Sazuna/UAT_keywords huggingface dataset:
The Influence of Internal Structure on Physical Outcomes of the 2029 Apophis Close Approach with Earth. The 2029 close approach between asteroid 99942 Apophis and Earth represents a unique opportunity to study the influence of tidal encounters on the deformation and rotational evolution of an S-complex near-Earth object in the 0.1─1 km size range—a class of object of particular interest to the planetary defense community. The encounter may give insight into the internal structure of the body, presenting an opportunity for our first direct probe of an asteroid's interior. We present results from numerical simulations of the Apophis─Earth tidal encounter, modeling Apophis as a self-gravitating granular aggregate of meter-sized spherical particles, with the aim of constraining measurable rotation change, deformation, and seismicity induced in Apophis during the encounter, in support of potential rendezvous missions. We vary particle size distributions, particle shapes, packing configurations, and interior structures (with large embedded cores) to examine the effects that internal structure has on these measurable encounter outcomes. We find that the packing configuration with the lowest shear strength exhibits the most deformation by a factor of 4 over the most compact configuration, and the presence of internal cores in a low shear strength configuration can reduce the stress felt by the asteroid. We also find that short-period seismic events are likely to occur in the shallow subsurface layers of the body in the hours just following the time of perigee. These events have amplitudes on the order of 10−4 m s−2 Hz−1/2 in the 0.1─1 Hz range, which should be measurable with the latest seismic instruments developed for asteroid interior characterization.

Keywords: Near-Earth objects, Tidal interaction, Close encounters, Asteroid dynamics
LROC NAC-derived Meter-scale Topography of the Moon's South Polar Landing Sites: Digital Terrain Models and Their Quality Assessments. High-quality digital terrain models (DTMs) are essential for lunar polar missions, aiding mission planning and surface operations. The horizontal resolution and vertical accuracy of DTMs are generally limited by factors such as source image resolution, image noise, the precision of ground control points (GCPs), and data processing techniques. In this study, we produced advanced DTMs for the lunar south pole region by integrating seamless mosaics generated from multiple Lunar Reconnaissance Orbiter Camera Narrow Angle Camera image pairs captured under various illumination azimuths. To enhance accuracy and reduce artifacts, we employed bundle adjustment with hundreds of meticulously selected image-to-image tie points and precise GCPs, combined with an advanced multiview shape-from-shading technique. This technique, which utilizes multiple viewpoints to resolve topographic details with higher precision, significantly improves vertical accuracy and resolution. Our methodology achieves a spatial resolution of 1 m pixel−1 and vertical precision of ±1.0 m, enabling clearer delineation of meter-scale lunar topographic features compared to previous models. These DTMs are expected to significantly support the Lunar Polar Exploration project and other forthcoming lunar exploration missions.

Keywords: Photogrammetry, Remote sensing, Lunar surface
Water Transport from Enceladus to the Rings. Enceladus continuously ejects approximately 300 kg s−1 of water vapor from its south polar regions, forming an extensive neutral gas torus around Saturn. In this study, we use the direct simulation Monte Carlo method to model the detailed spatial structure of this neutral torus, explicitly incorporating major loss processes, including photolysis, charge exchange, and electron-impact reactions. Our results demonstrate that molecular collisions and chemical reactions significantly enhance the radial and vertical spreading of water-group molecules within the Saturnian system. Specifically, our calculations indicate that 40% of the water-group neutrals emitted by Enceladus' plumes impact Saturnian rings, with a roughly estimated deposition of 0.03 mm of icy material over one million years. These findings provide insight into the physical and chemical processes that govern Enceladus' neutral torus environment, including implications for the composition of rings and their evolution.

