Sazuna/UAT_keywords huggingface dataset:
Mass-wasting Features on Galilean Icy Moons: Morphological Analysis and Implications. This study investigates mass-wasting features on the icy Galilean satellites Europa, Ganymede, and Callisto. Through comparative morphological analysis, we identified and classified slides, slumps, and flow-like deposits as mass-wasting categories using Galileo Solid State Imager data. Our findings reveal distinct variations in mobility, run-out length, and deposit characteristics across the three satellites. On Europa low topographic relief limits deposit mobility whereas Ganymede and Callisto exhibit longer run-out lengths, potentially due to compositional differences. We estimated the coefficient of friction (H/L), volume (V), area (A), and thickness (d) of the deposits to quantify and compare the regolith mobility among all three Galilean satellites, along with Mars and Earth (Iceland). These results enhance our understanding of surface processes on icy bodies and highlight regions of interest for the Europa Clipper mission, particularly for high-resolution imaging and radar analysis. This study provides critical insights into Europa's surface dynamics and regolith instability, informing future exploration of the subsurface structure and potential habitability on icy moons.

Keywords: Galilean satellites
Toward Reliable Interpretations of Small-exoplanet Compositions: Comparisons and Considerations of Equations of State and Materials Used in Common Rocky Planet Models. The bulk compositions of small planets (Rp &lt; 2 R⊕) are directly linked to their formation histories, making reliable compositional constraints imperative for testing models of planet formation and evolution. Because exoplanet interiors cannot be directly observed, their makeup must be inferred from mass─radius─composition models that link assumed stellar abundances to the direct observables: planetary mass and radius. There are a variety of such models in the literature, each adopting different equations of state (EOS) to describe the materials' properties at depth and varying assumptions about the minerals present within the planets. These EOS+mineral suites provide the foundations for compositional inferences, but they have not yet been systematically compared. In this work, we review several suites, with a detailed description of the basic structure, mineral physics, and materials within standard small-planet models. We show that EOS+mineral suites predict planet densities whose differences are comparable to current observational uncertainties, which present a challenge for robustly interpreting and classifying small planets. We apply a powerful small-planet characterization framework, which illustrates that variations among EOS+mineral suites lead to inconsistent conclusions for both individual planets and sample-level demographics. Our results demonstrate the need for more careful considerations of the materials and EOS used in mass─radius─composition models, especially given the current focus on finding and characterizing potentially habitable rocky planets. We conclude with recommendations for best practices so that future interpretations of small planets and their formation are accurate and consistent.

Keywords: Extrasolar rocky planets, Exoplanet astronomy, Mineral physics, Planetary interior
Covertly Active Comet (139359) 2001 ME1. On 2018 November 18, coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) captured an unrecognized comet crossing its fields of view. We identified this comet to be the minor planet (139359) 2001 ME1, whose previously unnoticed dust activity near perihelion became optically amplified by efficient forward scattering of sunlight as the comet crossed between the Sun and SOHO/Earth at up to  175.°6  phase angle. Simultaneous backscattering observations by the Solar Terrestrial Relations Observatory (STEREO) precisely constrain the comet's ∼7 mag forward scattering brightening, enabling a direct comparison with the ∼3 mag brightening of the more active but optically dust-poor comet 2P/Encke seen by SOHO and STEREO under similar geometry in 2017. Earlier STEREO observations from 2014 additionally show the newly recognized activity to be recurrent─consistent with a reanalysis of the comet's associated meteor activity—and has likely only been previously overlooked due to the comet's faintness and proximity to the Sun while active. Orbital integrations show the comet has likely followed a near-Earth orbit for at least the past 10 kyr, suggesting that the weakness of its observed activity evolved through its continued depletion of accessible volatiles.

