Sazuna/UAT_keywords huggingface dataset:
Equatorial Waves Associated with Dust Storms as Simulated in a Mars General Circulation Model. Equatorial atmospheric waves provide a mechanism for variability on a wide range of timescales and for disturbances in one part of the tropics to influence other tropical locations around the globe. A Mars general circulation model is used to investigate how equatorial waves behave under different atmospheric dust loading scenarios and when perturbed by dust storms. Such waves may be important for understanding triggering of distant dust storms or additional dust lifting centers within large storms. Equatorial waves appear to change when dust storm sequences cross the equator or when background dust amounts significantly vary, with eastward- and westward-propagating waves within a wide spectral interval being amplified in general. Specifically, many low-frequency, long-wavelength equatorial waves become prominent during prescribed dust storm episodes. Their horizontal wave structures seen in the 100 Pa geopotential field show a resemblance to equatorial Rossby, Kelvin, and mixed Rossby─gravity waves. Waves with different wave periods and zonal wavenumbers evolve with time and interfere with each other, leading to complex time-dependent eddy patterns. This study shows that both dust storms and background dust can significantly influence the spectra and structures of eddies in the tropical Martian atmosphere.

Keywords: Mars, Atmospheric dynamics, Solar system terrestrial planets, Atmospheric circulation
Coupled 1D Chemical Kinetic Transport and 2D Hydrodynamic Modeling Supports a Modest 1─1.5× Supersolar Oxygen Abundance in Jupiter's Atmosphere. Understanding the deep atmospheric composition of Jupiter provides critical constraints on its formation and the chemical evolution of the solar nebula. In this study, we combine 1D thermochemical kinetic-transport modeling with 2D hydrodynamic simulations to constrain Jupiter's deep oxygen abundance using carbon monoxide as a proxy tracer. Leveraging a comprehensive chemical network generated by the Reaction Mechanism Generator, we assess the impact of updated reaction rates, including the often-neglected but thermochemically significant Hidaka reaction (CH3OH + H →CH3 + H2O). Our 1D─2D coupled approach supports a modest supersolar oxygen enrichment of 1.0─1.5× the solar value. We also present a method for deriving Jupiter's eddy diffusion coefficient (Kzz = 3 × 106−5 × 107 cm2 s−1) from 2D hydrodynamic simulations using the quasi steady-state approach. This method is applicable to exoplanet atmospheres, where Kzz remains highly uncertain despite its strong influence on atmospheric chemistry. Finally, our results imply a significantly elevated planetary carbon-to-oxygen (C/O) ratio of ∼2.9, highlighting the importance of clarifying the mechanisms behind the preferential accretion of carbon-rich material during Jupiter's formation. By integrating thermochemical and hydrodynamic processes, our study offers a more complete framework for constraining chemical and dynamical processes in (exo)planetary atmospheres.

Keywords: Planetary atmospheres, Jupiter, Protoplanetary disks, Atmospheric composition, Planet formation
On the Border: Searching for Cometary Activity near the Centaur─JFC Transition Line. Current wide-field surveys discover ∼15 Jupiter-family comets (JFCs) each year, typically identified via visual detection of a dust coma or tail. The same surveys also discover many asteroids that have distant JFC-like orbits, but with no reported activity. We observed asteroids on Jupiter-crossing orbits beyond the depth of typical survey imaging using the 2.5 m Isaac Newton Telescope. We used deep imaging to observe 16 asteroids in this region, plus seven known comets for comparison. Three asteroids (2011 WM183, (669525) 2012 XO144, and 2020 RX133) showed surface brightness profiles consistent with low-level activity, equating to ∼19% of our total sample. We note that 2020 RX133 is a Jupiter Trojan. When we considered the heliocentric distance range of the asteroids at the time when they showed activity, this fraction increased to 33% of the targets in the 3.16 au ≤ Rh ≤ 4.56 au region, and therefore it is possible to infer that at least ∼30 asteroids with TJ ≤ 3.05 and in the 4.05 au &lt; a &lt; 5.05 au parameter space may potentially exhibit low-level activity. We also estimated nuclear radii for the three active targets of rn = 1.8 ± 0.2 km, rn ≤ 0.8 km, and rn ≤ 0.5 km for (669525) 2012 XO144, 2011 WM183, and 2020 RX133, respectively. The median color index for the observed asteroids is (g − r)PS1 = 0.52 ± 0.13, aligning with those expected for D-type asteroids.