Keywords: Saturn, Monte Carlo methods, Enceladus, Planetary rings, Saturnian satellites
First Passive Permittivity Measurement of Lunar Regolith Simulant at Terahertz Band. This study presents the first passive measurements of the relative polarization ratio (RPR) and apparent bulk permittivity (ABP) of lunar regolith simulants at approximately 280 GHz. We prepare anorthositic and basaltic simulants with both optically flat surfaces and surfaces with roughness equivalent to typical lunar surface roughness represented by the Chang'E-4 landing site and conduct passive measurements to verify whether the RPR and ABP follow Fresnel's law. For flat-surfaced samples, the results confirm that the relationship between RPR, incidence angle, and ABP is consistent with the Fresnel-derived relationship. The ABP values are 1.91 and 2.40 for the anorthositic and basaltic simulant, respectively. Importantly, even for rough-surfaced samples, which incorporate surface scattering effects, the results demonstrate that the relationship between RPR, incidence angle, and ABP remains consistent with the Fresnel-derived relationship. This is the first experimental confirmation that passive observation can estimate the ABP of lunar regolith using the Fresnel-derived relationship, even with lunar surface roughness. Furthermore, the permittivity differences originating from the inherent bulk density and chemical composition of the samples are preserved despite the surface roughness. These findings suggest that passive polarimetric remote sensing, such as that employed by the TSUKIMI mission, can effectively estimate the ABP of the lunar surface and provide insights into identifying regions with potential for resource exploration.

Keywords: Lunar regolith, Experimental data, Lunar science, Lunar surface, Remote sensing, Radar observations, Planetary geology
Modeling the Solar System. I. Characterization Limits from Analytic Timing Variations. Planetary systems with multiple transiting planets are beneficial for understanding planet occurrence rates and system architectures. Although we have yet to find a solar system (SS) analog, future surveys may detect multiple terrestrial planets transiting a Sun-like star. In this work, we simulate transit-timing observations of our system based on the actual orbital motions of Venus and Earth + Moon (EM)—influenced by the other SS objects—and retrieve the system's dynamical parameters for varying noise levels and observing durations. Using an approximate coplanar N-body model for transit-time variations, we consider test configurations with two, three, and four planets. For various observing baselines, we can robustly retrieve the masses and orbits of Venus and EM, detect Jupiter at high significance (for &lt;90 s timing error and baseline ≤15 yr), and detect Mars at 5σ confidence (with &lt;20 s timing error and baseline ≥27 yr) using TTVFaster. We also find that the three-planet model is generally preferred, and we provide equations to estimate the mass precision of Venus/Earth/Jupiter analogs. The addition of Mars—which is near a 2:1 mean-motion resonance with Earth—improves our retrieval of Jupiter's parameters, suggesting that unseen terrestrials could interfere in the characterization of multiplanetary systems. Our findings are comparable to theoretical limits based on stellar variability and may eventually be possible.

Keywords: Exoplanet detection methods, Astrobiology, Transit timing variation method, Solar system planets
Investigating Local- and Global-scale Dust Redistribution on Comet 67P/Churyumov─Gerasimenko. We use a 3D dynamical Monte Carlo model to simulate the trajectories of individual dust grains and map their redeposition across the surface of comet 67P/Churyumov─Gerasimenko. These simulations are used to characterize spatial variations in fallback patterns, as well as the global and regional mass balance resulting from sublimation-driven erosion. We find that dust redeposition is highly heterogeneous, strongly influenced by the comet's topography and rotational dynamics. Enhanced accumulation occurs along the leading edges of both the large and small lobes, while gravitational lows such as the Hapi region act as persistent dust sinks. Despite localized deposition, most areas of the nucleus experience net mass loss over an orbit, with sublimation-driven erosion dominating the overall surface evolution. In particular, the southern hemisphere exhibits limited dust accumulation, consistent with its stronger seasonal activity. Additionally, our model reproduces the asymmetric erosion of large pits based on their orientation, supporting the idea that pit walls can expand laterally while maintaining circular morphology. These results highlight the importance of global shape, rotation, and seasonal forcing in governing dust redistribution and landscape evolution on cometary nuclei.