Keywords: Near-Earth objects, Short period comets, Comet dynamics, Comet dust tails, Meteor streams, Comets, Coma dust
A One-dimensional Microphysical Model of the Venus Cloud System between 40 and 80 km Including Photochemistry and Radiative-dynamic Feedback. We present results from 1D simulations using PlanetCARMA for Venus in which, for the first time, a sophisticated 1D cloud microphysics model has simultaneously incorporated simplified diurnally varying photochemistry, parameterized diurnally varying solar heating, interactive radiative cooling, and 1D radiative-dynamical feedback. The model basis is a state-of-the-art bin-resolved microphysics scheme. It also incorporates simplified photochemical production and loss rates for sulfuric acid and water vapors that have been extracted from the predictions by current state-of-the-art photochemical models in the literature. The radiative transfer model is a two-stream delta-scaled scheme. Convective mixing in this model is calculated using a Richardson number parameterization of the eddy diffusion coefficient. We find that the simulated clouds and upper hazes compare favorably with in situ and remote sensing measurements of the clouds. We find a measurable ∼400 day oscillation in the photochemical clouds. This 1D model can serve as a baseline of comparison for future work to explore effects of 3D mesoscale dynamics feedbacks on the Venus cloud structure.

Keywords: Atmospheric clouds, Planetary atmospheres, Venus, Atmospheric composition, Atmospheric variability
Modeling the Effects of Anthropogenic Activities on the Lunar Environment with a Systems-theoretic Approach. An increasing number of missions to the Moon are planned for the future. However, their long-term, cumulative impacts on the lunar environment are unknown. Research indicates that some important scientific discovery potential may be permanently lost, and exploration may become challenging due to effects of large-scale human activities. Motivated by these questions, we develop and present a generalizable systems-theoretic framework, called Sustainability Evaluations for Lunar Environment Exploration, for assessing the effects of human-built systems on the lunar environment. We contribute a scale and rate diagram of natural and anthropogenic processes on the Moon to provide comparative assessment of important processes that can dominate environmental effects and carry implications for human operations. Additionally, we derive metrics using functional-relationship diagrams of engineered systems to identify environmental effects based on exchange of matter, energy, and information. We demonstrate computation of two selected metrics: the area of the blast zone due to lunar landings and the trajectory of disturbed regolith mobilized from the lunar surface. For the cases considered, our results show that modern spacecraft (that may transport humans to the Moon) can have a landing blast zone area that would be 2─5 times larger as compared to the estimated landing blast zone area of the Apollo missions and up to 30 times larger as compared to some robotic missions. Overall, our analyses highlight the urgent need for careful and rigorous consideration of the environmental effects of engineered systems on the Moon and for understanding the important trade-offs that exist in preserving and (potentially irreversibly) altering the lunar environment.

Keywords: Lunar surface, Exosphere, Lunar regolith
Dawn─Dusk Asymmetry of the Io Plasma Torus Derived from Io's Auroral Footprints Observed by Juno-UVS. The Io plasma torus (IPT) is a dense plasma cloud that corotates around Jupiter near Io's orbit. A dawn-to-dusk electric field shifts the IPT dawnward. The shift orientation has been previously measured, but the observing geometries have limited our understanding of the spatial extent of the dawn-to-dusk electric field in the day─night direction. This study probes the dawn-to-dusk electric field using Io's auroral footprints. The position of the Io footprint corresponds to the travel time of the Alfvén waves from Io, which depends on the local plasma mass density along the magnetic flux tube connected to the moon. By modeling the Alfvén wave propagation, we retrieved the ion mass density and temperature at Io's orbit from the footprint positions measured by the Juno Ultraviolet Spectrograph from 2016 to 2022, but the two parameters are degenerate. We found that the flux tube mass content (FTMC)—the total mass integrated along the magnetic field line—is a more robust proxy for variability in the plasma conditions at Io's orbit. The deduced Io-FTMC is correlated with Io's local time (LT) in the magnetosphere. The peak Io-FTMC is found at 03:42 ± 00:53 LT, suggesting the dawn-to-dusk electric field is oriented toward a predusk direction. The estimated dawn-to-dusk electric field is 3.0─20.0 mV m−1, with an upper limit exceeding the previously observed values. This may reflect temporal variations in the solar wind dynamic pressure and in the local plasma conditions driven by Io's volcanic activity over the Juno era.