Keywords: Small Solar System bodies, Centaur group, Asteroids, Short period comets, Solar system, Jupiter trojans, Comets
3D Reconstruction of DART Ejecta at Dimorphos Reveals an Anisotropic, Filamentary Structure. We present a 3D reconstruction of the ejecta plume generated by the DART impact on Dimorphos based on LUKE images acquired by LICIACube. Using adaptive histogram equalization and geometric coregistration from multiple vantage points, we identified and tracked extended ejecta features and reconstructed their 3D spatial distribution with a voxel-based method. The reconstructed ejecta field shows strong anisotropy. An azimuth-matched comparison with the published elliptical cone highlights coherent, direction-dependent departures from a simple conic surface, despite broad agreement on the global cone orientation. This quantifies nonaxisymmetric structures that cone models cannot capture. We derived lower limits to ejecta velocities ranging from 20 to 50 m s−1, consistent with numerical simulations of hypervelocity impacts into weak, porous targets. Compared to laboratory experiments, these values correspond to few-meter launch depths, suggesting a significant role of near-surface boulders in the ejecta distribution. Complementing this ejecta filament analysis, we studied 105 isolated comoving diffuse ejecta features, tracked up to 7 km from the impact site. These features followed highly tangential (85∘─92∘ from the impact direction) trajectories relative to Dimorphos's surface. Their velocity distribution peaks around 50 m s−1, indicating that crater excavation persisted throughout the imaging sequence. Our results challenge and refine previous cone-based ejecta distribution models, offering new insights into the complex nature of impact-induced ejecta and improving constraints relevant for planetary defense strategies. Given these new insights, we urge the designers of future planetary defense missions to take into consideration anisotropic ejecta models for more realistic estimates of the imparted momentum via a kinetic impactor technique.

Keywords: Impact phenomena, Near-Earth objects, Ejecta, Space probes, Asteroids, Planetary science
Similar Topography and Crater Retention Record yet Divergent Space Weathering Extents across Reiner Gamma on the Moon. Electrostatic levitation and migration of charged dust may occur during the formation of lunar swirls. Due to interaction between crustal magnetic anomalies and solar wind, immature fine-grained particles are predicted to preferentially migrate to bright on-swirl regions, yielding smaller elevation differences compared to dark off-swirl regions with time and also larger contrast of space weathering extents. Here we report that the off-swirl and on-swirl regions of Reiner Gamma, a representative lunar swirl, do not exhibit systematic elevation differences of over 2 m or distinct crater retention records at D ≥ 10 m. Surface regolith and fresh crater ejecta in on-swirl regions exhibit comparable reflectance spectra, but those of the surface regolith have shallower absorption bands and redder spectral slopes. Dark lanes sandwiched by on-swirl regions exhibit intermediate extent of space weathering compared to the background mare and on-swirl regions. The results indicate that dust migration either did not occur or yielded little topographic changes during the formation of Reiner Gamma, and deflection of solar wind by the local magnetosphere alone suffices to explain its origin.