Keywords: Comet nuclei, Comets, Small Solar System bodies
High-temperature He<SUP>+</SUP> Irradiation of Low-iron-bearing Olivine: Laboratory Simulations of Space Weathering on Mercury. The surface of Mercury is highly space weathered, and the products of space weathering are different than on the Moon. Here we simulate the interaction of solar wind ions with the surface of Mercury by implanting low-iron-bearing (∼3 wt% Fe) olivine slices with 4 keV He+ ions both under ambient conditions and at 450 °C during the irradiation. The sample irradiated under ambient conditions shows a ∼140 nm thick partially amorphous layer on top of the grain with high concentrations of bubbles and cavities. However, the sample irradiated at 450 °C has a 110─140 nm thick polycrystalline layer with 1─5 nm sized nanoparticles of metallic iron and no bubbles or cavities. Mg atoms are preferentially sputtered from the ion-damaged layer present on the sample irradiated under ambient conditions, but no difference in composition is seen between the crystalline olivine and the ion-damaged layer in the sample irradiated at 450 °C. In addition, a thin amorphous film deposited on a micro-electromechanical systems─based chip is heated up to 1200 °C in situ inside a transmission electron microscope for a few milliseconds, and it produced nanoparticles of size 5─30 nm. Our results show that solar wind irradiation of low-iron-bearing olivine in the equatorial regions of Mercury will produce nanoparticles of iron whose sizes will be larger than that on the surface of the Moon and that the size will further increase during impacts of dust particles. Solar-wind-implanted He can diffuse out of regolith grains and can be a source of He observed in the exosphere of Mercury.

Keywords: Solar wind, Planetary surfaces, Mercury (planet)
Synchronous Rotation in the (120347) Salacia─Actaea System. We report on roughly 16 yr of photometric monitoring of the trans-Neptunian binary system (120347) Salacia─Actaea, which provides significant evidence that Salacia and Actaea are tidally locked to the mutual orbital period in a fully synchronous configuration. The orbit of Actaea is updated, followed by a Lomb─Scargle periodogram analysis of the ground-based photometry, which reveals a synodic period similar to the orbital period and a peak-to-peak lightcurve amplitude of ∆m = 0.0900 ± 0.0036 mag (1σ uncertainty). Incorporating archival Hubble Space Telescope photometry that resolves each component, we argue that the periodicity in the unresolved data is driven by a longitudinally varying surface morphology on Salacia, and we derive a sidereal rotation period that is within 1σ of the mutual orbital period. A rudimentary tidal evolution model is invoked that suggests synchronization occurred within 1.1 Gyr after Actaea was captured/formed.

Keywords: Tidal friction, Asteroid satellites, Trans-Neptunian objects
JWST Spectroscopy of a Blue Binary Cold Classical Kuiper Belt Object. We present observations of two binary systems within the cold classical region of the Kuiper Belt—2001 XR254 and 2016 BP81—obtained with the JWST Near-Infrared Spectrograph. The measured reflectance spectrum of 2001 XR254 is characteristic of the red cold classicals, with strong features due to carbon dioxide, carbon monoxide, and methanol ices. In contrast, 2016 BP81 is a blue binary, with a spectrum that shows prominent water-ice absorption bands. The two components of the 2016 BP81 binary display identical spectral profiles, consistent with coeval formation from gravitational collapse. Through qualitative and quantitative comparisons of Kuiper Belt objects (KBOs) with similar spectral profiles dominated by water-ice features, we identify a small cluster, including 2016 BP81, that differs in systematic ways from the rest of the population. The relatively deep carbon dioxide ice absorption bands, different water-ice band-depth ratios, and possibly enhanced signatures of aliphatic organics suggest that objects in this cluster may have originated in a distinct formation environment from the other water-type KBOs. The implications of our findings are discussed within the context of recent models of Kuiper Belt formation and evolution.

Keywords: James Webb Space Telescope, Surface composition, Kuiper belt, Trans-Neptunian objects
Watching a Comet Turn On: High Spectral Resolving Power Observations of Comet C/2017 K2 (PanSTARRS). We report high spectral resolving power optical observations of comet C/2017 K2 (PanSTARRS) as it approached the Sun. This comet was discovered when it was 16 au from the Sun. At discovery, the comet had a large and relatively bright coma. However, the spectrum at discovery showed only signatures of dust. We used the coudé spectrograph on the McDonald Observatory 2.7 m telescope to obtain spectra, starting when the comet was at a heliocentric distance of 5.06 au and following it until 2.47 au, to determine what spectral features would appear at each heliocentric distance. The first heliocentric distance for which we detected any emission from the gas was 3.39 au, when we first detected CN. As the comet continued inward toward the Sun, various other species were detected. We discuss the implications of the early turn-on of CN compared with the assumed water turn-on distance of 3 au. We also found that different species first appeared at different heliocentric distances.