Keywords: Io, Jupiter, Jovian satellites
Evolution of the Mercurian Crust as Recorded in Carbon. Mercury and other silicate bodies are essential for understanding planetary formation and evolution. The surface of Mercury is unique and enigmatic, yet this innermost planet remains the least explored. The crust exhibits relatively low reflectance, possibly due to the excavation of a buried, primary flotation crust enriched in graphite. The combined spectral ranges of the Mariner 10 vidicon cameras and the MESSENGER Mercury Dual Imaging System (MDIS) characterize a diagnostic reflectance feature of graphitic materials, allowing us to test for their surface presence. We geometrically controlled Mariner 10 images to an MDIS-based control network, achieving subpixel registration between the image sets. With this combined dataset, ratio image mosaics and reflectance measurements comparing ultraviolet (UV) to visible and near-infrared wavelengths are consistent with increased UV reflectance in low-reflectance material, which fades with mixing and maturity. We conclude that space weathering processes mix graphite into the surrounding regolith and may alter it to other carbon phases.

Keywords: Mercury (planet), Planetary surfaces, Ultraviolet spectroscopy, Planetary geology, Regolith
The Surface Mineralogy of the Spinel-rich Asteroids from Mid-infrared Spectroscopy with JWST. The "Barbarian" L-type asteroids are purported to contain a high abundance of calcium─aluminum inclusions (CAIs), the oldest solar system solids, based on the dominance of the mineral spinel in their near-infrared spectra. We observed a sample of five objects of this class at 5─28 μm with the Medium-Resolution Spectrometer mode of the Mid-Infrared Instrument on the James Webb Space Telescope. The spectra indicate high-porosity (85%─97% porosity) particulate regolith (&lt;30 μm particles) made up of Mg-rich crystalline olivine (Fo 80─100), with an additional component that could be spinel or amorphous olivine. The spectra of these objects closely resemble that of the oxidized CV3 chondrite Allende. The asteriod spectra additionally exhibit features at 5.75, 6.2, and 7.55 μm that are not definitively identified but may arise from infall of C-bearing materials. These data complement existing visible to near-infrared data of the same targets, which indicate the presence of spinel and minimal hydroxylation, demonstrating the value of multiwavelength spectroscopy to get a more complete picture of the surface compositions of asteroids. The multiwavelength data consistently demonstrate a strong resemblance between the L-type asteroids and CV3 (or possibly CO3) chondrites. The spectra do not require an enhancement in CAI content above that of CV3 chondrites, but the lack of laboratory data prevents a quantitative constraint on CAI content for now. The dominance of crystalline olivine with a high Mg/Fe ratio, and minimal evidence for hydration suggest either an anhydrous formation in the inner solar system, or formation in the outer solar system followed by high-temperature alteration and dehydration.

Keywords: Asteroids, Infrared spectroscopy, James Webb Space Telescope, Main belt asteroids, Asteroid surfaces
A Mars Microbial Survival Model: Calculating Bioburden Reductions for Past Mars Spacecraft to Estimate Forward Contamination on Mars. Minimizing the forward contamination of Mars from terrestrial microorganisms is a key objective of planetary protection. To model the survivability of terrestrial spacecraft microorganisms under the biocidal effects of space, as well as on the surface of Mars, a Mars Microbial Survival (MMS) model was developed. The MMS model predicted the bioburden reductions at 14 historical Mars landing sites. During cruise phases, the exteriors of spacecraft aeroshells were sterilized owing to solar UVC irradiation, accumulating several Sterility Assurance Levels (SALs; defined as ─12 log reductions from initial starting populations of 106 spores per replicate) even before arriving at Mars. On the surface of Mars, each landed spacecraft would reach one SAL for upward-facing surfaces after only one sol on the surface owing to solar UVC (200─280 nm) irradiation. Over one Mars year, all external surfaces on all landers were likely sterilized by UVC. Contributions from desiccation, low pressure, and biotoxic soils on Mars also produced small additional bioburden reductions. It is unlikely that terrestrial microorganisms will be able to survive on the external surfaces of the landed spacecraft considered in this work. Internally, heated components of the spacecraft may reach one SAL in ∼100 sols, but nonheated internal components might take as long as 25 Mars years to be sterilized.