Keywords: Lunar magnetic fields, Lunar features
Interaction of Solar Wind Energy Helium Ions with Enstatite Surfaces Progressively Altered by Simulated Impact Melting. The interactions between micrometeoroid impacts and solar wind on the surface of the Moon remain a major area of investigation in the space weathering field. In this study, we first irradiated Fe-bearing enstatite [(Mg,Fe)2Si2O6] (1.50 at% Fe) with a nanosecond-pulse UV excimer laser (λ = 248 nm) to simulate micrometeoroid impacts, using fluences above and below the ablation threshold to produce four different impact-processed regions. Next, we irradiated the surfaces with 4 keV He+ to explore how prior impact processing changes the way solar wind ions interact with mineral surfaces. We performed comprehensive micro-scale to nano-scale characterization of the experimental products using scanning electron microscopy, scanning transmission electron microscopy, electron energy loss spectroscopy, and energy dispersive X-ray spectroscopy. In the samples irradiated above the ablation threshold, we observed the coexistence of nanophase Fe (npFe0) and Fe3+-bearing glass, indicating that npFe0 formation was driven by charge disproportionation. In the sample irradiated at the highest laser fluence, we produced helium-bearing vesicular npFe0, an enigmatic space weathering product known to occur widely on the Moon. Finally, we show that the temperature of impact melting and the phases produced by impact processing have a direct influence on the target's sputtering behavior and overall helium capture capacity. Our findings demonstrate that micrometeoroid impacts play a critical role in modifying the crystal structure and chemistry of regolith grain surfaces and that variation in impact processing can fundamentally shift the subsequent interactions that solar wind ions have with affected surfaces.

Keywords: Planetary surfaces, Micrometeoroids, Surface processes, Solar wind, Experimental techniques, Regolith
Impact-induced Contamination of Ganymede's Deep Ice Shell. Juno flew by Ganymede in 2021 June and measured the microwave brightness temperatures of the ice shell at six frequencies from 0.6─22 GHz. Based on the increasing brightness temperature with wavelength, S. Brown et al. (2023) derived a geothermal temperature gradient of 1 K km−1. However, this assumes a very high purity ice shell up to ∼20 km thick. In this work, we estimate the amount and extent to which impurities introduced by cometary impactors into Ganymede's ice shell will affect the attenuation, which has implications for the temperature gradient. We assume that in each impact event, the broken-up impactor and target material will reaccrete onto the surface. Many impact events thus emplace a surface layer that is a nearly homogeneous mix of the impactor (∼50/50 ice/rock by mass) and disrupted target material. We use estimates of impactor flux and size spectrum from the literature to calculate that this globally emplaced layer is 3.8─107.0 km in thickness with impurity (silicate) concentration 3.6−5.2 mass%. The consequent increase of attenuation implies a temperature gradient ≫1 K km−1, which is unrealistically large given the current heat source of Ganymede is the radiogenic heat production of the rocky component. Therefore, Juno microwave results and our calculations of impact-induced dirtiness of the ice shell together place a strong constraint on the upper bound of the dirt in the ice shell and, hence, an upper bound on the total impactor flux on Ganymede from the time of the late heavy bombardment period to be &lt;5.5 × 1019 kg.

Keywords: Impact phenomena, Ganymede
Reliability of Assessing Lunar Crustal Density Structures Using the GRAIL Gravity Model. The spatial resolution of gravity data acquired by the Gravity Recovery and Interior Laboratory (GRAIL) mission is adequate to resolve relatively small-scale density structures larger than approximately tens of kilometers within the lunar crust, which record important information about lunar geological evolution invisible from the surface. Band-limited spherical harmonic (SH) expansion is frequently employed to separate gravity signals induced by small-scale crustal density structures from those generated by large-scale structures. However, this procedure inevitably introduces ringing artifacts, i.e., the Gibbs effect. The potential effects of the Gibbs phenomenon on the identification and interpretation of lunar crustal density structures remain understudied. Here we investigate this effect by modeling gravity signals of density structures in both the lunar crust and mantle, with additional consideration of uncertainties of the GRAIL gravity data. The modeled density structures include shallow dense intrusions and deeper mantle uplifts with diverse geometries. Model results show pronounced effects of the Gibbs phenomenon on the high-pass-filtered gravity anomaly. We find that GRAIL Bouguer gravity models may contain substantial residual signals from large-scale structures due to the Gibbs effect. Therefore, assessment of lunar crustal density structures using high-pass-filtered GRAIL Bouguer gravity anomalies with a specific starting SH degree carries substantial uncertainties. The Gibbs effect can be evaluated in a relatively reliable way by combining full-band gravity anomaly spectra with forward modeling of gravity signals caused by possible density structures. To investigate potential crustal density structures using GRAIL data, we recommend analyzing gravity anomaly spectra in the full range of SH degrees.