Keywords: High resolution spectroscopy, Long period comets, Comets, Comae
A Dust Halo from Saturn's Main Rings Extending Several Saturnian Radii above the Ring Plane. During the Grand Finale orbits, the Cassini spacecraft orbited Saturn with high inclinations and perikrones near the ring plane crossings. The Cosmic Dust Analyzer sampled ice and mineral dust particles during these orbits. In previous work, time-of-flight mass spectra of ring debris close to the ring plane have been analyzed, with the main finding that the detected submicron mineral dust particles consist mostly of Fe-depleted silicates. Here we investigate silicate particles detected at unexpectedly high latitudes of up to 3 Saturnian radii (RS) distance above and below the ring plane. We find striking compositional similarities to those detected close to the main rings, suggesting that these silicates could likewise originate from there. The spatial distribution of lifted main ring material can roughly be constrained to the radial extent of the rings themselves. From there outward water-ice particles become dominant, indicating a vertical E ring extension to 3RS distance to the ring plane here. Using dynamical simulations, we examine conditions under which main ring particles could be ejected to these surprisingly high latitudes. We identify a plausible scenario by assuming ejection velocities of &gt;25 km s─1 and radii &lt;20 nm, allowing for trajectories bent by electromagnetic forces. Such high ejection velocities may be explained if the observed particles form from condensation of a fast vapor phase after micrometeoroid impact onto the rings, a mechanism that has recently been suggested to indeed eject preferably silicate material in the observed size range from the water-ice-dominated rings of Saturn.

Keywords: Saturn, Dust composition, Planetary rings
Infrared Spectra of Organic and Salt-bearing Ices under Titan Conditions: Constraints on Detection of Ocean Materials. Titan, with its organic-rich atmosphere and global subsurface ocean, has long been considered a prime candidate to potentially host life beyond Earth. The detection of species frozen within ocean fluids when extruded on the surface via cryovolcanism, crust-breaching impacts, or other means, presents an intriguing possibility for the characterization of the ocean composition and its habitability. On Titan, in situ spectra of organic- and salt-bearing ices could serve as evidence of life in the ocean and reveal the presence of salts or other nutrients. To this end, we present infrared (IR) reflectance spectra of organic- and salt-bearing ices under Titan surface conditions. For a subset of these species, a dilution series of spectra is presented to begin to constrain the limits of detection for Titan. Ultimately, this work shows that IR reflectance spectroscopy has little hope of detecting such species frozen in water ice from orbit, or even from a landed spacecraft, due to the low expected concentrations of these target species. The effect of abundant IR absorbers in the atmosphere presents an additional complicating factor. Such detections would require more sensitive in situ analytical techniques such as fluorescence or mass spectrometry, along with the sampling systems that such methods would require.

Keywords: Astrobiology, Titan, Infrared spectroscopy, Complex organic molecules
Jupiter's Tropical Atmosphere: Shallow Weather, Deep Plumes, and Vortices. Towering storms, swirling clouds, and vortices are the cloud top manifestation of complex weather systems shaping the atmosphere of Jupiter. We use observations from Juno's MicroWave Radiometer (MWR), the Karl G. Jansky Very Large Array, and the Hubble Space Telescope to probe for the first time the depth and impact of weather on Jupiter. We use ammonia, the main source of opacity at radio wavelengths on Jupiter, as the tracer for the weather by fitting ammonia anomalies to the MWR brightness temperature variations. We show that most of the weather—defined here as longitudinal deviations in ammonia concentration from the zonal mean—is concentrated in regions near cloud formation. Both the South Equatorial Belt and the Equatorial Zone have surprisingly shallow weather systems (P &lt; 2 bars), and even in the North Equatorial Belt most of the ammonia variations are above the water condensation level (P ∼ 6 bars). This confirms that the water condensation layer plays a crucial role in controlling the dynamics and the weather on Jupiter. Three features, however, extend below the water condensation layer: a vortex in the northern hemisphere reaching down to 30 bars, an ammonia plume down to 20─30 bars, and the signature of ammonia fallout down to 20 bars. This work confirms that an interplay of large-scale processes (vortices, plumes) and small-scale processes (storms) is responsible for shaping the global atmospheric makeup of Jupiter.