Keywords: Astrobiology
The Relative Cold-trapping Likelihood of Water on Airless Rocky Bodies. Many planetoids are airless, but despite the lack of a collisional atmosphere, these bodies can experience volatile migration toward the polar regions via the exosphere. However, there is a lack of parametrical studies that focus on cold-trapping as a general planetary process, as opposed to within the context of specific bodies. Therefore, we run a Monte Carlo simulation to determine the water cold-trapping likelihood for planetoids of varying size, bulk density, and insolation. As expected, small planets lose most of their water via thermal escape, while large planets favour photolysis. For a given bulk density and solar irradiation, we find the optimal planetary size where cold-trapping is most likely. Surprisingly, the Moon has the ideal size and instellation parameters to maximally cold-trap water in our model. We also find that the ideal size for cold-trapping changes very little across a wide range of cold-trap area coverage, planetary rotation, and photodissociation rate relative to bolometric flux.

Keywords: Monte Carlo methods, Lunar atmosphere, Surface ices, Exosphere
Dating Young, Low-K Martian Meteorites with an In Situ K─Ar Isochron Technique for Mars Missions. Accurate age determination is fundamental to advancing our understanding of planetary evolution. While sample-return missions provide the most accurate age measurements, in situ methods via one-way missions offer a significantly lower-cost alternative, enabling more frequent mission opportunities. The K─Ar isochron method, which combines spot-by-spot analysis using laser-induced breakdown spectroscopy (LIBS) for K and mass spectrometry (MS) for Ar, shows promise for in situ age dating since LIBS and MS have been used in planetary missions. Previous studies analyzed K-rich terrestrial rocks and chondrites using this LIBS─MS method. Martian meteorites, the only available samples of Martian rocks, are crucial for validating this technique for Mars missions. However, their low K concentrations and young ages have precluded measurements using this method. To overcome these challenges, we updated a LIBS─MS instrument for in situ K─Ar dating and applied it to three Martian meteorites: NWA 817, Zagami, and NWA 1068. We obtained isochron ages of 1351 ± 337 Ma, 165 ± 74 Ma, and 122 ± 163 Ma (2σ), respectively, in agreement with previously reported crystallization ages. The amounts of nonradiogenic 40Ar estimated using the y-intercept on the isochron plot are also consistent with those of previous studies. Our results suggest that this instrument is sufficiently precise to calibrate Martian crater age models and determine the absolute ages of young volcanic activity on Mars in the Amazonian period.

Keywords: Mass spectrometry, Mars, Planetary science, Meteorites, Laser ablation
Formation Age of Ernutet Crater, Ceres, and Implications for Origin of the Organics. Ceres is the largest body in the Main Asteroid Belt and has a unique composition characterized by products of aqueous alteration such as carbonates, ammoniated phyllosilicates, and organic materials in concentrated regions. A large organic region is associated with the 53 km diameter, relatively fresh crater, Ernutet, located in the northern hemisphere of Ceres. The isolated nature of the materials suggested delivery from impact (external source); yet high impact energy makes survivability of these materials unlikely. An internal source has also been suggested, but the localization is difficult to explain; thus, the origin of these organic materials on Ceres is still inconclusive. In this paper, we measure and classify superposed craters on Ernutet and its organic-rich ejecta to derive Ernutet's absolute model formation age and provide new constraints on the origin of the organics. Cumulative crater size─frequency distributions are used along with the asteroid-derived model production function chronology to estimate an age of ∼400─900 Ma. Therefore, Ernutet is likely much older than the surface survivability of delivered organics, on the order of 107 yr, even with regolith mixing. In addition, we find the volume of observed organics is plausibly much larger than could be delivered by the Ernutet impactor. We conclude that the organics are more likely to have originated endogenically rather than exogenically on Ceres.