Keywords: The Moon, Gravity anomaly, Lunar geodesy, Lunar gravitational field
From Dawn till Dusk: How Light Reduces Martian Granular Slope Angles. The maximum slope of a granular surface—beyond which particles start to move through avalanches—is determined by the balance of gravitational and interparticle forces and is independent of gravity when only frictional forces act between the particles. Additional forces like cohesion can modify (increase) this slope angle, though, and break the degeneracy on gravity. In addition, it has been proposed that a subsurface Knudsen compressor induced by insolation can specifically decrease maximum granular slope angles on Mars. To test the latter hypothesis, we study particle motion on slopes under Martian conditions in parabolic flights. That is, we simulate low gravity (0.37 g), low ambient pressure (100, 300, 600 Pa), and weak sunlight (590, 1235 W m−2) while increasing the slope of the granular media. As simulant we use JSC Mars-1A of two different particle size ranges centered at 50 and 160 μm and a mixture of both. Without illumination, we find avalanches starting on slopes reaching about 35°, not significantly depending on the size fraction. In illuminated parts, avalanching systematically starts at lower slope angles, i.e., as low as about 10°. Here details depend on particle size, light flux, and ambient pressure, as elucidated by a mathematical model that corroborates our experimental findings. At high pressure, we see a tendency that particle motion starts at the light/shadow boundary. In any case, we see for the first time that the low Martian light flux is sufficient to drive significant Knudsen compressors within the Martian soil and reduce slope angles.

Keywords: Planetary surfaces, Solar system planets, Surface processes, Mars, Solar system terrestrial planets
Revealing Callisto's Near-subsurface Thermophysical Properties with ALMA Calibration Data. Thermal images at different wavelengths probe varying subsurface depths of planetary bodies and therefore can inform us about their compositions, thermophysical properties, and impact histories. We identified six archival observations of Callisto obtained by the Atacama Large Millimeter/submillimeter Array (ALMA) between 2012 July 17 and 2012 November 4 at wavelengths of 0.43─0.47 mm (701.9─641.5 GHz). These wavelengths are shorter than those of nearly all other Callisto ALMA data and are sensitive to subsurface emission at depths (the upper ∼centimeter) between those sounded by millimeter and infrared observations. We estimate the disk-averaged brightness temperature as 133 ± 15 K and use a thermophysical mixture model to find that Callisto's thermal emission is best fit by a ∼50%─50% two-component thermal inertia mixture of Γlow∼15─40 J m−2 K−1 s−1/2 and Γhigh∼1200─2000 J m−2 K−1 s−1/2, consistent with recent ALMA observations of Callisto at longer wavelengths. Finally, we present several previously unpublished Galileo Photopolarimeter/Radiometer (PPR) observations of Callisto and derive thermal inertia and spectral emissivity maps using the same model. Altogether, these ALMA and PPR maps improve our understanding of the thermal properties and spatial distribution of Callisto's shallow subsurface regolith and demonstrate the value of ALMA flux density calibrator data for extending frequency coverage of existing science data.

