at multiple depths. It was deployed in Mare Crisium on Blue Ghost Mission 1 in 2025 March, reached 1 m depth, and measured the temperature and thermal conductivity of the regolith at eight different depths. The previous depth record for robotic in situ thermal measurements of the Moon was 8 cm. LISTER utilizes the pneumatic excavation technique, blowing a jet of pressurized nitrogen gas, as it pushes its thermal probe into the regolith. The gas expands rapidly in the lunar vacuum and lofts regolith clumps and clasts out of the hole. When the probe reaches one of the depths targeted for thermal measurements, LISTER stops blowing gas and pushes the probe into the yet-to-be-excavated bottom-hole regolith. It completes the necessary thermal measurements in 2 hr and then resumes excavation to the next targeted depth. LISTER detects obstacles on its way by monitoring the weight on bit (WOB). When the WOB exceeds a programmable threshold, LISTER attempts to dislodge the obstacle by automatically performing a piston-like vibratory movement ("dithering"), while it keeps blowing gas. Finally, video-monitoring the ejecta from LISTER's excavation operations is useful in studying the stratigraphy of the regolith.

Keywords: The Moon, Lunar regolith
Brownian Motion of Main-belt Asteroids on Human Timescales. High-precision astrometric data on main-belt asteroids (MBAs) enable new inferences on the gravitational and nongravitational forces present in this region. We estimate the typical Brownian motion due to mutual encounters among MBAs that cannot be predicted from the ephemeris of larger bodies and therefore serves as noise on inferences from the MBAs. The rms azimuthal shift σϕ of this "Brownian noise" is predicted using the distribution of known MBA orbits, combined with analytical propagation into future positional uncertainties—radial and vertical perturbations are much smaller. At current levels of asteroid-mass knowledge, we estimate that σϕ accumulates to 2–9 km, or 1–5 mas over T = 10 yr, increasing as T3/2. This must be taken into consideration for proper inferences from Gaia astrometry. Legacy Survey of Space and Time (LSST) data will, however, improve MBA mass knowledge enough to lower this Brownian uncertainty to 260–400 m, or 140–210 μas, which in many but not all cases could be small enough to ignore in inferences using Gaia or LSST astrometry of MBAs. For full exploitation of Gaia and LSST MBA data, ephemeris models should include the ≈10,000 largest asteroids as active bodies with free masses, even if not all are well constrained. This will correctly propagate the uncertainties in these bodies' gravity into desired inferences. The rms value of deflections from less massive MBAs is then just σϕ ≈ 17–60 m, or 9–40 μas, depending on the mean mass of the MBAs at fixed absolute magnitude small enough to ignore until occultation-based position data become ubiquitously available for MBAs.

Keywords: Main belt asteroids, Ephemerides, Astrometry, Asteroid dynamics
Barnard Crater, Mars: Evidence of Glaciofluvial Activity in a Large, High-latitude Impact Crater in Southern Hellas. Barnard, a 121.1 km diameter crater along the southern rim of Hellas basin, is a well-preserved complex crater with a history of burial, excavation, and fluvial/glacial activity on its floor and walls. The interior of Barnard shows ice-rich deposits similar to other mid-to-high-latitude craters on Mars but is distinctive in that it also contains sinuous ridges. We have completed a geologic map of Barnard and surrounding materials using the global CTX mosaic. Mapping has identified and shown the distribution of features including sinuous ridges and fluvial channels, attributed to subglacial melting, and lobate debris aprons, mantling deposits, and arcuate ridges, indicative of the deposition and mobilization of ice within the crater. We have identified 13 geologic units on and around Barnard, including three distinct floor units, suggesting sustained periods of infill. We have conducted topographic and morphometric analyses using MOLA and HiRISE DTMs across Barnard and its interior landforms, which show significant infill on the crater floor (∼1 km thick), and local excavation of floor deposits indicating continued modification. Lobate debris aprons extending from the crater walls have maximum thicknesses of ∼300–350 m. Sinuous ridges on the crater floor range in height from ∼10 to 20 m. Crater counts on Barnard's ejecta show that it formed ∼3.81 Ga in the Middle to Late Noachian, with subsequent periods of infill, excavation, fluvial, and wet-based glacial activity modifying its interior during the Late Hesperian/Early Amazonian, followed by further deposition and flow of ice-rich materials between ∼400 and 16 Ma into the Late Amazonian.

Keywords: Geological processes, Mars, Planetary geology