Keywords: Ceres, Craters, Complex organic molecules, Impact phenomena
Formation and Survival of Complex Organic Molecules in the Jovian Circumplanetary Disk. Europa, Ganymede, and Callisto are key targets in the search for habitability due to the potential presence of subsurface oceans. Detecting complex organic molecules (COMs), essential for prebiotic chemistry, is crucial to assessing their potential. Though COMs remain undetected on these moons, ESA's Jupiter Icy Moons Explorer (JUICE) and NASA's Europa Clipper missions aim to fill this gap with their science payloads. This study explores the formation and transport of COMs within Jupiter's circumplanetary disk (CPD), a critical environment for the formation of the Galilean moons. Using a time-dependent model that couples the evolving CPD structure with the dynamics of icy particles of varying sizes and release times, we assess two primary COM-formation pathways: thermal processing of ices and UV photochemistry. The results indicate that heating, particularly of NH3:CO2 ices, occurs efficiently before substantial irradiation, making it the dominant pathway for COM formation in the Jovian CPD. However, the relative efficiencies of these two processes are governed by particle density, disk viscosity, accretion rate, and UV flux, which collectively determine drift timescales and exposure to favorable thermodynamic environments. Existing models indicate that Europa's accretion was relatively cold and prolonged, possibly allowing some COMs to survive incorporation, whereas Ganymede and Callisto likely formed under even cooler conditions conducive to preserving COM-rich material. These results highlight the potential inheritance of complex organics by the Galilean moons and offer a framework for interpreting upcoming compositional data from JUICE and Europa Clipper.

Keywords: Planet formation, Flyby missions, Galilean satellites, Complex organic molecules
Thermal Stability of Ice at Shackleton Crater: Implications for Water Ice Detection for the Chang'E-7 Mission. The candidate landing region for China's Chang'E-7 (CE-7) lunar exploration mission is near Shackleton crater at the lunar south pole, and the CE-7 mission will perform in situ detection of water ice. We model the thermal stability of water ice in Shackleton crater and its surroundings at higher resolutions than previous remote sensing observations, considering the thermophysical properties of lunar regolith suitable for low-temperature conditions at the south pole. The effects of regolith thermal properties, influenced by different packings of lunar regolith, on the thermal stability of water ice in both permanently shadowed regions (PSRs) and non-PSRs are analyzed. Most of the surface of lunar regolith inside Shackleton crater is favorable for the stable preservation of water ice. For the PSRs inside the crater, more loosely packed lunar regolith results in lower annual mean temperatures at depths shallower than ∼0.03 m below the surface than those for densely packed regolith, suggesting that water ice could be more easily preserved in the shallow layers of loosely packed regolith in PSRs. Cold traps for some volatiles that require lower temperatures than water to persist over geological timescales are also identified; these cold traps, however, are noncontiguous due to the variation in local topography. Outside Shackleton crater, there are numerous cold traps with sizes down to ∼100 m. The identified cold traps could preserve a rich history of volatile accumulation and serve as targets for in situ exploration of water ice during the CE-7 mission.

Keywords: Lunar surface, The Moon, Surface ices
Near-infrared Hapke Photometric Analysis of the Moon's Regolith with Passive Radiometry from the Lunar Orbiter Laser Altimeter (LOLA). Measurements of the Moon's surface reflectance across a broad range of wavelengths and geometries can provide vital clues about the processes acting on its regolith. In the near-infrared (1064 nm), the Lunar Orbiter Laser Altimeter (LOLA) operates as a passive radiometer when its laser is turned off, adding a wavelength to the capabilities of the Lunar Reconnaissance Orbiter for narrowband photometric studies. We analyze LOLA passive radiometry spanning 2013 December through 2024 April, using the Hapke photometric model to infer regolith properties. We find that the highlands have a more backscattering single-particle phase function than the maria, with optically immature highlands exhibiting the strongest backscattering. In the maria, scattering becomes more symmetrical between backward and forward scattering with increasing TiO2 abundance, which may be related to the reflectance peak of ilmenite near 1 μm. Looking in detail at the Reiner Gamma swirl, we find that the contrasts in on/off-swirl photometric behavior can be explained by differences primarily in single-scattering albedo, and to a lesser extent the single-particle phase function, without any difference in surface roughness or porosity. The stronger influence of single-particle properties relative to surface textural properties is consistent with the solar wind standoff and electrostatic dust transport hypotheses for swirl formation, but not with the cometary impact hypothesis.

Keywords: Remote sensing, The Moon, Narrow band photometry