Keywords: Planetary surfaces, Callisto, Surface processes, Natural satellite surfaces, Galilean satellites, Remote sensing, Planetary science, Radio interferometry, Jovian satellites
Surface Modifications of a Space-weathered Ryugu Sample and the Reflectance Spectral Response. Reflectance spectra from the surface of asteroid Ryugu, measured by the Hayabusa2 spacecraft, exhibit a metal-OH absorption at ∼2.7 μm that is approximately half as deep as the returned samples measured in the laboratory and shifted toward longer wavelengths. These spectral differences likely result from the effects of space weathering; however, this interpretation has not been confirmed. In this study, we conducted a detailed observation of the surface of the Ryugu sample A0283, which shows reflectance spectra indicative of space weathering. Electron microscope observations on the A0283 surface identified space-weathering features (e.g., smooth and frothy layers and melt splashes) as previously reported. At these modified surfaces, the 2.7 μm band was approximately 50% shallower than that from unweathered surfaces and the position shifted up to 8 nm longer wavelengths. Additionally, the Reststrahlen band of phyllosilicates at ∼10 μm shifted by up to 0.8 μm from the position of unweathered samples, and its peak broadened. In particular, the regions covered by the frothy layer exhibited significant spectral changes. The frothy layer consists of vesicular amorphous silicate, with a thickness of tens to thousands of nanometers, and exhibits a lower Mg/Fe atomic ratio than the interior. These results indicate that space weathering causes amorphization, dehydration, Mg sputtering of the asteroid surface, and consequently, modification of reflectance spectra of asteroid Ryugu. In contrast, the collected samples are dominated by newly exposed surfaces, resulting in the observed spectral differences between the asteroid surface and its returned samples.

Keywords: Asteroids
Inferring and Interpreting the Visual Geometric Albedo and Phase Function of Earth. Understanding reflectance-related quantities for worlds enables effective comparative planetology and strengthens mission planning and execution. Measurements of these properties for Earth, especially its geometric albedo and phase function, have been difficult to achieve owing to our terrestrial situation—it is challenging to obtain planetary-scale brightness measurements for the world we stand on. Using a curated data set of visual (0.4─0.7 μm) phase-dependent, disk-averaged observations of Earth taken from the ground and spacecraft, alongside a physical─statistical model, this work arrives at a definitive value for the visual geometric albedo of our planet:  0.242−0.004+0.005 . This albedo constraint is up to 30%─40% smaller than earlier, widely quoted values. The physical─statistical model enables retrieval-like inferences to be performed on phase curves and includes contributions from optically thick clouds, optically thin aerosols, Rayleigh scattering, ocean glint, gas absorption, and Lambertian surface reflectance. Detailed application of this inverse model to Earth's phase curve quantifies contributions of these different processes to the phase-dependent brightness of the Pale Blue Dot. Model selection identifies a scenario where aerosol forward scattering results in a false negative for surface habitability detection, which implies that aerosol forward scattering can effectively mimic an ocean glint signature in broadband visual phase curves. Observations of phase curves for Earth at redder-optical or near-infrared wavelengths could disentangle ocean glint effects from aerosol forward scattering. Finally, a review of albedos and planetary photometry is provided, as well as a simple two-parameter fit to Earth's visual phase curve to ease adoption into other tools.

Keywords: Light curves, Photometry, Solar system terrestrial planets, Earth (planet)
Dripping to Destruction: Exploring Salt-driven Viscous Surface Convergence in Europa's Icy Shell. The Europan ice shell is thought to be simultaneously a key contributor and a barrier to the underlying ocean's habitability. Life-supporting oxidants formed by surface radiolysis have the potential to be a significant component toward the long-term sustenance of a Europan biosphere. However, these oxidants must first be transported through the ice shell to its base in order to be accessible by Europa's ocean. We propose that a viscous lithospheric foundering process ("dripping") driven by densification and weakening in salt-rich surface ice may provide a pathway for these surface oxidants to reach the ocean. We find that a viscous dripping process is capable of cycling surface ice to the base of the shell, transporting it in 3 Myr or less, depending on the level of salt-driven lithospheric weakening. Lithospheric drips can accommodate tens of kilometers of surface convergence within the salt-enriched region of the shell. We discover that the surrounding salt-poor ice locks the boundaries of the dripping region in place, encouraging lithospheric thinning and extension. We conclude that this dripping process is a viable avenue toward providing the mechanism for surface ice transport that could support Europan ocean habitability, but more work is needed to fully understand how the presence of saline ice affects ice shell deformation and dynamic behavior.

Keywords: Ice physics, Tectonics, Europa, Planetary science, Planetary dynamics, Galilean satellites, Habitable planets