Keywords: Very Large Array, Atmospheric structure, Hubble Space Telescope, Jupiter, Atmospheric dynamics, Radio astronomy
Isolating the Gravitational Influence of Uranus's Winds Requires Close Passages Inward of the Rings. Close orbits by the Uranus Orbiter and Probe (UOP) could be used to deduce Uranus's multipolar gravity field to a higher precision and angular degree than the J2 and J4 currently measured from ground-based ring occultations and the Voyager 2 flyby. We examine Jn sensitivity limits obtained from simulations of candidate UOP trajectories, pairing these with Uranus interior and wind models to perform retrievals from the gravity moments. We consider zonal wind profiles derived from recent feature-tracking data, assuming that zonal winds extend into the planet along cylinders, with a radial decay function similar to those that explain Jupiter and Saturn gravity. Present knowledge of J2 and J4 permits a fairly wide range of possible wind depths in Uranus, up to 1800 km or 7% of the planet's radius. Measuring additional gravity moments is essential to separate this unknown wind depth from other interior properties of interest, but J6 is found to be too dominated by bulk rotation to be a useful probe of the wind depth. Odd moments arising from Uranus's observed north─south asymmetric flow are strong functions of the wind depth, but the usefulness of J3 is hindered by its sensitivity to present uncertainties in the wind profile. The even moment J8 or the odd moments J5 and J7 are the best probes of the depth of Uranus's winds. J8 and, most likely, J5 and J7 are measurable in a highly inclined orbit making ≳10 pericenter passages inward of the ζ ring, approximately 1000─2500 km above Uranus's cloud tops.

Keywords: Orbiters, Gravitational fields, Oblateness, Atmospheric dynamics, Planetary interior, Uranus
VIPER's Mass Spectrometer Observing Lunar Operations (MSolo). The Volatiles Investigating Polar Exploration Rover (VIPER) is a lunar volatiles detection and measurement mission that will land on Mons Mouton near Nobile crater, close to the Moon's south pole. One of the analytical instruments embedded within the rover is the Mass Spectrometer observing lunar operations (MSolo) instrument. VIPER's data will ultimately be used to create lunar water resource maps that may enable a sustained presence on the lunar surface. As VIPER navigates several kilometers of terrain, its onboard analytical instrumentation will characterize the presence of volatiles along the traverse path and identify candidate locations for drilling. Upon selection of a drilling site, the rover will position itself and deploy an auguring, percussive drill down to 1 m depth. Upon extraction, regolith cuttings captured by the auger are deposited on the surface, an activity that will initiate the release of any volatile gases that are subsequently detected and quantified by MSolo. MSolo is designed to identify low-molecular-weight volatiles (between m/z 1 and 100) with unit mass resolution. Volatiles of interest include D/H and O18/O16-bearing species, including possible water contained within the lunar regolith. MSolo is a modified commercial off-the-shelf system, meaning the instrument is based on a commercially available unit that has been ruggedized for space applications.

Keywords: Quadrupole mass spectrometry, The Moon
Effect of Regolith─Ice Stratigraphy and Laser Weathering on Ultraviolet─Visible─Near-infrared Detection of Lunar Water Ice. Investigating volatiles is critical for understanding their delivery to the Moon and for their potential as a resource for sustained lunar exploration. Water ice and potentially other volatiles are known to exist in and proximal to permanently shadowed regions (PSRs). However, their form, distribution, abundance, and regolith stratigraphy remain poorly understood. NASA's Artemis program, along with international missions, seeks to address these knowledge gaps with observations at different scales (e.g., from orbit and surface operations). In this study, we replicated three distinct ice stratigraphies in a cryogenic, vacuum environment analogous to PSRs. We then measured the ultraviolet─visible─near-infrared (UV─vis─NIR) reflectance spectra of the volatile-rich samples before and after subjecting them to laser weathering. Our findings reveal that near-surface stratigraphy and weathering phenomena significantly affect the detectability of ice. Hence, spectra from our analog regolith─ice stratigraphies provide a foundational reference for interpreting data from future missions that aim to detect water using UV─vis─NIR reflectance techniques.

Keywords: Space weather, Lunar surface, Ice spectroscopy, Infrared spectroscopy